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Exploration Drilling First edition 2010 www.atlascopco.com

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Exploration Drilling

First edition 2010www.atlascopco.com

At Atlas Copco, our focus on customer productivity requires a steadfast commitment to continuous improvement — and finding solutions.

It may be a design innovation to our surface and underground drill rigs, in-hole tools or diamond products. More efficient distribution may be made possible through new ways of thinking. Or a customer’s productivity will be enhanced through customized on-site service and training.

Because we listen, we understand. Because we are more engaged, we will always find a better way.

There is always a better way

exploration drilling 1

Foreword

2 Foreword by Daniel Misiano Marketing Manager Exploration Atlas Copco Geotechnical Drilling and Exploration

Talking technically

3 Trends in exploration 8 Geology for exploration and mining 14 Prospecting and exploration for minerals 20 In search of the right balance 24 An introduction to Reverse Circulation drilling 30 Reverse circulation drilling with new hammer concept 32 Four decades of Diamec core drilling rigs 36 Selecting the right coring bit 40 Efficient core recovery 44 Hydraulic and mechanical surface drill rigs 48 Keep the rig and business running

Case studies

50 Confirming the future of Zambian copper 52 Atlas Copco exploration rigs prove reserves 54 Excore optimizes performance for Drillcorp 58 New record depth for CS14 core drilling rig 62 Grade Control at Kemi Mine 66 Reverse circulation drilling in Australia 68 Diamec MCR in Australia 70 Reverse circulation technology wins in Brazil 72 Thin wall core barrels improve productivity 74 Groundbreaking technology in the Valley of Gold 76 Christensen CS3001 works well in extreme conditions

Product specifications 78 Diamec core drilling rigs 83 Christensen core drilling rigs 88 Explorac reverse circulation rigs 90 Excore core drilling tools 92 In-The-Hole tools 94 Reverce circulation tools

For latest updates contact your local Atlas Copco Customer Center or refer to www.atlascopco.com

Contents

Front cover: Core sampling with Atlas Copco equipment. Northern College of Applied Arts and Technology, Kirkland Lake, Ontario Canada. Photographer: James Hodgins.

2 exploration drilling

ForewordSatisfying future production demandsThe mineral exploration community has, in recent decades, suffered its fair share of cyclical times. However, the latest cycle is unprecedented in the large swing from the successive boom years of 2005-2008 to the sharp decline in late 2008 caused by the global financial crisis. The last three cycles have one distinct common factor, which is the ongoing increase in demand for mineral resources as a result of global population growth and the emergence of less-developed countries. Even in the current economical turmoil, most will agree that the mid- to long-term outlook favours continued increased demand for mineral commodities, and pressure on exploration drilling programmes.

Technological advances in all aspect of mineral exploration have ensured evolutionary and revolutionary improvements in drilling techniques, and Atlas Copco has continued to offer innovation and leadership in the supply of mineral exploration products. Our global presence has facilitated the introduction of new products such as computerized drilling rigs, high perform-ance diamond tools, and improved in-the-hole equipment, which have been developed for both core and reverse circulation explo-ration applications. All of our products embody the safety and environmental features that are an integral part of Atlas Copco’s continued commitment to our clients and the industry.

The search for new mineral resources is in ever more remote areas of the globe, where infrastructure is often absent and the cultural acceptance towards mining may not yet be fully under-stood. In these environments, it can be difficult to attract and recruit skilled labour. It is therefore necessary to provide the exploration drilling companies with top quality products that will ensure increased productivity, optimized efficiency, and

reduced downtime. Apart from the obvious advantages, such products are also a major factor in improved labour retention.

When designing, manufacturing, selling and servicing Atlas Copco equipment, we strive to achieve optimal productivity, minimal downtime, best safety, environmental friendliness and high return on investment for the customer. These important objectives are achieved by a collaboration of customer input and Atlas Copco’s ability to bring to market such products and services. We must never underestimate the value of our clients’ input, and its role in creating a lasting and trusting business relationship. Each of our products needs to reflect the client’s signature, something which Atlas Copco is proud to achieve.

The ambition in offering this reference book is to further encou- rage interaction between all respective parties, technical and commercial, who have a special interest in mineral exploration applications. The participants include the global exploration community of drilling services, governmental agencies, con-sultants, geological associations and companies, educational institutions and, of course, our own sales, marketing and tech-nical organization.

The cases described in this manual are chosen for the variety of geological, geotechnical and environmental conditions experi-enced in different parts of the world. We sincerely hope that the articles will lead to continued interaction between the diverse parties that form our exploration community. It is our objective to be an integral part of the continued challenge to be more competitive and profitable.

Yours sincerely

Daniel Misiano

Marketing Manager ExplorationAtlas Copco Geotechnical Drilling and Exploration

[email protected]

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Talking TeChniCally

exploration cycle

Mineral exploration is, by definition, the process of finding ore to mine. Ore is commercially viable concentrations of minerals. Usually undertaken by mining companies, partnerships or corporations, mineral exploration is a more intensive, organized and professional form of mineral prospecting. Despite frequently using prospecting services, the process of mineral exploration is a much more involved operation.

The exploration cycle includes a num- ber of steps and activities such as area selection, target generation, geophysical methods, remote sensing, geochemical methods, resource evaluation, reserve definition and extraction.

Resource evaluation usually involves core or reverse circulation drilling, by which time a lot of money has already been invested into the exploration pro-ject. These first drill holes are needed to verify the findings from the initial investigation, and all obtained cores or samples are saved as tangible proof of what has been found.

exploration spending

Exploration expenditure is mainly driven by metal prices and, in the long run, by metals demand. When metals demand peaks, so does exploration expenditure. Explorac 220RC – reverse circulation rig operating in Australia.

Trends in explorationnecessity of mineral explorationproduction, survival and expan-sion. These activities are under-taken on a more or less continuous basis by the internal organization of individual companies, by con-tractors, or by funding junior com-panies. Exploration is carried out close to existing mine sites in or- der to identify and investigate ex- tensions, and in new areas to find and delineate fresh deposits. Historically, spending on explo-ration is cyclical, and tends to follow metal and mineral prices and the general business trend.

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Studying non-ferrous exploration bud-gets over a 20-year period (see fig. 1), we can see that, after a flat period in the beginning of the 1990s, there was an increase in spending for six consecutive years, reaching a peak in 1997. But in 2002, after a steady five years, spending fell back to the 1989 level.

Since then, exploration budgets in- creased dramatically every year, reach-ing an all-time high in 2008.

Then the world economic downturn in late 2008 drastically reduced the le- vel of activity, and spending in 2009 dropped off accordingly. This shows

clearly just how highly cyclical the exploration drilling business is.

The historical budget figures have not been adjusted for inflation, which means that the actual growth is not as large as indicated. This means that the actual activity on the ground has not increased in direct proportion to the expenditure, despite continuously in-creasing exploration costs.

increasing difficulties

Some cost increases were due to lack of staff and equipment during the mining

boom. Also, new deposits are found in more remote and challenging regions located further away from final mar-kets, high up in the mountain ranges of Latin America or out in the Asian deserts. In addition, ore grades are con-tinuously declining, making discover-ies more difficult than when ore bodies outcropped or were at shallow depths.At the same time, increased demand made it necessary to increase the rate of discovery of new deposits, otherwise total ore reserves to relative total metal production would decrease.

With hindsight, it is apparent that exploration should have been increased at a higher pace than that achieved. As a result, the current decline, driven by falling metal prices, has been more dra- matic than the trough in 2001/2002. This brings about the likelihood of another price peak in a few years time, driven by a perceived reduction in reserves.

increase in all regions

During the five years to 2008, explora-tion increased in all regions, and the relative geographical distribution re- mained basically the same, see fig. 2.

North America as a region is still number one, closely followed by Latin America, which for a long time has been a popular exploration region. Canada keeps its top position as the most popu- lar country, followed by Australia. Year- on-year growth in each region varied considerably. Forinstance, Papua New Guinea, the Philippines and Indonesia planned for a 60 % increase in explo-ration in 2008 compared with 2007.

Also worth noting is the fact that ex- ploration expenditure in Africa is con- siderably higher than the region’s share of mine production, indicating that its future role in metal and minerals pro-duction will grow. Democratic Republic of Congo, Angola, Tanzania, Botswana and Ghana are countries with high ex-ploration activities.

Meantime, China and Mongolia are the most important countries in Asia.

active players

The global mining industry is made up of some 6 000 companies. The vast majo-rity are the 4-5 000 junior exploration

Figure 3: Worldwide exploration budgets by compant type, 1999-2008(as a percentage of worldwide exploration)

Figure 1: estimated total worldwide exploration budgets (excl. uranium), 1989-2008 (US$)

Figure 4: Worldwide non-ferrous exploration budgets by target, 2008

Figure 2: Worldwide non-ferrous explora-tion budgets by region, 2008

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companies that do not have a mine in operation, but hope to find new de-posits to exploit. These companies do not have any cash flow, but depend on funding from the stock exchanges or from private placements for risk capital. They are small, innovative, and often with highly trained staff. They have been willing to take risk and are fast to make decisions, and dare to go into new areas and to apply geological models in new ground. In recent years, the juniors have accounted for a growing propor-tion of exploration expenditure, but in 2008 there was a slower growth for the juniors and an increased spending from the major companies. Many of the tra-ditional mining companies have earlier downscaled their internal exploration departments and spread their risk by funding juniors, see fig. 3. In the Nordic countries, for example, juniors accounted for some 50% of exploration, and this figure is similar for companies based in Canada, Australia and the UK.

greenfields vs brownfields

During the last five years the share of the grassroots exploration has decrea-sed, and Late Stage and Minesite have taken over that share. The spending in Late Stage has become larger than in grassroots exploration. The junior com-panies have accounted for more than half of the grassroots exploration, and major companies for about 80 % of the minesite exploration during the same period.

The increase in the brownfields sec-tor indicates the efforts to both replace and increase the ore reserves in existing mining areas.

With less total spending on explora-tion after the beginning of the financial crisis in late 2008, it can be expected that the share of the grassroots explora-tion will continue to decrease.

On the other hand, there is a demand for new large mineral deposits, and they have most probably to be found in new sites in remote areas. This should result in increasing greenfield exploration.

Type of metals

2008 was the first year since 1989 when exploration budgets for base metals such Christensen CS4002 surface core drilling rig operating in Mexico.

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as copper, nickel and zinc were higher than for gold, See fig. 4. Gold has, prior to 2008, always attracted more capital than other metals, but for five conse-cutive years the percentage spend for gold has declined. However, looking for gold has always been exciting, and will continue to be so.

Diamonds are the third most impor-tant mineral after gold and copper but, like gold, declined for five years.

looking forward

The world economy is a major influ-ence on the exploration business, with metal prices and availability of mine-rals as the main driver.

After the chaos in the world econo-my in late 2008, it was natural that the level of exploration activity should signi- ficantly reduce. Because credit is now less-freely available, it can be expected

that less capital will be available for new exploration projects. However, mineral exploration is an optimistic business, and new projects will emerge as the long-term demand for metals increases.

In 2009 we are observing a steep de- cline in the exploration business in line with that of the global economy. The question is how deep will the curve dip? Will it be down to the 2002 level, or will it level out before that point?

It is possible that the mining com-panies have learned from the previous downturn in 2002, when it took a long time to restart exploration activities after deep cuts in spending and resour-ces. Nowadays, many companies have integrated exploration into their long-term business strategy, and carry on planning their exploration activities over the business cycle. They may well stick to their original plans, and pick up the activity level after the initial cuts.

There is a question mark hanging over whether the trends will swing more with higher peaks and lower bottoms, or just swing faster. There are many theories about how the global economy will develop, and how exploration de-mand will contribute to its revival.

The cost of exploration has increa-sed, and in order to find future volumes and qualities of minerals, exploration has to be in remote areas and, in some cases, high-risk areas with higher costs.

Some of these cost increases can be compensated by use of new methods, and by investment in new and more efficient exploration equipment. For example, core drilling rigs have been developed to operate in deeper holes, demanding less personnel and support, contributing to higher productivity.

All mining companies have to en-sure proven ore reserves for long-term growth, for which core in the boxes, showing grade and quantity, is essen-tial as the proof. That is their future capital.

anders gustafsson

Atlas Copco is very grateful to Metal Economics Group for the right to pub-lish their graphs and definitions.

Definitions (courtesy Meg)

Junior companies Category mainly includes pure explorers, but also aspiring producers. Principal means of funding exploration is through equity financing.

Major companiesCompanies with annual non-ferrous mining-related revenue of more than US$500 million, and the financial strength to develop a major mine.

grassroots explorationFrom the earliest stage through to perimeter drilling, prior to quantification of initial re-source. Includes reconnaissance and evaluative forays.

MinesiteAll exploration at or around an existing mine site held by the company, including searching for satellite orebodies within economic transport distance.

late stageExploration to further define, quantify, and upgrade a previously identified orebody, including feasibility work up to a positive production decision.

intermediateIn the first hand based on a company's adjusted annual revenue with at least $50 million in annual non-ferrous revenue and less than $500 million major-company threshold.

Diamec U8 APC core drilling rig in operation.

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Core drilling operation in Mexico.

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The earth

The earth consists of an inner and outer core surrounded by a mantle. At the surface is a thin layer of rocks known as the crust. This shell-like structure has been confirmed by studying seismic waves originating from earthquakes. The velocity, or propagation, of these waves is related to the density of the material and its state, be it solid or liquid. According to this interpretation, the inner core is solid and the outer core is liquid. The mantle and the thin crust of the earth are solid.

The thickness of the core and mantle together corresponds roughly to half the radius of the earth. We can observe only the upper part of the earth’s crust. The deepest drill hole is 11 km, but we can get information from the equivalent of some tens of km by studying eroded mountain chains.

The earth was formed more than 4.6 billion years ago by aggregation of

cosmic material from our solar system. The meteorites falling down on earth are of same origin as our planet so, by studying this material, we can get data about the chemical composition of the deeper part of the earth. There are two types of meteorites: stone meteor-ites dominated by Fe-Mg-silicates, or chondrites; and iron meteorites mainly consisting of metallic iron and nickel. Seismic and meteorite data indicate that the chemical composition of the core is similar to iron meteorites and that of the mantle is similar to stone meteorites. The difference in density also explains the velocity of the seismic waves in core and mantle, and the high average density of the earth, which is about 5.5 g/cm3.

The thickness of the crust is nor-mally between 10 and 35 km. However, there is a great difference in thickness between oceanic crust and continental crust. Under a mountain chain the crust thickness can be up to 70 km. The chemical composition of the outer part

of the crust is well known, and is domi- nated by seven elements: silica, alumi-nium, iron, magnesium, calcium, sodium and potassium. The continental crust is higher in silica, aluminium and alkali due to the high content of granitic rocks. The oceanic crust is lower in silica but higher in magnesium and iron due to the dominance of volcanic rocks, mainly basalts.

Minerals

A mineral is a natural chemical com-pound with a defined crystal structure and composition. A rock, on the other hand, is a naturally formed aggregate of minerals. There are thousands of different minerals but only about fifty rock-forming ones, most of which are silicates, always containing silica and oxygen. Feldspars account for almost 50% of the earth’s crust and are hence the most common mineral. They can be grouped in potassium feldspar and plagioclase (sodium-calcium-feldspar).

Volcanic rocks sculptured by wind erosion, southern Bolivia.

geology for exploration and mining importance of geologyA thorough understanding of the geology of a mineral deposit is fundamental to its successful exploitation. As such, geology is a vital factor in the process of selecting methods in exploration and mining. The theory of plate tectonics has improved our know-ledge of ore formation, and also helps the explorer to select areas of high mineral potential. Plate tectonics gives us a better under-standing of important geological processes like mountain building, volcanism and earthquakes, and how these processes are connec-ted. The use of geological models makes exploration and mining more effective. This chapter reviews basic aspects of geology that may affect decisions about exploration and mining. Atlas Copco offers a full range of drilling products for site investigation, and for mine deve-lopment and production.

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Other main rock-forming silicates are pyroxene, amphibole, quartz and mica. In addition there are at least three other types of minerals: sulphides, oxides and carbonates.

To identify a mineral in the field, one or more of the following physical pro-perties of minerals are considered: hard-ness, density, streak, lustre, cleavage and crystalline form. Mineral hard-ness is commonly graded according to Moh’s scale, based on ten minerals of increasing hardness. The hardness scale starts with talc as the softest mineral, and ends with diamond as the hardest of all known minerals. The density of many rock-forming minerals is between 2.6 and 3.2 g/cm3. Most ore minerals have a density of 4 or higher. Some ele-ments have much higher densities, gold for example 19.3 g/cm3.

Other diagnostic features are streak, cleavage and crystal type. Streak is the colour of mineral powder produced when a mineral is scratched, whereas cleavage describes the property of a crystal to split along certain crystallo-graphic surfaces. All minerals belong to one of seven crystal systems. For example galena (PbS) sometimes forms small cubes, which is typical for cubic minerals. Mica has a layered structure, which causes cleavage parallel to these layers.

Plate tectonics

The modern theory of plate tectonics has improved the understanding of basic geological processes like moun-tain building, volcanism, earthquakes and formation of many types of ores. According to this theory, the crust and upper part of the mantle can be divided into 10-12 major plates, which move in a complex pattern.

The driving force of this movement can be attributed to heat generated by radioactive decay within the mantle and core. The heat is transported by slow convection streams, which move the plates. The speed of the motion of plates is just a few centimetres per year. Three major plates are North American which includes North America, Mexico and Greenland, South American which includes the whole of South America and a part of the Atlantic, and the

African plate consisting of the African continent and parts of the Atlantic and Indian Oceans. These plates are shown in fig.1.

Plates can interact by moving apart (divergence) or towards each other (convergence). Three types of plate margins will be discussed briefly.

When two continental plates collide, mountain ranges may be formed. Thus the collision of the Indo-Australian and Eurasian plates resulted in the for-mation of the Himalayas, the highest mountain chain on earth. When an oceanic plate moves towards a conti-nental plate such as South America the oceanic plate will move below the con-tinent, or subduct. When the oceanic plate starts to melt, volcanic activity will occur. Therefore, we find a great number of volcanoes along the western part of South America. Subduction also leads to the formation of ores.

In the middle of the Atlantic there is a long chain of volcanoes called the

mid-Atlantic ridge. Similar ridges are found in the other oceans. Along these ridges two oceanic plates are moving apart, leading to partial melting of the mantle below. This causes repeated eruptions of basaltic lava, forming a new ocean floor. The youngest volcanic rocks are found close to the ocean ridge, and the age of the rocks increases out from the spreading centre. The mechanism of seafloor spreading is an important part of the plate tectonic theory.

Volcanic activity occurs at diverging, or spreading, ocean plates and also as a result of a collision between ocean plates and continental plates. Volcanism is normally accompanied by earth-quakes, which may be extra strong when two plates are sheared or sliding along each other. The earthquakes in Los Angeles are of this type.

A collision between the Nazca and South American plate is shown in the fig. 2 on the following page.At a certain depth the subducted Nazca plate will

CARIBBEANPLATE ARABIAN

PLATE

AFRICANPLATE

SOUTH AMERICANPLATE

AUSTRALIANPLATE

INDIANPLATE

SCOTIA PLATE

EURASIANPLATE

NAZCAPLATE

NORTH AMERICANPLATE

Fig 1: Some of the major plates of the world.

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start to melt. The magma intrudes into the overlying rocks and also causes volcanic activity. Most porphyry copper depo- sits are formed in this geological en- vironment. This is the main reason for the frequent deposits of this type along the Andean mountain range. One third of the world’s copper production comes from Chile as a result.

Porphyry copper deposits are always associated with quartzdioritic or grano-dioritic intrusive rocks with a porphyry texture. The copper mineralization is not only found in the intrusive, but also in the surrounding rocks. The main copper minerals of porphyry copper deposits are chalcopyrite and bornite. The content of copper in this type of deposit is usually low, about 0.5%, but porphyry copper often contains some gold and molybdenum. Due to the large size of these deposits they are mainly mined in cost effective open pits, and form the greater part of the world’s copper production.

The discovery of black smokers found at the bottom of the ocean close to a spreading centre was a big sensation. Black and hot at about 350 degrees C, hydrothermal solutions rich in sul-phides are injected into the water from chimney-like structures. When the hot

sulphide solution comes into con-tact with seawater, the sulphides are immediately precipitated. The sulphide minerals formed in this way are mainly of pyrite, pyrrhotite, chalcopyrite and sphalerite. Similar deposits of old age have been mined on Cyprus for thou-sands of years. Black smokers can be called a modern analogue for the fre-quent volcanic massive sulphide (VMS) deposits mined all over the world. The first commercial attempts to exploit black smokers are underway in the deep waters north of Papua New Guinea.

Another interesting type of mine-ralization related to plate tectonics is the occurrence of manganese nodules on the ocean floor. These nodules of varying size are formed close to active spreading centres, where hot metal-rich water emerges. The nodules formed are rich in manganese and iron and have low concentrations of copper and nickel. The quantity of these nodules is huge but the potential cost of exploitation is, at least for the time being, too high.

Magmatic rocks

Magmatic, or igneous, rocks are formed by the cooling and crystallization of magma. This is normally taking place

at great depths in the earth, where pressure and temperature are high. If the intrusion of magma occurs deep in the crust, cooling and crystallization is a slow process. This will favour a coarse-grained texture, which is typi-cal for intruded magmatic rocks. Some magma will reach the surface, where it loses most of its gas content turning into lava, which forms volcanic rocks. At that stage, the crystallization is much faster and results in a fine-grained or glassy volcanic rock.

The shape of volcanoes often reveals the chemical composition of the erupted lava. Basic lava, or basalt, often has a low viscosity, forming shield volcanoes or more or less horizontal lava fields. When the content of silica increases in the magma, it also gets richer in water. Such a combination leads to more explosive eruptions, and the formation of strato volcanoes with cone shaped profiles.

This type of volcano is composed of alternating beds of lava and pyroclastic material, and the chemical composi-tion is intermediate or acidic. Table 1 shows volcanic rocks have a magmatic (plutonic) counterpart. The volcanic basalt corresponds to gabbro, andesite to diorite, dacite to quartz diorite, and

Porphyry copper

Mn nodules with Cu, Ni, Co

Ocean

Continent

400200

60

30

0

km

Fig 2: Andean type ocean - continent collision.

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rhyolite to granite. When a magmatic rock contains large crystals in fine-grained groundmass it is known as porphyry.

When the magma is rich in silica, a light coloured rock is formed. It has a high content of silica and feldspar, and is known as felsic. On the other hand, if the magma is poor in silica but rich in magnesium and iron mine-rals like olivine and different kinds of pyroxenes, amphiboles will dominate causing a dark colour of the rock. This type of basic rock is called mafic. If the content of SiO2 is lower than 45% we get ultramafic rocks like komatiites and peridotites. This kind of rock is often associated with nickel mineralization, see table 1.

Sedimentary rocks

Sedimentary rocks are formed by deposition of eroded fragmented rocks or precipitation of dissolved material. Sedimentary rocks are quite common, covering about 75% of the surface of the earth. However, the volume of sedi-mentary rocks is low, indicating limited thickness of these rocks.

Sedimentary rocks can be divided into two types, clastic and chemical, as shown in the table to the right. Clastic sediments consist of fragments of eroded rocks. Thus, the original rock will partially determine characteristics of the sedimentary rock. Large rounded rock fragments in a finer matrix of fragments are called conglomerate. If the rock is dominated by grains of sand, it is called sandstone. A greywacke is a kind of sandstone with a matrix of fragments, sand and clay.

Limestone is the most common of the carbonate rocks. It is either formed by chemical precipitation of calcite, or from depositions of skeletons of dead organisms such as corals and molluscs. Chert is a chemical sediment consisting mainly of quartz. Evaporites like gyp-sum and halite are formed in bays and lakes of arid regions. Bedding, or laye-ring, is a characteristic feature of many sedimentary rocks. The layering may be due to a variation in grain size or in chemical composition. Initially, the layers are more or less horizontal, but later tectonic forces may fold or overturn

the layers. Sedimentary rocks make up a very heterogeneous family with varying characteristics as shown in table 2.

Metamorphic rocks

When magmatic or sedimentary rocks are subjected to high temperature and pressure they will re-crystallize, often

forming new minerals. A metamorphic rock is formed. The change in mineral composition means that the new mine- rals are stable at the higher temperature and pressure. This occurs without mel- ting of the original rocks, and little change in the chemical composition. Metamor- phic rocks are also characterized by new texture and structure.The reason

A typical sandstone.

Table 2: Some sedimentary rocks

Type of sediment Rock type Composition/Original material

Clastic sediments Conglomerate Gravel, stones and boulders

Sandstone Grains of quartz and small fragments of rocks

Greywacke Like a sandstone but with higher content of rock fragments and argillaceous material

Shale Fine-grained argillaceous material

Chemicalsediments

Limestone Precipitated calcium carbonate

Chert Precipitation of fine-grained quartz

Gypsum, halite Evaporation of sea water

Table 1: Main magmatic rocks

Silica content Plutonic rocks Dykes and silts Volcanic rocks

Basic <52% SiO2

Gabbro Diabase Basalt

Intermediate 52-65% SiO2

Diorite Porphyrite Andesite

Syenite Syenite porphyry Trachyte

Acidic >65%SiO2

Quartz diorite Quartz porphyrite Dacite

Granodiorite Granodiorite porphyry Rhyodacite

Granite Quartz porphyry Rhyolite

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for a change in temperature and pres- sure may be due to heat from intru-ding magma, or because the rocks or sediments have sunk deeper into the earth’s crust. Compression and tension in the earth’s crust also play an impor-tant role during the metamorphic stage.

Metamorphic rocks make up a large part of the earth’s crust. They are divi-ded into three groups, depending on the degree of metamorphism: low, medium

and high. In the first group there are only slight changes in mineral compo-sition. Typical low-grade minerals are chlorite, albite and epidot. At medium and high metamorphism many new mi- nerals are formed, for example, silli- manite and garnet. Due to the strong re-crystallization, all primary textures are destroyed, and in many cases it is very difficult to determine the primary rock. Metamorphic processes often

make the rock denser and harder and more difficult to drill. Foliation is a kind of layering which is a characteristic feature of many metamorphic rocks. When rocks re-crystallize under pres-sure from one direction, platy minerals like mica are orientated in layers per-pendicular to the source of pressure. This results in banded or foliated rocks. Another type of metamorphic structure is lineation, where elongated crystals in the rock are oriented in the same direc-tion, resulting in a cigar-like structure.

Very often, the metamorphic rocks are named after the parent rock. Meta-morphosed sedimentary rocks are called metasediments and volcanic rocks metavolcanites.

Some examples of metamorphic rocks are given in table 3.

Quartzite is a very hard rock formed by the metamorphism of pure sand-stone. Schist is a common metamorphic rock of medium to high grade. This rock is often named after the most common mineral, for example: mica schist; and chlorite schist. Marble is a well-known metamorphic rock formed from re-crystallized limestone.

Rock cycle

There is a relationship between mag-matic, sedimentary and metamorphic rocks, which is shown in the fig. 3. Starting with the magma at the top of the figure and going down to the left, the magma will crystallize into a magmatic rock due to decreasing temperature and pressure. If crystallization occurs within the crust, an intrusive rock results, for example, granite. If the magma is erupted by volcanic activity, the result will be rhyolitic lava, or a tuff of similar composition.

A rock formed at high temperature and pressure is not stable at the surface of the earth. When magmatic rocks are exposed to surface conditions, rocks are eroded and weathered by mecha-nical and chemical processes.Chemical weathering will decompose many minerals, but the remaining part of more resistant minerals and rock frag-ments will be transported by water, ice or wind until deposition occurs. After sedimentation, compaction and cementation of the mineral grains, a

SEDIMENTS

Smelting

MAGMA

Cryst

alliza

tion

Cementation

Met

amor

phis

m

Weathering

Erosion transp.

MA

GM

ATI

C

RO

CK

S

SEDIMENTA

RY

ROCKS

M

ETAM

OR

PH

IC

RO

CK

S

Fig 3: Rock cycle.

Table 3: Typical metamorphic rocks

Rock type Original rock Degree of metamorphism

Amphibolite Basalt, diabase, gabbro High

Mica schist Mudstone, greywacke, etc Medium to high

Gneiss Various igneous rocks High

Green-schist Basalt, diabase, gabbro Low

Quartzite Sandstone Medium to high

Leptite Dacite Medium

Slate Shale Low

Marble Limestone Medium

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sedimentary rock is formed. If the sedimentary rock is buried deeper and deeper under other rocks and sedi-ments, the increasing pressure and tem-perature will cause re-crystallization, often combined with the formation of new minerals. A metamorphic rock is formed. At great depth in the crust the metamorphic rock will start to melt and form a new magma, and the cycle is completed.

However, there are also some other possibilities. When metamorphic rocks are exposed at the earth’s surface, wea- thering starts and the cycle is short-circuited. Erosion and weathering will transform the rock into sediment, which later can form a sedimentary rock. There is also a possibility that a magmatic rock is metamorphosed without for-ming a sedimentary rock in between. In other words recycling of rocks is always going on.

Formation and classification of oresOre is a natural concentration of one or more heavy metals which can be mined with profit. Such a concentration in the earth’s crust is very rare. The reason is that most metals have to be concen-trated many thousands of times to form an ore. A mine also needs a minimum size, a good location, and a qualified staff. Furthermore, the ore should be possible to mine and concentrate to become an economical success.

Ores can be formed by the same processes as rocks. This means that magmatic (igneous), sedimentary and metamorphic processes play important roles in formation of mineral deposits. Hydrothermal activity is another im- portant process, often related to mag-matic activity, in ore formation. Hot circulating water leaches metals from passing throw rocks, and these metals are later precipitated due to cooling, pressure decrease, or a chemical reac- tion with another fluid. Some major ore types are summarized in the table 5.

Tom ekströmContributors; Hans Fernberg

and Magnus Ericsson

Table 5: Some major ore types

Processes Type of ore/mineralisation Metals

Magmatic

Sulphide immiscibility Nickel and copper deposit. Ex. Sudbury, Canada Ni, Cu

Crystal fractionation Monomineralic chromite layers. Ex. Bushveld Complex, South Africa

Cr

Silicate-sulphide immiscibility

Komatiite-hosted Ni-Cu deposits. Ex. Kalgoorlie, Australia

Ni,Cu

Magmatic-hydrothermal

Copper porphyry deposits, associated with granodioritic intrusions. Ex. La Escondida, Chile

Cu, Au, Mo

hydrothermal

Fluid mixing Iron oxide-copper-gold deposits, associated with felsic volcanic rocks. Ex. Olympic Dam, Australia

Au, Ag

Hydrothermal solutions

Epithermal quartz-gold veins, Lode deposits in tectonically deformed zones.

Au, Ag

Exhalative venting “black smokers”

Volcanogenic massive sulphides (VMS). Ex. Trodoos deposits, Cyprus

Cu, Zn

Sedimentary exhalative

SEDEX deposits in sedimentary rocks. Ex. Red Dog Zn-Pb-Ag deposit, Alaska

Zn, Pb, Ag

Sedimentary

Sedimentation of heavy minerals

Placer deposits. Gold in conglomerate Au

Chemical sedimentation Ironstones and banded iron formations (BIF). Ex. Mount Whaleback, Australia

Fe

Table 4: important ore minerals and their composition

Metal Ore mineral Mineral formula

Cobalt Cobaltite, (Co,Fe)AsS

Chromium Chromite, FeCr2O4

Copper Chalcopyrite CuFeS2

Copper Chalcocite Cu2S

Copper Bornite Cu5FeS4

Gold Native gold Au

Iron Hematite Fe2O3

Iron Magnetite Fe3O4

Lead Galena PbS

Molybdenum Molybdenite MoS2

Nickel Pentlandite (Fe,Ni)9S8

Silver Native silver Ag

Tin Cassiterite SnO2

Titanium Ilmenite FeTiO3

Tungsten Wolframite (Fe,Mn)WO4

Tungsten Scheelite CaWO4

Zinc Sphalerite (Zn,Fe)S

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Prospecting

Prospecting involves searching a di-strict for mineral deposits with the view to mine it at a profit. In other words to transform the mineral deposit into an orebody. Exploration, while it sounds similar to prospecting, is the term used for systematic examination of a deposit. After an interesting area is chosen, an application for exploration permit is made. Approval by officials is needed before exploration activities can com-mence. It is not easy to define the point where prospecting turns into explo-ration.

A geologist prospecting a district is looking for surface exposure of minerals, by observing irregularities in colour, shape or rock composition. His experi-ence tells him where to look, to have the greatest chances of success. Sometimes he will stumble across ancient, shallow

Gold panning in the wind.

Prospecting and exploration for minerals in search for orebodiesFor a geologist in the mining busi-ness, exploiting an existing ore-body is the easy part of the job. The hardest part is to find new ore deposits and to define their extent and metal content (grade). But how do you find these accu-mulations of metallic minerals in the earth's crust? The mining com- pany has to ensure that the de-posit is economically viable and needs a guarantee of ore produc-tion over a sufficiently long period of time, before the heavy invest-ments required to set up a mining operation will be considered. Even after production starts, it is neces-sary to locate and delineate any extensions to the mineralization, and to look for new prospects that may replace the reserves being mined. Investigating extensions, and searching for new deposits, are vital activities for the mining company.

Area selection and review of existing data

Application for permit

Air borne survey

Geochemical survey

Geopysical survey on surface

Time

Trenching

Drilling

Environmental impact study

Application for mining permit

Act

ivity

Feasibility study

Table 1: Exploration activity sequence in general

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mine workings, which might have been what led him to prospect that particular area in the first place. Gravity methods such as panning is used for gold pro-specting in alluvial river beds. In areas with limited access to water wind pan-ning can be done towards the wind direction.

exploration activities

The first step is to conduct a review of historical and existing data, See table 1, Especially from closed down mines and terminated exploration there often exist core samples and other relevant information which can be accessed. This can result in great savings in time and money required for new activi-ties. One of the cheapest phases of property exploration is preparation of a comprehensive, detailed and accu- rate geological map which often starts with basic instruments such as tape and compass. The accuracy can be enhanced by using air photos to help locate out-crops, major fault zones and basic topo- graphic control. Each step adds some more costs, but it also improves the ac-curacy and detail of the resulting map.

Soil-covered ground is inaccessible to the prospector, whose first check would be to look for an outcrop of the mineralization. Where the ground cover comprises a shallow layer of alluvial material, trenches can be dug across the mineralized area to expose the bedrock. See picture to the right.

A prospector will identify the disco-very, measure both width and length, and estimate the mineralized area. Samples from the trenches are sent to the laboratory for analysis. Even when minerals can be found on the surface, determining any extension in depth is a matter of qualified guesswork. If the prospector's findings, and his theorizing about the probable existence of an ore-body are solid, the next step would be to explore the surrounding ground. Exploration is a term embracing geo-physics, geochemistry, and finally the more costly activities viz drilling into the ground for obtaining samples from any depth. Table 1 shows the sequence in time of various exploration methods.Efficient mineral exploration depends on increasingly sophisticated map

production for planning purpose and access routes, for geological, geophysi-cal, geochemical and structural mapping. Today detailed aerial topographic maps are available in many parts of the world giving the explorer basic information to determine where to find areas with good mineral potential.

geophysical explorationAfter their introduction in the 1950’s airborne geophysical surveys became commonly used as a first step in geo-physical exploration.

Large areas can be effectively cov-ered in a short period of time. The most

Are there minerals in the trench? International Gold Exploration AB, IGE conducts exploration works in Burundi.

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common aero-geophysical maps are magnetometer maps which record the variations in the earth’s magnetic field with high degree of accuracy. The opti-mal selection of altitude and spacing as well as choice of instrumentation is important.

From surface, different geophysical methods are used to explore subsurface formations, based on the physical pro- perties of rock and metal bearing mi-nerals such as magnetism, gravity, elec- trical conductivity, radioactivity, and sound velocity. Two or more methods are often combined in one survey, to acquire more reliable data. Results from the surveys are compiled, and matched with geological information from sur-face and chips or core samples from any previous core drilling, to decide if it is worth proceeding with further explora-tion. If yes, the information form basis for future drilling campaigns. As geo- physical survey is commonly conduc-ted from the air to begin with, infor-mation from the surface surveys are compared and added to the airborne mapping.

Magnetic surveys measure variations in the earth's magnetic field caused by magnetic properties of subsurface rock formations. In prospecting for metallic minerals, these techniques are par- ticularly useful for locating magnetite, pyrrhotite and ilmenite. EM (Electro-magnetic) surveys are based on varia-tions of electric conductivity in the rock mass. A transmitter is used to create a primary alternating electromagnetic field. Induced currents produce a secon- dary field in the rock mass. The resul- tant field can be traced and measured, thus revealing the conductivity of the underground masses. Electromagnetic surveys are mainly used to map geologi- cal structures, and to discover mineral deposits such as sulphides containing copper or lead, magnetite, pyrite, gra- phite, and certain manganese minerals. Electric surveys measure either the na-tural flow of electricity in the ground, or “galvanic” currents led into the ground and accurately controlled. Electrical surveys are used to locate mineral deposits at shallow depth and map geological structures to determine the

depth of overburden to bedrock, or to locate the groundwater table.

IP (Induced polarization) surveys are conducted along grid lines with read-ings taken at receiving electrodes plan-ted in the earth and moved from station to station. The electrodes, connected to a receiver, measure the chargeability (the capacity for various minerals to build up a charge of electricity) and resistivity effects on current forced into the ground and bedrock. The minerals detected by IP surveys are generally the same as for EM methods.

Gravimetric surveys measure small variations in the gravitational field cau- sed by the pull of underlying rock masses. The variation in gravity may be caused by faults, anticlines, and salt domes that are often associated with oil-bearing formations. Gravimetric surveys are also used to detect high-density mine- rals, like iron ore, pyrites and lead-zinc mineralizations. In regions where rock formations contain radioactive mine- rals, the intensity of radiation will be considerably higher than the normal background level. Measuring radiation

Airborne and surface geophysical survey map indicates where drill holes will be located, ref Lappland Goldminers, photo Patrick Trädgårdh.

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levels helps locate deposits containing uranium, thorium and other minerals associated with radioactive substances.

Seismic survey is based on variations of sound velocity experienced in diffe- rent geological strata. The time is mea- sured for sound to travel from a source on surface, through the underlying lay- ers, and up again to one or more detectors placed at some distance on surface. The source of sound might be the blow of a sledgehammer, a heavy fallen weight, a mechanical vibrator or an explosive charge. Seismic surveys determine the quality of bedrock and can locate the contact surface of geological layers, or of a compact mineral deposit in the ground. Seismic surveys are also used to locate oil-bearing strata.

All results from the survey are super- imposed on maps which will show dozens or often hundreds of anomalous patterns which are useful when opti- mum location of drill holes are decided.See picture to the left

geochemical surveying

Geochemical surveying is another explo- ration technology featuring several spe-cialities, the main one being to detect the presence of metals in the topsoil. By taking a large number of samples over an extended area and analyzing the con-tents of each metal, regions of interest are identified. The area is then selected for more detailed studies.

The geochemist will take stream samples on a regional basis covering many square kilometers of the supposed favourable terrain. That survey will be followed by more detailed sampling of variations in chemical composition of drainages and by soil sample grids in anomalous areas. The area chosen might be relatively acidic or the metal ions in the ground water being neutralized by a bed of limestone. Rapid and accurate analytical methods such as atomic emis- sion spectroscopy (ICP) have made it possible to determine many elements, commonly 30, in each sample which generates a vast amount of data.

Exploration commonly includes programs of soil sampling. This entails digging holes at certain intervals to collect soil samples from identified horizons. The samples are placed in

bags, dried, screened to collect the finer material and analyzed for “pathfinder” elements. A soil sampling survey might result in thousands of samples which need computer programs for efficient data handling.

Geochemical surveys can also be con- ducted on rock chips from outcrops or rocky debris. Biochemical surveys might use leaves or bark in forested regions or plants and sage brush in arid environ-ment.

exploratory drilling

The next and most expensive part of the exploration sequence is drilling. For a driller, all other exploration methods are like beating about the bush. Drilling penetrates deep into the ground, and brings up samples of whatever it finds on its way. If there is any mineraliza-tion at given points far beneath the sur-face, drilling can give a straightforward answer, and can quantify its presence at that particular point. The expenditure for drilling comprises about half of the total exploration costs mentioned above.

There are two main methods of explo-ratory drilling.

Core drilling, yields a solid cylinder shaped sample of the ground at an exact depth. Percussion drilling yields a cru-shed sample, comprising cuttings from a fairly well-determined depth in the hole. Beyond that, the drillhole itself can provide a complementary amount of information, particularly by logging using devices to detect physical anoma-lies, similar to the geophysical surveys mentioned above.

Core drilling is also used to define the size and the exact boundaries of mineralization. This is important for determining ore grades being handled, and vital for calculating the mineral re-serves that will keep the mine running in the future. A strategically placed under- ground core drilling may also intersect new ore bodies in the neighbourhood.

The core is an intact sample of the underground geology, which can be examined thoroughly by the geologist to determine the exact nature of the rock and any mineralization. Samples of special interest are sent to a laboratory for

Airborne geophysical surveys.

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analysis to reveal any metal contents. Cores from exploration drilling are sto- red in special boxes and kept in archives for a long period of time. Boxes are mar- ked to identify from which hole, and at what depth, the sample was taken. The information gathered by core drilling is important, and represents substantial capital investment.

To obtain fast geological information at less costs, reverse circulation methods are commonly used. Instead of core

samples the geologist gets access to drill cuttings (chips) throughout the hole length which are checked and mapped for mineral content after laboratory analyses.

Reverse circulation drilling as a method is rapidly gaining popularity for surface drilling applications. Compared with core drilling equipment, which are readily disassembled, the rigs are truck mounted and restricted to accessible terrain and better road conditions.

From prospecting to mining

To quantify the mineralization, and to define the shape, size and metal content of the deposit, the step by step proce-dure in exploration activities is required. At every step of the procedure, the geo- logists examine the information at hand, to recommend continuing the explo- ration efforts. The objective is to be fairly certain that the deposit is econo-mically viable by providing a detailed knowledge of the geology for a clear financial picture. Ore is an economic concept, defined as a concentration of minerals, which can be economically exploited and turned into a saleable product.

Before a mineral deposit can be label- led as an orebody, full knowledge is required about the mineralization, proposed mining technology and pro- cessing methods. The environmental impacts of mining and mineral pro-cessing are carefully studied and need approval. In case no serious negative impacts are found, the owners apply for permission to conduct mining opera-tions in the area. A prerequisite for this application is owner's confidence of sustained profitability over a long pe-riod of time. At this stage a compre-hensive feasibility study is undertaken covering capital requirements, returns on investment, payback period and other essentials, in order for the board of directors of the company to make the final decision on developing the prospect into a mine. The costs for a feasibility study is quite substantial and could reach an amount of approxi- mately of 5% of the required capital costs for the entire mining project. Based on all geological documentation and the study the owners get a good idea of how to mine the deposit; whether it will be surface open pit mining or underground operations with or without backfilling of the excavated stopes. In the majority of cases mining will start with open pit excavation gradually turning into underground mining once the waste to ore ratio becomes too excessive at dee- per horizons. Fig 1 shows initial mining plans at the Suurikuusikko gold mining project in northern Finland.

hans Fernberg

Fig 1. Two computer generated views of Agnico Eagle's Suurikuusiko gold mining project showing both surface and underground mining.

Exploration Results

Mineral Resources Ore Reserves

Increasing level of geological knowledge and confidence

Indicated

Inferred

Measured Proved

Probable

Consideration of mining, metallurgical, economic, marketing,legal, environmental, social and governmental factors

(the ”modifying factors”)

The 2004 Australasian code for reporting exploration results, mineral resources and ore reserves.

exploration drilling 19

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What´s in the cores?

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Technical logic

Since man first started searching for minerals and precious metals, three key factors have consistently proved decisive for success: time, cost and confidence. In other words, the time required, the cost of getting the job done, and con-fidence in the quality of the samples brought to the surface for analysis.

This is more a question of basic tech-nology and logic than one of science.

Drilling methodsCore drilling produces cores of sub- surface material and is the most com-monly used method of obtaining infor-mation about the presence of minerals or precious metals, as well as rock forma-tions. This method gives the geologist the opportunity to analyse the sample by eye as well as by more advanced me- thods. As the samples are placed in core boxes piece-by-piece and carefully mar- ked, it gives a full picture of the rock strata.

RC drilling by percussive air DTH hammer is a fast method due to higher penetration rate compared with tradi-tional core drilling and gives a lower cost per metre. At shallow investigations it is used alone and at deeper exploration as an economical way of precollaring in order to get down to where the mine-ralization is located. Once there, it can

be decided whether to continue with RC drilling to extract chips for evaluation, or to switch to diamond core drilling to extract cores. In this way, RC drilling becomes the perfect complement to con- ventional core drilling.

Selecting which method to use for actual sampling work depends on the actual conditions, surface or under-ground, depths of the holes, rock condi-tions, and the preference of the geologist. But it also depends on the confidence that he or she places in the quaity of the samples. Modern core drilling rigs carry out fast and efficient core sampling of different diameters to very large length, and RC drilling has become so advanced that more and more geologists believe that chips are perfectly sufficient as a means of determining mineralization.

Hence, surface drilling offers a choice between chips, core or a combination. Underground RC is possible technically,

Explorac 220RC Reverse circulation rig in operation in Australia.

in search of the right balance

Chips or cores? The question often faced by geo-logists is deciding which method of exploration drilling will get the most effective and economi-cal results. Core drilling, Reverse Circulation drilling (RC), or a com-bination of the two?

exploration drilling 21

Talking TeChniCally

but is still only used to a very small extent.

early birdsAs early as 1887, Craelius developed a rig that could recover cores at depths of 125 m. Confidence in these samples among geologists was very high, in that they were able to evaluate a piece of solid rock. Time was not necessarily of any great importance, and consequently neither was cost. Manpower was in-expensive and readily available.

Hydraulic drill rigs were launched in the early 1970s and progressively improved. In 1997, Atlas Copco intro- duced computers into their control sy-stem, and 10 years later, the current version of Diamec U6 APC (Automatic Performance Control) represents the 4th generation of computerized rigs. It incorporates the latest hydraulic and electronic technology into a modern compact design and includes many op-tions that offer added flexibility.

For surface mineral exploration and mineral grade identification the rela-tively low cost and rapid Reverse Circu- lation method has gained popularity, while underground core drilling is still the predominant method. One reason for this is the need for smaller and lighter equipment suited to shaft transportation and set-up in limited areas, coupled with the ability to drill deeper holes in all directions.

For surface exploration drilling, the core drilling rigs have been developed to higher efficiency and safety, inde-pendent of type of method used, pulling

rod with a main hoist or with the ro-tation unit.

The first RC rigs were water well drilling rigs equipped with a sampling system. Today, there are special RC

drilling systems, rigs, RC air hammers, DTH equipment, high-pressure com- pressors and sampling systems. To- gether, these offer efficient and safe drilling to increased depths, obtaining

Fig 1: Principles for RC drilling showing flow of compressed air and chips. The sampling collection box isintegrated into the cyclone.

0

20

40

60

80

100

Canada LatinAmerica

RussiaChina

Australia SE Asia USA Africa

RC drillingCore drilling

%

Table 1: Ratios between core and RC drilling. The figures reflect total exploration expenditures from national statistics for surface and underground.

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high quality samples. Atlas Copco RC rigs are controlled by tested and proven computer technology to help drillers to achieve optimal performances.

Time factor

For all exploration drilling the sample is the most important result. Time is money, with the cost of exploration paid up front, followed by a period of non-profitable waiting while the results are analyzed. For core drilling, depending upon depth, the actual drilling time is estimated to be a third of the total time

to extract a full core barrel because of the pumping in, pulling out, and adding and removing rods. RC drilling offers continuous drilling with a higher pene- tration rate. Percussive drilling is always faster than rotary abrasive but has prac-tical restrictions on hole depth and dimension, which is normally no smaller than 125 mm.

RC drilling can offer three times the productivity of core drilling, with an RC hole down to 250-300 m taking no more than a 10-12 h shift depending on drilling conditions, rock formation, and the driller’s ability. Cost comparisons

between the two methods should be ba- sed on the same factors as productivity.

Cost factor

Costs are mainly related to the time fac- tor, except that investment in RC rigs and equipment is higher compared to core drilling. For shallow exploration appli-cations, time and costs are in favour of RC drilling. The figures are easy to evaluate and vary depending on the location, and on the local drilling con-ditions and working environment.

For deeper exploration applications, shallow subsoil water and rocky terrain, core drilling is still the only practical alternative. Technical developments in drilling tools and rig technology have resulted in lower drilling costs. Due to substantially longer diamond core bit life, less down time and reduced num-ber of personnel are experienced.

Confidence factor

The third variable in the equation is the confidence factor. Investors, as well as geologists, expect contractors to deliver high quality information about the geo-logical formation. Investors want the highest possible return on their invest-ments in the shortest possible time. For example, whenever a gold nugget has been found, others may take over to conduct the drilling and blasting operations. As these are not the same people, the reliability of information plays a critical role.

Geologists choose their drilling me- thod carefully. If there is no need for continuous information about the geo-logical formation on the way down to a specified depth, there is no need for samples. It is just a matter of mini-mizing the drilling time.

If the goal is just to obtain a preli-minary indication of possible content, then the geologist is not relying on any mineralized structure or geometry. With an evaluation giving positive re-sults, a programme of core drilling is the logical way to continue, in order to bring the project to a resource/reserve status.

If the mineralized structure is identi- fied, but the geometry and rate of con- tent varies, RC drilling is used as an

Caption

Christensen CS1000P4 surface core drilling rig operating in Zambia.

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indicator for ensuring continued grade control. The geologist wants dry and representative samples in order to make optimal evaluations.

RC drilling below the groundwater table was previously believed to under-mine sample quality. Core drilling there- fore remained the only viable method for these depths. Today, the availability of high-pressure compressors and hammer tools makes it possible for RC drilling to reduce costs, even for these depths. These days, professional contractors deliver dry sampling down to depths of 500 m. By sealing off the bit from the rest of the hole, it can be kept dry.

In these cases RC drilling is the pre-ferred alternative.

It must be remembered that informa-tion from a core is crucial in estimating the period of mineralized structures. The core helps the geologist to calculate the cost of extracting the mineral from the ore. Large volumes of rock have to be excavated to obtain just a few grams of a valuable mineral.

Cores also yield geotechnical data. Data about slope stability can be of the highest importance.

Tradition and the environmental im-pact play a large role. RC rigs are heavy, assembled on trucks or track carriers. This fact tends to favour core drilling rigs, which are lighter and more adapt-able in order to be flown into remote and sensitive environments.

In areas with extremely cold climates, and where permafrost is present, RC drilling may have its limitations. Anti-freeze rock drill oil helps to keep the hammer and bottom of the hole free from ice. Other, purely practical, issues determine the choice of one or the other drilling method.

An intelligent, balanced choice be-tween the two methods is the key to optimal results.

The geologist plays an extremely im-portant role in finding this balance, as do manufacturers such as Atlas Copco who continue to provide the right tools for the job.

anders gustafsson

Diamec U6 underground core drilling rig in a typical setup.

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RC methodology

The RC method employs dual wall drill rods that comprise an outer drill rod, with an inner tube located inside the drill rod. The inner tubes overlap, and seal on the tube below with O rings when the drill rods are screwed together. These inner tubes provide a continuous sealed pathway for the drill cuttings to be transported from the bit face to the surface.

The circulating medium, in most ca- ses high-pressure air, enters the annu-lus between the rod and tube via the air swivel, which is normally part of the drill string, or sometimes mounted on top of the rotation head. The air travels down the annulus to the drilling tool, which is usually an RC hammer, or can be a blade bit or tricone roller bit.

As in conventional open hole drill-ing, the air powers the drilling tool and the exhaust air carries the cuttings. In RC drilling the cuttings are returned to the surface through the inner tubes in the drill string and rotation head.

Once through the rotation head, the air and cuttings comprising the sample change direction at the discharge blast box and are transported through the

sample hose to the cyclone. The cyclone slows the sample, separates it from the air, and collects it.

RC history

Difficult drilling conditions in some types of soft iron ore and mineral sands using conventional open hole techniques led to the development of RC drilling in the early 1970s for sampling. A dual tube configuration, occasionally used in the US oil industry, was adopted as the basis for the RC drill rod. The first RC drill rods were made in 1972 by Bruce Metzke and John Humphries in Kalgoorlie, Western Australia.

Shrouded tricone roller bits were initially employed in softer formations, returning previously unheard of sample accuracy and target depth achievement. The development of the crossover sub facilitated the use of conventional DTH hammers, and thereafter RC could be applied to almost all ground condi- tions. Speed and cost advantages over

diamond drilling led to a boom in RC drilling, and by the late 1980s more than 2 million m/y of RC exploration drill-ing were being completed in Western Australia alone.

The need for cleaner samples led to the development of the RC hammer in 1990. High-pressure boosters and auxiliary compressors were introduced for deeper holes and faster penetration. Air pressures up to 100 bar (1 500 psi) were available, driving necessary ad-vances in all aspects of RC drilling and RC systems.

In the late 1990s, gold processing improved, viable ore grades became lower, but mining costs were higher, so many mines looked to improve their ore selection processes.

One of the easiest ways to do this was grade control drilling, and RC drilling was the most cost efficient and accurate method available.As a result, RC drill-ing is now being used for initial explo-ration, ore body development drilling, and in pit grade control drilling.

Explorac 220 in Australia.

an introduction to Reverse Circulation drilling

Reverse Circulation, or RC, drilling is a fast and cost efficient method of retrieving high quality samples from exploration and mine drilling. The system has been continuously developed since its inception in Australia in the early 1970s, and is now a preferred method for initial exploration, ore body deve-lopment and in-pit grade control. Any method is only as good as the equipment developed around it, and Atlas Copco has called on the experience of drillers worldwide in order to perfect its offering. Rigs such as the Explorac 220RC are revolutionizing exploratory drill-ing, producing samples faster from deeper holes and in more diffi- cult situations.

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RC benefits

RC drilling provides virtually uncon-taminated cuttings to the cyclone. As the cuttings travel directly from the drill bit through the steel inner tubes and sample hose, there is no cross contamination from other areas of the hole. Using good sample splitters and sampling proce-dures, RC results rival the accuracy of diamond core assays.

Drilling penetration rates are simi-lar to open hole drilling, and are often faster at greater depths. The sample velo- city through the inner tubes can be up to 250 m/sec, so retrieval of the sample and hole cleaning is rapid.

Production rates of up to 200-300m/day are common at rates exceeding 10 m/h, many times faster than diamond drilling, and achieving rapid results for the customer.

Unconsolidated formations can often be drilled and sampled without casing. Washing and scouring of the hole is minimized, because there is normally no fluid or cuttings flow against the walls after the drill bit has passed. Low impact bits, such as RC blade or RC roller, are ideal in these soft or loose formations.

With good drilling techniques, sam- ples can be kept dry, even several hundred metres below the water table. Dry sam-ples are preferred as they split more accurately for assay, and are easier to handle. RC sample content ranges from dust to 25 mm chips, and is already partially processed for analysis.

Wireline surveying of the hole is still possible through the drill rods. With the use of a stainless steel rod at the bottom of the string, hole azimuth readings are also possible.

Drill string

The components in an RC drill string have a similar arrangement to those of a conventional drill string, but are de-signed specifically for RC drilling, with all components having a central inner tube. As these inner tubes carry almost all of the cuttings from the hole at high velocity, they are subject to wear.

The rate of wear is governed by the air volume and pressure of the rig, and the type of formation being drilled. Explorac 220 with cyclone and cone splitter.

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Apart from the hammer inner tubes, which may only last a few hundred me-tres in extreme conditions, the remaining components should last for several thousand metres of drilling.

Drilling tools

There are generally only three types of down hole tools used in RC drilling: hammer, roller and blade.

The RC hammer is the most common method used, drilling almost all forma-tions with few changes required. The commonest hammers are in the 4-5 in range as these meet the power, standard drill strings, and sample size require-ments.

The hammers work on the same principles as conventional hammers, but with a hardened, replaceable inner tube through the centre. The inner tube extends into the top of the drill bit. A conventional hammer exhausts the air through the bit, whereas a RC hammer exhausts around the outside of the bit splines and around the head of the bit, forcing the sample through the holes in the face of the bit and upward through the inner tubes.

To help create a higher pressure zone above the bit face, and to force the sample up the inner tubes, a sealing ring is situated above the bit. This ring can be described as a shroud, sleeve or compensator ring and is mounted

on the drive sub, or bit chuck, and is usually replaceable.

The RC hammer bit is similar to con- ventional hammer bits, but with two large ports in the face and a large bore through the centre to accept the hammer inner tube. There are deep channels on the outside of the drill bit head to allow the exhaust air to flush the sample into the ports in the face.

An RC roller setup comprises a sub onto which a bit and skirt similar to a hammer shroud are screwed directly to the drill string. The bit is normally a standard mill tooth tricone roller bit, modified to allow a shroud to be fitted.

The RC roller is only suited to softer formations, but can be extremely fast and produces a very accurate sample and very little disturbance in the hole. It requires minimal air volume, and down hole costs are low, so it is a very economical method of drilling. RC blade uses a sub and skirt setup similar to RC roller, but with a drag blade as the cutting tool. Used in heavy clay formations, which can be difficult or impossible with hammer or roller, it can be very quick and produces an accurate sample.

Rotating parts

RC drill rods consist of an outer tube, the rod, and an inner tube. The rods are externally flush and provide the strength

From top: RC bit face, RC bit with a shroud, RC saver sub, digout sub, RC blade with skirt, Adapter sub.

RC rod with inner tube.

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for the assembly, and also the pin and box threads. RC drill rod threads have been developed to retain strength while maintaining a large hole through the centre for the inner tube and airway.

The inner tube is installed into the rod through the box, or female, end, and usually sits on a shoulder in the rod and is retained with a circlip. Each inner tube has a male and female end, one of which has O-ring seals. Once the rods are screwed together the inner tube ends overlap, and the O-rings seal the tubes.

The annulus between the rod and inner tube carries the high-pressure air to the drilling tool, while the inner tube provides a smooth bore sealed tube to carry the cuttings to the surface.

Most drill rods are 3 m or 6 m long, and run pin down because of the inner tube installation.

The most commonly used rod size is 4.5 in (11.43 cm), coupled with a 5 in (12.7 cm) hammer and 5.25 (13.3 cm) to 5.75 (14.6 cm) in bit, but rods are also available from 3.5 (8.9 cm) in to 5.5 in (14 cm) to suit other rig or drilling requirements.

The inner tubes are a wearing, but easily replaceable, item.

As with any drill string there are va-rious subs used for adapting, reducing, and stabilizing. These are all available for RC drill strings.

The air swivel feeds air into the drill rod annulus, while still retaining an inner tube to allow sample flow. They can be either in-line in the drill string immediately beneath the rotation head, or mounted on top of the head as an integral part of the head.

The rotation head on an RC rig has a large bore through the spindle to allow for the replaceable sample inner tube. RC heads are usually built to provide high torque at moderate speed, with at least 10 000 Nm and 100 rpm normal for larger rigs.

Discharge system

The discharge system is the non-rotat-ing part of the sample path that carries the sample from the rotation head to the sample cyclone. It normally consists of a mud swivel, blowdown valve, blast box, discharge manifold and sample

hose. The mud swivel, blowdown valve, manifold and blast box all mount rigidly to the top of the rotation head. The mud swivel seals the rotating head shaft and inner tube from the stationary parts of the discharge system. The seals in the mud swivel are critical as they need to contain the pressurized flow of sample.

Most RC rigs now have a blowdown valve fitted to the discharge system. This is usually a hydraulic or air driven valve that closes off the sample inner tube and redirects the downhole air flow down through the sample inner tubes.

This function is used to clear block-ages in the bit ports or the inner tubes, and to force all air up the outside of the drill hole, hence cleaning the hole.

It is done without having to de-pressurize and unscrew the drill string to add a sub, so is a very useful tool in difficult drilling conditions.

The blowdown is mounted on top of the mud swivel. The sample stream can be travelling at up to 250 m/sec and needs to be redirected towards the cyclone. The blast box usually turns the sam-ple flow about 90 degrees to meet the sample hose. This direction change also reduces the energy of the sample considerably, but in doing so incurs very

high wear. Most systems have easily re- placeable wear components in this area.

The discharge manifold extends side- ways from the blast box. It helps slow the sample to reduce sample hose wear and also holds the hose clear of the drill rig as the head travels up and down. There is often provision to inject small amounts of water into the manifold to mix with dry sample and reduce the dust at the cyclone. The sample hose is a heavy materials handling hose specially manufactured for RC drilling. The hose transports the sample from the dis-charge manifold to the sample cyclone, and is long enough to allow for the movement of the rotation head up and down the mast.

Sampling

The majority of RC drilling is done to obtain mineral samples for analysis, so correct sampling equipment and prac-tices are necessary when undertaking this type of drilling.

There are two main components to the sampling system: the cyclone; and the splitter.The cyclone serves to reduce the speed of the sample stream, and to separate the sample from the air, allo-wing it to be collected. It is important to have an efficient cyclone to remove

Standard roller bit and drag bit.

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as much of the sample as possible, and also to avoid contamination of samples. A good cyclone will typically collect greater than 99% of the sample, with the remaining dust and air going to a dust collector or to atmosphere.

The cyclone should be able to hold two complete sample intervals without contamination. An area of the cyclone called the dump box is equipped with a door or knife valve for this purpose. The sample interval is normally 1 m or 2 m of hole. As one sample has collec-ted in the dump box, another is being drilled and is collecting in the cyclone. The lower dump box doors are opened to allow the sample to fall through the splitter. The lower doors are then closed, and the upper doors are opened to drop the next sample into the dump box. In this way sampling becomes a continuous process, with little or no interruption to drilling. Processing of the sample is one of the most important aspects of RC drilling. The sample from 1 m of a 5.5 in drill hole is about 30 lit, or up to 50 kg.

The purpose of a splitter is to divide the sample down to a smaller size that is an accurate representation of the complete sample. This assay sample is collected in a bag and sent to a labora- tory to be analysed for various minerals. Two main types of splitter are in use. Riff le splitters use several tiers of

dividers that halve the sample at each level, until the assay size is reached. This usually involves 3 or 4 tiers to give 12.5% or 6.25% of the total sample. Riffle splitters are easy to use and clean with dry sample, but do not perform too well with wet samples. Tiered riffle splitter, sometimes known as a Jones riffle splitter. These essentially divide the sample in two at each tier. Half the sample goes to waste and the other half to be split at the next tier and so on. The number of tiers dictate the final assay sample size, see picture above. Cone splitters drop the entire sample over the point of an inverted cone and allow it to run down the cone. The assay sample is taken by collecting a segment of the sample as it runs off the edge of the cone. This segment size can be adjusted to collect the required percen-tage for assay. Cone splitters can give a more accurate split, but are more sensi-tive to setup than riffle splitters. The con splitter works by dropping sample through a 120 mm hole over the point of a cone in an “hourglass effect”. This provides an even flow of sample over the cone. Beneath the bottom of the cone are 2 segment shaped chutes that direct a percentage of the sample to the assay bags. These chutes are adjust-able to take between 3 and 12% of the total sample. One is used as the assay

sample, the other for a dublicate sample. The waste materials falls through a chute and can be either collected in a large bag or wheelbarrow or left as waste, see picture above.

Rotating cone splitters are used for wet sampling, as they reduce or eliminate the bias that is created as a wet stream favours one portion of the splitter.

Drilling guidelines

RC Drilling has many similarities to conventional DTH drilling, but there are also many procedures and tech-niques that are required to achieve the best results.

In RC drilling, the hole is of little importance, while the sample is para-mount. Holes are normally set up in a similar way to a conventional hole, with a short length of collar pipe or conduc-tor casing set at the surface. A stuff-ing box, Tee piece or deflector box is mounted on the collar pipe to direct any lost sample or outside circulation away from the drill rig. Rotation speeds and feed weights are similar to conventional drilling.

As much sample as possible should be retrieved from the hole. It is prefe-rable to have at least 95% inside circu- lation, so that most of the sample is coming through the inner tubes and only

Side inlet air swivel. Tiered riffle splitter. Cone splitter.

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5% or less is being lost to outside. It is not uncommon to retain 100% inside.Achieving high inside circulation sample return is achieved by having the correct clearance between the bit shroud and the hole wall, thus creating a seal and forcing all sample up the inside. It is also common to allow the hole to collar off above the hammer to help with sealing. This collar will often breach when the water table is reached in the hole, or it can easily be blown out using the blowback sub.

If there is water in the hole, allowing the hole to collar off helps in keeping the samples dry. Dry samples split far more accurately, and are much easier to store, transport and process.

Auxiliary compressors and high-pressure boosters up to 100 bar are now commonly used with larger RC rigs. These are necessary to keep the hole dry, producing a dry sample and also achieving far greater hole depths.

It is almost inevitable that material will fall in behind the hammer or bit, causing the drill string to become bog-ged. This is normal for RC drilling, and it is common to run a short, sta-bilized dig-out sub above the hammer for protection when digging through fallback.

Blowdown valves are fitted to almost all large rigs now to help clean holes, and are usually used at each rod change to ensure the hole remains clean, or to remove excess water from the hole. Blowdown subs are available for inser-tion into the drill string, but these have to be removed to continue drilling.

Safety with reverse Circulation DrillingThere is a wide range of safety regu- lations and requirements that vary from site to site, but some general rules will apply almost everywhere.

While there are some potential ha-zards associated with the RC system, the normal safety requirements for the Explorac still need to be observed.

RC drilling requires one or more ‘Samplers’ or ‘Offsiders’ who process the sample from the cyclone and they are also often required to manually handle some of the downhole equip-ment.

They work close to the cyclone and the rig mast, so they can be exposed to hazards not usually encountered during standard production drilling.

While engineering solutions have been made for most hazards, the prox-imity of people to the machine in this type of drilling demands vigilance and management.

The customer should have a safety management system in place and all hazards should be assessed – most can be managed with procedures.

Manual handling:• Strains and inju- ries can be received with handling of heavy samples, hammers, bits etc.

Falling objects: • Due to the vibrations involved in percussion drilling there is potential for objects to shake loose from the rig mast. Correct maintenance and regular inspections are required.

High pressure air:• Can be extremely dangerous. All HP air hoses, inclu- ding the sample hose should have sock type restraints on each end. Sample hose clamps should be cor- rectly fitted and couplings tightened.

Pinch points:• There are many areas around the rig with potential for pinch or crush injuries. Mast boom and ro- tation head movement, rod loader movement, cyclone tilt and rotate, and the cyclone doors can all present some

hazard. Procedures, and communi- cation between the driller and sampler are essential here.

Personal protective equipment (PPE): • Appropriate personal protective equip- ment (PPE) should be in use at all times; ear plugs, dust masks, safety boots, hard hat and gloves. These items are considered as statutory require- ments in most mining environments.

Summary

RC drilling is a well-respected method within the exploration industry. It is fast and efficient, providing accurate samples for evaluation by the geolo-gists using tried and tested techniques. The method is undergoing continuous technical development that will result in RC drilling being applied to deeper holes and more difficult geological con-ditions. RC drilling is frequently used in conjunction with core drilling for a better result in certain circumstances.

The RC drilling method uses high torques, high pressures, big lifting capacities and rapid collection of sam-ples, so safety is a major factor in the ongoing design process.

Jan Jönsson

Explorac 220 under testdrilling in Australia.

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RC hammer

With a conventional DTH hammer, there is a risk of contamination as the sam-ple is transported between the hammer casing and the hole wall to the collector sub. Demands for cleaner samples were identified in the early 1990s, and the first true RC hammer was developed with sample collection at the face of the drill bit and removal of the cuttings through the centre of the hammer to the dual wall drill pipe. This technique provides a true sample from the bit face with minimum risk of contamination.

Higher air pressures were needed to achieve higher productivity, and to be able to drill deeper holes. The use of auxiliary compressors and high- pressure boosters resulted in air pres-sures up to 100 bar, leading to necessary advancements in all aspects of the RC system. RC drilling is now a common method used for surface mineral explo-ration drilling throughout the world, and it is gaining increasing acceptance. The method offers: representative samples with high recovery rate; more accurate samples in low-grade ores; continuous sampling from the hole bottom; uncon-taminated samples; straighter holes in

The RC50 hammer from Atlas Copco Secoroc is designed for both deep hole exploration drilling and In-Pit grade control.

Reverse circulation drilling with new hammer concept accurate samplingReverse Circulation (RC) drilling is gaining recognition and is already the most common mineral explora-tion drilling method used in many regions of the world. Combined with the Secoroc RC 50 hammer it is unbeatable for obtaining accu-rate and uncontaminated rock sam-ples at high speed and low cost. Atlas Copco produces the complete RC drill string including hammer, bit and pipes, for both in-pit grade control and exploration drillers. Mounted on a choice of Explorac 220RC, Explorac R50, ROC L8RC and RD10 rigs, the system is the most productive available.

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broken formations; high productivity; reduced drilling costs; large bulk sam-pling capability; and penetration of un-consolidated formations with cavities without loss of circulation.

in-pit grade control

Atlas Copco has focussed on two main applications: in-pit grade control and normal exploration drilling.

Gold processing techniques improved during the 1990s, making previously uneconomical ore grades viable, but with increasing costs for the entire pro-cess. "Mining operations had to improve their cost effectivness, the importance of knowing what grades to expect before the blast were identified. In Pit Grade Control returns an uncontami-nated sample, providing needed know-ledge of what grades to expect as well as the possibility to select what bench to blast next. This information makes it possible to to reduce waste rock in concentrator feed (dilution) as well as minimize the risk of transporting valuable ore to the waste dump." The importance of grade control and minimized dilution is increasing around the world. Dilution is defined as waste rock in concentrator feed, and can vary from 5–40% between different mines. The amount of waste raised from the mine is estimated by the geologists, but the actual process dilution is hard to measure. Dilution means not only lower grade ore, but also reduced profit.

One of the easiest ways to control dilution is to use in-pit grade control, where RC drilling is the most cost-efficient and accurate method available. In-pit grade control is used in existing operating mines to define and map boundaries between waste and ore, and variations in mineral content, in order to optimize ore recovery rates.

Another major application typical of, for example, iron ores, is to define the different ore grades in order to be able to mix them into set grades, giving increased efficiency of the ore process.

Mineral exploration

RC drilling has two shortcomings when compared to core drilling. Firstly, because dual wall pipes add a lot of weight

to the RC drill string, most of the RC drill rigs used today have a limitation in depth of 200-400 m. Secondly, RC drilling yields less information regarding the geological structure of the orebody. This is quite an important factor when estimating the cost of extracting min-eral from ore.

So, while coring yields a good physi-cal sample on which the geologists can rely, RC drilling is faster and more flex-ible, affording economic sampling over longer distances in the hole.

As a result, the two methods are often used in combination by mine operators, using RC for drilling shallow holes and in-pit grade control, and core drilling for deeper holes to identify future resour- ces. Furthermore, many exploration con- tractors drill the first part of their hole with RC, and then continue to the total depth with core drilling techniques.

The new RC 50 hammer

In recent years Atlas Copco RC tech-nology has evolved, and the Secoroc RC 50 hammer concept has been tested and refined. The RC 50 was released in 2008, along with three new RC drill rig configurations known as Explorac 220RC, Explorac R50, ROC L8RC and RD10.

The RC 50 hammer has the follow-ing features: higher stroke frequency performance; simpler design and fewer parts; built on the efficient Quantum Leap air cycle.

These features give five main ben-efits for RC drillers: high productivity; high recovery rate; quick and easy ser- vice; low fuel consumption; and de-creased cost per metre drilled.

The Secoroc RC 50 hammer is de-signed for the hole range 140-152 mm, and during tests has proven to be more productive than any other RC hammer available on the market. Another attrac-tive feature that adds to the productivity of the hammer, as well as availability of the rig, is the outstanding service life of wear components.

Fredrik gabrielsson

Cuttings Air flow

Reverse Circulation hammer

ConventionalDTH hammer

Fig 1: The DTH hammer flushes cuttings out of the hole on the outside of the hammer, while the RC hammer collects all cuttings through the centre of the hammer.

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importance of control

To get the best penetration rate and core recovery it is important to be able to control the speed of the rotation unit

and the feed and pull force in the feed frame.

It is important to understand what is happening in the bottom of the hole. For example, the feed force has to be compensated with the right amount of holdback when adding rods to the hole to ensure the right pressure on the bit in the bottom of the hole. Not too much, but enough for good penetration. The chapter on bit selection elsewhere in this book is a useful reference.

To empty the core barrel when drilling conventionally, and to change the bit when drilling wireline, all of the rods have to come out of the hole. This involves rod handling which is a very heavy, time consuming, unpro-ductive, and sometimes dangerous,

part of the work. Therefore a lot of ef- fort has been put into the design of better In-The-Hole tools and bits with longer life. The focus on the rigs is to make them more user-friendly, ergo- nomic, and faster when handling rods. Because of the potential risk for accidents with rotating rods and high pressure hydraulic hoses, operator contact with the rig is to be avoided as much as pos-sible. For this reason, all Diamec rigs delivered from Sweden today are equip- ped with a guard protecting all rota- ting parts, and all rigs have oversized couplings and other crucial components.

Transport on surface may be by truck, crawler, or trailer, but on the more re- mote sites helicopter transport may be necessary. For underground applications

The easy-to-move around Diamec 232 underground core drilling rig.

Four decades of Diamec core drilling rigs

going hydraulicFor the last 20 years, core drilling rigs have been following the same trend as most other construction equipment, moving from mecha-nical to hydraulic transmission. In core drilling, there are three main activities that control the produc-tive effort: drilling, rod handling, transport and setting up of the rig. This article compares these functions in both hydraulic and mechanical rigs

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in mines and tunnels shorter distances are involved, so a truck may be used to move the rig from site to site. Craw- ler mounted solutions reduce the set- up time and make transportation much easier In the last couple of years, Diamec rigs have been mounted on standard Atlas Copco Simba carriers. This makes the move around even easier, helping to reduce rig downtime between profi-table drilling periods.

Mechanical rigs

The old type of mechanical core drill-ing rigs are still in production in some places, mainly on account of their good reputation for robustness and easy ser-vice and maintenance.

The main components in a mecha-nical rig are: diesel or electric engine with a coupling and a four- or five-stroke gear box; rotation spindle with a hydraulic chuck; hydraulic feed cy-linder; hydraulic system; main hoist; wire line hoist; and skid with mast. Note that these rigs have a hydraulic feed system.

Drilling with a mechanical rig is har- der than with the newer hydraulic rigs. The rotation speed is rather difficult to control because of the reliance on gears, so the optimal speed for the appli- cation, ground formation and ITH tools is elusive. The feed system is similar to the hydraulic rig, but with the disad-vantage of a short feed frame. The very short stroke length demands frequent re-gripping, reducing drilling effici-ency and increasing the risk of core blockage. The rods are pulled out of the hole with a main winch and a wire. All threads are opened manually with wrenches, which is time consuming and sometimes risky. To avoid the rods falling back into the hole a mechanical rod holder is used.

Because a mast is needed for mecha- nical rigs, it is difficult to drill direc-tionally and in tight underground loca-tions. If wireline drilling, the core is taken out in a similar way to that used on hydraulic rigs.

The rigs are in general rather heavy, especially in relation to their capacity. On the positive side, they are easy to assemble and disassemble, making for simple movement in remote areas.

hydraulic rigsThe first hydraulic core drilling rig, Diamec 250, was introduced to the mar- ket in the early 1970s.

The deeper the hole, the heavier the rod string, so more lifting capacity is needed. In the underground situation, it

is important to be able to both push and pull to get the rods out of the hole.

On long holes, more torque is re-quired to rotate the rod string, because of the friction in the hole. When drilling angled holes, the friction increases, and even more torque is required. The con- clusion is that the depth capacity of

The service-friendliness of a Diamec U6 core drilling rig.

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the rig is set by at least two factors: pull force and torque. The value given in technical data sheets are often just the depth capacities, in metres/feet, for vertical down holes. When com- paring one rig with another it is pro-bably more correct to compare the power of the prime mover and the des ign of the hydraulic system, including pressure, flows, and number of pumps, rather than the stated depth capacities.

A hydraulic rig, mainly used for un- derground applications, has the follo-wing main components: feed frame; rotation unit; rod holder; skid with a positioner arm or frame; wireline winch; control panel; power unit; and water pump.

The rotation unit and the rod holder are mounted on the feed frame. The ro-tation unit comprises a hydraulic motor, a chuck and a hollow spindle, offering the most productive rod handling.

The rod holder is mainly used to hold the rods, so that they don’t fall in or out of the hole. To have a reliable rod holder

is therefore a safety issue that has been solved on the most modern rigs using a gas accumulator that keeps the jaws closed. They are opened when necessary using onboard hydraulic pressure. A hydraulic cylinder in the feed frame transfers the feed and pull force to the rotation unit. The most modern rigs use a telescopic cylinder that gives the opti-mal penetration parameters, resulting in straight holes and low risk of core blockage. Most underground rigs have the options of an 850 mm or 1 800 mm stroke length of the feed frame. The longer stroke length, the higher the productivity because of reduced regrip-ping. Every re-grip loses time-, and the rotation unit has to be stopped and re-started, which can result in vibrations in the rod string causing core blockage.

Optimal control

A hydraulic driven rig offers optimal control of the drilling parameters. The rotation speed and the feed and pull

force can be adjusted exactly. The con- trol panel has the manometers and valves needed to control the drilling, and penetration rate and rotation speed can be varied according to the ground formation.

To take up and down a rod string at a depth of 1 200 m can take the whole work shift to complete, and is a heavy and risky task. To design a good me-chanical rod handling system that re-moves the human element is difficult, but some solutions are available on the market today. The number of rods used in core drilling compared with produc-tion drilling makes it difficult to design a productive system.

The importance of setting up the rig in the right way cannot be over-emphasised. Most of the underground rigs are mounted on a skid that needs to be fixed to the ground. A wall bracket is employed to fix the rig in the drilling direction. The unique positioner arm used on the Diamec U4 and U6 helps set up the rig at exactly the correct angle.

Underground core drilling in Canada with a Diamec U6 PHC core drilling rig.

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The wireline winch is placed on the positioner arm for optimal flexibility, allowing the rig to be set in angles from vertical down to vertical up without moving the hoist.

automatic performance controlThe latest generation of Diamec core drilling rigs are computer assisted using APC, or Automatic Performance Con-trol. This is based on the well proven RCS. The operator sets the maximum and minimum values for the drilling parameters and the computer makes sure that focus is not lost. The com-puter stops the drilling as soon as the values are exceeded, or when the core barrel is full. The result is an optimal drilling procedure, with controlled ro- tation speed, penetration rate, and water flow, producing better core recovery and longer life for ITH tools and bits, resulting in more profitable drilling. The operator, who no longer has to

attend the drill rig, all the time, has more time for maintenance and core handling. The drilling procedure can be started and the rig computer left to handle the operation until the core barrel is full and it is time to hoist the core up.

Nowadays, there are more than 1 000 Diamec rigs in operation worldwide, with the highest populations in North America and Europe.

David Petersson

Diamec U8 PHC core drilling rig in operation in the US.

An operator with the control panel of the unique APC system for Diamec core drilling rigs.

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Selecting the right core bit

Selection criteriaAtlas Copco is an experienced ISO certi- fied supplier offering a full range of equipment for all underground and sur-face exploration drilling applications. This includes rigs and a full range of high technology and high quality pro- ducts, including (ITH) In-The-Hole tools and core drilling bits which are designed to maximize customer profitability.

All products are designed to mini-mize downtime and maximize produc-tivity. Atlas Copco core bits range from a Series 1 bit for the softest application to Series 10 bit for the hardest appli- cation. The numbers correspond to the different rock groups by hardness, and as a general rule, the harder the formation, the higher the series number required. However, other factors bear on the choice of bit, most important of which are the characteristics of the rock

formation, its hardness, grain size, abra- siveness, competence, and whether the strata is fractured or changing.

The lift and feed force of the drill-ing rig, together with its rotation speed and chuck and rod holding capacity are other factors. Some rigs have better controls than others, and this must be taken into account. Smooth control of feed force, and accurate control of water flushing and rotation are key factors, along with the driller’s technique.

A variety of core bit types is avai-lable based on the diamond cutting ele-ments used in their construction. The impregnated diamond core bit is most popular, followed by surface set dia- mond bits, tungsten carbide and poly- crystalline diamond composite bits.

Impregnated diamond bits should generally be used with a peripheral speed of 2-5 m/sec, depending on rock condi-tion and machine capacity.

Driller checking outside diameter of an Excore core drilling bit.

Crucial operation Drilling with a core bit is intro-duced at an advanced stage of the exploration operation, by which time substantial resources have already been spent. The quality and continuity of the captured core is crucial in the assessment of a potential mine, making the core bit a key component of a core drilling rig. Core bit selection is based on the size and depth of hole and the hardness of the rock, taking into account the rig capa-city and condition, the flushing medium, and the skills of the driller. To ensure the correct core bit, the drilling contractor needs a reliable bit supplier with the right hands-on experience to advise the best solution for every condition. Atlas Copco manufactures the entire range of core drilling tools, and will recommend and supply the type and designation most suited to the application.

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impregnated diamond core bitsIn most geological formations, impreg-nated bits are more economical to use than surface set bits as they provide ad- ditional benefits: greater resistance to wear in most formations, (particularly in hard and fractured formations), less sensitive to abuse, rough handling and improper use. Synthetic diamonds are used in the manufacture of Atlas Copco impregnated bits, with some bits using natural diamonds as gauge stones. The consistency of quality, shape, granular size, and strength make synthetic dia-monds superior to natural stones.

Impregnated diamond drill bits are designed to perform as grinders. Dia-monds are embedded in an infiltrated or sintered matrix, which erodes away at the same rate as the diamonds become worn and rounded. Thus new sharp dia- monds are exposed to continue cutting through the rock. The combination of diamonds and matrix determine the bit performance, and the simultaneous ero- sion of the matrix and the diamonds makes the bit self-sharpening.

The ideal combination of optimal penetration rate and wear resistance is matched to achieve the ultimate in drilling economy.

The diamonds are carefully selected by quality and size for the application.Through advanced manufacturing tech-nology an extensive range of drilling requirements can be satisfied. Conti- nuous control at each step in the manu-facturing process ensures that all bits are of identical high quality. This con-sistent high quality means more drill metres per bit. Impregnated diamond bits are the bit most commonly used in exploration drilling, and are particularly recommended in the hard to extremely hard formations of rock groups 6-10. Productivity has constantly improved due to intensive research and develop-ment, which has introduced new gene-rations of synthetic diamonds, metal alloy and improved production pro-cesses. As a result, impregnated bits can be used in almost all applications except clay, chalk and other unconsoli- dated formations.

The impregnated bit matrix is avail-able in a Series 1 through to Series 10

according to rock hardness. Extended channel f lushing (ECF), channel flushing (CF), and face discharge (FD) waterways can be selected, along with Torpedo “V” and JET crown profiles for competent formations. Atlas Copco manufactures core bits in 10, 13 and 16 mm crown heights. In terms of drilling parameters, weight on bit and rate of penetration have to be taken into ac- count, as do fluid volume, and rotation speed. The revolution per rate of pene-tration is normally in the range of 150-250 rev/in (RPI) or 60-100 rev/cm (RPC).

Surface set diamond bits

Surface set diamond bits can be used to drill in soft to medium hard sedimen-tary formations, but in hard rock im-pregnated diamond bits are normally more cost effective. Surface set bits are designed to utilize specific diamond size and quality according to the appli- cation, they are available in step and semi-round crown profiles, with a choice of CF waterways for consolidated rock or FD waterways for use with triple tube core barrels to avoid core washing out in soft formations. Step profile is nor- mally used for standard and thick kerf wire line bits and is suitable in almost all kinds of formations, where they offer good penetration rate and stability. Semiround profile is used for conven-tional and thin kerf wire line bits.

Atlas Copco surface set bits are manufactured to the highest standards in the industry, for the ultimate in drilling performance. They employ a hard type of matrix for all formations, and use selected and processed diamonds with a highly polished surface. These stones have a high impact resistance, and have been developed from many years of practical field experience. If the for-mation is soft a larger stone is utilized which results in fewer sones per carat. Harder formations require smaller sto- nes. The setting patterns are important to the long service life, high penetration rate, and adaptability to changing for-mations that characterize this type of bit.

Atlas Copco uses best quality pro- cessed N, S and P diamonds suitable for hard to soft formations. Most common

Jet

Extended Channel Flushing

Torpedo "V"

Face Discharge

Diamond Surface Set (SS)

Poly Crystalline Diamond Composite (PDC)

Tungsten Carbide Insert (TCI)

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quality is S, which is a natural, selected-, processed diamond, suitable for almost all applications. The size of diamonds, or stones per carat, is important because the harder the rock, the smaller the stones.

Tungsten carbide (TC) bitsTC core bits are used for drilling in non-consolidated formations and in overburden, and for cleaning drill holes. They are used for soil investi- gations and geotechnical drilling, and can also be used for mineral exploration for coring in softer rock formations.

Atlas Copco manufactures two diffe-rent types of bits with octagonal tungsten carbide inserts. Another type of tung-sten carbide bit with more cutting edges than standard TC bits is Corborit,

recommended in medium to medium-hard sedimentary formations.

All TC bits can be used in clean-out operations, such as for the removal of steel fragments from a drill hole.

Poly-crystalline diamond composite bits (PDC)PDC bits are an alternative to TC bits and surface set diamond bits, when drilling in non-consolidated and me-dium hard rock formations such as salt, potash, limestone, and clay stone with no crystalline or chert or similar intrusions.

Atlas Copco offers two types of PDC bits known as Diapax and Tripax. Diapax bits have brazed round PDC inserts, while Tripax bits have brazed cubic or triangular PDC inserts embedded

in the matrix and are recommended for harder sedimentary formations.

Reaming shells

A reaming shell should always be used in a coring system. It is a core barrel component, which joins the bit to the core barrel outer tube. The outside sur- face of the reaming shell is set with dia- monds to a specified diameter, normally larger than the bit diameter. This pro-vides a constant hole diameter inde-pendent of bit wear, and accommodates changing the bit without getting stuck in the hole. They also serve as a stabi-lizer, reducing vibration and prolonging the life of the bit.

Reaming shells are designed with a tapered leading edge to ream the hole. Well designed waterways, reinforced with PDC pins, facilitate effective flu-shing and contribute to long service life and good drilling economy for both reaming shells and drill bits.

For some core barrel systems there are optional reaming shells, longer than the standard, designed with two or three diamond set gauge rings. The longer reaming shells have to be used together with an optional extension sleeve for the inner tube. Double and triple ring reaming shells are used to improve hole deviation problems.

Impregnated reaming shells full hole profile are also available, when added stability is required.

Casing and rod shoes are manufac-tured to handle a broad range of con- ditions, from unconsolidated over- burden to broken, abrasive formations. Impregnated standard and heavy duty casing shoes as well as surface set casing shoes are available, rod shoes are available only in an impregnated design.

Summary

To maximize drilling efficiency, choose the right drill bit and utilize sound drill-ing practices. There is no substitute for testing the system at site, because all sites are different, all formations are different, and all clients’ requirements are different.

gerry Black

Atlas Copco representative discussing diamond tool selection with driller.

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Vital information

Recovered core samples are used to extract vital information where chips or other data gathering techniques do not provide an elevated level of confi-dence required to make decisions, be they related to mineralization or ground

mechanics. The quality of recovered core samples is of paramount impor-tance, and is influenced by the person-nel, capital and support equipment, diamond products, tools and accesso-ries used in given ground conditions.

In The Hole (ITH) tools represent only a small component of total project cost, but their selection and use are hugely significant to the outcome and overall success of a drilling project. Understanding the end user, his goals, and in particular his application, influ-ences how efficient coring and com-mercial solutions are developed and implemented.

Core recovery

Core can be generally defined as a volu-metric cylinder of material, created by the advancement of a rotating hollow centred diamond drill bit through an

in-situ formation, and subsequently removed.

Core recovery is a quantifiable mea-surement defined as the total linear amount of physical core sample extracted over the total linear advance in a bore- hole, expressed as a percentage. Reco- very is often measured against a section of advance, typically in the target zone and/or for the entire borehole.CR (%) = Length of core X 100

Length of advanceThe core being created is encapsu-

lated within, and subsequently extract-ed by, a retrievable sampling device called a core barrel. The core barrel is a mechanically designed device consist-ing of many interconnected engineered components. It is connected to a con-sumable core drilling bit, typically made with synthetic diamonds, which is the core cutting tool. As the drill bit penetrates through the material, it

Efficient Team: Geologist, Driller, Atlas Copco representative.

efficient core recovery

Core in the boxThe end users of exploration core drilling products are generally in the business of, and compensated for, providing representative and quality physical core samples to their customers, so nobody wins without “putting core in the box”. Core drilling is typically carried out either by contracted drilling com-panies, or directly by some mining houses, consulting companies or governmental bodies who have their own drilling departments.

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creates a core in its wake, entering the core barrel until it’s recipient tube is full, or the core’s entry is impeded, at which time the sample recipient tube is removed, emptied of its core, replaced and drilling resumed.

Drilling diameters

A drilling application comprises the borehole starting point, or collar, the target and the path in between. Bore- holes ranging from 48 mm to 146 mm- diameter, and depths of 3 m to 3 000 m share the following: diamond core drilling rig; flushing circuit; drill rod string; core barrel; and diamond tools. Selecting which diameter to drill for a given application is dependent on a variety of factors, most of which are not economic drivers and are beyond the scope of this basic overview, but capital and tools must be adequately sized and suited for each other and the objective to yield efficient recovery. As a general rule: the larger the core diameter, the better the core recovery.

Core drilling rigs come in many shapes and sizes. The rig, properly an-chored at the borehole collar, primarily needs to transmit rotation, thrust and pullback forces. As a general rule: the smoother the transmission of rotational force, the better the core recovery.

Fluid flushing

The fluid flushing circuit can vary signi-ficantly, but typically consists of one or more pumps, the fluid media itself, the drill rod string, the available borehole annular area and the peripheral acces-sories for controlling delivery, treatment and handling. Fluid is primarily required to cool and flush the cuttings from the advancing diamond core bit, and evacu-ate them from the borehole. The flushing medium can be clear water, or include additives or muds to condition borehole integrity and complete the circuit. As a general rule, with deteriorating ground conditions, focus on the flushing circuit to improve core recovery.

Drill rods

Drill rods play an important role in effi- cient core recovery. Their tool joints are

Drill rod

Conventional

Reaming shell

Bit

Core sample

Core barrel

Drill rod

Casing shoe

Flushing circulating

Drill rod

Casing tube

Bit

Core sample

Wireline

Drill rod

Core barrel

Reaming shell

Fig 1. Typical application.

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leak proof, permitting the f lushing medium to efficiently travel over great distances within the string to discharge through the face of the bit under remo- tely controlled volumes and pressures. Connected to the drilling rig, a straight rod string combined with smooth rota-tion and borehole conditioning will turn vibration free in the hole while trans- mitting the feed pressure to the cutting tool. As a general rule: proper care and handling of rods and a vibration free rotation are key to improved core recovery.

Core barrel

The core barrel is most critical to effi-cient core recovery. As a mechanically engineered device consisting of dozens of inexpensive individually intercon-nected and interdependent components, predictive and preventative mainte-nance is the easiest way to maximize recovery.

The core barrel is sandwiched be-tween the drill rods and the diamond bit. (see Fig 1) Whether conventional or wireline, the design will typically be configured as a double tube system con- sisting of an outer tube and inner tube. Triple tube systems using a split inner tube are common in broken ground.

While the outer tube rotates with the drill rod, the inner tube is meant to remain stationary during advance-ment though the in situ material. As a general rule: to improve core recovery, ensure that components are serviced and bearings regularly greased.

Core lifterThe drilling fluid circuit operates with-in the available annular area provided. More specifically, after travelling through the drill rods, the fluid enters the core barrel. There it is channelled between the inner and outer tubes, exiting via the throat of the diamond bit, and back out between the outer tube and borehole wall to the collar (see Fig 2).

At the bit end of the inner tube, core lifter case adjustment and core lifter selection are of great importance. The core lifter case needs to be placed close enough to the throat of the bit to allow for efficient core breakage, but The objective is 'core in the box'.

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its adjustment gap should not create an undesirable increase in fluid pressure and/or sample washing from the drill-ing fluid. By design, the tapered core lifter slides along the inside of the core lifter case, wedging and securing itself onto the core during core recovery and breaking. As a general rule: to improve core recovery, choose an optional fluted core lifter in difficult ground.

Core breaking

During core breaking, the drill string is raised slowly. The spring-loaded

inner tube assembly, by virtue of the core being firmly wedged by the lifter, remains stationary until the bit throat adjustment gap is closed.

At this point, the core lifter case nests into the bit, transferring the substantial lifting force from the inner tube to the drill string until the core breaks away. As a general rule: the adjustment gap should never exceed the available com-pression spring travel to improve core recovery.

In broken or friable ground, the flu- shing medium’s pathway can wash away some of the sample before it makes its

way into the inner tube with consequen-tial effect on measurable recovery.

In these poorer ground conditions the core barrel can be configured to accept a third ‘split’ inner tube. The split tube is located within the regular inner tube and uses core lifter cases and diamond bits designed to direct the drilling fluid though the bit blank instead of though the bit throat, preventing sample wash- ing (see Fig 2). As a general rule: choose the largest triple tube system possible in bad ground to improve core recovery.

A core sample will enter the inner tube until the tube is filled, or the sample is impeded, or "blocked", from entering the tube, usually because of a fracture in the sample. When this happens, continuing to advance the drill string will likely result in grinding and degradation of the desired core sample. As a general rule: avoid deformations, damaging blows and mishandling to the inner tube in order to improve core recovery.

Diamond tools

The diamond tools are the business end of the string, and the bit, in particular, is a metallurgical marvel. The bit cuts through the material that makes its way into the core barrel.

Crown profile, flushing, and gauge design characteristics react differently with changes to rotation, thrust and flu- shing parameters. As a general rule: to improve core recovery, choose bit de-signs that protect ID run out, and that minimize back-pressure and sample washing.

The fundamentals for diamond core drilling have not greatly changed since 1887, when Per Anton Craelius started in the business. We still push, turn, cool, flush, cut and collect.

However, advances by Atlas Copco in tooling and equipment have conti-nuously improved the efficiency of core recovery.

Peter Balen

Solid ground Broken ground

Flushingmedium

Reaming shell

Inner tube

Split tube

Stop ring

Core lifter case

Gap clearance

Minimal clearance

Bit

Sample

Core lifter

Double tube Triple tube

Fig 2. Bit /ground interface.

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Three aspects

Three different aspects of these ma-chines are important: drilling; rod hand- ling; and transportation and setup.

Drilling: for the driller to have full control of the drill process, the rig needs to be equipped with variable rotation speed and variable feed or hold back force. It is crucial to control these parameters, and the flow and pressure of the flush water, in order to provide a good working environment for the drill bit and produce the best core.

Rod handling: when changing the drill bit for wire line drilling, and for core recovery during conventional drilling, the drill rods have to be pulled out of the hole. This is very hard and time con- suming work, during which great atten-tion has to be paid to safety. Over the years, in-hole equipment has improved significantly, and drill bits are giving much longer life. At the same time, drill rig performance has improved through development.

Transportation and setup: for move-ment between different drilling areas the rig can be truck mounted, or a truck may be used for towing or carrying pur- poses. Across poor terrain, rigs can be

air transported, usually by helicopter. Movement between individual drill holes can sometimes be carried out manu-ally. Setup for surface rigs is typically between 90 to 45 degrees, with most holes being drilled on some angle. Straight vertical holes are not so com-mon, with a few regional exceptions.

Mechanical rigs

Mechanical rigs are still manufactured, though the numbers are decreasing from year to year. The feed system on these rigs employs hydraulic cylinders, while all other functions are mechanical.

Mechanical core drilling rigs are not very efficient, and their operation in-volves a lot of manual handling. On the other hand they are fairly easy to main-tain, so are useful in remote locations.

The drill rig components are: diesel engine with a clutch and 4 to 5 step gear-box; rotation spindle with a hydraulic

chuck; hydraulic feed cylinders; hy-draulic system; main winch; wire-line winch; feed frame; and mast.

The rotation force is transmitted from the diesel engine to the rotation spindle via the 4 to 5 step gearbox, a straight cut gear, and a 90 degree angle gear. A pair of hydraulic cylinders mounted on the rotation spindle provides feed force, and rod handling is carried out with the help of the main winch, using the mast and a separate rod clamp.

Drilling

On mechanical rigs the driller has li- mited control of the drilling process, especially the rotation speed. In the ab- sence of variable speed control, he uses the gear ratios of the gearbox and the variable revs of the diesel engine, both of which also change the available torque. The straight cut gear is equipped with a high and low setting, which will

LJ Huges' Christensen CT14 surface core drilling rig drilling in the coal fields of West Verginia.

hydraulic and mechanical surface drill rigs Principles and trendsCore drilling rigs are designed to rotate the drill string, while pro-viding pressure, to produce the core. In the core drilling industry, as in general construction, there is a clear development trend to-wards fully hydraulic rigs rather than the older mechanical rigs. The core drilling rig population can be divided according to whether they work on surface or under-ground. Most mechanical rigs are currently employed as surface ma-chines. This section describes the general principles for mechanical and hydraulic surface exploration rigs.

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increase the available spindle speed, but is not sufficient for effective core drill-ing. The feed and lift force have vari-able control, and most rigs are equipped with some kind of compensation system for the weight of the drill string.

The feed cylinders have very short stroke length compared to modern core drilling rigs. Short stroke involves fre-quent re-gripping with the chuck, slow-ing drilling and increasing the risk of core blockage. This means lower core recovery and increased wear on the drill bit.

Rod handling

On mechanical rigs rod handling is very heavy and slow work. A wire rope connected to a lifting plug is threaded on to the drill string, which is then lif-ted from the hole with the help of the main winch. The winch is driven by the diesel engine through a planetary gear equipped with brakes.

All the making and breaking of drill rod joints is carried out using a pair of pipe wrenches, while a separate rod clamp holds the drill string and pre-vents it from falling down in the hole.

The drill pipes are stored in a rod rack in the mast, or laid horizontally on a rod tray in front of the rig.

The reverse operation is used for lo-wering the drill string.

Handling of the inner tube while drilling with a wire line system is done with the help of a separate wire line winch, which is often slower than on a hydraulic drill rig.

Transport and setup

Mechanical drill rigs are normally mounted on a skid. They are heavy, despite their comparatively low capacity. However, the individual components are easy to take apart and reassemble, which is useful for movement by heli-copter. Using the main winch and the wire, the rig can slowly pull itself into the drilling position.

hydraulic rigs

In surface applications, a casing pipe may be used when starting the hole in order to create a stable hole through

the topsoil. Drilling down the casing requires lower revs/min and higher tor- que than for core drilling, and a rod holder that can handle the casing pipes.

Hydraulic drill rigs designed for sur- face applications have rotation units capable of a wide speed and torque range in combination with a long feed stroke.

The main components are: mast, rotation unit, rod holder, main winch/hoist, wireline winch, frame for car-rying the mast and the mast dump arrangement, control panel, hydraulic system, power pack, and carrier. Optional equipment may include rod rack in the mast, water/mud pump and mud mixer.

On surface rigs, the mast is usually designed as a welded structure or a beam. Feed lengths start at 1.9 m, and can be up to 3.5 m on the bigger machines. The longer feed system offers less risk of core blockage, better core recovery and longer bit life. The drill angles are

commonly between 90 degrees and 45 degrees.

The long mast is in sections, or tele-scopic, so that it can be shortened for transportation. In order to get a stable drill position, the mast can slide down to the ground with the help of a mast slide cylinder/dump cylinder.

The drill head/rotation unit and rod holder/rod clamp are mounted on the mast. The rotation unit is equipped with a variable hydraulic motor connected to the spindle/chuck via a multiple step gearbox, usually with four gears. With this arrangement variable control of the rotation speed is achieved, along with lower speed and higher torque for drilling down the casing pipes. For core drilling, a high gear is used to provide higher speed needed when drilling with modern high productive diamond bits. The mid gears are used while drilling in large diameters and/or in angle holes.The rotation unit can handle P-size rods,

A Christensen CS3001 surface core drilling rig in operation in Canada.

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or at least H, which are considered to be large diameters for core drilling. The feed force is transferred to the rotation unit by feed cylinders mounted in the mast, connected either directly to the rotation bed, or through a chain feed arrangement. Direct feed is preferable, since it requires less maintenance.

A rod holder capable of handling the drill string is mounted at the bottom of the mast. If it can be brought to the side, even bigger casing dimensions can be used. The rod clamp/rod holder is clo-sed with mechanical springs, or on mo-dern rigs by gas springs, and opened hydraulically. The main hoist is used for hoisting the drill string, and its capa- city heavily influences the capability of the rig. The diesel engine in the power pack of a modern surface drill complies with emission requirements in US and Europe.

Separate oil coolers or over sized engines are options for drilling at very high altitudes, above 3 000 m ASL. Flush pumps capable of handling mud, and mud mixers, are also common options.

Drilling

The driller has full control of the drill parameters such as rotation speed, feed

pressure, lifting force, and water flow. All rigs have a system that can compen-sate for the weight of the drill string. When drilling deeper holes, the weight of the drill string is greater than the feed force, and the rig has to apply a lifting force to relieve bit pressure.

Rod handling

In surface applications, 3 m drill rods are commonly used. The machines are capable of pulling 6 m or even 9 m rods, so only every second or third joint is broken when tripping/hoisting the drill string. Time is saved by pulling longer sections of drill string. It should be noted that a 6 m NO wireline rod weighs approximately 45 kg, and an H size rod around 70 kg. The drill pipes or sections of drill pipes are stored either in a rod rack in the mast or on a tray in front of the drill rig.

Making and breaking of the rod joints is accomplished with the help of the rotation unit and the rod holder. A thread compensation system, or floating head, is needed in order not to damage the threads. Surface rigs seldom have synchronization between the rotation chuck and the rod holder. This feature is common on underground drill rigs, because they need the capacity to drill

upwards, and they lack the capacity to hold the drill string with the main winch.

Transportation and setup

Core drilling rigs are mounted on the most suitable carrier for the particular terrain. If the terrain is fairly flat, the rig may be mounted on an all-wheel drive truck. For the complete setup, a drill rod truck is needed, as well as a water truck.

The drill platform can be equipped with hydraulic jacks, enabling it to stand alone while the truck is used elsewhere.

The rig can be crawler mounted for more difficult terrain, and transported between sites by truck and low bed trailer. Smaller rigs can be mounted on a wheeled trailer for towing from hole to hole, and between sites.

For cold weather conditions, part of the rig can be enclosed in a container, or the complete rig, including the mast, can by covered by a tent.

If vehicles cannot traverse the ter-rain to the drilling site and everything has to be carried by helicopter, the rig has to be both lightweight and easily disassembled.

Mechanical vs hydraulic rigsWith today’s demands for high produc-tivity, safer operations, and less work intensive, more versatile rigs, it is fair to say that the current transition from mechanical rigs to the more modern hydraulic rigs is a very stable trend, and will result in reducing numbers of mechanical rigs.

For very special applications, such as operations in remote areas, specialized mechanical rigs will still have to be considered, but for the vast majority of ap-plications the hydraulic drill rig will take over.

lars gellerhed

A Christensen CS4001 surface core drilling rig mounted on crawler during on-site transportation.

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increased revenue

There are two ways of increasing reve-nue on an exploration drill rig. Firstly, if availability is maximized, the opportuni-ties to put core in the box are increased. The cost of lead time and breakdowns should always be taken into the avail-ability calculation.

Secondly, if service costs increase due to the age of the rig, profitability is decreased. The service cost is normally related to the age of the rig. For a new rig, the service costs are generally lower than for a comparable 10 year old rig, not only due to lifetime of components but also because operators tend to take better care of new equipment. The capi-tal cost of a new rig is money well spent if the cost of service decreases dramati-cally compared with its predecessor.

The most important part of the ba-lance is to keep the total costs low. Moni- toring service and maintenance in a more professional way, using a service pro-gram adjusted to the specific equipment, will result in lower costs. Of course, ma- jor factors in the equation are the level

of training of the operator, overall care of the equipment, and the owner’s atti-tude to maintenance.

Care program

A well adjusted service and preventive maintenance program will ensure that your equipment is looked after in the best possible way. The care program has been developed to match the high availability expectation of our custo-mers. The program doesn’t ensure a

certain percentage of rig availability, but the setup of the program will secure its maintenance and productivity.

Care is the common name through-out the CMT business area for a tangible and simple service product for our capital equipment. It consists of three main pillars, but can be extended with more pillars depending on customer or product.

The three main pillars are: scheduled services in which we visit the machine every 250 or 500 hours and change

A Service engineer from Atlas Copco visits a drill site during a Christensen Care program to check the rig on a recommended interval.

keep the rig and business running lifetime return on investmentEvery business decision is based on the return on investment, re-gardless of whether the customer is purchasing a single machine or a whole fleet of drill rigs. The chal-lenge is to maximize the return on investment in every decision made, day after day. Atlas Copco always recommends what is best for individual customers, based on years of experience striving to gain the most economic and efficient performance on thousands of rigs in the full range of environments, worldwide. Consistently we have found that rigs with Atlas Copco service contracts yield the highest return on investment, both in daily running costs and in residual value. There simply is no better service than that performed by a trained Atlas Copco Service technician.

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filters and oils; inspection protocols whereby we carry out inspections ac-cording to a standard list; and extended warranty where we offer extended war- ranty up to 5 000 hours, or three years, on selected parts.

The extended warranty is for pro-ducts up to one year old, or 1 000 hours. Of course, the care program can be used for older rigs, but without the extended warranty option.

Other pillars in a care program can be: satellite monitoring system on sur- face rigs; application knowledge to op- timize drilling with our Service tech-nician evaluating the overall drilling operation; software upgrades.

During the care program, Atlas Copco will visit the rig at the recommended intervals, increasing the mean time be- tween failures on many parts. A com-plete and current service book also se- cures the resale value of the equipment, in much the same way as for private cars.

When using our care program you will benefit from correct service and genuine spare parts. Timely delivery of the correct parts ensures quality and availability.

Comparison between atlas Copco care program and normal/average in-house serviceThe calculation is based on experience from a number of customers during the last 5 years working in various kinds of environments.

Protecting the investment

Keeping the rig running is not only about having high availability and qual-ity assured production. Atlas Copco Service will also protect your invest-ment, with less downtime due to the better performance of genuine spare parts and the professional services of trained engineers and technicians. Atlas Copco will reduce your total cost of ownership, protecting your investment and your overall business.

anders Björk

input data of rig

Financial

Purchase price* 2 000 000

Depreciation time (number of years) 7

Residual value 300 000

Interest 5%

Insurance/tax cost/year 10 000

availability

Total workdays/year 220

Number of shifts (number/workday) 2

Length of shifts (h) 8

Standstill due to misc reasons** (days) 20

Mechanical availability*** 85%

effective operational hours 2400

* Total price including rig, Power unit and Trido. ** Change of location, set-up time, lack of electricity, fuel, water or ITH. *** Standstills due to brake-downs or service. All costs in the tables (above and below) are specified in SEK.

Outdata without Care program

Fixed costs Meter

Depreciation 33.73

Interest 13.89

Insurance/tax 1.39

Operating costs

Energy 60.00

Water 25.00

Labour 125.00

Bits 50.00

ITH 95.69

Spare parts 33.33

PM/Service 30.00

Unplanned service 60.83

Total cost 528.90

Metres per year 7 200.00

income/metre core 600.00

Profit as % of income per meter

Outdata with Care program

Fixed costs Meter

Depreciation 29.76

Interest 12.25

Insurance/tax 1.23

Operating costs

Energy 60.00

Water 25.00

Labour 125.00

Bits 50.00

ITH 84.90

Spare parts 33.33

PM/Service 30.00

Unplanned service 18.38

Total cost 469.90

Metres per year 8 160.00

income/metre core 600.00

Profit as % of income per meter

Cost/meter coreProfit/meter core

Cost/meter coreProfit/meter core

Note: Figures serve as an example from existing customers and Atlas Copco can not be held responsible if the outcome is not according to the above figures. We can only act together with our customers with a goal to achieve the above, where the CARE program is the tool we use.

50 exploration drilling

long experience

Based in Kitwe, the strategic hub of the Zambian mining industry, Blu Rock Mining Services has long and specific experience in the deep drilling sector. The founder, Polish-born Kris Jedrzejczyk, has worked in drilling and shaft sinking for nearly 30 years. Prior to starting Blu Rock, Kris worked for Mpelembe Drilling for 22 years, and was a member of the management buy- out team that took over the operation from Zambia Consolidated Copper Mines (ZCCM) in 1997. On contract drilling jobs, he adopted a hands-on approach, taking responsibility for pro- ject planning, contract proposal writing, and negotiations with clients at all the main Zambian mines, and moni-toring the execution of the projects. Consequently, he got to know most of the country’s senior mining executives, engineers and experienced drill ope-rators, earning their respect and trust.

equipment leasing

Through managing the Mpelembe drilling equipment fleet, and also as a

director of the specialist underground diamond drilling company, Redrilza Ltd, Kris Jedrzejczyk established a construc- tive and professional relationship with Atlas Copco. This was a considerable help when he decided to plan the esta- blishment of Blu Rock Mining Services, because Atlas Copco was in a position

to provide favourable credit and equip-ment leasing terms.

This enabled the company to get up and running with five new Atlas Copco rigs. The chosen fleet comprised two Christensen CS14 core drilling rigs ca- pable of drilling to 1 540 m with B size wireline, and three Christensen CS 1000

Exploration drilling with a CS1000 core drill rig at Muliashi, Luanshya Mines.

luanShya, ZaMBia

Confirming the future of Zambian coppernew playerA recent addition to the ranks of Zambian deep drilling firms is Blu Rock Mining Services, formed in March, 2007 and already proud owners of five Atlas Copco core drilling rigs. After many years of depletion, drilling for replacement of copper ore reserves is essential to the long term future of the local mining industry, and is currently carrying a high priority. Offering technically-advanced equipment for drilling the accurate holes required for what are very care-fully monitored geotechnical and exploration projects seems to have found a niche in the market on the Zambian Copperbelt, and business is booming for Blu Rock and its affiliates.

COnFiRMing The FuTuRe OF ZaMBian COPPeR

exploration drilling 51

P4 rigs for conventional or wireline co- ring down to 1 030 m with B size wireline. The rigs were delivered and commissioned over a period from December, 2006 through to September, 2007.

They are currently working under contract for two of the regions’ new generation of companies, Konkola Copper Mines (KCM) and Luanshya Copper Mines (LCM). The contracts involve exploration, geometallurgical and geotechnical drilling within two of the Copperbelt’s long-established mining areas, Chingola-Chililabombwe in the west, and Luanshya towards the eastern end.

long-term goal

KCM has employed one CS14 and two CS 1000 rigs in the Chingola area, where they had drilled a total of 10 000 m by the end of June, 2008, with the overall aim of confirming future copper and cobalt resources.

The remaining two rigs, a CS14 and a CS 1000, are drilling for LCM on the Muliashi and Mashiba projects near Luanshya to provide information for the detailed design of new surface mining and processing facilities.

The CS14, in particular, is working at the Fitwaola open pit to monitor the dip and grade of the orebody. The pit is in operation on a daily basis, and so, in order to avoid vibration damage to the drill string it is necessary to pull the rods each time production blasting is undertaken.

The trailer mounted Christensen CS14 is equipped with a 3.5 m feed with main hoist capacity of 80 kN and 138 kN hydraulic feed cylinder. Power is supplied by a Tier 3 Cummins diesel engine rated at 153 kW, or 208 hp.

At Kakosa, north of Chingola in the direction of Chililabombwe, a CS 1000 is exploration drilling to an average depth of 200 m to find a continuation of the Chingola orebody. The Christensen CS 1000 is a lightweight basic rig of simple design that can be flown to site. It has 40 kN hoist lifting capacity and 90 kN pull from the 1.83 m stroke feed system. Power is from a Cummins 4 cylinder 86.5 kW diesel engine. The third rig is drilling a limited number

of holes to assess lime resources that KCM might be able to use. This rig may start core drilling waste dumps in the area, to check for residual metal content, following up on a reverse cir-culation drilling programme that KCM has started.

Using the new fleet of Atlas Copco rigs has paid off, as they drilled 2 000 m in the first two months of the con-tract, a much higher rate than previ-ously achieved.

luanshya improvements

The LCM management team, headed by CEO Derek Webbstock, has already invested USD 50 million in upgrading both the Baluba mine and the concen-trator, which can now process 10 000 t daily. Baluba has been mining 5 000 t/day, yielding 21 000 t/y of copper, and is expected to produce 24 000 t in 2007.

Now LCM intends to invest a further USD 50 million at Baluba, in particular to modernize the hoisting shaft, and USD 354 million to develop a new open pit mine at Muliashi, initially extracting oxide ore reserves. Baluba should then be able to increase mine production to 6 000 t/day while Muliashi is presently expected to contribute 60 000 t/y copper and 1 500 t/y cobalt at full rate output. Phase 1 engineering has started at the Muliashi project, and is scheduled

for completion in the first quarter of 2009.

LCM, which presently employs 2 400 people, expects to employ a fur-ther 1 000 people during construction, although only 400 will be required for the operational phase. Meanwhile, the company has started a feasibility study for mining the Mashiba sulphide ore-body, which could add a further 6 000 t/y to LCM copper output.

Blu Rock’s rigs were contracted to drill a total of 15 000 m, of which 9 000 m had to be completed by April, 2008. The CS14 drilled holes ranging from 20-70 m for the Mashiba project, coring for process metallurgy test work needed for the feasibility study.

Meantime, one of the CS1000 rigs was used to recover 48 mm core from a depth of 450 m to provide geometallur-gical information for the mine planners and process engineers working on the Muliashi project.

Other recently won contracts seem to confirm Blu Rock’s winning formula.

acknowledgements

Atlas Copco is very grateful to Kris Jedrzejczyk and his company Blu Rock for assistance received in the prepa- ration of this article, which first appeared in Atlas Copco Mining & Construction magazine 1-2008.

Reviewing the progress: From left: Luciano Chikabo, Foreman, Blu Rock, John Kakumbi, Sales Manager, Atlas Copco and Kris Jedrzejczyk, Managing Director, Blu Rock.

52 exploration drilling

Five year plan

From its head office in Witbank, Zaai-man Exploration Drilling commenced a five-year plan in 2006 to replace all of their existing conventional type rigs with Christensen CS rigs.

Currently Zaaiman Exploration Drilling operates 2 x CS 1500, 9 x CS14 and 4 x CS10 machines. On order are a further 2 x CT14 and 2 x CS 3001 that will be in operation by January, 2009. Directors Thinus and Rudi Zaaiman state that changing over to the CS machines has increased production substantially. Drilled metres increased on average from 800 to 1 200 m/machine/ month.

Platinum explorationThe trend in South Africa in platinum exploration is towards deeper holes,

resulting in more requests for bigger drills. For this reason Zaaiman ordered another two CS 3001 drills.

In platinum, where the contractor drills BQ-size, bit life almost doubled, from an average of 130 m to 220 m. As a result of the efficiency of the Christensen CS rigs, as demonstrated in increased production and very little downtime, a recent large platinum exploration project in the Northern Province was finished six months ahead of schedule.

The CS 3001 is built on a well-proven concept that is continuously upgraded. Designed for truck mounting, it is equipped with four hydraulic levelling jacks. With a main hoist single line pull of 139 kN and feed stroke of 3.35 m, it can drill B-size to 2 300 m and N-size to 1 830 m, handling 6 m rods with ease. Power is delivered from a 212 kW Cummins Tier 3 diesel engine with a

WiTBank, SOuTh aFRiCa

atlas Copco exploration rigs prove reserves

Powerfully efficientThe current range of explora-tion drill rigs from Atlas Copco Christensen offers great benefits to contractors in the industry. This is evident in South Africa, where Zaaiman Exploration Drilling is operating 35 rigs in mainly coal and platinum explo-ration. For Zaaiman, Christensen rigs are powerful, with enough torque to drill deep and with high productivity. Speeds range from low to high to handle diamond drilling, and long masts pull 6 m to 9 m rods. Importantly, com-plete units are supplied, including rig feed, control panel, main hoist and powerpack. As an added bonus all rigs are equipped to make and break the drill string with the rig, eliminating manual making/breaking with pipe wrenches, improving safety and productivity.

CS 15000 in operation at Polokwane.

CRaeliuS exPlORaTiOn RigS PROVe ReSeRVeS

exploration drilling 53

large 950 litre fuel tank. The standard rig is equipped with hydraulic P-size rod clamp and hydraulic mud mixer.

Reduced maintenance

Atlas Copco Christensen rigs are built on the time-honoured concept of easy operation, simple and durable technology, and high capacity, and are much more in line with safety re-quirements and standards than their counterparts. Easy, timesaving setup, improved power, ergonomics and safety and increased productivity all contri-bute to the market acceptance of the new generation.

The CS rigs have certainly proved their worth for Zaaiman Exploration, where maintenance costs dropped by two thirds because of less downtime and breakdowns compared to the old conventional type drills.

This type of performance, along with its legendary Aftermarket support, have led Atlas Copco to its position as preferred supplier of all exploration drilling equipment and consumables to Zaaiman Exploration Drilling. This is a relationship of many years standing, and is certainly one that will continue in the future.

Coal benchmark

Because of the built-in safety features, the Christensen CS range of rigs are being used as the benchmark for pro-duction and safety standards in coal exploration in South Africa by major companies such as BHP Billiton, Anglo and Total Coal.

With safety being such a big factor in the industry, the CS range has kept on developing, and now sets the trend for other to follow.

acknowledgements

Atlas Copco is grateful to Drill Africa and Kyran Casteel for their assistance with the production of this article.

One of the first CS 1500 machines drilling for platinum.

54 exploration drilling

Challenging ground conditionsDrillcorp is a South African based drilling contractor, with operations in several countries in Southern Africa, as well as Brazil. The fleet includes more than 40 drill rigs, which are moved between sites after finished contracts. The operators and supervisors always have to ensure that contracts are final-ized in time, as a new drill site is wait-ing for them somewhere else.

Orkney is a small town 250 km west of Johannesburg, and is close to a gold-field with several mines. The goldfield Drillcorp operated on has a well known ore, with the first exploratory holes having been drilled as far back as the 1930s.

The mine had been operated since 1991, but was closed during a change of ownership to explore and evaluate the prospects of further development. In 2009, Drillcorp was awarded a five-month contract for 20,000 m core drill-ing to define the ore values.

To meet the timeline of the contract, Drillcorp had been running two drill rigs on separate locations to define the

values of the ore 400-500 m below sur-face datum. Some 46 holes were to be drilled, using mother holes drilled close to 500 m. At around 350-400 m depth wedges were placed, and deviated holes were drilled out in steps of approxi-mately 10 cm from the mother hole to define the ore around the centre.

Drillcorp deployed drill bits similar to those used at earlier drill sites, but soon discovered that the ground at the mine posed some challenges. The bits

did not cut the hard rock as expected and, when more pressure was applied it simply lifted the drill rig instead of cutting faster. In the toughest spots, the drill bits did not cut, but merely polished the bit.

In addition, the ground was frac-tured, and complicated to drill without getting stuck. By the time that 10,000 m had been drilled, Drillcorp was man-aging about 30 m/shift with a bit life of 60-70 m. At that level of performance,

Drillcorp in South Africa was one of the contractors where the Excore bit was tested successfully.

ORkney, SOuTh aFRiCa

excore optimizes performance for Drillcorp More for lessCore in the box determines explo-ration drilling company revenues and driller’s wages. Not surpris-ingly, drillers are always looking for diamond drill bits with faster penetration rates and longer service life. The efficiency of the drilling tools is often a decisive factor in maintaining productivity and profitability, even when rock conditions change. To meet these demands, Atlas Copco developed Excore as the next generation of diamond drill bits, offering superior bit life and penetration rate. Pre-launch testing of Excore was rig-orous, with thousands of metres drilled in six different countries under a wide range of conditions.

exCORe OPTiMiZeS PeRFORManCe FOR DRillCORP

exploration drilling 55

more drill rigs were needed to close the contract on time.

excellent results

At this stage, the newly-developed Excore bit from Atlas Copco was introduced on the advice of engineers at Atlas Copco Exploration Products Africa. The results were astounding on the remaining 10,000 m of drilling, on which Excore returned an average bit life of 280-300 m at a production rate of 54 m/shift. This 80% higher pene-tration rate, coupled with a more than four-fold increase in bit life, added up to a significant productivity improve-ment!

During the drilling operation, Drill-corp did not change any settings on the drill rigs, and used a variety of opera-tors with differing levels of experience to get a fair result. They found that a single Excore bit type could handle all of the formations in the Orkney area, whereas Drillcorp had previously nee-ded to stock six different bits on the shelf.

This is not only important from an inventory perspective, but also opera-tionally. As the rock conditions change, even for a few decimeters, the rods may have to be pulled to change bit type. The Excore bit could be used through-out the operation to cut through all for- mations.

After closing the contract, Drillcorp moved on to another drill site in the same region, where they knew that the rock conditions were not as challenging. They intend to try Excore again at this new site. They reason, that Excore is simpler and more flexible, and drilling will be easier.

Design and metallurgy in harmonyThe Excore drill bit technology is any- thing but a result by chance. The expe-riences from the preceding diamond bit ranges were substantial, and a global team of experts put their heads together to re engineer the bit from basics. The previously most successful bit designs were taken one step further, with changes in design specifications. Improved crown designs complimented

by new matrices achieves an optimized balance between design and metal-lurgy.

The design and composition of the Excore bit line offers the world’s explo-ration drillers new levels of produc- tivity in terms of longer bit life and higher penetration rates.

With a longer bit life, less fre-quent bit changes and rod pulling are required, allowing for more time to be spent on drilling.

The higher penetration rate means a lot more to the driller than mere pro-ductivity. When ground is difficult, and there is a risk for hole deviation or lower core sample recovery, it is possible to lower the weight on bit (WOB) and still hold a penetration rate equal or better than with other bits. With less pressure on the bit, it is easier to achieve straight holes and higher core sample recovery, while wear on the drill string is reduced. This gives a better result for the same

Drillcorp had a contract of 20 000 meters core samples, of which the last half was drilled with Excore.

exCORe OPTiMiZeS PeRFORManCe FOR DRillCORP

56 exploration drilling

Caption?

The Excore diamond bits set a new standard for production rate and bit life as it was released to the market.

exCORe OPTiMiZeS PeRFORManCe FOR DRillCORP

exploration drilling 57

operating parameters. On the other hand, when rock conditions allow the driller to push for maximum speed, Excore bits optimize the drilling rate vs WOB.

The bottom line is that Excore gives better results in a wide range of drilling conditions.

More performance with fewer bitsExcore is not only a bit of performance. It is also a bit of simplicity. Normally a variety of bits has to be stocked at site to cover all expected rock formations. Excore’s unique metallurgy and design ensures each bit type will cover a wider range of rock conditions, meaning that fewer bit types will be needed. With fewer choices, selecting the right bit is simpler. The driller does not need to have experience and knowledge of the rock conditions hundreds of metres below surface, because the Excore bits will help him in his judgment. And the logistics manager will benefit with less overall inventory.

The Excore bit range is divided into three application segments: Soft to me- dium hard, very abrasive to slightly abra-sive and very fractured to slightly broken formations (Matrix series 1-4); Medium hard to hard, abrasive to slightly abra-sive, moderately fractured to competent formations (Matrix series 5-8); and Very hard to extremely hard, slightly abrasive to non abrasive, very competent forma-tions (Matrix series 9-10).

Each Excore type is available in various crown designs like the ECF (Extended Channel Flush) for broken to competent formations, the JET profile for fast cutting in competent forma-tions, and Face Discharge design for extremely broken and triple tube appli-cations.

Combining these features with dif-ferent available crown heights, from 10-16 mm, there is an Excore bit for every formation.

acknowledgementsAtlas Copco is grateful to the management and engineers of Drillcorp South Africa for the contribution to this article.

Bit for purposeWillie Smit is Drillcorp’s site manager, with 17 years of experience of core drilling. His background, performance and attitude have earned him the title of supervisor of the year at Drillcorp in each of the past two years, emphasizing the fact that he has great pride in his worksite and equipment. Willie and his drilling crews were not satisfied when it became clear that the drilling contract could not be fulfilled in time because of inadequate bit performance.

A solution using the newly-developed Excore bit was suggested by Jimmy Erasmus, sales engineer from Atlas Copco Exploration Products Africa. As the Excore bit had not yet been released to the market, Drillcorp was offered a bit that had been part of the test program. This bit was introduced into a partly drilled hole which had 250 m left to drill.

Drillcorp normally would expect to change bit at least three more times for that hole, needing at least six hours to pull rods. However, the new Excore bit, completed the hole without need for replacement. Indeed, the bit still had some life left, and drilled another 52 m in the next hole. The first test showed 302 m bit life compared to the normal 60-70 m using the previous bits!

After the trial, Drillcorp ordered 20 additional Excore bits to enable the contract to be finalized on time, a great result for the company and for Willie and his team.

“This is an excellent bit, and I would recommend it to anyone”, comments Willie, adding “especially for the ground conditions we have experienced.”

Statements:“The new bit replaces six other bits needed in stock”, confirms Charl Sommers, Store supervisor and buyer for Drillcorp. “This makes our operation much more efficient.”

“We need bits for hard and soft rock, we don’t know which until we are in the formation. Says Willie Smit, site manager. “If we need to pull rods to change the bit it may be for only a few decimeters. It saves us a lot on not needing to do this.”

Table 1: a calculation shows that for a mother hole of 500 meters, time saving was:

Previous bit used Excore

Bit life 65 m 290 m

No. of bits needed 8 bits 2 bitsNo. of pulls to replace bit 7 pulls 1 pullTime to pull rods 14 hrs 2 hrs

Capacity 30 m/shift 54 m/shiftTotal time to drill 118 hrs 74 hrs

Total time per hole 132 hrs 76 hrsThis results in a time saving of 40% to drill a 500 m hole.

58 exploration drilling

Better technology

In 2007, global production of mineral gold exceeded 2 447 t, of which more

than 10% came from China. The com-bination of high price and demand in domestic and international markets has resulted in heightened interest in gold exploration. As always, speed is of the essence, and higher productivity is required, driven by improvement of drilling technology and equipment.

Recently, Guizhou Geo-mining Ex- ploration Bureau (Guizhou Bureau) employed the latest exploration drilling technology at Shuiyindong gold mine at Zhenfeng, Guizhou, where an Atlas Copco CS14 core drilling rig drilling NQ (75 mm) reached a depth of 1,411 m, record that exceeds the drill’s maxi-mum rated depth of 1 200 m.

The 176 000 sq km Guizhou pro-vince is in a plateau area comprising typical karst topography, where the basic

geologic exploration is the responsibility of the Guizhou Bureau.

Shuiyindong mine

A pair of Atlas Copco Christensen CS14 core drilling rigs are operating at Nayang section of Shuiyindong gold mine. The mine is located at the town of Zhexiang in Zhenfeng County, about 260 km away from the provincial capital Guiyang.

The rigs were bought in January, 2007 by No 112 Geo-Survey Team Exploration Company of Guizhou Bureau (Team 112) which has been responsible since 2002 for exploring the Zhexiang section. The two rigs have been generally employed on exploration drilling to depths of 700-1 400 m, and in their first year of

Close-up of CS14 core drilling rig at work.

guiZhOu, China

new record depth for CS14 core drilling rig

Mining prosperityThe mining industry in China is growing rapidly to fulfil huge demand for iron ore, coal, gold, silver and other metals. The coun-try is already a major mineral pro-ducer, and is both a consumer and a world trader of its mining pro-ducts. In Guizhou province, which is rich in gold resources, exten-sive mineral exploration drilling is underway using Atlas Copco CS14 rigs, one of which recently set a new record depth for a core drilling rig.

neW ReCORD DePTh FOR CS14 CORe DRilling Rig

exploration drilling 59

operation drilled a total of 17 holes, amounting to 15 100 m.

The orebodies in the Zhexiang section are usually at the bottom of the strata and explored using the wireline core drilling. Wireline coring is a relatively mature method of exploration in China, with high penetration rate and low la-bour input.

At Zhexiang section, Team 112 is using three drill rigs, of which two are Atlas Copco CS14 core drills and the third is a locally-designed XY-2000 drill. The CS14 displays superior speed and stability to that of the XY-2000 rig, and achieves higher productivity through proper selection of penetration parameters and techniques for deep hole drilling.

improved productivity

During the initial trial operation, both CS14 core drills achieved a maximum penetration rate of 18 m/h in HQ (95 mm) hole sections, which is 5.24 times that of the XY-2000. Their average pene-tration rate is a stunning 6.33 times greater!

During their first year of operation, the two CS14 drills achieved maximum monthly productivity respectively of 1 618 m and 1 705 m, while that of the XY-2000 drills was only 694 m. Their average monthly productivity was 1 074 m and 757 m, equating to 2.3 times and 1.6 times that of the XY-2000. Their average hourly productivity in the year was respectively 4.5 m/h and 4.9 m/h, 2.56 times and 2.83 times that of the XY-2000.

The distribution of exploration bore-holes in the mine is on a square grid measuring 160 m x 160 m, and hole quality is under strict control. The allow-able tolerance of borehole zenith angle is 2 degrees for 0-100 m and 4 degrees for 100-200 m. The rock core extraction in a hole exceeds 85%. Rectification is a must for every 100 m, and the error must not exceed one thousandth.

The two CS14 drills reached their record maximum depth of 1411 m in 42 days, operating 24 h/day, recor-ding maximum penetration of 70 m in a single 12 h shift. So far, no cores have been discarded, and there has been a very high rate of successful drilling, Collecting core samples from the inner tube.

neW ReCORD DePTh FOR CS14 CORe DRilling Rig

60 exploration drilling

Core washing at the rig shows perfect recovery.

neW ReCORD DePTh FOR CS14 CORe DRilling Rig

exploration drilling 61

with deviation controlled within the allowable tolerance.

By the end of March, 2008 CS14 No 1 had achieved a total penetration of 8 446 m and No 2 had drilled 6 432 m to average depths of 770 m and 716 m. The diameter of hole opening is 130 mm using locally produced drill pipes, the diameter of the finished hole is 75 mm, and the diameter of the rock core is over 40 mm.

The CS14 uses imported Atlas Copco drill strings, whose average service life is 8 000-9 000 m. XY-2000 drill uses home made drill strings, whose average service life is around 3 000 m.

When unstable rock or stratum condi- tions are encountered during the drilling operation, slurry or pipes are usually used to protect the hole. Any burial of the drill bit will be immediately hand-led using a reverse thread drill string.

Safety and training

A project office has been set up at the Zhexiang section, managing three drill-ing groups with one drill rig apiece. Each group comprises 12 personnel working in shifts of three people. The drill operators have a high level of enthusiasm, and are quick in installa-tion and relocation of drill rigs. The site follows standard operation procedures, with the CS14 rigs being maintained by specially assigned people.

Installation, operation and mainte-nance training has been provided by Atlas Copco to teach the operators about the drill functions, and how to improve productivity. The CS14 rig does not re- quire derrick installation, which is a great time saver. As a safety precaution, the machine is fitted with emergency stop buttons, which stop the drill immediately.

Deep impression

The CS14 has many merits including high penetration speed, good borehole quality, and a first class safety record. The bureau is satisfied with the after-market service of Atlas Copco, and praises the prompt response to prob-lems. Spare part supply is difficult to arrange in such a remote location, so it is necessary to carry an inventory of

spares in order to shorten the supply cycle.

Guizhou Bureau investigates all op- tions before importing technically ad-vanced drill rigs, and ordered ancillary equipment such as drill strings and drill tools along with the CS14. The proven performance of Atlas Copco products and aftermarket service were big influ-ences on the purchase decision, along with low noise, good hydraulic system tightness, high degree of safety, quick installation, and compactness of the CS14, being a third smaller than tradi-tional drills.

In 2007, the two Atlas Copco CS14 rigs drilled a total of over 14 000 m. The target for 2008 is 20 000 m.

Atlas Copco is now a major world supplier of ISO certified exploration drill equipment and tools, providing a com-plete range of conventional and thin-wall wireline core drill strings along with traditional steel and aluminium core drill strings. Localized production and supply in China means quicker delive-ries, and increases customer confidence in Atlas Copco products.

exploration bureau

Founded in 1957, Guizhou Geo-mining Exploration Bureau is a government institution at the provincial department level with comprehensive functions including: basic geological survey and research; mineral exploration and development; hydrological engineering; geological environment survey and evalu- ation; geological disaster survey and

prevention; and mineral rock identi-fication and testing.

In the last 50 years, the Bureau has accomplished a total mechanical core drilling of 6.6 million m and a total pit excavation of 280 000 m. It completed comprehensive survey of 180 000 sq km of land in the whole Guizhou Province and part of Tibet, and submitted many reports on mineral reserves including gold, aluminium, phosphor, lead and zinc, manganese, coal, mercury, iron, and barite.

In 2000, the Bureau established its business pattern: basic geology survey and research; mineral exploration and development; and geological engi-neering. The Bureau has made break-throughs in exploration of minerals like gold, lead and zinc, manganese and copper, and carries out vigorous cooper-ation with domestic and foreign mining companies such as Aohua Mining from Australia, APC Mining from Canada, and Zijin Mining in Fujian.

The Bureau also takes an active part in some infrastructure projects inclu-ding coal exploration to enable power transmission from west to east, and geological disaster prevention for Three Gorges.

acknowledgementsAtlas Copco is grateful to the manage-ment and engineers at Guizhou Bureau who contributed to this article, and to Caroline He of Atlas Copco (Shanghai) Trading Co for collation of the perform-ance data.

Typical CS14 core drilling site in the Guizhou region.

62 exploration drilling

Black rocks The main event that led to the creation of the integrated stainless steel ope-ration is something of a legend. During the summer of 1959, somebody reported finding “strange black rocks” in Kemi parish on the northernmost shore of the Gulf of Bothnia in Finland. These were identified as lumpy chromite, and traced back to a large stratiform deposit north of Kemi town.

However, the mineralization had a Cr2O3 content of about 26 % and a chromium to iron ratio of 1.5 to 1, both properties being substantially lower than those of any chromite ore then in use for making ferrochrome.

Even so, Outokumpu, which at that time was primarily a base metals mi- ning and smelting company, was inte- rested. The company had already em-barked on nickel production as the basis for making stainless steel, and decided to try to develop a processing system to upgrade the ore. A pilot plant was set up at Kemi in 1966 to prove the feasi-bility of upgrading the Cr2O3 content sufficiently. Both mining at Kemi, and ferrochrome production at Tornio using hydroelectric power, started in 1968.

At that time Outokumpu intended to improve the chromium to iron ratio as part of the ferrochrome smelting pro-cess, but this plan was effectively over-taken by the development in the United States of the argon-oxygen-decarburizing process for making stainless steel which can utilize low chromium to iron ferro-chrome.

Outokumpu was thus able to enter the stainless steel business, which it subse-quently expanded several times, often introducing new proprietary techno-logy that has been sold by Outokumpu Technology, and now Outotec, to other producers. The operation gained ISO 9002 quality certification in 2000.

Eventually, at the start of the 21st century, OTW became the company’s primary focus, and Kemi is now the only mine owned by Outokumpu. It now comprises the mine, ferrochrome works, steel melting shop, hot rolling mill and cold rolling plants and employs approximately 2 300 people, of whom 130 work at Kemi, assisted by about 100 contractor personnel.

The ore grade at Kemi still demands very careful mining and grade control to ensure the mineral processing plant can deliver competitive, cost-effective feed to the ferrochrome smelter. Hence there has always been a need for rather precise grade control.

Moving undergroundMine production started in 1968 on an open pit mineable part of the chromite deposit that comprised 11 ore bodies within a 4.5 km-long zone and varied from 5 m to 105 m in thickness, the average being 40 m.

The need to keep mining costs as low as possible, in what has been a high wage economy, has resulted in Kemi utili- zing advanced mining technologies for chromite extraction, probably to a greater extent than most other producers.

The first main pit to be developed continued until open pit mining ceased, but satellite pits immediately east and west of the main pit were developed and mined out in the intervening period. Open pit output reached a maximum of about 1.2 million t/y ROM ore.

Three main ore types corresponding to mill products were mined. These were fine concentrate (12-100 pm particles), upgraded lumpy type (34-36% Cr2O3)

keMi, FinlanD

grade control at kemi mineKemi mine is a crucial part of the Outokumpu stainless steel making operation at Tornio in Finland, now known as the Outokumpu Tornio Works (OTW). Equally, ac- curate grade control is crucial for the economic operation of the Kemi mining and processing sy-stem. For the grade control drilling function, the mine relies on an Atlas Copco Diamec U6 APC core drilling rig, which is drilling up to 12 km every year.

The Diamec U6 APC mounted on a crawler chassi, ready for operation.

gRaDe COnTROl aT keMi Mine

exploration drilling 63

and super upgraded lumpy (+36% Cr2O3), from which the processing plant made (and still makes) 220 000 t/y lumpy concentrate (36% Cr2O3) and 420 000 t/y metallurgical grade con-centrate at 44% Cr2O3.

Physical separation techniques are used to produce the lumpy ore and metallurgical grade fines. Ore grade control in the open pit involved wire-line diamond core drilling to determine boundaries and qualities of specific ore types. In addition, all blastholes were sampled, and only one type was produced from a specific working area because the initial process step will not work effectively with mixed ore types. In the 1990s Outokumpu planned a switch to underground mining, which involved developing the underground mine from the side of the open pit while production continued in the pit. As the output rate from the underground mine grew from 150 000 t/y in 2003, so the open pit mine was able to build

up stocks of the feed types. These were used after open pit mining ceased in December, 2005 and until underground output reached the 1.2 million t/y rate required to feed the ferrochrome smelter early in 2008.

The open pits had yielded a total of 31.15 million t of chromite ore when mining stopped.

grade control

Grade control and mineability were key factors considered in detailed under-ground mine planning for Kemi. To continue providing the data necessary for grade control from the underground operation, as well as the equally im-portant broader array of management information needed to maximize mine efficiency, Outokumpu developed an Intelligent Mine Information Technology programme. To obtain the geological data, a Diamec 264 rig for grade control and other core drilling was

deployed in 1996 for inventory drilling. The Intelligent Mine Programme pro-vided the mine and process plant with an advanced communications system to access and complement the information on Kemi’s master database. This system has been extended and upgraded more or less continuously.

Five ore bodies with a dip of 70 de-grees NW make up the 1.5 km-long ore zone that is now being mined below the main open pit. Their geometallurgical and rock mechanical characteristics vary quite widely, so planning the stoping schedule to achieve the required feed grades needs very careful attention.

The primary mining method is bench cut-and-fill, with some sublevel caving possible in parts of the mine where the blasted ore can be trucked out directly to the surface crushers. Sublevel caving provides a fall back option for maintaining the delivery of ore to the plant if the main mining operation is interrupted, for instance if

The Diamec U6 APC set up for horisontal drilling.

gRaDe COnTROl aT keMi Mine

64 exploration drilling

the hoist is out of operation. As in the open pit, the five ore bodies can still be differentiated along the ore body, which has average width of 40 m and can yield reasonably consistent ore types. However, whereas each 60 000 t ore blast in the open pit provided suffi-cient tonnage to be treated selectively at the concentrator, minimizing feed variation and maximizing process sta- bility, this is not possible with bench cut-and-fill. Designed to cope with weak hanging wall rock and very variable

fragmentation, this technique typically yields only 7 000 t/blast.

Kemi’s mine production objective is to obtain the best possible mix for the process plant that mine planning, together with historical processing data and current drilling data, can provide. Typically, four or five stopes in the five ore zones are mined at any one time, and 40-45 in a year, in order to yield appropriate feed tonnages for lumpy ore and metallurgical grade concentrate processing. The process team tries to

separate the ores for heavy medium separation and for milling between the two silos. Basic mineralogical data and process results for each ore stope are logged on a daily basis, and can be compared with daily and blast-specific production histories from the database.

Diamec u6 aPC

In August, 2006 the mine geology team decided to acquire a new core drilling rig. The choice, on price and avai-lability, was a new Diamec U6 APC Automatic Performance Control rig, rather than the equivalent U4 model. The specification selected included: the standard 1 800 mm feed frame; PU55E electric power unit with 55 kW motor and two hydraulic pumps; the A–N rotation unit with a 60 cc hydraulic motor, the optimal choice when ITH drilling at AQ size; Trido 80H hydraulic flushing water pump with a capacity of approximately 80 lit/min; 1 300 m wire line winch, mounted on the positioner arm; and APC panel.

These standard components are mounted on the tracked crawler unit option, which trams with diesel power rather than the alternative skid moun-ting, and has an extra working platform with seat for using the APC unit. The Kemi machine also has extra working lights. In addition to this set up delive-red by Atlas Copco in February, 2007, Kemi has added a cable drum at the back, has installed an internal water tank and retrofitted Atlas Copco’s RCS remote control system.

The RCS system works very well with Kemi’s W-LAN based communi-cation system, and most of the mine’s Atlas Copco units have it fitted. The new machine augmented the Diamec 264 until the older rig was sold to Suomen Malmi Oy (Smoy), a major Finnish exploration drilling contractor.

The choice of the crawler platform rather than a skid reflects the main use that Kemi makes of the Diamec, drilling relatively short holes from a stope drive to determine the ore boundaries, and then moving to another stope drive. The rig can tram at 2-3 km/h, but for long moves uses a special carrier. The crawler platform has the advantage that no dis-assembly is required before it moves,

The driller in action handling the drill rods.

The powerful rotation unit of the Diamec U6 APC.

gRaDe COnTROl aT keMi Mine

exploration drilling 65

whereas the power components must be disconnected from a skid-mounted feed frame, risking the entry of damaging particles into the equipment. The skid mount is more cost-effective for drilling long exploratory holes up to 1 000 m, which can take at least a month, so moves are infrequent.

Fast rotation

Kemi selected a fast rotation unit be-cause the rig is drilling for narrow core. However, selection of the Diamec U6 did take into account the possibility of drilling very long holes when nec-essary, and Smoy has already carried out a core drilling programme at the -475 m level, using the new machine with Kemi operators to drill 2 in holes intended to yield geomechanical infor-mation. The deepest core drilling to date has reached the -650 m level.

Since the orebody is normally 40 m- wide, the Diamec usually drills three to five holes 40–70 m-long holes sideways from the stope drive wall through to the other side of the orebody. In a few places faulting has made the ore wider, to over 100 m in some cases. Some drilling upwards into new mining levels is also underway.

Kemi’s Diamec has a 1.8 m feed and uses 3 m rods behind the core barrel. The core barrel is 48 mm-diameter, accommodating 30-32 m-diameter core. All core is analyzed by OMS-logg downhole logging, and automated microscope image analysis is used for establishing grain size distribution. Additional sludge colour information is obtained from blasthole drilling.

automatic Performance ControlKemi chose the APC hydraulic control system rather than the Pilot Hydraulic Control PHC option for a number of rea-sons. APC gives the driller freedom to empty core while the Diamec is drilling on automatic, which means the rig can be operated by only one person, rather than the usual two. It can also be used for remote control for operator safety. The Kemi operators, who previously worked with the Diamec 264 and are therefore used to the APC system,

particularly like the joystick control. However, Kemi does not presently use the performance data downloading facility because the ore is too variable for the data to be of use in subsequent operations.

Not surprisingly given the ore vari-ability, penetration rate varies from as low as 20 cm per minute but is typi-cally 30-35 cm/min, at the high end of the performance range for Diamec U6 machines. The APC is very easy for in-experienced drillers to use, but only an experienced driller can set the system parameters. The sensitivity of the APC control contributes to the excellent bit life at Kemi, which is 600-700 m with a recorded high of 900 m. Rod life has been enhanced by fitting the bits with a reaming facility to bore an annulus around the rods, mitigating the grinding effect of the extremely hard chromite.

The Diamec is maintained by Kemi personnel, assisted by the Atlas Copco technician on site if necessary. The mine is drilling 900-1 000 m/month in this application, a very large amount by any standard.

Mining expansion

Kemi chose the APC hydraulic control system rather than the Pilot Hydraulic Control PHC option for a number of rea-sons. APC gives the driller freedom to empty core while the Diamec is drilling on automatic, which means the rig can be operated by only one person, rather than the usual two. It can also be used for remote control for operator safety. The Kemi operators, who previously

worked with the Diamec 264 and are therefore used to the APC system, parti- cularly like the joystick control. However, Kemi does not presently use the per-formance data downloading facility because the ore is too variable for the data to be of use in subsequent ope-rations. Not surprisingly given the ore variability, penetration rate varies from as low as 20 cm per minute but is typi-cally 30-35 cm/min, at the high end of the performance range for Diamec U6 machines. The APC is very easy for inexperienced drillers to use, but only an experienced driller can set the system parameters. The sensitivity of the APC control contributes to the excellent bit life at Kemi, which is 600-700 m with a recorded high of 900 m. Rod life has been enhanced by fitting the bits with a reaming facility to bore an annulus around the rods, mitigating the grinding effect of the extremely hard chromite.

The Diamec is maintained by Kemi personnel, assisted by the Atlas Copco technician on site if necessary. The mine is drilling 900-1 000 m/month in this application, a very large amount by any standard.

acknowledgements

Atlas Copco is grateful to the manage-ment and staff at Kemi for their helpful inputs to this article. Particular men-tion goes to Jyrki Salmi, manager-mining, Timo Huhtelin, chief geologist, and Jukka Pitkäjärvi, who is now at Talvivaara.

Atlas Copco colleague, Carl Hansen, in dialogue with a Kemi operator.

66 exploration drilling

Collaborative design

The new rig was designed by Atlas Copco in conjunction with Metzke Engineering in Australia. Sheldon Burt, head of SBD Drilling, describes the Explorac 220RC reverse circulation rig as a world class rig that takes reverse circulation drilling to the next level.

Among the key health and safety features on the rig are noise suppression to 82 dB(A) at 7 m distance, a remote driller’s console, a KL rod handler, SDS Ausminco fire suppression system, and high-pressure plumbing mounted under the deck.

The Explorac 220RC has a full length underbody hydrocarbons spillage tray and Euro 3 emissions level rated deck engine.

Right equipment

RC is a method known for its advan-tageous cost structure, metre rate drilled, speed, maintained accuracy and sam- pling efficiency. There are several criti-cal factors in the design and use of the Explorac 220RC that combine to make this equipment efficient and profitable for the RC contractor.

Downhole gear that has been opti-mized to match the rig air and hydrau-lics is important in order to maintain low drilling costs. Fast hydraulics, with userfriendly controls and hands-free handling of most downhole gear, means faster rod pulls and less time spent on other non-productive tasks. The vari-able position sliding dumping mast on

the Explorac 220RC can be positioned at any angle from 45 to 90 degrees, and the slips table height can be adjusted up to 1m to allow easy access to the drill hole collar. In addition, an integrated cyclone and sample collection system allows continuous, dust-free sampling with little or no pause in the drilling process.

PeRTh, WeSTeRn auSTRalia

Reverse circulation drilling in australiaexpectations satisfiedThe technique of reverse circula-tion (RC) drilling is rapidly gaining ground as the method of choice for obtaining consistently high qual-ity rock samples with speed and efficiency. Until recently, drillers have had to modify existing rigs for RC drilling of deep exploration holes. Now, Atlas Copco has deve- loped a completely new concept in its Explorac 220RC reverse circu-lation rig, providing exploration drillers with the only RC drill rig on the market that is truly tailor made for the job.

Explorac 220RC reverse circulation rig mounted on crawler with 50 pipes rack. Exploring for iron ore in West Africa down to 350-400 meters.

ReVeRSe CiRCulaTiOn DRilling in auSTRalia

exploration drilling 67

Performance with safetyBecause the Explorac 220RC is designed specifically for the job, it has quickly become the mining industry benchmark unit for safety and performance.

With its high on board air capacity of 519 lit/s at 31 bar (1 100 cfm at 450 psi), the rig can drill to greater depths than conventional RC rigs, without the need for boosters and auxiliary power units.

However, if backup air is required, it can be made available in the form of a Hurricane 6T booster rated to more than 1 133 lit/s at 69 bar (2 400 cfm at 1 000 psi), and an Atlas Copco XRVS 466 auxiliary compressor rated to 453 lit/s at 25 bar (950 cfm at 365 psi).

The onboard Atlas Copco XRX 12 compressor is a new, 30 bar pressure, two stage rotary screw compressor. Compact and lightweight, it is ideally rated for RC drilling and requires low engine power leading to significant fuel savings. Multiple connection points are provided for safe positioning of an auxiliary compressor and/or booster compressor. All air lines are steel and designed for 70 bar (1 015 psi).

Convenient controls

The unique control panel is portable and rugged. It can be positioned up to 10 m from the rig, providing unequalled operator safety and maximum visibility of the drilling and tool handling proc-esses. The ergonomically designed, adjustable panel gives comfortable and precise control over all drilling, rod handling, sampling and rig manage-ment functions. The integrated display screen is clearly read in any conditions and shows all drilling information, para- meters and warnings. It also monitors and displays all engine, compressor and hydraulic system information and ser- vice data. Troubleshooting is simplified because the electronic control unit ma-nages all functions The Explorac 220RC is powered by the latest generation electronic Caterpillar C18 engine which exceeds Euro 3 emission standards. An intelligent engine management package linked with all other systems on the rig can adjust critical functions to provide optimum performance, reliability and fuel efficiency.

easy drilling

The KL rod handler on the Explorac 220RC is a proven and versatile com-ponent. It provides hands-free loading, unloading and stacking of drill pipes, both from the rig and from a rod truck or from racks that can be positioned anywhere within a 210 degree arc to the side or rear of the rig. It is operated by remote control, either by the driller or off-siders. This hands-free loading, unloading and stacking of drill pipes makes the job easier and safer.

The rotation head is a proven, robust unit that has two high torque variable speed hydraulic motors driving through a single reduction. The integrated above- head RC air and mud swivel is compact, reliable and easy to maintain. Adjust- ment, alignment and maintenance are simplified with a unique mounting sy- stem, which also allows the head to be

easily removed from the mast without disconnecting the feed chains. The fully hydraulic breakout table is extremely versatile. The front opens to 310 mm and not only guides the drill string, but also clamps and holds any downhole gear or casing when breaking out. A hydraulic sliding key/spanner retains the drill rods in normal operation, and the hands-free hydraulic wrench per-forms all breakout functions safely.

acknowledgements

Atlas Copco is grateful to Metzke Engineering and Sheldon Burt for their assistance with the production of this article, a version of which first appeared in Atlas Copco Australia house magazines.

Explorac 220RC reverse circulation rig mounted on truck, RC drilling for gold deposits in Western Australia, using 4½ OD RC dual wall pipes.

68 exploration drilling

Diamec u6 MCRKey features of the Diamec U6 MCR are safety, strength, and a well-proven solu-tion with a high level of engineering. As core drilling is heavy drilling, there is a need for a robust carrier. Also, the 1.8 m feed frame enables higher productivity. These features particu-larly suit the drilling of shorter holes in underground operations. Ore defini-tion drilling, where the rig needs to be moved more often, benefits by a reduc-tion of one working shift per move.

A major strength of the Diamec U6 MCR is that a single manufacturer sup- plies carrier, boom and drill unit, ma-king aftermarket support much simpler. Both the Simba 1257 carrier and the Diamec U6 drill unit are robust, well proven components. Computer assist-ance, APC, is available as an option.

The greater mobility and ease of trans-port makes the rig independent from other mining production equipment.

The main markets for the MCR rig are Australia, Canada and Scandinavia, plus Chile and Mexico.

Barminco experience

Customers for the Diamec U6 MCR are typically underground contractors and in house contractor teams in larger mi-ning companies.

For 20 years, Barminco has been one of Australia’s leading underground mi- ning contractors, initially providing ser- vices to the mines in Western Australia, and latterly expanding to other Australian states. The contractor has a range of ex- perience with most underground mining methods from narrow vein small de-posits to large scale sub-level caving

COunTRyWiDe, auSTRalia

Diamec MCR in australia

Saving time and effortThe Diamec MCR (Mobile Carrier Rig) was developed to improve rig flexibility and mobility. The first standard product was based on a Diamec U6 PHC or APC car-rier, both of which are well proven components. The Diamec MCR has more flexibility, and reaches further in wider angles. Setup and moving of the rig is much shorter, taking only 25% of the time when compared to a traditional Diamec rig. As the Diamec MCR moves by itself, the drilling contractor does not have to rely on mining ope-rations equipment for moving the unit, and as all components such as power unit and control unit are fixed on the rig, no disassembly is required.

Diamec U6 MCR underground core drilling rig.

DiaMeC MCR in auSTRalia

exploration drilling 69

operations, and has gained a high re- gard for safe and efficient performance.

Barminco are using Diamec U6 MCR models in the Australian underground operations, and now have three at work at different sites. They are finding that, while the drilling rates are comparable with other rigs, they are achieving the expected savings in rig moving time.

One major advantage reported by the company is that, by moving all of the drilling components as one piece from site to site, they are seeing a reduction in heavy manual labour when lifting gear onto the utility truck or trailer. The chance of contaminants entering the hydraulic system is reduced by not ha-ving to de-hose when moving site, and there is no need for jacking up the rig and power pack to fit wheels and tow bars. By using stingers for short holes, pinning of the rig base and the faceplate is also reduced.

Safety advantages include a reduced need to work at height when pinning the rig on up-holes, and a reduction in the trip hazards in the vicinity of the drill rig. The moving time of the drill rig has reduced greatly, creating more drilling time and increasing drilling output.

Summary

The Diamec U6 MCR is aimed at the main exploration markets in Australia, Canada, USA, and Scandinavia. Secon-dary markets are in South America. All of these regions have mines where ore definition drilling is a necessity, and where the MCR can reduce costs by increased availability to drill. The robust carrier and drill unit are de-signed for mobility and heavy usage in the underground situation.

acknowledgements

Atlas Copco is grateful to David Miitel, General Manager Diamond Drilling with Barminco Limited, for his inputs and assistance with reviewing this article.

The Diamec MCR in operation in Wiluna Mine, in Western Australia.

70 exploration drilling

Changing times

Until two years ago, exploration for non- ferrous metal in Brazil was carried out by conventional diamond core drilling, following Canadian models which have been adopted as the parameter by virtu-ally all Brazilian mines, irrespective of the ore being prospected.

The times, however, are changing and new technologies are being introduced. In the case of nickel ore exploration, conventional core drilling is giving way to reverse circulation (RC), mainly due to the excellent results obtained with this method by Australian miners.

The prime example of this change of methods is at Votorantim Metais (VMetais), the biggest local producer of metallic nickel in South America.

Since 1957, the company has ex-ploited the nickel ore in the district of Niquelândia, Goiás State, and processes it to the metallic product in the district of São Miguel Paulista, São Paulo State.

Motivated by the continuing high inter- national demand for nickel and its deri-vatives, VMetais has decided to increase capacity with a new project for Fe-Ni alloy production. This is being built along- side the existing mine and processing plant in Niquelândia, to produce 10 600 t/y of contained nickel by the pyrometallurgi- cal process, or 42 400 t/y of Fe-Ni alloy. The latter is widely employed in stainless steel production, where annual world demand is growing by 4% to 6%.

new reserves

To support this new industrial project, the company needed to identify and to measure a new reserve of nickel ore. The new mine is located alongside the mineral bed being mined by the Caron

unit, producer of nickel carbonate, which is the main input for production of me-tallic nickel in São Miguel Paulista.

The new reserve is distributed along the dunitic unit of the mafic-ultramafic complex of Niquelândia, occurring along a strike of 20 km in the NNE-SSW direction. It is of the saprolitic type, with an average thickness of 5 m, and contains total resources of up to 35 million t with a content of 1.3% nickel.

Rotary core drilling was employed as the sole method when dimensioning the original mineral bed to be exploited in Niquelândia for the Caron process. However, the volume of drilling required for the new reserve warranted a faster system, so RC drilling was introduced by VMetais to supplement their core drilling effort.

The team members of V Metais standing in front of the Explorac R50 Reverse circulation rig.

gOiaS, BRaZil

Reverse circulation technology wins in BrazilComplex taskThe prolonged run of high prices for nickel and its by-product cobalt on the London Metal Ex- change (LME) has sparked a world- wide revolution in the nickel sector. New mining projects are being started, and existing ope-rations expanded, to supply heavy demands from emerging markets such as China and India. In Brazil, the portfolio of nickel-related pro- jects is valued at US$4 billion and will add more than 240 000 t/y of the metal to the existing produc-tion of 37 000 t/y as concentrate, metallic, matte and Fe-Ni alloys. To identify and define new reser- ves, and then to extract the nickel ore, is a complex task for which the start point is generally an ex- ploration drilling project. Reverse circulation (RC) drilling using Atlas Copco Explorac R50 technology has been introduced at Votorantim Metais to speed things up.

ReVeRSe CiRCulaTiOn TeChnOlOgy WinS in BRaZil

exploration drilling 71

Defining resources

To identify the new ore body for the Fe-Ni project, some 38 000 m of core drilling on a pattern of 62 m x 50 m was undertaken between 2004 and 2007. Detailed research was initiated in 2007 with a pattern of 25 m x 31 m to define the resources of the ore body in the cate- gory of “measured reserves”. To meet the target, approximately 13 000 m were drilled by diamond core drilling, and 8 000 m performed by reverse circu-lation process using rotary percussive equipment.

In 2008, diamond core drilling was abandoned in favour of the RC method, and a total of 18 000 m of exploration drilling was undertaken using the new method.

Significantly, the company decided that all future exploration drilling will use the rotary percussive method with reverse circulation, because of the bet- ter overall quality of the job, improved drilling speed, easier transportation flexi- bility of the equipment and its opera-tion, and higher quality of the samples obtained.

For 2009, VMetais plans to continue using RC drilling to define the resources in the ore body.

high mobility

The RC drilling method was first uti-lized by VMetais in another nickel ore project, Montes Claros in Goiás State. Because the rate of rotary diamond core drilling could not keep up with the re- quired schedule at Niquelândia, an Atlas Copco Explorac R50 was introduced. This was the first such unit to arrive in Brazil, and was used as a test bed to establish the recovery and quality of samples using RC drilling. The holes in the exploration area were shallow, and ideally suited to the mobility of the Explorac R50, because the rig needed to move many times each day. Because the rig is equipped with crawlers, it can move easily in the difficult terrain of the drilling sites in Niquelândia.

By comparison, the diamond core drill must be disassembled for transport and reassembled at each new work-place, or at least be towed by a tractor on an improvized skid or crawler track.

This proved to be the most important function of the low productivity of the core drills. Using RC drilling with the Explorac R50, production delays were minimized, and dimensioning of the mineral reserves for the Fe-Ni project was spee ded up.

Comparative testing

Tests were initiated in August, 2007 and, after a comparison of the results from the chemical analyses involving the two drilling methods, RC was quickly integrated into the company plans.

The comparative test involved drill-ing of a hole with the Explorac R50 at a 2 m distance from an existing core drilled hole.

The speed and mobility of the rig was monitored in steep and wet terrain, along with the volume of recovered sam- ples and their chemical analyses. The Explorac R50 moved very well over dif-fering terrain, was faster, and presented high recovery. The rig returned above 90% of each drilled metre, whether drilling through loose material or solid rock.

The chemical results were very simi-lar to those obtained by rotary diamond drilling, and the drilling speed in dry material was superior. In 2007, some 18 conventional rigs were needed to achieve 13 000 m of drilling, while the two RC rigs drilled 8 000 m.

The result of the chemical analyses varied only at the ore to waste rock tran- sitions, where study of the lithologic contact was better than metre-by-metre sampling. However, this does not affect the final result, so is inconsequential in this situation.

Shallow holes

Due to the fact the holes are very shallow, some only 8 m deep, with diameters from 5 in to 5.125 in, RC production is as much as 10 times that of the conven-tional method, in plain and dry areas. In reality, VMetais drills up to 150 m/day of shallow holes that are close to each other, compared to a maximum of 45 m/day obtained by the rotary diamond core drilling system, or 10 to 15 m/shift.In more steep topographies, it is ne-cessary to have a compressor towed by

a tractor to allow the operation of the drill, and this makes the machine’s mo-bilization more difficult. Even so, the Explorac R50 produces five times more than the conventional method.

After comprehensive comparisons between core drilling and RC, the com- pany now employs the RC method using equipment supplied by Atlas Copco in all three lateritic nickel projects: Montes Claros; Fe-Ni; and the existing Caron.

VMetais are well satisfied with the drilling system and its productivity, and appreciate the support given by Atlas Copco, which, they say, is always very rapid, of optimum quality, and with pro- blems promptly attended to and solu-tions found. The Atlas Copco technical team has made many visits following startup of the Explorac R50 to help with maintenance and to advise on operation of the drilling system.

acknowledgements

Atlas Copco is grateful to the manage-ment at VMetais for their inputs to this article and for permission to publish.

Rod handling.

72 exploration drilling

unique challenges

Developed in 1957, and located in the Canadian province of Manitoba, the Thompson T-1 shaft first began produc-tion in 1959 and to date has produced more than 70.7 million metric tons of ore, for a total of 1.95 million kg of nickel. It is currently at a depth of 1 341 m.

Exploration is now being conducted at the 2800 ft level (850 m), where unique challenges had Vale Inco’s Manitoba Operations seeking innovative and effi- cient solutions. They needed to commis-sion a new drill for the exploration pro- ject and, based on past experience, their first call was to the Atlas Copco office in the provincial capital of Winnipeg.

Until this point, they had been using a skid-mounted Diamec 252 core drill-ing rig, which had given consistently good performance. However, moving the rig to different drilling locations in a single operator environment made it an impractical proposition. In addi- tion, Vale Inco needed a rig that would work on multiple levels in the same

mine, including older areas with space-restricted access and different electrical requirements. It needed to be portable enough to be moved from station to sta-tion, narrow enough to fit in the cage, and safe enough for one-man operation.

Diamec u6

The compact design and flexible posi- tioner allows a single operator, working alone, to set the feed frame in any verti- cal position from +90 to -90 degrees without moving the wireline hoist. In addition, the turntable option enables the drill to quickly be positioned in the horizontal plane.

The improved control panel on the Diamec U6 enables full control over drilling, giving the driller more time for emptying core barrels and preparing equipment. Most drills run as a two-man operation because, at a 850 m hole depth (2789') it is hard to hold the tube,

drain the water and get the overshot off. With the Diamec U6, a helper is not required and, because it is an inte-grated unit, it is much faster to move around to different set-ups. The mine is also impressed with the drill’s design, mechanical availability and durability, noting improvements over what they have used in the past.

Vale Inco Manitoba Operations is using exclusively Atlas Copco ITH pro- ducts for this project, and Atlas Copco impregnated diamond core bits.

“I’m very pleased with both the ease of use, manoeuvrability and overall production. I would absolutely recommend this unit to my drilling colleagues”.

Gerald CarrierD1 Diamond Driller

and Supervisor

ManiTOBa, CanaDa

Thin wall core barrels improve productivitylighter means fasterVale Inco’s ore body exploration in the T-1 shaft at its Thompson minesite in Manitoba, Canada is a situation where Atlas Copco has been quick to respond to the cus- tomer’s need for innovative prod-ucts and after market services for exploration in extreme condi- tions. To satisfy the rigorous de- mands of this project, Atlas Copco supplied a capital, consumable, and total care solution. Highly pro- ductive double tube thin wall core barrels with light weight wireline drill rods, complemented by high performance diamond bits, were chosen to optimize the mobility and ergonomics of the Diamec U6 core drilling rig design features and realize the full productivity effi-ciencies of the complete package.

Drilling with BOTW Thin wall core barrels in underground application.

exPlORaTiOn PaCkage SOluTiOn iMPROVeS PRODuCTiViTy in ManiTOBa

exploration drilling 73

Thin wall

The project is taking full advantage of the AOTW and BOTW double tube thin wall core barrel designs.

Thin wall systems are built around speciality application tubing having thinner cross sections, which translates into lighter weight drill rods and thinner diamond bits. For drill rods, the weight reduction is a benefit for Vale Inco ope-rators, and effectively extends the depth capacity of their drill. Complementary diamond bits, having to cut less rock surface area, require less feed force and yield higher penetration rates.

Ruggedly built by design, thin wall core barrels are used in all borehole orientations at Vale Inco, and are often extended to increase the total amount of productive drilling time by reducing tripping of the tools in deeper holes.

Vale Inco extract a more represen-tative sample volume and increase mea- surable core recovery with a larger dia- meter core sample, without any increase to nominal borehole diameter. Some calculated trial and error is employed when finding the perfect combination of In-The-Hole tools for this type of underground project. Atlas Copco staff are experts on what the bits and core barrels have been designed for, sup- plying a range of products, testing them with the operator, checking the ope-rating parameters against productivity and figuring out which product combi-nations work best under each specific condition.

“We’re averaging between 24 and 37 meters (80 to 100 feet) per shift. These are a little larger barrel, ( core diameter ) but they’re a lot more durable for the conditions and depths we’re dealing with here.”

Bradley WoytkiwDriller

Customer communication

The commitment to superior productivity through dependable and innovative quality In-The-Hole products is a two way street. Like many other end users, Vale Inco Manitoba Operations uses

the full Atlas Copco line of exploration products and services, from the drill-ing rig to the bit, and all the tools in between. The Winnipeg location makes getting tools, parts and service to the operator much more streamlined.

Atlas Copco uses their Net Promoter Score (NPS), a customer-centric feed-back survey, which assists them in product development and actively trig-gers improved service and communi- cation with customers such as Vale Inco. The NPS survey involves the entire Atlas Copco organization and considers transactional surveys, such as when drills are delivered and when on-site

maintenance and technical services are performed. Atlas Copco and Vale Inco are taking their relationship to the next level by working together to develop an in-house drilling programme at the Thompson mine.

acknowledgements

Atlas Copco is grateful to the manage-ment of Vale Inco, Canada and Bradley Woytkiw, driller and Gerald Carrier, D1 diamond driller and supervisor, for their contributions to this article and permission to publish.

Diamec U6 core drilling rig using a Thin wall drilling package.

74 exploration drilling

Major investmentThe Cadillac fault is a major structural feature of the geology of the area, cove-ring a stretch of ground approximately 400 km-long and 5 km-wide. It is a break in the earth’s crust that extends from Timmins in the west to Val D’Or in the east, formed when the Canadian Shield broke over 3 billion years ago. During the upthrust, magma, or molten rock, rose and solidified within the fracture. The magma carried with it precious metals such as gold and silver, as well as copper and zinc.

Because of its economic impor-tance, some 80% of all the investments in Quebec’s mineral exploration and ore deposit development are currently made in the Abitibi-Temiscamingue and Nord-du-Quebec regions, directly along the fault. Since the first disco-very of gold in the 1920s, the ability to

explore at any significant depth along the Cadillac fault has been tested again and again, but with limited success.

uncommon ground

While core drilling technology has ad- vanced steadily since the 19th century, there are still several basic, limiting factors that will determine the depth to which a borehole can be drilled. Drilling to depths of 1 200 m to 1 800 m is common where the ground is mainly hard rock. In Val D’Or and other regions along the Fault, geological challenges demand not only superior product tech-nology and performance, but also sup-erior contractor competence. Drilling contractors have to put their skills and experience to the test on every hole.Jean-Claude Gendron, Vice-President of Operations for Forage Mercier Inc., a

QueBeC, CanaDa

groundbreaking technology in the Valley of gold

Cadillac faultDuring the early part of the 20th century, major discoveries in pre-cious metals were made in the Abitibi-Témiscamingue region of Québec. These included copper-gold at Rouyn-Noranda in 1922 and gold at Val D’Or in 1925. Subsequently, many mines were developed in ore bodies disco-vered near these communities, all of them located along what is known as the Cadillac fault, part of the upthrust that created the Canadian Shield billions of years ago. However, exploration drill-ing conditions have always been difficult, testing contractors and equipment to the limit. The intro-duction by Atlas Copco of its BT rods, with a rated depth capacity of 2 600 m, has produced a mar-ked improvement in results.

Forage Mercier crew at Val D’Or.

gROunDBReaking TeChnOlOgy in The Valley OF gOlD

exploration drilling 75

company specializing in surface explo-ration diamond drilling in Val D’Or, has been doing mineral exploration along the Cadillac fault for over 43 years.

He is involved in gold exploration for a Val D’Or-based client where the prospect straddles the fault, and has presented his team with unique geo-logical challenges. They are drilling through layers of abrasive ground, sand, mud, and very hard and broken rock in which, to maintain the integrity of each hole, considerable cementing and wedging is required.

The entire procedure involved in positioning a wedge in a drill hole to achieve a required deviation can often take up to two shifts.

This is due primarily to the fact that there is a wait of at least eight hours between grouting to allow for drying. Once the wedge is placed and the deviation of the hole has been achieved, the corebarrel is re-inserted on the drill string and normal drilling resumes. In the event additional deviation is required, another wedge is installed after 60 m and the process is repeated. It is a time-consuming process and can be hard on the drilling rigs and in-the-hole tools.

Tougher threads

In April, 2008, on the recommendation of his representative from Atlas Copco, Gendron replaced the BO drill rods he had been using with BT rods, which are exclusive to Atlas Copco. He reports that the new rods work very well in the broken ground, where previously the O-threads were experiencing a lot of strain. Gendron says the BT threads are tougher, and allow more torque to be used without danger of damage or galling, all of which is important for the drillers and conditions at the Cadillac fault.

Wearing metal against metal in abra-sive cemented and wedged ground is known to be extremely hard on the rod joints and overall rod life expectancy, commonly reducing the life of the rod string by about 20%, meaning replace-ments can be required every 16 000 m, or 50 000 ft. At one location, the drillers went through some very bad ground and had to cement more than

ten times, plus a couple of wedges. This would have been very hard on the threads prior to the change, but not with BT rods. As a result, the company now spends more time drilling with the string, and less time pulling and replacing rods. Furthermore the Tuff Rod allowed the Forage Mercier team to reach a record depth of 2 378 m, or 7 800 ft, exceeding their expectations not only for depth, but also for overall integrity and life of the rod threads.

Straighter holes

More than depth, the goal of this project is to drill a straighter hole. The Forage Mercier team is using an upgraded Atlas Copco B15 drilling rig, which, along with the BT rods, has given them excellent results in the field. Because of the stronger threads, operators have noted that the drill string doesn’t bend at the joints due to worn threads.

The standard setup is for drilling at 85 to 87 degrees, which is fairly steep. Normally, readjustment would be re- quired frequently because of worn

threads shifting the rods off angle. However, this is no longer the case, so they feel this is really a superior pro-duct across the board. Forage Mercier has been relying on Atlas Copco in-the-hole tools, including drill rods and diamond bits, for over 20 years, during which time Gendron and his team have developed a strong relationship with the staff at the Atlas Copco office in Val D’Or.

When Atlas Copco technical per-sonnel visit the job sites they work with the drillers, giving them the infor- mation to solve specific problems. Forage Mercier observes that the reso-lution of the difficulties with the rods at Cadillac fault is typical of the way in which Atlas Copco supports its clients, as part of their own project team.

acknowledgements

Atlas Copco would like to thank Forage Mercier, and in particular Jean-Claude Gendron, for their assistance with this article and permission to publish.

From the left to the right: Jean-Claude Gendron, Vice-President, Forage Mercier and Christian Bergeron, Sales representative, Atlas Copco.

76 exploration drilling

location of the projectThe Hilarion project is located 50 km south of Antamina, the world class Cu-Zn reserve, and 13 km south of Mitsui’s Huanzalá mine, in the department of Ancash, Perú. The prospecting licence area covers some 8 512 hectares of a skarn type polymetallic reserve of Zn- Ag-Pb. The local climate suffers extreme weather conditions due to 4 200-5 000 m altitude and temperatures as low as -15 degrees C. The campaign deman- ded 85 000 drilled metres to 1 000 m depth using NQ pipe in limestone with presence of silica. The total number of

drilling rigs engaged on the project is 16, three of these are Christensen 3001 core drilling rigs.

Christensen CS3001 selectionThe Christensen CS3001 was chosen for this project mainly due to the ca-pacity of the equipment and the good results obtained in similar campaigns where deep drill holes of 1 000 m in NQ were required at up to 45 degrees inclination.

The threading and unthreading ope- rations on the Christensen CS3001 were

anCaSh, PeRu

Christensen CS3001 works well in extreme conditions

Problems and challengesWhen long-standing Atlas Copco customer Lucho Rodriguez from Geotec in Peru needed to get big drilling performance on his Hilarion contract in the high Andes, the choice was easy. The Christensen CS3001 surface core drilling rig has the mobility, the drilling capacity, and the power to operate under extreme condi-tions of altitude and weather, with only minor modifications.

Discussions about the performance and design of a Christensen CS3001 surface core drilling rig at 4800 m above sea level.

ChRiSTenSen CS3001 WORkS Well in exTReMe COnDiTiOnS

exploration drilling 77

known to be much safer and more effi- cient in similar long hole drilling pro-jects, where the previously accepted risks of accidents and breakdown were replaced by safety and speed.

The drilling rate achieved by the Christensen CS3001 at Hilarion is 3.5 m/ hour at 87% availability. Two shifts every day are spent on drilling ope-rations, requiring one driller and two helpers. One shift/day comprising three mechanics and two foremen is spent on maintenance of the fleet of rigs.

Some problems were experienced initially with the Christensen CS3001 drill head when water and mud entered the unit, contaminating the oil. These were resolved by replacing the excluder seal on top of the head by two oil seals.

Christensen CS3001 specificationThe Christensen CS3001 is a field pro- ven concept that has become exceedingly popular amongst contractors looking for a tough medium- to deep-hole ex- ploration drilling rig. Rated at a drilling capacity of 1 830 m, this truck mounted model features a hydraulic slide mounted control panel with all drilling and engine controls in one location. This provides fingertip control of all functions and facilitates a good view of the worksite and, in particular, improved visibility of main and wireline hoists. As this type of drilling rig may find its way into high terrain, the Christensen CS3001 is equipped with a high altitude kit to ensure operation in situations where the air is much thinner than normal. The rig’s main features are a Cummins 6 CTA 8.3L turbocharged aftercooled diesel engine, and a drillhead with P size 117 mm spindle, maximum 1 300 rev/min, maximum torque 4 800 Nm, and four- speed transmission. The main hoist capacity is 133 kN, and lift capacity of the feed is 155 kN. Feed length is 3.35 m, and rod pull length is 6 m.

acknowledgements

We thank Lucho Rodriguez, Service Manager at Geotec in Peru for his con-tributions to this article and permission to publish.

The worksite is located at extreme altitudes in the Andes.

One of the three Christensen CS3001 surface core drilling rigs at the Hilarion project runned by Geotec.

Maintenance and service talks between Lucho Rodriguez and members of the drill crew.

78 exploration drilling

CORe DRilling RigS

Main specifications Diamec 232

Basic dataMax depth 120 m (A) 400 ft (A)Diameter 50 mm 2"Max speed 2 200 rpmMax torque 250 Nm 180 lbf ftFeed force 20 kN 4 500 lbfFeed length 850 mm 33 1/2"ModulesFlush pump Trido 45Power unit* PU 20E or PU 20D

* Electric (E) or diesel (D)

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Diamec 232

Diamec 232 is an all-hydraulic drilling rig, ideal for coring in narrow tunnels or galleries as well as in other cramped spaces underground and for grout hole drilling. The rig is equally efficient for surface drilling operations.

Compact design and light weight, makes the Diamec 232 easy and fast to set-up for c drilling. This in turn offers quicker moves between drill sites, without disturbing normal production routines in the mine, or grouting sequences in dam galleries.

The Diamec 232 is also aluminium-free for use in coal mines. Combined with a special designed power unit, this machine can be used with HFC (water/glycol) flame-proof liquids in the hydraulic circuit, thereby complying with another statutory requirement in underground coal mines.

Features• Allhydraulicoperation• Mechanizedrodhandling• Hingemountedrodholderandrotationunit• Lowweightandcompactdesignforeasytomove around • Impressiverodrunningspeed• Variablehydraulicmotoronrotationunitforstepless regulation of spindle speed keeping max. power output

Main optional equipment• Electricordieseldrivenpowerunitwithabasicdesign and with a double hydraulic pump set-up for optimal operation• Columnmounting

DIA

ME

C 2

32

1400

1510

230500

exploration drilling 79

CORe DRilling RigS

Main specifications Diamec U4

Basic dataMax depth 500 m (A) 1 650 ft (A)Diameter 78 mm 3 1/16"Max speed* 1 800 rpmMax torque* 660 Nm 490 lbf ftFeed force 52 kN 11 700 lbfFeed length 850 mm or 1 800 mm 33 1/2" or 70"ModulesFlush pump Trido 80Power unit** PU 45E or PU 40DT

* Also available as high torque ** Electric (E) or diesel (D)

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Diamec u4

Diamec U4 is a compact and powerful core drilling rig for its size and easy to set up. Ideal for both underground and surface drilling, it can be equipped with a long or short feed frame and wire line equipment. The push-equals-pull feed cylinder also allows for maximum capacity uphole and downhole exploration drilling. Diamec U4 is ideal for both conventional and wire line drilling.

There is also a wide choice of equipment available for the Diamec U4, including two feed frames, two rotation units, two chassis models and two types of control systems.

In combination with the optional control system, APC the Diamec U4 is the most modern, user-friendly and productive core drilling rig in it's size available on the market today.

FeaturesA versatile, easy-to-use positioner, for setting up the •

rig -90 to + 90Robust feed frame with a telescopic feed cylinder•Equal pull and push capacity, for optimal underground •

drillingAll new rod holder with the latest gas spring technology•State-of-the-art hydraulic system•Turn table mounted on skid for easy to set up in •

horizontal planImpressive rod running speed•

Main optional equipment• Twooptionsforcontrolsystem:PHC–PilotHydraulic ControlandAPC–AutomaticPerformanceControl• WLhoist(500m)mountedonthepositionerarm• Electricordieseldrivenpowerunitwithabasicdesign and with a double hydraulic pump set-up for optimal operation

2260

2820

620

355

DIAMEC U4

80 exploration drilling

CORe DRilling RigS

Main specifications Diamec U6 and U6DHBasic data U6 U6DHMax depth 1 000 m (A) 3 300 ft (A) 1 000 m (B) 3 300 ft (B)Diameter 78 mm 3 1/16" 100 mm 4"Max speed* 1 800 rpm 1 400 rpmMax torque* 700 Nm 515 lbf ft 1 375 Nm 1 020 lbf ftFeed force 65 kN 14 600 lbf 89 kN 20 000 lbfFeed length 850 mm or

1 800 mm33 1/2" or 70"

1 800 mm 70"

Modules U6 U6DHFlush pump Trido 80 Trido 140Power unit** PU 55E or PU 100DT PU 75E or PU 100DT

* Also available as high torque ** Electric (E) or diesel (DT)

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Diamec u6 and u6Dh

Diamec U6 and Diamec U6 Deep hole (DH) core drilling rigs are truly flexible exploration core drilling rigs.

They are both at home in underground and surface exploration. There’s also a wide choice of equipment available, including two feed frames, four rotation units, two chassis models and two types of control systems. This powerful and compact rig has become very popular amongst those wanting to drill deep and large holes. The unique positioner allows you to move the feed frame through 180°.

FeaturesA versatile, easy-to-use positioner, for setting up the rig •

-90 to + 90Robust feed frame with a telescopic feed cylinder•Equal pull and push capacity, for optimal underground •

drillingAll new rod holder with the latest gas spring technology•State-of-the-art hydraulic system•Turn table mounted on skid for easy to set up in •

horizontal planWLhoist(1300m)mountedonthepositionerarm•Impressive rod running speed•

Main optional equipmentTwooptionsforcontrolsystem:PHC–PilotHydraulic•

ControlandAPC–AutomaticPerformanceControlElectric or diesel driven power unit with a basic design •

and with a double hydraulic pump set-up for optimal operation

Feed extention for optimal surface operation•

2900

2645

700

400

exploration drilling 81

CORe DRilling RigS

Main specifications Diamec U8

Basic dataMax depth 2 000 m (B) 6 600 ft (B)Diameter 100 mm 4"Max speed 1 200 rpmMax torque 2 300 Nm 1 630 lbf ftFeed force 133 kN 29 000 lbfFeed length 1 800 mm 70"ModulesFlush pump Trido 140Power unit* PU 110E or PU 160DT

* Electric (E) or diesel (DT)

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Diamec u8

Diamec U8 is a true deep hole core drilling rig. It’s quite simply the most powerful exploration rig for its size on the market today. At home both above and below ground.

Often operating for weeks working the same bore hole, it’s imperative that the rig keeps running efficiently. Ergonomics and safety are also a consideration in the design, providing for safe and comfortable operation and improved rod handling.

As a trend in the exploration segment, to drill deeper, the Diamec U8 is and will be an important rig to meet theneedsbothundergroundandonsurface.Withuser-friendliness and safety as highest priority the Diamec U8 will be a state of the art rig for many years to come.

Features• Robustfeedframewithatelescopicfeedcylinder• Equalpullandpushcapacity,foroptimalunderground drilling• All new rod holder with the latest gas spring technology• State-of-the-arthydraulicsystem• Impressiverodrunningspeed

Main optional equipmentAvailable in two different versions; Underground •

version(compact,andwithaWL-hoist(1300m)and Surface version (long mast extension to handle 6 m rods,WL-hoistwithhighcapacity(2000m)

Twooptionsforcontrolsystem:PHC–PilotHydraulic• ControlandAPC–AutomaticPerformanceControl

Electric or diesel driven power unit with a basic design • and with a triple hydraulic pump set-up for optimal operation.

770

455

2320

3100

DIAM

EC U8

82 exploration drilling

CORe DRilling RigS

Main specifications Diamec MCR

Basic dataMax depth 1 000 m (A) 3 300 ft (A)Diameter 78 mm 3 1/16"Max speed 1 800 rpmMax torque 700 Nm 515 lbf ftFeed force 65 kN 14 600 lbfFeed length 1 800 mm 70"ModulesFlush pump Trido 80Electric power unit PU 75E (To be used when drilling)

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Diamec u6 MCR

The Diamec Mobile Carrier Rig (MCR) combines the best of two worlds: the high productivity and accuracy in core drilling of a Diamec core drilling rig, with the robustness and mobility of a Simba carrier! This combination pro-vides the exploration driller with unmatched productivity in underground mining

The Diamec MCR™ is completely self sufficient and can swiftly move from one drill spot to another. The time saving can be more than 50% depending on distance etc! Lesspeopleandequipmentneedstobeinvolved,andthe entire core drilling equipment is moved in one piece. Settingupfornextdrillholeisdonewithinminutes.Lesssetting up time of course means higher productivity. This is also the case for the Diamec U6 MCR, the idea is that whenmoving–moveitfast,whendrilling–drillfast!

Features• Robustfeedframewithatelescopicfeedcylinder

Equal pull and push capacity, for optimal underground • drilling

WLhoist(1300m)mountedontheboomarm•For drilling an electric driven power unit is used with a •

double hydraulic pump set-up for optimal operation. Everything needed for optimal core drilling installed on •

the carrier (drill unit, hydraulic power pack, water pump, power cable etc)

Flexible boom system for variety of drill angles•Self-sufficient and gives a safe transport between drill •

locations

Main optional equipmentTwooptionsforcontrolsystem:PHC–PilotHydraulic•

ControlandAPC–AutomaticPerformanceControlSupport jacks •

DIAMEC MCR U6

8700-11000

width=3100

exploration drilling 83

CORe DRilling RigS

Christensen CS10 is the smallest core drilling rig in the range. Sharing many of the components with Christensen CS14, this trailer-mounted drilling rig has a robust long mast that is split-able into three sections. Even though it is a small drill it is equipped with all the common standard safety and operation features a modern drill rig should have such as making and breaking including thread compensation.

Withadrillcapacityof800m(NO),thisflexibledrillingrig can pull a 6 m core barrel without disconnection the over shot. CS10 is a small yet highly productive core drilling perfect when small to medium depth capacity is needed.

Main specifications CS10

Basic dataDepth capacity (NO) 800 m 2 625 ftDrill rod size, wire line B-PMain hoist 53.5 kN 12 000 lbLiftcapacity,feed 90 kN 20 200 lbFeed length 1.83 m 6 ftRod pull length 6 m 20 ftEngine (up to 3000m a.s.l.) Cummins QSB4.5, 4 cyl Tier IIIEngine power at 1800 rpm 111kW 148 hpWeight(includingTrido140) 5 000 kg 10 200 lb

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Christensen CS10

FeaturesHydraulic P-size rod holder•Mast in three sections•Hydraulic mast raise•Wearlinesonlowermast•Safety guards•Largecrownsheavewheel•4 hydraulic levelling jacks•Making and breaking including hydraulic tread •

compensationHigh quality fuel filters and water separator•

Main Optional equipmentWater/mudpump,Trido140•WaterflowandRPMmeterkit•High altitude version •

(for operations higher than 3 000 above sea level)Hydraulic mud mixer•

5900

1110

0

CHRISTENSEN CS10

Width=2200

84 exploration drilling

CORe DRilling RigS

Christensen CS14 represents one of the most flexible drilling rig sizes in the Christensen range with a drilling capacity of 1200 m. With its relatively small dimensions and the built in power and safety this rigs is capable of taking on the vast majority of core drill projects.

Christensen CS14 is a trailer mounted medium sized core drill rig for surface exploration applications. CS14 is built on the well proven Christensen concept meaning easy operation, simple technology, high capacity and reliable performance. In addition the rig is equipped with many features that ensure easy, safe and high productive operation. This model is operation in all markets around the world, why it is safe to say that this is the work horse of the Christensen range.

Main specifications CS14

Basic dataDepth capacity (NO) 1 200 m 4 042 ftDrill rod size, wire line B-PMain hoist 80 kN 18 000 lbLiftcapacity,feed 138 kN 31 020 lbFeed length 3.5 m 11.5 ftRod pull length 6 m 20 ftEngine Cummins QSB6.7, 6 cyl Tier IIIEngine power at 1800 rpm 153kW 208 hpWeight 7 000 kg 15 430 lb

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Christensen CS14

FeaturesHydraulic mast dump•Foldable mast in two sections•Largecrownsheavewheel•Hydraulic mast dump•4 hydraulic levelling jacks•Wearlinesonlowermast•Safety guards•Making and breaking including hydraulic tread •

compensationHydraulic P-size rod holder•Towing package•High quality fuel filters and water separator•

Main Optional equipmentWater/mudpump,Trido140•WaterflowandRPMmeterkit•High altitude version (for operations higher •

than 3000 above sea level)Hydraulic mud mixer•

6127

9970

CHRISTENSEN CS14

Width=2200

exploration drilling 85

CORe DRilling RigS

CT14 is the smallest truck-mounted drilling rig, has all the equipment required mounted onto the rig chassis. A truck mounted rig offers great flexibility, capable of accessing terrain as well as offering easy transportation between different drill areas. The large platform provides a very stable drill set up.

The Christensen CT14 is a powerful, safe and ergonomic surfacecoredrillingrig.Withitsdepthcapacityof1200m (NO) this rig will suit the majority of core drill projects. Withtheextendablecontrolpanelthedrillercangetagood view of the drill operation regardless of drill angle. The main control panel offers the driller access to all drill controls, placed in a logical grouping in order for the driller to have full attention to the drill operation/helper.

Main specifications CT14

Basic dataDepth capacity (NO) 1 200 m 4 042 ftDrill rod size, wire line B-PMain hoist 80 kN 18 000 lbLiftcapacity,feed 138 kN 31 020 lbFeed length 3.5 m 11.5 ftRod pull length 6 m 20 ftEngine Cummins QSB6.7, 6 cyl Tier IIIEngine power at 1800 rpm 153kW 208 hpWeight 9 000 kg 19 840 lb

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Christensen CT14

FeaturesHydraulic mast dump•Making and breaking including hydraulic tread •

compensationLargecrownsheavewheel•Hydraulic oil reservoir with fill pump and filtration•Mast lightening kit•Rod kicker hydraulically operated•WaterflowandRPMmeterkit•Hydraulic mast raise•Extendable control panel (for drilling angle holes)•4 hydraulic levelling jacks•Wearlinesonlowermast•High quality fuel filters and water separator•Water/mudpump,Trido140•

Main Optional equipmentHigh altitude version •

(for operations higher than 3000 above sea level)Rod rack including ladder and helpers platform•

CHRISTENSEN CT14

1024

3

6767

Width=2280

86 exploration drilling

CORe DRilling RigS

The Christensen CS3001 is a field-proven concept that has become exceedingly popular amongst contractors looking for a tough medium to deep hole exploration drilling rig. Rated at a drilling capacity of 1830 m, this truck-mounted model features a hydraulic slide mounted control panel. This facilitates a good view of the worksite and full control of the operation.

As this type of drilling rig may find its way into high terrain, the Christensen CS3001 is equipped with a high altitude kit to ensures smooth operation up to 5000 m (16 400 ft) above sea level. The truck mount offers great mobility, both when transporting the rig and while going from hole to hole at the drill site. The current version of CS3001 is the third why it is safe to say that a lot of drilling experience has been designed in to the current model. All models have achieved great results even wherethedrillingconditionshavebeenreallydifficult–the CS3001 will get the job done.

Main specifications CS3001

Basic dataDepth capacity (NO) 1 830 m 6 000 ftDrill rod size, wire line B-PMain hoist 133 kN 30 000 lbLiftcapacity,feed 155 kN 35 000 lbFeed length 3.35 m 11 ftRod pull length 6 m 20 ftEngine Cummins QSC8.3, 6 cyl Tier IIIEngine power at 2000 rpm 212kW 285 hpWeight 12 810 kg 28 240 lb

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Christensen CS3001

FeaturesMaking and breaking including hydraulic tread •

compensationFour hydraulic jacks 610 mm (24 in) stroke•Hydraulic P-size holding clamp•Control panel hydraulic slide•High altitude version •

(for operations higher than 3000 above sea level)Hydraulic mud mixer•Fuel tank 950 l (250 gal)•Hydraulic swing out of the rotation unit•Rod centralizer•Water/mudpump,Trido140 •

Main Optional equipmentRod rack and helpers platform•Rod spinner tool•Rope tentioner•

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1148

3

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exploration drilling 87

CORe DRilling RigS

This truck-mounted drilling rig is the most powerful Christensen unit ever built, capable of drill down to 2450 m (NO). This rig is a stronger version of the well proven CS3001 incorporating all the design features of that rig. A foldable mast extension is available as an option, then offering a 9 m (30 ft) rod pull capacity. Together with the rod rack this offers excellent productivity when rod trip-ping in deep hole drilling.

Having inherited all the design features of the very well proven CS3001 the strongest Christensen rig will offer unsurpassed productivity for really deep applications. The well proven design also leads to minimizing down time as well as keeping the maintenance cost to a minimum.

Main specifications CS4002

Basic dataDepth capacity (NO) 2 450 m 8 030 ftDrill rod size, wire line B-PMain hoist 178 kN 40 000 lbLiftcapacity,feed 200 kN 45 000 lbFeed length 3.35 m 11 ftRod pull length 9 m 30 ftEngine Cummins QSC8.3, 6 cyl Tier IIIEngine power at 2000 rpm 212kW 285 hpWeight 13 864 kg 30 500 lb

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Christensen CS4002

FeaturesMaking and breaking including hydraulic tread •

compensationFour hydraulic jacks 610 mm (24 in) stroke•Hydraulic P-size holding clamp•Control panel hydraulic slide•Hydraulic slide on the rotation unit•Rod centraliser•High altitude version •

(for operations higher than 3000 above sea level)Hydraulic mud mixer•Fuel tank 950 l (250 gal)•Water/mudpump,Trido140 •

Main Optional equipmentFolding mast extension for 9.1 M (30 ft) pull•Rod rack and helper’s platform for 9.1 m pull mast•Rod spinner tool•Rope tentioner•

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1383

5

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88 exploration drilling

ReVeRSe CiRCulaTiOn RigS

Main specifications Explorac 220RC

Basic dataPullback 220 kN 49 438 lbfEngine CAT C-18, Tier IIIEngine power 522kW 700 hpRotation head, max torque 14 000 Nm 10 294 lbf ftRotation head, max rpm 101 rpmFoam/water pump 75 lit/min, 90 bar 2.6 cfm, 1 300 psiHandling hoist 15 kN 3 370 lbfCompressor 510 lit/sec, 30 bar 1 080 cfm, 435 barCyclone 850 lit/sec 1 800 cfmLineoiler 0.4-2.0 lit/hour 0.014-0.071 cfhTotal weight without truck 21 300 kg 47 000 lbTotal weight with truck 33 090 kg 73 000 lb

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explorac 220RC

Features• Feedbeamwithhydraulicramsandguidechainfor hydraulic hoses• Singlereductiongearboxfittedwithtwo630cm3 hydraulic geroler motors• Spindeladaptorthread4½”IF.Integratedairswivel with blow down valve• Slipstablemax.opening12in.305mm• Hydraulicallyactivatedslipswithintegratedholding clamp• Hydraulicallyoperatedslidingkey• Hydraulicallyoperatedhandsfreebreakoutsystem • Noiselevelof82dB(A)at7mdistance

Main Optional equipmentSplitter•Wirelinehoist•Rod handler•Fire suppression•

With safety and ergonomics as key issues together with latest tehnology the Explorac 220RC is made the safest and most user friendly rig of it’s type. The Explorac 220RC rigs can be used for RC drilling as well as water well drilling with just a few adjustments.

The Explorac 220RC takes over much of the physical effort requiredfromthedriller.Withthestandard1.5tonwinch, which positions directly over the hole, with a slewing boom, Explorac 220RC handles all heavy lifting requirements. In addition, hands-free breakout and rod handling systems ensure rapid and safe handling of all drill string components. A special casing handling tool attached to the rotation head gives full safety and control.

4280

4200

12100

exploration drilling 89

ReVeRSe CiRCulaTiOn RigS

explorac R50

Features• Platform,includingmastsupport• Fourhydraulicjacks• Mastcompletewith4.4mstrokelength, hold-back 60 kN• Hold-backcontrolscale• Breakouttablemaxopening310mm• Hydraulicbreak-outtongtypeRidgid48• Rotary head powered by two hydraulic motors OMT 250• Operatorsfoldingplatform

Main Optional equipmentGardner Denver mud pump 5 x 6 hydraulic driven•Mast for 6 m drillpipe length•Welder/generatorpoweredbydieselengine•Rotation unit hydraulic motor alternatives•

The Explorac R50 is a robust and reliable drill unit ideal for remote areas. It is designed to perform as an versa-tile base platform for down-the-hole percussion drilling, reverse circulation drilling and rotary drilling.

The explorac R50 is an extremely well proven workhorse with simple design. The high accessibility and reliability makes it particularly interesting for drillers operating in remote areas. Separate drill rig subframe design permits stable mounting on various standard trucks as well as special vehicles or on crawlers depending on which terrain the rig will be used in.

The proven technology and the ease of maintenance provides the driller more efficient working hours, and less downtime. This is of course of great use and interest, especially when operating in remote areas.

Main specifications Explorac R50

Basic dataPulldown 48.8 kN 11.0 k lbfHold back/lift 80.9 kN 18.2 k lbfEngine DeutzBF4L914,4cylEngine power at 2150 rpm 68kW 91 hpRotation head OMT 250Speed 0-97 rpmTorque, max 5 750 Nm 4 240 lbf ftFeed travel length 4.4 m 14.4 ftDrill pipe length 3.0 m 9.8 ftTotal weight without carrier 5 400 kg 11 900 lb

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4000

6580

2550

3510

E X P L O R A C

R50

90 exploration drilling

CORe DRilling TOOlS

excore core drilling tools

DCDMA design

Size DesignHole diameter Core diameter Hole area Core area Cutting area

% of hole areamm in mm in cm2 in2 cm2 in2

A Q** 48 1.89 26.9 1.06 18.1 2.81 5.7 0.88 68.5GM.OTW** 30.3 1.19 7.3 1.13 59.0

QTK** 30.5 1.20 7.3 1.13 59.6

48 JKT 35.3 1.39 9.8 1.52 45.9

48 LTK 35.3 1.39 9.8 1.52 45.9

48 TT 35.3 1.39 9.8 1.52 45.9B Q3** 60.0 2.36 33.5 1.31 28.3 4.37 8.8 1.36 68.7

Q** 36.4 1.43 15.8 2.45 44.0

QTK** 40.7 1.60 13.0 2.02 54.1

GM. OTW. B2** 42.0 1. 66 13.9 2.17 50.2

60 LTK 44.0 1.73 15.2 2.35 46.3N Q3** 75.6 2.98 45.1 1.77 45.0 6.96 15.9 2.47 64.6

3/50** 50.2 1.97 19.8 3.0 56.0

Q** 47.6 1.88 17.8 2.76 60.4

Q2** 50.7 2.0 20.1 3.12 55.3

GM** 56.1 2.21 24.8 3.86 44.4H Q3** 96.1 3.78 61.1 2.41 72.8 11.29 29.3 4.5 59.7

Q** 63.5 2.5 31.7 4.91 56.5P Q.G** 122.7 4.81 85.0 3.34 117.2 18.24 56.7 8.76 51.6

G3/Q3** 122.7 4.81 83.0 3.26 54.1 8.38 53.8

*Holediameterwithpilotbit**Wirelinecorebarrelsystem

Metric design

Size DesignHole diameter Core diameter Hole area Core area Cutting area

% of hole areamm in mm in cm2 in2 cm2 in2

46 TT 46.5 1.82 35.3 1.39 16.8 2.6 9.8 1.52 41.7

56 TT 56.5 2.22 45.2 1.78 24.9 3.86 16.0 2.48 35.7

Excore diamond bits are the culmination of decades of diamond drilling experience in combination with the latest in metallurgical and manufacturing technologies. The Excore, is a series of diamond drill bits that sets the standard for the mineral exploration industry.The operating range of each diamond bit has been substantially increased, which results in fewer bits required on the job site by the drilling contractor to cover a wide range of drilling conditions and simplifies bit selection for the driller.

The Excore bits are engineered with new matrices and optimized crown profiles that provide bits with excep-tional penetration rates as well as extended service lives in the toughest of drilling conditions. This means a contractor can drill both faster and deeper without changing drill bits.

The Excore bits are available in different profiles ECF (Extended Crown Profile) for slightly broken to broken

abrasive formations, patented Jet and Torpedo V profile for fast cutting in competent formations, face discharge and sand discharge for extremely broken and triple tube applications.

exploration drilling 91

CORe DRilling TOOlS

Rock group Rock characteristics Rock type

1 - 4Soft to medium hardVery abrasive to slightly abrasiveVery fractured to slightly broken

Unmetamorphosed or weakly metamorphosed shales. Sandstone and limestone.

5Medium hardAbrasive Moderately fractured to slightly broken

Limestoneanddolomite.Weatheredgranite and gneiss.Serpentinite and metaperidotite.

6Medium hardModerately abrasiveModerately fractured to slightly broken

Unmetamorphosed or weakly metamorphosed diorite. Gabbro, peridotite and gneiss. Basalt, andesite.

7Medium hard - hardModerately abrasiveSlightly fractured to competent

Metabasalt, amphibolite. Metamorphosed diorite and gabbro. Diabase.

8HardSlightly abrasiveCompetent

Quartz rich skarn. Granite and pegmatite.

9Very hardSlightly abrasiveVery competent

Metamorphosed granitic rock and quartz rich gneiss.

10Extremely hardNon-abrasive, fine grainedVery competent

Chert and jasperite. Quartzite. Highly metamorphosed volcanic.

To simplify bit selection for the driller rock formations have been categorized into three applications. Each application has a series of matrices designed specifically for that type of drilling condition which will provide optimum performance.

Application 1(Green)–Softtomediumhard,veryabrasiveto slightly abrasive and very fractured to slightly broken formation.

Application 2(Blue)–Mediumhardtohard,abrasiveto slightly abrasive, moderately fractured to competent formations.

Application 3(Red)–Veryhardtoextremelyhard,slightly abrasive to non abrasive, very competent formations.

Bit selection chart

92 exploration drilling

in-The-hOle TOOlS

in-The-hole toolsAtlas Copco offers a full range of In-The-Hole tools such as drill rods, core barrels, all based on advanced technology. They are constantly being upgraded to exceed the expec-tations from the market.

Core barrelsSurface core barrels are available in standard double tube designs with the option for easy conversion to triple tube configurations in broken ground. Thin wall core barrels, used when ground conditions and drill rig selection are appropriate, offer the end user an opportunity to increase sample size within a nominal bore hole size. Underground core barrels are available in double tube and double tube thin wall wireline core barrels and are used for flatter and up hole applications where gravity does not permit unassisted movement of the inner wireline components. Conventional core barrels produce a larger core diameter compared to the equivalent wire line nominal size. Their rugged construction and design features ensure optimization of productivity in soft to medium hard formations, allow them to be used in all orientation and are typically used in shorter boreholes.

Drill rodsWirelinedrillrodsaremanufacturedfromhighqualitycold drawn seamless tubes, which provide superior

1. Determine direction of the core drilling. If the borehole will be drilled between vertical down to 45 degrees from vertical down, choose one of the three surface style systems. For flatter or up holes, choose within the two underground ranges of corebarrel systems.

2. Determine requirements of the application. For surface style selections, determine if the application requires a double tube or triple tube design. If a double tube design is preferred choose if a standard wall or thin wall design is favored.Likewise,forunderground style selections, determine if a standard wall or thin wall design is favored.

3. Determine threads, rods and accessories. Choosing a drill rod is based on the preferred thread connection and the overall length that can be handled efficiently. Don’t forget to consider the limitations of the drill design and the envelope within which the drill will be operating. Choose the accessories that you require to complement the core barrel and drill rod selections.

Underground core barrels

Thin wall For larger core

sample

Standard wall

Surface core barrels

Double tube design Standard wall

Thin wall For larger core

sampleTriple tube design

For better core recovery in broken

ground Thread connection Overall length to

be handled

Accessories needed

yield and ultimate strength. Conventional drill rods are available in mid-weight steel and/or aluminium. Rod threads for mineral exploration applications are typically TorOforwireline,withWJtypethreadsusedwithconventional style core barrels.

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A summary of the relevant data when evaluating core sample size for corresponding core barrel systems be they double tube, triple tube or thin wall double tube for

O surface or O-U pump in configurations. A summary of weights and dimensions of tubular products to help you choose complimentary rod and casing.

DimensionsSize Metric system imperial system

Diameter length Diameter length

1.5 m 3.0 m 5 ft 10 ft

Rods OD iD kg OD iD lbs

aO /aT 44.5 34.9 6.8 13.9 1.75 1.38 15.70 31.40

agM / aTT 44.5 36.8 5.9 11.8 1.75 1.45 13.0 26.0

BO / BT 55.6 46.0 8.9 17.9 2.19 1.81 20.1 40.2

BgM / BTT 56.5 48.8 7.6 15.3 2.23 1.92 16.8 33.8

nO / nMO / nT 69.9 60.3 11.4 22.9 2.75 2.38 25.7 51.4

hO / hMO / hT 88.9 77.8 17.1 34.2 3.50 3.06 38.0 76.70

PT 114.3 101.6 25.4 56.0 4.50 4.00 56.9 123.5

Casing

aW 57.1 48.4 8.3 16.9 2.25 1.91 18.40 37.40

BW 73.0 60.3 15.3 31.2 2.88 2.38 33.80 68.80

nW 88.9 76.2 19.1 38.8 3.50 3.00 42.10 85.60

hW / hWT 114.3 101.6 25.0 50.8 4.50 4.00 55.10 112.10

PW /PWT 139.7 125.5 34.9 69.7 5.50 4.94 76.70 153.30

Double tube surface and/or undergroundSize (Surface-underground) Metric system (mm) imperial system (in)

hole diameter Core diameter hole diameter Core diameter

BO/BO-u 60.0 36.4 2.36 1.43

nO/nO-u 75.7 47.6 2.98 1.88

hO/hO-u 96.1 63.5 3.78 2.50

PO 122.7 85.0 4.83 3.34

Triple tube surfaceSize (Surface-Underground) Metric system (mm) imperial system (in)

hole diameter Core diameter hole diameter Core diameter

nO3 75.7 45.0 2.98 1.78

hO3 96.1 61.1 3.78 2.41

PO3 122.7 83.0 4.83 3.27

Double tube thin wall surface and/or undergroundSize (Surface-Underground) Metric system (mm) imperial system (in)

hole diameter Core diameter hole diameter Core diameter

aOTW / -u 48.0 30.3 1.89 1.19

BOTW / -u 60.0 42.0 2.36 1.65

nO2 75.7 50.7 2.98 2.0

Dimensions

94 exploration drilling

RC TOOlS

Reverce circulation tools

Secoroc RC pipesPipe Pipe OD Pipe Length Hammer

sizeHole diameter Weight Inner tube ID

mm in mm ft mm in2 kg2 lbs mm inchM45 114 4½ 6 000 19.7 4½-5" 127-152 5-6" 198 436 49.2 1.94M45 114 4½ 4 000 13.1 4½-5" 127-152 5-6" 132 291 49.2 1.94M45 114 4½ 3 000 9.8 4½-5" 127-152 5-6" 100 220 49.2 1.94

DR115 114 4½ 6 000 19.7 4½-5" 127-152 5-6" 152 335 53.5 2.1DR115 114 4½ 3 000 9.8 4½-5" 127-152 5-6" 80 176 53.5 2.1

The Secoroc RC 50 reverse circulation drill stands for simplicity, performance and reliability.

AQuantumLeapcycleisincorporatedintotheRChammer, creating a high frequency hammer with world class performance and reliability. The Secoroc RC 50's high frequency enables it to perform well in all rock formations.TheQuantumLeapaircyclemaximizesefficiency and develops greater power for large or small compressor capacities. The air cycle utilizes a special poppet valve to drive air pressure to accelerate the piston tohigherenergylevels.Longevityandreliabilityaredueto a larger piston-struck end, a heat-treated collection tubeandtheuseoftheQuantumLeap-valvecycle.

Atlas Copco's reverse circulation hammers are specifically designed for both deep hole exploration drillingandin-pitgradecontrolapplications.Whetheryou are exploring potential sites or working an existing mine, you can be assured of high performance, exceptional reliability and dependable support.

Secoroc RC 50 reverse circulation hammer

Outside diameter 130 mm 5.13 in

Length without bit 1 152 mm 45.4 in

Length with bit extended 1 276 mm 50.2 in

Length with bit retracted 1 232 mm 48.5 in

Weight without bit 72 kg 158 lb

Spanner flat on tob sub 102 mm 4 in

Minimum recommended bit size 140 mm 5.5 in

Maximum recommended bit size 152 mm 6 in

Cylinder bore 113.7 mm 4.48 in

Piston weight 17 kg 38 lb

Stroke length 64 mm 2.5 in

Working pressure 10-35 bar 145-500 psi

Make up torque 6 800 Nm 5 000 ft-lb

Shank Secoroc RC50

Thread connection 4½"RemetBOX

Secoroc RC 50 bit assortment Drop centre, Extra flushing head design

Outside diameter, mm Outside diameter, in

140 5-1/2143 5-5/8146 5-3/4152 6165* 6-1/2*

*For setting casing

Secoroc RC 50 chuck sleeve assortmentOutside diameter. mm Outside diameter. in

132 5.2134 5.28137 5.4139 5.47140 5.52142 5.59144 5.65147 5.77150 5.9153 6157 6.2163 6.4

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Produced by: Atlas Copco Craelius AB, SE-195 82 Märsta, Sweden, tel +46 8 587 785 00, fax +46 8 591 187 82. Publisher: Daniel Misiano, Märsta, Sweden, [email protected] Editor: Mike Smith, tunnelbuilder ltd, Cardiff, United Kingdom, [email protected] Senior Adviser: Anders Gustafsson, Stockholm, Sweden, [email protected] Layout: Rafaella Turander, ahrt informationsdesign, Örebro, Sweden, [email protected]

Contributors: Anders Björk, Anders Gustafsson, Daniel Misiano, David Petersson, Fredrik Gabrielsson, Gerry Black, Hans Fernberg, Jan Jönsson, Lars Gellerhed, Magnus Ericsson, Peter Balen, Tom Ekström, all [email protected]. We also thank all contributors of editorial material for case stories.

Digital copies of all Atlas Copco reference editions can be ordered from the publisher, address above, or online at www.atlascopco.com/rock. Reproduction of individual articles only by agreement with the publisher.

Printed by: Prinfo Welins Tryckeri, Örebro, Sweden.

Legal notice

© Copyright 2010, Atlas Copco Craelius AB, Märsta, Sweden. All rights reserved. Atlas Copco is committed to comply or exceed all applicable laws, rules and regulations. Photos in this publication may show situations which complies with such laws, rules and regulations in the country where the photo has been taken but not necessarily in other parts of the world. In any case think safety first and always use proper ear, eye, head and other protection to minimize risk of personal injury.

This publication, as well as specifications and equipment, is subject to change without notice.

Consult your Atlas Copco Customer Center for specific information.

Excore - excellence in core drilling

An exploration contractor’s success is dependent upon the efficiency of the drilling equipment. To meet this demand, Atlas Copco has developed the new Excore™ diamond bit, which offers the latest in diamond drilling technology. Atlas Copco has combined scientific research and innovative new technology with more than 100 years of field experience to create a diamond bit that will revolutionize mining exploration. Excore™ is a faster drilling, longer lasting coring bit that performs in a wider range of drilling conditions and formations. This means fewer bits needed on the job site - both in operation and on the shelf and increased productivity throughout the entire operation - from purchasing to retrieving core. Excore™ from Atlas Copco is a series of diamond drill bits that is in the absolute top range of what is available today– a bit that stands for excellence, durability, speed and strength.

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The power within

Just as our coring drills explore deep inside the earth, so too dowe look within ourselves, constantly searching for improvementsto products and manufacturing processes. The result is the mostcomprehensive range of dependable exploration products to poweryou towards your goal.