minimum construction requirement water bore-aus

8/12/2019 Minimum Construction Requirement Water Bore-AUS

1/97

Edition 2Revised September, 2003

MINIMUM CONSTRUCTION REQUIREMENTS

FOR WATER BORES

IN AUSTRALIA


2/97contents

i

Groundwater has played a vital role in the development of many areas of Australia. The extensive usemade of groundwater resources stems from a number of factors. The resource extends over largeareas, making distribution costs more economic than from surface supplies. It is generally well-filtered, is mostly accessible at reasonably shallow depths, and the scale of development required can

be tailored closely to meet individual water demands.

Access to the resource is usually by bores or excavated wells. However, bores must be constructed toan acceptable standard using appropriate materials in order for this access to be achieved efficiently,cost-effectively and reliably without danger to the resource from pollution or overuse. It is estimatedthat over $6.6 billion has been spent on bore construction in Australia. For many individuallandholders the cost of constructing a water supply from bores represents a large proportion of theirtotal property investment.

It is important to both the nation as a whole and groundwater users that the very large investment inbore construction be protected by proper construction methods.

All States and Territories have introduced, or are about to introduce the national system of licensingwater bore drillers.

In order to underpin the skills levels on which the three classes of drilling licences are based, it isessential that there be a common reference standard for bore construction and that this standard beclearly defined and accepted by water licensing agencies and the drilling industry throughoutAustralia.

The purpose of this document is to provide such a reference as a technical basis and description of theminimum requirements for constructing water bores in Australia.

This document is a minimum guideline only. It must be recognised that special conditions mayrequire a higher standard to be applied to a particular bore.

This document draws on and is supported by a number of state and industry documents andstandards which are referenced in the relevant chapters.

Although the document is focused mainly at drillers and drilling contractors, it will also be of valueand use to water licensing agencies, consultants, consulting engineers and clients.

We urge you to become fully acquainted with the requirements set out in here.

Chair, Water Reform Task Group Chair, National Minimum BoreMember, Land and Water Biodiversity Committee Specifications Committee

FOREWORD

foreword


3/97contents

ii

This book is based on information available in September 2003.

It is available from the Queensland Department of Natural Resources, Mines and Energy Library, theState Library of Queensland and the National Library, Canberra, through interlibrary loan.

ISBN 1 9209 2009 9

QNRM04027

Land and Water Biodiversity Committee, 2003

Inquiries should be directed to the appropriate authorities listed on pages 7 and 8 of this publication.

The members of the National Minimum Bore Specifications Committee are:

Australian Drilling Industry AssociationAustralian Drilling Industry Training CommitteeDepartment of Environment, Western AustraliaDepartment of Infrastructure, Planning and Environment, Northern TerritoryDepartment of Infrastructure Planning and Natural Resources, New South WalesDepartment of Mineral Resources, TasmaniaDepartment of Sustainability and Environment, VictoriaDepartment of Water, Land and Biodiversity Conservation, South AustraliaQueensland Department of Natural Resources, Mines and EnergyWater Corporation, Western Australia


4/97contents

iii

TABLE OF CONTENTS

1.0 Introduction 1

1.1 Need for minimum bore construction requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Purpose of document . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.3 Types of water bores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.0 Administrative requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3.0 Responsibilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.1 Client responsibilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.2 Driller responsibilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.3 Joint responsibilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4.0 Drillers classification system and drilling methods used . . . . . . . . . . . . . . . . . . . . 11

4.1 Drillers classification system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

4.2 Drilling methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4.3 Choice of drilling method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

5.0 Siting a water supply bore. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

5.1 Obtaining information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

5.2 Driller considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175.3 Client considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6.0 Formation (strata) sampling and water sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

6.1 Formation sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

6.2 Water sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

7.0 Drilling fluids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

8.0 Plumbness and alignment of bores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278.1 Method of testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

9.0 Casing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

9.1 General considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

9.2 Types of casing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

9.3 Choosing casing type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

10.0 Grouting (cementing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

10.1 Decreasing the specific gravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

10.2 Increasing specific gravity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

10.3 Reducing setting time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

10.4 Increasing setting time. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37


5/97


6/97contents

v

Figure 1.1 Water monitoring bore (non-flowing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Figure 1.2 Low-yield bore (non-flowing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Figure 1.3 High-yield bore (non-flowing, screened and gravel packed) . . . . . . . . . . . 4

Figure 1.4 Flowing bore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Figure 8.1 Types of bore misalignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 8.2 Typical bore plumbness test assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Figure 11.1 Example of open-hole bore construction . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Figure 11.2 Examples of perforated and slotted casing . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Figure 11.3 Stacked set of sieves used to provide grain distribution curve . . . . . . . . 43

Figure 11.4 Example of sieve analysis report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Figure 12.1 Improving bore permeability through development . . . . . . . . . . . . . . . . . 49

Figure 12.2 Commencing development of a bore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Figure 15.1(a) Example of a drilling log (front of form) . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Figure 15.1(b) Example of a drilling log (back of form) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Figure 18.1 Requirements for decommissioning a flowing bore . . . . . . . . . . . . . . . . . 74

Figure 18.2 Requirements for decommissioning a single aquifer non-flowing bore . . . 75

Figure 18.3 Requirements for decommissioning a multiple aquifer non-flowing bore . . 76

LIST OF FIGURES

19.10 Gravel packing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

19.11 Sealing of annulus above or between monitored intervals . . . . . . . . . . . . . . . . . . . . . . 79

19.12 Centralising casing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7919.13 Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

19.14 Decommissioning bores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

A Definitions and metric conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

B List of references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

C Typical bore types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87


7/97contents

vi

Table 4.1 Drilling methods and their applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Table 6.1 National Water Quality Management StrategyAustralian Drinking Water Guidelines 1996 . . . . . . . . . . . . . . . . . . . . . . . . 21

Table 6.2 pH limits for various water uses (guidelines only). . . . . . . . . . . . . . . . . . . . . 22

Table 7.1 Suggested Marsh funnel viscositiesfor drilling unconsolidated materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 7.2 Recommended up-hole circulation velocities

and Marsh funnel viscosities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 9.1 Reactivity of steel casing to corrosive waters . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Table 9.2 Comparison of strengths of bore casing materials . . . . . . . . . . . . . . . . . . . . . 32

Table 9.3 Bore casing manufacturing standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Table 9.4 Minimum acceptable wall thicknesses for steel casing or steel tubes . . . . 33

Table 9.5 Maximum potential pressure differentialfor PVC bore casing (head difference) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Table 10.1 Recommended range of cementwater mixes . . . . . . . . . . . . . . . . . . . . . . . . . 37

Table 10.2 Recommended cementbentonitewater mixes. . . . . . . . . . . . . . . . . . . . . . . . 37

Table 14.1 Type and duration of pumping test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Table 15.1 Guidelines for soil classification and description . . . . . . . . . . . . . . . . . . . . . 61

Table 15.2 Guidelines for rock classification and description . . . . . . . . . . . . . . . . . . . . . 62

Table 17.1 Chemicals used in the treatment of bores. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

LIST OF TABLES


8/97

1

1.1 NEED FOR MINIMUM BORECONSTRUCTION REQUIREMENTS

Some twenty per cent of Australias totalwater use is from groundwater sources. Ingeneral this percentage is increasing as surfacewater sources become fully utilised andeconomics favour the use of groundwater.

Water bores are the most common means oftapping groundwater resources. The siting,design, materials and construction method usedin a bore all influence the quantity and quality ofwater obtained. The final bore 'product' is aresult of a range of considerations and decisions

which include the: intended purpose of the bore geological and hydrogeological conditions

including the groundwater quality drilling methods construction methods bore performance improvements (for example

bore development and disinfection) bore performance indicators (for example

pumping test and water quality test).

The final bore product is further influenced by the

inherent nature of drilling which disrupts thenative environment. Bores drilled to intersect ahydraulic regime (aquifer) will disturb that regime

by providing a vertical connection betweenaquifers of different head or groundwaterqualities. Where drilling intersects groundwaterheld under pressure, uncontrolled flowing(artesian) bores can result causing wastage of thegroundwater resource and the loss of hydrostaticpressure. All non-flowing bores can potentiallyprovide a means of contaminating groundwater

by acting as a conduit for surface run-off.

Encrustation and corrosion of bores affects boththe security of supply and the level ofgroundwater protection; this, in turn, affects howand what will constitute the bore product.

All bores have a finite life span. Deteriorated orabandoned bores which threaten the groundwaterresource should be decommissioned in such a waythat the hydrogeological environment ismaintained or returned as close as possible to thecondition that existed prior to drilling.

These minimum requirements aim to provide atechnical base for driller licensing, bore licensingand use by the drilling industry. The documentconsiders the design, materials and recordingaspects for bore construction. In doing so therequirements aim to ensure the: protection of the groundwater resource from

contamination, deterioration and unduedepletion, and the

long-term economic production ofgroundwater of the best possible quality.

Definitions of the various terms used are listed inAppendix A.

This document was originally prepared by asteering committee made up of representativesfrom all State and Territory Governments, theAustralian Drilling Industry Association and theAustralian Drilling Industry Training Committee,using information from Australia, and other partsof the world. It accessed industry referencematerials, as well as appropriate Australian andoverseas Standards.

This document has been reprinted following areview, which sought submissions from the

drilling industry. Reviews are conducted everyfive years.

A list of useful references is shown in Appendix B.

These requirements are not designed to meetthe specific requirements of landholders orpurchasers, or replace specifications currentlyused by various state water authorities.However, they may be included into specificdocuments.

The minimum requirements relate to the text

and clauses in the shaded blocks. All other textis general information only and is not part ofthe minimum requirements.

These minimum requirements have a broadscope. They deal with the whole life of thewater bore from tendering and licensing toconstruction, development and decommissioningfor shallow small-diameter and low-yielding

bores through to deep large-diameter and high-yielding bores.

chapter

1.0 INTRODUCTION


9/97

2

1.2 PURPOSE OF DOCUMENT

The purpose of this document is to provide a

technical basis for and description of theminimum requirements for constructing water

bores in Australia. It both complements andunderpins the national drillers licensing system

by providing a bore construction standard whichis consistent across Australia.

Although its use is focused mainly at the waterdrilling industry, it should also be of interest toanyone intending to construct a water bore.In prescribing the minimum acceptableconstruction requirements, it is not intended to

be viewed as a substitute for formal training.

Drillers play a vital role in the development, useand protection of the groundwater resource.They supply a service to clients and in so doinghave a responsibility to ensure that this role isfulfilled through high standards of work and theuse of materials appropriate to the particularworks involved.

1.3 TYPES OF WATER BORES

The type of bore used to obtain a water supplydepends on a number of factors which include: flowing (artesian) or non-flowing

(subartesian) source the potential or desired bore yield single or multiple aquifers system the stability of the strata the grain size of the aquifer material whether the bore is to be used for monitoring

or production purposes.

There are numerous combinations of these whichresult in the many types of bore necessary, a

number of which are shown in Appendix C.

The following describes some of the differentconstruction requirements for single, multipleand flowing aquifer systems.

The minimum requirements for each of thecomponent parts of their construction aredetailed in subsequent chapters.

1.3.1 Single aquifer non-flowing bores

(a) Monitoring bores

Monitoring bores are normally of small diameterand drilled specifically to obtain accurateformation samples and are then equipped andused for the sole purpose of taking watersamples and/or monitoring water levels.

The basic characteristics are 50100 mm casingslotted and/or screened, normally of low-yieldconstruction but providing for accurate waterquality sampling and water level measurementsfrom a particular zone of interest within anaquifer. Annulus seals and selective filterpacking are used where necessary to isolate thezone being monitored.

Care must be taken during drilling operationsand in selecting the drilling method to ensurethat there are no contaminants introduced thatmay affect the monitoring/sampling results.Casing, filter pack and sealing or groutingmaterials should similarly be selected so thattheir chemical properties have minimal or noeffect on the proposed sampling requirements.An example of monitoring bore construction is

shown diagrammatically in Figure 1.1.

(b) Low-yield bores

Low-yield bores are the most common andnumerous type of bore and therefore drilling ofthese bores tends to be competitive and ofrelatively low cost.

The drilling priority is usually to obtain a usablesupply of water for livestock watering and/ordomestic use. Such bores normally use casing ofsome 100150 mm diameter to contain costs.

It is most important however that the bores beconstructed to an adequate standard becausethey are often the only source of permanentwater available for a property.


10/97

3

Figure 1.1 Water monitoring bore (non-flowing)

The basic requirements for these bores are: construction technique and water entry

selected to allow long-term production ofclear silt-free water

adequate bore straightness to allowinstallation and reliable operation of theclient's preferred pump

use of proper bore casing of acceptablestandard and suitable materials

effective isolation of the main productionaquifer from thief zones (lateral leakage),aquifers of poorer quality and intrusionthrough surface runoff and or seepage ofcontaminants or pollutants

a usable supply of water of acceptable quality.

Any shallow water beds of poor-quality watershould be excluded from the bore. Potential surfacewater runoff or shallow subsoil seepage should also

be excluded and sealed from bore entry.

An example of a non-flowing bore of low yield ina consolidated aquifer is shown in Figure 1.2.

(c) High-yield screen and gravel packed bores(unconsolidated formation)

The major objective when drilling a high-yieldbore is to ensure that the formation remains stableand capable of being pumped at the maximumefficient water yield with immunity from

contamination, particularly from the surface.

To achieve this result a test hole drilling programis usually carried out to locate the optimumproduction bore site.

The same criterion used for low-yield boresapplies to high-yield bores in regard to possiblecontamination or pollution.

The surface casing should be sealed to preventsurface runoff and subsoil seepage entering the

bore annulus.

Figure 1.2 Low-yield bore (non-flowing)


11/97

4

Other important factors which must beconsidered include: selection of a casing size based on the desired

or potential yield and the required pump size selection of screen length appropriate to the

aquifer thickness being screened choice of gravel pack size based on analysis of

the gradation of the aquifer materials selection of a screen slot aperture

approximately 20 per cent smaller than thegravel pack modal size

selection of a screen diameter and length that willtransmit the bore yield at low entrance velocities

selection of a hole diameter large enough toallow a gravel pack thickness of 50 to 100 mm

selection of a gravel pack material that is wellrounded and clean.

It is important in constructing a high-yield borethat the long-term stability and efficiency ofoperation are not compromised by imprudentcost savings.

An example of high-yield bore construction isshown in Figure 1.3.

1.3.2 Multiple aquifer non-flowing bores

(a) Monitoring bores

When a single bore is required for the monitoringof multiple aquifers of differing water quality,yield or pressure, it is drilled with a largerdiameter to allow the insertion of two or moreseparate strings of small-diameter casing.

As with all monitoring work, care should betaken with design, materials selection, anddrilling/installation methods to ensure that water

samples are not contaminated. Extra care isrequired with the placement of annular seals

between aquifers to ensure that representativesamples of each zone of interest can be obtained.

The usual method of construction is to drill andsample the hole to full depth first, carry out anylogging work to help define potential aquifersthen slot and/or screen the first or deepest setcasing string and run it into the hole. Gravel isthen placed around the slots through the loweraquifer up to where the first annular seal isrequired. A tremie pipe is then run and the

between-aquifer annular seal is set. The tremiepipe is withdrawn and the second casing stringrun and gravel packed. If there is little distance

Figure 1.3 High-yield bore(non-flowing, screened and gravel packed)

between aquifers and the hole is reasonablystable the annular seal is sometimes leftovernight to set before the second casing string isgravel packed.

This procedure is then repeated for anysubsequent casing strings. Experience has shownthat it is sometimes quicker and more secure todrill multiple holes if room permits as any

drilling time saved with a single hole can betaken up with the setting of multiple casingstrings and annular seals.


12/97

5

(b) Low-yield bores

Often the top or upper aquifer in an area is saline

or of poor quality or may be fully committed toother users.

Bores in these cases are drilled through the upperaquifers to allow tapping of the better loweraquifers.

The bores are drilled to full depth with carefulsampling for quality and testing for yield asdrilling progresses so that the bore can becompleted to yield the most suitable water. Anyunsuitable waters are excluded from the bore

during casing by slotting or screening only theselected aquifer. Annular seals are then set abovethe slots or, if necessary to protect steel casingfrom possible corrosive waters, grouting of thecasing to the surface is carried out.

Care must be taken to ensure waters of differingquality or pressure cannot mix either in the borecasing or in the annulus between casing and

bore hole.

Sometimes two or more aquifers may bepenetrated before the selected aquifer and in

these cases it is often easier to ensure there is nopossible mixing of waters by grouting theannulus from the production aquifer to surface.

(c) High-yield bores

The completion of a high-yield, large-diameterbore usually requires a large drilling rig and anexperienced driller and may require two or morestrings of casing for deeper bores.

The aim is to construct the bore to allow efficientpumping from the selected aquifer at maximum

yield but prevent mixing of waters from otheraquifers penetrated.

1.3.3 Flowing bores (artesian)

The drilling priority for artesian boreconstruction is the control of artesian pressureand flow.

The requirements for an artesian bore include theprotection of production casing from corrosivesoils and prevention of discharge up the outsideof the casing by the setting and cementing ofsurface control casing, then prevention ofintermixing of waters of different quality orpressure from one aquifer to another, tapping ofone primary aquifer only, and the control offormation pressures by selective cementing of theproduction casing. During the selection processfor production casing and headworks materials,consideration must be given to the depth ofinstallation, grouting pressures, well head staticpressure and water temperature together withthe corrosive nature of the water and strata.

Bores must also be fitted with headworks ofapproved design to permit the control of flow,and for periodic maintenance and measurement.These approved headworks must have provisionmade for flow and pressure to be measuredwithout having to disconnect or interfere withreticulation or surface pumping systems.

Because of the high costs involved, few artesianbores are drilled for monitoring purposes only.

The monitoring of artesian bores is usually

carried out by the licensing agencies and involvesa series of measurements, at regular intervals, offlow, pressure, temperature and water quality ona set of selected representative bores.

The construction requirements for artesian borestapping the Great Artesian Basin (GAB) varyfrom state to state, and can be different to theminimum requirements described in thisdocument. Local licensing authorities should beconsulted concerning artesian bore constructionrequirements before drilling in an artesianaquifer of the GAB.

In artesian aquifers outside of the GAB,alternative construction requirements may beapproved by the licensing authority to meet thelocal requirements.

An example of the construction for a flowingbore is shown in Figure 1.4.


13/97

6

Figure 1.4 Flowing bore


14/97

7

chapter

2.0 ADMINISTRATIVE REQUIREMENTS

The following general legislative provisionsand policies are enacted by water agenciesin each of the States and Territories. Because therelevant legislation varies between authorities,

drillers, consultants and clients must becomefully conversant with the requirements of theState in which they intend the work beundertaken.

MINIMUM REQUIREMENTS FOR DRILLING OPERATIONS

R2.1 Driller. Unless state or territory legislation provides an exemption, only drillers licensedfor the class of work proposed and endorsed for the construction method to be used maycarry out work on a water bore. This includes the construction, reconditioning,decommissioning by plugging or other work as specified. The licensed driller must be on siteat all times during such operations. It should be noted that it is the individual driller who islicensed, not drilling companies.

R2.2 Works. Where necessary, the owner or legal occupier of the land on which a bore is tobe constructed must obtain the appropriate licence or permit from the licensing authority inthe relevant State or Territory. Work must not commence on a bore until such approval has

been granted.

A driller must sight the licence or permit before commencing any work and be aware of theconditions relating to the particular bore. The licence or permit will stipulate the nature of thework that has been approved. It may also stipulate the reporting requirements.

The following is a list of government agencies inAustralia and driller associations from whom

further information may be obtained in regard tothis document or drilling requirements generally.

Western Australia

Water CorporationPO Box 100LEEDERVILLE WA 6007

Department of EnvironmentPO Box 6740Hay St,EAST PERTH WA 6892

South Australia

Department of Water, Land and BiodiversityConservation Drilling ServicesPO Box 219INGLE FARM SA 5098

Resource AssessmentPO Box 2834ADELAIDE SA 5001

VictoriaSouthern R.W.A.PO Box 153MAFFRA VIC 3860

Goulburn Murray R.W.A.PO Box 165TATURA VIC 3616

Wimmera Mallee R.W.A.PO Box 56HORSHAM VIC 3402

New South Wales

Department of Infrastructure Planning andNatural ResourcesGPO Box 39SYDNEY NSW 2001

Queensland

Department of Natural Resources, Mines and EnergyPO Box 156MAREEBA QLD 4880

Northern Territory

Department of Infrastructure, Planning and

Environment Natural SystemsPO Box 30PALMERSTON NT 0831


15/97

8

Tasmania

Mineral Resources Tasmania

PO Box 56ROSNEY PARK TAS 7018

Industry

Australian Drilling Industry Association LtdPO Box 3020FRANKSTON EAST VIC 3199

Australian Drilling Industry Training CommitteePO Box 742LANE COVE NSW 2066


16/97

9

chapter

3.0 RESPONSIBILITIES

providing the client with regular and timelyreports of progress, and any other informationthat may be relevant to the work and its cost

ensuring, where legislation requires, that theclient holds a current Waterworks or BoreLicence for the type of bore being constructedand that the driller is conversant with theconstruction requirements, depth and aquiferlimitations contained therein

providing the client and the water licenceauthority with a written log of each bore's details

providing advice on the flow and quality ofwater on completion of a bore

leaving the site in a clean and tidy mannerand free from contamination.

Note: a driller cannot warrant or guaranteequantity or quality of water before drilling iscarried out.

3.3 JOINT RESPONSIBILITIES

The type and nature of bore construction shouldbe discussed fully between the driller and thebore owner before the work commences.The following should be taken into account:

legislative requirements (including Stateoccupational health and safety legislation)

protection of the aquifer materials required the desired yield or purpose of the bore known geological conditions the desired life and future maintenance of the

facility costs duration of contract provision of detailed strata logs, strata

samples and water samples as specified by therelevant licensing agency

preferred pumping equipment and powersource options.

The construction of a bore can often be a veryimportant development resulting in a vitaland valuable source of supply to a property,town or project.

The client, or a representative, should be on sitefor a substantial amount of the constructionperiod or at least be readily contactable whenabsence is necessary. The client should also be

made fully aware of the more critical phases of

When a bore is to be constructed both thedriller and client are responsible forvarious aspects of the work. It is in the interest of

both parties that a written agreement or contractbe entered into detailing all aspects of the workto be performed.

The following is a general guide to theresponsibilities of driller and client. It isemphasised that some responsibilities relate tolegislative requirements which vary betweenlicensing authorities. When in doubt, therespective agency should be contacted at theaddress shown in Chapter 2.

3.1 CLIENT RESPONSIBILITIES

In general the client has the followingresponsibilities: obtaining the necessary licence or permit to

construct the bore and comply with the borelicence conditions

selecting and if necessary preparing or clearingthe site, often in consultation with the driller

providing access to the bore site(s) submitting reports and water samples to the

relevant authority where required arriving at a written agreement/contract with

the drilling contractor on the work to becarried out and materials to be supplied

ensuring, where legislation requires, that thedriller holds a current Drillers Licence for theclass of work and drilling method employed

seeking advice on likely availability of watersupply and its quality.

3.2 DRILLER RESPONSIBILITIES

The driller generally has responsibility for: providing the client with accurate and

competent technical advice on the work providing references offering warranty on completed and tested

works including materials and the quality ofwork undertaken

providing the client with a written quotationfor work to be performed and materials to

be supplied ensuring the quantity and quality of materials

used are suitable for the job

the standard of work and deciding theconstruction method used


17/97

10

construction of the bore. Differing geologicalformations encountered may present difficulties

that even the most experienced driller could notanticipate, and may require consultation withthe client.


18/97

11

Under the national system of drillerslicensing, there are three classes of licenceand endorsements for four basic drillingconstruction methods.

The class of licence relates to the skill levelrequired to construct bores in different types ofaquifer systems, while the endorsements relate tothe drilling and construction methods which adriller is licensed to use.

4.1 DRILLERS CLASSIFICATION SYSTEM

4.1.1 Licence classes

Class 1 This licence is restricted to drillingoperations in non-flowing (sub-artesian)single aquifer systems.

Class 2 This licence, in addition tooperating in Class 1 conditions, permitsoperations in non-flowing (sub-artesian)multiple aquifer systems.

Class 3 This licence, in addition tooperating in Class 1 and Class 2 conditions,permits drilling operations in flowing(artesian) aquifer systems.

4.1.2 Drilling endorsements

Cable tool This endorsement permitsdrilling operations using cable tool or cablepercussion drilling methods.

Auger This endorsement permits drillingoperations using bucket auger, hollow-stemauger and solid-stem auger techniques.

Rotary air This endorsement permitsdrilling operations which use rotary drilling

methods with air or foam as the drilling fluid.This endorsement also includes the use ofdown-hole hammers.

Rotary mud This endorsement permitsdrilling operations which use rotary drillingmethods with water as the drilling fluid or asthe base for the drilling fluid.

Non-drilling rig This endorsement coversoperations such as spear points etc.

4.1.3 Required skills, experience

and abilitiesClass 1 licence: The holder of a Class 1 DrillersLicence must be capable and have knowledgeand skills, as they apply to the drilling methodendorsement, in:

chapter

the provisions of the legislation and regulationsrelating to groundwater and groundwaterdrilling; and understanding and appreciationof bore construction licence applicationprocedures and licence conditions

siting a bore recognising potentialcontamination sources to water supply boresand appropriately siting a bore to preventcontamination and meeting the locationrequirements of the bore licence

straightness and plumbness of hole setting upa rig, the causes of bent bores and themethods of hole straightening

drilling correctly choosing and usingequipment, having regard to such factors as

rotational speed and proper annular velocities fishing tool string inventories, fishing tools

and procedures formation sampling and description obtaining

representative formation samples, andlabelling and describing them

bore design designing and constructingbores for domestic use, stock watering andhousehold irrigation purposes in singleaquifer systems

construction seating and sealing of casing,casing types and their limitations and uses,

and completion of the bore site cementing grouting surface casing anddecommissioning (abandoning) bores or testholes

setting screens and stabilising gravel fillselecting the appropriate slot size, screenlength and diameter, and procedures forscreen installation in low-yield bores

bore development basic knowledge ofdevelopment techniques

disinfection procedures basic knowledge ofdisinfection procedures and safe chemicaldisposal

aquifer testing and water sampling carryingout a single stage pumping test, anddetermining and recording static water level,drawdown and yield; taking and labelling awater sample

decommissioning designing and selectingappropriate materials for thedecommissioning (abandonment) of bores insingle aquifer systems

bore completion reports correctly filling in adrill log or other required bore reports foreach bore or test hole

construction standards all bores constructedunder this class of drillers licence must beconstructed to meet the relevant minimumstandards requirements set out in this document.

4.0 DRILLERS CLASSIFICATION SYSTEMAND DRILLING METHODS USED


19/97

12

Class 2 licence: The holder of a Class 2 licencemust have the knowledge and skills required of aClass 1 driller together with knowledge andskills, as they apply to the drilling methodendorsement, in: bore design designing and constructing

bores in multiple aquifers with emphasis ondesigns and methods used to excludeunsuitable waters including the use of inertplastic and other nonferrous casings

screen setting and gravel pack selection skill inthe design of high-yielding bores is required.This entails overcoming entrance velocityproblems and carrying out sand sieve analysisin order to select appropriate gravel pack

material and screens (that is screen length,diameter and aperture)

cementing grouting casing, placing cementplugs over selected zones, effect of cementadditives; ability to calculate hole volume,slurry volumes and specific gravities; holepreparation, casing installation andcirculation requirements

aquifer testing the procedures involved anddata required from a multistage pumping test

decommissioning designing and selectingappropriate materials for the

decommissioning or abandonment of bores inmultiple aquifers construction standards all bores constructed

under this class of driller's licence must beconstructed to meet the relevant minimumstandards requirements set out in thisdocument.

Class 3 licence: The holder of a Class 3 licencemust have the knowledge and skills required of aClass 1 and Class 2 driller together withknowledge and skills, as they apply to thedrilling method endorsement, in:

drilling fluids methods, procedures andcalculations required for formation fluidpressure control

cementing methods and procedures andcalculations required in carrying out pressurecement jobs

bore design in aquifer systems that havehigh-pressure conditions; design of efficient

bores in corrosive water areas; use of inertplastic and other nonferrous casing

headworks design, fabrication and fitting ofsuitable bore flow control and remeasurement

headworks construction standards relevant bores must

be constructed to meet the minimumstandards requirements set out in thisdocument.

4.2 DRILLING METHODS

Drilling methods are many and varied, ranging

from simple digging with hand tools to high-speed drilling with sophisticated equipment.The most commonly used methods are described

briefly below for the general information ofreaders who do not have a drilling background.

4.2.1 Cable tool drilling

Cable tool drilling, otherwise known as percussiondrilling, is probably the oldest drilling method.

Basically it involves the lifting and dropping of a

string of solid steel drilling tools suspended froma wire rope, which hit the bottom of the hole.This process drives the cutting bit,fracturing or pulverising the formation. Thecrushed material forms a slurry on mixing withwater that is either added or naturally present inthe hole. The blow rate varies from 40 to 60strokes per minute and due to the characteristiclay of the wire rope cable, the bit turns andstrikes across a different section of the hole

bottom at each blow.

When the bit can no longer fall freely through the

watercuttings mix, the drill tools are withdrawnfrom the hole. A tubular bailer, which is run on aseparate smaller wire rope, is then used to pickup the slurry and cuttings and remove them fromthe hole before drilling is resumed.

In cable tool or percussion drilling there arebasically three major operations:(i) the drilling of the hole by chiselling or

crushing the rock, clay or other material bythe impact of the drill bit

(ii) removing the cuttings with a bailer as

cuttings accumulate in the hole(iii) driving or forcing the bore casing down into

the hole as the drilling proceeds.

Cable tool drilling rig


20/97

13

Because of the relatively low initial cost andsimplicity of the equipment used, cost per unitdrilled is relatively low. However, the techniqueis slow and when the increased cost of labour istaken into account, there is usually little netadvantage over faster rotary drilling methods inthe drilling of new bores.

Cable tool drill plants are used extensively forreconditioning work. They are usually smallerthan a rotary plant with an equivalent depthcapacity and therefore easier to establish over a

bore hole. They can also lower and retrieve toolsto probe a bore more quickly than with a rotaryplant and are able to work inside casings and

insert casing liners more quickly due to theirbetter access around casing strings for screwingor welding a joint.

4.2.2 Auger drilling

Auger drills are used mainly for soilinvestigation and drilling in soils and very softrock. The mechanical clearing of the holeeliminates any need for pumps or compressors.

Continuous-flight augers can be driven by anytop-drive rotary machine provided it has

adequate torque rating and slow rotation.

In deep, small-diameter holes using continuous-flight augers, cuttings are supported by the holeand carried to the surface by rotation of thehelical flights.

Hollow augers consist of a continuous-flightauger which has a hollow centre tube. They arenormally used with a bit plug held in place by asecondary internal rod string with the augersused to drill as with a conventional continuous-

flight auger to the required depth. At that pointthe central bit plug and rod string is withdrawn.

Short-flight and plate augers are loaded withcuttings and then pulled out of the hole. At thesurface the cuttings are 'spun' off the auger.

With bucket augers the cuttings are picked up ina bucket, hoisted to the surface and dumpedthrough the hinged bottom of the bucket.Extensions are added as the hole gets deeper.

Short-flight, plate and bucket augers are used for

shallow, large-diameter holes.

Rotary air drilling rig

4.2.3 Rotary air drilling

This method is used to drill holes in consolidatedor semi-hard formations such as sandstone orshales which are self-supporting. The principlecommon to all rotary techniques is that a drill bitis attached to the end of a hollow drill pipe androtated against the bottom of the hole,thereby imparting either a fracturing, digging orscraping action, depending on the bit type andthe nature of the formation. Pressure is appliedto the bit by the weight of the drill pipe andadditional weight (feed) is also applied from thedrill plant. The cuttings produced by this processare cleared by circulating air, which is derivedfrom a compressor and fed down the drill pipe toemerge through a bit.

To remove cuttings effectively an annularvelocity of at least 900 metres per minute isnecessary. Compressor output, hole diameter

and drill pipe size should be matched to providevelocities of this order.


21/97

14

Mud rotary drill rig

Holes can be drilled to depth using a largevolume of air at high pressure. However, the

equipment normally used is limited in depthonce below water level.

Two general types of bit are used. These are theroller-cone type, usually called a rock bit, andthe drag type, of either a fishtail design or thewing insert bit of three- or four-piece design.

A major advantage of the rotary air drillingmethod is that water is blown to the surface assoon as the water bearing stratum isencountered. This allows the driller to obtain aprogressive indication of the available supplyand monitor any changes in the quality andquantity of water as the drilling progresses.

Air is used principally in hard clay or rockformations, because once the air pressure isturned off, loose formations tend to cave inagainst the drill pipe. Foaming additives areoccasionally used to increase the up-holecarrying capacity of the return air.

Down-hole hammer method The down-holehammer method involves a pneumaticallyoperated special bottom-hole drill bit thatefficiently combines the percussion action ofcable tool drilling with the turning action ofrotary drilling. The pneumatic drill can be used

on a standard rotary rig with a high pressure aircompressor of sufficient capacity. It is used for

fast and economical drilling of medium toextremely hard formations. Fast penetrationresults from the blows transmitted directly to the

bit by the air piston. Continuous hole cleaningexposes new formation to the bit and practicallyno energy is wasted in redrilling old cuttings.Down-hole hammer drilling is generally thefastest method of penetration in hard rock. The

bit is turned slowly (515 rpm) by the samemethod by which the drill bit in the fluid or airdrilling operation is rotated. Foaming additivesare occasionally used to increase the up-holecarrying capacity of the return air. The down-hole hammer has revolutionised hard rockdrilling and has enabled water bores to beestablished from rock aquifers previouslyregarded as being too hard to drill. The methodis not recommended for drilling loose,unconsolidated materials.

Reverse circulation drilling method air(dual tube rotary air and down-hole hammer)For this drilling method, air is introducedthrough a dual swivel head on a top drive rotaryrig and pumped down the annulus in the dual

drill pipe to the bit or hammer being used.Cuttings are returned to the surface through theinner tube. This method is used primarily formineral sampling to obtain an uncontaminatedstrata sample. However, it can also be used for

Rotary mud drilling


22/97

15

water sampling programs. Large-diameter dualtube rotary air drill strings permit the insertion ofup to 50 mm PVC casing through the inner tubefor the construction of monitoring bores. It is nota common method for water bore construction.

4.2.4 Rotary mud drilling

Rotary mud drilling functions on the sameprinciple as air drilling except that the circulationmedium is aqueous. The technique wasdeveloped for handling soft, unconsolidatedformations which would collapse if air was used.The mud forms a membrane which inhibits flowthrough the walls of the hole. The internal

pressure of the mud provides structural supportto the hole wall. Drilling fluids are also used fordrilling deep bores which are beyond thecapacity of air compressors.

In the rotary mud system, drilling fluid or mud ispumped down through the drill pipe and outthrough nozzles in the bit.

The cuttings are removed by continuouscirculation of a drilling fluid as the bitpenetrates the formation material. The fluid

also serves to cool and lubricate the bit. Themud fluid then flows upward in the annularspace around the drill pipe to the surface,carrying the cuttings with it in suspension. Atthe surface, the fluid is firstly channelled into asettling pit, where most of the cuttings settleout, and then into a storage pit, where the mudpump picks it up again for recirculation.

The basic fluid normally used for rotary drillingis water to which specific chemicals and otheradditives can be added to increase density orviscosity to improve hole support. The fluid canalso be weighted to control artesian pressures.

Reverse circulation drilling method mud In thereverse circulation drilling method, instead ofcirculating the drilling fluid through and up theoutside of the pipe, the process is reversed. Fluidis fed down through the space between the wallof the hole and the drill pipe where it is thenpumped up, together with the cuttings, throughthe hollow part of the pipe and then out througha discharge pipe. Of particular importance is thepossible use of a light (nearly clear) drilling fluidfor large diameter holes rather than a viscous andheavy drilling mud as used in conventionalrotary mud drilling which sometimes tends toseal-off water-bearing formations. However, asubstantial quantity of fluid must be on hand to

maintain an open hole.

This method is used for rapid drilling of large-diameter holes in soft formations where gravelsare encountered. It is possible to bring gravel tothe surface through the hollow drill pipe becauseof the extremely high velocity of the fluid as it isdrawn up by the suction pump. The walls of thehole are held in place by the pressure of the fluidagainst the sides of the hole.

4.3 CHOICE OF DRILLING METHOD

Each of the common drilling methods has itsadvantages and disadvantages. The choice ofdrilling method employed should be made onthe basis of geological conditions and the type offacility to be constructed.


23/97

16

Type of Cable Auger* Rotary air Rotary mud High-pressureformation tool drill rotary air with

down-holehammer

Dune sand Slowfair Fair Difficultslow Suitable (with good Not suitableSand (if casing driven) Not suitable (Fair with foam fluid control)

and/or mud used below water table injection)

Loose sand Difficultfair Not suitable Difficult not Suitable (with fluid Not suitable& gravel (if casing driven) suitable control) Fair (see note)

Loose coarse Difficult slow (but Not suitable Not suitable Difficultslow Not suitablegravels & boulders generally can be sometimes impossible Fair (see note)

handled if casing driven)

Loam and silt Suitable Fair Fair Suitable Not suitable

Sandy clay Suitable Fair Suitable (drag bits) Suitable Fair

Puggy shale Fair Slow Fair (water injection) Suitable Slow & mudstone (water injection)

Shale Suitable Fair Suitable Suitable Fair

Sandstone Suitable Slow Suitable Suitable Suitable

Conglomerate Slow Not suitable Fairslow Fairslow Fair (if (rock bits) (rock bits) consolidated

formation)

Limestone & Slow Not suitable Fair (rock bits) Fair (rock bits) Suitabledolomite

Limestone with Fair Not suitable Fair (rock bits) Fair (rock bits) Suitablesmall cracks or

fissuresCavernous Fairslow Not suitable Fair (circulation Not suitable Fair (circulationlimestone problems) problems)

Weathered basalts Fair Slow Suitable Suitable Suitable

Thick layered Very slow - not Not suitable Fair (rock bits only) Fair (rock bits only) SuitableBasalts suitable

Metamorphic rocks Very slow not suitable Not suitable Fair to slow Fair to slow Suitable(rock bits) (rock bits)

Granite Very slow not suitable Not suitable Slow (rock bits only) Slow (rock bits only) Fairsuitable

LEGENDNot suitable : Normally cannot drill formation type.Difficult : Generally not suitable but can sometimes be adapted.Slow : Can be used but drilling progress is usually slow.Fair : Suitable with some care and/or special technique suggested thus.

Suitable : Normally used to drill formation type economically.

Note : Fair if top drive rig using hammer and swing out reamer and casing following bit.

* : Auger drilling requires high torque for rotation so depth is limited.

Table 4.1 Drilling methods and their applications

MINIMUM REQUIREMENTS FOR DRILLING OPERATIONS

R4.1 Drilling operations shall comply with relevant State or Territory Workplace Health andSafety Regulations.

R4.2 Drilling equipment shall meet any State or Territory inspection and certification requirements.

R4.3 Drillers should not contract for or attempt works which could be reasonably expected toexceed the depth, diameter or casing load rating of the drill plant to be used.

R4.4 Quality assurance procedures may be required.


24/97

17

chapter

5.0 SITING A WATER SUPPLY BORE

The siting of a bore usually involves theconsideration of a range of factors in thecourse of providing a cost-effective and reliablesupply of water of acceptable quality.

5.1 OBTAINING INFORMATION

The initial location selection and investigation arevery important in the overall construction andperformance of a bore. The depth, cost and relativeimportance of a production bore will usuallydictate the amount of investigation required.

Most licensing authorities can provide

information, advice and, if required, give anassessment of groundwater availability in aspecific area of interest. This could include dataavailable on any previous drilling work in anarea and other geological and geophysicalrecords. Depending on the extent of the workrequired to provide the assessment, a charge maybe made for providing this service.

Local information may also be available fromother drillers and neighbouring landholders.This could include the location, depth to water,amount of water pumped, type of water bed orformation, and water quality.

5.2 DRILLER CONSIDERATIONS

If a driller has worked consistently in an area it isprobable that he has a knowledge of theconstruction, depth, quality and yield of bores inthat area. However, the client has access to boreinformation which is held by State licensing andwater authorities.

The driller should have an understanding of theknown hydrogeological conditions of the area sothat a determination can be made of whether thedrilling equipment available can do the job.

Provisions relating to licensing vary betweenauthorities; drillers must become conversant withthe requirements of the particular area in whichthey operate.

5.3 CLIENT CONSIDERATIONS

The client should seek advice from the relevantwater authority so that the best site for the borecan be determined.

Siting the bore

The client should advise the driller if there are

any underground or overhead services in thearea of the proposed drill site.

The positioning of a bore should be based on thebest prospects for obtaining a successful supplyand on working convenience.

Consideration of other requirements may berequired if the pump is to be solar- or wind-powered. A cleared area might be preferable ifsuch pumps are to be used. State and local lawsand planning schemes might limit or control the

ways in which vegetation or timber can becleared, and should be checked prior toundertaking any clearing for a bore site.

The production bore site should allow readyaccess for heavy machinery for drilling andsubsequent servicing of the bore and pumpingequipment.

Some licensing authorities may have a borelicence or permit condition that requires that abore should be located not less than a specified

distance from the property boundary and/or froma bore on a neighbouring property, channel,stream, or source of pollution such as a septictank. This requirement is to minimise thepossibility of interfering with the flow and waterlevels in nearby bores.


25/97

18

MINIMUM REQUIREMENTS FOR SITING A BORE

R5.1 Distance condition: The driller shall not commence construction of a bore if its locationdoes not comply with a distance condition specified in the bore licence.

R5.2 Sources of contamination: All bores shall be positioned away from the influence of anypossible sources of contamination such as a dairy, septic tank and absorption trench, refusedump, land fill, effluent discharge (piggery or feedlots, sewerage treatment discharge), drainageditch, cattle/stock dip or chemical spray use/preparation area. In bores where the target aquiferis deeper than the source of the pollution, the bore may be constructed providing thecontaminated formation is adequately cased and cement sealed before the target aquifer isencountered. If the driller has any doubts concerning the potential problems and therequirements for a particular situation, advice should be sought from the relevant licensing orlocal authority.

R5.3 Protection of headworks: All bores or wells should be positioned so that the headworkscan be protected from frequent flooding and surface water drainage. If the bore has to belocated in an area of potential flooding, the casing should be raised above flood level or if this isnot feasible, completely sealed to prevent the entry of flood water. Temporary caps should befitted to all bores during the period from completion to pump installation to ensure foreignmatter does not enter the bore.

R5.4 Access to site: Access to a site and work to be carried out should be planned andconducted in such a manner as to minimise damage to property improvements, crops, land,drainage works and roads.

R5.5 Overhead power lines: Prior to commencement of drilling, the driller must contact thelocal electricity/power supply authority to obtain advice on the minimum clearance distancesbetween the drilling rig and overhead power lines. This information should be supplied, as faras practical, in written form.

R5.6 Underground/overhead services: The driller shall check with the client that nounderground or overhead services are located within the area of the proposed bore sites.


26/97

19

chapter

6.0 FORMATION (STRATA) SAMPLING AND WATER SAMPLING

Formation and water sampling are carried outto determine the nature and type of stratabeneath the site and the water quality in anywater bearing formation.

6.1 FORMATION SAMPLING

Reliable information on specific geologicalmaterials and aquifer conditions at a site isnecessary to establish the optimum design forvarious elements of a final production boreincluding the casing size and length, apertureof the bore screen, and the gradation of thegravel pack.

MINIMUM REQUIREMENTS FOR FORMATION SAMPLING

Laying out samples of drill cuttings

Geophysical logging equipment can also be usedand is recommended to confirm drilling depthsand strata details. It can also provideinformation on the porosity of formation, claycontent, the integrity of the borehole and the bestproduction zones within the aquifer sequence.

6.2 WATER SAMPLING

Knowledge of the quality of water encounteredas a bore is being constructed is highly desirableand, in some instances, imperative, because it canaffect decisions regarding continuedconstruction, selection of materials, and

modifications in construction or in the plannedoperation of the completed bore.

R6.1 Frequency of sampling: Formation samples shall be taken at least every three metres,and if required, bagged and delivered as specified in the bore licence or permit. Particular careshould be taken when collecting samples from expected water producing zones. Samples ofwater beds shall be taken at one metre intervals.

R6.2 Collection and marking: Samples required for collection shall be collected as soon aspossible after being withdrawn from the hole, drained of excess moisture and kept in plasticbags, or other containers of at least 500 g capacity for each interval drilled. Containers shall beplainly marked with the bore number and depth interval.

R6.3 Arrangement of samples: Samples, whether required for collection or not, shall be laidout on regular lines so that both the driller and client can see the formation changes.

R6.4 Where there is no licence requirement for samples they shall be taken at each change information and the depth recorded so that a reliable drilling log can be completed.


27/97

20

Common examples of water quality-relatedproblems are: water zones to be excluded bycasing or grouting; choice of casing material;selective casing perforation; selection of screenmaterials; screen setting; and the installation andoperation of water conditioning equipment.If water is to be used for domestic consumptionboth chemical and biological analyses arenecessary as recommended by the relevantgovernment agency. If the water is to be used forirrigation or for a special purpose, furtheranalysis to determine its suitability is advisable.

Wherever possible water sampling and testingprograms should be carried out under Quality

Assurance guidelines.

In order to determine the chemical constituentsof waters in various aquifers it is necessary toobtain water samples and carry out a chemicalanalysis. Care needs to be taken to ensure thatthe sample is representative of the water bodyand is not contaminated by bore constructionmaterials. Use a clean, thoroughly washedcontainer of not less than one litre volume toobtain and store water samples. Used plasticdrink bottles with residual smell, colour and/or

taste are not acceptable.

Where it is necessary to determine the suitability ofa particular aquifer or provide early advice to theclient on the likely quality of water from a bore, anapproximate indication of water quality may beobtained by the use of field test equipment.

Professional water bore drillers would be expectedto have some basic water analysis equipment sothat an 'in the field' guide to groundwatersuitability can be given to the bore owner

Basic equipment would include a conductivitymeter and a meter or other method ofdetermining pH.

The equipment used should be checked andrecalibrated at intervals to ensure its accuracy.Most licensing agencies would be able to providethis service for a nominal charge.

A guide to the quality of water for various uses isgiven in Tables 6.1 and 6.2.

A quick determination of the total salts in borewater may be made using a conductivity meter.Conductivity can be used as a guide to totalsalinity, but it does not indicate the concentrationof individual ions, which is ultimately requiredto assess the suitability of water for a particularuse, nor does it indicate the presence of possiblecontaminants. If no conductivity meter isavailable and water is required for domestic orirrigation use be aware of water that clearsquickly when left standing in a container, as thisusually means high salinity levels are present.

The sample should be placed in a clean bottlepreferably rinsed at least five times with the

water to be analysed. The bottle should be sealedso as to prevent the entry of air. Special samplingand preservation techniques are required for theanalysis of specific ions.

The taking, handling, storage and analysis ofgroundwater samples for particularcontaminants may require special considerations.

6.2.1 Water used for irrigation

A guide to the suitability of water for irrigationcan be obtained from a conductivity analysis.Water authorities can supply charts listing therange of values for different crop types.

High concentrations of individual ions mayrender the water unsuitable, even if theconductivity value is within limits suggested.The suitability of water for continued irrigationwill depend on plant species, soil type, climateand soil leaching conditions. The client or boreowner should already be aware of any waterquality restraints imposed by the intended croptypes or proposed water use.


28/97

21

Table 6.1 National Water Quality Management Strategy Australian Drinking Water Guidelines 1996

Characteristic Guideline values: Comments

Health Aesthetic

Dissolved oxygen ** >85% Low concentrations allow growth of nuisance micro-organisms (iron/manganese/sulfate/nitrate-reducingbacteria) causing taste and odour problems, staining andcorrosion. Low oxygen concentrations are normal ingroundwater supplies and the guideline value may notbe achievable.

Hardness as CaCO3 ** 200 mg/L Caused by calcium and magnesium salts.Hard water is difficult to lather.500 mg/L CaCO3 severe scaling

pH * 6.58.5 While extreme pH values (11) may adversely affect health, there is insufficient data to set a health guideline.8 progressively decreases efficiency of chlorination.>8.5 may cause scale and taste problems.New concrete tanks and cement-mortar lined pipescan significantly increase pH and a value up to 9.2may be tolerated provided monitoring indicates nodeterioration in microbiological quality.

Taste and odour ** Acceptable to May indicate undesirable contaminants, but usually most people indicates problems such as algal or bio-film growths.

Temperature ** No value set Generally impractical to control; rapid changes canbring complaints.

Total dissolved solids ** 500 mg/L 1000 mg/L may be associated with excessivescaling, corrosion and unsatisfactory taste.

True colour ** 15 HU 15 HU just noticeable in a glass.(Hazen Units) Up to 25 HU is acceptable if turbidity is low.

If colour is high at time of disinfection, then the water shouldbe checked for disinfection by-products such as THMs.

Turbidity * 5 NTU 5 NTU just noticeable in a glass.>1 NTU may shield some micro-organisms fromdisinfection.


29/97

22

Table 6.2 pH limits for various water uses (guidelines only)

Domestic use

Desirable Maximum

78.5 6.59.2

Stock water use

Desirable Maximum

69.5 4.310.0

MINIMUM REQUIREMENTS FOR WATER SAMPLING

R6.5 Water sampling: After construction, water samples of at least 1 litre in volume shall betaken by the driller for analysis. Prior to taking a sample from a particular formation, the boreshall be pumped out or airlifted not less than three times the volume of the bore to removematerial which may contaminate the sample. The method used to collect the sample shall notcause contamination of the bore or the sample.

R6.6 Licensing requirement: Samples of water separate from the client's samplingrequirements of at least 1 litre in volume from every completed bore shall be supplied asrequired to the relevant licensing authority for chemical analysis. A clean container rinsed withthe water to be sampled shall be used. Sample containers shall be clearly labelled with the

name and address of licensee, bore licence number, depth to water bed and the date the samplewas taken. The relevant water authority may be a source of clean water sample bottles.

R6.7 Testing on site: Measurements of electrical conductivity (EC) and pH shall be taken usingportable meters or other methods.


30/97

23

Drilling fluids are used to facilitate theremoval of formation cuttings, act as alubricant and stabilise drilling operations.

The density (or weight) of a drilling fluid shouldbe kept as low as possible. Dense mixes shouldonly be used to control formation overpressure orcollapse or to control artesian flow.

Mud viscosity should be kept as thin aspracticable while the mud retains the ability tostabilise the formation and adequately clean thehole. Mud viscosity should be measured using aMarsh funnel. Suggested Marsh funnelviscosities for drilling unconsolidated materials

are shown in Table 7.1.

chapter

7.0 DRILLING FLUIDS

Because viscosity can often be confused withdensity, the specific gravity or density should bedetermined by means of a mud balance and notjust estimated.

The use of chlorides as a hydration (clay)inhibitor and weighting agent is notrecommended where steel casing is used.

Rotary-drill rig pumps or compressors shouldhave sufficient capacity to obtain the circulationrates shown in Table 7.2.

Table 7.2 Recommended up-hole circulation velocitiesand Marsh funnel viscosities

Circulating Marsh funnel Recommendedfluid viscosity up-hole velocity

(seconds) m/s

Air or mist Nil 1525

Water 26 0.6

Normal mud 3240 0.4

Thick mud 5080 0.2

Table 7.1 Suggested Marsh funnel viscosities fordrilling unconsolidated materials

Material Approriate Marshdrilled funnel viscosity

(seconds)

Fine sand 3045

Medium sand 4055Coarse sand 5065

Gravel 6075

Coarse gravel 7585

Lost circulation 85120


31/97

24

MINIMUM REQUIREMENTS FOR DRILLING FLUIDS

R7.1 Water: Fresh nonpolluted or if this is not possible the best quality water that is reasonablyavailable shall be used as the base fluid (make-up water) for all water bore drilling fluidpreparations. Water taken from swamps or creeks may be contaminated. If no other watersupply is available and swamp or creek water is used the bore may need disinfection before use.Where possible water shall be obtained from a treated town water supply.

Water shall not be used where it is obvious that it is polluted or suspected that it may bepolluted in that it occurs close to a pollution source.

The conductivity and pH values of all make-up waters shall be measured.

R7.2 Types of drilling fluids: The following types of drilling fluids shall be consideredacceptable for water bore drilling: water-based drilling fluids natural drilling fluids air-based drilling fluids

Fluid additives: Additives to drilling fluids that are acceptable for water bore drilling areclassified as follows:

(i) Dissolved additives

(a) mud-thinning agents. The use of mud thinner based on phosphates is not recommended

(b) surfactants, drilling detergents, and foaming agents

(ii) Non-dissolved additives

(a) native solids (clays and sand)

(b) bentonite

(c) polymers (liquid, powder)

(d) density-increasing materials

(e) loss-circulating materials (not recommended for the production zone).

R7.3 Manufacturers recommendations: The use of drilling fluid additives shall be inaccordance with manufacturer's recommendations. Safety notes and manufacturer's

recommendations for any additives used or proposed to be used by the driller shall be availablefor perusal by the licensing authority and client at the bore site during construction.

R7.4 Properties and tests: During drilling operations, when additives to water are used,drilling-fluid properties shall be maintained within the limits that will allow their completeremoval from the bore, if necessary, and shall not affect the potential capacity, efficiency, orquality of the bore. Drilling-fluid properties may be requested to be maintained during normaldrilling operations within the specified limits using test procedures conforming to API RP 13B:

(i) Weight (fluid density) test equipment: mud balance (API)

(ii) Viscosity test equipment: Marsh funnel (API)

(iii) Filtration (wall cake and filtration loss) test equipment: filter press (API)

(iv) Sand content (solids larger than 200 mesh) test equipment: sand-content set (API).


32/97

25

MINIMUM REQUIREMENTS FOR DRILLING FLUIDS (continued)

R7.5 Maintenance of fluid properties: The driller shall ensure that the composition andproperties of the drilling fluid are maintained to protect the water-bearing formationspenetrated and to allow the collection of good representative samples of the formation materialsduring drilling.

R7.6 Toxicity: Chemicals or other substances which could leave a residual toxicity shall not beadded to the fluid.

R7.7 Frequency of fluid testing: Drilling fluid properties should be tested regularly as anormal part of the drilling program or as determined by the drilling conditions.

R7.8 Removal: The drilling fluid must be removed from the hole to allow the subsequentdevelopment of the bore.

Measuring viscosity using a Marsh funnel


33/97

26

Page

deliber

ately

left

blank


34/97

27

chapter

8.0 PLUMBNESS AND ALIGNMENT OF BORES

Bore holes should be drilled and casings setto retain roundness and also be constructedwith as straight an alignment and true verticalplumbness as possible.

In shallow low-yield bores, where the smallestinside diameter of the bore is considerably largerthan the maximum outside diameter of thepumping equipment installed in the bore, somedeviation in plumbness and alignment seldomcauses problems. Plumbness and alignment arenever perfect. However, the driller should beexpected to keep alignment and plumbnesswithin practical limits under most conditions, byexercising reasonable care and using equipment

that is adequate and appropriate for the job.

Plumbness and alignment become more criticalwith deeper holes and where a shaft-driventurbine pump, helical screw type or rod-drivenpump such as a windmill or pumpjack is to beinstalled in the bore. A badly aligned bore or onecontaining kinks at casing joints, bends orcorkscrews can cause wear on the pump rods orpump shaft, shaft bearings and dischargecolumn. Under extreme conditions it may bedifficult to insert a pump into or withdraw it

from a bore.Alignment may not be as critical if a submersibleor jet type non-shaft-driven pump is to be used.

All bores completed for the purpose of extractingwater, other than monitoring purposes, should beconstructed to or pass the plumbness/alignmentmethods of testing.

8.1 Method of Testing

(a) Rigid dummy A rigid dummy is made

12 metres long of casing or similar material. Theoutside diameter of the dummy shall be 80 percent of the internal diameter of the bore casingbeing used.

Test dolly A test dolly is made up by weldingthree rings each of 85 per cent of the insidediameter of the bore casing onto a light but rigidcentre tube 12 metres long one ring each endand one in the centre.

In both of the above the lowering wire attachmentbail should be on the top and in the centre of the

assembly when suspended in the bore.

The cased hole must be sufficiently straight toallow a rigid dummy or test dolly to be loweredfreely under its own weight to the lowestproposed setting depth of the borehole pump.

(b) The test for plumbness shall be made using aplummet suspended on a thin-braided wire. This

consists of a pulley installed three metres abovethe bore head on a tripod or frame and positionedso that the plumb line comes off its outer edgeexactly over the centre of the bore casing.

The outer plumb ring or plunger should be56 mm smaller in diameter than the insidediameter of the bore casing. The plummet mustbe heavy enough to keep the plumb line taut butthe hub of the ring must not be solid as the watermust pass through it as it is lowered into thebore. The wire must be attached in the exact

centre of the plummet hub.Bore alignment shall be determined by loweringthe plummet three metres at a time and taking ameasurement of plumb line deflection from theexact centre of the casing at the bore head (seeFigure 8.2). Measurements are normally taken asNorth, South, East and West and maybe acombination of two. If the plumb line hangsthrough the casing centre line the bore is plumbat the depth the plummet is suspended. If theline does not hang in the centre, the bore at thatdepth is out of plumb by the distance from centre

plus an equal distance for each three metres theplummet is below bore head level.

Figure 8.1 Types of bore misalignment


35/97

28

MINIMUM REQUIREMENTS FOR BORE ALIGNMENT

Figure 8.2 Typical bore plumbness test assembly

R8.1 The completed bore shall be sufficiently plumb and straight so that there will be nointerference caused to the installation, alignment, long-term operation or future removal of thepermanent borehole pump intended for use.


36/97

29

Bores must be lined with an adequate lengthof appropriate casing to prevent the collapseof the strata penetrated. The casing also acts as asafe housing for any pump installed in the hole.

9.1 GENERAL CONSIDERATIONS

The casing must be of sufficient strength andcomposition to withstand the pressure exerted bythe surrounding strata and other forces imposedduring installation, bore development and anycementing operations, and to resist rapidcorrosion by the soil and water environments. Itshould provide a secure and leakproof conduit

from the water source to the surface throughunstable formations and through zones of actualor potential contamination. It must be joined andinstalled so that it is reasonably straight and freeof kinks or twists.

The selected diameter of the bore casing shouldfirstly comply with the minimum requirementsof the respective licensing authority and beadequate to accommodate the size of pumpselected to meet design or supply requirements.It should take into account:

the efficiency of the pumping unit the expected pump life the extra clearance required in the event that

the casing is not perfectly straight the possibility of weld metal projecting inside

at the joints of steel casing.

The wall thickness or class of the bore casingshould be selected in accordance with gooddesign practice and experience as applied toconditions found at the bore site. Where it isnecessary to drive casing only steel should beused. Casing that is placed in an oversized drill

hole may be of other types of materials as notedin these guidelines. Irrespective of what materialis used all joints should be watertight and havethe same structural integrity as the casing itself.

9.2 TYPES OF CASING

Casing selection depends on several majorfactors: strength requirements, corrosionresistance, ease of handling, cost considerations,type of formation, method of drilling, theparticular bore design, construction techniquesand licence or permit requirements. Casing musthave the column, collapse and tensile strengthsrequired for a specific borehole.

The improved drilling methods and techniquesnow available allow the use of a range ofmaterials for bore casing: steel PVC thermoplastic fibreglass

Each of these has advantages over the others andmay be more suited for a particular application.

9.2.1 SteelSteel is a commonly used casing material becauseof its greater strength.

Today much of the steel used as casing is in theform of piping or tubing and each length isjoined by butt welding. Some screwed andsocketed casing is used but the former is lessexpensive.

If using steel, choose casing or piping that isclean, new and of approved quality. Do not usesteel tubing that is defective or reject pipe.

Steel has these advantages over other types ofmaterials:

The diameter of drill hole can be smaller insoft formations.

It is stronger than other materials. It can be pressure-cemented to greater depths

due to its higher collapse strength. It can withstand rougher treatment.

A disadvantage with steel is that its life can bereduced in a corrosive environment. This can bethrough corrosive soils, water or by galvanicaction arising from the use of dissimilar materialsin the bore. Stainless steel has generally fewer

problems but cost may be a prohibiting factor.

It is also best not to use steel in situations whereiron bacteria are present. These bacteria cancause corrosion and use steel as an additionalsource of energy.

Some potable waters can be very corrosive tosteel because of the dissolved gases they contain,carbon dioxide being the most common.Indications of high CO

2water qualities that can

accelerate the corrosion of steel are listed inTable9.1.

chapter

9.0 CASING


37/97

30

The short-term strength of plastic casing is muchhigher than its strength over time. In general,short-term test results for strength are not a goodindication of long-term strengths.

Other factors to consider when using plasticmaterials include impact resistance, toughnessand pipe stiffness. When casing protrudes aboveground level, for example, it must be protectedbecause it can be severely damaged by movingvehicles or contact with drilling tools. The casingshould also be shielded from the suns ultravioletrays if exposed above ground for long periods,because the impact strength of the material maybe reduced significantly over time. Care must be

used during cold weather to prevent shatteringof the plastic during handling. Because theweight of plastic casing is only one-fifth to one-seventh that of steel, tensile strength is usuallyless important. Occasionally, it will float in abore during installation, thus creating specialhandling problems.

Plastic pipe may present a hazard to drinkingwater quality in areas where groundwatercontamination has occurred. If volatile organicchemicals exist in groundwater near a bore, but

above the intake section, it is possible for some ofthese chemicals to move into the discharge bypassing through the wall of the casing. Althoughthis process is not fully understood, it appearsthat plastic casing can be permeable in thepresence of certain chemicals.

9.2.3 PVC (unplasticised polyvinyl chloride)PVC pipe is made as piping for a wide range ofdrainage and general water distribution uses. Itis made in a variety of wall thicknesses andinternal diameters.

The only PVC piping suitable for use as borecasing is pressure rated pipe manufactured toAS1477 standards. The piping is swell-jointedand solvent-welded. The only solvent and primertobe used is Type 'P' conforming to AS 3879.

If screws are `used to support the joint while thesolvent cures, only stainless steel screws are to beused. Care must be taken to ensure the screwsdo not protrude internally.

All other PVC piping is unsuitable for use in bore

construction. PVC sewer or drainage pipe shall

Reactive Water Reactionagent quality

pH less than 5.5 corrosive

O2 more than 4 mg/L corrosive

CO2 more than 100 mg/L corrosive

CO2 50 to 100 mg/L marginal/corrosive

CO2 less than 50 mg/L acceptable

Table 9.1 Reactivity of steel casing tocorrosive waters

The reactivity shown in the table can varydepending on the chemistry of the particular

water.

Nonferrous or plastic materials are commonlyused as casing materials where corrosive waterspreclude the use of steel.

9.2.2 PlasticPlastic materials have much lower strength andweight than steel and require care in handling,storage and installation to prevent breakage ordistortion of their shape and must be derated inaccordance with the manufacturers

specifications when used with waters which areabove certain temperatures.

Plastic casing is low in compressive strengthrelative to steel casing. High temperatures deratethe pressure rating of the casing, so care must beused when grouting to minimise the effects of theheat of the curing grout around the casing.

Plastic material is much more flexible than steel.Therefore, plastic casing must be centred in theborehole before backfilling or filter packing is

completed. Any voids in the backfill or filterpack material may lead to sudden collapse offormation materials against the casing, causing itto break.

The collapse strength of unreinforced plasticcasing is much less than for steel casing. Theactual strength for any situation will depend onthe wall thickness uniformity, roundness of thecasing, rate of loading, and the temperature ofthe casing when the loading is applied. Whereunreinforced plastic casing is fully supported byevenly compacted non-clayey fill or by grout, the

collapse strength and hence possible settingdepth is significantly increased.

8/12/2019 Minimum Construction Requirement

minimum construction requirement water bore-aus

Documents