• Name:- Virat Patel• Roll no- 14BPE094• Seminar no:- 38• Batch:- U2

Drilling Technologies

WHY TO DRILL?

What is going on?

Drilling problems

Hole deviation Pipe sticking Loss of circulation Caving Hole cleaning And many more

WHAT NEXT?

• LASER DRILLING

• SNAKE WELL DRILLING

•RADIAL DRILLING

• PLASMA DRILLING

WHAT IS LASER TECHNOLOGY?

• The Laser(light amplification by stimulated emission of radiation) devices are those which convert one form of energy into photons which are electromagnetic radiations.

• Laser drilling works on the principle of transferring light energy from the surface through fibre optic cabling – which transmits light with little or no loss of energy through Total Internal Reflection – to a series of lenses which direct the laser light to the surface of the rock. This concentrated beam of light is capable of cutting rock many times faster than the conventional method of drilling.

LASER DRILLING In order to break rock mechanically, sufficient energy has to be expended to overcome the in-

situ rock stresses. Similarly, in laser drilling, sufficient heat must be applied to raise the local temperatures so that they exceed the melting point of the rock. Once that threshold value is exceeded, the amount of energy required to remove a piece of rock remains almost constant.

To quantify the amount of energy needed, a parameter called specific energy (SE) is used. SE is defined as the amount of energy required removing a unit volume of rock and is given by:

SE= (Energy Input)/(Volume of Rock removed)= P/(dV⁄dt)

Where,P = Power Input (Watts)dV/dt = Volume Time Derivative (cm3/sec)Its is expressed in kW/(cm³⁄s) or kJ/cm³

LASER MECHANICAL BIT• While going all out for a complete laser bit may not seem a very economical or sustainable

option today, a combination of laser and mechanical bit is certainly feasible. It consists of a rotating laser beam which fractures and weakens rock, combined with a set of PDC cutters that scrape the weakened rock from the affected area. The laser mechanical bit works by first spalling the rock by a laser beam. Weakening of rock is caused due to fracture development, mineral dehydration and vaporization brought about by the laser beam, which results in an increase in void space.

• This weakened rock can then be drilled through using the conventional mechanical technique.

• The laser characteristics can be adjusted from the surface depending on the lithological characteristics interpreted from well logs.

APPLICATIONS:• The normal mechanical method of drilling faces certain challenges. Penetrating hard and ultra-hard

rocks such as granite, for example, requires tons of weight on bit and wears it out quickly. The concept of laser drilling can substantially reduce the time and money required in such situations. It has certain benefits over the conventional methods. Some of the major advantages are:

• Increased ROP

• Provision of temporary casing

• Reduced trip-ins and trip-outs

• Accurate and precise drilling, with ability to cut rock in select areas

• Single diameter borehole possible

• In addition, laser drilling rigs occupy very less space. Conventional rigs may take upto several thousand square feet of space and cost of transporting them is very high. Studies estimate that the cost of drilling a well may be reduced by 10 times while using a laser drilling rig.

LIMITATIONS OF LASER DRILLINGThe main disadvantage of laser cutting is the high power consumption. Industrial laser

efficiency may range from 5% to 15%. The power consumption and efficiency of any particular laser will vary depending on output power and operating parameters. This will depend on type of laser and how well the laser is matched to the work at hand. The amount of laser cutting power required, known as heat input, for a particular job depends on the material type, thickness, process (reactive/inert) used, and desired cutting rate. Some more disadvantages of later drilling are:

• Cannot drill a blind hole to a precise depth.

• Laser technology to be supplied to field.

• Slower processing large holes.

• A drill bit that combines high-power laser energy with polycrystalline diamond compact bit technology.

• A test hole drilled 12' deep in dolomite rock with a compressive strength exceeding 30ksi. The discoloration of the rock is oil discarded by the drilling motor.

The Snake Well■ It is surprising to learn that, when an oil field reaches the end of its normal production life,

up to two-thirds of the oil can still be left in the ground. This oil is too difficult to extract because it is located in various small pockets that cannot be accessed under normal operating conditions.

■ According to the International Energy Agency, the world's economies would benefit from an extra 300 billion barrels if access was made possible. The innovative snake well is one of the solutions which Shell engineers have come up with in order to improve access. Snake well are so called because they can be drilled horizontally and 'snake' from one pocket of oil to another. Without the  snake well, several individual wells would have to be drilled in order to access each pocket. The  snake well significantly lowers the cost of drilling.

■ Shell has successfully practiced in Champion West oil field, Brunei.

Advantages■ Improved oil recovery.■ More profits and less time .

Disadvantages■ Difficult in drilling initially.

Radial drillingRadial Drilling is a technique which utilizes hydraulic jet energy of fluids to drill lateral holes

inside the reservoir. In this several small diameter holes are drilled from a mother well which radiate in different direction & levels throughout the depth of the well or wherever there is possibility of finding more Oil & Gas. It is mainly used to stimulate depleted or dead wells by bypassing the damaged/skin zone & extracting crude from unreached virgin lateral holes extending beyond the skin region.

RD is an unconventional drilling method which utilizes Coil Tubing conveyed drilling to create micro diameter holes by expending the energy of high velocity jet fluids. A small section of casing of the mother well.

With the use of Radial drilling, oil that otherwise would have remained beyond the reach of conventional technologies can now be recovered efficiently and economically. In some cases production recovers to a level that equals or exceeds that of the well’s initial production. This enables drilling farther into the strata.

Top view of 90˚ oriented fractures.

Specifications•Generally lateral hole of about 300ft-500ft length are drilled having a diameter of 30mm-50mm (1.2 inches-1.9inches) and injection pressure should be 10000-15000 psi.

•The maximum working depth is about 10,000ft. Bottom hole temperature should be of maximum 248 o F. Drilling fluids varies depending on reservoir lithology and formation fluid properties. Water is generally used in most operations. For water sensitive formations diesel fuel may be used which also is useful when dealing with waxy reservoir fluids. Hydraulic acid can be used as a drilling fluid in carbonate formation. Because of high jet fluids, casing and formation get eroded for which abrassives are used.

Indian scenario•RD has been done by Selan Exploration Technology Limited recently for the first time in India for lateral jet drilling. The zone where it was done were mostly of Kalol VIII reservoir, Ahmedabad, Gujarat.

•Three wells were selected and each well was performed with 6 numbers of lateral wells. The reservoir is a silty sandstone layer having low permeability and porosity. The operation was done in two steps: casing cutting using a tungsten carbide bit of size 22mm and then performing jet drilling using high pressure jet hose in variety of jet angles to drill the lateral holes. Coil tubing unit has been used for the surface equipment. Hence from this it can be seen that RD jobs have been started and can be applied in other states of India.

•The cost is low and dead fields can be reused to produce leftover crudes.

Conclusion•RD method is highly encouraging and evolving technique. Its primary usage is to improve production which is needed to be implemented in the dead fields.

•Apart from improving production, it is also a bypass technique which increases productivity without improving the damage zones in a reservoir.

•Also wherever IOR-EOR methods needs to be implemented, RD technique can be applied first. It helps reduce initial cost as well as buys some extra time of another one –two years of average production.

Benefits

• Increase production rate and recoverable reserves from marginal wells.

• Improves injection rates in water disposal/injection wells.

• Allows directional treatment of wells e.g. acid, steam, CO2, etc.

• Allows multi-layer application in thicker reservoir zones.

• No need for large, expensive rotary rigs.

• No additional stimulation required.

•Average operation duration is one to four days per well, thus limiting the time the well is out of production.

Plasma Drilling• A method of drilling based on the use of a plasma drill, or specially designed p

lasmatron

• Plasma drills with air-eddy stabilization, or “swirling” of the electric arc discharge which is plasma source.

• The temperature of the plasma jet in plasma drilling may be as high as 5000°K, which is sufficient for the destruction of the rocks at the bottom of the drill hole. The plasma-forming materials in plasma drills are air, inert gases, water vapour, and mixtures thereof. The axial position of the arc in the plasma drill permits high power outputs to be obtained with a small outer diameter.

Working• Compressed air is supplied through a hollow drill rod to the plasma drill,

where it is separated into two streams.

• One stream proceeds to the internal electrode through a spiral swirling channel, feeds the discharge, and by blowing on the arc, forces it to rotate. The rotation displaces the electrode spots of the arc over the surface in the interior of the electrode and thereby prevents the premature burning of the electrode. The second stream cools both electrodes by flowing around cooling fins.

• A part of the second stream proceeds through tangential opening in the insulating sleeve into the discharge chamber. The plasma that has been formed , flows out through one or more nozzles toward the bottom of the drill hole. After the cooling of the electrodes, a large part of the second stream is injected to the outside through openings in the plasma drill cover and carries the drilling debris out of the drill hole.

Benefits• Can easily drill 3-10 km depth with large bottom hole

• Extensively useful in drilling igneous rocks and deep wells.

• Efficient, lesser well problems and faster.

• At experimental level, not in practice.

• Production and use of plasma is matter of worry.

QUESTIONS ?

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