Circulating Fluid In Laser Drilling

Published Date: 02 Nov 2017

The mud to be used in laser drilling is generally to be a .since the diffraction is disturbed by using a liquid based mud hence a gas based mud is used .The method to be used for this is the purging method.

We can say that that laser drilling is done using Air Drilling Method and hence this is the most important aspect of laser drilling since it eradicated the pollution created by mud during rotary drilling also vanishes its environmental impacts.

Laser technique melts the rock as well as cuts it hence the methgod becomes easy to take out the rock chips and reducing the damage to the formation and also reducing the time constraint. The purging system provides a transparent medium for the laser to pass through , cleans the hole of cuttings and move molten material rock into the fractures to seal them as well as sealing the wall of the well bore.

Some experimental data is given below with respect to the hydrocarbon present areas, mud and other features of the well bore.

Effect of Saturation and Purge Gas Type on SE

To study the effects of beam interface on SE with limestone and sandstone saturated in brine, oil and water in the company of different nonreactive purge gases.

Procedure: The laser-rock-fluid interface test was conducted on Berea sandstone and limestone. Sandstone and limestone cores measuring 5.08 cm (2.0 in) diameter x 5.08 cm (2.0 in) height were located in vacuum environment for about 6 hrs and then soaked separately with water, brine or oil for at least 24 hours.

The composition of the brine was a blend of 25,000 ppm potassium chloride (KCl) and 25,000 ppm sodium chloride (NaCl) in 1,000 ml of water. The density of the brine was 1.039 gm/cm 3. The oil used in testing has a density of 0.841 gm/cm3. Each sample was positioned in Plexiglas chamber specifically designed to have debris and harmful vapor .Each saturated sample was lased for 8 s with 5.34 kW (CW) laser power. Lens with 1000 mm (39.37 in) focal length used to focus 2.54 cm (1.0 in) collimated ray. Spot amount was kept constant at 8.9 mm (0.35 in) before focal point. Air, argon, nitrogen and helium used independently on sandstone and limestone samples soaked with water, brine and oil to see the result of purge gas on exact energy. The purging gas provided a simulated reservoir condition (an oxygen-free environment) while removing rock debris and vapor from the beam path.

An optimized nozzle purge system used with compressed air at 620.5 kPa (90 psig) line pressure. Distance in purge nozzle and sample was about 2.54 cm (1.0 in). Specific energy is calculated based on weight differential & geometric methods. Results are presented in graph below for both sandstone and limestone.

Results and Analysis:

Purge Gas Type: This test was performed to determine if a change in the gas atmosphere near the hole during lasing affected SE. Four types of gas were used; nitrogen, compressed air, argon and helium. The purge gas was used to simulate reservoir conditions (oxygen-free environment) while removing debris and gases from the beam path.

For both sandstone and limestone, nitrogen provides the lowest observed SE values. The fallout are favorable given that process of the tool in a pressurized hydrocarbon atmosphere down hole will need a non-reactive gas, and nitrogen is generally used in this environment.

Purge Gas Type with Saturated Samples: Saturated samples in general resulted in elevated experiential values of SE than unsaturated sample .

More energy was requisite to initiate a phase alter from liquid to vapor. Additionally, this vapor served to partially block and absorb energy from the beam; therefore, fewer energy can be delivered to the rock sample.

Also of note as liquid in the pore volume changes to gas, the fluid expansion assists in the spallation process. This procedure provides a lowering effect on observed SE.

Objective: To simulate perforation under downhole conditions by applying axial and confining pressures (tri-axial load) on sandstone and limestone core samples.

Procedure: Initial tests were performed on cores of Berea sandstone and Bedford limestone under various conditions of axial, pore and confining pressures. For all cases, the laser remained the same. Full output power was applied continuously to each sample through the sapphire window of the pressure cell with a focused beam diameter of 0.089 cm (0.35 in) over 8.0 s. The 0.89 cm (0.35 in) diameter beam was beforehand found to generate no boundary effects with 10.16 cm (4.0 in) diameter core. The quantity of laser exposure time was calculated from earlier laser rock interactions to permit penetration into the heart without risk of penetrating the core’s full length and avoiding feasible harm to the pressure cell.

Results and Analysis

Five trial were performed on unsaturated samples. A base case was established for each rock type by lasing samples in the cell at ambient pressure conditions. A next condition was tested on each rock type with confine and axial stress limited to about 6895 kPa .Since the cores were not charged with pore pressure, a lofty pressure gas purge of 620.5 kPa through a 0.635 cm nozzle assisted in particle removal. A third situation was then tested for each rock type mutual confining and axial stress limited to about 6895 kPa , while charging the core to a pore pressure.

No gas purge was providing as underbalanced conditions served to eject particles from the charged core through pressure cell exit ports. Two extra trials were performed at balanced and underbalanced situation with twice the pressure settings.

To better understand the in-situ feat of lasers in the company of reservoir fluids, sandstone and limestone cores were drenched in brine and liquid hydrocarbon previous to high pressure lasing. Pressure conditions for each rock type included confining and axial stress limited to about 6895 kPa

with no pore pressure.

The resulting data generated from the succession of sample trials on sandstone and limestone have demonstrated that a laser perforation system will radically benefit from the high pressure conditions encountered down hole. For both rock types, SE value decreased as confining and axial stresses enlarged. The effect was more evident in the limestone than in the sandstone samples. The exclusion mechanism for Berea sandstone is spallation, where quick differential thermal expansion causes grains and cementitious material to fracture. The base case for sandstone with no pressure had an SE value of 19.75 kJ/cc. The condition is alike in many respects to much of the previous work performed in the lab. The model is at ambient conditions during lasing and a gas purge nozzle assist in removing kaput material.

The lowest SE value observed in sandstone was 12.91 kJ/cc , a 35% reduction from the base case, ensuing from the uppermost pressure values tested. Material removal is with the discrepancy between the pore pressure and wellbore chamber pressure. As this differential increases, material is more rapidly expelled from the tunnel, thus minimize travel through the cutting beam and engrossing less beam energy after coming off from the rock structure. With beam energy is less captivated by exiting particles, more is accessible for cutting, as evidenced by the drop in SE value.

Cementation

The cementation in laser drilling is to be done using conventional method o cementation making the cement to go through the drill pipe and reach the annulus surface and then allowed it to cool down and making the cement to be placed.

Since, in the laser drilling we are using the technique o casing while drilling method we have to be particularly careful about the through movement of cement material.

We see that when laser works inside the well bore so it creates a ceramic sheath now when the laser is run with the lowering o casing the cement is run out through the pipe using different output of cement in all directions .As we know that the drill hole will be of single diameter therefore their would be considerably no difficulty in cementation.

Laser Assisted Drilling

An apparatus for underground drilling have at least one optical fiber for transmitting light energy from a laser energy source disposed on top of ground to an underground drilling place and a mechanical drill bit having at least 1 cutting surface and forming at least one light transmission channel aligned to send out light from the at least 1 optical fiber through the mechanical drill bit by way of a at least one light transmission channel.

Why choose air drilling:-

Advantages of Nitrogen Drilling

Faster R.O.P.

Improved Deviation Control

Minimal Formation harm in Production section

Effective Pressure Control through Lost Circulation Zones

Detection of Low Pressure Zones

Quicker return of drilled cuttings

Overall lesser Cost per Foot

Disadvantages of Nitrogen Drilling

Large amount of Air Volume High Annular Velocity is necessary to carry cuttings up the hole;3000 ft/min Minimum Annular Velocity necessary for Hole Cleaning as per Angel’s Curves in 1957

5000 ft/min Annular Velocity optional for Optimum Hole Cleaning

Formation Pressure Control is negligible;

Can Not drill when H2 S zones are nearby

Danger of Down-hole fires: Use Nitrogen

Use Fire Float / Stop

Use Mist

Limited Applications: geological region with mature, stable and moderately dry formations ;

Problems with Down-hole motors & EM-MWD but improvement are being made and performance has enhanced with Mist.

What is Mist Drilling?

Air Drilling with the addition of liquids usually water, soap and chemical inhibitors .Assortment of water and soap is added to the air stream at surface at a proscribed rate to advance annular hole cleaning. Misting can use many dissimilar mediums (water, surfactant, etc.) When Misting the Annular Pressure increases so the ROP will typically drop VS Dusting application. Additional Air Volume can help improve ROP

When should you Mist Drill ?

Wellbore gets wet due to fluid influx.

Annular cleaning problems escort to contradictory flow at the Blooie line / pressure increase.

Wellbore fluid influx is up to 100+ gpm but is dependent upon Air Volume.

Reservoir produces huge amount of Gas / Condensate which create hole cleanout problem.

Hole showing fill after connections suggesting "Sloughing problems"……. caution Mist could increase sloughing if shales are sensitive.

Advantages of Mist Drilling

Higher ROP than with conformist mud.

Enables drilling to continue while producing fluids.

Improves Hole Cleaning capacity

Reduce risk of down hole fires.

Eliminate need for Nitrogen.

Cost:-

This is an estimated costing as a comparison of rotary and laser drilling.

 

Rotary

Laser

 

 

 

Mobilization

$132,000.00

$132,000.00

Mobilization Labor

$16,500.00

$16,500.00

Demobilization

$66,000.00

$66,000.00

Demobilization Labor

$16,500.00

$16,500.00

Waste Disposal & Cleanup

$30,000.00

$30,000.00

Location Cost

 

 

Site Expense

$32,000.00

$32,000.00

Cellar

$25,000.00

$25,000.00

Drill Conductor Hole

$8,000.00

$8,000.00

Water Supply

$10,000.00

$10,000.00

Initial Mud Cost

$10,000.00

$10,000.00

Daily Operating Cost

$1,040.65

$10,000.00

Rig Day Rate

$687.50

$10,000.00

Fuel

$1,425.60

$1,425.60

Water

$400.00

$400.00

Electric Power

$50.00

$1,000.00

Camp Expense

$200.00

$500.00

Drilling Supervision

$1,200.00

$2,000.00

DRLG Engr & Management

$1,000.00

$3,000.00

Mud Logging

$1,800.00

$1,000.00

Hole Insurance

$250.00

$250.00

Administrative Overhead

$500.00

$500.00

Misc Transportation

$500.00

$500.00

Site Maintenance

$200.00

$200.00

Waste Disposal and Cleanup

$200.00

$200.00

Misc Services

$750.00

$750.00

Drilling Fluids

 

 

Mud Cost

$45,111.11

$0.00

Mud Treatment Equip

$11,277.78

$0.00

Mud Cooling Equip

$9,022.22

$0.00

Air Service Hrs & $

$3,000.00

$20,000.00

DRLG Tools. Jars, Shocks

$19,918.50

$19,918.50

D/H Rentals, DP, DC, Motor

$17,000.00

$30,000.00

Drill String Inspections

$3,000.00

 

Small Tools and Supplies

$5,000.00

 

Fishing Hrs & $

$1,000.00

$1,000.00

Logging Hrs & $

$36,000.00

$36,000.00

Casing Services

$40,350.00

$10,000.00

CSG/Liner Hrs

$1,026,508.80

$50,000.00

Casing Cementing Equipment

$8,000.00

$8,000.00

Liner Hanger and Packers

$0.00

$0.00

Cementing

$270,000.00

$270,000.00

Wellhead $

$15,000.00

$15,000.00

Welding and Heat Treat

$25,000.00

$25,000.00

BOPE Hrs & $

$22,781.11

$22,781.11

Test and Completion

 

 

Location Cost

$0.00

 

Testing Coring Sampling

$0.00

 

Well Testing Hrs & $

$0.00

 

Completion Hrs & $

$20,000.00

$20,000.00

Production Tree and Valves

$84,000.00

$84,000.00

 

 

 

Casing

$1,577,155.80

 

30"0.375 Wall Welded

$7,200.00

$300,000.00

22"0.625 Wall Welded

$139,750.00

 

16"109lb L80 Premium

$287,897.00

 

113/4"73.6lb K55 Premium

$1,034,508.80

 

85/8"40lb K55 Slotted

$107,800.00

 

Other Well Equipment

 

 

Wellhead Assembly

$35,000.00

$50,000.00

Liner Hangers and Packers

$52,000.00

$52,000.00

Drilling Engineering

$75,619.70

$75,619.70

Direct Supervision

$90,743.64

$90,743.64

Mobilization and Demobilization

$346,000.00

$346,000.00

Drilling Contractor

$1,247,725.03

$1,247,725.03

Bits, Tools, Stabilizers, Reamers etc

 

 

Bit Totals

$321,647.50

$600,000.00

0’ to 1250’ Interval 28"

$43,190.00

 

1250’ to 5000’ Interval 20"

$53,480.00

 

5000’ to 12000’ Interval 143/4"

$132,790.00

 

12000’ to 16000’ Interval 103/8"

$92,187.50

 

Stabilizers, Reamers and Hole Openers

$64,329.50

 

0’ to 1250’ Interval 28"

$8,638.00

 

1250’ to 5000’ Interval 20"

$10,696.00

 

5000’ to 12000’ Interval 143/4"

$26,558.00

 

12000’ to 16000’ Interval 103/8"

$18,437.50

 

Other Drilling Tools, Jars, Shock Subs, etc

$48,247.13

 

0’ to 1250’ Interval 28"

$6,478.50

 

1250’ to 5000’ Interval 20"

$8,022.00

 

5000’ to 12000’ Interval 143/4"

$19,918.50

 

12000’ to 16000’ Interval 103/8"

$13,828.13

 

D/H Rentals DP, DC, Motors etc

$72,000.00

 

Drill String Inspections

$12,500.00

 

Small Tools, Services, Supplies

$20,000.00

 

Reaming

$7,500.00

 

 

 

 

Directional Engineering Service

$36,451.11

$0.00

Directional Tools

$23,191.11

$0.00

Mud Motors

$140,222.22

$0.00

Steering/MWD Equipment

$73,111.11

$0.00

 

 

 

Drilling Fluids Related

 

$0.00

Drilling Muds, Additives & Service

$104,227.78

$0.00

Mud Cleaning Equipment

$25,744.44

$0.00

Mud Coolers

$19,395.56

$0.00

Air Drilling Services and Equipment

$45,500.00

$70,000.00

 

 

 

Well Control Equipment

 

 

Blow out Preventer Rentals

$48,546.67

$48,546.67

Diverter

$3,500.00

$3,500.00

211/4"2000 Stack

$10,750.00

$10,750.00

163/4"3000 Stack

$25,781.11

$25,781.11

135/8"3000 Stack

$8,515.56

$8,515.56

135/8"3000 Stack

$ –

$ –

 

 

 

Mud Logging and H2S Monitoring & Equip.

$136,115.46

$136,115.46

Electrical Logging

$94,000.00

$94,000.00

0’ to 1250’ Interval

$ –

$ –

1250’ to 5000’ Interval

$18,000.00

$18,000.00

5000’ to 12000’ Interval

$36,000.00

$36,000.00

12000’ to 16000’ Interval

$40,000.00

$40,000.00

16000’ to 20000’ Production Interval

$ –

$ –

Testing, Sampling & Coring

$2,000.00

$2,000.00

Well Test

$130,000.00

$130,000.00

Completion Costs

$95,000.00

$95,000.00

 

 

 

Misc Expenses

 

 

Transportation and Cranes

$37,809.85

$37,809.85

Fuel

$107,803.44

$107,803.44

Water and System

$30,247.88

$30,247.88

 

$9,291,934.80

$4,645,583.55

 

 

 

Capabilities of Laser Drilling

No physical contact (no tooling wear or breakage, minimal material distortion)

High speed

Computer controlled accuracy

Programmable hole sizes

Multi-axis perforations

Remote processing

Minimize heat input, results in lesser disturbance of the work-piece.

Increase in cutting speeds and higher throughput in most

   instances

No expensive tooling to add to the cost of producing a part.

No tool required to wear or replace.

No tool makes prototyping parts inexpensive and fast.

Edges are cleaner so none secondary deburring operations are

   necessary on some materials.

A laser cutting heads minimize set-up time.

These are extremely flexible and lend themselves to quick changeover.

Application to a wide range of materials and thickness

Narrow kerf widths

Very high repeatability

Very high reliability

Reduced tooling costs and reduced setup times

Versatility (the same tool can also be used for laser drilling and laser welding)

Capacity for high degree of beam manipulation (true 3-D cutting)

Limitations of Laser Drilling

Cannot drill holes of stepped diameter

Blind hole drilling difficult

Beam divergence limits hole depth

Cost of safety devices

Skilled operators and maintenance personnel required

Other Advantages to Laser Drilling

Roadways and Other Structures Many areas of the world use multi-level roadways to enhance vehicular transport ease. Along the same line, many countries use bridges to support rapid transfer on rail systems. The majority of these transportation-support structures relies on concrete and rebar for their structural integrity. As part of an earthquake rehabilitation program it will be possible to use laser-drilling technologies to not only interrogate the concrete for potential failure but also to create access holes wherein rebar can be introduced to reinforce the concrete structures. Clearly, if one can envision a multiple level roadway exchange that requires earthquake rehabilitation, it is inconceivable to think that a drill rig could allow access to the vertical columns wherein it is highly reasonable to think that one could lower cages down with a coil released laser-drill to create rebar access holes at various locations in vertical concrete support columns.

Unexploded Ordinance: With respect to applications for unexploded ordinance; once new UXO locations have been identified using surface or remote scanning technologies, a confirmation approach is required. That confirmation approach typically involves either excavation or a surface conventional drilling technology.

Using micro-laser-drills, a micro-hole can be very accurately created down to the ordinance of interest. Once the ordinance has been located, the laser drill parameterser can be changed to either interrogate the kind of ordinance casing or to atomize the material around the ordinance so that one can visually look at the kind of ordinance. If the nature of the ordinance is such that it is unstable or can be exploded in place, the laser-drill parameters can be re-configured to detonate the explosive. The notion of using conventional drilling technologies to drill down to most UXO is simply unreasonable.

DISCUSSION

Rock destruction and removal is a significant issue in the Earth boring and tunneling industries. Over the years, billions of cubic feet of rock have been removed, with tremendous capital investment. In the oil and gas industry alone, approximately 20,000 wells (oil, gas and dry) were drilled onshore in the US in 1999, with an average depth of 6,000 feet. This is equivalent to approximately 23,000 miles, or approximately three times the diameter of the earth (7,899 miles).

According to a GRI study conducted in 1995 on costs associated with well construction, nearly half of the time was spent on drilling, a one fourth of the time on moving tools in and out of the hole, and the remaining quarter on casing and cementing activities. In general, mostly potential cost reductions related to well drilling were likely to come from increasing the rate of penetration of the drill bit into the earth, and it reduces the time involved with moving tool, such as drill bits and pipe, out and in of the hole.

A significant amount of time can be spent on drilling through rock strata other than the reservoir rock. To drill in hard rocks, such as granite, is extremely tough and can expend a great amount of resources with little penetration resulting. Other problems associated with the drilling process include stuck pipe, fishing operations for lost tools down-hole, and side tracking procedures, all of which are time and money consuming operations.

Conventional completion techniques, specifically perforating, can also create extensive and costly damage. An instantaneous force from a shaped charge explosive detonated down-hole focuses a penetrating, small-diameter jet through casing and cement into the reservoir rock. This process usually results in significant damage to the formation and a reduction in reservoir rock porosity and permeability. In most cases, it is necessary to minimize flow restrictions into the wellbore through time-consuming and costly post-perforation operations.

Laser perforation and stimulation technology has a wide range of applications for the well completions industry, and could be applied in multiple environments including deep wells, well recompletions and directional stimulation. These applications could provide economic alternatives to add reserves to older fields, improve production and deliverability of oil and natural gas well, and improve the injection/withdrawal cycle efficiencies of underground natural gas storage facilities. In addition, since there is no set distance between shots with the laser tool now envisioned, perforation designs could be modified on the fly, to increase productivity of troublesome zones. Perforations also could take the shape of either vertical or horizontal slots in the wellbore wall.

Conclusion

It was at the turn of the 20th century when rotary drilling supplanted cable tool drilling as the petroleum industry's standard method for reaching oil and gas formations. While major improvements have occurred since then, fundamental mechanical drilling method has remained essentially the same.

Using lasers to bore a hole offers an entirely new advance. The novel drilling system will transfer light energy from lasers on the surface, down a borehole with a fiber optic bundle, to a succession of lenses that will direct the laser to the rock face.

Researchers are in believe that state-of-the-art lasers have the potential to penetrate rock many times faster than conventional boring technologies - a huge benefit in reducing the high costs of operating a drill rig.

Today, a typical land-based oil or gas well costs around $400,000 to drill, while costs for an offshore well average nearly $4.5 million. But in some deeper or more hard drilling terrain, expenses can be much elevated .Reducing the time a drill rig remains on site can lower costs and make previously uneconomic gas or oil deposits commercially attractive.

The Study showed that laser systems now can provide more than enough power to cut rock. Because laser head will not contact the rock, there will be no need to pause drilling to substitute a mechanical bit.

Moreover, researchers believe that lasers have the ability to melt the rock in a way that creates a ceramic sheath in the wellbore, eliminating the price of buying and setting steel well casing. A laser system possibly will also contain a variety of downhole sensors - including visual imaging systems - that could communicate with the surface through the fiber optic cabling.

While the lure of laser drilling has been its speed, one major drawback has been the large amounts of energy experts assumed would be required.