Drilling and Completion Technique Selection Methodology for CBM

IPTC 17153 Drilling and Completion Technique Selection Methodology for Coalbed Methane Well Wells s J. Caballero, ExxonMobil Development Company Copyright 2013, International Petroleum Technology Conference This paper was prepared for presentation at the International Petroleum Technology Conference held in Beijing, China, 26–28 March 2013. This paper was selected for presentation by an IPTC Programme Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the International Petroleum Technology Conference and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the International Petroleum Technology Conference, its officers, or members. Papers presented at IPTC are subject to publication review by Sponsor Society Committees of IPTC. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the International Petroleum Technology Conference is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented. Write Librarian, IPTC, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A., fax +1-972-952-9435

 Ab st rac t Geographically, coal-bed methane exploration or development has occurred on every continent with the exception of Antarctica. Worldwide, many different completion techniques have been utilized to develop coal-bed methane reservoirs. These techniques range from vertical well multi seam completions to multiple lateral wellbores drilled into a single coal seam. Stimulation techniques include open-hole under-ream, cavity creation, and hydraulic fracturing. A number of factors influence the selection of completion techniques including proximity to established oil and gas infrastructure, depth, number and thickness of coal seams, permeability, gas content, composition, and saturation, porosity, etc. The purpose of this paper is to survey the various techniques that have been utilized, to provide the rationale for utilization of each technique, to comment on the commercial success of the t he various techniques, and to propose a general selection criteria approach that may be useful in the selection of a drilling and completion technique. Introduction While CBM well drilling and completion permutations may be practically endless, the following summary descriptions will  be covered in this paper:    

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Vertical well, open-hole and under-ream completion, single seam Vertical well, cased and open-hole, perforate and under-ream completion, multi-seam Vertical well, open-hole cavity completion, single seam Vertical well, cased perforated, hydraulic fracture completion, multi seam 1. Plug and Perforate 2. Ball and Baffle 3. Multiple Zone Stimulation Technology (MZST) Vertical well, open-hole under-ream with intercepting single or multiple surface to in-seam open-hole horizontal well(s), single seam Vertical well, open-hole under-ream with intercepting a surface to in-seam open-hole multi-lateral horizontal well

Other techniques not listed here can generally be considered to be a variation or combination of one or more of these techniques. Many authors have proposed methods for determining the optimum drilling and completion method [1, 2, 3]. These methods have consisted of flow diagrams, empirical studies, and reliance on a few critical reservoir parameters and form the basis for conceptual understanding of the problem. This paper will present an overview of the various CBM drilling and completion techniques; reservoir parameters that need to be considered in the selection of drilling and completion techniques; and a proposed methodology for selecting optimum drilling and completion techniques will be proposed.

Fundamental Reservoir Parameters Factors to be considered in the selection of drilling and completion technique include [4, 5]:   

Reservoir Thickness Coal Cleat/Fracture Permeability Coal Cleat/Fracture Porosity

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        

Reservoir Pressure Gas Saturation and gas composition  Number of Seams Geologic Complexity Minimum Complete-able Thickness Dip Coal Competency / Hole Integrity / Risk of Collapse Surface Access Economics, Capital and Operating Costs

Each of these reservoir parameters is perhaps critical in the selection of an appropriate drilling and completion technique. In general, the following principles are suggested: coal seams with lower permeability require a greater degree of stimulation such as hydraulic fracturing or cavitation in order to achieve economic production rates and cumulative recovery; thick, highly permeable coal seams require relatively little stimulation, while low permeability coal seams may require stimulation techniques such as horizontal drilling; large numbers of coal seams or highly structured, geologically complex coal seams may limit the optimal candidates to vertical well completion options only; or surface access or limitations in local services may drive the drilling and completion decision.

Vertical Well, Open-hole and Under-ream Completio n, Single Seam This drilling and completion technique was pioneered in the Powder River Basin. The major steps for this drilling and completion technique are: 1) drilling the production hole to the top of the coal seam; 2) running and cementing casing; 3) drilling a hole through the coal seam; and 4) increasing the diameter of the hole by a technique known as under-reaming. This process is illustrated in Figure 1. The resulting hole diameter after under-reaming may be as large as 4 feet. From a reservoir engineering perspective, the stimulation effect is achieved because the resulting under-reamed hole diameter is larger than the original hole diameter. In addition to under-reaming, small high rate water injection into the coal seam may be utilized to open up and relax the surrounding coal cleat system providing additional stimulation. This type of technique is best suited for thick, vertically continuous, highly permeable coal seams. The primary advantage of this technique is that it is very inexpensive relative to other options discussed later. Disadvantages for this type of drilling and completion technique are that caving of the formation may cause fill which in turn may cause production problems, completion of deeper coal seams is nearly impossible, and completion of upper coal seams may be difficult and complicated. Also, because drilling stops at the base of the coal seam, there is no “sump” in which to place the pump, so part of the coal seam may remain under water. This type of drilling and completion technique has been used extensively in the Powder River Basin, the San Juan Basin, and has been attempted in other areas. Figure 2 illustrates an example of a simple under-reaming tool. The under-reaming tool works by rotating the drill pipe. High rotation speed causes the “wings” of the tool to swing out by centrifugal force so they can cut into the coal formation. Fluid is circulated during the process in order to lift the coal cuttings as they form. There are many different varieties of under reaming tools and they all share the characteristic of a low cost low technology technique.

Vertical Well, Cased and Open-ho le, Perfor ate and Under-ream Completion , Multi-seam This drilling and completion technique is a variation of the technique described above and was motivated by the desire to capture reserves that would otherwise be left behind cemented casing at shallower depths than the primary completion coal seam. In this technique a hole is drilled to the top of the main target coal seam and casing is run and cemented as before. After under-reaming, a bridge plug is set above the primary completion interval, and additional coal seams are completed according to typical plug and perforation techniques that will be described later in the section titled “Vertical Well, Cased Perforated, Hydraulic Fracture Completion, Multi-seam”. If additional coal seams are to be developed, care must be taken to ensure that the incremental cost of the completion is  justified by the incremental revenue from the additional coal seams.

Vertical Well, Open-hole Cavity Comp letion , Sing le Seam This drilling and completion technique is similar to the vertical well open-hole single seam under-ream completion in that a hole is drilled to the top of the coal seam where 7 in. casing is run and cemented [6]. After the coal seam is drilled, instead of  performing the under-ream technique, air compressors are used to inject air (and sometimes water and air) into the coal seam at high rate and pressure. After injection, the well is opened to the atmosphere and the high pressure air is allowed to escape from the coal seam. This process causes individual pieces of coal to cave into the wellbore, after which they are circulated out

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of the well bore. This process is repeated many times (typically perhaps 15 times or more). The latter injection cycles cause less coal to cave than the earlier cycles, and cuttings returns are monitored to determine when injection cycles no longer yield adequate caving to warrant further cycles. At the completion of the cavity process, the well may be left open hole or a  perforated liner may be installed [6, 12]. Figure 3 is an illustration of a cavity completion. The stimulation achieved by the cavitation process can be attributed to two main mechanisms [7]: first, the increased diameter of the well bore caused by the cavitation process; and second, coal cleat relaxation in the area beyond the cavity which increases the aperture of the cleat system creating an additional stimulated zone. Figure 4 is an illustration of a density and sonar log of a caviated well. The left track is a density log where the coal / shale sequence can clearly be seen as indicated (coal is much less dense than shale). The right hand track indicates the radius of the cavity as determined by the sonar log. This illustration shows a typical radius of 4 to 5 feet. Figure 5 is an illustration of a simplified cavity. The void space or cavity may have a radius of 4 to 5 feet and may occasionally be larger. Surrounding the cavity void is a zone of enhanced cleat permeability known as the shear zone. This shear zone may have a radius of 10 to 15 ft. Beyond the shear zone another zone of enhanced cleat permeability known as the tensile zone which may extend to a distance of 90 to 150 feet [7]. In this diagram the well bore and cavity is represented  by the white circle. Zones of enhanced cleat permeability are represented by the light blue and dark blue areas. The shape and direction of the shear and tensile zones created by the cavity process are influenced by the face cleat and butt cleat direction as well as the current stress field, and are most likely not circular or oriented in the same direction. Cavity completions have been performed in Australia, Canada, India [12], and the United States; however, it has been successful primarily in the San Juan Fairway [7] and Unita Basin of the United States, and to some extent in Australia. Cavity completions have been successfully applied in the Bowen basin in Australia, but this technique has not been utilized widely at this time. It is proposed that cavity completions work best in the weak brittle coal with a rank ranging from high volatile A to medium volatile. Other ideal situations for cavity completions are thought to be a high permeability, normally to over pressured, fully gas-saturated, naturally fractured coal in a low stress environment [7]. Areas or properties thought to be unfavorable for the cavitation process are north and south of the San Juan fairway, strong or ductile coals in areas of high insitu stress, coals with low permeability, or under pressured and under gas-saturated coals.

Vertical Well, Cased Perforated, Hydraulic Fracture Completion, Multi-seam 1. Plug and Perforate 2. Ball and Baffle 3. Multi Zone Stimulation Technology (MZST) This technique is by far the most common technique for drilling and completing CBM fields, especially where multiple completable seams are encountered and many or most of them need to be hydraulically fractured in order to achieve economic flow rates and cumulative recoveries. This technique is typically used where the coal cleat system has permeability ranging from 0.1 to 100.0 md. Because hydraulic fracturing is utilized, a method of zone isolation must be used between hydraulic fracture stages. Three primary methods of zonal isolation will be discussed. This technique is common in domestic US basins such as Central and Southern Appalachia, Black Warrior, Raton, and internationally in Australia, China, and India [12]. The technique involves drilling the production hole to a depth 50 to 100 ft below the lowest coal seam to be completed, and running and cementing production casing. Typical total depths may range down to 4000 ft. Zones are completed sequentially from bottom to top. The first zone to be completed is perforated (several individual coal seams may be included in each stage) and hydraulically fracture stimulated. The zone is then isolated and the next zone is perforated and hydraulically fractured. Zonal isolation can be accomplished by several techniques such as “perf and plug”, “ball and baffle”, Multi Zone Stimulation Technology (MZST), and others. Figure 6 is an illustration of this type of completion. Advantages of this technique are that all desired coal seams can be sequentially completed in stages leaving nothing behind  pipe, coal particles and fines are generally well controlled behind pipe, minimizing formation caving and associated  production problems such as pump and equipment plugging and hole fill-up. Disadvantages may include somewhat higher cost and completion time depending on the number of hydraulic fracture stages, and wells may experience initial well clean up issues such as sand and coal fine production. Operators may control the initial rate of water level reduction in order to manage these problems.

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Perforate and Plug Isolation Technique:  In this technique, the zone to be stimulated is perforated and hydraulically fractured. After a short flow back period, the well is shut in, a wire-line lubricator is installed with a bridge plug, and the bridge plug is run and set at a location between the hydraulic fracture stage just completed and the subsequent stage. With the well controlled at this point, another set of coal seams are perforated, and the sequence is repeated. After all hydraulic fracture stimulation treatments are completed, the plugs are drilled out, and after final flow back and clean up, artificial lift equipment is installed with the pump typically set at a location below the lowest perforation in the well.

Setting the pump below the lowest perforation in the well allows the well-bore to act as the first stage of water/gas separation; the water falls with gravity to the pump where it is pumped up the tubing string, and the buoyant gas is allowed to flow up the casing-tubing annulus. At the surface, additional separation and dehydration may be required, either at the well site or at a central facility.  Ball and Baffle Isolation Technique : In this technique, baffles are installed at predetermined locations in the casing string. Baffles are metal rings that are beveled in order to accept a seating ball. These baffles are threaded so they can be installed by screwing them into the casing collars. Obviously, the baffles are installed in the casing at depths such that they will isolate each hydraulic fracture stage from subsequent stages. Logs must be carefully studied in order to decide optimal placement of the baffles. The baffles have varying inside diameters, and are installed with the smallest baffle at the bottom, followed by  baffles of successively increasing diameter. In this way, small balls will drop through the larger inside diameter baffles and seat in the appropriate baffle. The next stage is isolated by dropping the next larger ball, and so on.

The first stage is perforated and hydraulically fracture stimulated as before, and after a short flow back, a ball is pumped and seated in the first baffle. Then a lubricator with perforating gun is installed, and the next zone is perforated, and the sequence is repeated. It is possible to perform up to seven stages with this technique, which is sufficient in the majority of cases. This technique was first pioneered in 4 ½ in. casing in the Appalachian and Permian Basin (latter basin not a CBM application),  but has also been utilized in 5 ½ in. casing [12]. In some applications, th e baffles can be installed after casing installation using slip/packer devices; however, because of t he necessarily smaller diameter baffles, higher hydraulic fracture treating  pressure may be expected.  Multi-Zone Stimulation Technology (MZST) : This technique is currently being studied for use in vertical and deviated CBM well completions in Australia, utilizing MZST (or multi-zone stimulation technology) which is licensed to multiple stimulation service companies [13]. Specifically, the MZST technique utilizes coiled tubing to convey the completion tool string consisting primarily of a re-settable packer and jetting nozzles which are used to hydraulically “cut” perforations in the casing. In this technique the first set of perforations are cut by pumping an abrasive fluid down coiled tubing and through a few small diameter nozzles at high pressure. This results in a high velocity stream of abrasive fluid striking the casing and quickly eroding a hole through the casing and cement. The depth placement of the nozzles is made by running a mechanical casing collar locator.

The abrasive fluid may typically consist of a light linear gel and low concentrations of sand, and a single jetting process will typically take up to 10 minutes. After the perforation procedure, the hydraulic fracture stimulation treatment is pumped down the coiled tubing-casing annulus. After the first stage has been pumped, subsequent stages are isolated by the on-board packer after perforations have been cut. This technique has the advantage that many coal seams can be stimulated in one run in the hole, potentially saving significant time and expense, and eliminate the need for drill-out of plugs when compared to conventional multi-stage hydraulic fracture methods. Another advantage is the ability to monitor down-hole pressure by monitoring surface pressure of the coil tubing during the treatment as no fluid is being pumped down this string there is no frictional pressure loss to estimate; the resulting data can be utilized to optimize subsequent fracture treatments.

Vertical Well, Open-hole Under-ream with Intercepting Single or Multiple Surface to In-seam Open-hole Horizont al Well(s), Singl e Seam In this technique, a vertical well is drilled utilizing the “Vertical Well, Open Hole, Single Seam, Under-ream” method described earlier. A “target” is then placed in the under-ream section, and the surface to in-seam horizontal well is drilled, typically from 1.0 km distance, and intersects the under-reamed section of the vertical well utilizing sensors in the drill string to detect the target. Two or three passes may be required to hit the target. Typically, a perforated or slotted plastic liner is inserted into the open and un-stimulated horizontal well in order to prevent collapse of the coal. Figure 7 is an illustration of this drilling and completion technique. In actual application, usually two surface to in-seam wells intersect one vertical well at more or less right angles forming what has been called a “Chevron” pattern. Each set of two surface to in-seam wells and one vertical well will drain roughly 1.0 km2. This drilling pattern is illustrated in Figure 8.

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After clean out of the open-hole section of the vertical well, artificial lift equipment is installed, with the pump typically set in or just above the under-ream section. Initially, water and gas, and then primarily gas, flow from the coal seam, into the horizontal well, and into the under-ream section of the vertical well. As in other completions, water is pumped up the tubing, and gas flows up the casing-tubing annulus. This technique was developed in Australia (Queensland) in the late 1990’s and early 2000’s as a response to the lack of or expense of hydraulic fracturing operations, illustrating how available services can influence the drilling and completion decision. While this technique is still in use today, the use of vertical hydraulically fractured wells is much more available and common than in the past. Advantages of this technique are that high recovery of gas in place can be achieved in a short period of time relative to vertical wells, and can be used in areas where hydraulic fracturing capability is lacking. This technique has proven to be economic based on successful projects in Queensland Australia [8, 12]. This technique has also been used to remove gas from coal seams prior to underground mining [12]. Disadvantages include inability to complete more than one coal seam with each set of in-seam wells, and in-seam well stability issues can cause partial or complete loss of an in-seam well section.

Vertical Well, Open-hole Under-ream with Intercepting Surface to In-seam Open-hole Multi-lateral Horizontal Wells Originally developed as a coal mine methane (CMM) method for removing gas from coal seams prior to underground mining for safety reasons, this technique has been used in low permeability high rank coal seams. The technique has been successful in producing significant quantities of gas from low permeability coal seams, but high drilling cost has challenged viable economics. This technique is similar to the previous technique, in that a vertical well is drilled to the top of the coal seam and production casing is run and cemented. The coal seam is then drilled and under-reamed. At this point, a nearby surface to in-seam well is drilled to a depth near the top of the coal seam where a tight radius turn is made and a horizontal in-seam well intersects the under-reamed portion of the vertical well. This is illustrated in Figure 9. The in-seam well is then drilled through the coal typically for approximately 0.7 mile. The drill string is then retracted, and side lateral wells are drilled into the coal seam in a “pinnate” pattern as shown in Figure 10. When drilling is completed, in one pinnate pattern covering 0.25 mi2, as much as 20,000 ft of hole may be drilled [10]. Production is by pump in the vertical well as discussed previously. This type of drilling and completion technique has the same advantages and disadvantages as the previous surface to in-seam technique discussed, with the additional disadvantages; 1) it is not possible to install plastic liners in the multiple lateral wells sections; 2) in relatively thin coal seams and where geologic complexity exists, core hole drilling may be required to properly locate the in-seam well sections.

Process for Determination of Proper Completion Technique Before describing the proposed general procedure for determination of optimal drilling and completion technique, some general principles or concepts will be listed. In general, ranked from high to low permeability (from greater than 50 md to less than 0.1 md), appropriate drilling and completion techniques may be suggested as follows:     

Vertical Well, Open Hole, Single Seam, Under-ream Vertical Well, Open Hole, Single Seam, Cavity Vertical Well, Cased, Perforated, Multi-Seam, Hydraulic Fracture Surface to In-seam Horizontal Wells with Vertical Well Intercepts, Single Seam Multi-lateral, with Vertical Well Intercepts

General Principles:      

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Safety First Utilize Present Value Economics Low development cost tends to be better ($/mcf) Getting the gas out sooner tends to be better Developing everything now tends to be better Multiple zones are difficult and expensive to complete with multiple horizontal wells, but may be easy to complete with single, multi-seam vertical well completions. Single seam, thick, low permeability reservoir may be difficult to develop with vertical wells but may be easy to complete with horizontal wells.

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CBM reservoirs tend to be heterogeneous, and the optimal technique in one area may not be the optimal technique in another. See the San Juan Basin for a good example, where cavity completions are used in the Fairway, and hydraulic fracturing is used to the north and south. Gas price solves many problems – but, is the drilling and completion selection optimized?

The forgoing discussion implies that there are many options available for development of CBM resources, and it may not be clear which one is best. The author suggests the following general work flow as a guide to developing the optimal drilling and completion strategy. Gather critical reservoir parameters:  No attempt to develop an optimal drilling and completion strategy for a CBM resource can succeed unless it takes into consideration all of the critical reservoir parameters. Table 1 lists the critical reservoir  parameters necessary. Time and care should be taken to compile an accurate description of the CBM resource as possible utilizing all the available data. Where parameters are unknown, best estimates must be made based on experience and utilizing the best analog available. Analogs should be similar with respect to coal age and rank, depth, thickness and number of seams, to name a few parameters. It is always good to know how operators have drilled and completed analogous fields, they may have learned a lot through trial and error. Each parameter should be ranked with respect to certainty and economic impact, for example, often depth is known relatively accurately, but permeability may not be known at all; porosity may not  be known but is a critical factor; for example, a difference between coal cleat porosity from 2% to 3% can increase the volume of water lifting by 50%, and may be economically significant due to increased water lifting, handling, and disposal requirements. Sensitivity analysis and Monte Carlo simulation should be considered to quantify overall uncertainty. Utilizing reservoir simulation, perform spacing optimization study for each style of completion to be considered:   Some drilling and completion techniques may be ruled out immediately, for example, it will be difficult to develop a stack of 10 to 15 relatively thin coal seams with horizontal wells, or it may be difficult to develop one thick, deep, and low permeability coal seam with vertical wells. Thus, with experience it may be possible to use general guidelines to screen likely techniques. Again, it is important to look at what operators in analogous fields have done. Once the likely drilling and completion techniques have been identified, reservoir simulation should be used to study and optimize spacing between wells or in-seam laterals. For each case, incremental economics should be run to determine which spacing is optimum for each drilling and completion candidate. Excellent books are available for more information on economic and incremental economic analysis [11].  Run field development economics for each completion style based on optimized spacing:  With optimal spacing estimated, full field development scenarios can be studied for each drilling and completion technique. The development plan should give consideration to total number of wells, location of pipelines and central processing facilities, etc. Net present value economics should be run including capital and operating cost, gas prices, and reasonable timing assumptions [11]. Again, critical unknowns should be identified and quantified with respect to uncertainty. Perform incremental economic analysis to determine the best completion technique:  Once development scenarios have been economically evaluated, incremental economics can be run to compare one drilling and completion technique to another. For example, an area that would require two surface to in-seam wells intersecting a vertical well may require four vertical wells. Each surface to inseam well is more expensive, but less of them are required. The production profiles for the two drilling and completion techniques are different; therefore, one may have better net present value than the other. The surface to in-seam option may develop only one seam, but the vertical well scenario can develop an additional small seam, with resulting additional resource having an impact on project economics.

Summary This paper has discussed the problem of the determination of optimal drilling and completion technique. It is a difficult  problem, one that has been faced in every new CBM development. Technology offers many options and permutations. By knowing the critical reservoir parameters, the options available, and use of incremental economic analysis methodology, it is  possible to intelligently direct efforts to the drilling and completion techniques most likely to produce optimal results.

References 1. 2.

S. Ramaswamy, W.B. Ayers, S.A. Holditch, Texas A&M University, “Best drilling, completion, and stimulation methods for CBM reservoirs”, World Oil, October 2008 A.O. Nasar, S.D. Mohaghegh, G. Vida, Department of Petroleum and Natural Gas Engineering, West Virginia University, “A Parametric Study and Economic Evaluation of Drilling Patterns in Deep, Thick CBM Reservoirs”, SPE 149441

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3. 4. 5. 6.

7.

8. 9.

10.

11. 12. 13.

I. Palmer, Higgs-Palmer Technologies, “The Permeability Factor in Coalbed Methane Well Completions and Production”, SPE 131714 Gas Research Institute, “A Guide to Coalbed Methane Reservoir Engineering”, GRI Reference No. GRI-94/0397 M.J. Mavor, Tesseract Corporation, C.R. Nelson, Gas Research Institute, “Coalbed Reservoir Gas-In-Place Analysis“, GRI Reference No. GRI-97/0263 T.L. Logan, Resource Enterprises, Inc. and W.F. Clark, Blackwood and Nichols Co., LTD and R.A. McBane, Gas Research Institute: “Comparing Openhole Cavity and Cased Hole Hydraulic Fracture Completion Techniques, San Juan Basin, New Mexico”, SPE 19010 I.D. Palmer, Amoco Production Co., M.J. Mavor, Resource Enterprises Inc., J.L. Spitler, J.P. Seidle, and R.F. Volz, Amoco Production Co., “Openhole Cavity Completions in Coalbed Methane Wells in the San Juan Basin”, SPE 24906-PA, 1993. L. Rozman, CH4, “CH4’s Scorecard for 2004/2005”, Presentation given to the Brisbane Mining Club, June 23, 2005  N. Maricic, Chevron Corporation, S.D. Mohaghegh, West Virginia University, A. Emre, Chevron Corporation, “A  parametric Study on the Benefits of Drilling Horizontal and Multilateral Wells in Coalbed Methane Reservoirs”, SPE Reservoir Evaluation and Engineering, December 2008 S.A. Keim, Virginia Polytechnic Institute and State University, “Optimization of Coalbed Methane Completion Strategies, Selection Criteria and Production Prediction: A Case Study in China’s Qinshui Basin”, Doctoral Dissertation, August 18, 2011 F.J. Stermole, J.M. Stermole, “Economic Evaluation and Investment Decision Methods”, Publisher: Investment Evaluations Corporation, Published: January 1, 2009 J. Caballero, personal knowledge. Kris Nygaard, ExxonMobil Production Company, Shekhar Gosavi and Pavlin Entchev, ExxonMobil Development Company, Fuping Zhou, Wadood El-Rabaa, and Chris Shuchart, ExxonMobil Upstream Research Company, “Improved Methods and Workflows for Multi-Zone Stimulation”, IPTC-16865, March 2013

Figures

Table 1 Critical Reservoir Parameters Necessary to Evaluate Optimal Drilling and Completion Technique

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Table 2 Illustrating General Relationship between Completion Type and Permeability

 

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Figure 1 Vertical Open-hole Under-ream Completion

 

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Figure 2 Illustration of an Under-reaming Tool

Figure 3 Vertical Open-hole Cavity Completion

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Figure 4 Illustration of Typical Density and Sonar Log in a Cavitated Well

Figure 5 Simplified Plan View of a Cavity Completion

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Figure 6 Schematic of a Vertical Cased Hole Multi-seam Hydraulic Fracture Completion

Figure 7 Surface to In-seam Horizontal Well

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Figure 8 Example Development Well Layout for Surface to In-seam Horizontal Wells

Figure 9 Surface to In-seam Multi-lateral Well

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Figure 10 Schematic Plan View of Two Multi-lateral “Pinnate” Patterns