US20130255942A1

US20130255942A1 - Accelerated Coalbed Methane Dewatering Using CO2 Injection

Info

Publication number: US20130255942A1
Application number: US13/787,618
Authority: US
Inventors: Edward C. Wanat
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-03-29
Filing date: 2013-03-06
Publication date: 2013-10-03

Abstract

A method for producing methane from a coalbed formation including the accelerated dewatering of the coalbed formation including determining the location of water influx into the coal formation and determining an area to form a permeability barrier in the coal formation to reduce the water influx into the coal formation. A strongly adsorbing fluid is injected through one or more injection wells into the area to form a permeability barrier to the influx of the water. One or more methane production wells are drilled into the coal formation and methane is produced from the coal formation.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of U.S. Provisional Patent Application 61/617,294 filed Mar. 29, 2012 entitled ACCELERATED COALBED METHANE DEWATERING USING CO₂INJECTION, the entirety of which is incorporated by reference herein.

FIELD OF THE INVENTION

Embodiments of the present invention are directed toward the dewatering of coalbed methane, and more specifically, towards the dewatering of coalbed methane that is experiencing water influx from an external source.

BACKGROUND

This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present techniques. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present techniques. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
Solid carbonaceous subterranean formations, such as coal, often contain commercially viable quantities of natural gas, made up of light hydrocarbons including, but not limited to, methane and ethane, in an adsorbed state on the coal surface. In many locations the recovery of this natural gas represents a significant energy resource. In the case of coal mining, this natural gas represents an environmental hazard because natural gas is known as a greenhouse gas, and a safety hazard because natural gas can explode in the subsurface when mixed with air at proper ratios. Thus, it has been recognized that the recovery of the natural gas stored in an adsorbed state in subterranean coal reservoirs would have economic, environmental, and safety benefits.
The amount of natural gas that can be produced from a solid carbonaceous subterranean formation is often described by a desorption isotherm which describes the amount of natural gas the coal can adsorb as a function of pressure while maintaining a constant temperature. When natural gas is sorbed to the surface it can be said to be bound to that surface and unable to flow to a wellbore for production. In general, desorption isotherms show coal is able to store increasing amounts of natural gas with increasing pressure. Hence, the recovery of adsorbed natural gas is accomplished through decreasing the reservoir pressure, allowing the natural gas sorbed on the surface to become desorbed or unbounded and able to flow to the wellbore.
Subterranean coal reservoirs often contain fractures called cleats that provide a path for natural gas to flow once desorbed from the surface through a reduction in reservoir pressure. However, these cleats are often saturated with water. The water present in these types of fractures generally causes multiple problems. The first problem is the impedance of the flow of natural gas to wells due to relative permeability effects. These effects generally lead to lower flow rates of gas and less gas produced over the lifetime of the well. The second problem is a portion of this water present in the reservoir can be produced along with the natural gas. The water being produced with the natural gas imposes a cost for the operator of the well due to the required treatment, transportation, and disposal of the produced water. Finally, the water present in the cleats provides pressure support to the subterranean coal reservoir which acts to keep the natural gas in the adsorbed state in the coal.
In many subterranean coalbed natural gas reservoirs, the permeability is sufficiently high to allow for the production of water at sufficient rates to appreciably decrease the amount of water present in the reservoir, and hence the reservoir pressure, allowing natural gas to flow at increased, and commercial, rates. This places those entities that produce natural gas from such subterranean coal reservoirs in a paradox. Increased production of water will generally lead to increased production of natural gas due to relative permeability effects, but also increase costs of production due to increased water production. Currently, operators choose to deal with the paradox of increased gas production while increasing costs for the handling of produced water by accepting the increased costs of water handling in order to produce more gas. This decision is driven by the need to reduce reservoir pressure in order to cause gas to desorb and flow to the well bore.
The process of dewatering solid carbonaceous subterranean formations may be complicated if the formation is an open system in which water not originally present in the coal when the dewatering begins can flow into the coal. The water encroaching into the coal from outside often comes from an adjacent or non-adjacant formation through flow pathways present in the subsurface or through meteoric recharge from the surface. The inflow of water into the coal from outside makes the job of dewatering more difficult as more water has to be removed at higher cost than if the coal was a closed system or did not have water from the outside entering the coal. In some coals with very high influx of water it has been reported that operators have not been able to remove enough water to obtain gas flow rates at commercial rates. These seams of coal have to be bypassed for production in favor of those coal seams that have lower rates of water removal to obtain commercial gas production.
The production of natural gas from solid carbonaceous subterranean formations can be enhanced by the flooding of the subterranean reservoir with a strongly adsorbing gas, such as CO₂, which is preferentially adsorbed onto the surface of the coal compared to the desirable light hydrocarbons that will be displaced from the coal's surface. In addition to the benefit of increased production of natural gas, a second benefit is that CO₂is a greenhouse gas that is sequestered by its adsorption onto the coal. While not as commonly practiced in producing solid carbonaceous subterranean formations as water production to reduce reservoir pressure the process is described many places in literature. U.S. Pat. No. 6,412,559 (Gunter et al, Jul. 2, 2002) describe a process in which an injection well is drilled into a subterranean coalbed reservoir and fractured. Then a more strongly adsorbing gas than methane is injected into the well and the well shut in allowing the more strongly adsorbing gas than methane to soak into the subterranean coal reservoir causing the methane to desorb from the coal and flow to the production well.
One draw-back of using a gas more strongly adsorbing than methane such as CO₂is that CO₂adsorption causes the coal to swell which decreases the permeability of the coal by reducing the apertures of the cleats and decreases the recovery of natural gas. Palmer and Mansoori and others have developed relationships that describe the coal matrix shrinkage/swelling that express permeability changes of coal that can be expected due to the changes in porosity that occur when gases such as CO₂are sorbed on the surface. (Palmer, I. and Mansoori, J., “How Permeability Depends on Stress and Pore Pressure in Coalbeds: A New Model,” SPE 36767, Procs. 71st Ann. Tech. Conf. Denver, Colo., October 1996; Palmer, I. and Mansoori, J., “How Permeability Depends on Stress and Pore Pressure in Coalbeds: A New Model,” SPE 52607, SPEREE, December 1998, pp. 539-544; and Levine, J. R., “Model Study of the Influence of Matrix Shrinkage on Absolute Permeability of Coal Bed Reservoirs,” in Gayer, R and Harris, I. (eds), Coalbed Methane and Coal Geology, Geol. Soc. Special Pub. No. 109, pp.
197-212, 1996). Using these relations, Pekot and Reeves reported permeability decreases of over 90% in numerical simulations and from analysis of CO₂injection field trials in the San Juan basin (Pekot, L. J. and Reeves, S. R., “Modeling Coal Matrix Shrinkage and Differential Swelling with CO2 Injection for Enhanced Coalbed Methane Recovery and Carbon Sequestration Applications,” Topical Report, Advanced Resources International for U.S. Department of Energy, contract DE-FC26-00NT40924, November, 2002). Perhaps unexpectedly; however, the injectivity of CO₂was reported to improve with time in the field trial reported by Pekot and Reeves suggesting that resistance in the near well bore flow decreases allowing CO₂flooding to continue.
The need exists for new approaches to improve the performance of production of coalbed methane by reducing the amount of water that needs to be removed from the coal formation. In addition, the need exists to sequester the greenhouse gas, CO₂, in subterranean solid carbonaceous subterranean formations in which it contributes to the increased production of valuable hydrocarbons while removing the CO₂from possible emission to the atmosphere.
An additional object of this invention is to provide a means to render coal mining safer, with respect to ensuring more efficient and complete dewatering of the coals and the removal of potentially explosive light hydrocarbons prior to the extraction of the coal.

SUMMARY OF INVENTION

One or more embodiments of the present invention provide a method for producing methane from a coalbed formation including the accelerated dewatering of the coalbed formation. The method includes determining the location of water influx into the coal formation and determining an area to form a permeability barrier in the coal formation to reduce the water influx into the coal formation. A strongly adsorbing fluid, such as, for example, carbon dioxide, is injected through one or more injection wells into the area to form a permeability barrier to the influx of the water. The permeability barrier is formed by the strongly adsorbing fluid adsorbing into the coal formation and causing the coal formation to swell. Swelling of the coal formation reduces the apertures of the cleats and fractures within the coal formation and thereby reduces the permeability of the coalbed formation. With the permeability reduced, the permeability barrier reduces the influx of water into the coalbed formation. One or more methane production wells are drilled into the coal formation and methane is produced from the coal formation.
One or more embodiments of the present invention provide a method of fracturing the coalbed formation with the strongly adsorbing fluid to increase the area contacted with the strongly adsorbing fluid. In addition, the injection wells may be horizontal or deviated wells to further increase the area contacted with the strongly adsorbing fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the present techniques may become apparent upon reviewing the following detailed description and drawings of non-limiting examples of embodiments in which:

FIG. 1 is a side view of an exemplary illustration of a coalbed formation according to an embodiment of the present invention;

FIG. 2 is a plan view of the exemplary illustration of a coalbed formation according to an embodiment of the preset invention;

FIG. 3 is another plan view of the exemplary illustration of a coalbed formation according to an embodiment of the preset invention;

FIG. 4 is a process flow chart of methods of accelerated dewatering of a coalbed formation in accordance with certain embodiments of the present invention; and

FIG. 5 is process flow chart of methods of accelerated dewatering of a coalbed formation in accordance with certain embodiments of the present invention.

DETAILED DESCRIPTION

In the following detailed description section, the specific embodiments of the present techniques are described in connection with preferred embodiments. However, to the extent that the following description is specific to a particular embodiment or a particular use of the present techniques, this is intended to be for exemplary purposes only and simply provides a description of the exemplary embodiments. Accordingly, the invention is not limited to the specific embodiments described below, but rather, it includes all alternatives, modifications, and equivalents falling within the true spirit and scope of the appended claims.
Embodiments herein relate to a method for improving coalbed methane recovery by making use of one or more strongly adsorbing and coal swelling injectants. An embodiment targets subterranean solid carbonaceous formations that contain water influx. In an embodiment, the permeability pathways in the subterranean solid carbonaceous subterranean formations are caused to be restricted, reducing the amount of water influx into the reservoir. The reduction in permeability is accomplished by injecting one or more strongly adsorbing and swelling injectants into the subterranean coal reservoir near the source of the water influx. The injectant will then adsorb onto the coal surface causing the coal to swell, reducing the size of cleat aperture, i.e. reducing the interior volume of the fractures and pathways in the coal, and reducing the permeability of the coal to water. By reducing the permeability of the coal near the source of the water influx, the amount of water needing to be removed from the coal to achieve commercial gas production is reduced. This will enhance coalbed methane recovery by allowing producers in the reservoir to dewater the coal more quickly causing accelerated production of coalbed methane.
Strongly adsorbing means a fluid that is more strongly adsorbing than methane or other hydrocarbons typically found adsorbed in coals such as, but not limited to, ethane, propane, and butane. One possible fluid, found in abundance, that is more strongly adsorbing than methane is carbon dioxide. By being more strongly adsorbing than the hydrocarbons typically found adsorbed in coals, the injectant will, given time, replace the adsorbed methane and other hydrocarbons present on the coal by being adsorbed itself in the same or different locations on the surface of the coal as where the methane was adsorbed.
Coal swelling means that the volume of the coal increases once the strongly adsorbing material becomes sorbed onto the surface of the coal in a manner described earlier. Upon the increase in coal volume, the volume of the cleats, and other fractures and pathways, will decrease causing a decrease in the permeability of the coal. In an embodiment, the injectant will contain both properties of being more strongly adsorbing than methane and to cause the coal to swell upon adsorption. An injectant that is more strongly adsorbing than methane but not swelling will not cause the closing of the cleats required to reduce permeability and hence reduce water flow into the coal. A gas that causes coals to swell, but is not strongly adsorbing will not adsorb onto the surface of the coal to cause it to swell, also not causing the necessary reduction in permeability to water.
Referring to FIGS. 1 and 2, an embodiment of the invention may be applied to the sides or flanks of a solid carbonaceous subterranean formation 102 experiencing an influx of water 104 into the coal. One or more vertical injection wells 106 drilled into or through the solid carbonaceous subterranean formation 102 are used to inject the strongly adsorbing fluid directly into the solid carbonaceous subterranean formation 102. Preferably the injected strongly adsorbing fluid is applied over the entire height 108 of the solid carbonaceous subterranean formation 102 to create a permeability barrier 111 and to ensure that all possible flow paths into the coal are affected. It is also preferred that a series of injector wells 106 are used, if required, to ensure complete saturation of the coal with the strongly adsorbing fluid so that the permeability barrier 111 reaches across the solid carbonaceous subterranean formation 102 to prevent as much water influx 104 into the solid carbonaceous subterranean formation 102 as possible. In the case where it is not possible to cover the entire field of water influx due to topography, land lease considerations, or other obstacles, creating the largest permeability barrier as reasonably possible is desired. One or more production wells 112 produce the methane and other hydrocarbons present in the coal.
It is desirable to create the permeability barrier in such a way that it is as thin as possible. There are several advantages to a thin permeability barrier over a thicker barrier. First, the amount of strongly adsorbing fluid that must be purchased is reduced when a thin barrier can be created, improving the economics of the project. Second, as the reduced permeability of the portion of the solid carbonaceous subterranean formation used for the creation of the permeability barrier will likely preclude that section from later use as a producing reservoir, the volume sacrificed to creation of the barrier should be kept to a minimum. Third, thinner barriers result in lower likelihood of any disruption to the natural environment other than the desired permeability barrier and any required remediation once the production of natural gas is complete will be easier and less expensive.
In an embodiment, the injection wells include a method of increasing the surface area contacting the wellbore to the reservoir in order to increase the efficiency of injecting the strongly adsorbing fluid or to increase the amount of coal contacted by the strongly adsorbing fluid. For example, in one embodiment of this invention the injection wells can be fractured prior to injecting the strongly adsorbing fluid. While multiple methods for fracturing a solid carbonaceous subterranean formation are described in the literature, any of the methods will be compatible with the current invention as long as the fracturing method allows for injection of the strongly adsorbing fluid once the fracturing processes are complete. For example, in an embodiment, the coal may be hydraulically fractured with the use of a fluid containing a proppant prior to the injection of the strongly adsorbing fluid. The purpose of the proppant is to keep the hydraulic fracture open in order to improve the injectivity of the strongly adsorbing fluid. The strongly adsorbing fluid would then be pumped down the wellbore and through the created hydraulic fracture containing proppant into the formation. The purpose of hydraulically fracturing the formation prior to injecting strongly adsorbing fluid would be to increase the surface area between the formation and the injection point of the strongly adsorbing fluid, reducing the number of wells required to create the permeability barrier. In this embodiment, it is desired that the proppant not reach the cleat apertures, but rather remain within the hydraulic fracture. If it is not possible to inject the strongly adsorbing fluid once the fracturing is complete then that method of fracturing should be avoided.
It is also possible to fracture the solid carbonaceous subterranean formation using the same fluid as the strongly adsorbing fluid used to cause the coal to swell. It is preferable that the strongly adsorbing fluid be used for fracturing where possible so that two steps in the field, fracturing followed by injection, are consolidated into one in which injection of the strongly adsorbing fluid is continued after the fracturing is completed. Thus, the injection of the fluid may be at a pressure at or above a fracture pressure of the solid carbonaceous subterranean formation. In some embodiments, such as when fracturing is not desired or after fracturing of the formation, the injection of the fluid may be below a fracture pressure of the solid carbonaceous subterranean formation.
In an embodiment, the size of the borehole may be increased to increase the surface area contact between the coal and wellbore prior to injecting the strongly adsorbing fluid. A few examples would include under-reaming of the hole and cavitation of the coal. By increasing the effective size of the wellbore through hydraulically fracturing, under-reaming, cavitation, or other methods prior to the injection of strongly adsorbing fluid, the contact surface area between the formation and the wellbore is increased. By increasing the surface area it is possible to more easily contact a larger volume of coal with the strongly adsorbing fluid compared to the use of a smaller effective wellbore. This is desirable as it would then be possible to create an effective barrier to water influx from external sources with fewer adsorbing fluid injection wells if each well can contact a larger volume of coal. This would lead to reduced costs and improved project economics. Once again any method used to increase the borehole size should only be used if it does not prevent the injection of the strongly adsorbing fluid into the coal once the operations to increase the size of the borehole are complete.
Another embodiment of the invention would involve the use of horizontal wells or deviated wells for injection of the strongly adsorbing gas into the solid carbonaceous subterranean formation. Horizontal or deviated wells represent another method in which to increase the area contacted by the injector with the reservoir. A horizontal well or deviated well may work well in cases where the desired solid carbonaceous subterranean formation is thin making the amount of reservoir contacted by a vertical well especially low. Another case in which a horizontal or deviated well may be desirable is when the permeability of the solid carbonaceous subterranean formation is especially low, making it difficult to inject the strongly adsorbing fluid deep into the reservoir. The increased area contacted by a horizontal or deviated well means it is less critical to be able to inject long distances into the solid carbonaceous subterranean formation. Methods described above, including fracturing, under-reaming, etc., can be used to further increase the contact area of the well with the solid carbonaceous subterranean formation in a horizontal or deviated well; however, the same cautions apply in that the ability to inject the strongly adsorbing fluid must be maintained once the operations to increase the surface area of the wellbore-reservoir contact are complete.
Another embodiment of the invention involves the use of injectors to create permeability barriers along lease lines. As it is no benefit to produce water from a neighboring lease, the invention can be used to place a permeability barrier along a lease line that will act to prevent water from the neighboring acreage from flowing into the production wells. Such a barrier prevents the neighbor from having their acreage dewatered at no cost to them and helps dewater the solid carbonaceous subterranean formation of interest much quicker than would otherwise be possible. The operation of the injectors would be similar to that described above except that well placement of both the strongly adsorbing fluid injectors and the coalbed methane producers would have to be planned so that the permeability barrier is created along the lease line with a minimum amount of acreage being used for the construction of the permeability barrier as it is desirable to use as much acreage for coalbed methane production as possible.
Referring to FIG. 3, illustrated is a plan view of an embodiment of the invention in which a permeability barrier 302 is created within a coalbed methane formation 303 along a lease line 304. The coalbed methane formation is experiencing water influx 305. The lease line 304 separates a neighboring lease 306 from the lease to be produced 308. The permeability barrier is created with the use of one or more injection wells 310, as described above. The permeability barrier 302 prevents or reduces additional water influx from the neighboring lease 306 into the lease to be produced 308. Production wells 312 are also indicated.
In an embodiment, the injection of the strongly adsorbing fluid could also utilize periodic or non-periodic injection pulses. The injection pulses may help the fluid penetrate further into the coal formation and/or reach additional coal surface area, than would otherwise occur. Additionally, the use of periodic or non-periodic injection pulses may allow flexibility and down-time for operational issues, such as maintenance of equipment, etc.
Depending on reservoir conditions, the amount of swelling by the coal matrix may decrease over time, especially after injection of the adsorbing fluid has ceased, causing the cleat apertures to increase and causing an increase in permeability. There are many potential causes for the decrease in the swelling of the coal matrix, for example, stripping of the strongly adsorbing fluid due to water flow through the coal would cause the coal to stop swelling, increase cleat aperture, and restore permeability back to the coal. Hypothetically, weakening of the permeability barrier can be unintentional or induced, for example, part of a regulatory requirement to restore water flow in the coal seam once production is complete.
In an embodiment, the fluid that is injected may be at a temperature that is above ambient temperature, or which has been cooled through the use of a cooler to near ambient temperature. Fluid temperature is important because adsorption is related to temperature; in theory, the amount of gas a coal can adsorb decays exponentially with increasing temperature of the fluid. Hence use of a warmer temperature fluid, for example, the flue gas from a power plant, can affect how the fluid adsorbs on the surface of the coal. A warmer fluid would transfer some of its heat to the coal, reducing the amount of strongly adsorbing gas that would adsorb on the coal surface, causing lower levels of matrix swelling, meaning the cleat apertures would not close as much as they would with the use of a cooler fluid. Depending on the temperature of the strongly adsorbing fluid, adsorption isotherm of the coal, and the swelling properties of the coal, the input temperature of the strongly adsorbing fluid may need to be monitored.
Referring to FIG. 4, illustrated is a process flow chart of methods of accelerated dewatering of a coalbed formation in accordance with certain embodiments of the present invention. The process 400 includes injecting 402 a strongly adsorbing species or fluid, such as, for example, carbon dioxide, through an injection well into a solid carbonaceous subterranean formation at or close to the edge of the direction of water influx into solid carbonaceous subterranean formation. The injection of the strongly adsorbing fluid may be continued 404 for a period of time long enough until further injection does not become feasible due to coal swelling. The injection may be stopped 406 and concurrently and/or sequentially 408 repeat steps 402-406 for other injection wells in the solid carbonaceous subterranean formation such that a permeability barrier is created. Concurrently or following 410 steps 402-408 in an area of the solid carbonaceous subterranean formation in a direction opposite from the direction of water influx from where the injection described in steps 402-408, operate one or more producing wells in a manner typical for coalbed methane recovery.
Referring to FIG. 5, illustrated is a process flow chart of methods of accelerated dewatering of a coalbed formation in accordance with certain embodiments of the present invention. The process 500 includes determining 502 the location of water influx into the coal formation, determining 504 an area to form a permeability barrier in the coal formation to reduce the water influx into the coal formation, injecting 506 a strongly adsorbing species or fluid through an injection well into the area to form a permeability barrier, drilling 508 methane production wells into the coal formation, and producing 510 methane from the coal formation.
Operating producing wells in the embodiments described do not change appreciably from standard methods of producing coalbed methane. As described earlier, the pressure of the solid carbonaceous subterranean formation will need to be reduced in order to cause the coalbed methane to flow at commercial rates. The invention described here is designed to prevent pressure support from areas external to the solid carbonaceous subterranean formation from occurring. In the ideal case, the permeability barrier created will have no effect on the operations of the producing wells, other than reducing the amount of water pumped from the producing wells and increasing the gas rate from those same wells. The producing wells are likely to be away from the very flanks of the basin, which is where the injectors creating the permeability barrier are located. It is likely desirable that the producing well operations occur simultaneously with the creation of the permeability barrier. In this way the dewatering of the solid carbonaceous subterranean formation can occur and production of gas can occur as soon as possible.

EMBODIMENTS

Embodiments of the invention may include any combinations of the methods and systems shown in the following numbered paragraphs. This is not to be considered a complete listing of all possible embodiments, as any number of variations can be envisioned from the description above.
1. A method for producing methane from a coalbed formation, the method comprising:

- determining the location of water influx into the coal formation;
- determining an area to form a permeability barrier in the coal formation to reduce the water influx into the coal formation;
- injecting a strongly adsorbing fluid through one or more injection wells into the area to form a permeability barrier;
- drilling one or more methane production wells into the coal formation; and producing methane from the coal formation.

2. The method of paragraph 2, wherein the strongly adsorbing fluid is selected from the group consisting of carbon dioxide, nitric acid, sulfur hexafluoride, hydrogen sulfide, sulfur dioxide, nitrogen dioxide, sulfur trioxide, trichlorofluoromethane, dichlorofluoromethane, chlorotrifluoromethane, tetrafluoromethane, dichloromonofluoromethane, fluoroform, 1,1,2-trichloro-1,2,2-trifluoroethane, dichlorotetrafluoroethane, hexafluoroethane, chloropentafluoroethane, Lewis base donor molecules with high basicity, primary, secondary, or tertiary amines, alkylamines, aromatic amines, molecules with several amine functions, lactams, amines, urea and its derivatives, pyridine, ammonia, methylamine, buytlamine, tetramethyl ethylenediamine, 1,4-dimethylpiperazine, ethylmethylamine, N-methylpyrollidone, N-methylpyridone, N,N-dimethylformamide and combinations thereof.
3. The method of any of the preceding paragraphs, wherein injecting a strongly adsorbing fluid through one or more injection wells into the area to form a permeability barrier comprises fracturing the coalbed formation by the strongly adsorbing fluid.
4. The method of any of the preceding paragraphs, wherein the one or more injection wells are horizontal or deviated.
5. The method of any of the preceding paragraphs, wherein the one or more injection wells further comprise increasing the surface area contact between the wellbore and the coalbed formation.
6. The method of any of the preceding paragraphs, wherein the strongly adsorbing fluid reduces the cleat permeability.
7. The method of any of the preceding paragraphs, further comprising treating the well with periodic or non-periodic injection pulses of the strongly adsorbing fluid.
8. The method of any of the preceding paragraphs, further comprising injecting the strongly adsorbing fluid at temperatures other than ambient temperatures.
9. The method of any of the preceding paragraphs, wherein injecting a strongly adsorbing fluid through one or more injection wells into the area to form a permeability barrier further comprises injecting the strongly adsorbing fluid at a pressure at or above a fracture pressure of the coalbed formation.
10. The method of any of the preceding paragraphs, wherein injecting a strongly adsorbing fluid through one or more injection wells into the area to form a permeability barrier further comprises injecting the strongly adsorbing fluid at a pressure below a fracture pressure of the coalbed formation.
11. The method of any of the preceding paragraphs, wherein the strongly adsorbing fluid causes the coal formation to swell.
12. The method of any of the preceding paragraphs, wherein the swelling of the coal formation by the strongly adsorbing fluid decreases over time.
13. The method of any of the preceding paragraphs, wherein the step of performing the treatment contains solid proppant.
While the present techniques of the invention may be susceptible to various modifications and alternative forms, the exemplary embodiments discussed above have been shown by way of example. However, it should again be understood that the invention is not intended to be limited to the particular embodiments disclosed herein. Indeed, the present techniques of the invention are to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.

Claims

What is claimed is:

1. A method for producing methane from a coalbed formation, the method comprising:

determining the location of water influx into the coal formation;

determining an area to form a permeability barrier in the coal formation to reduce the water influx into the coal formation;

injecting a strongly adsorbing fluid through one or more injection wells into the area to form a permeability barrier;

drilling one or more methane production wells into the coal formation; and

producing methane from the coal formation.

2. The method of claim 1, wherein the strongly adsorbing fluid comprises carbon dioxide.

3. The method of claim 1, wherein the strongly adsorbing fluid is selected from the group consisting of carbon dioxide, nitric acid, sulfur hexafluoride, hydrogen sulfide, sulfur dioxide, nitrogen dioxide, sulfur trioxide, trichlorofluoromethane, dichlorofluoromethane, chlorotrifluoromethane, tetrafluoromethane, dichloromonofluoromethane, fluoroform, 1,1,2-trichloro-1,2,2-trifluoromethane, dichlorotetrafluoroethane, hexafluoroethane, chloropentafluoroethane, Lewis base donor molecules with high basicity, primary, secondary, or tertiary amines, alkylamines, aromatic amines, molecules with several amine functions, lactams, amines, urea and its derivatives, pyridine, ammonia, methylamine, buytlamine, tetramethyl ethylenediamine, 1,4-dimethylpiperazine, ethylmethylamine, N-methylpyrollidone, N-methylpyridone, N,N-dimethylformamide and combinations thereof.

4. The method of claim 1, wherein injecting a strongly adsorbing fluid through one or more injection wells into the area to form a permeability barrier comprises fracturing the coalbed formation with the strongly adsorbing fluid.

5. The method of claim 1, wherein the one or more injection wells are horizontal or deviated.

6. The method of claim 1, wherein the one or more injection wells further comprise increasing the surface area contact between the wellbore and the coalbed formation.

7. The method of claim 1, wherein the coal formation comprises one or more cleats and wherein the strongly adsorbing fluid reduces the cleat apertures.

8. The method of claim 1, further comprising treating the well with periodic or non-periodic injection pulses of the strongly adsorbing fluid.

9. The method of claim 1, further comprising injecting the strongly adsorbing fluid at temperatures other than ambient temperatures.

10. The method of claim 1, wherein injecting a strongly adsorbing fluid through one or more injection wells into the area to form a permeability barrier further comprises injecting the strongly adsorbing fluid at a pressure at or above a fracture pressure of the coalbed formation.

11. The method of claim 1, wherein injecting a strongly adsorbing fluid through one or more injection wells into the area to form a permeability barrier further comprises injecting the strongly adsorbing fluid at a pressure below a fracture pressure of the coalbed formation.

12. The method of claim 1, wherein the strongly adsorbing fluid causes the coal formation to swell.

13. The method of claim 11, wherein the swelling of the coal formation by the strongly adsorbing fluid decreases over time.

14. The method of claim 1, further comprising injecting a solid proppant into the one or more injection wells into the area.