CA2196369C - Chemically induced stimulation of coal cleat formation - Google Patents
Chemically induced stimulation of coal cleat formation Download PDFInfo
- Publication number
- CA2196369C CA2196369C CA002196369A CA2196369A CA2196369C CA 2196369 C CA2196369 C CA 2196369C CA 002196369 A CA002196369 A CA 002196369A CA 2196369 A CA2196369 A CA 2196369A CA 2196369 C CA2196369 C CA 2196369C
- Authority
- CA
- Canada
- Prior art keywords
- coal formation
- methane
- formation
- well
- coal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 230000015572 biosynthetic process Effects 0.000 title claims abstract description 117
- 239000003245 coal Substances 0.000 title claims abstract description 106
- 230000000638 stimulation Effects 0.000 title description 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 106
- 238000004519 manufacturing process Methods 0.000 claims abstract description 49
- 239000007800 oxidant agent Substances 0.000 claims abstract description 49
- 230000001590 oxidative effect Effects 0.000 claims abstract description 48
- 238000000034 method Methods 0.000 claims abstract description 35
- 230000001965 increasing effect Effects 0.000 claims abstract description 21
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical class OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims abstract description 18
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical class [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 claims abstract description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical class [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 7
- 239000001301 oxygen Chemical class 0.000 claims abstract description 6
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 6
- 239000000243 solution Substances 0.000 claims description 44
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 35
- 238000002347 injection Methods 0.000 claims description 28
- 239000007924 injection Substances 0.000 claims description 28
- 230000035699 permeability Effects 0.000 claims description 14
- 239000012530 fluid Substances 0.000 claims description 5
- 239000007864 aqueous solution Substances 0.000 claims description 2
- 230000002708 enhancing effect Effects 0.000 claims description 2
- 238000005755 formation reaction Methods 0.000 abstract description 94
- WQYVRQLZKVEZGA-UHFFFAOYSA-N hypochlorite Chemical compound Cl[O-] WQYVRQLZKVEZGA-UHFFFAOYSA-N 0.000 abstract description 4
- 239000008398 formation water Substances 0.000 abstract description 2
- 230000004936 stimulating effect Effects 0.000 abstract description 2
- QWPPOHNGKGFGJK-UHFFFAOYSA-N hypochlorous acid Chemical class ClO QWPPOHNGKGFGJK-UHFFFAOYSA-N 0.000 abstract 1
- 150000003839 salts Chemical class 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 7
- 238000011084 recovery Methods 0.000 description 6
- 230000008569 process Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 230000000149 penetrating effect Effects 0.000 description 4
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000011282 treatment Methods 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 150000002978 peroxides Chemical class 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000002203 pretreatment Methods 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/84—Compositions based on water or polar solvents
- C09K8/845—Compositions based on water or polar solvents containing inorganic compounds
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
- C09K8/66—Compositions based on water or polar solvents
- C09K8/665—Compositions based on water or polar solvents containing inorganic compounds
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/006—Production of coal-bed methane
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/17—Interconnecting two or more wells by fracturing or otherwise attacking the formation
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/27—Methods for stimulating production by forming crevices or fractures by use of eroding chemicals, e.g. acids
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Mining & Mineral Resources (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Organic Chemistry (AREA)
- Environmental & Geological Engineering (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Geochemistry & Mineralogy (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Solid Fuels And Fuel-Associated Substances (AREA)
- Treatment Of Sludge (AREA)
- Extraction Or Liquid Replacement (AREA)
Abstract
A method for increasing the production of methane from a subterranean coal formation by chemically stimulating the formation of cleats in the coal formation in order to facilitate removal of formation water, and increase the rate of methaneproduction from the coal formation.
The method comprises injecting an aqueous oxidant solution into the coal formations to stimulate the formation of cleats in the coal formation; and thereafter producing methane from the coal formations at an increased rate. The aqueous oxidant solution preferably comprises hypochlorite, metaic salts of hypochlorous acid, hydrogen peroxide, ozone, oxygen and combinations thereof.
The method comprises injecting an aqueous oxidant solution into the coal formations to stimulate the formation of cleats in the coal formation; and thereafter producing methane from the coal formations at an increased rate. The aqueous oxidant solution preferably comprises hypochlorite, metaic salts of hypochlorous acid, hydrogen peroxide, ozone, oxygen and combinations thereof.
Description
CHEMICALLY INDUCED STIMULATION
OF COAL CLEAT FORMATION
Field of the Invention ' This invention relates to methods for increasing the rate of production of methane from subterranean coal formations by chemically stimulating the cleat system in the coal formation to increase the production rate of methane from the coal formation.
Brief Descri,~tion of the Prior Art Substantial quantities of methane gas are found in subterranean coal formations.
A variety of processes have been used in attempts to recover the methane from the coal formations more efficiently.
The simplest process is the pressure reduction process wherein a borehole is drilled into a coal formation from the surface and methane is withdrawn from the borehole by reducing the pressure to cause methane to be desorbed from and flow from the coal formation into the borehole and to the surface. This method is not e~cient because coal formations are generally not extremely porous and the methane is generally not found in the pores of the coal formation but is absorbed onto the coal. While methane can be produced from coal formations by this process, the production of methane is relatively slow.
In some coal formations, the natural permeability is su~cient to allow the removal of in situ water to permit the enhanced recovery of methane. In such formations, cleat systems developed during the coal bed diagenesis provide channel ways through which water and methane migrate to the production wells for removal. This removal of water or "de-watering"
of the coal formations removes water from the channel ways and permits the flow of methane through the channel ways and to a production well at a greater rate.
Many coal formations do not have extensively developed cleat systems or have cleat systems which are not fully developed. These coal formations have very low permeability to water and do not yield their water at significant rates. As a result, the water fills the channels, and the recovery of methane from such coal formations is difficult or impossible at significant rates.
Accordingly, continuing efforts have been directed to the development of methods for recovering methane from such coal formations at an increased rate.
OF COAL CLEAT FORMATION
Field of the Invention ' This invention relates to methods for increasing the rate of production of methane from subterranean coal formations by chemically stimulating the cleat system in the coal formation to increase the production rate of methane from the coal formation.
Brief Descri,~tion of the Prior Art Substantial quantities of methane gas are found in subterranean coal formations.
A variety of processes have been used in attempts to recover the methane from the coal formations more efficiently.
The simplest process is the pressure reduction process wherein a borehole is drilled into a coal formation from the surface and methane is withdrawn from the borehole by reducing the pressure to cause methane to be desorbed from and flow from the coal formation into the borehole and to the surface. This method is not e~cient because coal formations are generally not extremely porous and the methane is generally not found in the pores of the coal formation but is absorbed onto the coal. While methane can be produced from coal formations by this process, the production of methane is relatively slow.
In some coal formations, the natural permeability is su~cient to allow the removal of in situ water to permit the enhanced recovery of methane. In such formations, cleat systems developed during the coal bed diagenesis provide channel ways through which water and methane migrate to the production wells for removal. This removal of water or "de-watering"
of the coal formations removes water from the channel ways and permits the flow of methane through the channel ways and to a production well at a greater rate.
Many coal formations do not have extensively developed cleat systems or have cleat systems which are not fully developed. These coal formations have very low permeability to water and do not yield their water at significant rates. As a result, the water fills the channels, and the recovery of methane from such coal formations is difficult or impossible at significant rates.
Accordingly, continuing efforts have been directed to the development of methods for recovering methane from such coal formations at an increased rate.
Summary of the Invention According to one aspect of the invention there is provided a method of enhancing the permeability to methane of a water-containing subterranean coal formation having a low permeability to methane and penetrated by at least one well, the method consisting essentially of a) injecting an aqueous oxidant solution into the coal formation;
b) maintaining the aqueous oxidant solution in the coal formation for a selected time to enhance or stimulate the formation of cleats in the coal formation;
c) removing sufficient water from the coal formation to open passage-ways in the cleats so that methane can be produced through the passage-ways; and d) producing methane from the coal formation at an increased rate.
According to another aspect of the invention, there is provided a method of increasing the permeability to methane of a water-containing subterranean coal formation having a low permeability to methane and penetrated by at least one injection well and at least one production well, the method consisting essentially of a) injecting an aqueous oxidant solution into the coal formation through the injection well;
b) maintaining the aqueous oxidant solution in the coal formation for a selected time to stimulate the formation of cleats in the coal formation;
c) removing sufficient water from the coal formation to open passage-ways in the cleats so tnat methane can be produced through the passage-ways; and d) producing methane from the coal formation through the production well at an increased rate.
According to a further aspect of the invention, there is provided a method of increasing the production of methane from a water-containing subterranean coal formation penetrated by at least one injection well and at least one production well, the method comprising:
a) injecting an aqueous oxidant solution into the coal formation through the injection well until water is recovered from the production well at an increased rate; and b) producing methane from the coal formation through the production well at an increased rate.
The aqueous oxidant solution may comprise hydrogen peroxide, ozone, oxygen and combinations thereof.
Brief Description of the Drawings Fig. 1 is a schematic diagram of a well penetrating a subterranean coal formation from the surface.
Fig. 2 is a schematic diagram of a well penetrating a subterranean coal formation from the surface wherein the coal formation has been fractured.
- 3a -x.96369 Fig. 3 is a schematic diagram of an injection well and a production well penetrating a subterranean coal formation from the surface.
Fig. 4 is a schematic diagram of an injection well and a production well penetrating a subterranean coal formation from the surface wherein the coal formation has been fractured from the injection well.
Fig. 5 is a schematic layout of a 5-spot injection and production well pattern.
Description of Preferred Embodiments In the discussion of the Figures, the same numbers will be used throughout to refer to the same or similar components.
In Fig. 1, a coal formation 10 penetrated from a surface 12 by a wellbore 14 is shown. The wellbore 14 includes a casing 16 positioned in the wellbore 14 by cement 18. Alternatively, the casing 16 could extend into or through the coal formation 10 with perforations through the casing in the coal seam providing fluid communication with the coal formation from the casing 16. The wellbore 14 extends into the coal formation 10 and includes a tubing 20 and a packer 22. The packer 22 is positioned to prevent flow between the outer diameter of the tubing 20 and the inner diameter of the casing 16. The wellbore 14 also includes equipment 24 adapted to inject a gaseous or liquid stream into the coal formation 10 or to recover a gaseous or liquid stream from the coal formation 10.
In the practice of the present invention, an aqueous oxidant solution is injected as shown by an arrow 26 through the tubing 20 into the coal formation 10 as shown by arrows 28. The zones treated are shown by circles 30. The aqueous oxidant solution is injected into the coal formation 10 for a selected time to enhance or stimulate the formation of a cleat system in the coal formation 10. The aqueous oxidant solution is injected for a period of time and in a quantity considered sufficient to increase the permeability of the coal formation 10 in the zones 30.
After a selected period or after a selected amount of the aqueous oxidant solution has been injected, the well is shut in for a period of time which may be greater than 24 hours. Typically, the well is shut in until the pressure in the wellbore returns to the formation pressure and thereafter for a t least 12 additional hours. The shut-in period allows for migration of the oxidant-containing solution into the coal formation 10 to oxidize components of the coal formation 10 to enhance the cleat system in the coal formation 10. Subsequent to the shut-in period, water is recovered from the coal formation 10 with methane to de-water the coal formation in the zones 30.
The term "de-water" as used herein does not refer to the complete removal of water from the coal formation 10, but rather to the removal of sufficient water from the coal formation 10 to open passage-ways in the cleat system in coal formation 10 so that methane can be produced through the passage-ways from the coal formation 10.
The aqueous solution may contain an oxidant selected from the group of hydrogen peroxide, ozone, oxygen and combinations thereof. Typically, the oxidant is used in concentrations equal to less than 10 volume percent of the aqueous oxidant solution. When hydrogen peroxide is used, the concentrations are desirably up to about 10 volume percent of the solution with concentrations from 5 to 10 percent being preferred. When hypochlorite is used, concentrations up to 5.0 volume percent are used.
In the embodiment shown in Fig. l, a single well is used for injection of the aqueous oxidant solution to chemically enhance or stimulate the n formation of a cleat system in the zones 30 to result in the release of formation water and an increase in the methane production rate from the coal formation 10.
In Fig. 2, a similar embodiment is shown except that the coal formation 10 has been fractured by fractures 32. The operation of the well is basically the same as rthat shown in Fig. 1 except that the coal formation has previously been fractured or is fractured by a fluid which may comprise the aqueous oxidant solution during at least part of the fracturing operation. For instance, it may be desirable to use a conventional 10 fracturing application, if the coal formation 10 is sufficiently impermeable,, as an initial stimulation method followed by the aqueous oxidant solution as a post-fracturing flush. The post-fracturing flush enhances cleat permeability throughout the areas contacting the fracture. In such instances, the well is desirably~shut-in as discussed previously and the oxidants are selected from the same oxidant materials group discussed previously. The fractures are formed in the coal formation 10 prior to injection of the oxidant solution. The oxidant solution could comprise the fracturing fluid if desired.
In Fig. 3, an injection well 34 and a production well 36 penetrate the coal formation 10 from the surface 12. The injection well 34 is spaced apart from the production well 36 at a spacing based upon the characteristics of the particular coal formation. and the like. According to the present invention, the aqueous oxidant solution described above is injected into the coal formation 10 through the injection well 34 as shown by the arrow 26 and the arrows 28 to treat the zones 30 which may extend from the injection well 34 in a generally circumferential direction, but generally extend preferentially toward a nearby production well or production wells.
-G-z~~s3s9 The production well 36 is positioned to withdraw water and methane from the coal formation 10. The production of water and methane through the production well 36 causes the aqueous oxidant solution to migrate toward the production well 36. Desirably, injection of the aqueous oxidant solution is continued until an increased water volume is detected in the production well 36 or until detection of an injection "tag" substance indicating the presence of a quantity of the aqueous oxidant solution is detected in the production well 36. The increase in the quantity of water produced from the production well 36 is indicative of the formation or enhancement of cleats in the coal formation 10 with a resulting increase in permeability so that additional quantities of water are released from the coal formation 10 for production as shown by arrows 38 through the production well 36 and a line 40. The arrows 38 are shown directed toward the production well 36 from both directions in contemplation that water will continue to be recovered at a lower rate from untreated portions of the coal formation 10.
The embodiment shown in Fig. 4 is similar to that shown in Fig. 3 except that the coal formation 10 has been fractured by fractures 32.
Fractures 32 in the embodiment shown in Fig. 2 can be of substantially any extent. By contrast, in the embodiment shown in. Fig. 4, the fractures 32 desirably extend no more than half way to the production well 36. Clearly, if the fractures 32 extend completely into the production well 36, it will be difficult to use any kind of fluid or gas drive between the injection well 34 and the production well 36. Desirably, the fractures extend no more than half the distance between the injection well 34 and the production well 36.
The use of the aqueous oxidant solution with the fractures 32 is as discussed previously.
?1.9f~~b9 The aqueous oxidant solution comprises a solution of hydrogen peroxide (H202), ozone (03) solutions, or oxygen (02) saturated water. Of these materials, solutions of peroxide and ozone are preferred because they are more readily generated in the relatively high volumes required in the field. Of these, hydrogen peroxide and ozone are preferred because they introduce only hydrogen and oxygen components into the' coal formation 10. Concentrations of hydrogen peroxide and ozone up to about 10 volume percent are suitable, although solutions containing less than about 5.0 volume percent are preferred.
In Fig. 5, a 5-spot well arrangement is shown.
Such well arrangements are useful in the practice of the present invention and may be used in a recurring pattern over a wide area. Such arrangements are well known to those skilled in the art and will be discussed only briefly. In the arrangement shown in Fig. 5, the aqueous oxidant solution is injected through the injection well 34 to treat the zones 30 to enhance the recovery of water and methane from the production wells 36. When break-through of the aqueous oxidant solution occurs, as evidenced by the production of water and methane at an increased rate from the production wells 36, the injection of the aqueous oxidant solution is stopped and the injection well 34 can be converted to a production well. The area would then be de-watered through the original production wells and the converted injection well. The areas of enhanced cleat formation will accelerate the de-watering process.
g _ r 219f 369 and increase the methane production rates and the ultimate methane recovery.
The method of the present invention is also useful as a pre-treatment for gas injection treatments to enhance the recovery of methane from the coal formation 10. The use of carbon dioxide, either alone or with other gases, to increase the production of methane from coal formations is well known. Similarly, the use of inert gases, such as nitrogen, argon and the like, to remove additional quantities of methane from coal formations by increasing the pressure in the formation and thereby removing additional methane as the methane partial pressure in the atmosphere in the coal seam is decreased are well known to those skilled in the art. The use of such processes requires that the formation be permeable to gas flow into or through the formation so that the methane can be recovered. The method of the present invention enhances the permeability of coal formations and may be used prior to the use of gas sweep or gas desorption treatments to enhance the recovery of methane.
Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments discussed are illustrative rather than limiting ~n nature and that many variations and modifications are possible within the scope of the present invention. Many such variations and modifications may be considered obvious and desirable by those skilled in the art. based upon a review of the foregoing description of preferred embodiments.
_9_
b) maintaining the aqueous oxidant solution in the coal formation for a selected time to enhance or stimulate the formation of cleats in the coal formation;
c) removing sufficient water from the coal formation to open passage-ways in the cleats so that methane can be produced through the passage-ways; and d) producing methane from the coal formation at an increased rate.
According to another aspect of the invention, there is provided a method of increasing the permeability to methane of a water-containing subterranean coal formation having a low permeability to methane and penetrated by at least one injection well and at least one production well, the method consisting essentially of a) injecting an aqueous oxidant solution into the coal formation through the injection well;
b) maintaining the aqueous oxidant solution in the coal formation for a selected time to stimulate the formation of cleats in the coal formation;
c) removing sufficient water from the coal formation to open passage-ways in the cleats so tnat methane can be produced through the passage-ways; and d) producing methane from the coal formation through the production well at an increased rate.
According to a further aspect of the invention, there is provided a method of increasing the production of methane from a water-containing subterranean coal formation penetrated by at least one injection well and at least one production well, the method comprising:
a) injecting an aqueous oxidant solution into the coal formation through the injection well until water is recovered from the production well at an increased rate; and b) producing methane from the coal formation through the production well at an increased rate.
The aqueous oxidant solution may comprise hydrogen peroxide, ozone, oxygen and combinations thereof.
Brief Description of the Drawings Fig. 1 is a schematic diagram of a well penetrating a subterranean coal formation from the surface.
Fig. 2 is a schematic diagram of a well penetrating a subterranean coal formation from the surface wherein the coal formation has been fractured.
- 3a -x.96369 Fig. 3 is a schematic diagram of an injection well and a production well penetrating a subterranean coal formation from the surface.
Fig. 4 is a schematic diagram of an injection well and a production well penetrating a subterranean coal formation from the surface wherein the coal formation has been fractured from the injection well.
Fig. 5 is a schematic layout of a 5-spot injection and production well pattern.
Description of Preferred Embodiments In the discussion of the Figures, the same numbers will be used throughout to refer to the same or similar components.
In Fig. 1, a coal formation 10 penetrated from a surface 12 by a wellbore 14 is shown. The wellbore 14 includes a casing 16 positioned in the wellbore 14 by cement 18. Alternatively, the casing 16 could extend into or through the coal formation 10 with perforations through the casing in the coal seam providing fluid communication with the coal formation from the casing 16. The wellbore 14 extends into the coal formation 10 and includes a tubing 20 and a packer 22. The packer 22 is positioned to prevent flow between the outer diameter of the tubing 20 and the inner diameter of the casing 16. The wellbore 14 also includes equipment 24 adapted to inject a gaseous or liquid stream into the coal formation 10 or to recover a gaseous or liquid stream from the coal formation 10.
In the practice of the present invention, an aqueous oxidant solution is injected as shown by an arrow 26 through the tubing 20 into the coal formation 10 as shown by arrows 28. The zones treated are shown by circles 30. The aqueous oxidant solution is injected into the coal formation 10 for a selected time to enhance or stimulate the formation of a cleat system in the coal formation 10. The aqueous oxidant solution is injected for a period of time and in a quantity considered sufficient to increase the permeability of the coal formation 10 in the zones 30.
After a selected period or after a selected amount of the aqueous oxidant solution has been injected, the well is shut in for a period of time which may be greater than 24 hours. Typically, the well is shut in until the pressure in the wellbore returns to the formation pressure and thereafter for a t least 12 additional hours. The shut-in period allows for migration of the oxidant-containing solution into the coal formation 10 to oxidize components of the coal formation 10 to enhance the cleat system in the coal formation 10. Subsequent to the shut-in period, water is recovered from the coal formation 10 with methane to de-water the coal formation in the zones 30.
The term "de-water" as used herein does not refer to the complete removal of water from the coal formation 10, but rather to the removal of sufficient water from the coal formation 10 to open passage-ways in the cleat system in coal formation 10 so that methane can be produced through the passage-ways from the coal formation 10.
The aqueous solution may contain an oxidant selected from the group of hydrogen peroxide, ozone, oxygen and combinations thereof. Typically, the oxidant is used in concentrations equal to less than 10 volume percent of the aqueous oxidant solution. When hydrogen peroxide is used, the concentrations are desirably up to about 10 volume percent of the solution with concentrations from 5 to 10 percent being preferred. When hypochlorite is used, concentrations up to 5.0 volume percent are used.
In the embodiment shown in Fig. l, a single well is used for injection of the aqueous oxidant solution to chemically enhance or stimulate the n formation of a cleat system in the zones 30 to result in the release of formation water and an increase in the methane production rate from the coal formation 10.
In Fig. 2, a similar embodiment is shown except that the coal formation 10 has been fractured by fractures 32. The operation of the well is basically the same as rthat shown in Fig. 1 except that the coal formation has previously been fractured or is fractured by a fluid which may comprise the aqueous oxidant solution during at least part of the fracturing operation. For instance, it may be desirable to use a conventional 10 fracturing application, if the coal formation 10 is sufficiently impermeable,, as an initial stimulation method followed by the aqueous oxidant solution as a post-fracturing flush. The post-fracturing flush enhances cleat permeability throughout the areas contacting the fracture. In such instances, the well is desirably~shut-in as discussed previously and the oxidants are selected from the same oxidant materials group discussed previously. The fractures are formed in the coal formation 10 prior to injection of the oxidant solution. The oxidant solution could comprise the fracturing fluid if desired.
In Fig. 3, an injection well 34 and a production well 36 penetrate the coal formation 10 from the surface 12. The injection well 34 is spaced apart from the production well 36 at a spacing based upon the characteristics of the particular coal formation. and the like. According to the present invention, the aqueous oxidant solution described above is injected into the coal formation 10 through the injection well 34 as shown by the arrow 26 and the arrows 28 to treat the zones 30 which may extend from the injection well 34 in a generally circumferential direction, but generally extend preferentially toward a nearby production well or production wells.
-G-z~~s3s9 The production well 36 is positioned to withdraw water and methane from the coal formation 10. The production of water and methane through the production well 36 causes the aqueous oxidant solution to migrate toward the production well 36. Desirably, injection of the aqueous oxidant solution is continued until an increased water volume is detected in the production well 36 or until detection of an injection "tag" substance indicating the presence of a quantity of the aqueous oxidant solution is detected in the production well 36. The increase in the quantity of water produced from the production well 36 is indicative of the formation or enhancement of cleats in the coal formation 10 with a resulting increase in permeability so that additional quantities of water are released from the coal formation 10 for production as shown by arrows 38 through the production well 36 and a line 40. The arrows 38 are shown directed toward the production well 36 from both directions in contemplation that water will continue to be recovered at a lower rate from untreated portions of the coal formation 10.
The embodiment shown in Fig. 4 is similar to that shown in Fig. 3 except that the coal formation 10 has been fractured by fractures 32.
Fractures 32 in the embodiment shown in Fig. 2 can be of substantially any extent. By contrast, in the embodiment shown in. Fig. 4, the fractures 32 desirably extend no more than half way to the production well 36. Clearly, if the fractures 32 extend completely into the production well 36, it will be difficult to use any kind of fluid or gas drive between the injection well 34 and the production well 36. Desirably, the fractures extend no more than half the distance between the injection well 34 and the production well 36.
The use of the aqueous oxidant solution with the fractures 32 is as discussed previously.
?1.9f~~b9 The aqueous oxidant solution comprises a solution of hydrogen peroxide (H202), ozone (03) solutions, or oxygen (02) saturated water. Of these materials, solutions of peroxide and ozone are preferred because they are more readily generated in the relatively high volumes required in the field. Of these, hydrogen peroxide and ozone are preferred because they introduce only hydrogen and oxygen components into the' coal formation 10. Concentrations of hydrogen peroxide and ozone up to about 10 volume percent are suitable, although solutions containing less than about 5.0 volume percent are preferred.
In Fig. 5, a 5-spot well arrangement is shown.
Such well arrangements are useful in the practice of the present invention and may be used in a recurring pattern over a wide area. Such arrangements are well known to those skilled in the art and will be discussed only briefly. In the arrangement shown in Fig. 5, the aqueous oxidant solution is injected through the injection well 34 to treat the zones 30 to enhance the recovery of water and methane from the production wells 36. When break-through of the aqueous oxidant solution occurs, as evidenced by the production of water and methane at an increased rate from the production wells 36, the injection of the aqueous oxidant solution is stopped and the injection well 34 can be converted to a production well. The area would then be de-watered through the original production wells and the converted injection well. The areas of enhanced cleat formation will accelerate the de-watering process.
g _ r 219f 369 and increase the methane production rates and the ultimate methane recovery.
The method of the present invention is also useful as a pre-treatment for gas injection treatments to enhance the recovery of methane from the coal formation 10. The use of carbon dioxide, either alone or with other gases, to increase the production of methane from coal formations is well known. Similarly, the use of inert gases, such as nitrogen, argon and the like, to remove additional quantities of methane from coal formations by increasing the pressure in the formation and thereby removing additional methane as the methane partial pressure in the atmosphere in the coal seam is decreased are well known to those skilled in the art. The use of such processes requires that the formation be permeable to gas flow into or through the formation so that the methane can be recovered. The method of the present invention enhances the permeability of coal formations and may be used prior to the use of gas sweep or gas desorption treatments to enhance the recovery of methane.
Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments discussed are illustrative rather than limiting ~n nature and that many variations and modifications are possible within the scope of the present invention. Many such variations and modifications may be considered obvious and desirable by those skilled in the art. based upon a review of the foregoing description of preferred embodiments.
_9_
Claims (13)
1. A method of enhancing the permeability to methane of a water-containing subterranean coal formation having a low permeability to methane and penetrated by at least one well, the method consisting essentially of a) injecting an aqueous oxidant solution into the coal formation;
b) maintaining the aqueous oxidant solution in the coal formation for a selected time to enhance or stimulate the formation of cleats in the coal formation;
c) removing sufficient water from the coal formation to open passage-ways in the cleats so that methane can be produced through the passage-ways; and d) producing methane from the coal formation at an increased rate.
b) maintaining the aqueous oxidant solution in the coal formation for a selected time to enhance or stimulate the formation of cleats in the coal formation;
c) removing sufficient water from the coal formation to open passage-ways in the cleats so that methane can be produced through the passage-ways; and d) producing methane from the coal formation at an increased rate.
2. A method as claimed in claim 1, wherein the aqueous oxidant solution is injected into the coal formation through a first well; the first well is shut in for a selected time; and thereafter, methane is produced from the first well at an increased rate.
3. A method as claimed in claim 1 or 2, wherein the coal formation has been fractured with fractures extending from the well prior to injection of the aqueous oxidant solution.
4. A method as claimed in any one of claims 1 to 3, wherein the aqueous oxidant solution comprises a fracturing fluid injected at fracturing conditions to fracture the coal formation.
5. A method as claimed in any one of claims 1 to 4, wherein said aqueous oxidant solution is maintained in the coal formation for at least 24 hours.
6. A method of increasing the permeability to methane of a water-containing subterranean coal formation having a low permeability to methane and penetrated by at least one injection well and at least one production well, the method consisting essentially of a) injecting an aqueous oxidant solution into the coal formation through the injection well;
b) maintaining the aqueous oxidant solution in the coal formation for a selected time to stimulate the formation of cleats in the coal formation;
c) removing sufficient water from the coal formation to open passage-ways in the cleats so that methane can be produced through the passage-ways; and d) producing methane from the coal formation through the production well at an increased rate.
b) maintaining the aqueous oxidant solution in the coal formation for a selected time to stimulate the formation of cleats in the coal formation;
c) removing sufficient water from the coal formation to open passage-ways in the cleats so that methane can be produced through the passage-ways; and d) producing methane from the coal formation through the production well at an increased rate.
7. A method as claimed in claim 6, wherein the aqueous oxidant solution is injected into the coal formation until water is recovered from the production well at an increased rate.
8. A method as claimed in claim 6 or 7, wherein the water removed in step (c) is recovered through the production well.
9. A method as claimed in any one of claims 1 to 8, wherein the aqueous oxidant solution comprises an aqueous solution of an oxidant selected from hydrogen peroxide, ozone, oxygen and combinations thereof.
10. A method as claimed in claim 9, wherein the oxidant is selected from hydrogen peroxide and ozone.
11. A method as claimed in any one of claims 1 to 10, wherein the aqueous oxidant solution contains up to about 10 volume percent of the oxidant.
12. A method as claimed in any one of claims 1 to 11, wherein the aqueous oxidant solution contains up to about 5 volume percent of the oxidant.
13. A method of increasing the production of methane from a water-containing subterranean coal formation penetrated by at least one injection well and at least one production well, the method comprising:
a) injecting an aqueous oxidant solution into the coal formation through the injection well until water is recovered from the production well at an increased rate; and b) producing methane from the coal formation through the production well at an increased rate.
a) injecting an aqueous oxidant solution into the coal formation through the injection well until water is recovered from the production well at an increased rate; and b) producing methane from the coal formation through the production well at an increased rate.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US08/594,725 | 1996-01-31 | ||
US08/594,725 US5669444A (en) | 1996-01-31 | 1996-01-31 | Chemically induced stimulation of coal cleat formation |
Publications (2)
Publication Number | Publication Date |
---|---|
CA2196369A1 CA2196369A1 (en) | 1997-08-01 |
CA2196369C true CA2196369C (en) | 2002-07-23 |
Family
ID=24380122
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA002196369A Expired - Fee Related CA2196369C (en) | 1996-01-31 | 1997-01-30 | Chemically induced stimulation of coal cleat formation |
Country Status (11)
Country | Link |
---|---|
US (1) | US5669444A (en) |
CN (1) | CN1082605C (en) |
AU (1) | AU1241297A (en) |
CA (1) | CA2196369C (en) |
DE (1) | DE19703448C2 (en) |
EA (1) | EA000054B1 (en) |
GB (1) | GB2309719B (en) |
IN (1) | IN191373B (en) |
PL (1) | PL185041B1 (en) |
UA (1) | UA45348C2 (en) |
ZA (1) | ZA97789B (en) |
Families Citing this family (39)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5964290A (en) * | 1996-01-31 | 1999-10-12 | Vastar Resources, Inc. | Chemically induced stimulation of cleat formation in a subterranean coal formation |
US5865248A (en) * | 1996-01-31 | 1999-02-02 | Vastar Resources, Inc. | Chemically induced permeability enhancement of subterranean coal formation |
US5967233A (en) * | 1996-01-31 | 1999-10-19 | Vastar Resources, Inc. | Chemically induced stimulation of subterranean carbonaceous formations with aqueous oxidizing solutions |
US5944104A (en) * | 1996-01-31 | 1999-08-31 | Vastar Resources, Inc. | Chemically induced stimulation of subterranean carbonaceous formations with gaseous oxidants |
DE19842407B4 (en) * | 1997-09-22 | 2008-04-10 | Vastar Resources, Inc., Houston | Chemically induced pacing in a subterranean coal formation |
US6662870B1 (en) | 2001-01-30 | 2003-12-16 | Cdx Gas, L.L.C. | Method and system for accessing subterranean deposits from a limited surface area |
US7025154B2 (en) | 1998-11-20 | 2006-04-11 | Cdx Gas, Llc | Method and system for circulating fluid in a well system |
US8297377B2 (en) | 1998-11-20 | 2012-10-30 | Vitruvian Exploration, Llc | Method and system for accessing subterranean deposits from the surface and tools therefor |
US8376052B2 (en) | 1998-11-20 | 2013-02-19 | Vitruvian Exploration, Llc | Method and system for surface production of gas from a subterranean zone |
US6679322B1 (en) | 1998-11-20 | 2004-01-20 | Cdx Gas, Llc | Method and system for accessing subterranean deposits from the surface |
US6280000B1 (en) | 1998-11-20 | 2001-08-28 | Joseph A. Zupanick | Method for production of gas from a coal seam using intersecting well bores |
US6454000B1 (en) | 1999-11-19 | 2002-09-24 | Cdx Gas, Llc | Cavity well positioning system and method |
US6681855B2 (en) | 2001-10-19 | 2004-01-27 | Cdx Gas, L.L.C. | Method and system for management of by-products from subterranean zones |
US6425448B1 (en) | 2001-01-30 | 2002-07-30 | Cdx Gas, L.L.P. | Method and system for accessing subterranean zones from a limited surface area |
US6598686B1 (en) | 1998-11-20 | 2003-07-29 | Cdx Gas, Llc | Method and system for enhanced access to a subterranean zone |
US7048049B2 (en) | 2001-10-30 | 2006-05-23 | Cdx Gas, Llc | Slant entry well system and method |
US6708764B2 (en) | 2002-07-12 | 2004-03-23 | Cdx Gas, L.L.C. | Undulating well bore |
WO2001063090A2 (en) * | 2000-02-25 | 2001-08-30 | Sofitech N.V. | Foaming agents for use in coal seam reservoirs |
US6412556B1 (en) | 2000-08-03 | 2002-07-02 | Cdx Gas, Inc. | Cavity positioning tool and method |
US6591903B2 (en) | 2001-12-06 | 2003-07-15 | Eog Resources Inc. | Method of recovery of hydrocarbons from low pressure formations |
US6725922B2 (en) | 2002-07-12 | 2004-04-27 | Cdx Gas, Llc | Ramping well bores |
US8333245B2 (en) | 2002-09-17 | 2012-12-18 | Vitruvian Exploration, Llc | Accelerated production of gas from a subterranean zone |
CN100347402C (en) * | 2002-12-13 | 2007-11-07 | 石油大学(北京) | Thermal recovery method for coal seam gas |
CN100351491C (en) * | 2002-12-13 | 2007-11-28 | 石油大学(北京) | Thermal recovery method for coal seam gas |
US7051809B2 (en) * | 2003-09-05 | 2006-05-30 | Conocophillips Company | Burn assisted fracturing of underground coal bed |
US20050082058A1 (en) * | 2003-09-23 | 2005-04-21 | Bustin Robert M. | Method for enhancing methane production from coal seams |
US7185702B2 (en) * | 2005-02-25 | 2007-03-06 | Halliburton Energy Services, Inc. | Methods and compositions for the in-situ thermal stimulation of hydrocarbons using peroxide-generating compounds |
US7681639B2 (en) * | 2008-06-17 | 2010-03-23 | Innovative Drilling Technologies LLC | Process to increase the area of microbial stimulation in methane gas recovery in a multi seam coal bed/methane dewatering and depressurizing production system through the use of horizontal or multilateral wells |
JP2011529128A (en) * | 2008-07-28 | 2011-12-01 | フォーブス オイル アンド ガス プロプライエタリー リミテッド | Method for liquefying carbonaceous material into liquid hydrocarbon |
WO2010027455A1 (en) * | 2008-09-04 | 2010-03-11 | Ciris Energy, Inc. | Solubilization of algae and algal materials |
CN102741500A (en) * | 2009-12-15 | 2012-10-17 | 雪佛龙美国公司 | System, method and assembly for wellbore maintenance operations |
JP5841948B2 (en) | 2009-12-18 | 2016-01-13 | シリス エナジー,インコーポレイテッド | Process for producing methane and other useful products by biogasification of coal |
CN102162351A (en) * | 2011-03-15 | 2011-08-24 | 彭仁田 | Application of hydrogen peroxide to thickened oil dilution |
CN105422067B (en) * | 2015-12-29 | 2017-11-28 | 中国石油大学(华东) | The method of active water displacement exploiting coal bed methane |
CN107165613B (en) * | 2017-07-07 | 2023-03-14 | 新疆国利衡清洁能源科技有限公司 | Safety guarantee system for underground coal gasification mine type gasification furnace and implementation method |
CN107325851A (en) * | 2017-08-25 | 2017-11-07 | 太原理工大学 | A kind of method that biological methane yield is improved by raw material of liquefaction coal |
RU2689012C1 (en) * | 2018-02-19 | 2019-05-23 | Федеральное государственное бюджетное образовательное учреждение высшего образования "Кубанский государственный технологический университет" (ФГБОУ ВО "КубГТУ") | Gas production method of gas at hydrate deposits |
CN109779594A (en) * | 2019-01-31 | 2019-05-21 | 中国科学技术大学 | Fracturing technology, device for producing hydrogen |
CN114856499A (en) * | 2022-05-12 | 2022-08-05 | 重庆大学 | Method for improving yield of coal-bed gas well by generating carbon dioxide through in-situ oxidation |
Family Cites Families (23)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4032193A (en) * | 1974-03-28 | 1977-06-28 | Shell Oil Company | Coal disaggregation by basic aqueous solution for slurry recovery |
US4043395A (en) * | 1975-03-13 | 1977-08-23 | Continental Oil Company | Method for removing methane from coal |
NL7800005A (en) * | 1978-01-02 | 1979-07-04 | Stamicarbon | PROCEDURE FOR GETTING METHANE IN SITU FROM GREAT DEPTH CARBON LAYERS. |
US4440651A (en) * | 1980-09-08 | 1984-04-03 | Standard Oil Company | Use of peroxide in waterflood oil recovery |
US4424863A (en) * | 1981-10-06 | 1984-01-10 | Mobil Oil Corporation | Oil recovery by waterflooding |
US4537252A (en) * | 1982-04-23 | 1985-08-27 | Standard Oil Company (Indiana) | Method of underground conversion of coal |
US4662439A (en) * | 1984-01-20 | 1987-05-05 | Amoco Corporation | Method of underground conversion of coal |
US4747642A (en) * | 1985-02-14 | 1988-05-31 | Amoco Corporation | Control of subsidence during underground gasification of coal |
US4662443A (en) * | 1985-12-05 | 1987-05-05 | Amoco Corporation | Combination air-blown and oxygen-blown underground coal gasification process |
US4765407A (en) * | 1986-08-28 | 1988-08-23 | Amoco Corporation | Method of producing gas condensate and other reservoirs |
US4762543A (en) * | 1987-03-19 | 1988-08-09 | Amoco Corporation | Carbon dioxide recovery |
US4883122A (en) * | 1988-09-27 | 1989-11-28 | Amoco Corporation | Method of coalbed methane production |
US5014788A (en) * | 1990-04-20 | 1991-05-14 | Amoco Corporation | Method of increasing the permeability of a coal seam |
US5099921A (en) * | 1991-02-11 | 1992-03-31 | Amoco Corporation | Recovery of methane from solid carbonaceous subterranean formations |
US5332036A (en) * | 1992-05-15 | 1994-07-26 | The Boc Group, Inc. | Method of recovery of natural gases from underground coal formations |
GB9319696D0 (en) * | 1993-09-23 | 1993-11-10 | Petroleum Recovery Inst | Process of well stimulation by chemically removing pyrobitu-men from subterranean formation for oil fields |
US5416286A (en) * | 1993-10-19 | 1995-05-16 | Dixon, Jr.; Alfred R. | High amperage, high efficiency electrical slide switch assembly with plug and socket contacts |
US5388642A (en) * | 1993-11-03 | 1995-02-14 | Amoco Corporation | Coalbed methane recovery using membrane separation of oxygen from air |
US5388645A (en) * | 1993-11-03 | 1995-02-14 | Amoco Corporation | Method for producing methane-containing gaseous mixtures |
US5417286A (en) * | 1993-12-29 | 1995-05-23 | Amoco Corporation | Method for enhancing the recovery of methane from a solid carbonaceous subterranean formation |
US5419396A (en) * | 1993-12-29 | 1995-05-30 | Amoco Corporation | Method for stimulating a coal seam to enhance the recovery of methane from the coal seam |
US5439054A (en) * | 1994-04-01 | 1995-08-08 | Amoco Corporation | Method for treating a mixture of gaseous fluids within a solid carbonaceous subterranean formation |
US5501273A (en) * | 1994-10-04 | 1996-03-26 | Amoco Corporation | Method for determining the reservoir properties of a solid carbonaceous subterranean formation |
-
1996
- 1996-01-31 US US08/594,725 patent/US5669444A/en not_active Expired - Lifetime
-
1997
- 1997-01-29 GB GB9701833A patent/GB2309719B/en not_active Expired - Fee Related
- 1997-01-29 EA EA199700009A patent/EA000054B1/en not_active IP Right Cessation
- 1997-01-30 CN CN97102507A patent/CN1082605C/en not_active Expired - Fee Related
- 1997-01-30 IN IN177CA1997 patent/IN191373B/en unknown
- 1997-01-30 CA CA002196369A patent/CA2196369C/en not_active Expired - Fee Related
- 1997-01-30 UA UA97010369A patent/UA45348C2/en unknown
- 1997-01-30 ZA ZA97789A patent/ZA97789B/en unknown
- 1997-01-30 PL PL97318207A patent/PL185041B1/en not_active IP Right Cessation
- 1997-01-30 DE DE19703448A patent/DE19703448C2/en not_active Expired - Fee Related
- 1997-01-30 AU AU12412/97A patent/AU1241297A/en not_active Abandoned
Also Published As
Publication number | Publication date |
---|---|
US5669444A (en) | 1997-09-23 |
IN191373B (en) | 2003-11-29 |
DE19703448C2 (en) | 2000-02-17 |
GB2309719A (en) | 1997-08-06 |
CN1082605C (en) | 2002-04-10 |
PL185041B1 (en) | 2003-02-28 |
AU1241297A (en) | 1997-08-07 |
PL318207A1 (en) | 1997-08-04 |
DE19703448A1 (en) | 1997-08-07 |
ZA97789B (en) | 1998-07-30 |
CN1165236A (en) | 1997-11-19 |
EA199700009A1 (en) | 1997-09-30 |
GB2309719B (en) | 1999-07-21 |
CA2196369A1 (en) | 1997-08-01 |
EA000054B1 (en) | 1998-04-30 |
GB9701833D0 (en) | 1997-03-19 |
UA45348C2 (en) | 2002-04-15 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
CA2196369C (en) | Chemically induced stimulation of coal cleat formation | |
US5964290A (en) | Chemically induced stimulation of cleat formation in a subterranean coal formation | |
US5967233A (en) | Chemically induced stimulation of subterranean carbonaceous formations with aqueous oxidizing solutions | |
US7819191B2 (en) | Method of fracturing a coalbed gas reservoir | |
CA2038290C (en) | Method of increasing the rate of production of methane from a coal seam | |
US5944104A (en) | Chemically induced stimulation of subterranean carbonaceous formations with gaseous oxidants | |
CA2236243C (en) | Chemically induced permeability enhancement of subterranean coal formation | |
US4871022A (en) | Method for removing polymer plugging in well boreholes | |
US5199766A (en) | Cavity induced stimulation of coal degasification wells using solvents | |
US20050082058A1 (en) | Method for enhancing methane production from coal seams | |
US3841406A (en) | Single well oil recovery method using carbon dioxide | |
AU720919B2 (en) | Increasing the rate of production of methane from subterranean coal and carbonaceous formations | |
SU1500792A1 (en) | Method of degassing coal seam | |
RU2109790C1 (en) | Method of secondarily opening productive formation |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
EEER | Examination request | ||
MKLA | Lapsed |
Effective date: 20160201 |