US20070277984A1 - Methods, systems, and devices for extracting a gas from a subsurface stratum - Google Patents

Methods, systems, and devices for extracting a gas from a subsurface stratum Download PDF

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US20070277984A1
US20070277984A1 US11/446,901 US44690106A US2007277984A1 US 20070277984 A1 US20070277984 A1 US 20070277984A1 US 44690106 A US44690106 A US 44690106A US 2007277984 A1 US2007277984 A1 US 2007277984A1
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conduit
fluid
recited
housing
liquid
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US11/446,901
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Robert Nelson Farrara
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SUBGARD INTERNATIONAL Co
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SUBGARD INTERNATIONAL Co
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    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21BEARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/12Methods or apparatus for controlling the flow of the obtained fluid to or in wells
    • E21B43/121Lifting well fluids
    • E21B43/128Adaptation of pump systems with down-hole electric drives
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21BEARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00Survey of boreholes or wells
    • E21B47/008Monitoring of down-hole pump systems, e.g. for the detection of "pumped-off" conditions
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21BEARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00Survey of boreholes or wells
    • E21B47/04Measuring depth or liquid level

Abstract

A fluid flow control device having at least one bypass valve that is actuated in response to the movement of an annular body housed in the device. The annular body may be housed in a cylindrical housing and be a buoyant or non-buoyant body, such as a non-buoyant annular ring. The movement of the annular body in the cylindrical housing actuates the one or more bypass valves. Flow through the bypass valves returns the fluid to its source, for example, to an aquifer while maintaining a desired liquid level. The fluid flow control device can provide an effective means for regulating the elevation of subsurface fluids, for example, ground water, to enhance the efficiency of gas extraction from subsurface strata, for example, the extraction of methane from water and methane containing coal beds. Systems and methods of extracting gases from subsurface strata are also provided.

Description

    TECHNICAL FIELD
  • The present invention relates, generally, to methods, systems, and devices for extracting gas from a subsurface stratum containing a gas and a liquid, in particular, to extracting methane gas from coal beds containing water and methane gas.
  • BACKGROUND OF THE INVENTION
  • Subsurface coal beds may often contain natural gas, for example, in the form of methane (CH4). Typically, methane is produced during the natural conversion of organic material to coal. When the methane gas becomes trapped within a subsurface bed of coal, the trapped gas is commonly referred to as “coal bed methane.”
  • Just like any fossil fuel, the energy value of coal bed methane makes it desirable to extract the methane from the coal bed. (See Coal Bed Methane: Potential and Concerns, U.S. Geological Survey Fact Sheet FS 123-00, October 2000, incorporated by reference herein.) However, subsurface coal beds may also contain ground water, for example, ground water from naturally occurring aquifers. The presence of water in the methane containing coal bed makes it difficult to extract the methane in a cost effective fashion. Extracting methane from a water-containing coal bed typically requires pumping water from the subsurface coal bed to reduce the hydraulic pressure on the methane so the methane can escape from the coal bed. Since methane is less dense than air, once released, the methane will rise to the surface. However, controlling the extraction of water to optimize the extraction of methane is typically difficult. Aspects of the present invention address this difficulty by providing methods, systems, and devices to extract coal bed methane, for example, by controlling the extraction of water from the subsurface coal bed.
  • The prior art includes devices for controlling the water level in subsurface wells, for example, the devices disclosed in U.S. Pat. Nos. 4,028,011 and 4,173,255, both of Kramer. However, these devices and their methods of use are limited to the control of well water levels to prevent over-pumping of wells, for example, the over-pumping of low yield wells. These devices and methods typically cannot be applied to the extraction of, for example, coal bed methane. The experience of the present inventor with the devices similar to those disclosed in these patents for coal bed methane extraction have been less than desirable. For example, such devices may be prone to fouling by the fine coal particulate that typically is present in the water being pumped from coal beds. These and other disadvantages of the prior art are addressed by aspects of the present invention.
  • SUMMARY OF THE INVENTION
  • Aspects of the present invention provide means for extracting gas from subsurface strata containing gas and liquid, for example, for extracting coal bed methane. One aspect of the invention is a method of extracting a gas from a subsurface stratum containing the gas and a liquid, the method including providing a first conduit from a surface whereby the liquid produces a liquid level in the first conduit; inserting a pumping device into the first conduit, the pumping device having an inlet below the liquid level and an outlet; inserting a second conduit into the first conduit, the second conduit providing a fluid path from the outlet of the pump to the surface; pumping the liquid from the subsurface stratum to the surface through the second conduit; and maintaining the liquid level in the first conduit whereby at least some of the gas escapes from the subsurface stratum and passes through the first conduit to the surface. In one aspect, the gas comprises methane, the liquid comprises water, and the subsurface stratum comprises a coal bed.
  • Another aspect of the invention is a system for extracting a gas from a subsurface stratum containing the gas and a liquid, the system including a first conduit directed from a surface to the stratum whereby the liquid produces a liquid level in the first conduit; a pumping device positioned below the liquid level, the pumping device having an inlet below the liquid level and an outlet; a second conduit positioned inside the first conduit, the second conduit providing a fluid path from the outlet of the pumping device to the surface; means for maintaining the liquid level in the first conduit whereby at least some of the gas escapes from the subsurface stratum and passes through the first conduit to the surface while pumping the liquid from the subsurface stratum to the surface through the second conduit. In one aspect, the means for maintaining the liquid level in the first conduit comprises at least one valve adapted to divert liquid from the second conduct to the first conduit.
  • Another aspect of the invention is a system for extracting methane from a coal bed containing methane and water, the system including a first conduit directed from a surface to the coal bed whereby the water produces a water level in the first conduit; a pump positioned below the liquid level, the pump having an inlet below the water level and an outlet; a second conduit positioned inside the first conduit, the second conduit providing a fluid path from the outlet of the pump to the surface; and a flow diverting device having a housing, an inlet in fluid communication with the outlet of the pump, a first outlet in fluid communication with the second conduit, a second outlet in fluid communication with the first conduit, a body mounted for vertical displacement within the housing, and at least one valve adapted to control water flow through the second outlet; wherein the at least one valve is adapted to operate in response to the movement of the body to maintain the water level in the first conduit whereby at least some of the methane escapes from the coal bed and passes through the first conduit to the surface while pumping the water from the coal bed to the surface through the second conduit.
  • A still further aspect of the invention is a flow regulating device including a cylindrical housing having a first end and a second end, the cylindrical housing having at least one perforation; an inlet chamber mounted to the first end of the housing, the inlet chamber having an inlet adapted to receive a flow of fluid; a conduit passing from the first end of the housing to the second end of the housing, the conduit having an inlet adjacent the first end of the housing in fluid communication with the inlet chamber; at least one valve in the first end of the cylindrical housing, the at least one valve adapted to vary fluid communication between the inlet chamber and the cylindrical housing; an annular disk mounted for axial movement within the cylindrical housing; and means for actuating the at least one valve in response to the axial movement of the annular disk; wherein deflection of the annular disk causes the means for actuating to actuate the at least one valve and provide fluid communication between the inlet chamber and the cylindrical body wherein at least some of the fluid introduced to the inlet of the inlet chamber is allowed to flow into the cylindrical housing and out of the at least one perforations in the cylindrical housing. In one aspect, the annular disk comprises a non-buoyant annular disk.
  • A still further aspect of the invention is a method for regulating the flow of a fluid, the method including providing a flow regulating device having a cylindrical housing having a first end and a second end, the cylindrical housing having at least one perforation; an inlet chamber mounted to the first end of the housing, the inlet chamber having an inlet adapted to receive a flow of fluid; a conduit passing from the first end of the housing to the second end of the housing, the conduit having an inlet adjacent the first end of the housing in fluid communication with the inlet chamber; at least one valve in the first end of the cylindrical housing, the at least one valve adapted to vary fluid communication between the inlet chamber and the cylindrical housing; an annular body mounted for axial movement within the cylindrical housing, the annular body having an axial surface; and means for actuating the at least one valve in response to the movement of the annular body; mounting a fluid pumping device to the inlet of the inlet chamber; immersing the flow regulating device and the fluid pumping device in a fluid to provide a level of fluid above the annular body; providing a gas overpressure to the surface of the level of the fluid; pumping the fluid into the inlet chamber and through the conduit by means of the pumping device; and when the fluid level deceases wherein the axial surface of the annular disk is exposed to the gas overpressure, allowing the annular body to deflect under the force of the gas overpressure to actuate the means for actuating and open the at least one valve and permit fluid to flow from the inlet chamber to the cylindrical housing wherein the flow through the conduit is reduced. In one aspect, immersing the flow regulating device and the fluid pumping device in a fluid comprises immersing the flow regulating device and the fluid pumping device in a fluid containing subsurface stratum. In another aspect, the subsurface stratum further comprises methane gas, and wherein providing a gas overpressure to the surface of the level of the fluid comprises providing a methane gas overpressure from subsurface stratum.
  • These and other aspects, features, and advantages of this invention will become apparent from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings.
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention will be readily understood from the following detailed description of aspects of the invention taken in conjunction with the accompanying drawings in which:
  • FIG. 1 is schematic diagram of a system for extracting a gas from a subsurface stratum containing the gas and a liquid according to one aspect of the invention.
  • FIG. 2 is a perspective view of a flow-regulating device according to another aspect of the invention.
  • FIG. 3 is front elevation view, partially in cross section of the flow-regulating device shown in FIG. 2.
  • FIG. 4 is a perspective view of an annular disk used in the flow-regulating device shown in FIG. 3 according to one aspect of the invention.
  • FIG. 5 is a plan view of the annular disk shown in FIG. 4.
  • FIG. 6 is a side elevation view, partially in cross section, of the annular disk shown in FIG. 4.
  • FIG. 7 is a perspective view, similar to FIG. 2, of a flow-regulating device according to another aspect of the invention.
  • DETAILED DESCRIPTION OF THE INVENTION
  • FIG. 1 is schematic diagram of a system 10 for extracting a gas from a subsurface stratum 12 containing a gas and a liquid, for example, methane and water, according to one aspect of the invention. Subsurface stratum 12 may comprise any subsurface layer lying at a depth 13 below the surface 14 of the earth and containing a gas and a liquid and from which it is desirable to extract the gas with little or no liquid, for example, to isolate the gas from the liquid. The depth 13 typically may be at least about 3 feet, but may be as deep as about 1500 feet or more. The gas may be any naturally occurring or man-made gas and the liquid may be any liquid. In one aspect of the invention, the subsurface stratum 12 comprises a coal bed having a thickness 21, and the gas comprises methane and the liquid comprises substantially water, for example, naturally occurring groundwater. In one aspect, the systems and methods of the present invention are adapted to extract methane from a coal bed, for example, from fractures or “cleats” in the coal bed, while minimizing the extraction of water from the coal bed. The thickness 21 of stratum 12 may range from about 5 feet to about 100 feet or more.
  • As shown in FIG. 1, stratum 12 bearing the gas to be extracted may lie beneath one or more other strata 15, for example, one or more clay strata, one or more claystone strata, one or more shallow water sand strata, one or more carbonaceous shale strata among other typical subsurface strata.
  • According to one aspect, system 10 includes a first conduit 16 extending from surface 14 to stratum 12, or to just above stratum 12 in a hole 11. Conduit 16 may typically be a pipe, for example, a steel or cast iron pipe, having a nominal diameter of at least about 6 inches. The outside diameter of conduit 16 and the inside diameter of hole 11 into which conduit 16 is inserted may be sealed with an appropriate sealing compound 17, for example, cement, to minimize or prevent the leakage of gas or liquid. In one aspect of the invention, a subsurface cavity 19 may be provided in stratum 12 below the lower end of conduit 16 to, for example, provide a plenum into which liquid and gas from stratum 12 may collect. In another aspect, conduit 16 may be perforated at its lower end and extend at least partially into stratum 12 whereby the perforated lower end of conduit 16 may provide collection plenum 19.
  • According to aspects of the invention, conduit 16 extends into stratum 12 whereby the liquid in stratum 12 provides a liquid level 18 in conduit 16. A pumping device 20 is positioned below the liquid level 18 and a second conduit 22 and a flow control device 26 are inserted into first conduit 16. Second conduit 22 is positioned and adapted to receive the output flow from pumping device 20 and carry the output flow to the surface 14. Pumping device 20 may be positioned below the open lower end of conduit 16 and may be accompanied by a pump drive means 24, for example, an electric motor, adapted to drive pumping device 20. Electric power may be provided to pump drive means 24 by means of a wire or cable (not shown) extended into conduit 16. Pumping device 20 includes an inlet positioned below the liquid level 18 and an outlet in fluid communication with second conduit 22. Pumping device 20 may be any submersible pumping device capable of lifting liquid the desired height, for example, at least depth 13. In one aspect, pumping device 20 may be a Model 7S03-8 submersible pump provided by Grundfos Pumps Corporation U.S.A. of Olathe, Kans., or its equivalent. Motor 20 may be a submersible motor, for example, a 5 horsepower motor provided by Franklin Electric, or its equivalent.
  • As shown in FIG. 1, system 10 may also include a wellhead 30 having a liquid outlet 31 and a gas outlet 32. Wellhead 30 may be any conventional wellhead, for example, a wellhead typically used to extract subsurface fluids, such as methane gas.
  • According to aspects of the present invention, system 10 also includes a flow control device 26 for maintaining liquid level 18 in first conduit 16. In one aspect, the maintenance of liquid level 18 in first conduit 16 permits at least some of the gas from stratum 12 to escape, for example, to escape from stratum 12 into conduit 16 and then from the surface of liquid level 18 pass through first conduit 16 to the surface 14 (as indicated by arrows 28 in FIG. 1). According to aspects of the invention, while gas is allowed to rise to the surface 14, liquid is pumped from subsurface stratum 12 to surface the 14 through second conduit 22 as indicated by arrow 29.
  • Flow control device 26 may comprise at least one valve adapted to divert liquid from the second conduct to the first conduit. Flow control device 26 may also be a device adapted to monitor liquid level 18 and provide means for diverting at least some liquid pumped by pumping device 20 from second conduit 22 to first conduit 16 when liquid level 18 deviates from a desired level. In one aspect, flow control device 26 may comprise a device having means for detecting the elevation of liquid level 18 and then varying the operation of a valve to maintain or vary liquid level 18 as desired. The means for detecting the elevation of liquid level 18 may comprise means for detecting exposure of a surface to a gas, for example, exposure of a surface that may typically be submerged in the liquid prior to the level of the liquid falling below a predetermined elevation. The means for detecting the elevation of liquid level 18 may comprise a buoyant body at least partially immersed in the liquid in conduit 16. In one aspect, flow control device 26 may comprise a device having at least one buoyant body positioned in first conduit 16 below liquid level 18. For example, the flow control device may include means for diverting at least some liquid from second conduit 22 to first conduit 16 in response to a detection of a predetermined elevation of liquid level 18, for example, by actuating at least one valve in response to the movement of the buoyant body. Flow control device 26 may include a housing enclosing the buoyant body and the housing may be in fluid communication with first conduit 16
  • In one aspect of the invention, flow control device 26 may be the device disclosed in U.S. Pat. No. 4,173,255 entitled “Low Well Yield Control System and Method” (the disclosure of which is include herein in its entirety) and supplied by Subgard International of Cambridge, N.Y. under the trademark SUBGARD™. U.S. Pat. No. 4,173,255 discloses a submersible device having a buoyant body and a linkage that actuates one or more valves in response to the movement of the buoyant body. The method and device disclosed in the U.S. Pat. No. 4,173,255, as indicated by its title, are methods and devices to control or prevent the over pumping of wells. The disclosed device may be mounted to the outlet of a well pump and may be used to divert the pumped flow from the discharge conduit back into the well or aquifer when the level of the water in the well decreases below a predetermined level. The variation of the water level is detected by a buoyant body in the device. The movement of the buoyant body actuates one or more valves which divert flow to the aquifer. Though the device disclosed in U.S. Pat. No. 4,173,255 has been effectively used in the control of the operation of well water pumping, for example, in residential and commercial water wells, the applicant has discovered that the device has an advantageous application in the pumping and isolation of gases from subsurface strata containing gases and liquids, for example, in the handling of coal bed methane.
  • According to one aspect of the invention, the device disclosed in U.S. Pat. Nos. 4,028,011 or 4,173,255 (the disclosures of which are incorporated by reference herein) may be used for flow control device 26 by mounting the device to the outlet of pump 20 and to conduit 22. However, instead of regulating the flow of well water from an aquifer to minimize or prevent over pumping of the aquifer, the device disclosed in these patents may be used to maintain liquid level 18 in conduit 16 whereby gas in coal bed 12 may escape from, for example, cleats, and pass to surface 14 via conduit 16. In one aspect, the devices disclosed in U.S. Pat. Nos. 4,028,011 or 4,173,255 may maintain liquid level 18 in conduit 16 by diverting liquid flow from conduit 22 to conduit 16 whereby pumping device 20 can operate substantially continuously, for example, without undesirable cycling on and off.
  • FIG. 2 is a perspective view of a flow-regulating device 40 according to another aspect of the invention. In one aspect of the invention, device 40 may be used for flow control device 26 shown in FIG. 1. FIG. 3 is front elevation view, partially in cross section of flow-regulating device 40 shown in FIG. 2. As shown in FIGS. 2 and 3, flow-regulating device 40 includes a housing 42 having a first end 44 and a second end 46. Housing 42 is typically cylindrical, for example, circular cylindrical or rectangular cylindrical, though a circular cylindrical housing is shown in FIGS. 2 and 3. As shown, housing 42 includes a cylindrical side wall 43, an end plate 45 closing off the second end 46 and an inlet chamber 50 that effectively closes off the first end 44 of housing 42. Housing 42 may include at least one aperture or perforation 41 in sidewall 43, typically, a plurality of apertures 41 may be provided. Device 40 also includes at least one conduit 52 that extends from first end 44 to second end 46 of housing 42, and typically extends out from housing 52 to provide a conduit extension 53. Conduit 52 may be coaxial with cylindrical housing 42 wherein both the centerline of conduit 52 and the centerline of housing 42 lie on the same line 54. However, conduit 52 and housing 42 may also not be coaxial; that is, the centerline of conduit 52 may be offset from the centerline of housing 42. According to aspects of the invention, conduit 52 accesses inlet chamber 50 whereby a fluid, for example, water, may flow from inlet chamber 50 to conduit 52 and out of extension 53.
  • Inlet chamber 50 comprises a cavity into which a flow of fluid, for example, water is introduced. Inlet chamber 50 includes a sidewall housing 56 having a sidewall 58 and top plate 60. An inlet 62 is provided in housing 56. Inlet 62 may be adapted to receive a flow of fluid, for example, pressurized water, from a pumping device, for example, from pump 20 shown in FIG. 1. Inlet chamber 50 is in fluid communication with conduit 52, for example, conduit 52 may pass through an aperture in plate 60. Conduit 52 may be mounted to inlet chamber 50 by conventional means, for example, by means of welding or mechanical fasteners, or conduit 52 may be threaded into plate 60. According to aspects of the invention, inlet chamber 50 is also adapted to received one or more valve devices or mechanisms 64, for example, one or more devices adapted to regulate the flow of a liquid between inlet chamber 50 and cylindrical housing 42.
  • As shown in FIG. 3, device 40 also includes at least one annular body 66 that is mounted in an annular cavity 68 defined by the outside of conduit 52 and the inside of housing 42. Annular body 66 is mounted to freely translate in annular cavity 68. According to aspects of the invention, annular body 66 is operatively connected to a means 69 for actuating valve mechanism 64, for example, by means of a linkage set, for instance, one or more of the linkage sets disclosed in U.S. Pat. Nos. 4,028,011 or 4,173,255 (again, the disclosures of which are incorporated by reference herein). In one aspect, the axial movement of annular body 66 actuates means 69 and valve mechanism 64 whereby fluid is permitted to flow or prevented from flowing from inlet chamber 50 to housing 42. As will be discussed further below, in one aspect, annular body 66 may not be buoyant, but may be deflected by a fluid pressure exerted on the upper surface of annular body 66.
  • Annular body 66 may take many annular shapes and provide the desired function of regulating the operation of valve mechanism 64. For example, annular body 66 may comprise an annular disk as shown in FIG. 3, or an elongated cylinder. Annular body 66 may be solid or hollow. In one aspect of the invention, annular body 66 may be non-buoyant in the fluid in which annular body 66 is immersed; for example, annular body 66 may sink in water. However, in other aspects of the invention annular body 66 may be buoyant; for example, annular body 66 may float in water.
  • One annular body 70 that may be used in device 40 is illustrated in FIGS. 4-6. FIG. 4 is a perspective view of one annular disk 70. FIG. 5 is a plan view of disk 70 shown in FIG. 5 and FIG. 6 is a side elevation view, partially in cross section, of disk 70 shown in FIG. 5. As shown in FIG. 5, disk 70 may be circular and have an outside diameter 72 and an inside diameter 74. As shown in FIG. 6, disk 70 may have a width or thickness 76 and a radiused edge 78. In one aspect, disk 70 may have an outside diameter 72 of between about 2 to about 6 inches, for example, between about 3.75 inches and about 4.25 inches; an inside diameter 74 of between about 1 inches and about 4 inches, for example, between about 2 inches and about 3 inches; a thickness 76 of between about 0.125 inches and about 2 inches, for example, between about 0.25 inches and about 0.75 inches; and a radiused edges 78 having radius of between about 0.125 inches and about 6 inches, for example, between about 0.25 inches and about 1 inch.
  • Disk 70 may be metallic or non-metallic. For example, disk 70 may be made from one or more of the following metals: iron, steel, stainless steel, aluminum, titanium, nickel, magnesium, brass, bronze, or any other metal, or one or more of the following plastics: a polyamide (PA), for example, nylon; a polyamide-imide; a polyethylene (PE); a polypropylene (PP); a polyester (PE); a polytetraflouroethylene (PTFE); an acrylonitrile butadiene styrene (ABS); a polycarbonate (PC); or a vinyl, such as, polyvinylchloride (PVC), among other plastics. In one aspect, disk 70 may be made from a PVC plastic, for example, machined from bar stock. Disk 70 may also be made from wood
  • The diameter and length of device 40 may vary broadly depending upon the application in which device 40 is used. FIG. 7 is a perspective view similar to FIG. 2 of a flow-regulating device 140 according to another aspect of the invention. Device 140 includes many of aspects of device 40 discussed above, but is longer in length. For example, as indicated by the section lines in FIG. 7, device 140 may comprise a broad range of lengths, for example, a length ranging from about 2 feet to about 5 feet, or longer. Similar to device 40, device 140 may be used for flow control device 26 shown in FIG. 1. Also similar to device 40, device 140 may include a housing 142 having at least one aperture 141, an inlet chamber 150 having an inlet 162, at least one valve mechanism (not shown), and at least one conduit having an extension 153. Device 140 also includes an annular body (not shown), such as an annular body similar to annular disk 70 shown in FIGS. 4-6. Again, the structures of device 140 may perform essentially the same function and have essentially the same properties as the corresponding structures in device 40 discussed above.
  • The following description of the typical operation of devices 40, 140 is made with reference to the system shown in FIG. 1. As discussed above, in one aspect, device 40 or 140 may be used for device 26 in FIG. 1. The following discussion of the typical operation of device 40 assumes that device 40 is installed in the system shown in FIG. 1. As noted above, conduit 16 may be inserted into subsurface stratum 12 containing a liquid and at least some gas, for example, methane, whereby a level of liquid 18 is provided in conduit 16. Typically, the elevation of the level of liquid 18 will be defined by the elevation of the water table. However, in order to extract as much gas as possible, it is desirable to reduce the liquid level 18 as much as possible whereby the hydrostatic pressure in stratum 12 is reduced as much as possible whereby gas will be allowed to escape into conduit 16 and pass to surface 14. However, in one aspect of the invention, it is undesirable to expose the subsurface stratum 12, that is, to lower liquid level 18 into below upper edge 23 or the “seam” of stratum 12. For example, reducing liquid level 18 into stratum 12 can allow particles in stratum 12, for instance, flaky coal particles to escape into conduit 16 and, possibly, interfere with gas extraction. Thus, in one aspect, it is desirable to maintain liquid level 18 above the upper edge 23 of stratum 12.
  • In one aspect, liquid level 18 may be maintained as close to upper edge 23 as possible to minimize hydrostatic pressure on the stratum 12, for example, to minimize the hydrostatic pressure on gas-containing cleats in coal bed 12, while maintaining at least some liquid level of upper edge 23 to minimize the escape of particulate from stratum 12. Aspects of the present invention permit this desired control of liquid level 18 whereby gas extraction is maximized and particulate entrainment is minimized.
  • In one aspect of the invention, this desired control of liquid level 18 may be effected by a buoyant body in one of the devices disclosed in U.S. Pat. Nos. 4,028,011 or 4,173,255. In this aspect of the invention, the devices are positioned in conduit 16 whereby the movement of the buoyant body in these devices regulates the opening and closing of one or more bypass valves to maintain liquid level 18. In one aspect, these buoyant body devices may maintain liquid level 18 at a desired elevation while minimizing or preventing undesirable cycling of pumping device 20.
  • In another aspect of the invention, the desired control of liquid level 18 may be effected by an annular body, for example, annular disk 66, in devices 40 and 140. However, instead of relying on the buoyancy of a float or body, devices 40 and 140 are adapted to regulate the elevation of liquid level 18 in response to the exposure to gas pressure. According to one aspect of the invention, the inventor has found that actuation of bypass valves 64 in device 40, 140 may be effected by means of exposing a surface of a translatable body to the gas pressure present in conduit 16, for example, the pressure of methane gas escaping from a coal bed stratum 12, and employing the gas pressure to actuate one or more valves 46. For example, with reference to the aspect shown in FIG. 3, in one aspect, as the elevation of liquid level 18 in conduit 16 decreases and approaches the elevation of the upper surface of annular disk 66, the level of liquid above disk 66 decreases. According to aspect of the invention, when level 18 decreases whereby the upper surface of disk 66 is exposed to a gas, the pressure of the gas is sufficient to axially deflect disk 66 whereby one or more valves 64 may be actuated, for example, venting liquid from the outlet of pump 20 from inlet chamber 50 through one or more valves 64 into housing 42, through apertures 41 and into conduit 16. As the level of liquid 18 subsequently increases, the upper surface of annular disk 66 is again submerged preventing exposure to gas pressure and whereby valves 64 are closed. This actuation and deactivation of valves 64 may occur repeatedly as the level 18 is maintained at a desired level. In one aspect, the return or seating of valves 64 may be effected by one or more springs. However, in another aspect, the seating of valves 64 may be effected by the fluid pressure provided in chamber 50 by pumping device 20. Again, in one aspect, the activation and deactivation of valves 64 by device 40, 140 may maintain liquid level 18 at a desired elevation while minimizing or preventing undesirable cycling of pumping device 20.
  • While several aspects of the present invention have been described and depicted herein, alternative aspects may be effected by those skilled in the art to accomplish the same objectives. Accordingly, it is intended by the appended claims to cover all such alternative aspects as fall within the true spirit and scope of the invention.

Claims (29)

1. A method of extracting a gas from a subsurface stratum containing the gas and a liquid, the method comprising:
providing a first conduit from a surface whereby the liquid produces a liquid level in the first conduit;
inserting a pumping device into the first conduit, the pumping device having an inlet below the liquid level and an outlet;
inserting a second conduit into the first conduit, the second conduit providing a fluid path from the outlet of the pump to the surface;
pumping the liquid from the subsurface stratum to the surface through the second conduit; and
maintaining the liquid level in the first conduit whereby at least some of the gas escapes from the subsurface stratum and passes through the first conduit to the surface.
2. The method as recited in claim 1, wherein the gas comprises methane, the liquid comprises water, and the subsurface stratum comprises a coal bed.
3. The method as recited in claim 1, wherein maintaining the liquid level in the first conduit comprises diverting at least some liquid pumped by the pump from the second conduit to the first conduit.
4. The method as recited in claim 1, wherein maintaining the liquid level in the first conduit comprises monitoring the liquid level at a desired level and diverting at least some liquid pumped by the pump from the second conduit to the first conduit when the liquid level deviates from the desired level.
5. The method as recited in claim 1, wherein maintaining the liquid level comprises providing a body in the first conduit below the liquid level, and providing means to actuate at least one valve in response to the movement of the body.
6. The method as recited in claim 5, wherein the body comprises a buoyant body.
7. The method as recited in claim 5, wherein maintaining the liquid level further comprises providing the body in a housing, the housing being in fluid communication with the first conduit.
8. The method as recited in claim 1, wherein inserting a first conduit further comprises providing a sealing casing for the first conduit.
9. The method as recited in claim 1, wherein inserting a pumping device into the first conduit comprises inserting the pump at a position within the subsurface stratum
10. A system for extracting a gas from a subsurface stratum containing the gas and a liquid, the system comprising:
a first conduit directed from a surface to the stratum whereby the liquid produces a liquid level in the first conduit;
a pumping device positioned below the liquid level, the pumping device having an inlet below the liquid level and an outlet;
a second conduit positioned inside the first conduit, the second conduit providing a fluid path from the outlet of the pumping device to the surface;
means for maintaining the liquid level in the first conduit whereby at least some of the gas escapes from the subsurface stratum and passes through the first conduit to the surface while pumping the liquid from the subsurface stratum to the surface through the second conduit.
11. The system as recited in claim 10, wherein the means for maintaining the liquid level in the first conduit comprises at least one valve adapted to divert liquid from the second conduct to the first conduit.
12. The system as recited in claim 10, wherein the system further comprises a device adapted to monitor the liquid level and means for diverting at least some liquid pumped by the pump from the second conduit to the first conduit when the liquid level deviates from a desired level.
13. The system as recited in claim 12, wherein the device comprises a body positioned in the first conduit below the liquid level, and wherein the means for diverting the at least some liquid comprises means to actuate at least one valve in response to the movement of the body.
14. The system as recited in claim 13, wherein the body comprises a buoyant body.
15. The system as recited in claim 13, wherein the system further comprises a housing enclosing the body, the housing being in fluid communication with the first conduit.
16. A system for extracting methane from a coal bed containing methane and water, the system comprising:
a first conduit directed from a surface to the coal bed whereby the water produces a water level in the first conduit;
a pump positioned below the liquid level, the pump having an inlet below the water level and an outlet;
a second conduit positioned inside the first conduit, the second conduit providing a fluid path from the outlet of the pump to the surface; and
a flow diverting device having a housing, an inlet in fluid communication with the outlet of the pump, a first outlet in fluid communication with the second conduit, a second outlet in fluid communication with the first conduit, a body mounted for vertical displacement within the housing, and at least one valve adapted to control water flow through the second outlet;
wherein the at least one valve is adapted to operate in response to the movement of the body to maintain the water level in the first conduit whereby at least some of the methane escapes from the coal bed and passes through the first conduit to the surface while pumping the water from the coal bed to the surface through the second conduit.
17. The system as recited in claim 16, wherein the flow diverting device further comprises a set of linkages interconnecting the body and the at least one valve.
18. The system as recited in claim 16, wherein the system further comprises a wellhead.
19. The system as recited in claim 19, wherein the wellhead is adapted to isolate the methane from the water.
20. A flow regulating device comprising:
a cylindrical housing having a first end and a second end, the cylindrical housing having at least one perforation;
an inlet chamber mounted to the first end of the housing, the inlet chamber having an inlet adapted to receive a flow of fluid;
a conduit passing from the first end of the housing to the second end of the housing, the conduit having an inlet adjacent the first end of the housing in fluid communication with the inlet chamber;
at least one valve in the first end of the cylindrical housing, the at least one valve adapted to vary fluid communication between the inlet chamber and the cylindrical housing;
an annular disk mounted for axial movement within the cylindrical housing; and
means for actuating the at least one valve in response to the axial movement of the annular disk;
wherein deflection of the annular disk causes the means for actuating to actuate the at least one valve and provide fluid communication between the inlet chamber and the cylindrical body wherein at least some of the fluid introduced to the inlet of the inlet chamber is allowed to flow into the cylindrical housing and out of the at least one perforations in the cylindrical housing.
21. The device as recited in claim 20, wherein the annular disk comprises thickness of less then 3 inches.
22. The device as recited in claim 20, wherein the annular disk comprises a non-buoyant annular disk.
23. The device as recited in claim 22, wherein the non-buoyant annular disk comprises a solid annular disk.
24. The device as recited in claim 29, wherein the means for actuating the at least one valve comprises at set of linkages.
25. The device as recited in claim 20, wherein the at least one perforation in the cylindrical housing is positioned adjacent the first end of the cylindrical housing.
26. A method for regulating the flow of a fluid, the method comprising:
providing a flow regulating device comprising:
a cylindrical housing having a first end and a second end, the cylindrical housing having at least one perforation;
an inlet chamber mounted to the first end of the housing, the inlet chamber having an inlet adapted to receive a flow of fluid;
a conduit passing from the first end of the housing to the second end of the housing, the conduit having an inlet adjacent the first end of the housing in fluid communication with the inlet chamber;
at least one valve in the first end of the cylindrical housing, the at least one valve adapted to vary fluid communication between the inlet chamber and the cylindrical housing;
an annular body mounted for axial movement within the cylindrical housing, the annular body having an axial surface; and
means for actuating the at least one valve in response to the movement of the annular body;
mounting a fluid pumping device to the inlet of the inlet chamber;
immersing the flow regulating device and the fluid pumping device in a fluid to provide a level of fluid above the annular body;
providing a gas overpressure to the surface of the level of the fluid;
pumping the fluid into the inlet chamber and through the conduit by means of the pumping device; and
when the fluid level decreases wherein the axial surface of the annular disk is exposed to the gas overpressure, allowing the annular body to deflect under the force of the gas overpressure to actuate the means for actuating and open the at least one valve and permit fluid to flow from the inlet chamber to the cylindrical housing wherein the flow through the conduit is reduced.
27. The method as recited in claim 26, wherein immersing the flow regulating device and the fluid pumping device in a fluid comprises immersing the flow regulating device and the fluid pumping device in a fluid containing subsurface stratum.
28. The method as recited in claim 27, wherein the subsurface stratum further comprises methane gas, and wherein providing a gas overpressure to the surface of the level of the fluid comprises providing a methane gas overpressure from subsurface stratum.
29. The method as recited in claim 26, wherein the annular body comprises an annular disk.
US11/446,901 2006-06-05 2006-06-05 Methods, systems, and devices for extracting a gas from a subsurface stratum Abandoned US20070277984A1 (en)

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