SYSTEM AND METHOD FOR ENHANCING COAL BED METHANE RECOVERY
A system includes first and second wells. The first well has a first tube that extends from a first well head to a first end disposed within a coal seam. The second well is disposed at a distance from the first well and includes a second tube that extends from a second well head to a second end disposed within the coal seam. A pump is coupled to the first well and is configured to supply the first tube with pressurized fluid that includes nutrients for methanogenesis. At least a portion of the pressurized fluid introduced into the first tube of the first well is received within the second tube of the second well by way of the coal seam.
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This application claims priority to U.S. Provisional Patent Application Ser. No. 61/374,796, filed Aug. 18, 2010, the entirety of which is herein incorporated by reference.
FIELD OF DISCLOSUREThe disclosed systems and methods relate to the production of methane gas. More specifically, the disclosed systems and methods relate to the injection of nutrients, which may include metabolic amendments, and/or microorganisms for microbially-enhanced coal bed natural gas (e.g., methane or “coal bed methane”) recovery.
BACKGROUNDMany coal seams around the world either have produced or are capable of producing biogenic methane. Biogenic methane was created initially through a process known as a methanogenesis, which is a naturally occurring process that has been in existence for millions of years.
Recently, laboratory studies have duplicated the methanogenesis process and have created new biogenic gas in relatively short time periods, in some instances, as few as twenty (20) days. After completion of these laboratory studies, field pilot studies were initiated in an attempt to duplicate the findings in previous lab studies. Field pilot programs have replicated laboratory studies in that new biogenic methane was produced in several coal bed methane wells that prior to the study were completely void of gas. However, these field pilot programs have not resulted in a wide-distribution of the nutrients and/or microbes.
SUMMARYIn some embodiments, a system includes first and second wells. The first well has a first tube that extends from a first well head to a first end disposed within a coal seam. The second well is disposed at a distance from the first well and includes a second tube that extends from a second well head to a second end disposed within the coal seam. A pump is coupled to the first well and is configured to supply the first tube with pressurized fluid that includes nutrients for methanogenesis. At least a portion of the pressurized fluid introduced into the first tube of the first well is received within the second tube of the second well by way of the coal seam.
In some embodiments, a method includes injecting a fluid having a first nutrient concentration into a coal seam through a first well under a first pressure and extracting a second fluid having a second nutrient concentration from the coal seam through a second well disposed apart from the first well. The second nutrient concentration is less than a first nutrient concentration.
The disclosed systems and methods advantageously enable distribution of nutrients throughout a coal bed to provide a maximum exposure of the microorganisms to coal pore space and surface area of coal beds. The exposure of the microorganisms to the coal pore space and surface area is maximized by forcing nutrient rich water through the pore space itself thereby enabling the full potential of a methanogenesis process to convert the soluble or free carbon to methane. The system also advantageously establishes routes for the resultant methane to flow and be extracted.
For example, the system includes one or more pressurized pumps disposed adjacent to an injection well. The pumps inject nutrient-rich water into the injection well. The water is circulated through the coal bed by the injection pump and one or more circulation pumps disposed at a distance from the injection pump. The setup and operation of such systems may be performed in accordance with an improved method.
At block 106, an injection well is drilled in a site. The size and depth of the injection well may be based on the characteristics of the coal as determined at block 104.
Injection well 200 may be coupled to an injection pump 250 as illustrated in the embodiment shown in
A second well, which may be a recovery and/or circulation well, is drilled at a distance from the injection well at block 108. As will be understood by one skilled in the art, the distance at which the injection well is positioned from the test well may be based on the initial permeability assessment of the coal performed at block 104.
An example of such a recovery/circulation well 220 is illustrated in
In some embodiments, such as the embodiment illustrated in
The nutrient injection may be implemented by gravimetric and/or low pressure (e.g., approximately less than or equal to 50 psi). Injection system 280 may include a mixing system comprising one or more tanks used for mixing nutrients with other chemical amendments or with a tracer. The one or more mixing tanks are filled with water from well 222 and/or from make-up water from another formation water source. The nutrients and other chemical amendments or tracer is mixed in the one or more mixing tanks while being purged with an inert gas such as, for example nitrogen or argon. Mixing is conducted by impellers, pumps, gas diffusion, or any combination of methods as will be understood by one skilled in the art. The mixture from the mixing tanks are injected in-line with conduit 270 into well 202.
Both injection wells 200 and circulating wells 220 are capable of producing new biogenic gas generated from the circulation methodology. For example, each of the injection wells 200 and recovery/circulation wells 220 may be tied to a gathering system for transfer to a sales facility.
Referring again to
At block 112, the fluid 14 removed from the second well is analyze to determine the amount of tracer recovered such that the fluid connection between the injection well and the second well may be determined. For example, if fifty percent or more of the injected tracer is recovered from the second well, then it may be determined that a sufficient fluid connection between the injection well and the second well has been established. One skilled in the art will understand that other threshold values may be used other than fifty percent.
The rates at which the tracer fluid is pumped into the injection well and pumped out of the test well may be measured to provide a real-time measurement of the permeability of the coal seam at block 114. The real-time permeability measurement of the coal may be used to adjust the pumping parameters of the injection pump and the extraction pump.
At block 116, one or more additional wells may be drilled at distances from the injection well. As will be understood by one skilled in the art, the one or more additional wells may be drilled at distances based on the real-time permeability of the coal over an area in which the coal is to be used to produce methane. The one or more wells may include one or more injection wells 200 and/or one or more recovery/circulation wells 220. As described above, injection wells 200 may be coupled to a tank 260 or to an output of a recovery/circulation well 220 through a conduit 270 and pump 250.
One or more wells 200, 220 may be disposed in each of the subdivisions 302. For example, subdivisions 302-6, 302-7, 302-10, and 302-11 each include an injection well 200 associated with a corresponding injection pump 250. Each of the subdivisions 302 in which an injection pump 200 and injection well 250 are not disposed, i.e., subdivisions 302-1:302-5, 302-8, 302-9, and 302-12:302:16, may be configured with a respective recovery/circulation well 220 and corresponding pump 250.
In embodiments in which the well heads 202 of injection wells 200 are coupled to the well heads 222 of recovery/circulation wells 220, such as the embodiment illustrated in
One skilled in the art will understand that wells 200, 220, and pumps 250 may be configured in other patterns with respect to subdivisions. For example,
Referring again to
At block 120, a non-nutrient enriched fluid may be injected into the coal seam via the injection well(s) 200. For example, approximately 5,000 to 15,000 gallons of non-nutrient enriched fluid may be injected into the coal seam 14 through injection well(s) 200 in a 40 acre site. One skilled in the art will understand that other amounts of non-nutrient enhanced fluid may be injected based on the size of the coal seam, i.e., greater or less than the identified range. The non-nutrient enriched fluid flush pushes the initial nutrient-rich fluid out of the fractures in cleats and into the pore space of the coal.
At block 122, recovery/circulating wells 220 are turned to move the nutrients away from the injection wells 200 to spread the nutrients throughout the entire coal seam 14. In some embodiments, circulating pumps 220 are configured to move fluid in a range from 5 gallons per minute to 200 gallons per minute depending on the size of the site and the number of injection wells 200 and/or recovery/circulation wells 220 disposed in the site. One skilled in the art will understand that circulating pumps 220 may be configured to move fluid with other flow rates.
As described above, the nutrient-depleted fluid extracted from recovery/circulating wells 220 may pass through a nutrient injection system (280 in
Although the systems and methods have been described in terms of exemplary embodiments, they are not limited thereto. Rather, the appended claims should be construed broadly, to include other variants and embodiments of the systems and methods, which may be made by those skilled in the art without departing from the scope and range of equivalents of the systems and methods.
Claims
1. A system, comprising:
- a first well including a first tube that extends from a first well head to a first end disposed within a coal seam;
- a second well disposed at a distance from the first well, the second well including a second tube that extends from a second well head to a second end disposed within the coal seam; and
- a pump coupled to the first well and configured to supply the first tube with pressurized fluid that includes nutrients for methanogenesis,
- wherein at least a portion of the pressurized fluid introduced into the first tube of the first well is received within the second tube of the second well by way of the coal seam.
2. The system of claim 1, wherein the first well includes a nozzle disposed at the first end configured with a plurality of aperture for directing the pressurized fluid into the coal seam.
3. The system of claim 1, further comprising:
- a third well disposed at a distance from the first and second wells, the third well including a third tube that extends from a third well head to a third end disposed within the coal seam,
- wherein at least a portion of the pressurized fluid introduced into the first tube of the first well is received within the second tube of the second well by way of the coal seam.
4. The system of claim 1, further comprising:
- a third well disposed at a distance from the first and second wells, the third well including a third tube that extends from a third well head to a third end disposed within the coal seam; and
- a second pump coupled to the third well and configured to supply the third tube with pressurized fluid that includes nutrients for methanogenesis,
- wherein at least a portion of the pressurized fluid introduced into the first and second tubes of the first and second wells is received within the second tube of the second well by way of the coal seam.
5. The system of claim 1, wherein the fluid is provided to the pump from a tank.
6. The system of claim 1, wherein the first tube is connected to the second tube by a conduit that extends between the first well head and the second well head.
7. The system of claim 6, wherein the pump is disposed along the length of the conduit.
8. The system of claim 7, wherein a nutrient injection system is disposed along the length of the conduit.
9. A method, comprising:
- injecting a fluid having a first nutrient concentration into a coal seam through a first well under a first pressure; and
- extracting a second fluid having a second nutrient concentration from the coal seam through a second well disposed apart from the first well,
- wherein the second nutrient concentration is less than a first nutrient concentration.
10. The method of claim 9, further comprising:
- drilling a test well into the coal seam;
- assessing at least one characteristic of the coal seam using the test well;
- drilling the first well; and
- drilling the second well at a distance from the first well based on the at least one characteristic.
11. The method of claim 10, further comprising:
- injecting a tracer into the first well; and
- extracting at least a portion of the tracer from the second well.
12. The method of claim 11, further comprising obtaining a measurement of permeability of the coal seam based on a rate at which the tracer is injected to the first well and the portion of the tracer is extracted from the second well.
13. The method of claim 9, further comprising extracting a third fluid having a third nutrient concentration from the coal seam through a third well disposed apart from the first and second well.
14. The method of claim 13, wherein the second and third nutrient concentrations are less than the first nutrient concentration.
15. The method of claim 9, further comprising:
- increasing the second nutrient concentration of the second fluid to provide the first fluid having the first concentration at a nutrient injection system coupled to the second well; and
- supplying the first fluid to the first well by way of a conduit between the nutrient injection system and the first well.
16. The method of claim 9, further comprising:
- injecting a third fluid having a third nutrient concentration into the first well after the first fluid has been injected into the first well,
- wherein the third nutrient concentration is less than the first and second nutrient concentrations.
17. The method of claim 16, wherein the third fluid forces the first fluid into spaces of the coal seam and combined with the first fluid to create the second fluid having the second concentration.
18. The method of claim 9, wherein the nutrients are for producing methanogenesis.
19. The method of claim 9, wherein the first pressure is up to and including approximately 100 pounds per square inch.
Type: Application
Filed: Aug 12, 2011
Publication Date: Feb 23, 2012
Applicant: NEXT FUEL, INC. (Sheridan, WY)
Inventors: Song JIN (Fort Collins, CO), Robert H. CRAIG (Sheridan, WY)
Application Number: 13/208,400
International Classification: E21B 43/16 (20060101); E21B 43/00 (20060101);