Integrated process for coalbed methane production and carbon dioxide sequestration in coalbed geology

Abstract

The present application relates to coal bed gas technical field, disclose coal bed gas mining and carbon dioxide storage integration process in coal bed geology, including the following steps, S1 sets up multi-branch horizontal well and coal bed gas extraction well in coal bed, S2 opens the fracturing fluid storage tank to add water-based fracturing fluid to all injection pipes, carries out primary segmented fracturing to coal bed, the extraction unit extracts the coal bed gas in the extraction pipe to the coal bed gas storage tank, the methane obtained after separation by the separation unit enters the methane storage tank, S3 adds carbon dioxide mixed fluid to all injection pipes, S4 detects the methane concentration of the gas extracted by the extraction pipe, closes the discharge valve of the extraction pipe and the feed valve of the main injection well, closes the multi-branch horizontal well and the coal bed gas extraction well, the present application adopts the above steps, hydraulic fracturing and carbon dioxide mixed fluid can be alternately carried out, when the blockage appears in the mining and drainage process, water-based fracturing fluid is injected again to dredge, improve the carbon dioxide storage amount and the methane recovery rate.

Description

Technical Field

[0001] This invention relates to the field of coalbed methane technology, and in particular to an integrated process for coalbed methane extraction and carbon dioxide sequestration in coal seam geology. Background Technology

[0002] Coalbed methane (CBM) is a gaseous resource associated with and coexisting with coal. It refers to hydrocarbon gases stored in coal seams, primarily composed of methane. It is an unconventional natural gas, and its combustion produces almost no waste gas, making it an excellent fuel for industrial, chemical, power generation, and residential use. Although my country is rich in coal and CBM resources, some coalfields have experienced tectonic deformation due to intense tectonic activity. Severely tectonically damaged coal seams typically contain abundant CBM, but their low permeability and mechanical strength result in low CH4 recovery rates. Therefore, utilizing the preferential adsorption of CO2 by coal, CO2 injection can more effectively displace and replace CH4 in coal seams. CO2-ECBM technology provides an effective approach for the exploitation of CBM in deep, low-permeability coal reservoirs. However, based on the fluid characteristics of CO2 within a suitable storage depth range, the injected CO2 will undergo physical-chemical reactions with the coal, thereby altering the coal reservoir structure (mainly pores, fractures, and chemical structure). Changes in reservoir structure can affect the adsorption / desorption capacity of CH4 and CO2, thereby impacting subsequent CO2 sequestration and CH4 recovery. Therefore, improving CO2 sequestration and CH4 recovery in coal seams is a promising research area. Summary of the Invention

[0003] The purpose of this invention is to provide an integrated process for coalbed methane extraction and carbon dioxide sequestration in coal seam geology, thereby increasing the CO2 sequestration and CH4 recovery rate in coal seams.

[0004] To achieve the above objectives, this invention provides an integrated process for coalbed methane extraction and carbon dioxide sequestration in coal seam geology, comprising the following steps:

[0005] S1. Set up multi-branch horizontal wells in the coal seam. The main injection well of the multi-branch horizontal well is connected to several branch injection wells. The main injection well and one branch injection well are connected by an injection pipe. The multiple branch injection wells are connected by multiple independent injection pipes. A coalbed methane extraction well is set at the end of the branch injection well. An extraction pipe is set in the coalbed methane extraction well.

[0006] S2. Open the fracturing fluid storage tank and add water-based fracturing fluid to all injection pipes. The water-based fracturing fluid enters the coal seam through the fracturing holes of the branch injection wells to perform the initial staged fracturing of the coal seam. The extraction unit extracts the coalbed gas from the extraction pipe to the coalbed gas storage tank. The methane obtained after separation by the separation unit enters the methane storage tank.

[0007] S3. Open the mixed fluid storage tank and add carbon dioxide mixed fluid to all injection pipes. The extraction unit extracts the coalbed methane from the extraction pipes to the coalbed methane storage tank. The methane obtained after separation by the separation unit enters the methane storage tank.

[0008] S4. Detect the methane concentration of the gas extracted from the extraction pipe. When the methane concentration is below 0.5%, close the discharge valve of the extraction pipe and the feed valve of the main injection well, remove the injection pipe and extraction pipe, and seal the multi-branch horizontal well and coalbed methane extraction well.

[0009] Preferably, in S1, the sidewall of the coalbed methane extraction well is provided with several extraction holes, and the extraction holes are provided with a fine filter screen and a filter separation membrane from the outside to the inside, and the extraction pipe is provided with a filter separation membrane at the end.

[0010] Preferably, the filtration membrane is one or more of MOF membrane, carbon molecular sieve membrane, and zeolite molecular sieve membrane.

[0011] Preferably, in S1, the distance between the main injection well and the coalbed methane extraction well is greater than the length of the branch injection well.

[0012] Preferably, in S2, the water-based fracturing fluid includes one or more of active water fracturing fluid, water-gel fracturing fluid, and clean fracturing fluid.

[0013] Preferably, in S3, the inlet 1 of the mixed fluid storage tank is connected to the supercritical treatment unit, the supercritical treatment unit adds supercritical carbon dioxide to the mixed fluid storage tank, the inlet 2 of the mixed fluid storage tank is connected to the deionized water storage tank, and an inlet valve is provided between the outlet of the mixed fluid storage tank and the injection pipe.

[0014] Preferably, in S3, the carbon dioxide mixed fluid is supercritical carbon dioxide and deionized water mixed in a volume ratio of 8-15:1.

[0015] Preferably, in S3, the extraction pump of the extraction unit is connected to the extraction pipe, a discharge valve is provided between the extraction pump and the extraction pipe, and an extraction valve is provided between the extraction pump and the coalbed methane storage tank.

[0016] Preferably, in S3, the separator of the separation unit is connected to the coalbed methane storage tank through a separation feed valve, and a first discharge valve is provided between the separator and the methane storage tank.

[0017] Preferably, the clean fracturing fluid is composed of one or more of quaternary ammonium cationic surfactants and counterionic additives.

[0018] Therefore, the beneficial effects of the above steps in this invention are as follows:

[0019] 1. When using multi-branch horizontal wells for production and drainage, hydraulic fracturing and carbon dioxide mixed fluid can be used alternately. If blockage occurs during production and drainage, the corresponding branch injection well can be found and water-based fracturing fluid can be injected again to clear the blockage.

[0020] 2. Using a carbon dioxide mixed fluid, the carbon dioxide and deionized water mixture increases the adsorption lag of carbon dioxide after contacting the coal seam, which is beneficial for carbon dioxide sequestration.

[0021] 3. While extracting coalbed methane, methane and carbon dioxide are separated, saving working time.

[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the integrated process for coalbed methane extraction and carbon dioxide storage in coal seam geology according to the present invention;

[0024] Figure 2 yes Figure 1 Enlarged view of point A in the middle.

[0025] Figure Labels

[0026] 1. Multi-branch horizontal well; 11. Main injection well; 12. Branch injection well; 2. Coalbed methane extraction well; 21. Extraction pump; 22. Coalbed methane storage tank; 3. Supercritical treatment unit; 4. Mixed fluid storage tank; 5. Fracturing fluid storage tank; 6. Deionized water storage tank; 7. Separator; 8. Methane storage tank; 9. Extraction hole; 91. Fine filter screen; 92. Filter separation membrane. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] The present invention will be explained in more detail through the following embodiments. The purpose of disclosing the present invention is to protect all changes and modifications within the scope of the present invention. The present invention is not limited to the following embodiments.

[0029] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0030] Example 1

[0031] The integrated process for coalbed methane extraction and carbon dioxide sequestration in coal seam geology includes the following steps, such as... Figure 1 As shown,

[0032] S1. A multi-branch horizontal well 1 is installed in the coal seam, avoiding fractured strata during installation. The main injection well 11 of the multi-branch horizontal well 1 is connected to several branch injection wells 12. The main injection well 11 and one branch injection well 12 are connected by an injection pipe. The multiple branch injection wells 12 are connected by multiple independent injection pipes. A coalbed methane extraction well 2 is installed at the end of the branch injection wells 12. The coalbed methane extraction well 2 is equipped with an extraction pipe.

[0033] In S1, the distance between the main injection well 11 and the coalbed methane extraction well 2 is greater than the length of the branch injection well 12.

[0034] In S1, the sidewall of the coalbed methane extraction well 2 is equipped with several extraction holes 9, such as... Figure 2 As shown, the extraction hole 9 is equipped with a fine filter screen 91 and a filter separation membrane 92 arranged sequentially from the outside to the inside, and the extraction pipe is equipped with a filter separation membrane 92 at the end. During the process of coalbed methane and carbon dioxide mixed gas entering the coalbed methane extraction well 2, the fine filter screen 91 blocks the particulate coal powder moving with the mixed gas, and the filter separation membrane 92 performs preliminary separation of methane and other gases such as carbon dioxide in the mixed gas, preventing a large amount of carbon dioxide from entering the coalbed methane storage tank 22 with the coalbed methane.

[0035] S2. Open the fracturing fluid valve. Water-based fracturing fluid is added to all injection pipes from the fracturing fluid storage tank 5. The water-based fracturing fluid enters the coal seam through the fracturing holes of the branch injection well 12 to perform initial staged fracturing of the coal seam. After staged fracturing, coalbed methane in the coal seam is released from the fractures. Some of the released coalbed methane moves to the coalbed methane extraction well 2. The extraction unit extracts the coalbed methane from the extraction pipe to the coalbed methane storage tank 22. The methane obtained after separation by the separation unit enters the methane storage tank 8.

[0036] When using the multi-branch horizontal well 1 for production and drainage, the branch injection well 12 should be as perpendicular as possible to the natural fractures to connect more natural fractures and facilitate better coalbed methane production. The production and drainage intensity should not be too high in the early stages, as this can easily lead to wellbore collapse. After hydraulic fracturing is stopped, if blockage occurs during production and drainage, the corresponding branch injection well 12 can be located, and water-based fracturing fluid can be injected again to clear the blockage.

[0037] In S2, the water-based fracturing fluid includes one or more of the following: active water fracturing fluid, water-gel fracturing fluid, and clean fracturing fluid.

[0038] The clean fracturing fluid is composed of one or more of the following: quaternary ammonium salt cationic surfactant and counterionic additive, specifically N,N-long-chain alkyl-2-hydroxypropyl-N,N,N',N'-methyl dibromide or 14-3(OH)-14(2Cl) and sodium p-toluenesulfonate.

[0039] S3. Open the mixed fluid storage tank 4 and add carbon dioxide mixed fluid to all the injection pipes. The extraction unit extracts the coalbed methane from the extraction pipe to the coalbed methane storage tank 22. The methane obtained after separation by the separation unit enters the methane storage tank 8.

[0040] In S3, the inlet 1 of the mixed fluid storage tank 4 is connected to the supercritical treatment unit 3, and the supercritical treatment unit 3 adds supercritical carbon dioxide to the mixed fluid storage tank 4. The inlet 2 of the mixed fluid storage tank 4 is connected to the deionized water storage tank 6, and an inlet valve is provided between the outlet of the mixed fluid storage tank 4 and the injection pipe.

[0041] The filtration membrane 92 is one or more of MOF separation membrane, carbon molecular sieve separation membrane, and zeolite molecular sieve membrane.

[0042] In S3, the carbon dioxide mixture is a supercritical carbon dioxide and deionized water mixed at a volume ratio of 8-15:1. When this mixture comes into contact with the coal seam, the adsorption hysteresis of carbon dioxide increases, which is beneficial for carbon dioxide sequestration. While the carbon dioxide mixture reduces the microporosity of the coal sample, it also reacts with carbonate minerals to form silica precipitates, increasing the development of macropores and fractures and improving coal seam permeability.

[0043] In S3, the extraction pump 21 of the extraction unit is connected to the extraction pipe, and a discharge valve is provided between the extraction pump 21 and the extraction pipe. An extraction valve is provided between the extraction pump 21 and the coalbed methane storage tank 22. The extraction pump 21 extracts the gaseous alkanes in the extraction pipe into the coalbed methane storage tank 22. When the extraction pump 21 stops working, the extraction valve is closed.

[0044] In S3, the separator 7 of the separation unit is connected to the coalbed methane storage tank 22 via a separation feed valve, and a first discharge valve is provided between the separator 7 and the methane storage tank 8. The separator 7 is used to separate the methane from the other impurity gases in the extracted coalbed methane, and the obtained methane enters the methane storage tank 8.

[0045] S4. Detect the methane concentration of the gas extracted from the extraction pipe. When the methane concentration is below 0.5%, close the discharge valve of the extraction pipe and the feed valve of the main injection well 11, remove the injection pipe and extraction pipe, and seal the multi-branch horizontal well 1 and the coalbed methane extraction well 2.

[0046] Example 2

[0047] The integrated process for coalbed methane extraction and carbon dioxide storage in coal seam geology includes the following steps.

[0048] S1. A multi-branch horizontal well 1 is installed in the gas coal seam, avoiding fractured strata during installation. The main injection well 11 of the multi-branch horizontal well 1 is connected to several branch injection wells 12. The main injection well 11 and one branch injection well 12 are connected by an injection pipe. A coalbed methane extraction well 2 is installed at the end of the branch injection well 12. An extraction pipe is installed in the coalbed methane extraction well 2.

[0049] In S1, the distance between the main injection well 11 and the coalbed methane extraction well 2 is greater than the length of the branch injection well 12.

[0050] In S1, the sidewall of the coalbed methane extraction well 2 is provided with several extraction holes 9. The extraction holes 9 are provided with a fine filter screen 91 and a filter separation membrane 92 in sequence from the outside to the inside. The end of the extraction pipe is provided with a filter separation membrane 92, which is a MOF separation membrane.

[0051] S2. Open the fracturing fluid valve. The fracturing fluid storage tank 5 adds clean fracturing fluid to all the injection pipes. The clean fracturing fluid is composed of N,N-long-chain alkyl-2-hydroxypropyl-N,N,N',N'-methyl dibromide and sodium p-toluenesulfonate.

[0052] Clean fracturing fluid enters the coal seam through the fracturing holes of branch injection well 12 to perform initial staged fracturing of the coal seam. After staged fracturing, coalbed methane in the coal seam is released from the fractures. Some of the released coalbed methane moves to coalbed methane extraction well 2. The extraction unit extracts the coalbed methane from the extraction pipe to coalbed methane storage tank 22. The methane obtained after separation by the separation unit enters methane storage tank 8.

[0053] After hydraulic fracturing is stopped, if blockage occurs during the production and drainage process, the corresponding branch injection well 12 can be located and clean fracturing fluid can be injected again to clear the blockage.

[0054] S3. The mixed fluid storage tank 4 is opened, and carbon dioxide mixed fluid is added to all injection pipes. The extraction unit extracts the coalbed methane from the extraction pipes into the coalbed methane storage tank 22. The methane obtained after separation by the separation unit enters the methane storage tank 8. When a mixed fluid of supercritical carbon dioxide and deionized water comes into contact with the coal seam, the carbon dioxide desorption hysteresis increases, and the connectivity of pores and fractures is enhanced, which is beneficial for carbon dioxide sequestration. The carbon dioxide mixed fluid reduces the microporosity of the coal sample, but it reacts with carbonate minerals to generate silica precipitates, increasing the development of macropores and fractures.

[0055] In S3, the inlet 1 of the mixed fluid storage tank 4 is connected to the supercritical treatment unit 3, and the supercritical treatment unit 3 adds supercritical carbon dioxide to the mixed fluid storage tank 4. The inlet 2 of the mixed fluid storage tank 4 is connected to the deionized water storage tank 6, and an inlet valve is provided between the outlet of the mixed fluid storage tank 4 and the injection pipe.

[0056] In S3, the carbon dioxide mixed fluid is a mixture of supercritical carbon dioxide and deionized water in a volume ratio of 12:1.

[0057] In S3, the extraction pump 21 of the extraction unit is connected to the extraction pipe, and a discharge valve is provided between the extraction pump 21 and the extraction pipe. An extraction valve is provided between the extraction pump 21 and the coalbed methane storage tank 22.

[0058] In S3, the separator 7 of the separation unit is connected to the coalbed methane storage tank 22 via a separation feed valve, and a first discharge valve is provided between the separator 7 and the methane storage tank 8. The separator 7 separates the remaining impurity gases and methane in the coalbed methane storage tank 22, and the separated methane enters the methane storage tank 8.

[0059] S4. Detect the methane concentration of the gas extracted from the extraction pipe. When the methane concentration is below 0.5%, close the discharge valve of the extraction pipe and the feed valve of the main injection well 11, remove the injection pipe and extraction pipe, and seal the multi-branch horizontal well 1 and the coalbed methane extraction well 2.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An integrated process for coalbed methane extraction and carbon dioxide sequestration in coal seam geology, characterized by: Includes the following steps, S1. Set up multi-branch horizontal wells in the coal seam. The main injection well of the multi-branch horizontal well is connected to several branch injection wells. The main injection well and one branch injection well are connected by an injection pipe. The multiple branch injection wells are connected by multiple independent injection pipes. A coalbed methane extraction well is set at the end of the branch injection well. An extraction pipe is set in the coalbed methane extraction well. S2. Open the fracturing fluid storage tank and add water-based fracturing fluid to all injection pipes. The water-based fracturing fluid enters the coal seam through the fracturing holes of the branch injection wells to perform the initial staged fracturing of the coal seam. The extraction unit extracts the coalbed gas from the extraction pipe to the coalbed gas storage tank. The methane obtained after separation by the separation unit enters the methane storage tank. S3. Open the mixed fluid storage tank and add carbon dioxide mixed fluid to all injection pipes. The extraction unit extracts the coalbed methane from the extraction pipes to the coalbed methane storage tank. The methane obtained after separation by the separation unit enters the methane storage tank. In S3, the carbon dioxide mixed fluid is supercritical carbon dioxide and deionized water mixed in a volume ratio of 8-15:1; S4. Detect the methane concentration of the gas extracted from the extraction pipe. When the methane concentration is below 0.5%, close the discharge valve of the extraction pipe and the feed valve of the main injection well, remove the injection pipe and extraction pipe, and seal the multi-branch horizontal well and coalbed methane extraction well.

2. The integrated process for coalbed methane extraction and carbon dioxide sequestration in coal seam geology according to claim 1, characterized in that: In S1, the sidewall of the coalbed methane extraction well is provided with several extraction holes. From the outside to the inside, the extraction holes are provided with a fine filter screen and a filter separation membrane. The end of the extraction pipe is provided with a filter separation membrane.

3. The integrated process for coalbed methane extraction and carbon dioxide sequestration in coal seam geology according to claim 2, characterized in that: The filtration separation membrane is one or more of MOF separation membrane, carbon molecular sieve separation membrane, and zeolite molecular sieve membrane.

4. The integrated process for coalbed methane extraction and carbon dioxide sequestration in coal seam geology according to claim 1, characterized in that: In S1, the distance between the main injection well and the coalbed methane extraction well is greater than the length of the branch injection well.

5. The integrated process for coalbed methane extraction and carbon dioxide sequestration in coal seam geology according to claim 1, characterized in that: In S2, the water-based fracturing fluid includes one or more of the following: active water fracturing fluid, water-gel fracturing fluid, and clean fracturing fluid.

6. The integrated process for coalbed methane extraction and carbon dioxide sequestration in coal seam geology according to claim 1, characterized in that: In S3, the inlet 1 of the mixed fluid storage tank is connected to the supercritical treatment unit, which adds supercritical carbon dioxide to the mixed fluid storage tank. The inlet 2 of the mixed fluid storage tank is connected to the deionized water storage tank. A feed valve is provided between the outlet of the mixed fluid storage tank and the injection pipe.

7. The integrated process for coalbed methane extraction and carbon dioxide sequestration in coal seam geology according to claim 1, characterized in that: In S3, the extraction pump of the extraction unit is connected to the extraction pipe, a discharge valve is provided between the extraction pump and the extraction pipe, and an extraction valve is provided between the extraction pump and the coalbed methane storage tank.

8. The integrated process for coalbed methane extraction and carbon dioxide sequestration in coal seam geology according to claim 1, characterized in that: In S3, the separator of the separation unit is connected to the coalbed methane storage tank through a separation feed valve, and a first discharge valve is provided between the separator and the methane storage tank.

9. The integrated process for coalbed methane extraction and carbon dioxide sequestration in coal seam geology according to claim 5, characterized in that: Clean fracturing fluid is composed of one or more of quaternary ammonium salt cationic surfactants and counterionic additives.

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