CCUS-ECBM carbon dioxide displacement coalbed methane technical method and application

Abstract

The invention relates to the field of coal bed gas extraction, and discloses a CCUS-ECBM carbon dioxide displacement coal bed gas technical method and application. The CCUS-ECBM carbon dioxide displacement coal bed gas technical method comprises the steps that at least one second hoistway with a first diving section and a first extending section which are arranged at an angle is drilled from the earth surface to a coal bed; a first target area formed by the second hoistway in the coal seam is arranged among the plurality of first hoistways in the coal seam; installing an injection device on the ground surface; and carbon dioxide is injected into the second hoistway through the injection device, and the coal bed gas of the multiple first hoistways is displaced. The method is used for solving the problem that coal bed gas extraction efficiency is low, a first diving section and a first extending section of a second shaft are arranged at an angle, so that the contact area of the first extending section and a coal bed is increased, and the displacement effect of carbon dioxide on a plurality of first shafts is improved; and the first target area, formed in the coal seam, of the second hoistway is arranged among the multiple first hoistways, and displacement of the multiple first hoistways is achieved.

Description

Technical Field

[0001] The present application belongs to the field of coalbed methane extraction, and in particular, relates to a CCUS-ECBM carbon dioxide displacement coalbed methane technology method and application. Background Art

[0002] CCUS (Carbon Capture, Utilization and Storage) is the capture, utilization and storage of carbon dioxide; ECBM (Enhanced Coal Bed Methane Recovery) is to improve the recovery rate of coalbed methane. Coalbed methane, also known as coalbed methane, commonly known as gas, refers to hydrocarbon gas with methane as the main component in coal seams, mainly adsorbed on the surface of coal matrix particles, and partially free in coal pores or dissolved in coal seam water. Coalbed methane is mainly present in coal pores in an adsorbed state, accounting for up to 70%.

[0003] At present, there are two main ways to extract coalbed methane: underground gas extraction and ground drilling mining. Underground gas extraction: Drill holes into various gas accumulation areas in coal mining, connect the extraction pipes in the boreholes to the underground dedicated extraction pipeline trunk, and use the ground extraction pump station to pump the accumulated gas to the ground using the negative pressure system for processing or discharge into the total return air flow. Ground drilling mining: After drilling from the ground to the fracture zone above the mining layer, the coalbed methane in the coal seam and goaf is pumped to the ground for use through the extraction well. This method produces high methane concentration and is easy to use industrially, but it has certain requirements for the terrain and coal seam structure.

[0004] However, the current coalbed methane extraction method has low extraction efficiency for coalbed methane adsorbed in coal pores. Summary of the invention

[0005] The embodiment of the present application provides a CCUS-ECBM carbon dioxide displacement coalbed methane technical method and application, which can improve the extraction efficiency of coalbed methane.

[0006] On the one hand, an embodiment of the present application provides a CCUS-ECBM carbon dioxide displacement coalbed methane technical method, comprising: in a working area having multiple first shafts, drilling at least one second shaft having a first diving section and a first extension section arranged at an angle from the surface to the coal seam, so that a first target area formed by the second shaft in the coal seam is placed between the multiple first shafts in the coal seam; installing an injection device on the surface, connecting the injection device to the second shaft; turning on the injection device and the extraction device of the first shaft, injecting carbon dioxide into the second shaft through the injection device, and displacing the coalbed methane in the multiple first shafts.

[0007] On the other hand, an embodiment of the present application also provides an application of CCUS-ECBM carbon dioxide displacement of coalbed methane, including: an extraction shaft, an injection shaft, an extraction device and an injection device; the extraction shaft includes a plurality of first shafts arranged at intervals, the first shafts extending from the ground surface to the coal seam along their own extension direction; the injection shaft includes at least one second shaft, the second shaft extending from the ground surface to the coal seam along their own extension direction, the second shaft includes a first diving section and a first extension section arranged successively and connected along their own extension direction, the first diving section and the first extension section are arranged at an angle, the end of the first extension section away from the first diving section forms a first target area in the coal seam, and the first target area is placed between the plurality of first shafts in the coal seam and along the extension direction of the coal seam; the extraction device is connected to the first shaft; the injection device is connected to the second shaft, and the injection device is configured to inject carbon dioxide into the second shaft when the extraction device extracts the coalbed methane to displace the coalbed methane in the plurality of first shafts.

[0008] In some embodiments of the present application, the injection shaft further includes a casing, which extends from the ground surface to a side of the coal seam close to the ground surface, and the casing is placed in the second shaft and is connected to the injection device.

[0009] In some embodiments of the present application, along the thickness direction of the coal seam, the distance between the first target area and a side of the coal seam away from the ground surface is less than or equal to the distance between the first target area and a side of the coal seam close to the ground surface.

[0010] In some embodiments of the present application, the end of the first submerged section facing away from the ground surface is placed in the coal seam, and the first extension section is extended along the extension direction of the coal seam and is arranged between multiple first shafts.

[0011] In some embodiments of the present application, the end of the first shaft away from the ground surface forms a second target area in the coal seam, and along the extension direction of the coal seam, the first target area is placed between the second target areas of multiple first shafts.

[0012] In some embodiments of the present application, the first target area is equidistant from the second target areas of the plurality of first shafts.

[0013] In some embodiments of the present application, at least one of the first shafts includes a second diving section and a second extension section that are successively and connected along its own extension direction, the second diving section extends along the first direction, and the second extension section extends along the second direction to the coal seam, and the first direction intersects with the second direction.

[0014] In some embodiments of the present application, the first shaft includes a second submerged section extending from the ground surface to the coal seam along a first direction, and the second submerged section is arranged side by side with the first submerged section.

[0015] In some embodiments of the present application, the second shaft includes a fractured gap, and the fractured gap extends along the coal seam toward at least one of the first shafts.

[0016] In some embodiments of the present application, the carbon dioxide is in liquid state.

[0017] In some embodiments of the present application, the injection pressure range of the injection device is 10 MPa to 30 MPa.

[0018] The CCUS-ECBM carbon dioxide displacement coalbed methane technical method and application of the embodiment of the present application is to set the first diving section of the second shaft at an angle to the first extension section, thereby increasing the contact area between the first extension section and the coal seam, thereby increasing the diffusion area of ​​carbon dioxide in the coal seam, and improving the displacement effect of carbon dioxide on multiple first shafts; and placing the first target area formed by the second shaft in the coal seam between multiple first shafts to achieve displacement of multiple first shafts. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solution of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0020] Figure 1 A schematic diagram of the arrangement of a CCUS-ECBM carbon dioxide displacement coalbed methane application provided in some embodiments of the present application; Figure 2 for Figure 1 A schematic diagram of the arrangement from another perspective; Figure 3 Another schematic diagram of the layout of the application of CCUS-ECBM carbon dioxide displacement of coalbed methane provided in some embodiments of the present application; Figure 4 Another schematic diagram of the layout of the application of CCUS-ECBM carbon dioxide displacement of coalbed methane provided in some embodiments of the present application; Figure 5 Another schematic diagram of the layout of the application of CCUS-ECBM carbon dioxide displacement of coalbed methane provided in some embodiments of the present application; Figure 6 The figure is a flow chart of a CCUS-ECBM carbon dioxide displacement coalbed methane technology method.

[0021] Description of reference numerals: 1. Surface; 2. Coal seam; 21. First target area; 22. Roof; 23. Floor; 24. Second target area; 100. Extraction shaft; 101. First shaft; 110. Second submerged section; 111. Second extension section; 200. Injection shaft; 201. Second shaft; 210. First submerged section; 211. First extension section; 230. Fracturing gap; 300. Extraction device; 400. Injection device; X, first direction; Y, second direction. DETAILED DESCRIPTION

[0022] The features and exemplary embodiments of various aspects of the present application will be described in detail below. In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, rather than to limit the present application. For those skilled in the art, the present application can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present application by illustrating the examples of the present application.

[0023] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "include..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0024] With the rapid growth of global fossil fuel consumption, the concentration of carbon dioxide in the atmosphere continues to rise, leading to increasingly serious global climate change problems. In order to achieve the goal of greenhouse gas emission reduction, carbon dioxide is currently captured and stored through CCUS technology. CCUS, or carbon capture, utilization and storage, is one of the key technologies for addressing global climate change. It involves separating carbon dioxide from emission sources (such as the use of fossil energy in industries such as electricity, chemicals, steel, and cement), and then directly utilizing or storing it to achieve an industrial process of carbon dioxide emission reduction. The whole process can be divided into three main steps: Carbon capture: separation and enrichment of carbon dioxide produced during industrial production.

[0025] Transport: The captured CO2 is transported to a utilization or storage site.

[0026] Utilization and storage: Utilization methods include geological utilization, chemical utilization, biomass utilization, etc.; storage is the transportation of captured and compressed carbon dioxide through pipelines, tank trucks, etc., and finally injecting it into underground rock formations for storage.

[0027] CCUS technology is a new development trend of CCS (Carbon Capture and Storage) technology. Compared with CCS, CCUS can transform carbon dioxide into resources and generate economic benefits, so it is more practical.

[0028] ECBM, or enhanced coalbed methane recovery, is a method of injecting carbon dioxide (CO2) into coal seams, waste gas mines, saline water layers, etc., so that it competes with methane (CH4) in the coal seams for adsorption, thereby driving out methane. This method can not only improve the recovery rate of coalbed methane, but also seal carbon dioxide in coal seams, waste gas mines, etc., thereby helping to reduce the greenhouse effect.

[0029] When extracting coalbed methane, since the coalbed methane is adsorbed in the coal seam, the extraction device can only extract free coalbed methane, while the coalbed methane adsorbed in the cracks of the coal seam cannot be completely extracted. On the one hand, it affects the extraction efficiency, and on the other hand, the residual coalbed methane poses a safety hazard to the underground.

[0030] In view of this, the present application provides an application of CCUS-ECBM carbon dioxide to replace coalbed methane, by drilling at least one second wellbore to the coal seam, placing the second wellbore between multiple first wellbores in the first target area of ​​the coal seam, and injecting carbon dioxide into the second wellbore to displace the coalbed methane in the multiple first wellbores, thereby improving the extraction efficiency of the coalbed methane.

[0031] Figure 1 A schematic diagram of the arrangement of a CCUS-ECBM carbon dioxide displacement coalbed methane application provided in some embodiments of the present application; Figure 2 for Figure 1 Schematic diagram of the arrangement from another perspective.

[0032] like Figure 1 and Figure 2As shown, some embodiments of the present application provide an application of CCUS-ECBM carbon dioxide displacement of coalbed methane, including an extraction shaft 100, an injection shaft 200, an extraction device 300 and an injection device 400, the extraction shaft 100 includes a plurality of first shafts 101 arranged at intervals, the first shaft 101 penetrates from the ground surface 1 to the coal seam 2 along its own extension direction; the injection shaft 200 includes at least one second shaft 201, the second shaft 201 penetrates from the ground surface 1 to the coal seam 2 along its own extension direction, and the second shaft 201 includes first submerged sections 21 arranged successively and connected along its own extension direction. 0 and the first extension section 211, the first submerged section 210 is set at an angle to the first extension section 211, the end of the first extension section 211 away from the first submerged section 210 forms a first target area 21 in the coal seam 2, and the first target area 21 is placed between multiple first shafts 101 in the coal seam 2 and along the extension direction of the coal seam 2; the extraction device 300 is connected to the first shaft 101; the injection device 400 is connected to the second shaft 201, and the injection device 400 is configured to inject carbon dioxide into the second shaft 201 when the extraction device 300 extracts coalbed methane, so as to displace the coalbed methane in the multiple first shafts 101.

[0033] The extraction shaft 100 is a shaft used for extracting coalbed methane. The extraction shaft 100 may be an existing shaft or a newly drilled shaft. For example, the extraction shaft 100 may be a shaft used only for extracting coalbed methane, or a shaft used for burning coalbed methane to form synthesis gas after extracting coalbed methane, or a shaft used for extracting coalbed methane after burning to form synthesis gas.

[0034] The extraction well 100 includes a plurality of first wells 101. For example, the extraction well 100 includes two, three, four or five first wells 101. The well types of the plurality of first wells 101 may be the same or different. For example, the wellhead arrangement of the plurality of first wells 101 on the surface 1 may be in any spacing arrangement such as a straight line, a circle or a triangle.

[0035] For example, the first shaft 101 may extend to the coal seam 2 perpendicularly to the ground surface 1 or inclined to the ground surface 1. In one example, the first shaft 101 may extend to the coal seam 2 at an acute angle or an obtuse angle to the ground surface 1.

[0036] Exemplarily, the first hoistway 101 may have one section extending in one direction or may have a plurality of sections extending in a plurality of directions.

[0037] The extraction device 300 is a device for extracting and storing coalbed methane in the extraction shaft 100. Exemplarily, the extraction device 300 is installed on the ground surface 1 and is connected to one or more shafts. In one example, the extraction device 300 includes an extraction pump and a storage tank, and the extraction pump extracts the coalbed methane in the extraction shaft 100 and stores it in the storage tank.

[0038] The injection shaft 200 is a shaft for injecting carbon dioxide into the coal seam 2. The injection shaft 200 extends from the ground surface 1 to the coal seam 2.

[0039] The injection well 200 includes one or more second wells 201. In one example, in a working area, there are multiple first wells 101, and the coalbed methane in the multiple first wells 101 can be displaced by one or more second wells 201.

[0040] For example, the first submerged section 210 of the second shaft 201 may extend vertically or obliquely to the surface 1 toward the coal seam 2. The first submerged section 210 may extend to the coal seam 2 or be disposed between the coal seam 2 and the surface 1.

[0041] Exemplarily, the first extension section 211 of the second shaft 201 is arranged at an angle to the first submerged section 210. The first extension section 211 may extend from the end of the first submerged section 210 to the coal seam 2. The first extension section 211 may be partially or completely placed in the coal seam 2. The first extension section 211 is arranged at an angle or parallel to the coal seam 2, which may increase the length of the first extension section 211 in the coal seam 2, thereby increasing the permeability area of ​​carbon dioxide in the coal seam 2 and improving the displacement effect of carbon dioxide.

[0042] The end of the second shaft 201 forms a first target area 21 in the coal seam 2. For example, the concentration of carbon dioxide in the first target area 21 is greater than the concentration of carbon dioxide in other areas of the coal seam 2. The first target area 21 can be a circular area with the target point as the center, or a rectangular area with the target point as the center and a certain offset and along-line distance from the center of the target. In a highly deviated well or a horizontal well, the target area may be a cylindrical volume.

[0043] The coal seam 2 and the ground surface 1 are stacked in the thickness direction of the coal seam 2, and the extension direction of the coal seam 2 is perpendicular to the plane direction of the thickness of the coal seam 2. The coal seam 2 and the ground surface 1 can be arranged in parallel or at an angle. The first target area 21 can be located in the upper layer, middle layer or lower layer of the coal seam 2 in the thickness direction.

[0044] In the coal seam 2, the first target area 21 is provided with first shafts 101 on opposite sides at least in one direction. The displacement effect of the first shaft 101 can be effectively improved. For example, along the radial direction of the second shaft 201, at least two first shafts 101 are placed on both sides of the first target area 21. In one example, at least two first shafts 101 are provided within a range of 200 meters with the first target area 21 as the center.

[0045] The injection device 400 is a device for providing carbon dioxide to the second well 201. The injection device 400 is arranged on the surface 1 or in the second well 201, and is connected to the second well 201. In one example, the injection device 400 includes a carbon dioxide storage tank and a driving pump, and the driving pump pumps carbon dioxide into the second well 201. In another example, the injection device 400 also includes an extension pipe, which is connected to the driving pump and extends to a certain depth in the second well 201. Reduce the diffusion of carbon dioxide in other rock formations.

[0046] For example, the injection device 400 and the extraction device 300 can be turned on at the same time, or the extraction device 300 works for a period of time before the injection device 400 is turned on. While the injection device 400 injects carbon dioxide to displace the coalbed methane, the extraction device 300 extracts the displaced coalbed methane. The extraction device 300 has a stripping force on the coalbed methane adsorbed in the wellbore, which is more conducive to the displacement of carbon dioxide and improves the displacement efficiency of carbon dioxide.

[0047] The first diving section 210 of the second shaft 201 is set at an angle to the first extension section 211, so as to increase the contact area between the first extension section 211 and the coal seam 2, thereby increasing the diffusion area of ​​carbon dioxide in the coal seam 2 and improving the displacement effect of carbon dioxide on the multiple first shafts 101; and the first target area 21 formed by the second shaft 201 in the coal seam 2 is placed between the multiple first shafts 101 to achieve uniform displacement of the multiple first shafts 101.

[0048] In one embodiment of the present application, the first submerged section 210 is extended perpendicularly to the ground surface 1, and the first extension section 211 is arranged at an angle to the first submerged section 210. Exemplarily, the extension direction of the first extension section 211 is arranged at an angle or parallel to the extension direction of the coal seam 2. In one example, the second shaft 201 is a directional well.

[0049] Continue to refer Figure 1 In an optional embodiment of the present application, the injection shaft 200 also includes a casing, which extends from the surface 1 to the side of the coal seam 2 close to the surface 1, and the casing is placed in the second shaft 201 and is connected to the injection device 400.

[0050] Exemplarily, the coal seam 2 includes a roof 22 and a bottom plate 23 which are arranged opposite to each other along the thickness direction of the coal seam 2, the roof 22 being arranged on the side of the coal seam 2 close to the ground surface 1, and the bottom plate 23 being arranged on the side of the coal seam 2 away from the ground surface 1. The casing extends from the ground surface 1 to the roof 22. That is, the second shaft 201 is an open well when in the coal seam 2.

[0051] Exemplarily, the casing may be disposed in the first submerged section 210 , or in the first submerged section 210 and a portion of the first extending section 211 .

[0052] The casing is extended to the side of the coal seam 2 close to the ground surface 1, thereby reducing the diffusion of the carbon dioxide injected by the injection device 400 before reaching the coal seam 2, increasing the displacement area, and further improving the displacement effect.

[0053] Continue to refer Figure 1 In an optional embodiment of the present application, along the thickness direction of the coal seam 2, the distance between the first target area 21 and the side of the coal seam 2 facing away from the ground surface 1 is less than or equal to the distance between the first target area 21 and the side of the coal seam 2 close to the ground surface 1.

[0054] That is, along the thickness direction of the coal seam 2, the distance between the first target area 21 and the roof 22 is greater than or equal to the distance between the first target area 21 and the bottom plate 23. In one example, the first target area 21 and the end of the first shaft 101 are at the same height relative to the roof 22 along the thickness direction of the coal seam 2.

[0055] By placing the first target area 21 close to the side of the coal seam 2 facing away from the ground surface 1 , the length of the first extension section 211 in the thickness direction of the coal seam 2 is extended, thereby increasing the contact area with the coal seam 2 and further improving the displacement effect.

[0056] Figure 3 Another schematic layout diagram of the application of CCUS-ECBM carbon dioxide displacement of coalbed methane provided in some embodiments of the present application.

[0057] like Figure 1 and Figure 3 As shown, in another embodiment of the present application, the end of the first submerged section 210 facing away from the surface 1 is placed in the coal seam 2, and the first extension section 211 is extended along the extension direction of the coal seam 2 and is arranged between multiple first shafts 101.

[0058] In one example, the first submerged section 210 is a vertical well perpendicular to the ground surface 1, the end of the first submerged section 210 is placed at a height position close to the roof 22 of the coal seam 2, and the casing is arranged in the first submerged section 210. The first extension section 211 can be arranged parallel to the coal seam 2 and extend along the coal seam 2.

[0059] In another example, the plurality of first shafts 101 are at least disposed on two opposite sides of the first extension section 211 in the radial direction.

[0060] The first extension section 211 is extended along the extension direction of the coal seam 2, thereby increasing the contact area between the second shaft 201 and the coal seam 2, increasing the diffusion area of ​​carbon dioxide, and displacing more first shafts 101.

[0061] Figure 4 Another schematic layout diagram of the application of CCUS-ECBM carbon dioxide displacement of coalbed methane provided in some embodiments of the present application.

[0062] like Figure 1and Figure 4 As shown, in an optional embodiment of the present application, the end of the first shaft 101 away from the ground surface 1 forms a second target area 24 in the coal seam 2, and along the extension direction of the coal seam 2, the first target area 21 is placed between the second target areas 24 of multiple first shafts 101.

[0063] The second target area 24 is the end position of the first shaft 101 in the coal seam 2. For example, the second target area 24 can be a circular area with the target point as the center, or a rectangular area with the target point as the center and a certain offset and along distance from the target center. In a highly deviated well or a horizontal well, the target area may be a cylindrical volume.

[0064] The second target area 24 is the main suction position when extracting coalbed methane. The first target area 21 is set between multiple second target areas 24 to improve the displacement effect and the extraction effect of coalbed methane.

[0065] In order to ensure a uniform displacement effect of the second shaft 201 on the multiple shafts, in some embodiments of the present application, the first target area 21 and the second target areas 24 of the multiple first shafts 101 are spaced equally apart.

[0066] In one example, the extraction well 100 includes two first wells 101, the two first wells 101 may be vertical wells or directional wells, and the first target area 21 is set in the middle of the line connecting the second target areas 24 of the two first wells 101. For example, the center of the first target area 21 is 200 meters away from the center of the second target area 24.

[0067] In another example, the extraction well 100 includes three first wells 101, the three first wells 101 may be vertical wells or directional wells, and the center of the circumscribed circle of the second target area 24 of the three first wells 101 is the center position of the first target area 21. For example, the center of the first target area 21 is 200 meters away from the center of the second target area 24.

[0068] The distance between the first target area 21 and the second target area 24 is equal within a certain error range, for example, approximately equal.

[0069] Figure 5 Another schematic layout diagram of the application of CCUS-ECBM carbon dioxide displacement of coalbed methane provided in some embodiments of the present application.

[0070] like Figure 4 and Figure 5 As shown, in some specific embodiments of the present application, at least one first shaft 101 includes a second submerged section 110 and a second extension section 111 which are successively and connected along its own extension direction, the second submerged section 110 is extended along the first direction X, and the second extension section 111 extends along the second direction Y to the coal seam 2, and the first direction X intersects with the second direction Y.

[0071] One, two or all of the first shafts 101 in the extraction shaft 100 may have a second submerged section 110 and a second extended section 111. Exemplarily, one, two or all of the first shafts 101 in the extraction shaft 100 may be directional wells.

[0072] For example, the first direction X may be a thickness direction of the coal seam 2, or a stacking direction of the ground surface 1 and the coal seam 2. The second direction Y may be a direction perpendicular to the first direction X.

[0073] The end of the second submerged section 110 can be placed in the coal seam 2 or between the coal seam 2 and the ground surface 1 along the thickness direction of the coal seam 2. The second extension section 111 can be arranged at an angle to the coal seam 2 or parallel to the extension direction of the coal seam 2. The second submerged section 110 is arranged at an angle to the second extension section 111.

[0074] In one example, the end of the second extension section 111 forms a second target area 24 on the coal seam 2 .

[0075] like Figure 1 As shown, in an optional embodiment of the present application, the first shaft 101 includes a second submerged section 110 extending from the ground surface 1 to the coal seam 2 along a first direction X, and the second submerged section 110 is arranged side by side with the first submerged section 210 .

[0076] Exemplarily, the first wellbore 101 is a vertical well perpendicular to the ground surface 1 , and the first submerged section 210 is a vertical well section perpendicular to the ground surface 1 .

[0077] like Figures 1 to 3 As shown, in other optional embodiments of the present application, the second shaft 201 includes a fracture gap 230 , and the fracture gap 230 extends along the coal seam 2 toward at least one first shaft 101 .

[0078] For example, the fractured gap 230 may be formed by hydraulic fracturing or grouting fracturing, and sand flushing is performed in the gap.

[0079] In one example, the fracturing gap 230 is formed in the first target area 21 , that is, the end of the second shaft 201 at the coal seam 2 .

[0080] In another example, in the coal seam 2 , the fracturing gap 230 is formed around the first extension section 211 along the extension direction of the first extension section 211 .

[0081] The fracture gap 230 may make it easier for the carbon dioxide in the second shaft 201 to displace the coal seam methane in the coal seam 2, thereby improving the displacing effect.

[0082] Furthermore, in one embodiment of the present application, the carbon dioxide is in liquid state.

[0083] The gas adsorption capacity of coal seam 2 is limited, and different gases have different adsorption priorities in coal seam 2. Since the molecular diameter of carbon dioxide is smaller than that of methane, which is one of the main components of coal seam gas, and the adsorption force of coal seam 2 on carbon dioxide is greater than that of methane, when carbon dioxide is injected into coal seam 2, carbon dioxide will be preferentially adsorbed on the coal surface, thereby crowding out and replacing the methane originally adsorbed in coal seam 2. This competitive adsorption and replacement effect is one of the key mechanisms for improving coalbed methane recovery.

[0084] After the injection of carbon dioxide, the coal matrix will undergo adsorption expansion and effective stress changes, which will further change the size and connectivity of the coal matrix micropores. The change in micropore size will affect the storage and migration characteristics of coalbed methane, while the improvement in connectivity will help the desorption and diffusion of methane. These factors work together to improve the efficiency of methane extraction.

[0085] By injecting carbon dioxide into the coal seam 2, not only can the methane originally adsorbed in the coal seam 2 be replaced, but also the desorption and diffusion of methane in the coal seam 2 can be promoted. At the same time, the injection of carbon dioxide will also reduce the partial pressure of methane in the pores and cracks, breaking the original adsorption and desorption equilibrium state, so that methane needs to be further desorbed to reach a new equilibrium, so that the concentration and flow rate of methane produced by the first shaft 101 increase.

[0086] Compared with gaseous carbon dioxide, liquid carbon dioxide has a higher displacement efficiency in the short term, can quickly form a high pressure gradient and drive coalbed methane to the production well. Liquid carbon dioxide has a higher density than gaseous carbon dioxide and can better penetrate into the pores deep in the coal seam. Liquid carbon dioxide will quickly convert into gas during the injection process, producing a large volume expansion effect. This volume expansion further promotes the displacement of coalbed methane.

[0087] In addition, in another embodiment of the present application, the injection pressure of the injection device 400 is in the range of 10 MPa to 30 MPa. The replacement volume ratio of carbon oxide and coalbed methane is increased, thereby improving the displacement efficiency.

[0088] In one example, the injection pressure is 20 MPa, which can make the replacement volume ratio of carbon dioxide and coalbed methane be: carbon dioxide: methane = 2:1.

[0089] During the coalbed methane extraction process, once the gas adsorption and desorption reach a dynamic equilibrium, the osmotic pressure inside the coalbed 2 is basically uniform, and there is no gas seepage under the action of the pressure gradient. However, when carbon dioxide is injected into the coalbed 2 through the gas injection well 200, the pressure at the gas injection end rises rapidly, thereby forming a certain pressure gradient again between the gas injection well 200 and the extraction well 100, i.e., the production well, of the coalbed 2. The existence of this pressure gradient promotes the seepage movement of gas in the coalbed, which helps to improve the extraction efficiency of coalbed methane. The gas includes injected carbon dioxide and produced methane.

[0090] Figure 6 The figure is a flow chart of a CCUS-ECBM carbon dioxide displacement coalbed methane technology method.

[0091] like Figures 1 to 6 As shown, in some embodiments of the present application, a CCUS-ECBM carbon dioxide displacement coalbed methane technical method based on the above-mentioned CCUS-ECBM carbon dioxide displacement coalbed methane application includes the following steps: S1: In a working area having multiple first shafts 101, at least one second shaft 201 having a first diving section 210 and a first extension section 211 arranged at an angle is drilled from the surface 1 to the coal seam 2, so that a first target area 21 formed by the second shaft 201 in the coal seam 2 is placed between the multiple first shafts 101 in the coal seam 2.

[0092] The first shaft 101 is used to extract coalbed methane in the coal seam 2. The first shaft 101 extends from the ground surface 1 to the coal seam 2. The first shaft 101 is equipped with an extraction device 300.

[0093] Exemplarily, the second wellbore 201 may be a directional well. For example, the second wellbore 201 is a horizontal well.

[0094] S2: Install the injection device 400 on the ground surface 1 and connect the injection device 400 to the second well 201 .

[0095] S3: Open the injection device 400 and the extraction device 300 of the first shaft 101 , inject carbon dioxide into the second shaft 201 through the injection device 400 to displace the coalbed methane in the multiple first shafts 101 .

[0096] The second shaft 201 injects carbon dioxide while the extraction device 300 extracts carbon dioxide through the first shaft 101. The second shaft 201 displaces the coalbed methane in the surrounding first shafts 101, thereby improving the extraction efficiency of coalbed methane.

[0097] After the extraction of coalbed methane is completed, carbon dioxide can be continuously injected through the second shaft 201 to achieve the sealing of carbon dioxide in the first shaft 101 and the second shaft 101. The carbon dioxide sealed in the first shaft 101 and the second shaft 101 is less affected by the extraction and is more conducive to long-term sealing.

[0098] The above is only a specific implementation of the present application. Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working processes of the systems, modules and units described above can refer to the corresponding processes in the aforementioned method embodiments, and will not be repeated here. It should be understood that the protection scope of the present application is not limited to this. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in this application, and these modifications or replacements should be included in the protection scope of this application.

Claims

1. A CCUS-ECBM carbon dioxide displacement coalbed methane technology method, characterized in that: include: In a working area having a plurality of first shafts, drilling at least one second shaft having a first descending section and a first extending section arranged at an angle from the surface to the coal seam, so that a first target area formed by the second shaft in the coal seam is located between the plurality of first shafts in the coal seam; Installing an injection device on the ground surface, and connecting the injection device to the second well; The injection device and the extraction device of the first shaft are turned on, and carbon dioxide is injected into the second shaft through the injection device to displace the coalbed methane in multiple first shafts.

2. An application of CCUS-ECBM carbon dioxide displacement of coalbed methane, characterized in that: include: The extraction shaft comprises a plurality of first shafts arranged at intervals, wherein the first shafts extend from the ground surface to the coal seam in their own extension direction; An injection shaft, comprising at least one second shaft, wherein the second shaft runs from the ground surface to the coal seam along its own extension direction, wherein the second shaft comprises a first submerged section and a first extension section which are arranged successively and connected along its own extension direction, wherein the first submerged section and the first extension section are arranged at an angle, wherein an end of the first extension section which is away from the first submerged section forms a first target area in the coal seam, and within the coal seam and along the extension direction of the coal seam, the first target area is placed between a plurality of the first shafts; a pumping device connected to the first well; An injection device is connected to the second shaft, and is configured to inject carbon dioxide into the second shaft when the extraction device extracts the coalbed methane, so as to displace the coalbed methane in multiple first shafts.

3. The application of CCUS-ECBM carbon dioxide displacement of coalbed methane according to claim 2 is characterized in that: The injection shaft also includes a casing, which extends from the ground surface to a side of the coal seam close to the ground surface. The casing is placed in the second shaft and is connected to the injection device.

4. The use of CCUS-ECBM carbon dioxide to displace coalbed methane according to claim 3, characterized in that: Along the thickness direction of the coal seam, the distance between the first target area and the side of the coal seam away from the ground surface is less than or equal to the distance between the first target area and the side of the coal seam close to the ground surface.

5. The use of CCUS-ECBM carbon dioxide to displace coalbed methane according to any one of claims 2 to 4, characterized in that: The end of the first submerged section facing away from the ground surface is placed in the coal seam, and the first extension section is extended along the extension direction of the coal seam and is arranged between the plurality of first shafts.

6. The use of CCUS-ECBM carbon dioxide to displace coalbed methane according to claim 2, characterized in that: The end of the first shaft away from the ground surface forms a second target area in the coal seam, and along the extension direction of the coal seam, the first target area is placed between the second target areas of the plurality of first shafts.

7. The use of CCUS-ECBM carbon dioxide to displace coalbed methane according to claim 6, characterized in that: The first target area is equidistant from the second target areas of the first shafts.

8. The use of CCUS-ECBM carbon dioxide to displace coalbed methane according to claim 2 or 6, characterized in that: At least one of the first shafts includes a second diving section and a second extension section which are successively and connectedly arranged along its own extension direction, the second diving section is extended along the first direction, the second extension section extends to the coal seam along the second direction, and the first direction intersects with the second direction.

9. The use of CCUS-ECBM carbon dioxide to displace coalbed methane according to claim 2 or 6, characterized in that: The first shaft includes a second submerged section extending from the ground surface to the coal seam along a first direction, and the second submerged section is arranged side by side with the first submerged section.

10. The use of CCUS-ECBM carbon dioxide to displace coalbed methane according to claim 2, characterized in that: The second shaft includes a fractured gap extending along the coal seam toward at least one of the first shafts.

11. The use of CCUS-ECBM carbon dioxide to displace coalbed methane according to claim 2, characterized in that: The carbon dioxide is in liquid state.

12. The use of CCUS-ECBM carbon dioxide to displace coalbed methane according to claim 2, characterized in that: The injection pressure of the injection device ranges from 10 MPa to 30 MPa.

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