Deep coal bed gas and coal underground gasification collaborative mining method

Abstract

The invention relates to a deep coal bed gas and coal underground gasification collaborative mining method which comprises the steps that coal bed gas wells are drilled and comprise a vertical well and a first horizontal well, and then coal bed gas is mined; an underground gasification production well is drilled at a safe distance from the coal-bed gas well, a second horizontal well is arranged at the bottom of the production well, and the first horizontal well and the second horizontal well are arranged in the same direction; an injection well is drilled, a third horizontal well is arranged at the bottom of the injection well, and the first horizontal well and the second horizontal well are both perpendicular to the third horizontal well; a continuous oil pipe is arranged in the injection well and used for inputting a gasifying agent, and openable air outlets are formed in the positions, corresponding to the first horizontal well and the second horizontal well, of the continuous oil pipe correspondingly so that the gasifying agent can be conveniently provided; carrying out gasification combustion one by one corresponding to each production well, and outputting coal gas obtained by combustion from the corresponding production well; meanwhile, gas produced by the coal-bed gas well is increased again, and coal-bed gas is collected; and coal-bed gas and coal gas collection is finished, gasification combustion is carried out one by one corresponding to each coal-bed gas well, and coal gas obtained through combustion is output by the corresponding coal-bed gas well.

Description

Technical Field

[0001] The invention belongs to the technical field of coalbed methane and coal mining, and specifically relates to a method for coordinated mining of deep coalbed methane and underground coal gasification. Background Art

[0002] my country is rich in coal and coalbed methane resources. At present, the depth of coal mining is mainly shallower than 1000m. Coal seams deeper than 1000m are difficult to mine due to complex geological conditions and mining technology. At present, vertical wells and horizontal wells are commonly used for deep coalbed methane mining. However, due to the complex mining geological conditions and high deep ground stress, deep coalbed methane is difficult to transform the reservoir fracture network, and the mining efficiency of deep coalbed methane is often low. It can be seen that the full development of deep coalbed methane and coal resources is a problem faced by technical personnel in this field. Summary of the invention

[0003] In view of the above problems, the present invention provides a method for coordinated mining of deep coalbed methane and underground coal gasification, comprising the following steps: S1: Drill at least one coalbed methane well from the ground downward, the coalbed methane well includes a vertical well and a horizontal well connected up and down, and then exploit the coalbed methane; S2: At least one production well is drilled at a safe distance from the coalbed methane well. The bottom of the production well is horizontal well 2. Horizontal well 1 and horizontal well 2 are set in the same direction, and the end of horizontal well 1 is flush with the end of horizontal well 2. S3: Drill an injection well. The structure of the production well is the same as the main structure of the injection well. The bottom of the injection well is horizontal well 3. Horizontal wells 1, 2 and 3 are all in the coalbed methane reservoir and at the same depth. Horizontal wells 1 and 2 are both perpendicular to horizontal well 3. A coiled tubing is set in the injection well for inputting the gasifying agent. The coiled tubing in the horizontal well 3 is provided with openable and closable gas outlets at positions corresponding to the horizontal well 1 and the horizontal well 2, respectively, to facilitate the supply of the gasifying agent. S4: Gasification and combustion are carried out one by one for each production well, and the coal gas obtained by combustion is output from the corresponding production well; at the same time, affected by the increase in gasification and combustion temperature, the coalbed methane is further analyzed from the coal reservoir, and the gas production of the coalbed methane well increases again, and coalbed methane is collected; S5: End the coalbed methane and coal gas collection, and perform gasification combustion on each coalbed methane well one by one, and the coal gas obtained by combustion is output from the corresponding coalbed methane well.

[0004] Preferably, in step S1, two parallel coalbed methane wells are drilled, and a safe distance is provided between the two coalbed methane wells so that a coal gas production well for underground coal gasification can be located between the two coalbed methane wells.

[0005] Optionally, in step S2, when the gas production of the coalbed methane well reaches the end stage, the gas production of the coalbed methane well is suspended; a plurality of production wells parallel to each other are drilled between the two coalbed methane wells, the production wells including a longitudinal well section from the ground downward and a horizontal well 2 in the horizontal direction, and the horizontal well 1 is parallel to the horizontal well 2; Conventional casing completion is carried out in the production well, and perforation is carried out on the second horizontal well to connect the second horizontal well with the external reservoir environment so that the coal gas produced by coal gasification can enter the second horizontal well.

[0006] Optionally, in step S3, the injection well includes a longitudinal well section from the ground downward and a horizontal well three; At least one extended well section is respectively provided at the position of horizontal well 3 corresponding to horizontal well 2 and horizontal well 1. One end of the extended well section is connected to horizontal well 3, and the other end points to the top or bottom of horizontal well 3. The extended well section can be vertical or inclined toward the direction of the corresponding horizontal well 2 or horizontal well 1. Conventional casing completion is carried out in the injection well, and perforations are performed on the side walls of horizontal well 3 at positions corresponding to horizontal well 2 and horizontal well 1, respectively, to connect horizontal well 3 with the external reservoir environment. The perforations of horizontal well 3 are concentrated on the half-circle side walls facing horizontal well 2 or horizontal well 1, so that the gasification agent is output toward the production well or coalbed methane well.

[0007] Further optionally, the extended well section is kept in an open hole state without casing completion, and when the horizontal well three is completed, an expandable packer is used to temporarily block one end of the extended well section connected to the horizontal well three to prevent concrete from entering the extended well section.

[0008] Optionally, at least one gas pipe is provided inside the coiled tubing for inputting gasifying agent; In horizontal well three, the relative positions of the coiled tubing and the internal gas pipe are fixed, and the gas pipes are provided with connecting pipes at positions corresponding to horizontal wells one and two. The coiled tubings are provided with openable and closable gas outlets at positions corresponding to horizontal wells one and two. The connecting pipes are connected to the corresponding gas outlets to form targeted gasification agent output.

[0009] Further optionally, a plurality of pairs of openable and closable gas blocking components are provided on the outer side wall of the coiled tubing, and a pair of gas blocking components are respectively provided on both sides of a gas outlet along the length direction of the horizontal well three; A number of gas blocking components are arranged on the inner wall of the horizontal well three. The gas blocking components correspond to the gas blocking components one by one, and together they form a circle of baffles, which are arranged between the coiled tubing and the horizontal well three to block the gasifying agent output from the gas outlet near the gas outlet, and try to avoid the gasifying agent from diffusing along the horizontal well three, but output it from the perforation holes corresponding to the gas outlet.

[0010] Further optionally, the air blocking assembly includes a fixing ring and a plurality of air blocking sheets, the fixing ring surrounds the outer wall of the coiled tubing, and the fixing ring points to the inner wall of the horizontal well along the radial direction of the coiled tubing; the air blocking sheets are evenly distributed along the circumference of the coiled tubing, the tail of the air blocking sheet is hinged to the side of the fixing ring facing the wellhead of the injection well, the air blocking sheet is a straight plate, and the width of the head of the air blocking sheet is smaller than the width of the tail of the air blocking sheet; there is a gap between two adjacent air blocking sheets, so that the air blocking sub-sheet of the air blocking sub-piece can be arranged between the two blocking sheets to form a complete annular plane; The folded state of the air blocking sheet is that the air blocking sheet is close to the outer wall of the coiled tubing and is arranged in the same direction as the coiled tubing; the unfolded state of the air blocking sheet is that the air blocking sheet is rotated to a vertical state and close to the side of the fixing ring.

[0011] Further optionally, the air-blocking auxiliary component includes a fixed auxiliary ring and a plurality of air-blocking auxiliary sheets, the fixed auxiliary ring surrounds the inner wall of the horizontal well three, and the fixed auxiliary ring points to the coiled tubing along the radial direction of the horizontal well three; the air-blocking auxiliary sheets are evenly distributed along the circumference of the horizontal well three, the tail of the air-blocking auxiliary sheet is hinged to the side of the fixed auxiliary ring facing the wellhead of the injection well, the air-blocking auxiliary sheet is a straight plate, and the width of the head of the air-blocking auxiliary sheet is smaller than the width of the tail of the air-blocking auxiliary sheet; there is a gap between two adjacent air-blocking auxiliary sheets, so that the air-blocking sheet can be arranged between the two air-blocking auxiliary sheets to form a complete annular plane; The folded state of the air-blocking sub-piece is that the air-blocking sub-piece is close to the inner wall of the horizontal well three and is arranged in the same direction as the horizontal well three; the unfolded state of the air-blocking sub-piece is that the air-blocking sub-piece is rotated to a vertical state and is close to the side of the fixed sub-ring.

[0012] Optionally, in step S4, starting from a production well close to a coalbed methane well, gasification and combustion are carried out one by one on each production well in the direction close to another coalbed methane well, and only one production well is targeted at each time to avoid reservoir collapse; during gasification, the gas blocking components and gas blocking subcomponents on both sides of the corresponding gas outlet are opened, and then the corresponding gas outlet is opened to release the gasifying agent and ignite it. The gasifying agent diffuses from the perforated holes to the reservoir and the extended well section, and burns the coal. The extended well section becomes the initial gasification chamber, which is conducive to the expansion of heat to various parts of the reservoir thickness. The gasification chamber as a whole advances toward the corresponding production well, and the generated coal gas is discharged from the production well. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the structure of the coalbed methane well, the production well and the injection well in the embodiment; Figure 2 It is a schematic diagram of the extended well section of horizontal well 3; Figure 3 It is a schematic diagram of the coiled tubing and the gas pipe; Figure 4 is a schematic longitudinal section diagram of a gas barrier component; Figure 5It is a side schematic diagram when the air barrier assembly is not deployed; Figure 6 It is a side view schematic diagram of the air barrier assembly when it is half deployed; Figure 7 It is a schematic longitudinal section diagram of the gas barrier sub-component.

[0014] In the attached drawings, 1-coalbed methane well, 2-production well, 3-injection well, 4-horizontal well one, 5-horizontal well two, 6-horizontal well three, 7-continuous oil pipe, 8-gas pipe, 9-gas outlet, 10-connecting pipe, 11-extended well section, 12-fixing ring, 13-fixed sub-ring, 14-gas blocking plate, 15-gas blocking sub-plate. DETAILED DESCRIPTION

[0015] This embodiment provides a method for coordinated exploitation of deep coalbed methane and underground coal gasification, such as Figure 1-Figure 7 As shown, the following steps are included: S1: Drill two coalbed methane wells 1 from the ground downward, the coalbed methane well 1 includes a vertical well and a horizontal well 4 connected up and down, and then extract the coalbed methane; S2: Three production wells 2 are drilled at a safe distance from the coalbed methane well 1. The bottom of the production well 2 is the horizontal well 2 5. The horizontal well 1 4 and the horizontal well 2 5 are arranged in the same direction. The end of the horizontal well 1 4 is flush with the end of the horizontal well 2 5. S3: Drill an injection well 3. The structure of the production well 2 is the same as the main structure of the injection well 3. The bottom of the injection well 3 is the horizontal well 3 6. The horizontal wells 1 4, 2 5 and 3 6 are all in the coalbed methane reservoir and at the same depth. The horizontal wells 1 4 and 2 5 are both perpendicular to the horizontal well 3 6. A coiled tubing 7 is provided in the injection well 3 for inputting the gasifying agent, and the coiled tubing 7 in the horizontal well 3 6 is provided with openable and closable gas outlets 9 at positions corresponding to the horizontal well 1 4 and the horizontal well 2 5, respectively, for providing the gasifying agent; S4: gasification and combustion are performed one by one in correspondence with each production well 2, and the coal gas obtained by combustion is output from the corresponding production well 2; at the same time, the gas production of the coalbed methane well 1 is increased again, and coalbed methane is collected; S5: End the coalbed methane and coal gas collection, and perform gasification combustion on each coalbed methane well 1 one by one, and the coal gas obtained by combustion is output from the corresponding coalbed methane well 1.

[0016] The present invention conducts synergistic exploitation of deep coalbed methane and coal, which can promote each other and increase production at the same time. Specifically, step S1 is the drilling and exploitation of a conventional coalbed methane well 1, which also faces the problems of difficulty in transforming the reservoir seam network, low mining efficiency, and low gas production. The present invention drills at least one production well 2 next to the coalbed methane well 1, and the horizontal well 1 4 is arranged in the same direction as the horizontal well 2 5. The drilling, completion, and perforation processes of the horizontal well 2 5 and the horizontal well 3 6 can transform the coalbed methane reservoir again, so that new cracks are generated in the reservoir between the horizontal well 1 4 and the horizontal well 2 5, and at the same time, it is also beneficial for the original cracks around the horizontal well 1 4 to be expanded again, so that the cracks are enriched, complicated, and multi-branched, which is beneficial for the coalbed methane to continue to overflow and increase production.

[0017] Traditionally, injection wells correspond to production wells one by one, and the injection wells can output gasification agents to the production wells, and burn and gasify the coal seam between the injection wells and the production wells. The present invention designs the production well 2 to be a well type with the same structure as the injection well 3. The injection well 3 is based on the form of the horizontal well 1 4 and the horizontal well 2 5. From a bird's-eye view, the horizontal well 1 4 and the horizontal well 2 5 are both perpendicular to the horizontal well 3 6. The horizontal well 3 6 is connected to a continuous oil pipe 7, which can input gasification agents and provide gasification agents for each horizontal well 1 4 and the horizontal well 2 5. That is, one injection well 3 corresponds to multiple production wells 2, which greatly saves the number of injection wells 3 and reduces the construction volume and cost.

[0018] The previous drilling, fracturing and gas production operations of CBM Well 1 have improved the microstructure of the reservoir, increased the number of fractures in the reservoir, as well as the depth and breadth of the fractures, and improved the permeability of the reservoir, which is conducive to the efficient transfer of gasification agents and heat in the reservoir during subsequent gasification, thereby improving the gasification efficiency. After the gasification operation of production well 2, the CBM collection is terminated, and CBM Well 1 plays the role of production well 2, gasifying the coal seam between CBM Well 1 and injection well 3, and fully exploiting and utilizing the reservoir coal and CBM resources.

[0019] Step S1 is a conventional coalbed methane mining technology. The conventional coalbed methane well 1 includes a vertical well and a horizontal well 4. The upper part of the vertical well is vertically downward, and the lower part is inclined downward. The drilling direction is gradually changed until the drilling reaches the horizontal well 4 and changes to the horizontal direction.

[0020] In step S1 , two coalbed methane wells 1 are spaced apart by a safety distance from the coalbed methane wells 1 , so that the production well 2 can be located between the two coalbed methane wells 1 .

[0021] Optionally, in step S2, when the gas production of the coalbed methane well 1 reaches the end stage, the gas production of the coalbed methane well 1 is suspended; three parallel production wells 2 are drilled between two coalbed methane wells 1, and the production wells include a longitudinal well section from the ground downward and a horizontal well 2 5 in the horizontal direction, and the horizontal well 1 4 is parallel to the horizontal well 2 5; Conventional casing completion is performed in the production well 2 , and perforation is performed on the horizontal well 2 5 to connect the horizontal well 2 5 with the external reservoir environment, so that the coal gas produced by coal gasification can enter the horizontal well 2 5 .

[0022] In the prior art, the stable gas production stage of the coalbed methane well 1 is followed by a gas production decline stage, and the time for suspending gas production is reasonably determined based on the actual gas production situation and economic calculation. The bottom of the production well 2 is the horizontal well 2 5, and the positional relationship between the start of the horizontal well 1 4 and the start of the horizontal well 2 5 is not limited.

[0023] The safety distance between two coalbed methane wells 1 is greater than the safety distance between two production wells 2 , so that several production wells 2 can be set between the two coalbed methane wells 1 .

[0024] Optionally, the injection well 3 includes a longitudinal well section from the ground downward and a horizontal well section 6 in the transverse direction; An extended well section 11 is respectively provided at the position of the horizontal well 3 6 corresponding to the horizontal well 2 5 and the horizontal well 1 4. One end of the extended well section 11 is connected to the horizontal well 3 6, and the other end points to the top of the horizontal well 3 6. The extended well section 11 can be vertical or inclined toward the corresponding horizontal well 2 5 or horizontal well 1 4. Conventional casing completion is carried out in the injection well 3, and perforations are performed on the side walls of the horizontal well three 6 at positions corresponding to the horizontal well two 5 and the horizontal well one 4, respectively, to connect the horizontal well three 6 with the external reservoir environment. The perforations of the horizontal well three 6 are concentrated on the half circle side wall facing the horizontal well two 5 or the horizontal well one 4, so that the gasification agent is output toward the production well 2 or the coalbed methane well 1.

[0025] Further optionally, the extended well section 11 is kept in an open hole state without casing completion, and when the horizontal well three 6 is completed, an expandable packer is used to temporarily block the end of the extended well section 11 connected to the horizontal well three 6 to prevent concrete from entering the extended well section 11.

[0026] The gasification agent of the present invention is too dispersed in the horizontal direction when entering the horizontal well 36. Moreover, the diameter of the horizontal well 36 is smaller than the reservoir thickness. If the wall of the horizontal well 36 is perforated evenly, the gasification agent will be wasted and the coal gasification will be insufficient.

[0027] In response to the above problems, horizontal well three 6 is provided with an extended well section 11 at the position corresponding to horizontal well one 4 and horizontal well two 5. The extended well section 11 plus horizontal well three 6 is basically equal to the thickness of the reservoir. The extended well section 11 extends upward and downward respectively, and perforation is performed at this position, so that the gasification agent at this position can be output from horizontal well three 6, and then diffuse in the extended well section 11 with basically no resistance, so that the gasification agent is dispersed in the thickness direction of the reservoir at this position, which is conducive to the full combustion of the coal seam.

[0028] Optionally, at least one gas pipe 8 is sleeved inside the coiled tubing 7 for inputting gasifying agent; In the horizontal well 3 6, the relative positions of the coiled tubing 7 and the internal gas pipe 8 are fixed, and the gas pipe 8 is provided with a connecting pipe 10 at the positions corresponding to the horizontal well 1 4 and the horizontal well 2 5. The coiled tubing 7 is provided with an openable gas outlet 9 at the positions corresponding to the horizontal well 1 4 and the horizontal well 2 5, and the connecting pipe 10 is connected to the corresponding gas outlet 9 to form a targeted gasification agent output. A valve is provided at the gas outlet 9 to control the opening or closing of the gas outlet 9.

[0029] Further optionally, a plurality of pairs of openable and closable gas blocking components are provided on the outer side wall of the coiled tubing 7, and a pair of gas blocking components are provided along the length direction of the horizontal well 3 6 and on both sides of a gas outlet 9 respectively; A number of gas blocking components are provided on the inner wall of the horizontal well three 6. The gas blocking components correspond to the gas blocking components one by one, and together they form a circle of baffles, which are provided between the coiled tubing 7 and the horizontal well three 6 to block the gasifying agent output from the gas outlet 9 near the gas outlet 9, and try to avoid the gasifying agent from diffusing along the horizontal well three 6, but output it from the perforation holes corresponding to the gas outlet 9.

[0030] Further optionally, the air blocking assembly includes a fixing ring 12 and a plurality of air blocking sheets 14, the fixing ring 12 surrounds the outer wall of the coiled tubing 7, and the fixing ring 12 points to the inner wall of the horizontal well 3 6 along the radial direction of the coiled tubing 7; the air blocking sheets 14 are evenly distributed along the circumference of the coiled tubing 7, and the tail of the air blocking sheet 14 is hinged to the side of the fixing ring 12 facing the wellhead of the injection well 3, the air blocking sheet 14 is a straight plate, and the width of the head of the air blocking sheet 14 is smaller than the width of the tail of the air blocking sheet 14; there is a gap between two adjacent air blocking sheets 14, so that the air blocking sub-sheet 15 of the air blocking sub-component can be arranged between the two blocking sheets 14 to form a complete annular plane; The folded state of the air blocking sheet 14 is that the air blocking sheet 14 is close to the outer wall of the coiled tubing 7 and is arranged in the same direction as the coiled tubing 7; the unfolded state of the air blocking sheet 14 is that the air blocking sheet 14 is rotated to a vertical state and close to the side of the fixing ring 12.

[0031] There are many technologies to realize the rotation of the gas blocking plate 14, such as electromagnetic control, mechanical control, etc. The control device can be set inside the coiled tubing 7. Since the gasification agent is ignited outside the coiled tubing 7, and the combustion and gasification of coal is outside the horizontal well 3 6, the coiled tubing 7 provides protection for the control device, and there is basically no gasification agent in the space between the coiled tubing 7 and the gas pipe 8, which is a relatively safe space. If mechanical control is used, for example, a lifting rod supports the rotation of the gas blocking plate 14, and a sealing ring is set at the position where the lifting rod passes through the side wall of the coiled tubing 7.

[0032] Further optionally, a circle of recessed sealing grooves is provided on the side of the fixing ring 12 facing the air blocking sheet 14, and a sealing strip is provided on the side of the air blocking sheet 14 facing the fixing ring 12. When the air blocking sheet 14 is close to the fixing ring 12, the sealing strip is embedded in the corresponding sealing groove part to play a sealing and air-blocking role. The other parts of the sealing groove are embedded by the sealing strip on the top of the air blocking sub-sheet 15, so that the entire circle of the sealing groove has a sealing strip embedded and sealed.

[0033] Further optionally, the air-blocking auxiliary component includes a fixed auxiliary ring 13 and a plurality of air-blocking auxiliary pieces 15, the fixed auxiliary ring 13 surrounds the inner wall of the horizontal well three 6, and the fixed auxiliary ring 13 points to the continuous oil pipe 7 along the radial direction of the horizontal well three 6; the air-blocking auxiliary pieces 15 are evenly distributed along the circumference of the horizontal well three 6, and the tail of the air-blocking auxiliary piece 15 is hinged to the side of the fixed auxiliary ring 13 facing the wellhead of the injection well 3, the air-blocking auxiliary piece 15 is a straight plate, and the width of the head of the air-blocking auxiliary piece 15 is smaller than the width of the tail of the air-blocking auxiliary piece 15; there is a gap between two adjacent air-blocking auxiliary pieces 15, so that the air-blocking piece 14 can be arranged between the two air-blocking auxiliary pieces 15 to form a complete annular plane; The folded state of the air-blocking sub-piece 15 is that the air-blocking sub-piece 15 is close to the inner wall of the horizontal well three 6 and is arranged in the same direction as the horizontal well three 6; the unfolded state of the air-blocking sub-piece 15 is that the air-blocking sub-piece 15 is rotated to a vertical state and is close to the side of the fixed sub-circle 13.

[0034] The technology for realizing the rotation of the air-blocking sub-piece 15 is the same as the control technology of the air-blocking piece 14 .

[0035] Further optionally, at least one circle of recessed sealing grooves is provided on the side of the fixed sub-ring 13 facing the air-blocking sub-piece 15, and a sealing strip is provided on the side of the air-blocking sub-piece 15 facing the fixed sub-ring 13. When the air-blocking sub-piece 15 is close to the fixed sub-ring 13, the sealing strip is embedded in the corresponding sealing groove part to play a sealing and air-blocking role. The other parts of the sealing groove are embedded by the sealing strip on the top of the air-blocking sheet 14, so that the entire circle of the sealing groove has a sealing strip embedded and sealed.

[0036] Further optionally, longitudinal sealing grooves are respectively provided on both side edges of the side of the air barrier sheet 14 facing the wellhead of the injection well 3, and longitudinal sealing strips are respectively provided on both side edges of the side of the air barrier sub-sheet 15 away from the wellhead of the injection well 3. The air barrier sub-sheet 15 overlaps the air barrier sheet 14, and the longitudinal sealing strips of the air barrier sub-sheet 15 are respectively embedded in the longitudinal sealing grooves of adjacent air barrier sheets 14 to achieve sealing between the air barrier sheet 14 and the air barrier sub-sheet 15.

[0037] Before the gas outlet 9 is discharged, the gas blocking components and gas blocking sub-components on both sides of the gas outlet 9 are deployed and cooperated to form a complete ring, closing the space between the coiled tubing 7 and the horizontal well 3 6. Two barriers are formed on both sides of the gas outlet 9, so that the gasification agent output from the gas outlet 9 is output to the nearby perforated holes. When the gas blocking sheet 14 is retracted, it is close to the coiled tubing 7, and does not affect the lowering of the coiled tubing 7 to the injection well 3. The gas blocking sub-sheet 15 can be installed in the well section of the horizontal well 3 6 in advance, and then lowered into the reservoir. When the gas blocking sub-sheet 15 is retracted, it is close to the inner wall of the well section, and does not affect fracturing and completion.

[0038] Optionally, in step S4, starting from a production well 2 close to a coalbed methane well 1, gasification and combustion are performed one by one on each production well 2 in the direction close to another coalbed methane well 1, and only one production well 2 is targeted at each time to avoid reservoir collapse; during gasification, the gas blocking components and gas blocking sub-components on both sides of the corresponding gas outlet 9 are opened, and then the corresponding gas outlet 9 is opened to release the gasifying agent and ignite it. The gasifying agent diffuses from the perforated holes to the reservoir and the extended well section 11, and burns the coal. The extended well section 11 becomes the initial gasification chamber, which is conducive to the expansion of heat to various parts of the reservoir thickness. The gasification chamber as a whole advances toward the corresponding production well 2, and the generated coal gas is discharged from the production well 2.

[0039] Since there is a safe distance between the adjacent coalbed methane well 1 and the adjacent production well 2 in operation, most of the gas is discharged from the production well 2 in operation, and a small amount of gas can diffuse to both sides. 2 It has a competitive adsorption effect with the methane in the coal seam, which is beneficial to the desorption of methane in the coal seam. When the coal seam burns, it will change the microstructure of the coal seam, which is beneficial to the formation of new cracks and the further expansion of existing cracks, thereby increasing the coalbed methane production again and producing it from coalbed methane well 1, that is, the gas production of production well 2 can promote the increase of coalbed methane again.

[0040] Coal seam gasification combustion is beneficial to the transfer of heat to adjacent coal seams, preheating the adjacent coal seams, and facilitating the full combustion of the subsequent adjacent coal seam gasification.

Claims

1. A method for the coordinated exploitation of deep coalbed methane and underground coal gasification, characterized in that: The following steps are involved: S1: Drill at least one coalbed methane well from the ground downward, the coalbed methane well includes a vertical well and a horizontal well connected up and down, and then exploit the coalbed methane; S2: At least one production well is drilled at a safe distance from the coalbed methane well. The bottom of the production well is horizontal well 2. Horizontal well 1 and horizontal well 2 are set in the same direction, and the end of horizontal well 1 is flush with the end of horizontal well 2. S3: Drill an injection well, the bottom of which is horizontal well 3. Horizontal wells 1, 2 and 3 are all in the coalbed methane reservoir and at the same depth; horizontal wells 1 and 2 are both perpendicular to horizontal well 3; A coiled tubing is set in the injection well for inputting the gasifying agent. The coiled tubing in the horizontal well 3 is provided with openable and closable gas outlets at positions corresponding to the horizontal well 1 and the horizontal well 2, respectively, to facilitate the supply of the gasifying agent. S4: Gasification and combustion are performed one by one for each production well, and the coal gas obtained by combustion is output from the corresponding production well; at the same time, the gas production of the coalbed methane well is increased again, and coalbed methane is collected; S5: End the coalbed methane and coal gas collection, and perform gasification combustion on each coalbed methane well one by one, and the coal gas obtained by combustion is output from the corresponding coalbed methane well.

2. The method for coordinated exploitation of deep coalbed methane and underground coal gasification according to claim 1, characterized in that: In step S1, two parallel coalbed methane wells are drilled, and the two coalbed methane wells are separated by a safe distance so that the production well can be located between the two coalbed methane wells.

3. The method for coordinated exploitation of deep coalbed methane and underground coal gasification according to claim 2, characterized in that: When the gas production of the coalbed methane well reaches the end stage, the gas production of the coalbed methane well is suspended; a number of parallel production wells are drilled between two coalbed methane wells, and the horizontal well 1 is parallel to the horizontal well 2; Casing completion is performed in the production well, and perforation is performed on the second horizontal well to connect the second horizontal well with the external reservoir environment.

4. The method for coordinated exploitation of deep coalbed methane and underground coal gasification according to claim 1, characterized in that: In step S3, the injection well includes a longitudinal well section from the ground downward and a horizontal well three in the horizontal direction; At least one extended well section is respectively provided at the position of horizontal well 3 corresponding to horizontal well 2 and horizontal well 1, one end of the extended well section is connected to horizontal well 3, and the other end points to the upper side or the lower side of horizontal well 3; Casing completion is carried out in the injection well, and perforations are performed on the side walls of horizontal well three at positions corresponding to horizontal well two and horizontal well one, respectively, to connect horizontal well three with the external reservoir environment. The perforations of horizontal well three are concentrated on the half-circle side walls facing horizontal well two or horizontal well one, so that the gasification agent is output toward the production well or coalbed methane well.

5. The method for coordinated exploitation of deep coalbed methane and underground coal gasification according to claim 4, characterized in that: The extended well section is kept in an open hole state without casing completion. When the horizontal well three is completed, an expandable packer is used to temporarily block one end of the extended well section connected to the horizontal well three to prevent concrete from entering the extended well section.

6. The method for coordinated exploitation of deep coalbed methane and underground coal gasification according to claim 1, characterized in that: At least one gas pipe is sleeved inside the coiled tubing for inputting gasifying agent; In horizontal well three, the relative positions of the coiled tubing and the gas pipe are fixed, and the gas pipes are provided with connecting pipes at positions corresponding to horizontal wells one and two. The coiled tubings are provided with openable and closable gas outlets at positions corresponding to horizontal wells one and two. The connecting pipes are connected to the corresponding gas outlets to form targeted gasification agent output.

7. The method for coordinated exploitation of deep coalbed methane and underground coal gasification according to claim 6, characterized in that: A plurality of pairs of openable and closable gas blocking components are provided on the outer side wall of the coiled tubing, and a pair of gas blocking components are respectively provided on both sides of a gas outlet along the length direction of the horizontal well 3; A number of gas blocking components are arranged on the inner wall of the horizontal well three. The gas blocking components correspond to the gas blocking components one by one, and together they form a circle of baffles, which are arranged between the coiled tubing and the horizontal well three to block the gasifying agent output from the gas outlet near the gas outlet, and try to avoid the gasifying agent from diffusing along the horizontal well three, but output it from the perforation holes corresponding to the gas outlet.

8. The method for coordinated exploitation of deep coalbed methane and underground coal gasification according to claim 7, characterized in that: The air blocking assembly includes a fixing ring and a plurality of air blocking sheets. The fixing ring surrounds the outer wall of the coiled tubing and points to the inner wall of the horizontal well along the radial direction of the coiled tubing. The air blocking sheets are evenly distributed along the circumference of the coiled tubing. The tail of the air blocking sheet is hinged to the side of the fixing ring facing the wellhead of the injection well. The air blocking sheet is a straight plate, and the width of the head of the air blocking sheet is smaller than the width of the tail. There is a gap between two adjacent air blocking sheets, so that the air blocking sub-sheet of the air blocking sub-piece can be arranged between the two blocking sheets to form a complete annular plane. The folded state of the air blocking sheet is that the air blocking sheet is close to the outer wall of the coiled tubing and is arranged in the same direction as the coiled tubing; the unfolded state of the air blocking sheet is that the air blocking sheet is rotated to a vertical state and close to the side of the fixing ring.

9. The method for coordinated exploitation of deep coalbed methane and underground coal gasification according to claim 7, characterized in that: The air blocking sub-component comprises a fixed sub-ring and a plurality of air blocking sub-sheets, the fixed sub-ring surrounds the inner wall of the horizontal well three, and the fixed sub-ring points to the coiled tubing along the radial direction of the horizontal well three; the air blocking sub-sheets are evenly distributed along the circumference of the horizontal well three, the tail of the air blocking sub-sheet is hinged to the side of the fixed sub-ring facing the wellhead of the injection well, the air blocking sub-sheet is a straight plate, and the width of the head of the air blocking sub-sheet is smaller than the width of the tail; there is a gap between two adjacent air blocking sub-sheets, so that the air blocking sheet can be arranged between the two air blocking sub-sheets to form a complete annular plane; The folded state of the air-blocking sub-piece is that the air-blocking sub-piece is close to the inner wall of the horizontal well three and is arranged in the same direction as the horizontal well three; the unfolded state of the air-blocking sub-piece is that the air-blocking sub-piece is rotated to a vertical state and is close to the side of the fixed sub-ring.

10. The method for coordinated exploitation of deep coalbed methane and underground coal gasification according to claim 1, characterized in that: In step S4, starting from a production well close to a coalbed methane well, gasification and combustion are performed on each production well one by one in the direction close to another coalbed methane well, and only one production well is targeted at each time; during gasification, the gas blocking components and gas blocking subcomponents on both sides of the corresponding gas outlet are opened, and then the corresponding gas outlet is opened to release the gasifying agent and ignite it. The gasifying agent diffuses from the perforated holes to the reservoir and the extended well section, and burns the coal. The extended well section becomes the initial gasification chamber, which is conducive to the expansion of heat to various parts of the reservoir thickness. The gasification chamber as a whole advances toward the corresponding production well, and the generated coal gas is discharged from the production well.

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