CN109209474B - Method for extracting gas and accumulated water from coal seam and upper multi-goaf by double branch well - Google Patents
Method for extracting gas and accumulated water from coal seam and upper multi-goaf by double branch well Download PDFInfo
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Abstract
The invention belongs to the field of goaf accumulated water and gas extraction and utilization, and particularly relates to a method for extracting and taking off coal seams and gas and accumulated water in upper multi-goafs by a double-branch well, which solves the problem that the existing coal seam goaf gas and accumulated water are lack of mature process for simultaneous extraction. And accumulated water formed in the goaf is utilized while gas resources are extracted, so that potential threats to the mining of the lower coal seam caused by the accumulated water in the upper goaf are eliminated. And gas in the lower coal seam is pre-pumped, so that the gas concentration and the gas pressure during the exploitation of the lower coal seam are effectively reduced. The production target of safety, high efficiency and maximum resource utilization is realized, a large amount of economic benefits can be generated, and the method has great popularization value.
Description
Technical Field
The invention belongs to the field of goaf accumulated water and gas extraction and utilization, and particularly relates to a method for extracting gas and accumulated water from a lower coal seam and a plurality of goafs on the upper part by using a double-branch well.
Background
With the popularization and application of the comprehensive mechanized coal mining method, the goaf generated by the coal field mining in China rapidly grows, and the goaf is gradually regular and smooth to be clustered. The relatively regular distribution form creates convenient conditions for collecting and utilizing accumulated water and gas in the goaf in a large scale. 70% of goafs in China are high gas goafs, the storage amount of gas left inside is up to 2100 billions of cubic meters, and accumulated water exists in most goafs to different degrees, and the accumulated water amount is huge and constitutes a huge potential threat for exploiting lower coal seams. According to the statistics of coal mine water damage accidents published by the State administration of safety supervision, more than 80% of water damage accidents encountered in coal mines in China in recent years are caused by water accumulation in goafs, economic losses caused by water accumulation and water permeation accidents in the goafs are the first of all accidents, and casualties caused by the accidents are only second to gas accidents. If the gas and water resources with rich storage capacity in the goaf can be extracted and utilized, the goaf resources can be changed into valuables to be utilized to the maximum extent, and the potential threat of accumulated water in the goaf to the mining of a lower coal seam can be thoroughly eliminated, so that the effective overall extraction of the accumulated water and the gas in the goaf is significant to the current coal mining.
The common treatment measures for accumulated water and gas in the goaf are generally that the gas is extracted and utilized from a ground vertical drilling well to a fracture zone above the goaf, and the accumulated water in the goaf is drained by adopting a technical means of advanced exploration and drainage in roadway tunneling or working face stoping. The two measures are separately and independently carried out, and the accumulated water in the goaf is rarely recycled after detection and discharge and is directly discharged to the outside of the well according to industrial wastewater. Due to the adoption of the treatment mode, the drilling needs to be independently carried out aiming at the gas and the accumulated water in the goaf in the construction process, and a large amount of mechanical equipment and human resources are occupied. Particularly, a good recycling system is not formed for the extraction and utilization of water resources in the goaf. The actual situation that a large amount of accumulated water and gas exist in the goaf simultaneously requires that the optimal exploitation and utilization of resources can be realized only by considering both the accumulated water and the gas in the goaf, and the water pumping and the gas mining in the goaf are carried out simultaneously. Therefore, the technology for simultaneously extracting and utilizing the gas and the water resource in the goaf has important significance.
Disclosure of Invention
The invention provides a method for extracting gas and accumulated water from a lower coal seam and a plurality of goafs on the upper part by using a double-branch well, aiming at solving the problem that the existing technology for extracting gas and accumulated water simultaneously in a coal seam goaf is lack of a mature technology.
The invention is realized by the following technical scheme: a method for extracting gas and accumulated water from a lower coal seam and a plurality of upper goafs by a double-branch well comprises the following steps:
s1, according to design specifications and a mining engineering plan of a raw mine of a abandoned mine, a goaf group boundary is defined by an upper and lower comparison map of a mine in a mining area, three extraction well construction points A, B and C which are positioned on the same straight line are selected in a terrain flat area which is 10-20 m away from the goaf group boundary and along the advancing direction of an original working face, sewage treatment plants are arranged in the middles of the points A and B, gas collecting devices are arranged in the middles of the points B and C, and extraction well horizontal sections L above a top plate of a goaf are respectively determined according to a coal-series stratum comprehensive bar chart, a coal bed bottom plate contour diagram, a mine geological profile and goaf top plate lithology1And a horizontal section L of the extraction well below the bottom plate of the goaf2；
S2, erecting drilling equipment at a ground point A, and constructing a vertical section of the extraction well A vertically downwards from the ground surface until the vertical section of the extraction well A reaches a depth H1Time-making oblique section X1Construction, the drilling machine equipment passes through the deflecting section X1Can be smoothly adjusted to the horizontal section L of the extraction well1Construction of extraction well horizontal section L1Can span a plurality of goafs and extract the horizontal section L of the well1After the construction is finished, withdrawing the drill bit, adjusting the drilling direction of the extraction well A to be vertical and downward, and then continuing the construction of the vertical section of the extraction well A until the depth H is reached2Further carrying out a deflecting section X2After the construction is finished, the horizontal section L of the extraction well is carried out2Construction of the same extraction well horizontal section L2Can span a plurality of goafs;
s3, disassembling the drilling machine equipment, moving the drilling machine equipment to a ground point B, repeating the step S2 to perform construction of the extraction well B, and meanwhile laying a sleeve on the whole shaft of the extraction well A, wherein the vertical section and the deflecting section of the extraction well A adopt seamless steel pipes, and the horizontal section L of the extraction well is1And extraction well horizontal section L2The sleeve adopts a combined structure of a seamless steel pipe and a porous metal pipe;
s4, reinforcing the extraction well A and the pore channel after the casing of the extraction well A is laid, sealing the casing and the pore wall gap, and connecting the casing and the pore wall gap with a ground extraction pipeline, wherein the pipeline is respectively provided with a main valve and a water-gas separation device from bottom to top, the water-gas separation device is connected with a water pumping pipeline and a gas collecting pipeline, the water pumping pipeline is connected with a sewage treatment plant, the gas collecting pipeline is connected with a ground gas collecting device, the water pumping pipeline is provided with a valve B and a water flow monitoring meter, and the gas collecting pipeline is provided with a valve A and a gas monitoring meter;
s5, after the pipeline equipment of the extraction well A is connected, opening a main valve and a valve B on a water pumping pipeline, performing water pumping operation on the extraction well A for 8-10 hours, further opening a valve A on a gas collection pipeline to collect gas, monitoring the gas concentration through a gas monitoring table in the extraction process, closing the gas extraction valve A and keeping continuous water pumping of the extraction well A when the gas concentration is lower than 30% in the extraction process, and re-extracting the gas after the gas concentration is higher than 30% in 36-72 hours;
s6, after the construction of the extraction well B is completed, the steps S3, S4 and S5 are repeated to extract the gas and the accumulated water of the extraction well B, and the step S2 is synchronously repeated to construct the extraction well C;
and S7, after the construction of the extraction well C is finished, repeating the steps S3, S4 and S5 to perform the extraction operation of the gas and the accumulated water of the extraction well C.
The extraction well A, the extraction well B and the extraction well C are located on the same straight line and are arranged at equal intervals, and the adjacent intervals are 200-350 m.
Horizontal segment L of extraction well1The pumping well horizontal section L is arranged in the range of 4-9 m above a goaf top plate2The pumping well horizontal segment L is arranged in the range of 5-10 m below a goaf bottom plate1And extraction well horizontal section L2The length of (2) is 600-1000 m.
The diameter of the extraction well A is 200mm, and an inclined section X is formed1And deflecting segment X2The turning radius of the steel plate is 10-30 m.
Horizontal segment L of extraction well1And extraction well horizontal section L2A section of the porous metal pipe in the sleeve is arranged every 5-10 m, preferably 5m, so that the extraction effect is improved to the maximum extent.
The main valve is arranged on an extraction pipeline 1.3-1.6 m higher than the ground surface, and the water-gas separation device is arranged on the extraction pipeline 2-3 m higher than the ground surface.
Compared with the prior art, the invention has the advantages and beneficial effects that:
based on modern high-strength intensive mining conditions, the invention can quickly generate a large amount of regular and flat goafs with the propulsion length exceeding 1000m on the upper part, and meanwhile, the coal seam on the lower part contains a large amount of gas. Through construction of the double branch well, accumulated water and gas in the upper goaf and partial gas in the lower coal seam are simultaneously adopted, extraction and drilling are efficiently utilized, and one well can be used for multiple purposes. And accumulated water formed in the goaf is utilized while gas resources are extracted, so that potential threats to the mining of the lower coal seam caused by the accumulated water in the upper goaf are eliminated. And gas in the lower coal seam is pre-pumped, so that the gas concentration and the gas pressure during the exploitation of the lower coal seam are effectively reduced. The production target of safety, high efficiency and maximum resource utilization is realized, a large amount of economic benefits can be generated, and the method has great popularization value.
Drawings
FIG. 1 is a schematic view of the cross-sectional structure of an extraction process of the present invention;
FIG. 2 is an enlarged schematic view of a portion of the structure of FIG. 1;
FIG. 3 is a schematic top view of the extraction pipeline of the present invention.
In the figure: 1-sewage treatment plant, 2-water pumping pipeline, 3-water flow monitoring meter, 4-valve B, 5-gas monitoring meter, 6-valve A, 7-gas collecting pipeline, 8-gas collecting device, 9-water-gas separating device, 10-main valve and 11-depth H112-deflecting segment X113-depth H214-deflecting section X215-porous metal pipe, 16-extraction well horizontal section L117-extraction well horizontal segment L218-coal seam, 19-goaf, 20-extraction well A, 21-extraction well B, 22-extraction well C.
Detailed Description
The invention is further explained by referring to fig. 1-3, a method for extracting gas and accumulated water from a lower coal seam and a multi-goaf on the upper part by a double-branch well comprises the following steps:
s1, according to abandoned mineDesigning specifications of a raw mine well and a plane drawing of an excavation project, delineating a gob 19 group boundary by an upper and lower comparison drawing of a mine area well, selecting three extraction well construction points A, B and C which are positioned on the same straight line in a terrain flat area along the advancing direction of an original working face at a position 10-20 m away from the gob 19 group boundary, arranging sewage treatment plants 1 in the middles of the points A and B, arranging gas collecting devices 8 in the middles of the points B and C, and respectively determining an extraction well horizontal section L above a top plate of a gob 19 according to a coal-series stratum comprehensive histogram, a coal bed floor contour map, a mine geological profile and a gob 19 top floor lithology1Horizontal section L of extraction well below the floor of gob 19 and 16217; s2, erecting drilling equipment at a ground point A, and constructing a vertical section of the extraction well A20 vertically and downwards from the ground surface, wherein when the vertical section of the extraction well A20 reaches the depth H1Making oblique section X at 11 hours 112 construction, making the drilling machine pass through the deflecting section X 112 can be smoothly adjusted to the horizontal section L of the extraction well116, constructing an extraction well horizontal section L 116 may span multiple goafs, extraction well horizontal segments L1After 16 constructions are finished, withdrawing the drill bit, adjusting the drilling direction of the extraction well A20 to be vertical downward, and continuing the construction of the vertical section of the extraction well A20 until the depth H is reached213, further carrying out a deflecting section X 214, performing construction, and performing extraction well horizontal section L after the construction is finished217, constructing the horizontal section L of the extraction well in the same way2S3, disassembling the drilling machine equipment, moving the drilling machine equipment to a ground point B, repeating the step S2 to construct an extraction well B21, and meanwhile laying a sleeve on the whole shaft of the extraction well A20, wherein the vertical section and the deflecting section of the extraction well A20 are made of seamless steel pipes, and the horizontal section L of the extraction well is made of seamless steel pipes 116 and extraction well horizontal section L2The 17 sleeve adopts a combined structure of a seamless steel pipe and a porous metal pipe 15; s4, reinforcing the extraction well A20 and the pore channel after the casing of the extraction well A20 is laid, sealing the gap between the casing and the pore wall, and connecting the casing and the ground extraction pipeline, wherein the pipeline is respectively provided with a main valve 10 and a water-gas separation device 9 from bottom to top, the water-gas separation device 9 is respectively connected with a water pumping pipeline 2 and a gas collecting pipeline 7, the water pumping pipeline 2 is connected with a sewage treatment plant 1, and the gas collecting pipeline 7 is connected with a gas collection device8, a valve B4 and a water flow monitoring meter 3 are arranged on the water pumping pipeline 2, and a valve A6 and a gas monitoring meter 5 are arranged on the gas collection pipeline 7; s5, after the pipeline equipment of the extraction well A20 is connected, opening a main valve 10 and a valve B4 on a water pumping pipeline 2, performing water pumping operation on the extraction well A20 for 8-10 hours, further opening a valve A6 on a gas collection pipeline 7 to collect gas, monitoring the gas concentration through a gas monitoring table 5 in the extraction process, closing the gas extraction valve A6 and keeping continuous water pumping of the extraction well A20 after the gas concentration is lower than 30% in the extraction process, and re-extracting the gas after the gas concentration is higher than 30% in 36-72 hours; s6, after the construction of the extraction well B21 is completed, the steps S3, S4 and S5 are repeated to extract gas and accumulated water of the extraction well B21, and the step S2 is synchronously repeated to construct the extraction well C22; and S7, after the construction of the extraction well C22 is completed, repeating the steps S3, S4 and S5 to perform extraction operation on gas and accumulated water of the extraction well C22.
The extraction well A20, the extraction well B21 and the extraction well C22 are located on the same straight line and are arranged at equal intervals, the adjacent intervals are 200-350 m, and the horizontal section L of the extraction well116 are arranged in the range of 4-9 m above the top plate of the goaf 19, and the horizontal section L of the extraction well217 is arranged in the range of 5-10 m below the bottom plate of the goaf 19, and the horizontal section L of the extraction well116 and extraction well horizontal section L 217 is 600-1000 m in length. The diameter of the extraction well A20 is 200mm, and the deflecting section X is112 and deflecting section X 214, the turning radius is 10-30 m, and the horizontal section L of the extraction well116 and extraction well horizontal section L 217 the porous metal pipes 15 in the casing are arranged in sections at intervals of 5-10 m, preferably 5m, so that the extraction effect is improved to the maximum extent. The main valve 10 is arranged on an extraction pipeline 1.3-1.6 m higher than the ground surface, and the water-gas separation device 9 is arranged on the extraction pipeline 2-3 m higher than the ground surface.
The method of the present invention will be described with reference to a certain mine from Shanxi Jincheng. The mine is used for mining No. 2, No. 3 and No. 6 coal beds. The coal mining method is a comprehensive mechanical strike long wall type, the dip angle of a coal seam is averagely less than 8 degrees, and the mine mining area is prepared with a roadway panel type single-layer arrangement. After the stoping of the overlying No. 2 coal seam is finished, the average advancing length of the stoped working face of the No. 2 coal seam is 2000m, the thickness of the coal seam is 1.5-2.4 m, the average thickness of the coal seam is 1.9 m, and the No. 2 coal is high-quality anthracite, so that a large amount of gas resources are expected to be left in the mined-out area of the No. 2 coal seam. The thickness of the overlying surface soil layer of the No. 2 coal seam is 180-420 m, the average thickness is 300m, no river passes through the ground surface of the mining area, hydrogeological data and field geophysical prospecting data show that a large amount of accumulated water exists in the mined-out area of the No. 2 coal seam. And preparing to mine the No. 3 coal seam in the second mining area of the existing mine, wherein the distance between the No. 3 coal seam and the No. 2 coal seam is about 3m according to the geological data of the mine, and the mining of the No. 3 coal seam is seriously threatened by the accumulated water in the goaf in the No. 2 coal seam. In order to satisfactorily solve the problem of cooperative exploitation of gas resources, the invention provides the following specific steps:
according to the design specification and the mining engineering plan of the original mine of the abandoned mine, a goaf 19 group boundary is defined by an up-down comparison graph of a mine area well, the goaf 19 is positioned above a lower coal seam 18, three extraction well construction points A, B and C are selected in a terrain flat area along the advancing direction of an original working face at the position 15m away from the goaf 19 group boundary, the intervals of the points A, B and C are 300m, and the points A, B and C are linearly arranged along the advancing direction of the working face, sewage treatment plants 1 are arranged in the middle of the points A and B, gas collection devices 8 are arranged in the middle of the points B and C, and the extraction well horizontal section L above the top plate of the goaf 19 is respectively determined according to a coal system stratum comprehensive histogram, a coal seam bottom plate contour map, a mine geological section map and the lithology of the top plate of the goaf 191Horizontal section L of extraction well below the floor of gob 19 and 16217；
Erecting drilling equipment at a ground point A, and constructing a vertical section of an extraction well A20 vertically downwards from the ground surface, wherein the diameter of the extraction well A20 is 200mm, and when the vertical section of the extraction well A20 reaches the depth H1Making oblique section X at 11 hours 112 construction, deflecting section X 112 radius of turning 12m, making the drilling equipment pass through the deflecting segment X 112 can be smoothly adjusted to the horizontal section L of the extraction well116, constructing an extraction well horizontal section L 116 length is 1000m, and the horizontal section of the extraction well is L 116 may span multiple goafs, extraction well horizontal segments L1After 16 constructions are finished, withdrawing the drill bit, adjusting the drilling direction of the extraction well A20 to be vertical downward, and continuing the construction of the vertical section of the extraction well A20 until the depth H is reached213Further carrying out a deflecting section X 214, performing construction, and performing extraction well horizontal section L after the construction is finished217, constructing the horizontal section L of the extraction well in the same way 217 may span multiple goafs, extraction well horizontal segments L 217 has a length of 1000m and a deflecting segment X 214, the turning radius is 12m, the drilling machine equipment is disassembled, the drilling machine equipment is moved to a ground point B, the step S2 is repeated to conduct construction of an extraction well B21, meanwhile, a sleeve is laid on the whole shaft of the extraction well A20, the vertical section and the deflecting section of the extraction well A20 are made of seamless steel pipes, and the horizontal section L of the extraction well is made of seamless steel pipes 116 and extraction well horizontal section L2The 17 sleeve adopts a combined structure of a seamless steel pipe and a porous metal pipe 15, and the diameter of the sleeve is 180 mm;
the method comprises the steps of reinforcing an extraction well A20 and a pore passage after the laying of a sleeve of an extraction well A20 is finished, sealing the sleeve and a pore wall gap, and then connecting the sleeve with a ground extraction pipeline, wherein a main valve 10 and a water-gas separation device 9 are respectively arranged on the pipeline from bottom to top, the pipeline is respectively connected with a water pumping pipeline 2 and a gas collecting pipeline 7 after passing through the water-gas separation device 9, the water pumping pipeline 2 is connected with a sewage treatment plant 1, the gas collecting pipeline 7 is connected with a gas collecting device 8, a valve B4 and a water flow monitoring meter 3 are arranged on the water pumping pipeline 2, and a valve A6 and a gas monitoring meter 5 are arranged.
Further, after the pipeline equipment of the extraction well A20 is connected, opening the main valve 10 and a valve B4 on the water pumping pipeline 2, performing water pumping operation on the extraction well A20 for 8-10 hours, further opening a valve A6 on the gas collection pipeline 7 for collecting gas, monitoring the gas concentration through a gas monitoring table 5 in the extraction process, closing the gas production valve A6 and keeping continuous water pumping of the extraction well A20 after the gas concentration is lower than 30% in the extraction process, and re-extracting the gas after the gas concentration is higher than 30% in 36-72 hours; and after the construction of the extraction well B21 is completed, the steps are repeated to perform extraction work on gas and accumulated water in the extraction well B21, the construction of the extraction well C22 is synchronously performed, and after the construction of the extraction well C22 is completed, the steps S3, S4 and S5 are repeated to perform extraction work on the gas and the accumulated water in the extraction well C22.
Claims (6)
1. A method for extracting gas and accumulated water from a coal seam and a plurality of goafs on the upper part of the coal seam by a double-branch well is characterized by comprising the following steps:
s1, according to the design specification and the mining engineering plan of the original mine of the abandoned mine, the group boundary of a goaf (19) is defined by an up-down comparison map of the mine, three extraction well construction points A, B and C which are positioned on the same straight line are selected in a terrain flat area which is 10-20 m away from the group boundary of the goaf (19) and along the advancing direction of an original working face, sewage treatment plants (1) are arranged in the middles of the points A and B, gas collection devices (8) are arranged in the middles of the points B and C, and the horizontal section L of the extraction well above the top plate of the goaf (19) is respectively determined according to a coal-series stratum comprehensive column diagram, a coal bed bottom plate contour diagram, a mine geological profile diagram and the lithology of the top plate and the bottom plate of the goaf (19)1(16) And a horizontal section L of the extraction well below the bottom plate of the goaf (19)2（17）；
S2, erecting drilling equipment at a ground point A, and constructing a vertical section of the extraction well A (20) vertically downwards from the ground surface until the vertical section of the extraction well A (20) reaches a depth H1(11) Time-making oblique section X1(12) Construction, the drilling machine equipment passes through the deflecting section X1(12) Can be smoothly adjusted to the horizontal section L of the extraction well1(16) Construction of extraction well horizontal section L1(16) Can span a plurality of goafs and extract the horizontal section L of the well1(16) After the construction is finished, withdrawing the drill bit, adjusting the drilling direction of the extraction well A (20) to be vertical downward, and then continuing the construction of the vertical section of the extraction well A (20) until the depth H is reached2(13) Further carrying out a deflecting section X2(14) After the construction is finished, the horizontal section L of the extraction well is carried out2(17) Construction of the same extraction well horizontal section L2(17) Can span multiple goafs;
s3, disassembling the drilling machine equipment, moving the drilling machine equipment to a ground point B, repeating the step S2 to construct the extraction well B (21), and meanwhile laying a sleeve on the whole shaft of the extraction well A (20), wherein the vertical section and the deflecting section of the extraction well A (20) adopt seamless steel pipes, and the horizontal section L of the extraction well is1(16) And extraction well horizontal section L2(17) The sleeve adopts seamlessThe steel pipe and the porous metal pipe (15) are combined;
s4, reinforcing the extraction well A (20) and a pore passage after the casing of the extraction well A (20) is laid, sealing the casing and a pore wall gap, and then connecting the casing and a ground extraction pipeline, wherein the pipeline is provided with a main valve (10) and a water-gas separation device (9) from bottom to top, the water-gas separation device (9) is connected with a water pumping pipeline (2) and a gas collecting pipeline (7), the water pumping pipeline (2) is connected with a sewage treatment plant (1), the gas collecting pipeline (7) is connected with a gas collecting device (8), a valve B (4) and a water flow monitoring meter (3) are arranged on the water pumping pipeline (2), and a valve A (6) and a gas monitoring meter (5) are arranged on the gas collecting pipeline (7);
s5, after the pipeline equipment of the extraction well A (20) is connected, opening a main valve (10) and a valve B (4) on a water pumping pipeline (2), performing water pumping operation on the extraction well A (20) for 8-10 hours, further opening a valve A (6) on a gas collection pipeline (7) to collect gas, monitoring the gas concentration through a gas monitoring table (5) in the extraction process, closing the gas extraction valve A (6) and keeping continuous water pumping of the extraction well A (20) when the gas concentration is lower than 30% in the extraction process, and re-extracting the gas after the gas concentration is higher than 30% in 36-72 hours;
s6, after the construction of the extraction well B (21) is completed, the steps S3, S4 and S5 are repeated to extract gas and accumulated water of the extraction well B (21), and the step S2 is synchronously repeated to construct the extraction well C (22);
and S7, after the construction of the extraction well C (22) is finished, repeating the steps S3, S4 and S5 to perform extraction operation on gas and accumulated water of the extraction well C (22).
2. The method of claim 1, wherein the method comprises the following steps: the extraction well A (20), the extraction well B (21) and the extraction well C (22) are located on the same straight line and are arranged at equal intervals, and the adjacent intervals are 200-350 m.
3. The method for extracting gas and accumulated water from the lower coal seam and the upper multi-goaf by the double-branch well as the coal seam and the upper multi-goaf according to claim 2, wherein the horizontal section L of the extraction well1(16) Is arranged in the range of 4-9 m above the top plate of the goaf (19) and is used for extracting a horizontal section L of the well2(17) Is arranged in the range of 5-10 m below the bottom plate of the goaf (19) and is used for extracting a horizontal section L of the well1(16) And extraction well horizontal section L2(17) The length of (2) is 600-1000 m.
4. The method of claim 3, wherein the method comprises the following steps: the diameter of the extraction well A (20) is 200mm, and an inclined section X is formed1(12) And deflecting segment X2(14) The turning radius of the steel plate is 10-30 m.
5. The method for extracting gas and accumulated water from the lower coal seam and the upper multi-goaf by the double-branch well as claimed in claim 3, wherein the horizontal section L of the extraction well1(16) And extraction well horizontal section L2(17) The porous metal pipes (15) in the sleeve are arranged in sections at intervals of 5-10 m.
6. The method of claim 1, wherein the method comprises the following steps: the main valve (10) is arranged on an extraction pipeline 1.3-1.6 m higher than the ground surface, and the water-gas separation device (9) is arranged on the extraction pipeline 2-3 m higher than the ground surface.
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