CN115478830B - Low permeability coal seam permeability increasing method - Google Patents
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- CN115478830B CN115478830B CN202211367031.1A CN202211367031A CN115478830B CN 115478830 B CN115478830 B CN 115478830B CN 202211367031 A CN202211367031 A CN 202211367031A CN 115478830 B CN115478830 B CN 115478830B
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- 239000003245 coal Substances 0.000 title claims abstract description 144
- 230000035699 permeability Effects 0.000 title claims abstract description 28
- 238000000034 method Methods 0.000 title claims abstract description 20
- 230000001965 increasing effect Effects 0.000 title claims abstract description 13
- 238000005553 drilling Methods 0.000 claims abstract description 184
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 66
- 238000002485 combustion reaction Methods 0.000 claims abstract description 53
- 239000007788 liquid Substances 0.000 claims abstract description 31
- 238000004891 communication Methods 0.000 claims abstract description 28
- 238000004880 explosion Methods 0.000 claims abstract description 11
- 239000000203 mixture Substances 0.000 claims abstract description 10
- 238000005336 cracking Methods 0.000 claims abstract description 5
- 238000000605 extraction Methods 0.000 claims description 16
- 238000012544 monitoring process Methods 0.000 claims description 5
- 230000001737 promoting effect Effects 0.000 claims description 5
- 238000001028 reflection method Methods 0.000 claims description 4
- 238000005422 blasting Methods 0.000 claims description 3
- 230000000694 effects Effects 0.000 abstract description 6
- 239000007789 gas Substances 0.000 description 19
- 239000012530 fluid Substances 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 4
- 239000003034 coal gas Substances 0.000 description 4
- 238000002347 injection Methods 0.000 description 4
- 239000007924 injection Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000003116 impacting effect Effects 0.000 description 3
- 239000011435 rock Substances 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 239000002360 explosive Substances 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000010276 construction Methods 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/263—Methods for stimulating production by forming crevices or fractures using explosives
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
- E21B7/04—Directional drilling
- E21B7/046—Directional drilling horizontal drilling
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Abstract
The invention provides a low permeability coal seam permeability increasing method, which comprises the steps of sequentially drilling horizontal drilling holes from the bottom of a roadway to the upper part of the roadway, and drilling a plurality of groups of vertical drilling holes and lateral drilling holes in the formed horizontal drilling holes along the vertical direction upwards and the horizontal direction vertical to the horizontal drilling holes; drilling a top plate horizontal well in the lower part of the top plate; corresponding vertical communication holes are drilled upwards in each horizontal drilling hole on the uppermost layer, so that the vertical communication holes are communicated with the horizontal drilling holes on the uppermost layer and the horizontal section of the horizontal well on the top plate; plugging a horizontal drilling hole in a coal seam, and then adding a liquid combustion improver; pre-extracting methane in the coal bed, closing a ground wellhead after the concentration of extracted methane exceeds 80%, and igniting and detonating a methane-combustion improver mixture in a complex drilling network of the coal bed; and the combustion improver is continuously thrown and the explosion and cracking operation is continuously carried out in the coal seam, so that the continuous expansion and extension of cracks around the complex drilling network are promoted. The method is simple to operate, low in implementation cost and remarkable in permeability improvement effect on the coal seam.
Description
Technical Field
The invention belongs to the technical field of coal safety exploitation and gas development, and particularly relates to a low permeability coal seam permeability increasing method.
Background
The coal is produced and consumed in China, more than 50% of coal beds are high-gas coal beds, and the coal beds are seriously affected by coal and gas outburst accidents. With the increase of the mining depth, the coal and gas outburst risks are increasing. The coal gas is a gas mixture mainly comprising methane, which not only causes hidden danger of coal mine safety production, but also is an important clean energy source, and belongs to typical unconventional natural gas, so that the effective extraction of the gas is not only a key measure for preventing the outburst of coal and gas, but also an important technical link for realizing the recycling of the gas. The coal seam in China has the characteristics of high gas pressure, strong gas adsorptivity, low coal seam permeability and the like, so that a fracturing and permeability-increasing measure is required to be adopted for the coal seam, the air permeability of the coal seam is increased, and the effective extraction of gas is realized. At present, coal seam permeability improvement mainly adopts a drilling pressure relief method, and the permeability of the coal seam is improved by utilizing a damaged zone formed by stress release around a drilling hole, but the mode has the problems of limited permeability improvement range, small effective gas extraction radius and the like, and particularly has very limited fracturing permeability improvement effect in a soft coal seam with higher argillnesses. Therefore, the existing technological method is required to be upgraded and modified, the existing technological system is changed and innovated, and the anti-reflection method suitable for the low-permeability coal seam is formed, so that the efficient extraction of coal gas is realized, and accidents such as coal and gas outburst and the like in the coal mine production process are eliminated.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention provides the low permeability coal seam permeability increasing method which is simple in operation process, low in implementation cost, remarkable in permeability increasing effect on the coal seam, and capable of improving the gas extraction efficiency.
In order to achieve the above purpose, the invention provides a permeability-increasing method for a low permeability coal seam, which comprises the following steps;
step one: constructing a complex drilling network of the coal seam;
s11, aiming at coal seam areas with rich coal gas and high gas pressure, determining multi-layer drilling positions on the side surfaces in a return air roadway or a transport roadway in a mode parallel to a stope face;
s12, sequentially drilling horizontal drilling holes from the bottom of the roadway to the upper part of the roadway, vertically moving the drilling positions after finishing the next layer of horizontal drilling holes, and then performing the drilling operation of the upper layer of horizontal drilling holes;
s13, in the formed horizontal drilling holes, drilling a plurality of groups of vertical drilling holes and lateral drilling holes along the length direction of the horizontal drilling holes in a vertical upward direction and the horizontal direction perpendicular to the horizontal drilling holes in a hydraulic jet sidetracking mode, communicating the upper layer of adjacent horizontal drilling holes and the lower layer of adjacent horizontal drilling holes by using the vertical drilling holes, and communicating the same layer of adjacent horizontal drilling holes by using the lateral drilling holes; in the process, stress released in the drilling operation process is used for acting on the coal bed around the drilling hole, so that the coal bed is deformed and broken to form a drilling crack zone, and a complex drilling network consisting of horizontal drilling holes, vertical drilling holes and lateral drilling holes is formed in the coal bed;
step two: drilling a top plate horizontal well on the ground;
drilling a top plate horizontal well at the lower part of the top plate by adopting a ground drilling mode, and enabling the horizontal section of the top plate horizontal well to be parallel to the coal seam;
step three: a roof horizontal well and a complex drilling network of the coal seam are communicated;
after the roof horizontal well is drilled, corresponding vertical communication holes are drilled upwards in each horizontal drilling hole at the uppermost layer in a hydraulic jet sidetrack drilling mode, so that the vertical communication holes are communicated with the horizontal drilling holes at the uppermost layer and the horizontal section of the roof horizontal well, and complex well pattern channels formed by the complex drilling network, the vertical communication holes and the roof horizontal well are mutually communicated in the coal seam and the roof;
step four: adding a liquid combustion improver;
plugging a horizontal drilling hole in a coal bed in a downhole transportation roadway or a return air roadway, then throwing a liquid combustion improver into the coal bed from the ground through a roof horizontal well, enabling the liquid combustion improver to enter the coal bed through the roof horizontal well and a vertical communication hole, enabling the liquid combustion improver to flow into each region of the coal bed through horizontal drilling holes, vertical drilling holes and lateral drilling holes in the coal bed, and enabling part of the liquid combustion improver to enter the coal bed through cracks around the drilling holes;
step five: cracking by burning and explosion;
pre-extracting methane in a coal bed through a roof horizontal well, monitoring the methane concentration in real time, closing a ground wellhead of the roof horizontal well after the extracted methane concentration exceeds 80%, then performing electric shock ignition on a methane-combustion improver mixture in a complex drilling network of the coal bed, igniting the methane-combustion improver mixture in the complex drilling network of the coal bed, impacting the coal bed by utilizing high air pressure generated in the combustion explosion process of the methane and the combustion improver, promoting the coal bed around the complex drilling network to form large-scale cracks, and further communicating crack zones around the complex drilling network due to stress release;
step six: constructing a multi-scale methane extraction system;
repeating the steps four and five for a plurality of times, continuously carrying out combustion improver throwing and blasting cracking operation in the coal bed, promoting continuous expansion and extension of cracks around the complex drilling network, further increasing the complexity and the extension distance of the cracks, and finally forming the natural cracks, large-scale cracks, complex drilling network of the coal bed, vertical communication holes and top plate horizontal well multi-scale methane extraction system in the coal bed.
Further, in order to more fully monitor the extraction process, in step five, the methane concentration is monitored while the methane components are also monitored simultaneously.
Preferably, in the first step, the thickness of the coal seam in the coal seam region is not less than 2m.
Further, in order to obtain a better anti-reflection effect, in step S11, it is ensured that the heights of the drilling positions of different layers from the bottom of the roadway are different.
In the invention, firstly, a plurality of layers of horizontal drilling holes are drilled in a coal seam area, the upper layer of adjacent horizontal drilling holes and the lower layer of adjacent horizontal drilling holes are communicated with each other by utilizing vertical drilling holes, and the same layer of adjacent horizontal drilling holes are communicated with each other by utilizing lateral drilling holes, so that a complex drilling network can be formed in the coal seam, and a communication channel inside the coal seam is provided for later coal seam fracturing and permeability increasing; secondly, the area where the top plate is located is selected for drilling the top plate horizontal well, a stable borehole can be formed by utilizing the characteristic of stable structure of the rock stratum where the top plate is located, so that the stability of the main body section of the fluid injection channel can be ensured, and powerful guarantee is provided for the fact that the subsequent liquid combustion improver can be fully injected into each part in the coal seam; then, the vertical communication holes are used for connecting the top plate horizontal well and the uppermost horizontal drilling holes, so that a complex drilling network, vertical drilling holes, vertical communication holes and complex well pattern channels which are communicated with each other are finally formed, the complex well pattern channels can enable all directions of the coal bed to be communicated with each other, the uniformity of crack distribution is greatly enhanced, the range of crack formation is effectively enlarged, the crack formation effect is better, in addition, the well pattern channels can enable all parts of the communication channels inside the coal bed to be fully communicated with the main body section of the fluid injection channel, the fact that the follow-up liquid combustion improver can be fully injected into all areas inside the coal bed is effectively ensured, and the follow-up liquid combustion improver can be further beneficial to enter into cracks inside the coal bed in all areas; then, after the horizontal drilling hole is plugged, the liquid combustion improver is put into the complex well pattern channel through the horizontal well of the top plate, so that the hydraulic combustion improver can be ensured to fully enter each part of the complex well pattern channel, the consumption of the liquid combustion improver is favorably saved, and moreover, the hydraulic combustion improver entering the cracks can also expel part of methane in the cracks into the main body channel, thereby being favorable for improving the gas extraction efficiency; finally, igniting and detonating the methane-combustion improver mixture in the complex drilling network of the coal bed after the liquid combustion improver is put in, and fully utilizing methane in the coal bed to perform in-situ ignition and explosion, so that large-scale cracks can be formed by utilizing high-pressure impact of the explosion to form a crack zone.
Drawings
FIG. 1 is a schematic diagram of the construction of a complex drilling network for coal layers in the invention;
FIG. 2 is a schematic view of the structure of a horizontal well with a ground roof in the present invention;
FIG. 3 is a schematic diagram of a complex drilling network for connecting a roof horizontal well with a coal seam in the present invention;
FIG. 4 is a schematic illustration of the delivery of a liquid oxidizer in accordance with the present invention;
fig. 5 is a schematic diagram of a burst fracturing operation in accordance with the present invention.
In the figure: 1. horizontal drilling, 2, vertical drilling, 3, lateral drilling, 4, a top plate, 5, a top plate horizontal well, 6, a coal seam, 7, vertical communication holes, 8, a liquid combustion improver, 9, a ground wellhead, 10 and a large-scale crack.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
The invention provides a low permeability coal seam anti-reflection method, firstly, a complex drilling network is drilled in a coal seam 6, then a roof horizontal well 5 is drilled in a roof 4 from the ground, and finally a vertical communication hole 7 communicated with the roof horizontal well 5 is drilled upwards in the horizontal drilling 1; and (3) putting a liquid combustion improver 8 into the horizontal well 5 facing the roof, wherein the liquid combustion improver 8 enters the complex drilling network of the coal seam through the horizontal well 5 and is mixed with methane in the complex drilling network of the coal seam to form combustible and explosive multiphase fluid. The method comprises the steps of igniting combustible explosive multiphase fluid in a complex drilling network, causing the inside of the complex drilling network to explode, impacting coal beds around the complex drilling network to form cracks, generating a large-scale stress release area in the coal bed 6, and forming high-conductivity channels which are formed in the coal bed 6 and are formed by the complex drilling network, artificial cracks and natural cracks, so as to realize multidimensional and multi-level permeability improvement of the low-permeability coal bed and achieve the purpose of permeability improvement of the low-permeability coal bed, and specifically comprises the following steps of;
step one: constructing a complex drilling network of the coal seam, as shown in fig. 1 to 4;
s11, aiming at coal seam areas with rich coal gas and high gas pressure, determining multi-layer drilling positions on the side surfaces in a return air roadway or a transport roadway in a mode parallel to a stope face;
s12, sequentially drilling horizontal drilling holes 1 from the bottom of a roadway to the upper part of the roadway, vertically moving the drilling positions after completing a group of horizontal drilling holes 1 on the next layer, and then performing drilling operation on the horizontal drilling holes 1 on the upper layer;
s13, in the formed horizontal drilling holes 1, a plurality of groups of vertical drilling holes 2 and lateral drilling holes 3 are drilled in the vertical direction upwards and the horizontal direction perpendicular to the horizontal drilling holes 1 in a hydraulic jet sidetrack manner along the length direction of the horizontal drilling holes 1, the vertical drilling holes 2 are used for mutually communicating the upper layer of adjacent horizontal drilling holes 1 and the lower layer of adjacent horizontal drilling holes 1, and the lateral drilling holes 3 are used for mutually communicating the same layer of adjacent horizontal drilling holes 1; in the process, the stress of the coal seam is released due to the drilling operation, so that the released stress can be used for acting on the coal seam 6 around the drilling hole, the coal seam 6 is deformed and broken to form a drilling fracture zone, and a complex drilling network consisting of a horizontal drilling hole 1, a vertical drilling hole 2 and a lateral drilling hole 3 is formed in the coal seam 6;
step two: drilling a top plate horizontal well on the ground;
as shown in fig. 2, a ground drilling mode is adopted, a roof horizontal well 5 is drilled at the lower part of a roof 4, and the horizontal section of the roof horizontal well 5 is parallel to a coal seam 6; because the roof 4 has higher strength, the rock stratum structure is stable, and a stable borehole is easy to form when the roof horizontal well 5 passes through the roof 4;
step three: a roof horizontal well and a complex drilling network of the coal seam are communicated;
as shown in fig. 3, after the roof horizontal well 5 is drilled, a hydraulic jet sidetrack drilling mode is adopted to drill corresponding vertical communication holes 7 upwards in each horizontal drilling hole 1 at the uppermost layer, so that the vertical communication holes 7 are communicated with the horizontal sections of the horizontal drilling holes 1 at the uppermost layer and the roof horizontal well 5, and complex drilling network-vertical communication holes 7-complex well pattern channels in which the roof horizontal well 5 is mutually communicated are formed in the coal seam 6 and the roof 4; by adopting the mode, the coal seam 6 is communicated with the ground through the vertical communication hole 7 and the horizontal well 5 in the top plate, so that a channel is provided for later coal seam fracturing and permeability improvement and gas extraction;
step four: adding a liquid combustion improver;
as shown in fig. 4, a horizontal drilling hole 1 in a coal seam 6 is plugged in a underground transportation roadway or a return air roadway, then a liquid combustion improver 8 is put into the coal seam 6 from the ground through a roof horizontal well 5, the liquid combustion improver 8 enters the coal seam 6 through the roof horizontal well 5 and a vertical communication hole 7, flows into each region of the coal seam 6 through the horizontal drilling hole 1, the vertical drilling hole 2 and the lateral drilling hole 3 in the coal seam 6, and meanwhile, part of the liquid combustion improver 8 enters the coal seam 6 through cracks around the drilling holes;
step five: cracking by burning and explosion;
as shown in fig. 5, pre-extracting methane in a coal seam 6 through a roof horizontal well 5, monitoring the methane concentration in real time, closing a ground wellhead 9 of the roof horizontal well 5 after the extracted methane concentration exceeds 80%, then performing electric shock ignition on a methane-combustion improver mixture in a complex drilling network of the coal seam, igniting and detonating the methane-combustion improver mixture in the complex drilling network of the coal seam, impacting the coal seam 6 by utilizing high air pressure generated in the combustion explosion process of methane and combustion improver, promoting the coal seam 6 around the complex drilling network to form a large-scale crack 10, and further communicating a crack zone formed around the complex drilling network due to stress release;
step six: constructing a multi-scale methane extraction system;
repeating the steps four and five for a plurality of times, continuously carrying out combustion improver throwing and blasting fracturing operation in the coal seam 6, promoting continuous expansion and extension of cracks around the complex drilling network, further increasing the complexity and the extension distance of the cracks, and finally forming a natural crack-large-scale crack 10-complex drilling network-vertical communication holes 7 of the coal seam-top plate horizontal well 5 multi-scale methane extraction system in the coal seam 6.
In order to more comprehensively monitor the extraction process, in the fifth step, the components of methane are monitored synchronously while the concentration of methane is monitored.
Preferably, in the first step, the thickness of the coal seam 6 in the coal seam area is not less than 2m.
In order to obtain a better anti-reflection effect, in step S11, different heights of drilling positions of different layers from the bottom of the roadway are ensured.
In the invention, firstly, a plurality of layers of horizontal drilling holes are drilled in a coal seam area, the upper layer of adjacent horizontal drilling holes and the lower layer of adjacent horizontal drilling holes are communicated with each other by utilizing vertical drilling holes, and the same layer of adjacent horizontal drilling holes are communicated with each other by utilizing lateral drilling holes, so that a complex drilling network can be formed in the coal seam, and a communication channel inside the coal seam is provided for later coal seam fracturing and permeability increasing; secondly, the area where the top plate is located is selected for drilling the top plate horizontal well, a stable borehole can be formed by utilizing the characteristic of stable structure of the rock stratum where the top plate is located, so that the stability of the main body section of the fluid injection channel can be ensured, and powerful guarantee is provided for the fact that the subsequent liquid combustion improver can be fully injected into each part in the coal seam; then, the vertical communication holes are used for connecting the top plate horizontal well and the uppermost horizontal drilling holes, so that a complex drilling network, vertical drilling holes, vertical communication holes and complex well pattern channels which are communicated with each other are finally formed, the complex well pattern channels can enable all directions of the coal bed to be communicated with each other, the uniformity of crack distribution is greatly enhanced, the range of crack formation is effectively enlarged, the crack formation effect is better, in addition, the well pattern channels can enable all parts of the communication channels inside the coal bed to be fully communicated with the main body section of the fluid injection channel, the fact that the follow-up liquid combustion improver can be fully injected into all areas inside the coal bed is effectively ensured, and the follow-up liquid combustion improver can be further beneficial to enter into cracks inside the coal bed in all areas; then, after the horizontal drilling hole is plugged, the liquid combustion improver is put into the complex well pattern channel through the horizontal well of the top plate, so that the hydraulic combustion improver can be ensured to fully enter each part of the complex well pattern channel, the consumption of the liquid combustion improver is favorably saved, and moreover, the hydraulic combustion improver entering the cracks can also expel part of methane in the cracks into the main body channel, thereby being favorable for improving the gas extraction efficiency; finally, igniting and detonating the methane-combustion improver mixture in the complex drilling network of the coal bed after the liquid combustion improver is put in, and fully utilizing methane in the coal bed to perform in-situ ignition and explosion, so that large-scale cracks can be formed by utilizing high-pressure impact of the explosion to form a crack zone.
Claims (3)
1. The permeability-increasing method for the low permeability coal seam is characterized by comprising the following steps of;
step one: constructing a complex drilling network of the coal seam;
s11, aiming at a coal bed region with high gas concentration and high gas pressure of a coal bed, determining multi-layer drilling positions on the side surface in a return air roadway or a transport roadway in a mode parallel to a stope face;
s12, sequentially drilling horizontal drilling holes (1) from the bottom of a roadway to the upper part of the roadway, vertically upwards moving the drilling positions after completing a group of horizontal drilling holes (1) on the next layer, and then performing drilling operation on the horizontal drilling holes (1) on the upper layer;
s13, in the formed horizontal drilling holes (1), drilling a plurality of groups of vertical drilling holes (2) and lateral drilling holes (3) along the length direction of the horizontal drilling holes (1) in a hydraulic jet sidetrack mode along the vertical direction and the horizontal direction perpendicular to the horizontal drilling holes (1), communicating the upper layer of adjacent horizontal drilling holes (1) and the lower layer of adjacent horizontal drilling holes (1) with each other by using the vertical drilling holes (2), and communicating the same layer of adjacent horizontal drilling holes (1) with each other by using the lateral drilling holes (3); in the process, stress released in the drilling operation process is used for acting on the coal bed (6) around the drill hole, so that the coal bed (6) is deformed and broken to form a drill hole fracture zone, and a complex drilling network consisting of horizontal drill holes (1) -vertical drill holes (2) -lateral drill holes (3) is formed in the coal bed (6);
step two: drilling a top plate horizontal well on the ground;
drilling a roof horizontal well (5) at the lower part of the roof (4) in a ground drilling mode, and enabling the horizontal section of the roof horizontal well (5) to be parallel to the coal seam (6);
step three: a roof horizontal well and a complex drilling network of the coal seam are communicated;
after the roof horizontal well (5) is drilled, a hydraulic jet sidetrack drilling mode is adopted to drill corresponding vertical communication holes (7) upwards in each horizontal drilling hole (1) at the uppermost layer, so that the vertical communication holes (7) are communicated with horizontal sections of the horizontal drilling holes (1) at the uppermost layer and the roof horizontal well (5), and complex drilling network-vertical communication holes (7) -complex well pattern channels in which the roof horizontal well (5) are mutually communicated are formed in the coal seam (6) and the roof (4);
step four: adding a liquid combustion improver;
plugging horizontal drilling holes (1) in a coal bed (6) in a downhole transportation roadway or a return air roadway, then throwing a liquid combustion improver (8) into the coal bed (6) from the ground through a roof horizontal well (5), enabling the liquid combustion improver (8) to enter the coal bed (6) through the roof horizontal well (5) and a vertical communication hole (7), enabling the liquid combustion improver to flow into each area of the coal bed (6) through the horizontal drilling holes (1), the vertical drilling holes (2) and the lateral drilling holes (3) in the coal bed (6), and enabling part of the liquid combustion improver (8) to enter the coal bed (6) through cracks around the drilling holes;
step five: cracking by burning and explosion;
pre-extracting methane in a coal bed (6) through a roof horizontal well (5), monitoring the concentration of methane in real time, closing a ground wellhead (9) of the roof horizontal well (5) after the concentration of extracted methane exceeds 80%, then performing electric shock ignition on a methane-combustion improver mixture in a complex drilling network of the coal bed, igniting and detonating the methane-combustion improver mixture in the complex drilling network of the coal bed, and utilizing high air pressure generated in the combustion explosion process of the methane and the combustion improver to impact the coal bed (6), so as to promote the coal bed (6) around the complex drilling network to form large-scale cracks (10), and further communicating crack zones around the complex drilling network due to stress release;
monitoring the methane concentration and simultaneously monitoring the components of methane;
step six: constructing a multi-scale methane extraction system;
repeating the steps four and five for a plurality of times, continuously carrying out combustion improver throwing and blasting fracturing operation in the coal seam (6), promoting continuous expansion and extension of cracks around the complex drilling network, further increasing the complexity and the extension distance of the cracks, and finally forming a natural crack-large-scale crack (10) -coal seam complex drilling network-vertical communication holes (7) -roof horizontal well (5) multi-scale methane extraction system in the coal seam (6).
2. A low permeability coal seam anti-reflection method according to claim 1, wherein in step one the thickness of the coal seam (6) in the coal seam area is not less than 2m.
3. A low permeability coal seam anti-reflection method according to claim 1 or claim 2 wherein in step S11 it is ensured that the heights of different layer drill positions from the bottom of the tunnel are different.
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| RU2211308C2 (en) * | 2000-12-28 | 2003-08-27 | Институт проблем комплексного освоения недр РАН | Method of coal seam opening for methane recovery |
| CN102392677A (en) * | 2011-10-21 | 2012-03-28 | 河南煤业化工集团研究院有限责任公司 | Permeability improvement technology for coal bed gas reservoir cap by using three-dimensional fracture network modification |
| CN103104222B (en) * | 2013-02-01 | 2015-07-29 | 中北大学 | Ground peupendicular hole combines extraction coal bed gas method with concordant long drilled holes |
| CN104389631B (en) * | 2014-09-17 | 2016-09-21 | 中国矿业大学 | A kind of low air permeability coal seam slot and pressure break contract network anti-reflection method |
| CN108843241B (en) * | 2018-04-28 | 2020-01-14 | 中国矿业大学 | Cave pressure relief mining system for tectonic coal in-situ coal bed gas horizontal well |
| CN110173238A (en) * | 2019-05-27 | 2019-08-27 | 中国矿业大学(北京) | The anti-reflection extraction of high seam three-dimensional roadway layout networking explosion thick gas method entirely |
| CN112761588B (en) * | 2021-01-22 | 2022-02-08 | 中国矿业大学 | Shale reservoir methane in-situ combustion-explosion fracturing and combustion improver safe feeding cooperative control method |
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