CN114396244B - Method for extracting gas by up-and-down combined permeability-increasing of deep coal seam group well - Google Patents
Method for extracting gas by up-and-down combined permeability-increasing of deep coal seam group well Download PDFInfo
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- CN114396244B CN114396244B CN202111574458.4A CN202111574458A CN114396244B CN 114396244 B CN114396244 B CN 114396244B CN 202111574458 A CN202111574458 A CN 202111574458A CN 114396244 B CN114396244 B CN 114396244B
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- 239000003245 coal Substances 0.000 title claims abstract description 180
- 238000000034 method Methods 0.000 title claims abstract description 16
- 238000000605 extraction Methods 0.000 claims abstract description 190
- 238000010793 Steam injection (oil industry) Methods 0.000 claims abstract description 51
- 238000002347 injection Methods 0.000 claims abstract description 19
- 239000007924 injection Substances 0.000 claims abstract description 19
- 238000003795 desorption Methods 0.000 claims abstract description 9
- 239000012530 fluid Substances 0.000 claims description 75
- 238000005553 drilling Methods 0.000 claims description 68
- 239000002893 slag Substances 0.000 claims description 50
- 239000011435 rock Substances 0.000 claims description 38
- 239000002105 nanoparticle Substances 0.000 claims description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 239000011229 interlayer Substances 0.000 claims description 14
- 239000010410 layer Substances 0.000 claims description 13
- 239000000725 suspension Substances 0.000 claims description 12
- 230000001105 regulatory effect Effects 0.000 claims description 10
- 230000000274 adsorptive effect Effects 0.000 claims description 6
- 230000003116 impacting effect Effects 0.000 claims description 6
- 230000035699 permeability Effects 0.000 claims description 6
- 238000007789 sealing Methods 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 4
- 238000005065 mining Methods 0.000 claims description 4
- 239000011491 glass wool Substances 0.000 claims description 3
- 239000011241 protective layer Substances 0.000 claims description 3
- 238000009825 accumulation Methods 0.000 claims 2
- 238000005507 spraying Methods 0.000 claims 2
- 239000012634 fragment Substances 0.000 claims 1
- 230000002195 synergetic effect Effects 0.000 abstract description 3
- 230000015572 biosynthetic process Effects 0.000 description 8
- 238000001028 reflection method Methods 0.000 description 5
- 238000005520 cutting process Methods 0.000 description 4
- 230000006872 improvement Effects 0.000 description 3
- 230000004075 alteration Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 230000008901 benefit Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 238000005192 partition Methods 0.000 description 1
Classifications
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP 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
- E21B43/006—Production of coal-bed methane
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP 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
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
- E21B43/2405—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection in association with fracturing or crevice forming processes
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP 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
- E21B43/2605—Methods for stimulating production by forming crevices or fractures using gas or liquefied gas
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F7/00—Methods or devices for drawing- off gases with or without subsequent use of the gas for any purpose
Abstract
The invention provides an up-and-down combined anti-reflection gas extraction method for deep coal seam groups. According to the method, the multi-step heat injection is carried out by utilizing a plurality of pressure relief zones formed by hydraulic slotting, and the gas flows towards the direction of the orifice by utilizing the ring-type reciprocating sealer at the front end of the steam injection pipe, so that the gas is prevented from accumulating in the area outside the extraction range, the gas is directionally thermally driven, and the extraction efficiency of the gas is ensured. The use method of the system starts from two aspects of efficient fracturing of the coal seam and efficient desorption of the gas by utilizing the synergistic effect of hydraulic slotting and steam heat injection, and effectively solves the problems of high gas extraction difficulty and low extraction efficiency in the form of partitioned fracturing and directional thermal flooding of the gas.
Description
Technical Field
The invention relates to the technical field of gas extraction, in particular to an up-and-down combined anti-reflection gas extraction method for deep coal seam groups.
Background
Deep coal beds in China generally have the characteristics of high gas pressure, high content, low permeability and strong adsorptivity. The efficiency of coal mining is seriously affected by the problem of lower extraction efficiency due to the high extraction difficulty of deep gas.
The coal mine ground well gas extraction process is combined with the underground gas extraction process (namely underground combined extraction) to be one of important measures for preventing and controlling gas disaster accidents of the coal mine, and is an effective method for dealing with deep high-gas and high-ground stress coal seam groups at present. However, the extraction conditions of deep coal seam groups are also quite different due to different interlayer distances. The application effect of the combined underground extraction measures in engineering is not ideal, and the purpose of fully desorbing the gas in deep coal seams is difficult to achieve, so that the mine outburst risk still exists.
Therefore, development of an uphole and downhole combined anti-reflection gas extraction method for deep coal seam groups is needed.
Disclosure of Invention
The invention aims to provide an up-and-down combined anti-reflection gas extraction method for deep coal seam groups, which aims to solve the problems in the prior art.
The technical scheme adopted for achieving the purpose of the invention is that the underground combined anti-reflection gas extraction system of the deep coal seam group comprises an underground nano fluid fracturing subsystem, an underground gas extraction subsystem, an underground ultrahigh pressure nano fluid slotting subsystem, an underground directional thermal driving subsystem and an underground gas extraction subsystem.
The aboveground nanofluid fracturing subsystem comprises an aboveground measure hole, a fracturing string, a suspension packer and a nanofluid fracturing truck. The deep mining area comprises an upper coal seam and a lower coal seam. And an overburden layer is arranged above the upper coal layer. And an interlayer rock stratum is arranged between the upper coal bed and the lower coal bed. And an underlying rock stratum is arranged below the lower coal bed. The final hole location of the uphole formation is located in the upper coal seam or the interbedded rock formation. The fracturing string extends into the uphole formation bore. And a suspension packer is arranged on the shaft of the fracturing string. The upper end of the fracturing string is communicated with the nanofluid fracturing truck, and the lower end of the fracturing string is sequentially provided with a hydraulic injector, a screen pipe and a guide shoe.
The underground gas extraction subsystem comprises an orifice sealer, an underground gas-slag separator, an underground gas concentration detector, an underground gas extraction pipeline valve and an underground gas extraction pipeline. The orifice sealer is a tubular body. The front end of the orifice sealer is opened and fixed on the wall of the orifice of the uphole measuring hole, and the rear end is connected with the uphole gas-slag separator. The fracturing string extends from the rear end of the orifice sealer into the uphole service bore. The above-well gas-slag separator is connected with an above-well gas extraction pipeline. And an uphole gas concentration detector and an uphole gas extraction pipeline valve are arranged on a pipeline between the uphole gas-slag separator and the uphole gas extraction pipeline.
The underground gas extraction subsystem comprises an underground gas-slag separator, an underground gas concentration detector, an underground gas extraction pipeline valve and an underground gas extraction pipeline. The front end opening of the orifice sealer is fixed on the orifice wall of the underground measure orifice, and the rear end is connected with the underground gas-slag separator. The underground gas-slag separator is connected with an underground gas extraction pipeline. And an underground gas concentration detector and an underground gas extraction pipeline valve are arranged on a pipeline between the underground gas-slag separator and the underground gas extraction pipeline.
The underground ultrahigh pressure nano fluid slotting subsystem comprises a drill bit, a drilling machine, a drill rod, a booster pump and a nano fluid storage tank. And a pipeline valve is arranged on a high-pressure pipeline between the booster pump and the nanofluid storage tank. The drill rod is a hollow circular tube. The drilling machine clamps the tail end of the drill rod. The drill pipe extends from the rear end of the bore seal into the downhole tool bore. The side wall of the drill bit is provided with a pair of high-pressure nano fluid flow channels for injecting high-pressure nano fluid. The drill bit is arranged at the head end of the drill rod. The inner cavity of the drill bit is communicated with the inner cavity of the drill rod. The input end of the water braid is connected with the pressurizing pump through a high-pressure pipeline, and the output end of the water braid is connected with the tail end of the drill rod. The drilling machine drives the drill rod to rotate and drill into the coal stratum. The drill bit is driven by the rotation of the drill rod to rotate from the shaft. The nano fluid enters the inner cavity of the drill rod through the booster pump and the water braid. The nanofluid is fed into the drill bit through the lumen. The high-pressure nano fluid flow channel forms water jet to impact the coal rock mass. The coal rock mass is crushed by being impacted by a water jet or ground by a drill bit. The nanoparticles adhere to the surface of the coal cuttings. The nanofluid carries the coal rock slag back out to the downhole gas-slag separator.
The downhole directional thermal drive subsystem includes a steam generator and a steam injection pipe. The steam injection pipe extends into the downhole tool hole from the rear end of the orifice sealer. The steam generator is communicated with the inner cavity of the steam injection pipe through a pipeline. And a steam generator valve is arranged on a pipeline between the steam generator and the steam injection pipe. The outer wall of the head end of the steam injection pipe is provided with a ring-type reciprocating sealer and a pair of steam nozzles. The steam nozzle is communicated with the inner cavity of the steam injection pipe. The ring-type reciprocating sealer is positioned in front of the steam nozzle. The ring-type reciprocating sealer can be used for reciprocating sealing a gap between the wall of a drilling hole and the steam injection pipe. The hot steam generated by the steam generator is conveyed into the underground measure hole along the steam injection pipe and the steam nozzle. The coal body is heated by the heat carried by the hot steam.
Further, a glass wool protective layer is attached to the outer wall of the steam injection pipe.
The invention also discloses a remote deep coal seam group uphole and downhole combined permeability-increasing gas extraction method according to the system, which comprises the following steps of:
1) And (5) researching the layer position, thickness and strength parameters of the upper coal bed and the lower coal bed.
2) And determining an underground combined anti-reflection method according to the geological data and the actual drilling data.
3) And arranging hole positions of measure holes on the well in the upper coal seam, and sequentially connecting and debugging a nano fluid fracturing fluid nozzle, a fracturing string, a suspension packer and a nano fluid fracturing truck. Meanwhile, underground measure holes are constructed underground, and an underground ultrahigh pressure nano fluid force slotting subsystem and an underground gas extraction subsystem are connected and debugged in sequence.
4) Starting the drilling machine to drive the drill bit to perform drilling operation, opening the booster pump and the pipeline valve, regulating the pressure of the booster pump to 5-10MPa, enabling high-pressure nano fluid to be sprayed out from the side face of the drill bit through the high-pressure nano fluid flow passage outlet of the drill bit, impacting coal rock mass, enlarging the drilling diameter and improving the heat conductivity of the coal seam. Drilling and simultaneously opening a valve of the underground gas extraction pipeline to enable gas to be extracted into the underground gas extraction pipeline through the underground gas-slag separator, the underground gas concentration detector and the valve of the underground gas extraction pipeline.
5) When the drill bit passes through the 1m position of the overlying strata, stopping drilling, closing the booster pump, the pipeline valve and the drilling machine, and placing the drill bit in the upper coal seam after the drill bit is retreated 3-5m towards the orifice direction.
6) And starting the nanofluid fracturing truck, so that nanofluid fracturing fluid is sprayed out from a nanofluid fracturing fluid nozzle, continuous fracturing is carried out on an upper coal bed, and nanoparticles are adsorbed on the surface of the coal bed, so that the heat conductivity of the coal bed is improved. And (3) opening a valve of the gas extraction pipeline on the well when fracturing is performed, so that the gas enters the gas extraction pipeline on the well through the gas-slag separator on the well, the gas concentration detector on the well and the valve of the gas extraction pipeline on the well.
7) And opening a pipeline valve, starting a booster pump, regulating the pressure of the booster pump to 100-150MPa, enabling high-pressure nano fluid to be sprayed out through a high-pressure nano fluid flow passage outlet of the drill bit to crack the coal and rock mass, simultaneously starting the drill, enabling the drill to drive the drill bit to rotate around an axial lead, carrying out slotting and permeability improvement on the coal mass at the position of the drill bit, and enabling nano particles to be adsorbed in a coal bed to improve the heat conductivity of the coal bed.
8) After 3h of slotting, closing the pressurizing pump, the pipeline valve and the drilling machine. When the underground gas concentration detector shows that the gas concentration is lower than 20%, the valve of the underground gas extraction pipeline is closed, and gas extraction is stopped.
9) And (3) backing the drill bit to the lower coal seam towards the direction of the orifice, repeating the step 7) and the step 8), and backing the drill bit after the ultra-high pressure nano fluid of the lower coal seam is slotted.
10 The steam heat injection pipe is connected into the underground measure hole, the front end part of the steam heat injection pipe extends to the position 2-4m behind the overlying strata, a pair of steam nozzles are positioned at the first slit pressure relief zone, and the annular reciprocating sealer at the front end seals the gap between the steam heat injection pipe and the underground measure hole, prevents gas from accumulating in the extraction hole and ensures the directional flow of desorption gas.
11 The steam generator is started, a valve of the steam generator is opened, high-pressure hot steam is injected into the adjacent slotting pressure relief belt through a pair of steam nozzles at the upper end part of the steam injection pipe, the adjacent slotting pressure relief belt is heated, so that the temperature of coal is increased, and a large amount of adsorptive gas is desorbed. Simultaneously, a valve of the gas extraction pipeline is opened, so that gas is extracted into the underground gas extraction pipeline through the underground gas-slag separator, the underground gas concentration detector and the underground gas extraction pipeline valve:
12 After 3h of heat injection, the steam generator and the steam generator valve are closed. When the underground gas concentration detector shows that the gas concentration is always below 10%, the valve of the underground gas extraction pipeline is closed, and gas extraction is stopped.
13 The steam injection pipe is retreated to the lower coal seam towards the orifice direction, the steam nozzle is positioned at the position of the adjacent pressure relief zone, the ring-type reciprocating sealer is still kept at the position of 0.5m at the front end of the steam nozzle for sealing, the step 11) is repeated, and when the underground gas concentration detector shows that the gas concentration is always below 10%, the steam generator and the steam generator valve are closed.
14 Closing the nanofluid fracturing truck, withdrawing the fracturing string and the suspension packer from the uphole measure hole, and keeping the uphole gas extraction pipeline valve and the downhole gas extraction pipeline valve open all the time to continuously extract the gas.
The invention also discloses an up-and-down combined permeability-increasing gas extraction method for the near-distance deep coal seam group well of the system, which comprises the following steps:
1) And (5) researching the layer position, thickness and strength parameters of the upper coal bed and the lower coal bed.
2) And determining an underground combined anti-reflection method according to the geological data and the actual drilling data.
3) And arranging hole sites of measure holes on the well in the middle of the interlayer rock stratum, and sequentially connecting and debugging a nano fluid fracturing fluid nozzle, a fracturing string, a suspension packer and a nano fluid fracturing truck. Meanwhile, underground measure holes are constructed underground, and an underground ultrahigh pressure nano fluid force slotting subsystem and an underground gas extraction subsystem are connected and debugged in sequence.
4) Starting the drilling machine to drive the drill bit to perform drilling operation, opening the booster pump and the pipeline valve, regulating the pressure of the booster pump to 5-10MPa, enabling high-pressure nano fluid to be sprayed out from the side face of the drill bit through the high-pressure nano fluid flow passage outlet of the drill bit, impacting coal rock mass, enlarging the drilling diameter and improving the heat conductivity of the coal seam. Drilling and simultaneously opening a valve of the underground gas extraction pipeline to enable gas to be extracted into the underground gas extraction pipeline through the underground gas-slag separator, the underground gas concentration detector and the valve of the underground gas extraction pipeline.
5) When the drill bit passes through the interlayer rock stratum 1m, stopping drilling, closing the booster pump, the pipeline valve and the drilling machine, and placing the drill bit in the lower coal seam after the drill bit is retreated 3-5m towards the orifice direction.
6) And starting the nanofluid fracturing truck, so that nanofluid fracturing fluid is sprayed out from a nanofluid fracturing fluid nozzle, continuous fracturing is carried out on an interlayer rock stratum, an upper coal seam and a lower coal seam, and nanoparticles are adsorbed on the surface of the coal seam, so that the heat conductivity of the coal seam is improved. And (3) opening a valve of the gas extraction pipeline on the well when fracturing is performed, so that the gas enters the gas extraction pipeline on the well through the gas-slag separator on the well, the gas concentration detector on the well and the valve of the gas extraction pipeline on the well.
7) And opening a pipeline valve, starting a booster pump, regulating the pressure of the booster pump to 100-150MPa, enabling high-pressure nano fluid to be sprayed out through a high-pressure nano fluid flow passage outlet of the drill bit to crack the coal and rock mass, simultaneously starting the drilling machine, enabling the drilling machine to drive the drill bit to rotate around an axial lead, carrying out hydraulic slotting on the coal mass at the position of the drill bit, and enabling nano particles to be adsorbed in a coal bed to improve the heat conductivity of the coal bed.
8) After 3h of slotting, closing the pressurizing pump, the pipeline valve and the drilling machine. When the underground gas concentration detector shows that the gas concentration is lower than 20%, the valve of the underground gas extraction pipeline is closed, and gas extraction is stopped.
9) The steam heat injection pipe is connected into the underground measure hole, the front end part of the steam heat injection pipe extends to the position 2-4m behind the overlying strata, a pair of steam nozzles are positioned at the first slit pressure relief zone, and the annular reciprocating sealer at the front end seals the gap between the steam heat injection pipe and the underground measure hole, prevents gas from accumulating in the extraction hole and ensures the directional flow of desorption gas.
10 The steam generator is started, a valve of the steam generator is opened, high-pressure hot steam is injected into the adjacent slotting pressure relief belt through a pair of steam nozzles at the upper end part of the steam injection pipe, the adjacent slotting pressure relief belt is heated, so that the temperature of coal is increased, and a large amount of adsorptive gas is desorbed. Simultaneously, a valve of the gas extraction pipeline is opened, so that gas is extracted into the underground gas extraction pipeline through the underground gas-slag separator, the underground gas concentration detector and the underground gas extraction pipeline valve:
11 After 3h of heat injection, the steam generator and the steam generator valve are closed. When the underground gas concentration detector shows that the gas concentration is always below 10%, the valve of the underground gas extraction pipeline is closed, and gas extraction is stopped.
12 Closing the nanofluid fracturing truck, withdrawing the fracturing string and the suspension packer from the uphole measure hole, and keeping the uphole gas extraction pipeline valve and the downhole gas extraction pipeline valve open all the time to continuously extract the gas.
The technical effects of the invention are undoubted: aiming at the problems that deep coal seam gas is difficult to extract, coal seam groups are difficult to synergistically eliminate outburst and the like, the uphole and downhole coal seam anti-reflection methods are organically combined, and the uphole and downhole combined anti-reflection gas extraction system and method for the deep coal seam groups are provided, so that three-dimensional multi-source extraction of the deep coal seam groups is realized. The system realizes high-efficiency reflection-increasing and rapid outburst-eliminating of deep coal seam groups by efficiently matching the hydraulic reflection-increasing measure with steam heat injection and simultaneously utilizing the organic combination of the underground and the aboveground. Based on the characteristics of the short-distance coal seam group and the long-distance coal seam group, the method provides a system using method suitable for different coal seam groups, namely the short-distance coal seam group is used for pressing middle and cutting one layer, the long-distance coal seam group is used for pressing upper layers and cutting two layers, and construction cost is saved on the basis of rapid multi-source extraction. The system and the method for extracting the gas by combining the uphole and the downwell of the deep coal seam group scientifically and efficiently combine the uphole measures with the downhole measures, realize the rapid outburst elimination of the deep coal seam group and provide a thinking for solving the gas problem of the deep coal seam group in China.
Drawings
FIG. 1 is a schematic diagram of a remote coal seam group well top-bottom combined anti-reflection gas extraction;
FIG. 2 is a schematic diagram of the combined up and down permeability-increasing gas extraction of a close-range coal seam group well.
In the figure: the method comprises the steps of an upper coal seam 1, a lower coal seam 2, an overburden I3, an interbedded II 30, a underburden III 300, an uphole measure hole 4, an downhole measure hole 5, a fracturing string 6, a hanging packer 7, a nanofluid fracturing truck 8, a nanofluid fracturing fluid nozzle 9, a drill bit 10, a high-pressure nanofluid runner 10-1, a drilling machine 11, a drill pipe 12, a downhole gas and slag separator 13, a downhole gas concentration detector 14, a downhole gas extraction pipeline valve 15, a downhole gas extraction pipeline 16, a booster pump 17, a pipeline valve 18, a nanofluid storage tank 19, a steam generator valve 20, a steam generator 21, a steam injection pipe 22, a ring-type reciprocating sealer 22-1, a steam nozzle 22-2, a downhole gas and slag separator 23, a downhole gas concentration detector 24, a downhole gas extraction pipeline valve 25 and a downhole gas extraction pipeline 26.
Detailed Description
The present invention is further described below with reference to examples, but it should not be construed that the scope of the above subject matter of the present invention is limited to the following examples. Various substitutions and alterations are made according to the ordinary skill and familiar means of the art without departing from the technical spirit of the invention, and all such substitutions and alterations are intended to be included in the scope of the invention.
Example 1:
the embodiment provides an up-and-down combined permeability-increasing gas extraction system for deep coal seam groups, which comprises an aboveground nanofluid fracturing subsystem, an aboveground gas extraction subsystem, an underground ultrahigh-pressure nanofluid slotting subsystem, an underground directional thermal driving subsystem and an underground gas extraction subsystem.
The aboveground nanofluid fracturing subsystem comprises an aboveground measure hole 4, a fracturing string 6, a suspension packer 7 and a nanofluid fracturing truck 8. The deep mining area comprises an upper coal seam 1 and a lower coal seam 2. Above the upper coal seam 1 is an overburden 3. Between the upper coal seam 1 and the lower coal seam 2 is an interlayer rock layer 30. Below the lower coal seam 2 is an underburden 300. The final hole location of the uphole formation 4 is in the upper coal seam 1 or the interbay formation 30. The fracturing string 6 extends into the uphole formation bore 4. A hanging packer 7 is arranged on the shaft of the fracturing string 6. The upper end of the fracturing string 6 is communicated with a nanofluid fracturing truck 8, and the lower end of the fracturing string is sequentially provided with a hydraulic injector 9, a screen pipe and a guide shoe.
The underground gas extraction subsystem comprises an orifice sealer, an underground gas-slag separator 23, an underground gas concentration detector 24, an underground gas extraction pipeline valve 25 and an underground gas extraction pipeline 26. The orifice sealer is a tubular body. The front end of the orifice sealer is opened and fixed on the orifice wall of the uphole measuring hole 4, and the rear end is connected with the uphole gas-slag separator 23. The fracturing string 6 extends from the rear end of the orifice sealer into the uphole formation bore 4. The above-well gas-slag separator 23 is connected to an above-well gas extraction pipe 26. An uphole gas concentration detector 24 and an uphole gas extraction pipeline valve 25 are arranged on a pipeline between the uphole gas-slag separator 23 and the uphole gas extraction pipeline 26.
The underground gas extraction subsystem comprises an underground gas-slag separator 13, an underground gas concentration detector 14, an underground gas extraction pipeline valve 15 and an underground gas extraction pipeline 16. The front end opening of the orifice sealer is fixed on the orifice wall of the underground measure orifice 5, and the rear end is connected with the underground gas-slag separator 13. The downhole gas-slag separator 13 is connected with a downhole gas extraction pipeline 16. The underground gas concentration detector 14 and the underground gas extraction pipeline valve 15 are arranged on a pipeline between the underground gas-slag separator 13 and the underground gas extraction pipeline 16.
The downhole ultrahigh pressure nanofluid slotting subsystem comprises a drill bit 10, a drilling machine 11, a drill rod 12, a booster pump 17 and a nanofluid storage tank 19. A pipeline valve 18 is arranged on a high-pressure pipeline between the booster pump 17 and the nanofluid storage tank 19. The drill rod 12 is a hollow circular tube. The drill 11 grips the end of the drill rod 12. A drill rod 12 extends from the rear end of the bore sealer into the downhole tool bore 5. The side wall of the drill bit 10 is provided with a pair of high-pressure nanofluid flow channels 10-1 for injecting high-pressure nanofluid. The drill bit 10 is mounted at the head end of a drill pipe 12. The interior cavity of the drill bit 10 communicates with the interior cavity of the drill rod 12. The input end of the water braid is connected with the pressurizing pump 17 through a high-pressure pipeline, and the output end of the water braid is connected with the tail end of the drill rod 12. The drill 11 rotates the drill rod 12 and drills into the coal formation. The drill bit 10 is rotated by the rotation of the drill rod 12. The nanofluid enters the lumen of the drill rod 12 through the booster pump 17 and the water braid. The nanofluid is fed into the drill bit 10 through the lumen. The high-pressure nano fluid flow channel 10-1 forms water jet to impact coal and rock mass. The coal rock mass is crushed by being impacted by the water jet or ground by the drill bit 10. The nanoparticles adhere to the surface of the coal cuttings. The nanofluid carries the coal rock slag back out to the downhole gas-slag separator 13.
The downhole directional thermal drive subsystem includes a steam generator 21 and a steam injection pipe 22. A glass wool protective layer is attached to the outer wall of the steam injection pipe 22. The steam injection pipe 22 extends from the rear end of the orifice sealer into the downhole tool bore 5. The steam generator 21 is communicated with the inner cavity of the steam injection pipe 22 through a pipeline. A steam generator valve 20 is arranged on a pipeline between the steam generator 21 and the steam injection pipe 22. The outer wall of the head end of the steam injection pipe 22 is provided with a ring-type reciprocating sealer 22-1 and a pair of steam nozzles 22-2. The steam nozzle 22-2 communicates with the interior cavity of the steam injection pipe 22. The ring-type reciprocating sealer 22-1 is located in front of the steam nozzle 22-2. The ring-type reciprocating sealer 22-1 can reciprocally seal the gap between the borehole wall and the steam injection pipe 22. The hot steam generated by the steam generator 21 is delivered into the downhole tool hole 5 along the steam injection pipe 22 and the steam nozzle 22-2. The coal body is heated by the heat carried by the hot steam.
Aiming at the problems that gas in deep coal seam groups is difficult to desorb, a single ground well extraction technology is difficult to quickly eliminate outburst and the like, the embodiment organically combines the ground well extraction measures on the well with the borehole extraction measures in the well, thereby not only ensuring the advantage of wide gas extraction range on the well, but also ensuring the accuracy and high efficiency of underground gas extraction.
The multi-step heat injection is carried out by utilizing a plurality of pressure relief belts formed by hydraulic slotting, and the gas flows towards the direction of the orifice by utilizing the ring-type reciprocating sealer at the front end of the steam injection pipe, so that the gas is prevented from accumulating in the area outside the extraction range, the gas is directionally thermally driven, and the extraction efficiency of the gas is ensured. The hydraulic permeability-increasing measure and the steam heat injection measure are organically combined, and the synergistic effect of hydraulic slotting and steam heat injection is utilized, so that two aspects of efficient fracturing of a coal bed and efficient desorption of gas are started, and the problems of high gas extraction difficulty and low extraction efficiency of deep coal bed groups are effectively solved by a gas extraction means of 'pre-fracturing and post-heat flooding'. By utilizing the synergistic effect of hydraulic slotting and steam heat injection, the method starts from two aspects of coal seam high-efficiency fracturing and gas high-efficiency desorption, and effectively solves the problems of high gas extraction difficulty and low extraction efficiency in the form of partition fracturing and directional thermal flooding gas.
For coal seam thermal conductivity, the combined uphole and downhole anti-reflection systems can achieve a wide range of improvements in coal seam thermal conductivity, rather than achieving only a localized thermal conductivity improvement. For a gas migration channel, the uphole measures and the downhole measures are mutually complemented, so that the permeability of the deep coal seam can be greatly improved.
Example 2:
referring to fig. 1, the embodiment provides a method for uphole and downhole combined anti-reflection gas extraction of a remote deep coal seam group according to the system of embodiment 1, which comprises the following steps:
1) The level, thickness and strength parameters of the upper coal seam 1 and the lower coal seam 2 are investigated.
2) And determining an underground combined anti-reflection method according to the geological data and the actual drilling data.
3) The hole site of the measure hole 4 is arranged in the upper coal seam 1, and the nano fluid fracturing fluid nozzle 9, the fracturing string 6, the hanging packer 7 and the nano fluid fracturing truck 8 are sequentially connected and debugged. Meanwhile, an underground measure hole 5 is constructed underground, and an underground ultrahigh pressure nano fluid force slotting subsystem and an underground gas extraction subsystem are connected and debugged in sequence.
4) Starting the drilling machine 11 to drive the drill bit 10 to perform drilling operation, opening the booster pump 17 and the pipeline valve 18, adjusting the pressure of the booster pump 17 to 5-10MPa, enabling high-pressure nano fluid to be sprayed out of the side face of the drill bit through the outlet of the high-pressure nano fluid flow channel 10-1 of the drill bit 10, impacting coal and rock mass, enlarging the drilling diameter and improving the heat conductivity of the coal seam. Drilling while opening the downhole gas extraction pipeline valve 15, so that gas is extracted into the downhole gas extraction pipeline 16 through the downhole gas-slag separator 13, the downhole gas concentration detector 14 and the downhole gas extraction pipeline valve 15.
5) When the drill bit 10 passes through the overburden 31m, the drilling is stopped, the booster pump 17, the pipeline valve 18 and the drilling machine 11 are closed, and the drill bit 10 is retracted towards the orifice direction for 3-5m and placed in the overburden 1.
6) And starting the nanofluid fracturing truck 8, so that nanofluid fracturing fluid is sprayed out from a nanofluid fracturing fluid nozzle 9 to continuously fracture the upper coal seam 1, and simultaneously, nano particles are adsorbed on the surface of the coal seam to improve the heat conductivity of the coal seam. And at the same time of fracturing, opening an uphole gas extraction pipeline valve 25 to enable gas to enter an uphole gas extraction pipeline 26 through an uphole gas-slag separator 23, an uphole gas concentration detector 24 and the uphole gas extraction pipeline valve 25.
7) Opening a pipeline valve 18, starting a pressurizing pump 17, regulating the pressure of the pressurizing pump 17 to 100-150MPa, enabling high-pressure nano fluid to be sprayed out through an outlet of a high-pressure nano fluid flow channel 10-1 of a drill bit 10 to crack a coal rock mass, starting a drilling machine 11, enabling the drilling machine 11 to drive the drill bit 10 to rotate around an axial lead, carrying out slotting permeability increase on the coal mass at the position of the drill bit 10, and enabling nano particles to be adsorbed in a coal bed to improve the heat conductivity of the coal bed.
8) After 3h of slotting, the pressurizing pump 17, the pipeline valve 18 and the drilling machine 11 are closed. When the underground gas concentration detector 14 shows that the gas concentration is lower than 20%, the underground gas extraction pipeline valve 15 is closed, and gas extraction is stopped.
9) And (3) backing the drill bit 10 to the lower coal seam 2 towards the orifice direction, repeating the step 7) and the step 8), and backing the drill bit after the ultra-high pressure nano fluid of the lower coal seam 2 is slotted.
10 The steam injection pipe 22 is connected into the underground measure hole 5, the front end part of the steam injection pipe 22 extends to the position 2-4m behind the overlying strata 3, a pair of steam nozzles 22-2 are positioned at the first slit pressure relief zone, and the annular reciprocating sealer 22-1 at the front end seals the gap between the steam injection pipe 22 and the underground measure hole 5, prevents gas from accumulating in the extraction hole and ensures the directional flow of desorption gas.
11 The steam generator 21 is started, the steam generator valve 20 is opened, high-pressure hot steam is injected into the adjacent slit pressure relief zone through the pair of steam nozzles 22-2 at the upper end part of the steam injection pipe 22, and the temperature of the coal is raised and the adsorptive gas is desorbed in a large amount by heating the adjacent slit pressure relief zone. Simultaneously, the gas extraction pipeline valve 15 is opened, so that gas is extracted into the underground gas extraction pipeline 16 through the underground gas-slag separator 13, the underground gas concentration detector 14 and the underground gas extraction pipeline valve 15:
12 After 3h of heat injection, the steam generator 21 and the steam generator valve 20 are closed. When the underground gas concentration detector 14 shows that the gas concentration is always below 10%, the underground gas extraction pipeline valve 15 is closed, and gas extraction is stopped.
13 The steam injection pipe 22 is retreated to the lower coal seam 2 towards the orifice direction, the steam nozzle 22-2 is positioned at the adjacent pressure relief zone, the ring-type reciprocating sealer 22-1 is still kept at the front end 0.5m of the steam nozzle 22-2 for sealing, the step 11) is repeated, and when the underground gas concentration detector 14 shows that the gas concentration is always below 10%, the steam generator 21 and the steam generator valve 20 are closed.
14 Closing the nanofluid fracturing truck 8, withdrawing the fracturing string 6 and the hanging packer 7 from the uphole measure hole 4, and keeping the uphole gas extraction pipeline valve 25 and the downhole gas extraction pipeline valve 15 open all the time for continuously extracting the gas.
Example 3:
referring to fig. 2, the embodiment provides a near-distance deep coal seam group well up-down combined anti-reflection gas extraction method according to the system of embodiment 1, which comprises the following steps:
1) The level, thickness and strength parameters of the upper coal seam 1 and the lower coal seam 2 are investigated.
2) And determining an underground combined anti-reflection method according to the geological data and the actual drilling data.
3) The hole site of the well-surface measure hole 4 is arranged in the middle of the interlayer rock stratum 30, and the nano fluid fracturing fluid nozzle 9, the fracturing string 6, the hanging packer 7 and the nano fluid fracturing truck 8 are sequentially connected and debugged. Meanwhile, an underground measure hole 5 is constructed underground, and an underground ultrahigh pressure nano fluid force slotting subsystem and an underground gas extraction subsystem are connected and debugged in sequence.
4) Starting the drilling machine 11 to drive the drill bit 10 to perform drilling operation, opening the booster pump 17 and the pipeline valve 18, adjusting the pressure of the booster pump 17 to 5-10MPa, enabling high-pressure nano fluid to be sprayed out of the side face of the drill bit through the outlet of the high-pressure nano fluid flow channel 10-1 of the drill bit 10, impacting coal and rock mass, enlarging the drilling diameter and improving the heat conductivity of the coal seam. Drilling while opening the downhole gas extraction pipeline valve 15, so that gas is extracted into the downhole gas extraction pipeline 16 through the downhole gas-slag separator 13, the downhole gas concentration detector 14 and the downhole gas extraction pipeline valve 15.
5) When the drill bit 10 passes through the interlayer rock layer 301m, the drilling is stopped, the booster pump 17, the pipeline valve 18 and the drilling machine 11 are closed, and the drill bit 10 is retracted towards the orifice direction for 3-5m and is placed in the lower coal seam 2.
6) The nanofluid fracturing truck 8 is started, so that nanofluid fracturing fluid is sprayed out from the nanofluid fracturing fluid nozzle 9, the interlayer rock stratum 30, the upper coal bed 1 and the lower coal bed 2 are continuously fractured, and meanwhile nanoparticles are adsorbed on the surface of the coal bed, so that the heat conductivity of the coal bed is improved. And at the same time of fracturing, opening an uphole gas extraction pipeline valve 25 to enable gas to enter an uphole gas extraction pipeline 26 through an uphole gas-slag separator 23, an uphole gas concentration detector 24 and the uphole gas extraction pipeline valve 25.
7) Opening a pipeline valve 18, starting a pressurizing pump 17, regulating the pressure of the pressurizing pump 17 to 100-150MPa, enabling high-pressure nano fluid to be sprayed out through an outlet of a high-pressure nano fluid flow channel 10-1 of the drill bit 10 to crack coal and rock mass, starting a drilling machine 11, enabling the drilling machine 11 to drive the drill bit 10 to rotate around an axial lead, carrying out hydraulic slotting on the coal mass where the drill bit 10 is located, and enabling nano particles to be adsorbed in a coal bed to improve the heat conductivity of the coal bed.
8) After 3h of slotting, the pressurizing pump 17, the pipeline valve 18 and the drilling machine 11 are closed. When the underground gas concentration detector 14 shows that the gas concentration is lower than 20%, the underground gas extraction pipeline valve 15 is closed, and gas extraction is stopped.
9) The steam injection pipe 22 is connected into the underground measure hole 5, the front end part of the steam injection pipe extends to the position 2-4m behind the upper overburden layer 3, a pair of steam nozzles 22-2 are positioned at the first slit pressure relief zone, and the annular reciprocating sealer 22-1 at the front end seals the gap between the steam injection pipe 22 and the underground measure hole 5, prevents gas from accumulating in the extraction hole and ensures the directional flow of desorption gas.
10 The steam generator 21 is started, the steam generator valve 20 is opened, high-pressure hot steam is injected into the adjacent slit pressure relief zone through the pair of steam nozzles 22-2 at the upper end part of the steam injection pipe 22, and the temperature of the coal is raised and the adsorptive gas is desorbed in a large amount by heating the adjacent slit pressure relief zone. Simultaneously, the gas extraction pipeline valve 15 is opened, so that gas is extracted into the underground gas extraction pipeline 16 through the underground gas-slag separator 13, the underground gas concentration detector 14 and the underground gas extraction pipeline valve 15:
11 After 3h of heat injection, the steam generator 21 and the steam generator valve 20 are closed. When the underground gas concentration detector 14 shows that the gas concentration is always below 10%, the underground gas extraction pipeline valve 15 is closed, and gas extraction is stopped.
12 Closing the nanofluid fracturing truck 8, withdrawing the fracturing string 6 and the hanging packer 7 from the uphole measure hole 4, and keeping the uphole gas extraction pipeline valve 25 and the downhole gas extraction pipeline valve 15 open all the time for continuously extracting the gas.
Claims (4)
1. The utility model provides a deep coal seam crowd is combination anti-reflection gas drainage system from top to bottom in pit which characterized in that: the system comprises an aboveground nanofluid fracturing subsystem, an aboveground gas extraction subsystem, an underground ultrahigh-pressure nanofluid slotting subsystem, an underground directional thermal driving subsystem and an underground gas extraction subsystem;
the aboveground nanofluid fracturing subsystem comprises an aboveground measure hole (4), a fracturing string (6), a suspension packer (7) and a nanofluid fracturing truck (8); the deep mining area comprises an upper coal bed (1) and a lower coal bed (2); an overburden layer (3) is arranged above the upper coal bed (1); an interlayer rock stratum (30) is arranged between the upper coal bed (1) and the lower coal bed (2); an underlying rock stratum (300) is arranged below the lower coal bed (2); the final hole position of the uphole measure hole (4) is positioned in the upper coal bed (1) or the interlayer rock stratum (30); the fracturing string (6) extends into the uphole measure hole (4); a suspension packer (7) is arranged on the column shaft of the fracturing column (6); the upper end of the fracturing string (6) is communicated with the nanofluid fracturing truck (8), and the lower end of the fracturing string is sequentially provided with a hydraulic injector (9), a screen pipe and a guide shoe;
the underground gas extraction subsystem comprises an orifice sealer, an underground gas-slag separator (23), an underground gas concentration detector (24), an underground gas extraction pipeline valve (25) and an underground gas extraction pipeline (26); the orifice sealer is a tubular body; the front end of the orifice sealer is opened and fixed on the orifice wall of the uphole measure orifice (4), and the rear end is connected with the uphole gas-slag separator (23); the fracturing string (6) extends into the uphole measure hole (4) from the rear end of the orifice sealer; the aboveground gas-slag separator (23) is connected with an aboveground gas extraction pipeline (26); an uphole gas concentration detector (24) and an uphole gas extraction pipeline valve (25) are arranged on a pipeline between the uphole gas-slag separator (23) and the uphole gas extraction pipeline (26);
the underground gas extraction subsystem comprises an underground gas-slag separator (13), an underground gas concentration detector (14), an underground gas extraction pipeline valve (15) and an underground gas extraction pipeline (16); the front end opening of the orifice sealer is fixed on the orifice wall of the underground measure orifice (5), and the rear end is connected with the underground gas-slag separator (13); the underground gas-slag separator (13) is connected with an underground gas extraction pipeline (16); an underground gas concentration detector (14) and an underground gas extraction pipeline valve (15) are arranged on a pipeline between the underground gas-slag separator (13) and the underground gas extraction pipeline (16);
the underground ultrahigh-pressure nanofluid slotting subsystem comprises a drill bit (10), a drilling machine (11), a drill rod (12), a booster pump (17) and a nanofluid storage tank (19); a pipeline valve (18) is arranged on a high-pressure pipeline between the booster pump (17) and the nanofluid storage tank (19); the drill rod (12) is a hollow circular tube; the drilling machine (11) clamps the tail end of the drill rod (12); a drill rod (12) extends into the underground measure hole (5) from the rear end of the orifice sealer; a pair of high-pressure nanofluid flow channels (10-1) for injecting high-pressure nanofluid are arranged on the side wall of the drill bit (10); the drill bit (10) is arranged at the head end of the drill rod (12); the inner cavity of the drill bit (10) is communicated with the inner cavity of the drill rod (12); the input end of the water braid is connected with a pressurizing pump (17) through a high-pressure pipeline, and the output end of the water braid is connected with the tail end of the drill rod (12); the drilling machine (11) drives the drill rod (12) to rotate and drill into the coal stratum; the drill bit (10) is driven by the rotation of the drill rod (12) to rotate from the shaft; the nano fluid enters the inner cavity of the drill rod (12) through the booster pump (17) and the water braid; the nanofluid is sent into a drill bit (10) through the inner cavity; the high-pressure nano fluid flow channel (10-1) forms water jet to impact the coal rock mass; the coal rock mass is crushed by being impacted by water jet or ground and crushed by a drill bit (10); the nano particles are adhered to the surfaces of the coal and rock fragments; the nanofluid carries coal rock slag to return to a downhole gas-slag separator (13);
the underground directional thermal driving subsystem comprises a steam generator (21) and a steam injection pipe (22); the steam injection pipe (22) extends into the underground measure hole (5) from the rear end of the orifice sealer; the steam generator (21) is communicated with the inner cavity of the steam injection pipe (22) through a pipeline; a steam generator valve (20) is arranged on a pipeline between the steam generator (21) and the steam injection pipe (22); the outer wall of the head end of the steam injection pipe (22) is provided with a ring-type reciprocating sealer (22-1) and a pair of steam nozzles (22-2); the steam nozzle (22-2) is communicated with the inner cavity of the steam injection pipe (22); the ring-type reciprocating sealer (22-1) is positioned in front of the steam nozzle (22-2); the ring-type reciprocating sealer (22-1) can be used for reciprocating sealing the gap between the wall of the drilling hole and the steam injection pipe (22); the hot steam generated by the steam generator (21) is conveyed into the underground measure hole (5) along the steam injection pipe (22) and the steam nozzle (22-2); the coal body is heated by the heat carried by the hot steam.
2. The deep coal seam group uphole and downhole combined anti-reflection gas extraction system as claimed in claim 1, wherein: and a glass wool protective layer is attached to the outer wall of the steam injection pipe (22).
3. A method for uphole and downhole combined permeability-enhancing gas extraction of a remote deep coal seam group in accordance with the system of claim 1, comprising the steps of:
1) The layer position, thickness and strength parameters of the upper coal bed (1) and the lower coal bed (2) are investigated;
2) Determining an uphole and downhole combined permeability increasing method according to geological data and actual drilling data;
3) Hole positions of measure holes (4) on a well are arranged in an upper coal seam (1), and a nano fluid fracturing fluid nozzle (9), a fracturing string (6), a suspension packer (7) and a nano fluid fracturing truck (8) are connected and debugged in sequence; simultaneously, constructing an underground measure hole (5) in the pit, and sequentially connecting and debugging an underground ultrahigh pressure nano fluid force slotting subsystem and an underground gas extraction subsystem;
4) Starting a drilling machine (11) to drive a drill bit (10) to perform drilling operation, opening a booster pump (17) and a pipeline valve (18), regulating the pressure of the booster pump (17) to 5-10MPa, enabling high-pressure nano fluid to be sprayed out from the side surface of the drill bit through an outlet of a high-pressure nano fluid flow channel (10-1) of the drill bit (10), impacting coal and rock mass, enlarging the drilling diameter, and improving the heat conductivity of a coal bed; drilling and simultaneously opening an underground gas extraction pipeline valve (15) to enable gas to be extracted into an underground gas extraction pipeline (16) through an underground gas-slag separator (13), an underground gas concentration detector (14) and the underground gas extraction pipeline valve (15);
5) Stopping drilling when the drill bit (10) passes through the 1m position of the overburden (3), closing the pressurizing pump (17), the pipeline valve (18) and the drilling machine (11), and placing the drill bit (10) in the upper coal seam (1) 3-5m after retreating towards the orifice direction;
6) Starting a nanofluid fracturing truck (8), spraying nanofluid fracturing fluid from a nanofluid fracturing fluid nozzle (9), continuously fracturing an upper coal bed (1), adsorbing nano particles on the surface of the coal bed, and improving the heat conductivity of the coal bed; simultaneously, opening an uphole gas extraction pipeline valve (25) to enable gas to enter an uphole gas extraction pipeline (26) through an uphole gas-slag separator (23), an uphole gas concentration detector (24) and an uphole gas extraction pipeline valve (25);
7) Opening a pipeline valve (18), starting a pressurizing pump (17), regulating the pressure of the pressurizing pump (17) to 100-150MPa, enabling high-pressure nano fluid to be sprayed out through an outlet of a high-pressure nano fluid flow channel (10-1) of a drill bit (10) to crack coal and rock mass, starting a drilling machine (11) at the same time, enabling the drilling machine (11) to drive the drill bit (10) to rotate around an axial lead, slotting and permeability-increasing the coal mass at the position of the drill bit (10), and enabling nano particles to be adsorbed in a coal bed to improve the heat conductivity of the coal bed;
8) After slotting for 3h, closing the pressurizing pump (17), the pipeline valve (18) and the drilling machine (11); when the underground gas concentration detector (14) shows that the gas concentration is lower than 20%, the underground gas extraction pipeline valve (15) is closed, and gas extraction is stopped;
9) The drill bit (10) is retreated to the lower coal bed (2) towards the orifice direction, the step 7) and the step 8) are repeated, and after the ultra-high pressure nano fluid of the lower coal bed (2) is slotted, the drill bit is retreated;
10 The steam injection pipe (22) is connected into the underground measure hole (5), the front end part of the steam injection pipe extends to the position 2-4m behind the upper strata (3), a pair of steam nozzles (22-2) are positioned at the first slotting pressure relief zone, a ring-type reciprocating sealer (22-1) at the front end seals a gap between the steam injection pipe (22) and the underground measure hole (5), gas accumulation in the extraction hole is prevented, and directional flow of desorption gas is ensured;
11 Starting a steam generator (21), opening a steam generator valve (20), injecting high-pressure hot steam into an adjacent slotting pressure relief belt through a pair of steam nozzles (22-2) at the upper end part of a steam injection pipe (22), heating the adjacent slotting pressure relief belt to raise the temperature of coal and desorb a large amount of adsorptive gas; simultaneously, a gas extraction pipeline valve (15) is opened, so that gas is extracted into a gas extraction pipeline (16) through a downhole gas-slag separator (13), a downhole gas concentration detector (14) and the downhole gas extraction pipeline valve (15);
12 After heat injection for 3 hours, closing the steam generator (21) and the steam generator valve (20); when the underground gas concentration detector (14) shows that the gas concentration is always below 10%, the underground gas extraction pipeline valve (15) is closed, and gas extraction is stopped;
13 The steam injection pipe (22) is retreated to the lower coal seam (2) towards the orifice direction, the steam nozzle (22-2) is positioned at the position of the adjacent pressure relief zone, the ring-type reciprocating sealer (22-1) is still kept at the position of 0.5m at the front end of the steam nozzle (22-2) for sealing, the step 11) is repeated, and when the underground gas concentration detector (14) shows that the gas concentration is always below 10%, the steam generator (21) and the steam generator valve (20) are closed;
14 Closing the nanofluid fracturing truck (8), withdrawing the fracturing string (6) and the hanging packer (7) from the uphole measure hole (4), and keeping the uphole gas extraction pipeline valve (25) and the downhole gas extraction pipeline valve (15) to be always opened for continuously extracting the gas;
4. a method for combined uphole and downhole permeability-enhancing gas extraction of a close-range deep coal seam group according to the system of claim 1, comprising the steps of:
1) The layer position, thickness and strength parameters of the upper coal bed (1) and the lower coal bed (2) are investigated;
2) Determining an uphole and downhole combined permeability increasing method according to geological data and actual drilling data;
3) Arranging hole sites of a well-top measure hole (4) in the middle of an interlayer rock stratum (30), and connecting and debugging a nano fluid fracturing fluid nozzle (9), a fracturing string (6), a suspension packer (7) and a nano fluid fracturing truck (8) in sequence; simultaneously, constructing an underground measure hole (5) in the pit, and sequentially connecting and debugging an underground ultrahigh pressure nano fluid force slotting subsystem and an underground gas extraction subsystem;
4) Starting a drilling machine (11) to drive a drill bit (10) to perform drilling operation, opening a booster pump (17) and a pipeline valve (18), regulating the pressure of the booster pump (17) to 5-10MPa, enabling high-pressure nano fluid to be sprayed out from the side surface of the drill bit through an outlet of a high-pressure nano fluid flow channel (10-1) of the drill bit (10), impacting coal and rock mass, enlarging the drilling diameter, and improving the heat conductivity of a coal bed; drilling and simultaneously opening an underground gas extraction pipeline valve (15) to enable gas to be extracted into an underground gas extraction pipeline (16) through an underground gas-slag separator (13), an underground gas concentration detector (14) and the underground gas extraction pipeline valve (15);
5) Stopping drilling when the drill bit (10) passes through the interlayer rock stratum (30) for 1m, closing the pressurizing pump (17), the pipeline valve (18) and the drilling machine (11), and placing the drill bit (10) in the lower coal seam (2) 3-5m after being retracted towards the orifice direction;
6) Starting a nanofluid fracturing truck (8), spraying nanofluid fracturing fluid from a nanofluid fracturing fluid nozzle (9), continuously fracturing an interlayer rock stratum (30), an upper coal bed (1) and a lower coal bed (2), and simultaneously adsorbing nano particles on the surface of the coal bed to improve the heat conductivity of the coal bed; simultaneously, opening an uphole gas extraction pipeline valve (25) to enable gas to enter an uphole gas extraction pipeline (26) through an uphole gas-slag separator (23), an uphole gas concentration detector (24) and an uphole gas extraction pipeline valve (25);
7) Opening a pipeline valve (18), starting a pressurizing pump (17), regulating the pressure of the pressurizing pump (17) to 100-150MPa, enabling high-pressure nano fluid to be sprayed out through an outlet of a high-pressure nano fluid flow channel (10-1) of a drill bit (10) to crack coal and rock mass, starting a drilling machine (11) at the same time, enabling the drilling machine (11) to drive the drill bit (10) to rotate around an axial lead, carrying out hydraulic slotting on the coal mass at the position of the drill bit (10), and enabling nano particles to be adsorbed in a coal bed to improve the heat conductivity of the coal bed;
8) After slotting for 3h, closing the pressurizing pump (17), the pipeline valve (18) and the drilling machine (11); when the underground gas concentration detector (14) shows that the gas concentration is lower than 20%, the underground gas extraction pipeline valve (15) is closed, and gas extraction is stopped;
9) The steam injection pipe (22) is connected into the underground measure hole (5), the front end part of the steam injection pipe extends to the position 2-4m behind the upper strata (3), a pair of steam nozzles (22-2) are positioned at the first slotting pressure relief zone, a ring-type reciprocating sealer (22-1) at the front end seals a gap between the steam injection pipe (22) and the underground measure hole (5), gas accumulation in the extraction hole is prevented, and directional flow of desorption gas is ensured;
10 Starting a steam generator (21), opening a steam generator valve (20), injecting high-pressure hot steam into an adjacent slotting pressure relief belt through a pair of steam nozzles (22-2) at the upper end part of a steam injection pipe (22), heating the adjacent slotting pressure relief belt to raise the temperature of coal and desorb a large amount of adsorptive gas; simultaneously, a gas extraction pipeline valve (15) is opened, so that gas is extracted into a gas extraction pipeline (16) through a downhole gas-slag separator (13), a downhole gas concentration detector (14) and the downhole gas extraction pipeline valve (15);
11 After heat injection for 3 hours, closing the steam generator (21) and the steam generator valve (20);
when the underground gas concentration detector (14) shows that the gas concentration is always below 10%, the underground gas extraction pipeline valve (15) is closed, and gas extraction is stopped;
12 Closing the nanofluid fracturing truck (8), withdrawing the fracturing string (6) and the suspension packer (7) from the uphole measure hole (4), and keeping the uphole gas extraction pipeline valve (25) and the downhole gas extraction pipeline valve (15) to be always opened for continuously extracting the gas.
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