Coal seam mechanical modification anti-reflection system

Abstract

A coal seam mechanical modification anti-reflection system comprises a blast hole formed in a coal seam, and two freezing extraction holes are formed in the coal seam and are in bilateral symmetry with the blast hole as the center; extraction pipes and freezing pipes are arranged in the freezing extraction holes, the extraction pipes are arranged along the center positions of the freezing extraction holes, and the freezing pipes are U-shaped pipes and laid along the inner walls of the freezing extraction holes; the extraction pipe and the freezing pipe both penetrate through the grouting hole sealing section, a liquid inlet of the freezing pipe is connected with an air outlet of a heat insulation stainless steel hose, an air inlet of the heat insulation stainless steel hose is connected into a liquid nitrogen tank, a liquid nitrogen distributor is arranged on the heat insulation stainless steel hose, and a pressure monitoring device, a flow monitoring device and a liquid nitrogen tank valve are arranged on the liquid nitrogen tank. A liquid outlet valve is mounted at a liquid outlet of the freezing pipe; a CO2 blasting pipe and a temperature sensor are arranged in the blasting hole, and a blasting pipe valve is arranged at the air outlet end of the CO2 blasting pipe. The coal seam fracturing and permeability increasing device can improve the coal seam fracturing and permeability increasing effect and has a good promoting effect on gas extraction.

Description

Technical Field

[0001] The utility model relates to a coal seam permeability enhancement system, in particular to a coal seam mechanical modification permeability enhancement system, belonging to the technical field of coal sample gas mining. Background Art

[0002] Coal mines are the main source of energy in my country. During the coal mining process, gas extraction from coal seams is an important part of ensuring mine safety. However, for low-permeability and soft coal seams, due to their special physical properties, such as coal body fragmentation, low permeability, and high gas content, gas extraction efficiency is low, and may even cause safety hazards such as gas accumulation and gas explosion.

[0003] In order to overcome the difficulties of low-permeability and soft coal seams in gas extraction, researchers have been exploring new coal seam treatment methods. The coal seam permeability enhancement technologies currently used mainly include hydraulic fracturing, hydraulic slitting, pre-splitting blasting, loosening blasting, hydraulic punching, liquid nitrogen freeze-thaw fracturing, etc. The above methods can improve the permeability of coal seams to a certain extent and enhance gas extraction, but these methods themselves also have certain limitations.

[0004] Existing blasting technologies include pre-splitting blasting, loosening blasting, concentrated energy blasting and CO 2 Phase change blasting has the problem of poor fracturing effect due to the collapse of soft coal seams. Loosening blasting and pre-splitting blasting technologies produce greater pollution when used to increase the permeability of the coal body, and are prone to excessive local pressure or open flames, and gas explosion accidents when the gas in the tunnel exceeds the limit. Loosening blasting technology is mostly used for hard coal seams with weak protrusion strength.

[0005] In recent years, liquid nitrogen freezing technology has been gaining attention due to its technical advantages such as low consumption and no pollution. Compared with other unconventional oil and gas reservoirs, coal seams have strong heterogeneity and weak mechanical properties, which are more conducive to enhancing the damage effect of liquid nitrogen cryogenics. Therefore, applying liquid nitrogen to coal seam permeability enhancement will achieve better results. However, the existing liquid nitrogen fracturing technology mainly involves liquid nitrogen cycle freeze-thaw, which deteriorates the mechanical properties of coal, promotes the development of coal rock pores and cracks, increases permeability, and improves gas extraction rate. However, since liquid nitrogen cycle freeze-thaw technology requires dozens of cycles to achieve the permeability enhancement effect, it has the disadvantages of high cost, long time, and excessive nitrogen causing the oxygen concentration to drop. Summary of the invention

[0006] In view of the problems existing in the above-mentioned prior art, the utility model provides a coal seam mechanical modification and permeability enhancement system, which has a simple structure and is easy to operate. The mechanical strength and brittleness of the coal are greatly improved through the low-temperature freezing process, and then CO 2 Phase change blasting can fractur e coal seams, which can improve the fracturing and permeability enhancement effect of coal seams and has a good promoting effect on gas extraction.

[0007] In order to achieve the above-mentioned purpose, the utility model provides a coal seam mechanical modification and permeability enhancement system, including a blasting hole arranged in the coal seam, and the two ends of the blasting hole are respectively arranged in the rock layer on both sides of the coal seam, that is, the blasting hole is arranged through the coal seam, and also includes two freezing extraction holes, the two freezing extraction holes are arranged in the coal seam, and are arranged symmetrically with the blasting hole as the center; the freezing extraction holes are each provided with an extraction pipe and a freezing pipe, and the extraction pipe is arranged along the center of the freezing extraction hole. In order to ensure that a large amount of liquid nitrogen will not reduce the oxygen concentration of the working face after being gasified into nitrogen, the utility model uses a freezing extraction hole. The pipe is a U-shaped pipe, which can be used for nitrogen recovery and treatment. The U-shaped freezing pipe is laid along the inner wall of the freezing extraction hole; the extraction pipe and the freezing pipe both pass through the grouting sealing section, one end of the grouting pipe extends into the grouting sealing section, and the other end of the grouting pipe is connected to the grouting pump; the liquid inlet of the freezing pipe is connected to the air outlet of the insulated stainless steel hose, the air inlet of the insulated stainless steel hose is connected to the liquid nitrogen tank, and a liquid nitrogen distributor is set on the insulated stainless steel hose, the liquid nitrogen tank is provided with a pressure monitoring device, a flow monitoring device and a liquid nitrogen tank valve, and a liquid outlet valve is installed at the position of the liquid outlet of the freezing pipe; a CO2 gas outlet is set in the blasting hole 2 Burst tube and temperature sensor, CO 2 A bursting tube valve is installed at the gas outlet end of the bursting tube.

[0008] Furthermore, in order to ensure the freezing of liquid nitrogen and the fracturing effect of blasting, the utility model arranges two freezing extraction holes symmetrically on both sides of the blasting hole with the blasting hole as the center, and the distance from the freezing extraction holes on the left and right sides to the blasting hole is set to 2-5m; because liquid nitrogen freezing actually has a maximum freezing range, too large a freezing range will lead to a significant increase in the use of liquid nitrogen, and the effect decreases when the freezing range is greater than 3m; secondly, CO 2 Blasting-induced fracturing may lead to hole collapse. The range of hole collapse varies with different coal seams and is generally 2-5m. Therefore, 2-5m is selected for setting according to local conditions.

[0009] Furthermore, in order to fully freeze and blast the coal seam and better extract gas, the freezing pipe is close to the bottom of the freezing extraction hole, and the extraction pipe is 2-3m away from the bottom of the freezing extraction hole. 2 The blasting tube is 2-3m away from the bottom of the blasting hole.

[0010] Furthermore, in order to better perform blasting fracturing, the length of the grouting and sealing section of the blasting hole is 2-3m longer than the length of the grouting and sealing section of the freezing extraction hole.

[0011] Compared with the prior art, the two freezing extraction holes of the utility model are arranged in the coal seam, and are arranged symmetrically with the blasting hole as the center; the freezing extraction holes are provided with extraction pipes and freezing pipes. In order to ensure that a large amount of liquid nitrogen will not reduce the oxygen concentration of the working face after being gasified into nitrogen, the freezing pipe of the utility model is a U-shaped pipe, which can be used for nitrogen recovery; the liquid inlet of the freezing pipe is connected to the gas outlet of the heat-insulating stainless steel hose, the gas inlet of the heat-insulating stainless steel hose is connected to the liquid nitrogen tank, and a liquid nitrogen distributor is arranged on the heat-insulating stainless steel hose, the liquid nitrogen tank is provided with a pressure monitoring device, a flow monitoring device and a liquid nitrogen tank valve, and a liquid outlet valve is installed at the position of the liquid outlet of the freezing pipe; a CO2 gasket is arranged in the blasting hole. 2 Burst tube and temperature sensor, CO 2 A bursting tube valve is installed at the gas outlet end of the bursting tube; through the above technical scheme, the utility model has the following technical effects:

[0012] 1) Coal body structure reinforcement: Through the low-temperature freezing process, the water inside the coal body freezes and expands in volume, which effectively reinforces the coal body structure and enhances its mechanical strength, making the coal body more stable in subsequent operations;

[0013] 2) Improve the brittleness of coal: The low temperature effect of liquid nitrogen changes the internal microstructure of the coal, and the brittleness of the coal is increased, which makes the subsequent CO 2 In phase change blasting, more cracks can be created in the coal seam, thus improving the efficiency of gas extraction;

[0014] 3) Avoiding hole collapse: The mechanical strength of the coal mass is enhanced to 2 During the phase change blasting process, the hole collapse caused by soft coal quality was effectively avoided, ensuring the safety and efficiency of the blasting operation;

[0015] 4) Improve the fracturing and permeability-enhancing effect: The significant increase in coal brittleness makes CO 2 After blasting, more cracks can be generated in the coal seam, which provide more circulation channels for gas and greatly improve the fracturing and permeability enhancement effect of the coal seam;

[0016] 5) Environmental protection and energy saving: This method uses liquid nitrogen and liquid CO 2 ,Both media are environmentally friendly materials, no pollution is generated during use, and compared with traditional explosives, this method has lower energy consumption;

[0017] 6) Improve gas extraction efficiency: Through precise freezing and blasting treatment, the permeability of the coal seam is improved, which is conducive to gas extraction and improves extraction efficiency and recovery rate;

[0018] 7) Easy and flexible operation: The entire operation process includes freezing, blasting and extraction steps. The steps are clear and the operation is easy. The operating parameters can be flexibly adjusted according to actual conditions to adapt to the mining conditions of different coal seams. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the utility model.

[0020] In the figure: 1. Coal seam, 2. Freezing extraction hole, 3. Blasting hole, 4. Liquid nitrogen tank, 5. Liquid nitrogen tank valve, 6. Insulated stainless steel hose, 7. Liquid inlet, 8. Liquid outlet, 9. Grouting pipe, 10. Grouting pump, 11. Extraction pipe, 12. Freezing pipe, 13. CO 2 blasting tube, 14. blasting tube valve, 15. temperature sensor, 16. grouting and sealing section, 17. pressure monitoring device, 18. flow monitoring device, 19. liquid outlet valve, 20. liquid nitrogen distributor. DETAILED DESCRIPTION

[0021] The utility model will be further described below in conjunction with the accompanying drawings.

[0022] like Figure 1 As shown, a coal seam mechanical modification and permeability enhancement system comprises a blasting hole 3 arranged in a coal seam 1, and the two ends of the blasting hole 3 are respectively arranged in the rock strata on both sides of the coal seam, that is, the blasting hole 3 is arranged through the coal seam 1, and also comprises two freezing extraction holes 2, the two freezing extraction holes 2 are arranged in the coal seam 1, and are arranged symmetrically with the blasting hole 3 as the center; extraction pipes 11 and freezing pipes 12 are arranged in the freezing extraction holes 2, and the extraction pipes 11 are arranged along the center of the freezing extraction holes 2, and the freezing pipes 12 are U-shaped pipes, which are laid along the inner wall of the freezing extraction holes 2; the extraction pipes 11 , the freezing pipe 12 passes through the grouting sealing section 16, one end of the grouting pipe 9 extends into the grouting sealing section 16, and the other end of the grouting pipe 9 is connected to the grouting pump 10; the liquid inlet 7 of the freezing pipe 12 is connected to the air outlet of the heat-insulating stainless steel hose 6, the air inlet of the heat-insulating stainless steel hose 6 is connected to the liquid nitrogen tank 4, and a liquid nitrogen distributor 20 is arranged on the heat-insulating stainless steel hose 6, the liquid nitrogen tank 4 is provided with a pressure monitoring device 17, a flow monitoring device 18 and a liquid nitrogen tank valve 5, and a liquid outlet valve 19 is installed at the position of the liquid outlet 8 of the freezing pipe 12; a CO2 gas is arranged in the blasting hole 3 2 Explosion tube 13 and temperature sensor 15, CO 2 A bursting tube valve 14 is installed at the gas outlet end of the bursting tube 13 .

[0023] The distance between the two freezing extraction holes 2 and the blasting hole 3 is 2-5m.

[0024] The freezing pipe 12 is close to the bottom of the freezing extraction hole 2, and the extraction pipe 11 is 2-3m away from the bottom of the freezing extraction hole 2. 2The blasting tube is 2-3m away from the bottom of the blasting hole 3.

[0025] The length of the grouting and sealing section 16 of the blasting hole 3 is greater than the length of the grouting and sealing section 16 of the freezing extraction hole 2 by 2-3 m.

[0026] In the specific implementation process, firstly, a hole is drilled into the coal seam 1. Since the actual coal seam is often between rock layers, when drilling, it is necessary to first drill into the rock layer, and then drill through the coal seam to reach the rock layer behind the coal seam. Therefore, the bottom of the freezing extraction hole 2 and the blasting hole 3 is actually above the inner rock layer, and the entire coal seam 1 is penetrated.

[0027] In the specific implementation process, gas extraction requires drilling a hole on the coal seam 1, and the gas needs to be extracted through this hole. At the same time, the coal seam needs to be frozen, and a hole is also required for operation. Therefore, in the technical solution of the utility model, the two holes are combined into one, that is, the freezing extraction hole 2 of the utility model has both a freezing pipe and an extraction pipe.

[0028] In the specific implementation process, in order to ensure the freezing of liquid nitrogen and the fracturing effect of blasting, in the technical solution of the utility model, two freezing extraction holes 2 are set symmetrically 2-5m on the left and right of the blasting hole 3. Because liquid nitrogen freezing actually has a maximum freezing range, a large freezing range will lead to a significant increase in the use of liquid nitrogen, and the effect decreases when the freezing range is greater than 3m; secondly, CO 2 Blasting-induced fracturing may lead to hole collapse. The range of hole collapse varies with different coal seams and is generally 2-5m. Therefore, 2-5m is selected for setting according to local conditions.

[0029] In the specific implementation process, in order to ensure that the oxygen concentration on the working surface will not be reduced after a large amount of liquid nitrogen is gasified into nitrogen, the freezing pipe 12 uses a Φ30mm U-shaped seamless hose to recover the nitrogen.

[0030] The specific operation steps of the utility model are as follows:

[0031] 1) Drilling: Drill a blasting hole 3 into the coal seam 1, and drill freezing and extraction holes 2 for freezing and extraction on the left and right sides of the blasting hole 3;

[0032] 2) Water injection: inject a certain amount of water into the two freezing extraction holes 2 to moisten the coal body;

[0033] 3) Establishing a freezing extraction system: inserting the freezing pipe 12 and the extraction pipe 11 into the freezing extraction hole 2;

[0034] 4) Establish CO 2 Blasting system: will be filled with liquid CO 2 CO 2The blasting tube 13 and the temperature sensor 15 extend into the blasting hole 3;

[0035] 5) Sealing holes: arranging grouting pipes 9 at the outer ends of the blasting hole 3 and the two freezing extraction holes 2, and performing grouting and sealing on the blasting hole 3 and the two freezing extraction holes 2 respectively through a grouting pump 10, thereby forming a grouting and sealing hole section 16;

[0036] 6) Freeze the coal seam: Open the valve 5 of the liquid nitrogen tank, and allow the liquid nitrogen in the liquid nitrogen tank 4 to enter the freezing pipe 12 through the non-insulated stainless steel hose 6. The liquid nitrogen gradually vaporizes into nitrogen in the freezing pipe 12, absorbs the heat of the coal seam 1, and freezes the coal seam. When the pressure monitoring device 17 detects that the liquid nitrogen pressure has risen to a certain value, open the liquid outlet valve 19 of the return air part of the freezing pipe 12, and the nitrogen is discharged from the liquid outlet 8 through the freezing pipe 12; the pressure monitoring device 17 is an existing pressure sensor, as long as it can monitor the liquid nitrogen pressure; in addition to using the pressure monitoring device 17 to adjust the liquid nitrogen flow, the utility model can also adjust the amount of liquid nitrogen through the flow monitoring device 18. Similarly, the flow monitoring device 18 is an existing flow monitoring device, as long as it can monitor and adjust the liquid nitrogen flow;

[0037] 7) Blasting: After a certain period of liquid nitrogen freezing, the temperature of the temperature sensor 15 in the blasting hole 3 reaches below -5°C and lasts for more than 30 minutes, then CO 2 Explosion causes cracking. At this time, CO is detonated 2 Liquid CO in blasting tube 13 2 , making liquid CO 2 The phase change from liquid to gas is completed instantly, causing the coal seam to fracture;

[0038] 8) Extraction: within 48 hours after the blasting is completed, close the blasting pipe valve 14; wait for 48 hours before extracting gas through the extraction pipe 11;

[0039] In the specific implementation process, in order to fully freeze and blast the coal seam and better extract gas, the freezing pipe is close to the bottom of the freezing extraction hole, and the CO 2 The blasting tube is 2-3m away from the bottom of the hole, and the extraction tube is 2-3m away from the bottom.

[0040] In the specific implementation process, the purpose of closing the blasting pipe valve for 48 hours is to make the high-pressure CO in the blasting hole 2 The gas fully replaces and displaces CH in the coal 4 , so as to achieve the purpose of strengthening gas extraction, and at the same time make the frozen coal body fully thaw and return to normal temperature, so as to achieve the effect of freeze-thaw cracking of the coal body.

[0041] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A coal seam mechanical modification and permeability enhancement system, comprising a blasting hole (3) arranged in a coal seam (1), characterized in that: It also includes two frozen extraction holes (2), which are arranged in the coal seam (1) and are symmetrically arranged with the blasting hole (3) as the center; an extraction pipe (11) and a freezing pipe (12) are arranged in the frozen extraction holes (2), and the extraction pipe (11) is arranged along the center of the frozen extraction hole (2), and the freezing pipe (12) is a U-shaped pipe, which is laid along the inner wall of the frozen extraction hole (2); the extraction pipe (11) and the freezing pipe (12) both pass through the grouting sealing section (16), one end of the grouting pipe (9) extends into the grouting sealing section (16), and the other end of the grouting pipe (9) is connected to the grouting pump (10); the freezing pipe The liquid inlet (7) of the (12) is connected to the gas outlet of the heat-insulating stainless steel hose (6), the gas inlet of the heat-insulating stainless steel hose (6) is connected to the liquid nitrogen tank (4), and a liquid nitrogen distributor (20) is arranged on the heat-insulating stainless steel hose (6), the liquid nitrogen tank (4) is provided with a pressure monitoring device (17), a flow monitoring device (18) and a liquid nitrogen tank valve (5), and a liquid outlet valve (19) is installed at the position of the liquid outlet (8) of the freezing tube (12); a CO2 blasting tube (13) and a temperature sensor (15) are arranged in the blasting hole (3), and a blasting tube valve (14) is installed at the gas outlet end of the CO2 blasting tube (13).

2. A coal seam mechanical modification and permeability enhancement system according to claim 1, characterized in that: The distance between the two freezing extraction holes (2) and the blasting hole (3) is 2-5m.

3. A coal seam mechanical modification and permeability enhancement system according to claim 1 or 2, characterized in that: The freezing pipe (12) is close to the bottom of the freezing extraction hole (2), the extraction pipe (11) is 2-3m away from the bottom of the freezing extraction hole (2), and the CO2 blasting pipe is 2-3m away from the bottom of the blasting hole (3).

4. A coal seam mechanical modification and permeability enhancement system according to claim 3, characterized in that: The length of the grouting and sealing section (16) of the blasting hole (3) is greater than the length of the grouting and sealing section (16) of the freezing extraction hole (2) by 2-3 m.

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