A gas extraction device and method based on water pressure dissolution of coal seam drilling

Abstract

The present application belongs to the technical field of gas extraction in coal mine, and particularly relates to a gas extraction device and method based on water pressure dissolving in coal seam drilling. The device comprises a clean water pool, a chemical solution pool, a high-pressure hydraulic fracturing pump, a purification pool, a sedimentation and filtration pool, a high-pressure valve, a high-pressure water pipe I and a high-pressure water pipe II. During extraction, drilling holes are first drilled in rock strata and coal seams, the drilling holes penetrate the rock strata and reach the coal seams, high-pressure water is injected into the drilling holes by using the above device, the coal seams are cracked by using the effect of hydraulic fracturing, a gas pressure relief channel is formed in the coal seams, then chemical solution is injected, the chemical solution is closed-loop circulated among the fracturing holes, the hydraulic fracturing paths, the control holes, the sedimentation and filtration pool, the purification pool and the chemical solution pool, the utilization efficiency of the chemical solution is improved, the pollution to the environment is reduced, the release and extraction of the gas are promoted, and in addition, the drilling holes can be used as fracturing holes or control holes, the construction cost is reduced, and the damage to the coal seams is reduced.

Description

Technical Field

[0001] This invention belongs to the field of underground gas extraction technology in coal mines, specifically relating to a gas extraction device and method based on hydraulic pressure-through dissolution of coal seams through boreholes. Background Technology

[0002] Methane gas is one of the major hazards in my country's coal mines, accounting for 46% of all coal mines in the country. Due to the high difficulty and numerous contributing factors to methane gas control, mine methane has always been a key focus and challenge in my country's coal mine safety work. Traditional coalbed methane (CBM) extraction methods involve drilling and drainage, but these methods are costly, inefficient, and cause severe damage to the coal seam. A new technology is needed to improve CBM extraction efficiency and reduce coal seam damage; this is where the hydraulic fracturing and dissolution methane extraction technology comes in. This technology combines the principles of hydraulic fracturing and chemical dissolution. The basic principle is to drill holes in the coal seam and inject high-pressure water, using hydraulic fracturing to break up the coal seam and increase its permeability. Then, chemical solvents are injected to dissolve the substances within the coal seam, thereby promoting the release and extraction of methane.

[0003] Existing coal seam borehole hydraulic pressure-through dissolved gas extraction technology still has some shortcomings:

[0004] (1) Drilling can only be used as fracturing boreholes or control boreholes, which have high construction costs and cause serious damage to coal seams;

[0005] (2) Chemical solvents cannot be recycled, resulting in a waste of resources. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a gas extraction device based on hydraulic fracturing and dissolution of coal seams through boreholes, comprising a clear water tank, a chemical solution tank, a high-pressure hydraulic fracturing pump, a purification tank, a sedimentation and filtration tank, high-pressure valves, a first high-pressure water pipe, a second high-pressure water pipe, fracturing boreholes, and control boreholes.

[0007] Several boreholes are set up in the rock strata and coal seam, and the boreholes penetrate the rock strata to reach the coal seam. Each borehole is equipped with a high-pressure valve. The boreholes serve as fracturing boreholes and control boreholes.

[0008] Furthermore, the distance between two adjacent boreholes is 50m;

[0009] The high-pressure hydraulic fracturing pump is equipped with an inlet and an outlet. The inlet of the high-pressure hydraulic fracturing pump is connected to the clear water tank 1 or the chemical solution tank, and the outlet of the high-pressure hydraulic fracturing pump is connected to the high-pressure water pipe 1.

[0010] The sedimentation and filtration tank is equipped with an inlet, an outlet, a sedimentation zone, and a filtration zone. The inlet of the filtration tank is connected to a high-pressure water pipe. The sedimentation and filtration tank achieves purification through gravity sedimentation and filtration. The chemical solution discharged from the borehole is controlled to enter the sedimentation zone of the filtration tank through the high-pressure water pipe. After sedimentation, the chemical solution is filtered in the filtration zone and flows out from the outlet of the sedimentation and filtration tank.

[0011] The purification tank is equipped with an inlet, an outlet, a physical adsorption zone, and a biodegradation zone. The inlet of the purification tank is connected to the outlet of the sedimentation and filtration tank, and the chemical solution flowing out of the outlet of the filtration tank enters the purification tank through the inlet. The physical adsorption zone is equipped with an adsorption medium to adsorb organic matter and heavy metal ions in the water. The biodegradation zone is equipped with a microbial degradation medium to degrade organic matter into harmless substances. The outlet of the purification tank is connected to the chemical solution tank through a pipe, and the chemical solution after physical adsorption and biodegradation is led into the chemical solution tank.

[0012] The clear water pool contains clear water, and the chemical solution pool contains chemical solution.

[0013] The outlet of the high-pressure hydraulic fracturing pump is also equipped with a pressure and flow regulating valve.

[0014] The sedimentation and filtration tank is also equipped with a sludge discharge port, which is used to discharge the settled sludge and solid particles through the sludge discharge port of the sedimentation and filtration tank.

[0015] Furthermore, the gas extraction device based on coal seam borehole hydraulic pressure penetration and dissolution according to the present invention also includes a slag discharge pool, which is connected to the sludge outlet of the filter pool and is used to collect sludge and solid particles discharged from the sedimentation filter pool.

[0016] The sludge discharge tank is equipped with a sludge inlet and a sludge outlet. The sludge inlet of the sludge discharge tank is connected to the sludge outlet of the sedimentation and filtration tank through a pipeline.

[0017] This invention also provides a gas extraction method based on hydraulic pressure-through dissolution in coal seam boreholes, comprising the following steps:

[0018] Step 1: Drill several holes in the rock strata and coal seam, with the holes penetrating the rock strata to reach the coal seam. The number of holes is set according to the length of the coal seam. After drilling is completed, the holes are sealed according to the requirements of high-pressure hydraulic fracturing. After sealing, a high-pressure valve is set for each hole and all high-pressure valves are closed.

[0019] Step 2: Select the first borehole as the fracturing borehole and the second borehole as the control borehole. Connect one end of the high-pressure water pipe to the fracturing borehole, one end of the second high-pressure water pipe to the control borehole, and the other end of the second high-pressure water pipe to the sedimentation and filtration tank. Open the valves of the fracturing borehole and the control borehole. Connect the inlet of the high-pressure hydraulic fracturing pump to the clear water tank through a pipe. Start the high-pressure hydraulic fracturing pump. When the working pressure of the high-pressure hydraulic fracturing pump is greater than the coal seam pressure, the coal seam begins to fracture. A hydraulic fracturing path is formed in the coal seam between the fracturing borehole and the control borehole. High-pressure water is rapidly injected and then released from the control borehole.

[0020] Step 3: Transfer the inlet of the high-pressure hydraulic fracturing pump from the clear water tank to the chemical solution tank, and simultaneously connect the second high-pressure water pipe to the sedimentation and filtration tank; the high-pressure hydraulic fracturing pump injects the chemical solution from the fracturing borehole, flows out from the control borehole, and then flows into the sedimentation and filtration tank through the second high-pressure water pipe; the chemical solution after sedimentation and filtration in the sedimentation and filtration tank is introduced into the purification tank; the chemical solution after physical adsorption and biodegradation in the purification tank is introduced into the chemical solution tank;

[0021] Step 4: Repeat step 3, with the chemical solution circulating in a closed loop between the fracturing borehole, the hydraulic fracturing pathway and control borehole, the sedimentation and filtration tank, the purification tank and the chemical solution tank;

[0022] Step 5: Transfer the inlet of the high-pressure hydraulic fracturing pump from the chemical solution pool to the clear water pool to clean the hydraulic fracturing path between the fracturing borehole and the control borehole. After visually inspecting that the outflowing water is clear and free of impurities, close the high-pressure hydraulic fracturing pump and all high-pressure valves.

[0023] Step 6: Use the second borehole as a fracturing borehole and the third borehole as a control borehole. Repeat steps 2 to 5, and replace the fracturing borehole and control borehole in turn for hydraulic pressure penetration and dissolution treatment until all boreholes in the coal seam have been pressure penetrated and dissolved, and each borehole is interconnected.

[0024] Furthermore, in step 4, the chemical solution is circulated in a closed loop between the fracturing borehole, the hydraulic fracturing pathway and the control borehole, the sedimentation and filtration tank, the purification tank and the chemical solution tank, with a circulation time of 4 hours.

[0025] Furthermore, in step 5, the time for cleaning the hydraulic fracturing pathway between the fracturing borehole and the control borehole is 30 minutes.

[0026] The beneficial effects of this invention are:

[0027] This invention provides a gas extraction device and method based on hydraulic fracturing and dissolution of coal seams through boreholes. By drilling holes in the coal seam and injecting high-pressure water, the coal seam is fractured using hydraulic fracturing, forming a gas depressurization channel within the coal seam, thus improving gas extraction efficiency and coal seam permeability. A chemical solution is then injected, and a high-pressure hydraulic fracturing pump is used to create a closed-loop circulation of the chemical solution between the fracturing borehole, the hydraulic fracturing path, the control borehole, the sedimentation and filtration tank, the purification tank, and the chemical solution tank. This improves the utilization efficiency of the chemical solution, reduces environmental pollution, and promotes gas release and extraction. Furthermore, the boreholes in this invention can serve as both fracturing boreholes and control boreholes, reducing construction costs and minimizing damage to the coal seam. Attached Figure Description

[0028] Figure 1 Schematic diagram of a gas extraction device and method based on hydraulic pressure-break dissolution in coal seam boreholes.

[0029] The attached diagram is labeled as follows: 1. Clear water tank; 2. Chemical solution tank; 3. High-pressure hydraulic fracturing pump; 4. Pressure and flow regulating valve; 5. Purification tank; 6. Sedimentation and filtration tank; 7. Slag discharge tank; 8. Fracturing borehole; 9. Control borehole; 10. Rock stratum; 11. Coal seam; 12. Hydraulic fracturing path; 13. High-pressure valve; 14. High-pressure water pipe one; 15. High-pressure water pipe two. Detailed Implementation

[0030] The embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0031] See Figure 1 The present invention provides a gas extraction device based on hydraulic pressure-break dissolution in coal seam drilling, including a clear water tank 1, a chemical solution tank 2, a high-pressure hydraulic fracturing pump 3, a pressure and flow regulating valve 4, a purification tank 5, a sedimentation and filtration tank 6, a slag discharge tank 7, a high-pressure valve 13, a high-pressure water pipe 14, and a high-pressure water pipe 2 15.

[0032] In the rock stratum 10 and coal seam 11, a borehole is drilled every 50 meters. The borehole penetrates the rock stratum 10 to reach the coal seam 11. The number of boreholes is set according to the length of the coal seam. After the boreholes are completed, they are sealed according to the requirements of high-pressure hydraulic fracturing. After sealing, each borehole is equipped with a high-pressure valve 13. The boreholes serve as fracturing boreholes 8 and control boreholes 9.

[0033] Clear water pool 1 contains clear water, and chemical solution pool 2 contains chemical solution.

[0034] The high-pressure hydraulic fracturing pump 3 is equipped with an inlet and an outlet. The outlet of the high-pressure hydraulic fracturing pump 3 is equipped with a pressure and flow regulating valve 4. The inlet of the high-pressure hydraulic fracturing pump 3 is connected to the clear water tank 1 or the chemical solution tank 2. The outlet of the high-pressure hydraulic fracturing pump 3 is connected to the high-pressure water pipe 14. When the high-pressure hydraulic fracturing pump 3 is working, it pressurizes the clear water in the clear water tank 1 or the chemical solution in the chemical solution tank 2 into the fracturing borehole 8. The pressure of the chemical solution is regulated by the flow regulating valve 4.

[0035] The sedimentation filter tank 6 is equipped with an inlet, an outlet, a sludge discharge outlet, a sedimentation zone, and a filtration zone. The inlet of the sedimentation filter tank 6 is connected to a high-pressure water pipe 15. The sedimentation filter tank 6 achieves purification through gravity sedimentation and filtration. The chemical solution discharged from the control borehole 9 enters the sedimentation zone of the sedimentation filter tank 6 through the high-pressure water pipe 15. The suspended matter in the chemical solution settles under gravity. The settled sludge and solid particles are discharged through the sludge discharge outlet of the sedimentation filter tank 6. The settled chemical solution is further filtered through the filtration zone to remove fine particles and organic matter. Finally, the clean chemical solution flows out from the outlet of the sedimentation filter tank 6.

[0036] The sludge discharge tank 7 is equipped with a sludge inlet and a sludge outlet for collecting sludge and solid particles discharged from the sedimentation and filtration tank 6. The sludge inlet of the sludge discharge tank 7 is connected to the sludge outlet of the sedimentation and filtration tank 6 through a pipeline, so that the sludge and solid particles settled in the sedimentation and filtration tank 6 are introduced into the sludge discharge tank 7. When the sludge discharge tank 7 is full, the sludge and solid particles are discharged through the sludge outlet.

[0037] The purification tank 5 is equipped with an inlet, an outlet, a physical adsorption zone, and a biodegradation zone. The inlet of the purification tank 5 is connected to the outlet of the sedimentation and filtration tank 6, and the chemical solution flowing out of the outlet of the sedimentation and filtration tank 6 enters the purification tank 5 through the inlet of the purification tank 5. The physical adsorption zone is equipped with an adsorption medium to adsorb organic matter and heavy metal ions in the water. The biodegradation zone is equipped with a microbial degradation medium to degrade organic matter into harmless substances. The outlet of the purification tank 5 is connected to the chemical solution tank 2 through a pipe, and the chemical solution after physical adsorption and biodegradation is led into the chemical solution tank 2.

[0038] This invention also provides a gas extraction method based on hydraulic pressure-through dissolution in coal seam boreholes, the specific operation steps of which are as follows:

[0039] Step 1: Drill a hole every 50m in the rock stratum 10 and coal seam 11. The hole should penetrate the rock stratum 10 and reach the coal seam 11. The number of holes should be set according to the length of the coal seam. After drilling is completed, the holes should be sealed according to the requirements of high-pressure hydraulic fracturing. After sealing, a high-pressure valve 13 should be set in each hole and all high-pressure valves 13 should be closed.

[0040] Step 2: Select the first borehole as the fracturing borehole 8 and the second borehole as the control borehole 9. Connect the first high-pressure water pipe 14 to the fracturing borehole 8, connect one end of the second high-pressure water pipe 15 to the control borehole 9, and connect the other end of the second high-pressure water pipe 15 to the sedimentation and filtration tank 6. Open the valve 13 of the fracturing borehole 8 and the control borehole 9. Connect the inlet of the high-pressure hydraulic fracturing pump 3 to the clear water tank 1 through the pipe. Start the high-pressure hydraulic fracturing pump 3 and adjust the pressure and flow regulating valve 4. When the working pressure of the high-pressure hydraulic fracturing pump 3 is greater than the coal seam pressure, the coal seam begins to fracture. The coal seam between the fracturing borehole 8 and the control borehole 9 forms a hydraulic fracturing path 12. High-pressure water is rapidly injected and then released from the control borehole 9.

[0041] Step 3: Transfer the inlet of the high-pressure hydraulic fracturing pump 3 from the clear water tank 1 to the chemical solution tank 2, and connect the high-pressure water pipe 2 (15) to the sedimentation and filtration tank 6. The high-pressure hydraulic fracturing pump 3 injects the chemical solution from the fracturing borehole 8. The chemical solution passes through the fracturing path 12 and dissolves some substances in the coal seam. It flows out from the control borehole 9 and then flows into the sedimentation and filtration tank 6 through the high-pressure water pipe 2 (15). The chemical solution after sedimentation and filtration in the sedimentation and filtration tank 6 is introduced into the purification tank 5, and the sludge and solid particles are introduced into the slag discharge tank 7. The chemical solution after physical adsorption and biodegradation in the purification tank 5 is introduced into the chemical solution tank 2.

[0042] Step 4: Repeat step 3. The chemical solution circulates in a closed loop between fracturing borehole 8, hydraulic fracturing path 12, control borehole 9, sedimentation and filtration tank 6, purification tank 5, and chemical solution tank 2 for 4 hours. This is equivalent to soaking and dissolving the coal seam 11 through which it flows for 4 hours with the chemical solution, and carrying out the dissolved substances. This forms a chemical solution transport channel and a gas depressurization channel in the coal seam 11, which effectively increases the permeability coefficient of the coal seam.

[0043] Step 5: Transfer the inlet of the high-pressure hydraulic fracturing pump 3 from the chemical solution tank 2 to the clear water tank 1 to clean the hydraulic fracturing path 12 between the fracturing borehole 8 and the control borehole 9. Clean for 30 minutes. After visually inspecting that the outflowing water is clear and free of impurities, turn off the high-pressure hydraulic fracturing pump 3 and close all high-pressure valves 13.

[0044] Step 6: Use the second borehole as fracturing borehole 8 and the third borehole as control borehole 9. Repeat steps 2 to 5, and replace fracturing borehole 8 and control borehole 9 in turn for hydraulic pressure penetration and dissolution treatment until all boreholes in coal seam 11 have been pressure penetrated and dissolved, and each borehole is interconnected.

[0045] This invention involves drilling holes in coal seam 11 and injecting high-pressure water to hydraulically fracturing the coal seam 11, creating a gas decompression channel within it. This improves gas extraction efficiency and coal seam permeability. A chemical solution is then injected, and a high-pressure hydraulic fracturing pump 3 ensures a closed-loop circulation of the chemical solution between the fracturing borehole 8, the hydraulic fracturing path 12, the control borehole 9, the sedimentation and filtration tank 6, the purification tank 5, and the chemical solution tank 2. This improves the utilization efficiency of the chemical solution, reduces environmental pollution, and promotes gas release and extraction. Furthermore, the boreholes in this invention can serve as both fracturing boreholes 8 and control boreholes 9, reducing construction costs and minimizing damage to the coal seam.

Claims

1. A gas extraction method based on hydraulic pressure-through dissolution in coal seam boreholes, implemented using a gas extraction device, characterized in that, Includes the following steps: Step 1: Drill several holes in the rock strata (10) and coal seam (11). The holes penetrate the rock strata to reach the coal seam. After the holes are completed, seal them according to the requirements of high-pressure hydraulic fracturing. After sealing, set a high-pressure valve (13) for each hole and close all high-pressure valves (13). Step 2: Select the first borehole as the fracturing borehole (8) and the second borehole as the control borehole (9). Connect the first high-pressure water pipe (14) to the fracturing borehole (8), connect one end of the second high-pressure water pipe (15) to the control borehole (9), and connect the other end of the second high-pressure water pipe (15) to the sedimentation filter tank (6). Open the valves (13) of the fracturing borehole (8) and the control borehole (9). Connect the inlet of the high-pressure hydraulic fracturing pump (3) to the clear water tank (1) through the pipe. Start the high-pressure hydraulic fracturing pump (3). When the working pressure of the high-pressure hydraulic fracturing pump (3) is greater than the coal seam pressure, the coal seam begins to fracture. The coal seam (11) between the fracturing borehole (8) and the control borehole (9) forms a hydraulic fracturing path (12). High-pressure water is rapidly injected and released from the control borehole (9). Step 3: Transfer the inlet of the high-pressure hydraulic fracturing pump (3) from the clear water tank (1) to the chemical solution tank (2), and connect the high-pressure water pipe (15) to the sedimentation and filtration tank (6); the high-pressure hydraulic fracturing pump (3) pressurizes the chemical solution into the fracturing borehole (8), flows out from the control borehole (9), and then flows into the sedimentation and filtration tank (6) through the high-pressure water pipe (15); the chemical solution after sedimentation and filtration in the sedimentation and filtration tank (6) is introduced into the purification tank (5); the chemical solution after physical adsorption and biodegradation in the purification tank (5) is introduced into the chemical solution tank (2). Step 4: Repeat step 3, with the chemical solution circulating in a closed loop between the fracturing borehole (8), the hydraulic fracturing path (12), the control borehole (9), the sedimentation and filtration tank (6), the purification tank (5), and the chemical solution tank (2); Step 5: Transfer the inlet of the high-pressure hydraulic fracturing pump (3) from the chemical solution pool (2) to the clear water pool (1) to clean the hydraulic fracturing path (12) between the fracturing borehole (8) and the control borehole (9). After visually inspecting that the outflowing water is clear and free of impurities, close the high-pressure hydraulic fracturing pump (3) and all high-pressure valves (13). Step 6: Use the second borehole as the fracturing borehole (8) and the third borehole as the control borehole (9). Repeat steps 2 to 5, and replace the fracturing borehole (8) and the control borehole (9) in turn for hydraulic pressure penetration and dissolution treatment until all boreholes in the coal seam (11) have been pressure penetrated and dissolved, and each borehole is interconnected. The gas extraction device includes a clear water tank (1), a chemical solution tank (2), a high-pressure hydraulic fracturing pump (3), a purification tank (5), a sedimentation and filtration tank (6), a high-pressure valve (13), a high-pressure water pipe I (14), a high-pressure water pipe II (15), a fracturing borehole (8), and a control borehole (9). Several boreholes are set in the rock strata (10) and coal seam (11). The boreholes penetrate the rock strata (10) and reach the coal seam (11). Each borehole is equipped with a high-pressure valve (13). The boreholes serve as fracturing boreholes (8) and control boreholes (9). The high-pressure hydraulic fracturing pump (3) is equipped with an inlet and an outlet. The inlet of the high-pressure hydraulic fracturing pump (3) is connected to the clear water tank (1) or the chemical solution tank (2). The outlet of the high-pressure hydraulic fracturing pump (3) is connected to the high-pressure water pipe (14). The sedimentation filter tank (6) is equipped with an inlet, an outlet, a sedimentation zone, and a filtration zone. The inlet of the sedimentation filter tank (6) is connected to a high-pressure water pipe (15). The sedimentation filter tank (6) achieves purification treatment through gravity sedimentation and filtration. The chemical solution discharged from the control borehole (9) enters the sedimentation zone of the sedimentation filter tank (6) through the high-pressure water pipe (15). After sedimentation, the chemical solution is filtered through the filtration zone and flows out from the outlet of the sedimentation filter tank (6). The purification tank (5) is equipped with an inlet, an outlet, a physical adsorption zone, and a biodegradation zone. The inlet of the purification tank (5) is connected to the outlet of the sedimentation filter tank (6), and the chemical solution flowing out of the outlet of the sedimentation filter tank (6) enters the purification tank (5) through the inlet of the purification tank (5). An adsorption medium is set in the physical adsorption zone to adsorb organic matter and heavy metal ions in the water. A microbial degradation medium is set in the biodegradation zone to degrade organic matter into harmless substances. The outlet of the purification tank (5) is connected to the chemical solution tank (2) through a pipe, and the chemical solution after physical adsorption and biodegradation is introduced into the chemical solution tank (2). The clear water pool (1) contains clear water, and the chemical solution pool (2) contains chemical solution.

2. The gas extraction method based on hydraulic pressure-through dissolution in coal seam boreholes according to claim 1, characterized in that: In step 4, the chemical solution is circulated in a closed loop for 4 hours between the fracturing borehole (8), the hydraulic fracturing path (12), the control borehole (9), the sedimentation and filtration tank (6), the purification tank (5), and the chemical solution tank (2).

3. The gas extraction method based on hydraulic pressure-through dissolution in coal seam boreholes according to claim 1, characterized in that: The time for cleaning the hydraulic fracturing path (12) between the fracturing borehole (8) and the control borehole (9) in step 5 is 30 minutes.

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