A high-voltage electrical pulse-assisted acid fracturing coal seam permeability enhancement device and method

Abstract

This invention discloses a high-voltage electric pulse synergistic acid fracturing coal seam permeability enhancement device and method, including a sealing device, a high-voltage acid injection pipe, an expansion capsule sleeved in the middle of the high-voltage acid injection pipe, fixed ends at both ends of the expansion capsule, a connecting pipe at the rear end of the high-voltage acid injection pipe, and a pair of high-voltage electrodes, each including a high-voltage electrode A section and a high-voltage electrode B section. Mounting holes are radially arranged on both sides of the fixed ends at the front ends, and springs are fixedly installed at the bottom of the mounting holes. Both high-voltage electrode A sections penetrate the expansion capsule, and their front ends abut against the high-voltage electrode B section to achieve electrical connection. The rear ends of the high-voltage electrode A sections are connected to a pulse circuit. This method first dissolves minerals with acid fracturing fluid, clearing the coal seam pore and fracture network, reducing the difficulty of subsequent high-voltage electric pulse discharge, and then performs high-voltage pulse discharge for fracturing, ensuring the efficiency of coal and rock fracturing.

Description

Technical Field

[0001] This invention relates to the field of coal seam fracturing technology, specifically to a high-voltage electrical pulse-assisted acid fracturing coal seam permeability enhancement device and method. Background Technology

[0002] The development and utilization of coalbed methane is of great strategic significance for both safe coal mining and environmental protection. This is not only because methane has a high calorific value and produces relatively little exhaust gas, making it a highly efficient and clean energy source, but more importantly, it is also a major source of mine accidents during coal mining. Furthermore, methane released into the atmosphere is a greenhouse gas, causing air pollution. However, low permeability is a common problem in Chinese coal seams, making methane extraction difficult. Therefore, effectively enhancing coal seam permeability using artificial permeability enhancement techniques is of profound significance for achieving efficient coalbed methane extraction and fully realizing the value of coal resources.

[0003] To improve the conductivity and permeability of coal seams, the industry has long researched and proposed various methods for enhancing coal seam permeability, including borehole decompression, hydraulic fracturing, CO2 fracturing, and deep-hole pre-fracturing controlled blasting. Among these, borehole decompression can only extract one atmosphere of gas in low-permeability coal seams, resulting in low gas extraction efficiency. Hydraulic fracturing is highly effective for bright coals with well-developed fractures, high brittleness, and high strength, but it is not suitable for soft coal seams with poor joint development and low brittleness. CO2 fracturing is costly when applied at depths and carries the risk of coal and gas outbursts due to CO2 oversaturation. Pre-fracturing controlled blasting is effective in high-strength hard coals, but may cause secondary disasters in soft coal seams.

[0004] CN118462127A discloses a method for indirect fracturing of coal seams using high-voltage electric pulse combined with hydraulic fracturing. The method involves arranging horizontal wells in a hard roof, using high-voltage electric pulses to penetrate the roof and coal seam to form high-voltage electric pulse fracturing fractures, and then using horizontal well segmented fracturing technology to fracture the coal seam, forming a complex fracturing network within the coal seam.

[0005] CN107630717B discloses a method for enhancing coal seam permeability by combining electrical pulses with coal seam water injection. This method enhances the conductivity of the coal body by injecting ionized water into the coal seam, and then uses high-voltage electrical pulses to fracture the coal body, thereby creating fissures within the coal body and increasing the gas extraction rate per hole.

[0006] While the above methods are dedicated to enhancing the effect of high-voltage electric pulse technology, they cannot fundamentally solve the technical problem of high field strength in coal body breakdown caused by low conductivity of coal seams. Furthermore, simply using hydraulic or conductive ion solutions as mediums to improve the conductivity of coal seams is insufficient to effectively dissolve the pore and fracture structures filled with minerals in the coal seam. Summary of the Invention

[0007] This invention aims to solve the technical problems existing in the prior art. In particular, it innovatively proposes a high-voltage electric pulse synergistic acid fracturing coal seam permeability enhancement device and method, which can first dissolve minerals with acid fracturing fluid to clear the coal seam pore and fracture network, reduce the difficulty of subsequent high-voltage electric pulse discharge, and then perform high-voltage pulse discharge to induce fracturing, thus ensuring the efficiency of coal and rock fracturing.

[0008] To achieve the above objectives, the present invention provides a high-voltage electric pulse-assisted acid fracturing coal seam permeability enhancement device, comprising a sealing device for embedding in a fracturing permeation working hole, the sealing device comprising a high-voltage acid injection pipe, an expansion capsule sleeved in the middle of the high-voltage acid injection pipe, fixed ends provided at both ends of the expansion capsule, and both ends of the high-voltage acid injection pipe extending beyond the fixed ends, the rear end of the high-voltage acid injection pipe being connected to an acid fracturing fluid supply system via a connecting pipe;

[0009] It also includes a pair of high-pressure electrodes respectively disposed on both sides of the high-pressure acid injection pipeline. Each high-pressure electrode includes a high-pressure electrode A section extending axially along the high-pressure acid injection pipeline and a high-pressure electrode B section extending radially along the high-pressure acid injection pipeline. The fixed end at the front end is provided with mounting holes on both sides radially for accommodating the high-pressure electrode B section. A spring is fixedly disposed at the bottom of the mounting hole. The high-pressure electrode B section is fixed together with the spring, so that the outer end of the high-pressure electrode B section is pressed against the inner wall of the fracturing and permeation operation hole. Both high-pressure electrode A sections penetrate the expansion capsule. The front ends of the two high-pressure electrode A sections extend into the mounting holes on both sides of the fixed end at the front end and abut against the high-pressure electrode B section to achieve electrical connection. The rear end of the high-pressure electrode A section passes through the fixed end at the rear end of the high-pressure acid injection pipeline and is connected to the pulse circuit.

[0010] In the above scheme: the expansion capsule is equipped with an insulating oil supply system, and expands by injecting insulating oil into the expansion capsule. The use of insulating oil can prevent other parts from conducting electricity, ensuring that the current flows only from the high-voltage electrode A section and the high-voltage electrode B section, and is released from the high-voltage electrode B section, thus ensuring the range of pulse voltage action.

[0011] In the above scheme: a shut-off valve is installed on the connecting pipe outside the fracturing permeation operation hole to prevent acid fracturing fluid from flowing out of the connecting pipe and to ensure the acid fracturing effect.

[0012] In the above scheme: a non-detachment groove is provided on the side of the high-voltage electrode section B near the high-voltage electrode section A, extending radially along the fixed end, and the front end of the high-voltage electrode section A extends into the non-detachment groove. This prevents the high-voltage electrode section B from detaching and also ensures that the high-voltage electrode section A and the high-voltage electrode section B abut against each other, thus guaranteeing the stability of the electrical connection.

[0013] In the above scheme: the high-voltage electrode A section and the high-voltage electrode B section are both made of Cu-Cr-Zr alloy as the substrate, and the surfaces of the high-voltage electrode A section and the high-voltage electrode B section are coated with CrN coating.

[0014] This invention provides a method for enhancing the permeability of coal seams through high-voltage electrical pulse-assisted acid fracturing, comprising the sealing device described in the above scheme, and further comprising the following steps:

[0015] Step 1: Select acetic acid as the acidizing fracturing fluid and store the acidizing fracturing fluid in the mixing tank;

[0016] Step 2: Arrange multiple parallel fracturing and permeation operation holes in the target coal seam roadway, with a spacing of 3~5m between the fracturing and permeation operation holes;

[0017] Step 3: Place a sealing device into each fracturing and penetration well. Insulating oil is injected into the expansion capsule through the insulating oil supply system to make the expansion capsule completely fit the well wall and complete the sealing.

[0018] Step 4: Connect each perforator to the acidizing fracturing fluid supply system; the acidizing fracturing fluid supply system includes a fracturing pump whose inlet is connected to the mixing tank, and the outlet of the fracturing pump is connected to the connecting flange through a fracturing fluid pipeline. The fracturing fluid pipeline is equipped with a filter, a hydraulic pressure gauge, a fluid mass flow meter, and a throttle valve.

[0019] Step 5: Turn on the fracturing pump to pump the fracturing fluid from the mixing tank and deliver it to the high-pressure acid injection pipeline, thereby injecting the fracturing fluid into the fracturing permeation working hole;

[0020] Step 6: Stop the fracturing pump, close the shut-off valve, remove the connecting flange, disconnect the fracturing fluid injection, and allow the fracturing fluid to remain under pressure in the coal seam for a certain period of time to complete the acid fracturing operation;

[0021] Step 7: After completing the acid fracturing operation, connect the sealing device to the pulse circuit;

[0022] The pulse circuit includes a capacitor module. The positive terminal of the capacitor module is connected to a positive circuit, which is used to electrically connect the sealing device to the positive terminal of the capacitor module. A discharge switch is provided on the positive circuit, and the controlled end of the discharge switch is connected to a charge / discharge controller. The negative terminal of the capacitor module is connected to a negative circuit, which is used to electrically connect the sealing device to the negative terminal of the capacitor module. An oscilloscope is provided on the negative circuit.

[0023] When connecting the pulse circuit, two adjacent sealing devices are used as a group. The two sealing devices in the same group are connected to the positive circuit and the negative circuit respectively, and they are connected to the same positive circuit or negative circuit as the other adjacent sealing device.

[0024] Step 8: Perform the first discharge; close the discharge switch by operating the charge / discharge controller to perform the first discharge;

[0025] Step 9: Observe the current and voltage curves acquired by the oscilloscope to determine the effect of the high-voltage pulse discharge. If the discharge effect is not achieved, repeat step 8 until the discharge effect is met.

[0026] Step 10: Switch the circuit; switch the odd-numbered or even-numbered sealing device to be connected to the positive circuit or the negative circuit, and make the two sealing devices in the same group connected to the same positive circuit or negative circuit, and connect to the positive circuit and the negative circuit respectively with another adjacent sealing device.

[0027] Step 11: Perform the second discharge. Close the discharge switch by operating the charge and discharge controller to perform the second discharge. Observe the current and voltage curves collected by the oscilloscope to judge the effect of the high voltage pulse discharge. If the discharge effect is not achieved, repeat this step until the discharge effect is satisfied.

[0028] Step 12: Push the sealing device toward the bottom of the fracturing and permeation working hole, and repeat steps 8 to 11 to achieve single and / or repeated high-voltage electric pulse discharge at different points in the same borehole;

[0029] Step 13: Release the residual electrical energy in the capacitor module to complete the high-voltage pulse discharge operation.

[0030] Step 14: Extract the insulating oil from the expansion capsule, remove the sealing device, and complete the high-voltage electric pulse-assisted acid fracturing coal seam permeability enhancement operation.

[0031] In the above scheme: the capacitor module is equipped with a capacitor protection module, the charging end of the capacitor module is connected to one end of the charging protection module, and the other end of the charging protection module is connected to the power supply.

[0032] In the above scheme, step 8 also includes the following steps:

[0033] Before discharging, check that the capacitor protection module and charging protection module are properly connected to the capacitor module. Turn on the power and charge the capacitor module through the power supply. After the voltage inside the capacitor module reaches the set value, then discharge.

[0034] In summary, the beneficial effects of this invention are as follows: the sealing device can perform both acid fracturing and pulse circuit release, offering multiple functions and fulfilling the technical requirement of integrated "acid fracturing-high voltage discharge"; the high-voltage electrode B section on both sides forms a dual-electrode structure, capable of releasing pulse voltage to both sides of the fracturing and penetration hole, and connecting with the sealing device on one side to form a circuit, thereby achieving secondary fracturing of the coal seam through pulse voltage. Simultaneously, by combining the fracturing coal seam permeability enhancement method and replacing the electrode, a circuit can be formed by connecting with the sealing device on the other side, limiting the fracturing range of the pulse voltage and ensuring the fracturing efficiency of the coal seam, avoiding the formation of fracturing dead zones in certain locations; furthermore, the spring allows the high-voltage electrode B section to have a certain amount of free extension and contraction, effectively contacting the borehole wall and enhancing the high-voltage pulse discharge effect.

[0035] The acid fracturing fluid can dissolve coal minerals, initially clear pores and fractures, and improve the electrical conductivity of the coal, effectively reducing the difficulty of coal seam penetration. On this basis, the application of high-voltage electric pulse technology can not only further expand the pores and fractures formed by acid fracturing to form a complex fracture network, enhancing the effect of high-voltage electric pulse technology, but also effectively weaken the potential impact of acid fracturing reaction products blocking the channels. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of a high-voltage electric pulse synergistic acid fracturing coal seam permeability enhancement device according to the present invention.

[0037] Figure 2 yes Figure 1 Enlarged diagram of point A in the middle.

[0038] Figure 3 This is a schematic diagram of the connection between the acid fracturing fluid supply system and the high-voltage electric pulse-assisted acid fracturing coal seam permeability enhancement method of the present invention.

[0039] Figure 4 This is a schematic diagram of the connection of the pulse circuit in the high-voltage electric pulse synergistic acid fracturing coal seam permeability enhancement method of the present invention.

[0040] Figure 5 This is a schematic diagram of the circuit connection during two high-voltage electric pulse operations in the present invention, which describes a high-voltage electric pulse synergistic acid fracturing coal seam permeability enhancement method. Detailed Implementation

[0041] The present invention will be further described below with reference to the embodiments and accompanying drawings:

[0042] like Figures 1-5 As shown, a method for enhancing the permeability of coal seams through high-voltage electrical pulse-assisted acid fracturing includes the following steps:

[0043] Step 1: Prepare the acidizing fracturing fluid according to the minerals contained in the target coal seam 1, and store the acidizing fracturing fluid in the mixing tank 15. Acetic acid (CH3COOH) is selected as the working fluid for acidizing fracturing. Specifically, this invention uses acetic acid (CH3COOH) as the working fluid because the acid has weak ionization and a slow reaction, which can significantly extend the effective radius of action. Furthermore, acetic acid reacts with iron mineral nodules in the coal to form complexes, effectively avoiding the risk of secondary precipitation. The free metal ions generated during the dissolution process can significantly improve the conductivity of the reservoir medium, forming a synergistic mechanism with the high-voltage electric pulse technology to improve discharge efficiency. The cavitation effect generated by the electric pulse can also promote acid diffusion and penetration. The two work together through electro-chemical-mechanical multi-field coupling to produce a synergistic effect.

[0044] Step 2: Arrange multiple parallel fracturing and permeation working holes 2 in the roadway of the target coal seam 1. The spacing between the fracturing and permeation working holes 2 is 3~5m. To ensure the acidizing effect, it is recommended that the working hole depth be no less than 80m, the hole diameter be no less than 100mm, and the sealing depth be no less than 16m.

[0045] Step 3: Place a sealing device 4 into each fracturing and penetration working hole 2, and inject insulating oil into the expansion capsule 43 through the insulating oil supply system to make the expansion capsule 43 completely fit the hole wall and complete the sealing.

[0046] The sealing device 4 is used to be embedded in the fracturing permeation working hole 2, and includes a high-pressure acid injection pipe 44, with an expansion capsule 43 sleeved in the middle of the high-pressure acid injection pipe 44. The expansion capsule 43 is equipped with an insulating oil supply system and expands by injecting insulating oil into the expansion capsule 43. Both ends of the expansion capsule 43 are provided with fixed ends 42, and both ends of the high-pressure acid injection pipe 44 extend beyond the fixed ends 42. The rear end of the high-pressure acid injection pipe 44 is provided with a connecting pipe for communicating with the acidizing fracturing fluid supply system, and the rear end of the connecting pipe is provided with a connecting flange 6 for connecting with the acidizing fracturing fluid supply system. A shut-off valve 5 is provided on the connecting pipe located outside the fracturing permeation working hole 2.

[0047] A pair of high-pressure electrodes are respectively arranged on both sides of the high-pressure acid injection pipe 44. Each high-pressure electrode includes a high-pressure electrode section A 45 extending axially along the high-pressure acid injection pipe 44 and a high-pressure electrode section B 46 extending radially along the high-pressure acid injection pipe 44. Mounting holes for accommodating high-pressure electrode section B 46 are provided on both sides of the fixed end 42 at the front end, and the outer end of high-pressure electrode section B 46 is always located outside the mounting hole. A spring 47 is fixedly installed at the bottom of the mounting hole, and high-pressure electrode section B 46 is fixed together with the spring 47, so that the outer end of high-pressure electrode section B 46 is pressed against the inner wall of the fracturing and permeation working hole 2. High-pressure electrode sections A 45 both penetrate the expansion capsule 43. The front ends of the two high-pressure electrode sections A 45 extend into the mounting holes on both sides of the fixed end 42 at the front end and abut against high-pressure electrode section B 46 to achieve electrical connection. The rear ends of high-pressure electrode sections A 45 pass through the fixed end 42 at the rear end of the high-pressure acid injection pipe 44 and are connected to the pulse circuit.

[0048] The two high-voltage electrodes A section 45 on the sealing device 4 are fixed together by the same conductive copper clip 41, which is used to connect the pulse circuit.

[0049] A non-slip groove 46a is provided on the side of the high-voltage electrode section B 46 near the high-voltage electrode section A 45, extending radially along the fixed end 42. The front end of the high-voltage electrode section A 45 extends into the non-slip groove 46a. The non-slip groove 46a is used to prevent the high-voltage electrode section B 46 from sliding out of the mounting holes on both sides of the fixed end 42.

[0050] Furthermore, both high-voltage electrode section A 45 and high-voltage electrode section B 46 are made of Cu-Cr-Zr alloy as the base material, and the surfaces of high-voltage electrode section A 45 and high-voltage electrode section B 46 are coated with a 3μm thick CrN coating through PVD process, ensuring high conductivity, high temperature resistance and acid corrosion resistance of the electrode material, and the cost is relatively low, which has good engineering promotion value.

[0051] Step 4: Connect each sealing device 4 to the acidizing fracturing fluid supply system; the acidizing fracturing fluid supply system includes a fracturing pump 14 whose inlet is connected to the mixing tank 15, and the outlet of the fracturing pump 14 is connected to the connecting flange 6 through the fracturing fluid pipeline 7. The fracturing fluid pipeline 7 is equipped with a filter 13, a hydraulic pressure gauge 12, a fluid mass flow meter 11 and a throttle valve 10 in sequence along the liquid flow direction. The front end of the fracturing fluid pipeline 7 is also equipped with a connecting flange 6 for connecting to the connecting flange 6 of the connecting pipe.

[0052] Step 5: Turn on the fracturing pump 14 to pump the fracturing fluid from the mixing tank 15 and through the fracturing pump 14, filter 13, throttle valve 10, fluid mass flow meter 11, fracturing fluid pipeline 7, connecting flange 6, and shut-off valve 5 to the high-pressure acid injection pipeline 44, thereby injecting the fracturing fluid into the fracturing permeation working hole 2.

[0053] Step 6: Stop the fracturing pump 14, close the shut-off valve 5, remove the connecting flange 6, disconnect the fracturing fluid injection, and allow the fracturing fluid to remain under pressure in the coal seam for 36 hours to complete the acid fracturing operation.

[0054] Step 7: After completing the acid fracturing operation, connect the sealing device 4 to the pulse circuit;

[0055] The pulse circuit includes a capacitor module 16, which is equipped with a capacitor protection module 17. The charging end of the capacitor module 16 is connected to one end of the charging protection module 19, and the other end of the charging protection module 19 is connected to a power supply 18.

[0056] The positive terminal of capacitor module 16 is connected to a positive circuit 8, which electrically connects the sealing device 4 to the positive terminal of capacitor module 16. A discharge switch 21 is installed on the positive circuit 8, and the controlled terminal of the discharge switch 21 is connected to a charge / discharge controller 20. The negative terminal of capacitor module 16 is connected to a negative circuit 9, which electrically connects the sealing device 4 to the negative terminal of capacitor module 16. An oscilloscope 22 is installed on the negative circuit 9.

[0057] When connecting the pulse circuit, two adjacent sealing devices 4 are used as a group. The two sealing devices 4 in the same group are connected to the positive circuit 8 and the negative circuit 9 respectively, and are connected to the same positive circuit 8 or negative circuit 9 as the other adjacent sealing device 4.

[0058] In particular, the circuit connection scheme is as follows Figure 4 As shown, this arrangement method allows for the achievement of global technical effects in the target area through two high-voltage pulse discharge operations without removing the integrated acid discharge sealing device.

[0059] Step 8: Perform the first discharge;

[0060] Before discharging, check that the capacitor protection module 17 and the charging protection module 19 are properly connected to the capacitor module 16. Then, turn on the power supply 18 and charge the capacitor module 16 through the power supply 18.

[0061] After the voltage inside the capacitor module 16 reaches the set value, it will be discharged. During discharge, the discharge switch 21 will be closed by operating the charge and discharge controller 20 to perform the first discharge.

[0062] The current starts from the capacitor module 16, flows through the positive circuit 8, through the conductive copper clamp 41, the high-voltage electrode section A 45, and the high-voltage electrode section B 46 to reach the wall of the fracturing and permeation working hole 2, and reaches the same fracturing and permeation working hole 2 by penetrating the coal seam 1. It then connects to the capacitor module 16 via the negative circuit 9 to form a discharge circuit.

[0063] And the area of ​​breakdown caused by the high-voltage pulse voltage in this step is as follows: Figure 5The upper part shown is the coal seam 1 area between the sealing devices 4 in the same group;

[0064] Step 9: Observe the current and voltage curves acquired by oscilloscope 22 to determine the effect of high voltage pulse discharge. If the discharge effect is not achieved, repeat step 8 until the discharge effect is met.

[0065] Step 10: Switch the circuit; switch the odd-numbered or even-numbered sealing device 4 to be connected to the positive circuit 8 or the negative circuit 9, and make both sealing devices 4 in the same group connected to the same positive circuit 8 or negative circuit 9. At the same time, the sealing device 4 with the changed circuit is connected to the positive circuit 8 and the negative circuit 9 respectively with another adjacent sealing device 4.

[0066] Step 11: Perform a second discharge by closing the discharge switch 21 through the charge / discharge controller 20; the area of ​​high-voltage pulse voltage breakdown in this step is as follows: Figure 5 The lower half of the diagram shows the coal seam 1 region between adjacent sealing devices 4 of different groups;

[0067] Observe the current and voltage curves acquired by the oscilloscope 22 to determine the effect of the high-voltage pulse discharge. If the discharge effect is not achieved, repeat this step until the discharge effect is met.

[0068] In particular, multiple discharges can be designed based on the actual occurrence conditions of coal seam 1 to achieve the best fracturing effect in the coal seam.

[0069] Step 12: Push the sealing device 4 toward the bottom of the fracturing and permeation working hole 2, and repeat steps 8 to 11 to achieve single and / or repeated high-voltage electric pulse discharge at different points in the same borehole, thereby enhancing the effect of high-voltage electric pulse discharge operation.

[0070] Step 13: Release the residual electrical energy in capacitor module 16 to complete the high-voltage pulse discharge operation.

[0071] Step 14: Extract the insulating oil from the expansion capsule 43, remove the sealing device 4, and complete the high-voltage electric pulse coordinated acid fracturing coal seam permeability enhancement operation.

Claims

1. A high-voltage electrical pulse-assisted acid fracturing coal seam permeability enhancement device, characterized in that: Includes a sealing device (4) for embedding in the fracturing permeation operation hole (2), the sealing device (4) includes a high-pressure acid injection pipe (44), the middle of the high-pressure acid injection pipe (44) is covered with an expansion capsule (43), both ends of the expansion capsule (43) are provided with fixed ends (42), and both ends of the high-pressure acid injection pipe (44) extend out of the fixed ends (42), the rear end of the high-pressure acid injection pipe (44) is connected to the acid fracturing fluid supply system through a connecting pipe; It also includes a pair of high-pressure electrodes respectively disposed on both sides of the high-pressure acid injection pipe (44). Each high-pressure electrode includes a high-pressure electrode section A (45) extending axially along the high-pressure acid injection pipe (44) and a high-pressure electrode section B (46) extending radially along the high-pressure acid injection pipe (44). The fixed end (42) at the front end has mounting holes on both sides radially for accommodating the high-pressure electrode section B (46). A spring (47) is fixedly disposed at the bottom of the mounting hole. The high-pressure electrode section B (46) and the spring (47) are connected. They are fixed together so that the outer end of the high-pressure electrode B section (46) is pressed against the inner wall of the fracturing and permeation operation hole (2). Both high-pressure electrode A sections (45) penetrate the expansion capsule (43). The front ends of the two high-pressure electrode A sections (45) extend into the mounting holes on both sides of the fixed end (42) at the front end, and abut against the high-pressure electrode B section (46) to achieve electrical connection. The rear end of the high-pressure electrode A section (45) passes through the fixed end (42) at the rear end of the high-pressure acid injection pipe (44) and is connected to the pulse circuit. The high voltage electrode B section (46) is provided with an anti-slip groove (46a) extending radially along the fixed end (42) on the side of the high voltage electrode A section (45) in the middle. The front end of the high voltage electrode A section (45) extends into the anti-slip groove (46a). The high-voltage electrode A section (45) and the high-voltage electrode B section (46) are both made of Cu-Cr-Zr alloy as the base material, and the surfaces of the high-voltage electrode A section (45) and the high-voltage electrode B section (46) are covered with CrN coating. The working method of the coal seam permeability enhancement device includes the following steps: Step 1: Select acetic acid as the acidizing fracturing fluid and store the acidizing fracturing fluid in the mixing tank (15). Step 2: Arrange multiple parallel fracturing and permeation operation holes (2) in the roadway of the target coal seam (1), with a spacing of 3~5m between the fracturing and permeation operation holes (2); Step 3: Place a sealing device (4) into each fracturing and permeation operation hole (2), and inject insulating oil into the expansion capsule (43) through the insulating oil supply system to make the expansion capsule (43) completely fit the hole wall and complete the sealing. Step 4: Connect each sealing device (4) to the acidizing fracturing fluid supply system; the acidizing fracturing fluid supply system includes a fracturing pump (14) whose inlet is connected to the mixing tank (15), and the outlet of the fracturing pump (14) is connected to the connecting flange (6) through the fracturing fluid pipeline (7). The fracturing fluid pipeline (7) is equipped with a filter (13), a hydraulic pressure gauge (12), a fluid mass flow meter (11) and a throttle valve (10). Step 5: Turn on the fracturing pump (14) to pump the fracturing fluid out of the mixing tank (15) and deliver it to the high-pressure acid injection pipeline (44), thereby injecting the fracturing fluid into the fracturing permeation working hole (2); Step 6: Stop the fracturing pump (14), close the shut-off valve (5), remove the connecting flange (6), disconnect the fracturing fluid injection, and allow the fracturing fluid to remain under pressure in the coal seam for a certain period of time to complete the acid fracturing operation; Step 7: After completing the acid fracturing operation, connect the sealing device (4) to the pulse circuit; The pulse circuit includes a capacitor module (16), the positive terminal of which is connected to a positive circuit (8), which is used to electrically connect the sealing device (4) and the positive terminal of the capacitor module (16). A discharge switch (21) is provided on the positive circuit (8), and the controlled end of the discharge switch (21) is connected to a charge / discharge controller (20). A negative circuit (9) is connected to the negative terminal of the capacitor module (16), which is used to electrically connect the sealing device (4) and the negative terminal of the capacitor module (16). An oscilloscope (22) is provided on the negative circuit (9). When connecting the pulse circuit, two adjacent sealing devices (4) are used as a group. The two sealing devices (4) in the same group are connected to the positive circuit (8) and the negative circuit (9) respectively, and are connected to the same positive circuit (8) or negative circuit (9) as the other adjacent sealing device (4). Step 8: Perform the first discharge; close the discharge switch (21) by operating the charge / discharge controller (20) to perform the first discharge; Step 9: Observe the current and voltage curves collected by the oscilloscope (22) to judge the high voltage pulse discharge effect. If the discharge effect is not achieved, repeat step 8 until the discharge effect is satisfied. Step 10: Switch the circuit; switch the odd-numbered or even-numbered sealing device (4) to be connected to the positive circuit (8) or the negative circuit (9), and make the two sealing devices (4) in the same group connected to the same positive circuit (8) or negative circuit (9), and connect the sealing device (4) to the positive circuit (8) and the negative circuit (9) respectively. Step 11: Perform the second discharge. Close the discharge switch (21) by operating the charge and discharge controller (20) to perform the second discharge. Observe the current and voltage curves collected by the oscilloscope (22) to judge the high voltage pulse discharge effect. If the discharge effect is not achieved, repeat this step until the discharge effect is satisfied. Step 12: Push the sealing device (4) toward the bottom of the fracturing and permeation working hole (2), and repeat steps 8 to 11 to achieve single and / or repeated high-voltage electric pulse discharge at different points in the same borehole; Step 13: Release the residual electrical energy in the capacitor module (16) to complete the high-voltage pulse discharge operation; Step 14: Extract the insulating oil from the expansion capsule (43), remove the sealing device (4), and complete the high-voltage electric pulse synergistic acid fracturing coal seam permeability enhancement operation.

2. The high-voltage electric pulse synergistic acid fracturing coal seam permeability enhancement device according to claim 1, characterized in that: The rear ends of the two high-voltage electrodes A segment (45) are fixed together by the same conductive copper clamp (41), which is used to connect the pulse circuit.

3. The high-voltage electric pulse synergistic acid fracturing coal seam permeability enhancement device according to claim 2, characterized in that: The expansion capsule (43) is equipped with an insulating oil supply system and expands by injecting insulating oil into the expansion capsule (43).

4. The high-voltage electric pulse synergistic acid fracturing coal seam permeability enhancement device according to claim 1, characterized in that: A shut-off valve (5) is installed on the connecting pipe located outside the fracturing permeation operation hole (2).

5. The high-voltage electric pulse synergistic acid fracturing coal seam permeability enhancement device according to claim 1, characterized in that: The capacitor module (16) is equipped with a capacitor protection module (17). The charging end of the capacitor module (16) is connected to one end of the charging protection module (19), and the other end of the charging protection module (19) is connected to the power supply (18).

6. The high-voltage electric pulse synergistic acid fracturing coal seam permeability enhancement device according to claim 5, characterized in that: Step 8 also includes the following steps: Before discharging, check that the capacitor protection module (17) and the charging protection module (19) are properly connected to the capacitor module (16), turn on the power supply (18), and charge the capacitor module (16) through the power supply (18). After the voltage inside the capacitor module (16) reaches the set value, then discharge.

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