Methane in-situ burning explosion fracturing system and method based on shock wave ignition

Abstract

The invention discloses a methane in-situ burning explosion fracturing system and method based on shock wave ignition. A shock wave tube assembly comprises a pressure-bearing tube body; the first clamping device and the second clamping device clamp the first diaphragm and the second diaphragm in the pressure-bearing pipe body. The gas filling assembly comprises a high-pressure gas tank, and a high-pressure gas supply pipeline and a double-membrane gas supply pipeline which are connected with the high-pressure gas tank are respectively communicated with the high-pressure cavity and the double-membrane cavity The exhaust assembly comprises a vacuum pump, a vacuumizing pipeline connected with the vacuum pump communicates with the high-pressure cavity and the double-film cavity through a first communicating pipeline and a second communicating pipeline correspondingly, and a double-film air leakage pipeline communicates with the second communicating pipeline. The methane burning explosion packing unit is a packer arranged on the pressure-bearing pipe body in a sleeving mode. The combustion improver conveying unit comprises an oxygen bottle, and an oxygen conveying pipeline connected with the oxygen bottle is communicated with the combustion explosion chamber; the combustible gas concentration detector is positioned on the oxygen conveying pipeline; the method comprises the following steps: assembling and lowering the shock tube assembly; the high-pressure and double-film cavity is vacuumized; filling gas; the pressure is quickly released; and the generated shock wave is used for igniting and expanding into burning explosion. The device is high in ignition energy and ideal in burning and explosion effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of unconventional natural gas extraction and fracturing production increase, and specifically relates to a methane in-situ explosion fracturing system and method based on shock wave ignition. Background Art

[0002] Against the backdrop of the "dual carbon" strategic goal, unconventional natural gas, as a crucial component of my country's resource system, has become a key driver of energy transition. In recent years, my country has achieved a series of major breakthroughs in the field of enhanced unconventional natural gas development technology. Hydraulic fracturing, currently one of the mainstream technologies for large-scale unconventional natural gas extraction, significantly improves reservoir macropermeability and exhibits broad applicability. However, traditional hydraulic fracturing solutions have numerous limitations. For example, they can easily lead to uniform fracture morphology, making it difficult to construct a three-dimensional, complex reservoir fracture network. This results in low extraction efficiency and unsatisfactory results.

[0003] Based on the above dilemma, some scholars have innovatively proposed the process technology concept of methane in-situ explosive fracturing. Methane, as the main component of unconventional natural gas, is a flammable and explosive gas that can produce a strong explosive shock effect after explosion. By injecting a variety of different types of combustion aids into the reservoir and fully mixing them with the in-situ desorbed methane, the ignition and explosion operation is carried out after the two reach a predetermined ratio and meet the explosion pressure conditions, an explosive fracturing phenomenon is generated inside the wellbore, and then a complex fracture network system is constructed to facilitate the efficient development of unconventional natural gas. However, the existing ignition method mostly uses cables to control the downhole ignition device. This method has the defects of relatively low ignition energy and poor explosion effect, and it is difficult to shape a complex fracture network structure over a large range after the explosion. For this reason, there is an urgent need to provide an explosive fracturing system and method that can significantly enhance the effect of methane in-situ explosive fracturing. Summary of the Invention

[0004] In response to the problems existing in the above-mentioned prior art, the present invention provides a methane in-situ explosion fracturing system and method based on shock wave ignition. The system has a reasonable structure and a simple operation process. It uses shock waves for ignition, has high ignition energy, and has a relatively ideal explosion effect. It can construct a highly complex fracture network structure, which is conducive to improving the extraction efficiency and extraction effect of unconventional natural gas. The method has a simple implementation process, an ideal explosion effect, reliable performance, and a high safety factor. It can enable the wellbore explosion gas to achieve rapid temperature and pressure increase and global ignition operations, can effectively enhance the methane in-situ explosion fracturing effect, can significantly improve the extraction efficiency and extraction effect of unconventional natural gas, and has broad application prospects and great practical value.

[0005] In order to achieve the above-mentioned object, the present invention provides a methane in-situ explosion fracturing system based on shock wave ignition, comprising a shock wave ignition unit, a methane explosion isolation unit and an oxidant delivery unit; The shock wave ignition unit includes a shock tube assembly, an air filling assembly and an exhaust assembly; the shock tube assembly includes a pressure tube body, an end cover, a clamp 1, a clamp 2, a diaphragm 1 and a diaphragm 2; the pressure tube body is arranged in the target fracturing section inside the wellbore; the end cover is encapsulated at the upper open end of the pressure tube body; the clamp 1 and the clamp 2 are connected in series on the lower section of the pressure tube body at intervals up and down; the diaphragm 1 and the diaphragm 2 are arranged inside the pressure tube body at intervals up and down. The edge parts of diaphragm 1 and diaphragm 2 are respectively clamped in the inside of clamper 1 and clamper 2; the inside of the pressure-bearing tube body forms a high-pressure chamber between the end cover and diaphragm 1, and a double-membrane chamber is formed between diaphragm 1 and diaphragm 2; the gas filling assembly includes a high-pressure gas tank, a high-pressure gas supply pipeline and a double-membrane gas supply pipeline; the high-pressure gas tank is set on the ground; the high-pressure gas supply pipeline and the double-membrane gas supply pipeline are respectively connected in series with gas filling valve 1 and gas filling valve 2, and the air inlet ends of the two air supply pipelines are connected to the high-pressure The air outlet valve 1 on the gas tank is connected, and its air outlet ends are extended to the interior of the wellbore, and the air outlet end of the high-pressure air supply pipeline is connected to the reserved air injection hole 1 on the end cover, and the air outlet end of the double-membrane air supply pipeline is connected to the double-membrane chamber through the reserved air injection hole 2 on the pressure-bearing pipe body; the exhaust assembly includes a vacuum pump, a vacuum pipeline and a double-membrane air release pipeline; the vacuum pump is set on the ground; the air inlet section of the vacuum pipeline extends to the interior of the wellbore, and is connected to the connecting pipeline 1 and the double-membrane air release pipeline at intervals above and below. Connecting pipeline 2, connecting pipeline 1 and connecting pipeline 2 are respectively connected in series with connecting valve 1 and connecting valve 2 in the middle section, connecting pipeline 1 is connected with the high-pressure chamber through the reserved exhaust hole 1 on the pressure-bearing pipe body, connecting pipeline 2 is connected with the double-membrane chamber through the reserved exhaust hole 2 on the pressure-bearing pipe body, and the outlet end of the vacuum pipeline is connected to the air inlet end of the vacuum pump; a pressure relief valve is connected in series on the double-membrane air release pipeline, the air inlet end of which is connected to the air inlet section of connecting pipeline 2, and the air outlet end of which is connected to the outside atmosphere; The methane explosion isolation unit is a packer, which is sleeved on the outside of the lower end of the pressure-bearing pipe body and is set in the wellbore, forming an explosion chamber between the packer, the wellbore and the second diaphragm; The combustion-supporting agent delivery unit includes an oxygen cylinder, an oxygen delivery pipeline and a combustible gas concentration detector; the oxygen cylinder is set on the ground; the air inlet end of the oxygen delivery pipeline is connected to the second air outlet valve of the oxygen cylinder, and its air outlet end extends into the wellbore and is connected to the combustion chamber after passing through the seal; the combustible gas concentration detector is installed at the air outlet end of the oxygen delivery pipeline.

[0006] Furthermore, to facilitate fully automated control, the system further includes a controller, which is connected to the combustible gas concentration detector, outlet valve 1, outlet valve 2, refill valve 1, refill valve 2, pressure relief valve, connecting valve 1, connecting valve 2, and vacuum pump. Furthermore, preferably, the system further includes a power module and a wireless communication module, the power module being connected to the controller for supplying electricity, and the wireless communication module being connected to the controller for establishing a communication link between the controller and an external terminal.

[0007] Furthermore, in order to facilitate the clamping operation of the first and second diaphragms and to ensure the overall sealing effect and pressure-bearing strength after clamping, the pressure-bearing pipe body includes an upper pipe body, a middle pipe body and a lower pipe body coaxially distributed from top to bottom; The clamper includes an upper diaphragm flange, a lower diaphragm flange, a sealing ring and a fastening bolt; the upper diaphragm flange is fixedly sleeved on the outside of the lower end of the upper tube body; the lower diaphragm flange is fixedly sleeved on the outside of the upper end of the middle tube body, and is distributed relative to the upper diaphragm flange up and down; the sealing ring is arranged between the upper diaphragm flange and the lower diaphragm flange; a plurality of fastening bolts are evenly arranged in a circumferential direction through a plurality of pairs of screw holes between the upper diaphragm flange and the lower diaphragm flange, and the two are locked and fixedly connected; wherein the outer edge portion of the diaphragm is arranged between the upper diaphragm flange and the lower diaphragm flange, and is fitly connected to the inner edge portion of the sealing ring; The clamper 2 includes an upper diaphragm flange 2, a lower diaphragm flange 2, a sealing ring 2 and a fastening bolt 2; the upper diaphragm flange 2 is fixedly sleeved on the outside of the lower end of the middle tube body; the lower diaphragm flange 2 is fixedly sleeved on the outside of the upper end of the lower tube body, and is distributed relative to the upper diaphragm flange 2 up and down; the sealing ring 2 is arranged between the upper diaphragm flange 2 and the lower diaphragm flange 2; multiple fastening bolts 2 are evenly circumferentially arranged in multiple pairs of screw holes between the upper diaphragm flange 2 and the lower diaphragm flange 2, and the two are locked and fixed together; wherein the outer edge portion of the diaphragm 2 is arranged between the upper diaphragm flange 2 and the lower diaphragm flange 2, and is fitly connected to the inner edge portion of the sealing ring 2.

[0008] As a preference, both the diaphragm 1 and the diaphragm 2 are made of industrial pure aluminum film.

[0009] Furthermore, in order to ensure a good sealing effect at the connection, the end cover and the pressure-bearing tube body are sealed and connected via a graphite sealing ring.

[0010] Furthermore, in order to facilitate the convenient control of the connection status of the high-pressure air supply pipeline and the double-membrane air supply pipeline with the high-pressure gas tank, the air outlet valve 1 is a three-way valve, and is connected to the air inlet end of the high-pressure air supply pipeline and the air inlet end of the double-membrane air supply pipeline through the three-way valve 1 respectively.

[0011] Furthermore, in order to ensure the effective formation of shock waves and at the same time, to ensure the explosion effect, the high-pressure gas tank is filled with pure hydrogen or pure helium or pure nitrogen or pure argon, or a mixed gas of hydrogen, helium, nitrogen and argon in a set proportion.

[0012] In the present invention, an end cap is encapsulated at the upper open end of the pressure-bearing tube body. At the same time, diaphragms 1 and 2 are respectively assembled inside the pressure-bearing tube body using clamps 1 and 2 connected in series on the pressure-bearing tube body. This allows the inner cavity of the pressure-bearing tube body to be separated from top to bottom into three sections using diaphragms 1 and 2 spaced apart from each other. The portion between the end cap and diaphragm 1 forms a high-pressure chamber, the portion between diaphragms 1 and 2 forms a double-diaphragm chamber, and the portion below diaphragm 2 can be directly connected to the wellbore. Connecting pipes 1 and 2, which are provided at the air inlet section of the vacuuming pipeline, are used to connect the high-pressure chamber and the double-diaphragm chamber, respectively. This allows the high-pressure chamber and the double-diaphragm chamber to be vacuumed using a vacuum pump. Connecting valves 1 and 2 are separately provided on connecting pipes 1 and 2, respectively. This allows the vacuum levels of the high-pressure chamber and the double-diaphragm chamber to meet operational requirements through independent control. By connecting a high-pressure gas supply line and a double-membrane gas supply line connected to a high-pressure gas tank to the high-pressure chamber and the double-membrane chamber, respectively, the high-pressure chamber and the double-membrane chamber can be filled with driving gas after the vacuum operation is completed. By separately providing filling valves one and two on the high-pressure gas supply line and the double-membrane gas supply line, respectively, it is possible to effectively ensure that the filling pressure of the high-pressure chamber and the double-membrane chamber meet the operational requirements through independent control. A packer is mounted on the lower end of the pressure-bearing pipe body and is seated inside the wellbore. In this way, the packer can effectively seal the annulus between the pressure-bearing pipe body and the wellbore, thereby forming an explosion chamber below diaphragm one. An oxygen delivery line connected to an oxygen cylinder passes through the packer and connects to the explosion chamber, facilitating the injection of oxygen into the explosion chamber. By providing a combustible gas concentration detector, the concentration data of the mixed explosive gas in the explosion chamber can be detected in real time, thereby facilitating a timely determination of whether the required explosion standard has been met. A double-membrane air release pipeline is connected to the connecting pipeline 2, and a pressure relief valve is connected in series to the double-membrane air release pipeline. On the one hand, the vacuum operation can be ensured to be carried out efficiently and smoothly when the pressure relief valve is closed. On the other hand, the double-membrane chamber can be quickly depressurized when the pressure relief valve is open. Since the double-membrane chamber is located between the high-pressure chamber and the explosion chamber, the pressure difference effect can be used to cause diaphragms one and two to rupture quickly in sequence, so that the driving gas in the high-pressure chamber can quickly break through diaphragms one and two under the action of the pressure difference and enter the explosion chamber, and can quickly generate shock waves in the explosion chamber. Therefore, the shock wave can cause the explosion gas to spontaneously ignite. This process can generate multiple ignition points at the same time, thereby effectively improving the ignition energy, and quickly expand to explosion on this basis, which can significantly enhance the explosion effect, and is conducive to shaping a crack network structure with high complexity and ideal connectivity in a larger range after the explosion.The system of the present invention can generate a huge pressure difference in an instant by means of vacuuming-pressurizing gas injection-rapid pressure relief, and thus can break the membrane instantly. At the moment of membrane breaking, a shock wave is formed in the low-pressure section. The temperature and pressure of the mixed gas in the low-pressure end and the connected explosion chamber rise sharply under the action of the shock wave, and ignition and explosion occur under the action of the reflected shock wave. The shock wave temperature and pressure increase effect and the overall ignition mode can significantly promote the methane explosion effect, and significantly improve the transformation effect of methane in-situ explosion fracturing on the reservoir. Selecting a suitable membrane breaking method is a key step in generating a stable shock wave in the shock tube. The innovative double-diaphragm structure membrane breaking in the present invention has the characteristics of convenient operation, rapid response, and good reusability.

[0013] The system has a reasonable structure and simple operation process. It can instantly generate high-temperature and high-pressure shock waves in the explosion space and ignite through shock waves. Its ignition energy is relatively high, which can significantly enhance the explosion effect. It can construct a highly complex fracture network structure, which is conducive to improving the extraction efficiency and extraction effect of unconventional natural gas.

[0014] The present invention also provides a methane in-situ explosion fracturing method based on shock wave ignition, which uses a methane in-situ explosion fracturing system based on shock wave ignition, including the following steps: Step 1: Collect geological parameters and exploration data of the target reservoir, and determine the inflation pressure of the high-pressure chamber and the double-membrane chamber according to the reservoir conditions, and then select the corresponding diaphragm 1 and diaphragm 2; Step 2: Clamp diaphragm 1 and diaphragm 2 into holder 1 and holder 2 respectively, and seal the end cap onto the upper open end of the pressure tube body to complete the assembly of the shock tube assembly; at the same time, sleeve the packer onto the exterior of the lower end of the pressure tube body; Step 3: Lower the shock tube assembly into the target fracturing section inside the wellbore and set the packer inside the wellbore; Step 4: Keep the outlet valve 1 and the pressure relief valve closed, start the vacuum pump, open the connecting valve 1 and the connecting valve 2, and use the vacuum pipeline to evacuate the high-pressure chamber and the double-membrane chamber. When the high-pressure chamber reaches the set vacuum degree 1, the connecting valve 1 is closed. When the double-membrane chamber reaches the set vacuum degree 2, the connecting valve 2 is closed. Step 5: Control the second outlet valve to open, and use the oxygen in the oxygen delivery pipeline to deliver it to the explosion chamber. At the same time, use the combustible gas concentration detector to collect the concentration signal of the explosion gas in the explosion chamber in real time, and send it to the controller. The controller obtains the concentration data of the explosion gas according to the concentration signal of the explosion gas. When the concentration data of the explosion gas reaches the set threshold, control the second outlet valve to close, and let it stand for a set time to allow the explosion gas to be fully mixed. Step 6: Control the outlet valve 1 to open, control the filling valve 1 and the filling valve 2 to open, and use the high-pressure gas supply pipeline and the double-membrane gas supply pipeline to fill the driving gas in the high-pressure gas tank into the high-pressure chamber and the double-membrane chamber respectively. When the high-pressure chamber reaches the set inflation pressure 1, control the filling valve 1 to close. When the double-membrane chamber reaches the set inflation pressure 2, control the filling valve 2 to close. After the filling valves 1 and 2 are both closed, control the outlet valve 1 to close. Step seven: Control the pressure relief valve to open, and use the double-membrane air relief pipeline to quickly relieve the pressure of the double-membrane chamber, so that the pressure difference between the high-pressure chamber and the double-membrane chamber increases instantly. The instantly increased pressure difference causes the gas in the high-pressure chamber to break through diaphragm one and diaphragm two at high speed and enter the explosion chamber. Under the impetus of the high-speed airflow, the explosion gas produces compression waves that quickly superimpose to form shock waves. The compression effect of the shock wave causes the temperature and pressure of the explosion gas in the explosion chamber to rise sharply. At the same time, when the explosion gas is compressed again by the reflected shock wave formed after being reflected by the end of the explosion chamber, its temperature and pressure further increase, and then global self-ignition occurs within microseconds and quickly expands into explosion.

[0015] As a preference, in step five, the time is set to 1 to 2 hours.

[0016] As a preference, in step six, the second inflation pressure is half of the first inflation pressure.

[0017] The present invention provides a methane in-situ explosion fracturing system and method based on shock wave ignition, which aims to provide a new technical path and solution for the further optimization and upgrading of unconventional natural gas development technology. Specifically, the inflation pressure of the high-pressure chamber and the double-membrane chamber is first determined according to the target reservoir conditions, and the corresponding diaphragms one and two are selected, which can effectively ensure that diaphragms one and two can be quickly broken under the pressure difference generated subsequently. The sealer mounted on the lower end of the pressure-bearing pipe body is then sealed in the wellbore, which can facilitate the formation of an explosion chamber below diaphragm two that is isolated from the upper space of the wellbore, the double-membrane chamber and the high-pressure chamber, thereby effectively ensuring the subsequent explosion effect. Then, a vacuum pump is used to evacuate the high-pressure chamber and the double-membrane chamber, which can not only remove the gas in the two chambers that has an adverse effect on the generation of shock waves or the subsequent explosion process, but also effectively ensure that a larger amount of driving gas can be filled in later. Then, driving gases of different pressures are respectively added to the high-pressure chamber and the double-membrane chamber, and then the pressure relief valve is opened to quickly relieve the pressure of the double-membrane chamber. Since the double-membrane chamber is located between the high-pressure chamber and the explosion chamber, the driving gas can quickly cause diaphragms one and two to rupture in sequence with the help of the pressure difference effect and enter the explosion chamber. The explosion gas produces compression waves under the push of the high-speed airflow and quickly forms shock waves. The compression effect of the shock wave causes the temperature and pressure of the mixed gas in the explosion chamber to rise sharply. When the gas is compressed again by the reflected shock wave formed after being reflected by the explosion chamber, its temperature and pressure rise further, and then spontaneous combustion occurs and multiple ignition points are generated, which then quickly expands into explosion, significantly enhancing the explosion effect. In this way, the shock wave, high-pressure gas and high-temperature effect generated by the explosion can be effectively utilized to synergistically impact the target reservoir, promote the development of cracks in the well wall, form a complex fracture network, and greatly improve the recovery rate.

[0018] The present invention utilizes the shock wave principle, rapidly forming a shock wave driven by a pressure differential. Leveraging the shock wave's ability to heat materials to ultra-high temperatures within an extremely short time span, measured in microseconds, the combustible mixture can rapidly explode under high temperature and pressure. Due to the extremely high initial temperature and pressure, the number of activated molecules in the mixture increases compared to explosions at room temperature and pressure, significantly increasing the probability of molecular collisions and releasing a higher total energy. Simultaneously, the energy density per unit time can also be significantly increased. Furthermore, the instantaneous pressure of a high-temperature, high-pressure explosion can reach hundreds of MPa, while the pressure of a room-temperature explosion is typically less than 2 MPa. Consequently, the explosion process of the present invention can release more energy, generate a stronger shock wave, produce greater destructive power, and have a wider impact range, significantly enhancing the effectiveness of in-situ methane explosion fracturing. Furthermore, the explosion energy can be precisely controlled by adjusting the driving gas injection pressure, and shock wave explosion operations can be repeated multiple times to more effectively enhance the effectiveness of in-situ methane explosion fracturing. Compared with conventional ignition methods, the shock wave ignition method in the present invention can quickly increase the initial temperature and pressure of the mixed gas in the explosion wellbore, and through the overall temperature increase ignition method, it can generate stronger explosion impact energy, effectively enhancing the explosion efficiency.

[0019] This method has a simple implementation process, ideal combustion and explosion effect, reliable performance, and a high safety factor. It can enable the wellbore combustion and explosion gas to achieve rapid temperature and pressure increase and global multi-point ignition operations, can effectively enhance the in-situ combustion and explosion fracturing effect of methane, and can significantly improve the extraction efficiency and extraction effect of unconventional natural gas. It has broad application prospects and great practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the assembly of the methane in-situ explosion fracturing system of the present invention; Figure 2 This is a schematic structural diagram of the methane in-situ explosion fracturing system of the present invention; Figure 3 This is a schematic diagram of the assembly of the first and second clamps and the pressure-bearing pipe body of the present invention; Figure 4 It is a principle block diagram of the control part in the present invention.

[0021] Figure: 1. Pressure pipe, 2. End cap, 3. Clamp 1, 4. Clamp 2, 5. Diaphragm 1, 6. Diaphragm 2, 7. High-pressure chamber, 8. Double-diaphragm chamber, 9. High-pressure gas tank, 10. High-pressure gas supply line, 11. Double-diaphragm gas supply line, 12. Vacuum pump, 13. Vacuum pump line, 14. Double-diaphragm gas release line, 15. Packer, 16. Explosion chamber, 17. Oxygen cylinder, 18. Oxygen delivery line , 19. Combustible gas concentration detector, 20. Upper pipe body, 21. Middle pipe body, 22. Lower pipe body, 23. Upper diaphragm flange one, 24. Lower diaphragm flange one, 25. Fastening bolt one, 26. Sealing ring one, 27. Lower diaphragm flange two, 28. Lower diaphragm flange two, 29. Fastening bolt two, 30. Sealing ring two, 31. Connecting pipeline one, 32. Connecting pipeline two, 33. Wellbore. DETAILED DESCRIPTION

[0022] The present invention will be further described below with reference to the accompanying drawings.

[0023] like Figures 1 to 4 As shown, the present invention provides a methane in-situ explosion fracturing system based on shock wave ignition, comprising a shock wave ignition unit, a methane explosion isolation unit and an oxidant delivery unit; The shock wave ignition unit includes a shock tube assembly, an air filling assembly and an exhaust assembly; the shock tube assembly includes a pressure tube body 1, an end cover 2, a clamp 1 3, a clamp 2 4, a diaphragm 1 5 and a diaphragm 2 6; the pressure tube body 1 is arranged in the target fracturing section inside the wellbore 33; the end cover 2 is encapsulated in the upper open end of the pressure tube body 1; the clamp 1 3 and the clamp 2 4 are connected in series on the lower section of the pressure tube body 1 at intervals up and down; the diaphragm 1 5 and the diaphragm 2 6 are arranged in the interior of the pressure tube body 1 at intervals up and down, and are respectively arranged at the positions where the clamp 1 3 and the clamp 2 4 are located. The edge portions of the diaphragm 1 5 and the diaphragm 2 6 are respectively clamped in the interior of the clamp 1 3 and the clamp 2 4; the interior of the pressure-bearing tube body 1 forms a high-pressure chamber 7 between the end cap 2 and the diaphragm 1 5, and a double-membrane chamber 8 between the diaphragm 1 5 and the diaphragm 2 6; the gas filling assembly includes a high-pressure gas tank 9, a high-pressure gas supply pipeline 10 and a double-membrane gas supply pipeline 11; the high-pressure gas tank 9 is set on the ground, and the interior thereof is filled with driving gas; the high-pressure gas supply pipeline 10 and the double-membrane gas supply pipeline 11 are respectively connected in series with a gas filling valve 1 and a gas filling valve 2, and the two gas supply pipelines (the high-pressure gas supply pipeline 10 and the double-membrane gas supply pipeline 11) are connected in series with each other. The air inlet end of the air supply pipe 11 is connected to the air outlet valve 1 on the high-pressure gas tank 9, and the air outlet end thereof extends to the interior of the wellbore 33, and the air outlet end of the high-pressure air supply pipe 10 is connected to the reserved air injection hole 1 on the end cover 2, and then communicated with the high-pressure chamber 7 through the reserved air injection hole 1, and the air outlet end of the double-membrane air supply pipe 11 is communicated with the double-membrane chamber 8 through the reserved air injection hole 2 on the pressure-bearing pipe body 1; the exhaust component includes a vacuum pump 12, a vacuum pumping pipe 13 and a double-membrane air release pipe 14; the vacuum pump 12 is arranged on the ground; the air inlet section of the vacuum pumping pipe 13 extends to the interior of the wellbore 33, and A connecting pipe 1 31 and a connecting pipe 2 32 are connected at intervals above and below, and a connecting valve 1 and a connecting valve 2 are connected in series to the middle sections of the connecting pipe 1 31 and the connecting pipe 2 32 respectively. The connecting pipe 1 31 is connected to the high-pressure chamber 7 through the reserved exhaust hole 1 on the pressure-bearing pipe body 1, and the connecting pipe 2 32 is connected to the double-membrane chamber 8 through the reserved exhaust hole 2 on the pressure-bearing pipe body 1. The outlet end of the vacuum pipe 13 is connected to the air inlet end of the vacuum pump 12; the double-membrane air release pipe 14 is connected in series with a pressure relief valve, the air inlet end of which is connected to the air inlet section of the connecting pipe 2 32, and the air outlet end of which is connected to the outside atmosphere; The methane explosion isolation unit is a packer 15, which is sleeved on the outside of the lower end of the pressure pipe 1 and is set in the wellbore 33, forming an explosion chamber 16 between the packer 15, the wellbore 33 and the diaphragm 2 6; The combustion-supporting agent delivery unit includes an oxygen cylinder 17, an oxygen delivery pipeline 18 and a combustible gas concentration detector 14; the oxygen cylinder 17 is set on the ground, and is filled with a combustion-supporting agent, preferably oxygen; the air inlet end of the oxygen delivery pipeline 18 is connected to the second air outlet valve of the oxygen cylinder 17, and its air outlet end extends into the wellbore 33, and is connected to the explosion chamber 16 after passing through the seal 15; the combustible gas concentration detector 14 is installed at the air outlet end of the oxygen delivery pipeline 18, and is used to collect the concentration signal of the mixed explosion gas in the explosion chamber 16 in real time, and send it to the controller. The controller obtains the concentration data of the mixed explosion gas according to the concentration signal of the mixed explosion gas, and determines whether the optimal explosion concentration equivalence ratio (set threshold) is reached according to the concentration data of the mixed explosion gas.

[0024] In order to facilitate the realization of a fully automated control process, a controller is also included, which is respectively connected to the combustible gas concentration detector 14, the first and second gas outlet valves, the first and second gas filling valves, the pressure relief valve, the first and second connecting valves, and the vacuum pump 12. As a preferred embodiment, the controller adopts a PLC controller.

[0025] In order to facilitate the clamping operation of the first and second diaphragms and to ensure the overall sealing effect and pressure-bearing strength after clamping, the pressure-bearing pipe body 1 includes an upper pipe body 20, a middle pipe body 21 and a lower pipe body 22 coaxially distributed from top to bottom; The clamper 3 includes an upper diaphragm flange 23, a lower diaphragm flange 24, a sealing ring 26 and a fastening bolt 25; the upper diaphragm flange 23 is fixedly sleeved on the outside of the lower end of the upper tube body 20; the lower diaphragm flange 24 is fixedly sleeved on the outside of the upper end of the middle tube body 21, and is distributed relative to the upper diaphragm flange 23 up and down; the sealing ring 26 is arranged between the upper diaphragm flange 23 and the lower diaphragm flange 24; a plurality of fastening bolts 25 are evenly arranged in the circumferential direction through a plurality of pairs of screw holes between the upper diaphragm flange 23 and the lower diaphragm flange 24, and the two are locked and fixedly connected; wherein the outer edge portion of the diaphragm 5 is arranged between the upper diaphragm flange 23 and the lower diaphragm flange 24, and is fitly connected to the inner edge portion of the sealing ring 26, so that the sealing performance of the diaphragm 5 can be effectively ensured to effectively prevent air leakage; The clamper 24 includes an upper diaphragm flange 27, a lower diaphragm flange 28, a sealing ring 230 and a fastening bolt 29; the upper diaphragm flange 27 is fixedly sleeved on the outside of the lower end of the middle tube body 21; the lower diaphragm flange 28 is fixedly sleeved on the outside of the upper end of the lower tube body 22, and is distributed relative to the upper diaphragm flange 27 up and down; the sealing ring 230 is arranged between the upper diaphragm flange 27 and the lower diaphragm flange 28; a plurality of fastening bolts 29 are evenly arranged circumferentially through a plurality of pairs of screw holes between the upper diaphragm flange 27 and the lower diaphragm flange 28, and the two are locked and fixed together; wherein the outer edge portion of the diaphragm 26 is arranged between the upper diaphragm flange 27 and the lower diaphragm flange 28, and is fitly connected to the inner edge portion of the sealing ring 230, so that the sealing performance of the diaphragm 26 can be effectively ensured to effectively prevent air leakage; The double membrane chamber 8 serves as a filtering section connecting the high-pressure chamber 7 and the explosion chamber 16. It is the key to generating shock waves. The selection of diaphragm 1 5 and diaphragm 2 6 is crucial. The diaphragm 1 5 and diaphragm 2 6 are made of industrial pure aluminum membrane of the same model that meets the specifications according to the material, category, membrane breaking pressure difference, etc. It is further preferred that diaphragm 1 5 and diaphragm 2 6 are pre-treated with high temperature annealing to reduce the hardness of the aluminum membrane, improve the plasticity of the aluminum diaphragm, increase the membrane breaking pressure difference, and then engrave cross grooves of different widths and thicknesses to further reduce the hardness of the aluminum diaphragm, facilitate increasing the membrane breaking pressure difference, and at the same time, effectively avoid the occurrence of fragment splashing during the crushing process.

[0026] In order to ensure a good sealing effect at the connection, the end cover 2 and the pressure-bearing pipe body 1 are sealed by a graphite sealing ring.

[0027] In order to facilitate the convenient control of the connection status between the high-pressure gas supply pipeline and the double-membrane gas supply pipeline and the high-pressure gas tank, the outlet valve 1 is a three-way valve, and is connected to the air inlet end of the high-pressure gas supply pipeline 10 and the air inlet end of the double-membrane gas supply pipeline 11 through the three-way valve 1.

[0028] In order to ensure the effective formation of shock waves and at the same time, to ensure the explosion effect, the high-pressure gas tank 9 is filled with pure hydrogen, pure helium, pure nitrogen, or pure argon, or a mixed gas of hydrogen, helium, nitrogen and argon in a set proportion.

[0029] In the present invention, an end cap is encapsulated at the upper open end of the pressure-bearing tube body. At the same time, diaphragms 1 and 2 are respectively assembled inside the pressure-bearing tube body using clamps 1 and 2 connected in series on the pressure-bearing tube body. This allows the inner cavity of the pressure-bearing tube body to be separated from top to bottom into three sections using diaphragms 1 and 2 spaced apart from each other. The portion between the end cap and diaphragm 1 forms a high-pressure chamber, the portion between diaphragms 1 and 2 forms a double-diaphragm chamber, and the portion below diaphragm 2 can be directly connected to the wellbore. Connecting pipes 1 and 2, which are provided at the air inlet section of the vacuuming pipeline, are used to connect the high-pressure chamber and the double-diaphragm chamber, respectively. This allows the high-pressure chamber and the double-diaphragm chamber to be vacuumed using a vacuum pump. Connecting valves 1 and 2 are separately provided on connecting pipes 1 and 2, respectively. This allows the vacuum levels of the high-pressure chamber and the double-diaphragm chamber to meet operational requirements through independent control. By connecting a high-pressure gas supply line and a double-membrane gas supply line connected to a high-pressure gas tank to the high-pressure chamber and the double-membrane chamber, respectively, the high-pressure chamber and the double-membrane chamber can be filled with driving gas after the vacuum operation is completed. By separately providing filling valves one and two on the high-pressure gas supply line and the double-membrane gas supply line, respectively, it is possible to effectively ensure that the filling pressure of the high-pressure chamber and the double-membrane chamber meet the operational requirements through independent control. A packer is mounted on the lower end of the pressure-bearing pipe body and is seated inside the wellbore. In this way, the packer can effectively seal the annulus between the pressure-bearing pipe body and the wellbore, thereby forming an explosion chamber below diaphragm one. An oxygen delivery line connected to an oxygen cylinder passes through the packer and connects to the explosion chamber, facilitating the injection of oxygen into the explosion chamber. By providing a combustible gas concentration detector, the concentration data of the mixed explosive gas in the explosion chamber can be detected in real time, thereby facilitating a timely determination of whether the required explosion standard has been met. A double-membrane air release pipeline is connected to the connecting pipeline 2, and a pressure relief valve is connected in series to the double-membrane air release pipeline. On the one hand, the vacuum operation can be ensured to be carried out efficiently and smoothly when the pressure relief valve is closed. On the other hand, the double-membrane chamber can be quickly depressurized when the pressure relief valve is open. Since the double-membrane chamber is located between the high-pressure chamber and the explosion chamber, the pressure difference effect can be used to cause diaphragms one and two to rupture quickly in sequence, so that the driving gas in the high-pressure chamber can quickly break through diaphragms one and two under the action of the pressure difference and enter the explosion chamber, and can quickly generate shock waves in the explosion chamber. Therefore, the shock wave can cause the explosion gas to spontaneously ignite. This process can generate multiple ignition points at the same time, thereby effectively improving the ignition energy, and quickly expand to explosion on this basis, which can significantly enhance the explosion effect, and is conducive to shaping a crack network structure with high complexity and ideal connectivity in a larger range after the explosion.The system of the present invention can generate a huge pressure difference in an instant by means of vacuuming-pressurizing gas injection-rapid pressure relief, and thus can break the membrane instantly. At the moment of membrane breaking, a shock wave is formed in the low-pressure section. The temperature and pressure of the mixed gas in the low-pressure end and the connected explosion chamber rise sharply under the action of the shock wave, and ignition and explosion occur under the action of the reflected shock wave. The shock wave temperature and pressure increase effect and the overall ignition mode can significantly promote the methane explosion effect, and significantly improve the transformation effect of methane in-situ explosion fracturing on the reservoir. Selecting a suitable membrane breaking method is a key step in generating a stable shock wave in the shock tube. The innovative double-diaphragm structure membrane breaking in the present invention has the characteristics of convenient operation, rapid response, and good reusability.

[0030] The system has a reasonable structure and simple operation process. It can instantly generate high-temperature and high-pressure shock waves in the explosion space and ignite through shock waves. Its ignition energy is relatively high, which can significantly enhance the explosion effect. It can construct a highly complex fracture network structure, which is conducive to improving the extraction efficiency and extraction effect of unconventional natural gas.

[0031] The present invention also provides a methane in-situ explosion fracturing method based on shock wave ignition, which uses a methane in-situ explosion fracturing system based on shock wave ignition, including the following steps: Step 1: Collect geological parameters and exploration data of the target reservoir, and determine the inflation pressure of the high-pressure chamber 7 and the double-membrane chamber 8 based on the reservoir conditions and the preset explosion pressure and temperature, and then select the corresponding diaphragm 1 5 and diaphragm 2 6; Step 2: Clamp diaphragm 1 5 and diaphragm 2 6 into holder 1 3 and holder 2 4 respectively, and seal the end cap 2 onto the upper open end of the pressure tube 1 to complete the assembly of the shock tube assembly; at the same time, fit the packer 15 onto the outside of the lower end of the pressure tube 1; Step 3: Lower the shock tube assembly into the target fracturing section inside the wellbore 33 and set the packer 15 inside the wellbore 33; Step 4: Keep the outlet valve 1 and the pressure relief valve closed, control the vacuum pump 12 to start working, control the connecting valve 1 and the connecting valve 2 to open, and use the vacuum pumping pipeline 13 to vacuum the high-pressure chamber 7 and the double-membrane chamber 8. When the high-pressure chamber 7 reaches the set vacuum degree 1, the connecting valve 1 is controlled to be closed, and when the double-membrane chamber 8 reaches the set vacuum degree 2, the connecting valve 2 is controlled to be closed; preferably, pressure sensors 1 and 2 are respectively connected to the connecting pipelines 1 and 2, and the pressure sensors 1 and 2 are respectively used to collect pressure signals 1 and 2 of the high-pressure chamber 7 and the double-membrane chamber 8 in real time during the vacuum pumping process, and send them to the controller, and the controller obtains the vacuum degree 1 of the high-pressure chamber 7 and the vacuum degree 2 of the double-membrane chamber 8 according to the pressure signals 1 and 2; Step 5: Control the second outlet valve to open, and use the oxygen delivery pipeline 18 to deliver the oxygen in the oxygen cylinder 17 to the explosion chamber 16. At the same time, use the combustible gas concentration detector 14 to collect the concentration signal of the explosion gas (a mixture of methane and oxygen) in the explosion chamber 16 in real time and send it to the controller. The controller obtains the concentration data of the explosion gas according to the concentration signal of the explosion gas. When the concentration data of the explosion gas reaches the set threshold, the second outlet valve is controlled to close, and the gas is left to stand for a set time to allow the explosion gas to be fully mixed. Step 6: Control the outlet valve 1 to open, control the filling valve 1 and the filling valve 2 to open, and use the high-pressure gas supply pipeline 10 and the double-membrane gas supply pipeline 11 to fill the driving gas in the high-pressure gas tank 9 into the high-pressure chamber 7 and the double-membrane chamber 8 respectively. When the high-pressure chamber 7 reaches the set inflation pressure 1, control the filling valve 1 to close. When the double-membrane chamber 8 reaches the set inflation pressure 2, control the filling valve 2 to close. After the filling valves 1 and 2 are both closed, control the outlet valve 1 to close; preferably, the pressure sensors 1 and 2 on the connecting pipelines 1 and 2 can be used to collect the pressure signal 3 in the high-pressure chamber 7 and the pressure signal 4 in the double-membrane chamber 8 in real time during the gas filling process, and the controller obtains the inflation pressure 1 and the inflation pressure 2 based on the pressure signals 3 and 4 respectively; Step seven: Control the pressure relief valve to open, and use the double-membrane air relief pipe 14 to quickly relieve the pressure of the double-membrane chamber 8, so that the pressure difference between the high-pressure chamber 7 and the double-membrane chamber 8 increases instantly. The instantly increased pressure difference causes the gas in the high-pressure chamber 7 to break through the diaphragm 1 5 and the diaphragm 2 6 at high speed and enter the explosion chamber 16 (low-pressure section). Under the impetus of the high-speed airflow, the explosion gas produces compression waves that quickly superimpose to form a shock wave. The compression effect of the shock wave causes the temperature and pressure of the explosion gas in the explosion chamber 16 to rise sharply. At the same time, when the explosion gas is compressed again by the reflected shock wave formed after being reflected by the end of the explosion chamber 16, its temperature and pressure further increase, and then global self-ignition occurs within microseconds and quickly expands into an explosion.

[0032] As a preference, in step five, the time is set to 1 to 2 hours.

[0033] As a preference, in step six, the second inflation pressure is half of the first inflation pressure.

[0034] The present invention provides a methane in-situ explosion fracturing system and method based on shock wave ignition, which aims to provide a new technical path and solution for the further optimization and upgrading of unconventional natural gas development technology. Specifically, the inflation pressure of the high-pressure chamber and the double-membrane chamber is first determined according to the target reservoir conditions, and the corresponding diaphragms one and two are selected, which can effectively ensure that diaphragms one and two can be quickly broken under the pressure difference generated subsequently. The sealer mounted on the lower end of the pressure-bearing pipe body is then sealed in the wellbore, which can facilitate the formation of an explosion chamber below diaphragm two that is isolated from the upper space of the wellbore, the double-membrane chamber and the high-pressure chamber, thereby effectively ensuring the subsequent explosion effect. Then, a vacuum pump is used to evacuate the high-pressure chamber and the double-membrane chamber, which can not only remove the gas in the two chambers that has an adverse effect on the generation of shock waves or the subsequent explosion process, but also effectively ensure that a larger amount of driving gas can be filled in later. Then, driving gases of different pressures are respectively added to the high-pressure chamber and the double-membrane chamber, and then the pressure relief valve is opened to quickly relieve the pressure of the double-membrane chamber. Since the double-membrane chamber is located between the high-pressure chamber and the explosion chamber, the driving gas can quickly cause diaphragms one and two to rupture in sequence with the help of the pressure difference effect and enter the explosion chamber. The explosion gas produces compression waves under the push of the high-speed airflow and quickly forms shock waves. The compression effect of the shock wave causes the temperature and pressure of the mixed gas in the explosion chamber to rise sharply. When the gas is compressed again by the reflected shock wave formed after being reflected by the explosion chamber, its temperature and pressure rise further, and then spontaneous combustion occurs and multiple ignition points are generated, which then quickly expands into explosion, significantly enhancing the explosion effect. In this way, the shock wave, high-pressure gas and high-temperature effect generated by the explosion can be effectively utilized to synergistically impact the target reservoir, promote the development of cracks in the well wall, form a complex fracture network, and greatly improve the recovery rate.

[0035] The present invention utilizes the shock wave principle, rapidly forming a shock wave driven by a pressure differential. Leveraging the shock wave's ability to heat materials to ultra-high temperatures within an extremely short time span, measured in microseconds, the combustible mixture can rapidly explode under high temperature and pressure. Due to the extremely high initial temperature and pressure, the number of activated molecules in the mixture increases compared to explosions at room temperature and pressure, significantly increasing the probability of molecular collisions and releasing a higher total energy. Simultaneously, the energy density per unit time can also be significantly increased. Furthermore, the instantaneous pressure of a high-temperature, high-pressure explosion can reach hundreds of MPa, while the pressure of a room-temperature explosion is typically less than 2 MPa. Consequently, the explosion process of the present invention can release more energy, generate a stronger shock wave, produce greater destructive power, and have a wider impact range, significantly enhancing the effectiveness of in-situ methane explosion fracturing. Furthermore, the explosion energy can be precisely controlled by adjusting the driving gas injection pressure, and shock wave explosion operations can be repeated multiple times to more effectively enhance the effectiveness of in-situ methane explosion fracturing. Compared to conventional ignition methods, the shock wave ignition method of the present invention can rapidly increase the initial temperature and pressure of the mixed gas in the explosion wellbore, and through the overall temperature increase ignition method, it generates stronger explosion impact energy, effectively enhancing the explosion efficiency. This method has a simple implementation process, ideal explosion effect, reliable performance, and a high safety factor. It can achieve rapid temperature and pressure increase and overall global multi-point ignition operations for the explosion gas in the wellbore, effectively enhancing the in-situ explosion fracturing effect of methane, significantly improving the extraction efficiency and extraction effect of unconventional natural gas, and has broad application prospects and great practical value.

Claims

1. A methane in-situ explosion fracturing system based on shock wave ignition, comprising a shock wave ignition unit, characterized in that: It also includes a methane explosion isolation unit and an oxidant delivery unit; The shock wave ignition unit includes a shock tube assembly, an air filling assembly and an exhaust assembly; the shock tube assembly includes a pressure tube body (1), an end cover (2), a clamp 1 (3), a clamp 2 (4), a diaphragm 1 (5) and a diaphragm 2 (6); the pressure tube body (1) is arranged in a target fracturing section inside a wellbore (33); the end cover (2) is encapsulated at the upper open end of the pressure tube body (1); the clamp 1 (3) and the clamp 2 (4) are connected in series on the lower section of the pressure tube body (1) at intervals from top to bottom; the diaphragm 1 (5) and the diaphragm 2 (6) are arranged inside the pressure tube body (1) at intervals from top to bottom, and the diaphragm The edge portions of diaphragm one (5) and diaphragm two (6) are respectively clamped inside the clamp one (3) and the clamp two (4); the inside of the pressure-bearing tube body (1) forms a high-pressure chamber (7) between the end cover (2) and diaphragm one (5), and forms a double-membrane chamber (8) between diaphragm one (5) and diaphragm two (6); the gas filling assembly includes a high-pressure gas tank (9), a high-pressure gas supply pipeline (10) and a double-membrane gas supply pipeline (11); the high-pressure gas tank (9) is set on the ground; the high-pressure gas supply pipeline (10) and the double-membrane gas supply pipeline (11) are respectively connected in series with gas filling valve one and gas filling valve two, and the gas inlet ends of the two gas supply pipelines are connected to the The outlet valve on the high-pressure gas tank (9) is connected, and its outlet ends extend to the interior of the wellbore (33), and the outlet end of the high-pressure gas supply pipeline (10) is connected to the reserved gas injection hole 1 on the end cover (2), and the outlet end of the double-membrane gas supply pipeline (11) is connected to the double-membrane chamber (8) through the reserved gas injection hole 2 on the pressure-bearing pipe body (1); the exhaust component includes a vacuum pump (12), a vacuum pumping pipeline (13) and a double-membrane air release pipeline (14); the vacuum pump (12) is set on the ground; the air inlet section of the vacuum pumping pipeline (13) extends to the interior of the wellbore (33), and is connected to the connecting pipeline 1 (34) at intervals above and below. 1) and the connecting pipe 2 (32), the middle sections of the connecting pipe 1 (31) and the connecting pipe 2 (32) are respectively connected in series with a connecting valve 1 and a connecting valve 2, the connecting pipe 1 (31) is connected to the high-pressure chamber (7) through the reserved exhaust hole 1 on the pressure-bearing pipe body (1), and the connecting pipe 2 (32) is connected to the double-membrane chamber (8) through the reserved exhaust hole 2 on the pressure-bearing pipe body (1), and the outlet end of the vacuum pipe (13) is connected to the inlet end of the vacuum pump (12); the double-membrane air release pipe (14) is connected in series with a pressure relief valve, the inlet end of which is connected to the inlet section of the connecting pipe 2 (32), and the outlet end thereof is connected to the outside atmosphere; The methane explosion isolation unit is a packer (15), which is sleeved on the outside of the lower end of the pressure-bearing pipe (1) and is sealed in the wellbore (33), forming an explosion chamber (16) between the packer (15), the wellbore (33) and the second diaphragm (6); The combustion-supporting agent delivery unit comprises an oxygen cylinder (17), an oxygen delivery pipeline (18) and a combustible gas concentration detector (14); the oxygen cylinder (17) is arranged on the ground; the air inlet end of the oxygen delivery pipeline (18) is connected to the second air outlet valve of the oxygen cylinder (17), and the air outlet end thereof extends into the wellbore (33) and is connected to the explosion chamber (16) after passing through the packer (15); the combustible gas concentration detector (14) is installed at the air outlet end of the oxygen delivery pipeline (18).

2. The methane in-situ explosion fracturing system based on shock wave ignition according to claim 1, characterized in that: It also includes a controller, which is respectively connected to the combustible gas concentration detector (14), the first gas outlet valve, the second gas outlet valve, the first gas filling valve, the second gas filling valve, the pressure relief valve, the first connecting valve, the second connecting valve and the vacuum pump (12).

3. A methane in-situ explosion fracturing system based on shock wave ignition according to claim 1 or 2, characterized in that: The pressure-bearing pipe body (1) comprises an upper pipe body (20), a middle pipe body (21) and a lower pipe body (22) which are coaxially distributed in sequence from top to bottom; The clamper (3) includes an upper diaphragm flange (23), a lower diaphragm flange (24), a sealing ring (26) and a fastening bolt (25); the upper diaphragm flange (23) is fixedly sleeved on the outside of the lower end of the upper tube body (20); the lower diaphragm flange (24) is fixedly sleeved on the outside of the upper end of the middle tube body (21), and is distributed relative to the upper diaphragm flange (23) in the upper and lower directions; the sealing ring (26) is arranged between the upper diaphragm flange (23) and the lower diaphragm flange (24); a plurality of fastening bolts (25) are uniformly arranged in the circumferential direction through a plurality of pairs of screw holes between the upper diaphragm flange (23) and the lower diaphragm flange (24), and the two are locked and fixedly connected; wherein the outer edge portion of the diaphragm (5) is arranged between the upper diaphragm flange (23) and the lower diaphragm flange (24), and is fit-connected with the inner edge portion of the sealing ring (26); The clamper 2 (4) includes an upper diaphragm flange 2 (27), a lower diaphragm flange 2 (28), a sealing ring 2 (30) and a fastening bolt 2 (29); the upper diaphragm flange 2 (27) is fixedly mounted on the outside of the lower end of the middle tube body (21); the lower diaphragm flange 2 (28) is fixedly mounted on the outside of the upper end of the lower tube body (22), and is distributed relative to the upper diaphragm flange 2 (27) up and down; the sealing ring 2 (30) is arranged between the upper diaphragm flange 2 (27) and the lower diaphragm flange 2 (28); a plurality of fastening bolts 2 (29) are uniformly arranged in the circumferential direction through a plurality of pairs of screw holes between the upper diaphragm flange 2 (27) and the lower diaphragm flange 2 (28), and the two are locked and fixed together; wherein the outer edge portion of the diaphragm 2 (6) is arranged between the upper diaphragm flange 2 (27) and the lower diaphragm flange 2 (28), and is fit-connected to the inner edge portion of the sealing ring 2 (30).

4. The methane in-situ explosion fracturing system based on shock wave ignition according to claim 3, characterized in that: The diaphragm 1 (5) and the diaphragm 2 (6) are both made of industrial pure aluminum film.

5. The methane in-situ explosion fracturing system based on shock wave ignition according to claim 4, characterized in that: The end cover (2) and the pressure-bearing tube body (1) are sealed and connected via a graphite sealing ring.

6. The methane in-situ explosion fracturing system based on shock wave ignition according to claim 5, characterized in that: The outlet valve 1 is a three-way valve, and is connected to the air inlet end of the high-pressure air supply pipeline (10) and the air inlet end of the double-membrane air supply pipeline (11) respectively through the three-way valve 1.

7. The methane in-situ explosion fracturing system based on shock wave ignition according to claim 6, characterized in that: The high-pressure gas tank (9) is filled with pure hydrogen, pure helium, pure nitrogen, or pure argon, or a mixed gas of hydrogen, helium, nitrogen, and argon in a set ratio.

8. A methane in-situ explosion fracturing method based on shock wave ignition, using a methane in-situ explosion fracturing system based on shock wave ignition according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: Collect geological parameters and exploration data of the target reservoir, and determine the inflation pressure of the high-pressure chamber (7) and the double-membrane chamber (8) according to the reservoir conditions, and then select the corresponding diaphragm 1 (5) and diaphragm 2 (6); Step 2: Clamp the diaphragm 1 (5) and the diaphragm 2 (6) in the clamp 1 (3) and the clamp 2 (4) respectively, and seal the end cover (2) on the upper open end of the pressure tube body (1) to complete the assembly of the shock tube assembly; at the same time, sleeve the packer (15) on the outside of the lower end of the pressure tube body (1); Step 3: lowering the shock tube assembly into the target fracturing section inside the wellbore (33), and setting the packer (15) inside the wellbore (33); Step 4: Keep the outlet valve 1 and the pressure relief valve closed, control the vacuum pump (12) to start working, control the connecting valve 1 and the connecting valve 2 to open, and use the vacuum pumping pipeline (13) to evacuate the high-pressure chamber (7) and the double-membrane chamber (8). When the high-pressure chamber (7) reaches the set vacuum degree 1, the connecting valve 1 is controlled to be closed, and when the double-membrane chamber (8) reaches the set vacuum degree 2, the connecting valve 2 is controlled to be closed; Step 5: Control the second outlet valve to open, and use the oxygen delivery pipeline (18) to deliver the oxygen in the oxygen cylinder (17) to the explosion chamber (16). At the same time, use the combustible gas concentration detector (14) to collect the concentration signal of the explosion gas in the explosion chamber (16) in real time, and send it to the controller. The controller obtains the concentration data of the explosion gas according to the concentration signal of the explosion gas. When the concentration data of the explosion gas reaches a set threshold, control the second outlet valve to close, and let it stand for a set time to allow the explosion gas to be fully mixed. Step 6: Control the outlet valve 1 to open, control the filling valve 1 and the filling valve 2 to open, and use the high-pressure gas supply pipeline (10) and the double-membrane gas supply pipeline (11) to fill the driving gas in the high-pressure gas tank (9) into the high-pressure chamber (7) and the double-membrane chamber (8) respectively. When the high-pressure chamber (7) reaches the set inflation pressure 1, control the filling valve 1 to close. When the double-membrane chamber (8) reaches the set inflation pressure 2, control the filling valve 2 to close. After the filling valves 1 and 2 are closed, control the outlet valve 1 to close. Step 7: Control the pressure relief valve to open, and use the double membrane air relief pipeline (14) to quickly relieve the pressure of the double membrane chamber (8), so that the pressure difference between the high-pressure chamber (7) and the double membrane chamber (8) increases instantly. The instantly increased pressure difference causes the gas in the high-pressure chamber (7) to break through the diaphragm one (5) and the diaphragm two (6) at high speed and enter the explosion chamber (16). Under the impetus of the high-speed airflow, the explosion gas produces a series of compression waves and quickly superimposes to form a shock wave. The compression effect of the shock wave causes the temperature and pressure of the explosion gas in the explosion chamber (16) to rise sharply. At the same time, when the explosion gas is compressed again by the reflected shock wave formed after passing through the end of the explosion chamber (16), its temperature and pressure further increase, and then global self-ignition occurs within a microsecond time and quickly expands into an explosion.

9. The methane in-situ explosion fracturing method based on shock wave ignition according to claim 8, characterized in that: In step 5, set the time to 1 to 2 hours.

10. The methane in-situ explosion fracturing method based on shock wave ignition according to claim 8, characterized in that: In step six, the second inflation pressure is half of the first inflation pressure.

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