Experimental apparatus for hydroelectric fracturing with integrated multimodal tomography and its usage

Abstract

This invention relates to the fields of rock mass engineering and oil and gas enhancement technology, and particularly to an experimental apparatus and method for fracturing using the electrohydraulic effect integrated with multimodal tomography. A liquid medium container is connected to a reaction vessel via pipelines, a liquid medium heating tank, and an electronic heater. The inner cavity of the reaction vessel houses a test block base, a test block clamp, and a flexible sensing cover. A rock test block is placed inside the flexible sensing cover. The bottom of a pressure arm contacts the top of the flexible sensing cover. An electrode rod is installed in the middle of the cover, with its lower end connected to a discharge electrode located inside the energy-concentrating cover. The advantages are: the flexible sensing cover of this invention can quickly achieve circumferential pre-tightening and tight adhesion to the surface of the rock test block; the composite sensor array consists of alternately arranged UT transducers and ERT electrodes, and the spiral upward arrangement provides abundant ray intersection angles in the vertical direction of the rock test block, improving the longitudinal resolution of three-dimensional tomography.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rock mass engineering and oil and gas stimulation, and particularly relates to a liquid-electric effect fracturing experimental device integrated with multi-modal tomography and a use method thereof. BACKGROUND

[0002] With the development of global energy resources to deep / ultra-deep oil and gas, hot dry rock and other unconventional resources, reservoir reconstruction technology is facing severe challenges. High-voltage electric pulse (HVEP) rock breaking technology has become a potential next-generation reservoir reconstruction technology due to its low cracking pressure, complex fracture network and environmental friendliness. However, the existing high-voltage electric pulse experimental device has some defects:

[0003] 1. "Black box" operation: the traditional device cannot observe the cracking and expansion process of the internal cracks of the rock in real time in a high-temperature and high-pressure and liquid medium environment;

[0004] 2. Characterization lag: at present, CT scanning after the experiment is mainly relied on for static characterization, and the dynamic spatiotemporal information (4D information) of crack evolution cannot be obtained, which leads to deviation in the understanding of the rock breaking mechanism;

[0005] 3. Complicated operation: the sensor installation is complex, and it is easy to fail or signal distortion in a high-pressure environment. Therefore, an intelligent experimental equipment capable of simulating a real formation environment and inverting the three-dimensional morphology of the internal cracks of the rock in real time through a non-destructive method is urgently needed. SUMMARY

[0006] The present application is aimed at the above-mentioned defects in the prior art, and provides a liquid-electric effect fracturing experimental device integrated with multi-modal tomography and a use method thereof, which can simulate a deep formation environment and perform real-time, in-situ and three-dimensional dynamic observation on the liquid-electric effect rock breaking process.

[0007] The present invention discloses an experimental apparatus for hydroelectric fracturing based on integrated multimodal tomography, the technical solution of which includes a reaction vessel, a reaction vessel base, and a computer system. The bottom of the reaction vessel is mounted on the reaction vessel base. The apparatus also includes a liquid medium container, an electronic heater, a liquid medium heating tank, a liquid pressurizing pump, an axial hydraulic pressurizing pump, a pressurizing arm, an electrode rod, a test block base, a test block clamp, a flexible sensing cover, a focusing cover, and a discharge electrode. The top of the liquid medium container is connected to the liquid medium heating tank via a pipeline. An electronic heater is installed inside the liquid medium heating tank. The outlet of the liquid medium heating tank is connected to the reaction vessel via a pipeline and the liquid pressurizing pump. The sidewalls and bottom of the reactor are connected to a liquid medium container via a reflux line for injecting conductive liquid medium into the reactor and providing confining pressure. The reactor's inner cavity is fitted with a test block base, a test block clamp, and a flexible sensing cover. The upper part of the test block base is fixed to the flexible sensing cover by the test block clamp. A rock test block is placed inside the flexible sensing cover. An axial hydraulic pressure pump is installed on the top cover of the reactor. The output end of the axial hydraulic pressure pump is connected to a pressure arm, the bottom of which contacts the top of the flexible sensing cover. An electrode rod is installed in the middle of the cover, the lower end of which is connected to a discharge electrode located inside the energy-concentrating cover.

[0008] Preferably, the aforementioned flexible sensing cover includes a flexible cover body, UT transducers, ERT electrodes, and signal cables. Multiple UT transducers and multiple ERT electrodes are distributed on the inner wall of the flexible cover body to form a spiral-distributed composite sensor array. The multiple UT transducers and multiple ERT electrodes are connected in series through multiple signal cables to form a bundled signal cable.

[0009] Preferably, the unfolded surface of the above-mentioned flexible protective cover body is a rectangular structure, wherein one end is provided with a rough surface fastening structure and the other end is provided with a hook surface fastening structure. The flexible protective cover body wraps around the rock sample block and is movably connected through the rough surface fastening structure and the hook surface fastening structure.

[0010] Preferably, the energy focusing cover is a rigid insulating cover with a hemispherical, parabolic, frustum, or flared structure. The upper end of the energy focusing cover is provided with an internal thread, which is threaded to the lower end of the electrode rod. The discharge electrode at the lower end of the electrode rod is located inside the rigid insulating cover of the energy focusing cover.

[0011] Preferably, the aforementioned clustered signal cable passes through the liquid medium inside the reactor and is then collected and transmitted to the computer system via a digital transmission module located on the side wall of the reactor.

[0012] Preferably, a digital temperature sensor is installed on the side wall of the reactor, the temperature sensor head is located in the inner cavity of the reactor, and the data from the digital temperature sensor is connected to a computer system via a data cable.

[0013] Preferably, a digital control valve is installed on the pipeline between the liquid pressurizing pump and the liquid inlet on the side wall of the reactor, and a digital pressure sensor is installed at the liquid inlet on the side wall of the reactor. The data from the liquid pressurizing pump and the digital pressure sensor are collected and transmitted to the computer system via data lines.

[0014] Preferably, the bottom of the above-mentioned reactor is provided with a liquid outlet, which is located on the outside of the test block base. An electronic insulating rubber plug is installed on the liquid outlet. The liquid outlet is connected to the liquid medium container through the reactor base via a reflux pipeline. A reflux digital control valve and a reflux liquid pressurizing pump are installed on the reflux pipeline. The control terminal of the reflux liquid pressurizing pump is connected to the computer system via a signal line.

[0015] The method of using the electrohydraulic effect fracturing experimental device integrating multimodal tomography mentioned in this invention includes the following steps:

[0016] I. Assembly equipment:

[0017] The flexible protective cover is wrapped around the rock sample block. It is then bonded in a staggered manner using a rough-surface fastening structure and a hook-surface fastening structure to achieve circumferential pre-tightening and tight fit to the surface of the rock sample block. The flexible sensing cover wrapped around the rock sample block is then placed in the sample block clamp inside the reactor and fixed. The cover with a pressure arm and an electrode rod is then installed on the upper part of the reactor. An axial hydraulic pressure pump is installed on the cover so that the bottom of the pressure arm contacts the top of the flexible sensing cover. The discharge electrode at the lower end of the electrode rod and the energy focusing cover are placed in the middle of the rock sample block inside the flexible sensing cover.

[0018] The flexible shield body is made of oil-resistant and high-temperature resistant rubber material, and a composite sensor array with a spiral distribution is embedded in the inner wall of the flexible shield body. In addition, a discharge electrode is connected to the end of the electrode rod, and the discharge electrode is located inside the energy focusing shield. The electrode rod and the energy focusing shield are connected by threads to facilitate the replacement of different energy focusing shields. The energy focusing shield is made of PEEK or ceramic and has a hemispherical, parabolic, frustum, or trumpet-shaped structure.

[0019] II. Baseline Scan:

[0020] The liquid pressurization pump is turned on, and a conductive liquid medium is injected into the reactor through the liquid medium container. The liquid medium is heated by an electronic heater, thereby heating and pressurizing the conductive liquid medium injected into the reactor to the preset working conditions to provide confining pressure for the rock specimen. The axial hydraulic pressurization pump is controlled to apply axial pressure to the top of the flexible sensing cover by the pressurization arm. Then, a benchmark scan is performed, and a joint scan of the UT transducer and ERT electrode is performed to establish the initial three-dimensional model of the rock specimen.

[0021] III. Discharge and Real-time Imaging:

[0022] The discharge electrode is activated by a computer system. Located inside the energy-concentrating hood, the discharge electrode triggers a high-voltage pulse discharge, which confines and converges the omnidirectional shock wave generated by the electrohydraulic effect, spraying a high-speed water jet to crack the rock sample along a preset direction. If the computer system indicates that the crack has not yet started, the voltage amplitude of the next pulse is increased to control the discharge electrode to discharge again. The discharge stops when the main crack is detected to have penetrated to the boundary. At the same time, after the rock sample cracks, a joint scan of a composite sensor array consisting of UT transducers and ERT electrodes is performed to obtain a three-dimensional model of the rock sample. Since the composite sensor array consists of alternating UT transducers and ERT electrodes, the spiral upward arrangement can provide ray intersection angles in the vertical direction of the rock sample, improving the longitudinal resolution of the three-dimensional tomographic imaging.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] I. This invention wraps the flexible protective cover around the rock sample block, using a combination of rough and hook-and-loop fastening structures for staggered bonding, which allows for rapid circumferential pre-tightening and tight adhesion of the rock sample block surface. An electronic heater heats and pressurizes the conductive liquid medium injected into the reactor to a preset operating condition, providing confining pressure to the rock sample block. Controlling the axial hydraulic pressurization pump applies axial pressure to the top of the flexible sensing cover via a pressurization arm, improving experimental efficiency.

[0025] 2. The discharge electrode of the present invention is located inside the energy-concentrating cover with a hemispherical, parabolic, frustum, or funnel-shaped structure. The discharge electrode triggers a high-voltage pulse discharge, which binds and converges the omnidirectional shock wave generated by the liquid-electric effect, and sprays a high-speed water jet, thereby causing the rock sample to crack along a preset direction. In addition, by combining the energy-concentrating cover with real-time feedback control, the crack path of the rock sample can be actively induced and controlled.

[0026] Third, after the rock specimen cracks, a joint scan of a composite sensor array consisting of UT transducers and ERT electrodes is performed to obtain a three-dimensional model of the rock specimen. Since the composite sensor array is composed of alternately arranged UT transducers and ERT electrodes, the spiral upward arrangement can provide the ray intersection angle in the vertical direction of the rock specimen, which improves the longitudinal resolution of the three-dimensional tomographic imaging and realizes the full-cycle three-dimensional dynamic observation from the "initial state before the experiment" to the "dynamic expansion during the experiment" and then to the "final form after the experiment". Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall system structure of the present invention;

[0028] Figure 2 This is a schematic diagram of the flexible sensing sleeve.

[0029] Figure 3 This is a schematic diagram of the unfolded internal structure of the flexible sensing sleeve;

[0030] Figure 4 This is a schematic diagram of the cross-sectional structure of the energy-concentrating shield;

[0031] In the diagram: Liquid medium container 101, electronic heater 102, liquid pressurization pump 103, digital control valve 104, digital pressure sensor 105, axial hydraulic pressurization pump 106, pressurization arm 107, electrode rod 108, lifting ring 109, electrode rod clamp 110, reaction vessel 111, digital transmission module 112, digital temperature sensor 113, test block base 114, test block clamp 115, flexible sensing cover 116, energy focusing cover 118, discharge electrode 119, bundled signal cable 120, reaction vessel base 121, electronic insulating rubber stopper 122, computer system 123, liquid medium heating tank 124, reflux digital control valve 125, reflux liquid pressurization pump 126;

[0032] Rock test block 201, flexible protective cover body 202, rough surface fastening structure 203, hook surface fastening structure 204, UT transducer 205, ERT electrode 206, signal cable 207, rigid insulating cover 301, internal thread 302. Detailed Implementation

[0033] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0034] Example 1, referring to Figures 1-4The present invention discloses an experimental apparatus for hydroelectric fracturing based on integrated multimodal tomography, comprising a reaction vessel 111, a reaction vessel base 121, and a computer system 123. The bottom of the reaction vessel 111 is mounted on the reaction vessel base 121. The apparatus also includes a liquid medium container 101, an electronic heater 102, a liquid medium heating tank 124, a liquid pressurization pump 103, an axial hydraulic pressurization pump 106, a pressurization arm 107, an electrode rod 108, a test block base 114, a test block clamp 115, a flexible sensing cover 116, a focusing cover 118, and a discharge electrode 119. The top of the liquid medium container 101 is connected to the liquid medium heating tank 124 via a pipeline. The electronic heater 102 is installed inside the liquid medium heating tank 124. The outlet of the liquid medium heating tank 124 is connected to the side wall of the reaction vessel 111 via a pipeline and the liquid pressurization pump 103. The bottom of the reactor 111 is connected to the liquid medium container 101 via a reflux line for injecting conductive liquid medium into the reactor 111 and providing confining pressure. The inner cavity of the reactor 111 is equipped with a test block base 114, a test block clamp 115, and a flexible sensing cover 116. The upper part of the test block base 114 is fixed to the flexible sensing cover 116 via the test block clamp 115. A rock test block 201 is installed inside the flexible sensing cover 116. An axial hydraulic pressurizing pump 106 is installed on the top cover of the reactor 111. The output end of the axial hydraulic pressurizing pump 106 is connected to a pressurizing arm 107. The bottom of the pressurizing arm 107 contacts the top of the flexible sensing cover 116. An electrode rod 108 is installed in the middle of the cover via an electrode rod clamp 110. The lower end of the electrode rod 108 is connected to a discharge electrode 119, and the discharge electrode 119 is located inside the energy focusing cover 118.

[0035] A lifting ring 109 is also installed on the upper surface of the top cover of the reactor 111 for easy installation.

[0036] Reference Figure 2 and Figure 3 The flexible sensing cover 116 mentioned in this invention includes a flexible cover body 202, a UT transducer 205, an ERT electrode 206, and a signal cable 207. Multiple UT transducers 205 and multiple ERT electrodes 206 are distributed on the inner wall of the flexible cover body 202 to form a spiral-distributed composite sensor array. Multiple UT transducers 205 and multiple ERT electrodes 206 are connected in series through multiple signal cables 207 to form a bundled signal cable 120.

[0037] Reference Figure 3 The flexible protective cover body 202 mentioned in this invention has a rectangular structure when unfolded. One end is provided with a rough surface fastening structure 203, and the other end is provided with a hook surface fastening structure 204. The flexible protective cover body 202 wraps around the rock test block 201 and is movably connected through the rough surface fastening structure 203 and the hook surface fastening structure 204.

[0038] Reference Figure 4 The energy-concentrating cover 118 mentioned in this invention adopts a rigid insulating cover 301 with a flared mouth structure. An internal thread 302 is provided at the upper end of the energy-concentrating cover 118, which is threaded to the lower end of the electrode rod 108 through the internal thread 302. The discharge electrode 119 at the lower end of the electrode rod 108 is located inside the rigid insulating cover 301 with a flared mouth structure of the energy-concentrating cover 118.

[0039] The aforementioned clustered signal cable 120 passes through the liquid medium inside the reactor 111, and is then collected and transmitted to the computer system 123 via the digital transmission module 112 located on the side wall of the reactor 111.

[0040] A digital temperature sensor 113 is installed on the side wall of the aforementioned reactor 111. The temperature sensor head is located in the inner cavity of the reactor 111. The data from the digital temperature sensor 113 is connected to the computer system 123 via a data cable.

[0041] A digital control valve 104 is installed on the pipeline between the liquid pressurizing pump 103 and the liquid inlet on the side wall of the reactor 111, and a digital pressure sensor 105 is installed at the liquid inlet on the side wall of the reactor 111. The data from the liquid pressurizing pump 103 and the digital pressure sensor 105 are collected and transmitted to the computer system 123 via data lines.

[0042] The bottom of the aforementioned reactor 111 is provided with a liquid outlet, which is located outside the test block base 114. An electronic insulating rubber plug 122 is installed on the liquid outlet. The liquid outlet is connected to the liquid medium container 101 through the reactor base 121 via a reflux pipeline. A reflux digital control valve 125 and a reflux liquid pressurization pump 126 are installed on the reflux pipeline. The control terminal of the reflux liquid pressurization pump 126 is connected to the computer system 123 via a signal line.

[0043] The method of using the electrohydraulic effect fracturing experimental device integrating multimodal tomography mentioned in this invention includes the following steps:

[0044] I. Assembly equipment:

[0045] The flexible protective cover body 202 is wrapped around the outer periphery of the rock sample 201. The rock sample 201 is pre-tightened and tightly fitted around the surface of the rock sample 201 by means of the rough surface fastening structure 203 and the hook surface fastening structure 204. Then, the flexible sensing cover 116 wrapped with the rock sample 201 is placed in the sample clamp 115 inside the reactor 111 and fixed. Then, the cover with the pressure arm 107 and the electrode rod 108 is installed on the upper part of the reactor 111. An axial hydraulic pressure pump 106 is installed on the cover so that the bottom of the pressure arm 107 contacts the top of the flexible sensing cover 116. The discharge electrode 119 at the lower end of the electrode rod 108 and the energy focusing cover 118 are placed in the middle of the rock sample 201 inside the flexible sensing cover 116.

[0046] The flexible shield body 202 is made of oil-resistant and high-temperature resistant rubber material, and a composite sensor array with a spiral distribution is embedded in the inner wall of the flexible shield body 202. In addition, a discharge electrode 119 is connected to the end of the electrode rod 108, and the discharge electrode 119 is located inside the energy focusing shield 118. The electrode rod 108 and the energy focusing shield 118 are connected by a thread 302 to facilitate the replacement of different energy focusing shields 118. The energy focusing shield 118 is made of PEEK or ceramic and has a flared structure.

[0047] II. Baseline Scan:

[0048] The liquid pressurization pump 103 is turned on, and a conductive liquid medium is injected into the reaction vessel 111 through the liquid medium container 101. The liquid medium is heated by the electronic heater 102, thereby heating and pressurizing the conductive liquid medium injected into the reaction vessel 111 to a preset working condition, such as a temperature of 80°C and a confining pressure of 20MPa, to provide confining pressure for the rock specimen 201. The axial hydraulic pressurization pump 106 is controlled to apply axial pressure to the top of the flexible sensing cover 116 by the pressurization arm 107. Then, a reference scan is performed, and a joint scan of the UT transducer 205 and the ERT electrode 206 is performed to establish an initial three-dimensional model of the rock specimen 201.

[0049] III. Discharge and Real-time Imaging:

[0050] The computer system 123 controls the activation of the discharge electrode 119, which is located inside the energy-concentrating shield 118. The discharge electrode 119 triggers a high-voltage pulse discharge, which confines and converges the omnidirectional shock wave generated by the electrohydraulic effect, and sprays a high-speed water jet to crack the rock specimen 201 along a preset direction. If the computer system 123 shows that the crack has not yet started, the voltage amplitude of the next pulse is increased to control the discharge electrode 119 to discharge again. The discharge stops when the main crack is detected to have penetrated to the boundary. At the same time, after the rock specimen 201 cracks, a joint scan of the composite sensor array composed of UT transducer 205 and ERT electrode 206 is performed to obtain a three-dimensional model of the rock specimen 201. Since the composite sensor array is composed of alternately arranged UT transducers 205 and ERT electrodes 206, the spiral upward arrangement can provide the ray intersection angle in the vertical direction of the rock specimen 201, which improves the longitudinal resolution of the three-dimensional tomographic imaging.

[0051] Example 2: The present invention provides an experimental apparatus for hydroelectric fracturing based on integrated multimodal tomography, comprising a reaction vessel 111, a reaction vessel base 121, and a computer system 123. The bottom of the reaction vessel 111 is mounted on the reaction vessel base 121. The apparatus also includes a liquid medium container 101, an electronic heater 102, a liquid medium heating tank 124, a liquid pressurization pump 103, an axial hydraulic pressurization pump 106, a pressurization arm 107, an electrode rod 108, a lifting ring 109, an electrode rod clamp 110, a test block base 114, a test block clamp 115, a flexible sensing cover 116, a focusing cover 118, and a discharge electrode 119. The top of the liquid medium container 101 is connected to the liquid medium heating tank 124 via a pipeline. The electronic heater 102 is installed inside the liquid medium heating tank 124. The outlet of the liquid medium heating tank 124 is connected to the reaction vessel base 124 via a pipeline and the liquid pressurization pump 103. The side wall and bottom of the reactor 111 are connected to a liquid medium container 101 via a reflux line for injecting a conductive liquid medium into the reactor 111 and providing confining pressure. The inner cavity of the reactor 111 is equipped with a test block base 114, a test block clamp 115, and a flexible sensing cover 116. The upper part of the test block base 114 is fixed to the flexible sensing cover 116 by the test block clamp 115. A rock test block 201 is installed inside the flexible sensing cover 116. An axial hydraulic pressurizing pump 106 is installed on the top cover of the reactor 111. The output end of the axial hydraulic pressurizing pump 106 is connected to a pressurizing arm 107. The bottom of the pressurizing arm 107 contacts the top of the flexible sensing cover 116. An electrode rod 108 is installed in the middle of the cover by an electrode rod clamp 110. The lower end of the electrode rod 108 is connected to a discharge electrode 119, and the discharge electrode 119 is located inside the energy focusing cover 118.

[0052] The difference from Example 1 is:

[0053] The energy-concentrating cover 118 mentioned in this embodiment is made of PEEK or ceramic and has a hemispherical, parabolic or frustum-shaped structure. It can also perform the above functions to confine and converge the omnidirectional shock wave generated by the electrohydraulic effect, and spray a high-speed water jet to crack the rock specimen 201 along a preset direction.

[0054] The above description is merely a partial preferred embodiment of the present invention. Any person skilled in the art can modify the above-described technical solutions or modify them into equivalent technical solutions. Therefore, any simple modifications or equivalent transformations made based on the technical solutions of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. An integrated multi-modal tomography liquid electro-effect fracturing experiment device, comprising a reaction kettle (111), a reaction kettle base (121) and a computer system (123), the bottom of the reaction kettle (111) is installed on the reaction kettle base (121), characterized in that: Also include a liquid medium container (101), electronic heater (102), liquid medium heating tank (124), liquid pressure pump (103), axial hydraulic pressure pump (106), pressurizing arm (107), electrode rod (108), test block base (114), test block clamp (115), flexible sensing cover (116), energy gathering cover (118), discharge electrode (119), the top of the liquid medium container (101) is connected to the liquid medium heating tank (124) through the pipeline, the electronic heater (102) is installed in the liquid medium heating tank (124), the outlet of the liquid medium heating tank (124) is connected to the sidewall of the reaction kettle (111) through the pipeline and the liquid pressure pump (103), the bottom of the reaction kettle (111) is connected to the liquid medium container (101) through the reflux pipeline, which is used for injecting the conductive liquid medium into the reaction kettle (111) and providing the confining pressure; the inner cavity of the reaction kettle (111) is installed with the test block base (114), the test block clamp (115) and the flexible sensing cover (116), the upper part of the test block base (114) is fixed with the flexible sensing cover (116) through the test block clamp (115), the rock test block (201) is installed in the flexible sensing cover (116), the axial hydraulic pressure pump (106) is installed on the top cover of the reaction kettle (111), the output end of the axial hydraulic pressure pump (106) is connected to the pressurizing arm (107), the bottom of the pressurizing arm (107) is in contact with the top of the flexible sensing cover (116), the electrode rod (108) is installed in the middle of the cover, the lower end of the electrode rod (108) is connected to the discharge electrode (119), and the discharge electrode (119) is located in the energy gathering cover (118); The flexible sensing cover (116) comprises a flexible cover body (202), a UT transducer (205) and an ERT electrode (206), a plurality of UT transducers (205) and a plurality of ERT electrodes (206) are alternately arranged on the inner wall of the flexible cover body (202), forming a spiral line distributed composite sensor array.

2. The integrated multi-modality tomographic liquid electroeffect cracking experiment device according to claim 1, characterized in that: A plurality of UT transducers (205) and a plurality of ERT electrodes (206) are connected in series through a plurality of signal cables (207) to form a bundled signal cable (120).

3. The integrated multi-modality tomographic liquid electroeffect cracking experiment device according to claim 2, characterized in that: The flexible cover body (202) has a rectangular structure, one end of which is provided with a rough surface buckling structure (203), and the other end is provided with a hook surface buckling structure (204), the flexible cover body (202) is wrapped around the rock test block (201) and is movably connected through the rough surface buckling structure (203) and the hook surface buckling structure (204).

4. The integrated multi-modal tomographic imaging and electrohydraulic fracturing apparatus of claim 3, wherein: The energy gathering cover (118) adopts a rigid insulating cover body (301) with a hemispherical, parabolic, circular truncated cone or horn structure, an inner thread (302) is arranged at the upper end of the energy gathering cover (118), the lower end of the electrode rod (108) is threadedly connected with the inner thread (302), and the discharge electrode (119) at the lower end of the electrode rod (108) is located in the rigid insulating cover body (301) of the energy gathering cover (118).

5. The integrated multi-modal tomographic imaging and electrohydraulic fracturing apparatus of claim 4, wherein: The bundled signal cable (120) passes through the liquid medium inside the reactor (111) and is then collected and transmitted to the computer system (123) via the digital transmission module (112) located on the side wall of the reactor (111).

6. The integrated multi-modal tomographic imaging and electrohydraulic fracturing apparatus of claim 5, wherein: A digital temperature sensor (113) is installed on the side wall of the reactor (111), and the temperature measuring head is located in the inner cavity of the reactor (111). The data of the digital temperature sensor (113) is connected to the computer system (123) through a data cable.

7. The integrated multi-modal tomographic liquid electroeffect cracking experiment device according to claim 6, characterized in that: A digital control valve (104) is installed on the pipeline between the liquid pressurizing pump (103) and the liquid inlet on the side wall of the reactor (111), and a digital pressure sensor (105) is installed at the liquid inlet on the side wall of the reactor (111). The data from the liquid pressurizing pump (103) and the digital pressure sensor (105) are collected and transmitted to the computer system (123) through data lines.

8. The integrated multi-modality tomographic liquid electroeffect cracking experiment device according to claim 7, characterized in that: The bottom of the reactor (111) is provided with a liquid outlet, which is located outside the test block base (114). An electronic insulating rubber plug (122) is installed on the liquid outlet. The liquid outlet is connected to the liquid medium container (101) through the reactor base (121) via a reflux pipeline. A reflux digital control valve (125) and a reflux liquid pressurizing pump (126) are installed on the reflux pipeline. The control terminal of the reflux liquid pressurizing pump (126) is connected to the computer system (123) via a signal line.

9. A method of using the integrated multi-modal tomographic liquid electroeffect fracturing experiment device according to claim 8, characterized in that: Includes the following processes: I. Assembly equipment: The flexible shield body (202) is wrapped around the outer periphery of the rock sample (201). The rock sample (201) is pre-tightened and tightly fitted in the circumferential direction by means of the rough surface fastening structure (203) and the hook surface fastening structure (204). Then, the flexible sensing shield (116) wrapped with the rock sample (201) is placed in the test block clamp (115) in the reactor (111) and fixed. Then, the cover with the pressure arm (107) and the electrode rod (108) is installed on the upper part of the reactor (111). An axial hydraulic pressure pump (106) is installed on the cover so that the bottom of the pressure arm (107) contacts the top of the flexible sensing shield (116). The discharge electrode (119) at the lower end of the electrode rod (108) and the energy focusing cover (118) are placed in the middle of the rock sample (201) in the flexible sensing shield (116). The flexible shield body (202) is made of oil-resistant and high-temperature resistant rubber material. The inner wall of the flexible shield body (202) is pre-embedded with a composite sensor array with a spiral distribution. In addition, a discharge electrode (119) is connected to the end of the electrode rod (108), and the discharge electrode (119) is located inside the energy focusing shield (118). The electrode rod (108) and the energy focusing shield (118) are connected by a thread (302) to facilitate the replacement of different energy focusing shields (118). The energy focusing shield (118) is made of PEEK or ceramic and is in the shape of a hemispherical, parabolic, frustum or horn mouth structure. II. Baseline Scan: The liquid pressurizing pump (103) is started, the electrically conductive liquid medium is injected into the reaction kettle (111) through the liquid medium container (101), and heated by the electronic heater (102), so that the electrically conductive liquid medium injected into the reaction kettle (111) is heated and pressurized to a preset working condition, and the confining pressure of the rock test block (201) is provided; the axial hydraulic pressurizing pump (106) is controlled to make the pressurizing arm (107) apply axial pressure to the top of the flexible sensing cover (116); then the reference scanning is carried out, the combined scanning of the UT transducer (205) and the ERT electrode (206) is performed once, and the initial three-dimensional model of the rock test block (201) is established; III. Discharge and real-time imaging: The computer system (123) controls the discharge electrode (119) to start, the discharge electrode (119) is located in the energy gathering cover (118), the discharge electrode (119) triggers high-voltage pulse discharge, binds and converges the omnidirectional shock wave beam generated by the liquid-electric effect, sprays high-speed water jet, and cracks the rock test block (201) along the preset direction; if the computer system (123) shows that the crack has not been cracked, the voltage amplitude of the next pulse is increased to control the discharge electrode (119) to discharge again; until it is detected that the main crack has penetrated to the boundary, the discharge is stopped; at the same time, after the rock test block (201) is cracked, the combined scanning of the composite sensor array composed of the UT transducer (205) and the ERT electrode (206) is performed, and the three-dimensional model of the rock test block (201) is obtained. Since the composite sensor array is composed of the UT transducer (205) and the ERT electrode (206) arranged alternately, the spiral ascending arrangement can provide a ray crossing angle in the vertical direction of the rock test block (201), and the longitudinal resolution of three-dimensional tomography is improved.

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