High-voltage electric pulse and water pressure combined fracturing dry hot rock true triaxial experimental device and method

Abstract

The application discloses a high-voltage electric pulse composite water pressure fracturing dry hot rock true triaxial experiment device and method, aims at simulating the water pressure fracturing effect of dry hot rock after being subjected to high-voltage electric pulse under the temperature field and the ground stress state of the dry hot rock, and aims at exploring the damage behavior, damage criterion and law of the dry hot rock. Therefore, the experiment device provided by the application comprises a true triaxial stress loading mechanism for applying three-dimensional stress to the dry hot rock sample, a heating mechanism for heating the dry hot rock sample, a high-voltage electric pulse mechanism for applying high-voltage electric pulse to the upper surface of the dry hot rock sample, and a water pressure fracturing mechanism for applying fracturing water pressure to the upper surface of the dry hot rock sample.

Description

Technical Field

[0001] This invention belongs to the field of artificial thermal reservoir construction technology for hot dry rock, and particularly relates to a true triaxial experimental device and method for fracturing hot dry rock by high-voltage electric pulse combined with water pressure. Background Technology

[0002] The primary task in developing hot dry rock reservoirs is to create artificial thermal reservoirs thousands of meters underground using hydraulic fracturing technology. Cold fluids are then injected into the formation, circulating between the injection well, the artificial reservoir, and the production well, exchanging heat with the hot dry rock reservoir to extract thermal energy for surface heating, power generation, and other applications. However, the directionality and uncertainty of artificial fractures created by hydraulic fracturing prevent satisfactory hydraulic conductivity between the injection and production wells. Therefore, high-pressure pulsed discharge technology is typically used before hydraulic fracturing to create numerous directional fractures on the surface of the hot dry rock reservoir, controlling the direction of fracture extension and forming a fracture system connecting the injection and production wells to establish the artificial thermal reservoir. However, research shows that the effects of high-pressure pulsed discharge and hydraulic fracturing vary significantly depending on the temperature field and stress state of the hot dry rock. Therefore, obtaining optimal fracturing parameters is a critical technical problem that urgently needs to be solved.

[0003] In summary, it is necessary to develop an experimental device that can simulate the actual temperature field and geostress state of hot dry rocks under high-voltage electric pulses to investigate the failure behavior, failure criteria, and laws of hot dry rocks. Summary of the Invention

[0004] The main objective of this invention is to provide a true triaxial experimental apparatus and method for high-voltage electric pulse combined with hydraulic fracturing of dry hot rock, which aims to simulate the hydraulic fracturing effect of dry hot rock under the actual temperature field and geostress state after being subjected to high-voltage electric pulse, so as to explore the failure behavior, failure criteria and laws of dry hot rock.

[0005] To this end, one aspect of the present invention provides a high-voltage electric pulse combined with water pressure fracturing true triaxial experimental apparatus for dry hot rock, comprising:

[0006] A true triaxial stress loading mechanism is used to apply a three-dimensional stress field to a dry hot rock sample;

[0007] The heating mechanism is used to heat the dry hot rock sample to simulate the temperature environment that the dry hot rock sample is in in actual engineering.

[0008] A high-voltage electric pulse mechanism is used to apply a high-voltage electric pulse to the upper surface of a hot dry rock sample to induce directional cracks on the surface of the hot dry rock sample.

[0009] A hydraulic fracturing mechanism is used to apply fracturing water pressure to the upper surface of a hot dry rock sample to force the directional fractures to extend into the depth of the hot dry rock sample.

[0010] Specifically, the true triaxial stress loading mechanism includes an upper loading pad, a lower loading pad, a front loading pad, a rear loading pad, a left loading pad, a right loading pad, and a loading rod for loading each loading pad.

[0011] Specifically, each corner of the hot dry rock sample is wrapped with an insulating heat-conducting box, and the insulating heat-conducting box, together with the upper loading pad, lower loading pad, front loading pad, rear loading pad, left loading pad, and right loading pad, forms a loading chamber adapted to the hot dry rock sample.

[0012] Specifically, the upper loading pad has a hollow cavity on the end face that contacts the dry hot rock sample, and an insulating sealing gasket surrounding the hollow cavity is placed between the upper loading pad and the upper surface of the dry hot rock sample.

[0013] The electrodes of the high-voltage electric pulse mechanism are disposed in the hollow cavity, and the water pressure fracturing mechanism directly injects fracturing water into the hollow cavity.

[0014] Specifically, the heater of the heating mechanism includes an upper heater and a lower heater that can operate independently;

[0015] The upper heater is located around the upper part of the dry hot rock sample, and the lower heater is located around the lower part of the dry hot rock sample.

[0016] Specifically, the heating mechanism is a heating furnace, and each of the loading pads is disposed outside the heating furnace and extends into the heating furnace. The loading pads are slidably connected to the furnace wall of the heating furnace.

[0017] Specifically, the water pressure fracturing mechanism includes a water tank, a water injection pipe, a water injection pump, and a pressure sensor. The upper loading pad is provided with a water injection channel that communicates with the bottom of the hollow cavity. One end of the water injection channel is connected to the bottom of the hollow cavity. One end of the water injection pipe is connected to the water injection channel, and the other end is connected to the water tank. The water injection pump and the pressure sensor are mounted on the water injection pipe.

[0018] Specifically, it also includes a liquid nitrogen cooling mechanism, which includes a liquid nitrogen source, a liquid nitrogen delivery pipe, and a liquid nitrogen delivery pump. The liquid nitrogen source is connected to the water injection channel through the liquid nitrogen delivery pipe, and the liquid nitrogen delivery pump is installed on the liquid nitrogen delivery pipe.

[0019] Specifically, the water injection channel is equipped with a control valve that allows it to connect selectively to either the liquid nitrogen delivery pipe or the water injection pipe.

[0020] A high-voltage electrical pulse combined with hydraulic fracturing method for hot dry rock includes:

[0021] Sampling equipment was used to obtain rock samples of the dry hot rock to be developed, and the actual temperature and actual geostress state of the rock samples were obtained.

[0022] Several dry hot rock samples were prepared from the aforementioned rock samples and tested using the aforementioned high-voltage electric pulse combined with hydraulic fracturing dry hot rock true triaxial experimental apparatus; among them,

[0023] During the experiment, the loading force of the true triaxial stress loading mechanism was adjusted to make the three-dimensional stress field of the hot dry rock sample match the actual geostress state of the rock sample. At the same time, the temperature of the hot dry rock sample was matched with the actual temperature of the rock sample by the heating mechanism.

[0024] By changing the pulse discharge parameters and the hydraulic fracturing parameters, the hydraulic fracturing depth of dry hot rock samples under different parameter states was obtained. All parameters and their corresponding hydraulic fracturing depth data were used as sample data, and a machine learning algorithm was used to train and construct a hydraulic fracturing fracture depth prediction model.

[0025] In actual production, the well group layout scheme is determined according to the depth and range of the hot dry rock reservoir. Hydraulic fracturing is carried out by injection wells and production wells facing each other. Before hydraulic fracturing, high-voltage electric pulses are applied to the well walls of injection wells and production wells through a high-voltage pulse device, so that directional fractures are generated on the surface of injection wells and production wells.

[0026] Based on the pulse discharge parameters determined in the actual production process, the hydraulic fracturing parameters are obtained when the hydraulic fracturing depth is half the distance between the injection well and the production well using the constructed hydraulic fracturing depth prediction model. The obtained hydraulic fracturing parameters are then used to guide actual production.

[0027] Specifically, the pulse discharge parameters include discharge frequency, discharge voltage, and number of discharges, and the water pressure fracturing parameters include injection pressure and injection rate.

[0028] Compared with the prior art, at least one embodiment of the present invention has the following beneficial effects: it can simulate the actual temperature field of hot dry rock and the hydraulic fracturing effect after being subjected to high-voltage electric pulse under geostress, so as to explore the failure behavior, failure criteria and laws of hot dry rock, and thus guide actual production. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a front view of the high-voltage electric pulse combined with water pressure fracturing dry hot rock true triaxial experimental device provided in an embodiment of the present invention;

[0031] Figure 2 This is a top view of the high-voltage electric pulse combined with water pressure fracturing dry hot rock true triaxial experimental device provided in the embodiment of the present invention;

[0032] Among them: 1. True triaxial stress loading mechanism; 101. Upper loading pad; 102. Lower loading pad; 103. Front loading pad; 104. Rear loading pad; 105. Left loading pad; 106. Right loading pad; 107. Loading rod; 2. Heating mechanism; 3. High-voltage electric pulse mechanism; 301. Electrode; 302. High-voltage electric pulse generating device; 4. Hydraulic fracturing mechanism; 401. Water tank; 402. Water injection pipe; 4 03. Water injection pump; 404. Pressure sensor; 5. Dry hot rock sample; 6. Hollowed-out cavity; 7. Insulating sealing gasket; 8. Upper heater; 9. Lower heater; 10. Temperature sensor; 11. Temperature display dial; 12. Thermal insulation sealing assembly; 13. Insulating heat conduction box; 14. Water injection channel; 15. Liquid nitrogen cooling mechanism; 151. Liquid nitrogen source; 152. Liquid nitrogen delivery pipe; 153. Liquid nitrogen delivery pump; 16. Control valve. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0035] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0036] See Figure 1 and Figure 2 A true triaxial experimental apparatus for fracturing dry hot rock using a combination of high-voltage electric pulse and hydraulic pressure includes a true triaxial stress loading mechanism 1, a heating mechanism 2, a high-voltage electric pulse mechanism 3, and a hydraulic fracturing mechanism 4. The true triaxial stress loading mechanism 1 is used to apply a three-dimensional stress field to the dry hot rock sample 5. The heating mechanism 2 is used to heat the dry hot rock sample 5 to simulate the temperature environment of the dry hot rock sample 5. The high-voltage electric pulse mechanism 3 is used to apply a high-voltage electric pulse to the upper surface of the dry hot rock sample 5 to generate directional cracks on the surface of the dry hot rock sample 5. The hydraulic fracturing mechanism 4 is used to apply fracturing hydraulic pressure to the upper surface of the dry hot rock sample 5 to force the directional cracks generated by the discharge of the high-voltage electric pulse mechanism 3 to extend into the depth of the dry hot rock sample 5.

[0037] The experimental setup described above operates as follows: A true triaxial load is applied to the hot dry rock sample 5 using a true triaxial stress loading mechanism 1. The heating mechanism 2 is adjusted to realistically simulate various complex temperature environments in actual engineering. Then, an electric pulse is applied to the upper surface of the hot dry rock sample 5 using a high-voltage electric pulse mechanism 3, forcing the formation of numerous directional cracks on the upper surface of the hot dry rock sample 5 and causing the original cracks to expand. Subsequently, a hydraulic fracturing mechanism 4 injects fracturing water into the upper surface of the hot dry rock sample 5, causing the cracks generated by the high-voltage electric pulse mechanism 3 to further extend into the core of the hot dry rock sample 5. By changing the pulse discharge parameters and the hydraulic fracturing parameters, the hydraulic fracturing effect after the hot dry rock is subjected to different high-voltage electric pulses under the actual temperature field and geostress state can be simulated to explore the failure behavior, failure criteria, and laws of hot dry rock, thereby guiding actual production.

[0038] See Figure 1 and Figure 2In some embodiments, the true triaxial stress loading mechanism 1 includes an upper loading pad 101, a lower loading pad 102, a front loading pad 103, a rear loading pad 104, a left loading pad 105, a right loading pad 106, and a loading rod 107 for loading each loading pad. A hollow cavity 6 is provided on the lower end surface of the upper loading pad 101. An insulating sealing gasket 7 surrounding the hollow cavity 6 is placed between the upper loading pad 101 and the upper surface of the dry hot rock sample 5. The positive and negative electrodes 301 of the high voltage pulse mechanism 3 are both disposed in the hollow cavity 6. The conductive wires of the electrodes 301 are sealed and passed through the upper loading pad 101 and connected to the high voltage pulse generating device 302. The hydraulic fracturing mechanism 4 directly injects fracturing water into the hollow cavity 6. When the high-voltage electric pulse mechanism 3 is working, the discharge end of the electrode is in close contact with the upper surface of the dry hot rock sample 5, and appropriate water is injected into the hollow cavity 6 through the hydraulic fracturing mechanism 4, so that the discharge end of the electrode 301 and the upper surface of the dry hot rock sample 5 are completely submerged. Since the breakdown field strength of the rock is less than that of the water, the high-voltage electric pulse will preferentially break down the rock and form a plasma channel inside the rock. Subsequently, the plasma channel expands due to heat, causing the sample to undergo tensile failure and generating a large number of cracks.

[0039] In this embodiment, a hollow cavity 6 is set between the upper loading pad 101 and the upper surface of the dry hot rock sample 5 to form a discharge space, simulating the water injection well or production well in the actual production process. Appropriate water is injected into the hollow cavity 6 to act as an insulating medium in the discharge process. This can realistically simulate the process of applying a high-voltage electric pulse to the well wall of the water injection well and production well in the actual production process, so the data obtained is more realistic and reliable.

[0040] See Figure 1 In some other embodiments, the heater of the heating mechanism 2 includes an upper heater 8 and a lower heater 9 that can operate independently, wherein the upper heater 8 is located around the upper part of the dry hot rock sample 5, and the lower heater 9 is located around the lower part of the dry hot rock sample 5.

[0041] In actual production, when applying high-voltage electric pulses to injection wells and production wells to induce fracturing, it is necessary to inject an insulating medium into the well to ensure that the high-voltage electric pulses preferentially penetrate the rock and form plasma channels inside the rock. The injection of the insulating medium will cause changes in the temperature field of the dry hot rock layer, causing the temperature of the dry hot rock near the well wall to decrease, while the temperature of the end away from the well wall remains at the original high temperature. In this embodiment, by designing the upper heater 8 and the lower heater 9 of the heating mechanism 2 to be independently controllable, the lower heater 9 is kept on when the high-voltage electric pulse is applied, so that the end of the dry hot rock sample 5 away from the high-voltage electric pulse mechanism 3 remains at the original high temperature (corresponding to the end of the actual dry hot rock layer away from the well wall), so that the experimental temperature conditions are as close as possible to the temperature field corresponding to the actual dry hot rock layer, in order to ensure the accuracy of the experiment.

[0042] Specifically, the heating mechanism 2 is a heating furnace. Each loading pad is set outside the heating furnace and extends into the heating furnace. The loading pad is slidably connected to the furnace wall. The temperature sensor 10 is attached to the inner wall of the upper right side of the furnace wall to monitor the temperature inside the furnace in real time and feed it back to the temperature display dial 11. The temperature controller is connected to the heating chamber through a control circuit pre-embedded in the furnace wall, which can realize sample heating under different heating rates, heating paths and heating methods.

[0043] A heat-insulating sealing component 12 is installed in the gap between the square hole opening in the furnace wall and the loading pad of the true triaxial stress loading mechanism 1. This component can achieve heat preservation inside the furnace without hindering the normal loading of each group of loading rods 107, thus concentrating the heat generated by the heater and achieving faster heating and better heat preservation.

[0044] Specifically, each corner of the hot dry rock sample 5 is wrapped by an insulating heat-conducting box 13. The insulating heat-conducting box 13, together with the upper loading pad 101, lower loading pad 102, front loading pad 103, rear loading pad 104, left loading pad 105, and right loading pad 106, forms a loading chamber adapted to the hot dry rock sample 5. By setting the insulating heat-conducting box 13, the influence range of the high-voltage electric pulse can be limited to the inside of the sample.

[0045] See Figure 1 In some embodiments, the hydraulic fracturing mechanism 4 includes a water tank 401, a water injection pipe 402, a water injection pump 403, and a pressure sensor 404. The upper loading pad 101 is provided with a water injection channel 14 that communicates with the bottom of the hollow cavity 6. One end of the water injection channel 14 is connected to the bottom of the hollow cavity 6. One end of the water injection pipe 402 is connected to the water injection channel 14, and the other end is connected to the water tank 401. The water injection pump 403 and the pressure sensor 404 are installed on the water injection pipe 402. The pressure sensor 404 is used to measure the hydraulic fracturing rupture pressure.

[0046] See Figure 1 In some embodiments, a liquid nitrogen cooling mechanism 15 is also included. The liquid nitrogen cooling mechanism 15 includes a liquid nitrogen source 151, a liquid nitrogen delivery pipe 152, and a liquid nitrogen delivery pump 153. The liquid nitrogen source 151 is connected to a water injection channel 14 via the liquid nitrogen delivery pipe 152. The liquid nitrogen delivery pump 153 is mounted on the liquid nitrogen delivery pipe 152. The water injection channel 14 is equipped with a control valve 16 that selectively connects it to either the liquid nitrogen delivery pipe 152 or the water injection pipe 402. In this embodiment, liquid nitrogen can also be introduced into the upper surface of the hot dry rock sample 5 to rapidly cool the rock and cause thermal shock damage. This allows for the investigation of the fracturing effect of hot dry rock under the coupled effects of thermal shock damage, high-voltage electric pulse fracturing, and water pressure fracturing.

[0047] The operation of the above-mentioned high-voltage electric pulse combined with water pressure fracturing dry hot rock true triaxial experimental device is as follows:

[0048] Step 1: Prepare the dry hot rock sample 5 to be tested. Place the dry hot rock sample 5 into the insulating heat-conducting box 13.

[0049] Step 2: Install loading pads in each direction, and keep the electrode 301 of the high voltage pulse mechanism 3 in close contact with the upper surface of the dry hot rock sample 5. Install an insulating sealing gasket 7 between the upper loading pad 101 and the upper surface of the dry hot rock sample 5 to form a sealed discharge space. Connect the water injection channel 14 on the upper loading pad 101 to the water injection pipe 402 of the water pressure fracturing mechanism 4.

[0050] Step 3: Start the heating furnace, heat the dry hot rock sample 5 to the specified temperature and keep the temperature constant to complete the application of the real-time temperature field;

[0051] Step 4: Start the true triaxial loading mechanism, pre-clamp the sample, fill with hydraulic oil, apply axial pressure and confining pressure to the specified state, and complete the application of the true triaxial stress field;

[0052] Step 5: Start the liquid nitrogen pumping device to fully cool the dry hot rock sample 5, which has been heated to the specified temperature, and cause thermal shock damage to the rock.

[0053] Step 6: Start the water injection pump 403 to inject the aqueous solution into the crack formed by liquid nitrogen cooling, and ensure that the upper surface of the sample and the discharge end of the electrode 301 are completely immersed in the water, thus completing the setting of the environment and required insulation conditions for high-voltage electric pulse rock breaking.

[0054] Step 7: Start the high-voltage electric pulse generator, adjust various pulse discharge parameters, apply high-voltage electric pulses to the rock sample, so that a large number of cracks are formed on the surface of the dry hot rock sample 5 and the original cracks are expanded. The pulse discharge parameters include discharge frequency, discharge voltage and discharge times.

[0055] Step 8: Activate the water pressure fracturing mechanism 4, and after adjusting the water pressure fracturing parameters to the set values, inject high-pressure water into the hollow cavity 6, forcing the microcracks formed by thermal shock and high-voltage electric pulse to extend towards the core of the sample to form a complex interconnected fracture system. The water pressure fracturing parameters include water injection pressure and water injection rate.

[0056] This application simulates the actual temperature field and geostress state of hot dry rocks, and by adjusting the pulse discharge parameters and water pressure fracturing parameters, it can obtain the failure behavior and laws of high-voltage electric pulse combined with water pressure fracturing of rocks under different pulse discharge parameters and water pressure fracturing parameters. It can carry out relevant research on hot dry rock reservoirs under high-voltage electric pulse combined with water pressure fracturing under laboratory conditions.

[0057] This application also discloses a high-voltage electrical pulse combined with hydraulic fracturing method for dry hot rock, including:

[0058] Sampling equipment was used to obtain rock samples of the dry hot rock to be developed, and the actual temperature and actual geostress state of the rock samples were obtained.

[0059] Several dry hot rock samples 5 were prepared from the above-mentioned rock samples, and experiments were conducted using the above-mentioned high-voltage electric pulse combined with water pressure fracturing dry hot rock true triaxial experimental apparatus; among which,

[0060] During the experiment, by adjusting the loading force of the true triaxial stress loading mechanism 1, the three-dimensional stress field of the dry hot rock sample 5 was made to match the actual geostress state of the rock sample. At the same time, the temperature of the dry hot rock sample 5 was made to match the actual temperature of the rock sample by the heating mechanism 2.

[0061] By changing the pulse discharge parameters and the hydraulic fracturing parameters, the hydraulic fracturing depth of dry hot rock sample 5 under different parameter states was obtained. All parameters and their corresponding hydraulic fracturing depth data were used as sample data, and a machine learning algorithm was used to train and construct a hydraulic fracturing fracture depth prediction model.

[0062] Subsequently, in actual production, the well group layout scheme was determined based on the depth and extent of the hot dry rock reservoir. Hydraulic fracturing was carried out by injection wells and production wells facing each other. Before hydraulic fracturing, high-voltage electrical pulses were applied to the well walls of the injection and production wells using a high-voltage pulse device, causing directional fractures to be generated on the surfaces of the injection and production wells; among which,

[0063] The process of determining hydraulic fracturing parameters in actual production is as follows:

[0064] Based on the pulse discharge parameters determined in the actual production process, the hydraulic fracturing parameters are obtained when the hydraulic fracturing depth is half the distance between the injection well and the production well using the constructed hydraulic fracturing depth prediction model. The obtained hydraulic fracturing parameters are then used to guide actual production.

[0065] Unless otherwise stated, if any of the technical solutions disclosed in this invention specify a numerical range, then the disclosed numerical range is a preferred numerical range. Anyone skilled in the art should understand that the preferred numerical range is merely one among many feasible numerical values ​​that has a more obvious or representative technical effect. Because there are many numerical values, it is impossible to list them all. Therefore, this invention discloses only some numerical values ​​to illustrate the technical solutions of this invention. Furthermore, the numerical values ​​listed above should not constitute a limitation on the scope of protection of this invention.

[0066] Furthermore, if the present invention discloses or relates to mutually fixedly connected components or structural parts, then unless otherwise stated, a fixed connection can be understood as: a detachable fixed connection (e.g., using bolts or screws), or a non-detachable fixed connection (e.g., riveting, welding). Of course, mutually fixed connections can also be replaced by an integral structure (e.g., manufactured using a casting process) (except where it is obviously impossible to use an integral molding process).

[0067] Furthermore, unless otherwise stated, the terms used to indicate positional relationships or shapes in any of the technical solutions disclosed in this invention include states or shapes that are similar to, analogous to, or close to those states or shapes. Any component provided by this invention can be assembled from multiple individual components or can be a single component manufactured using a one-piece molding process.

[0068] The above embodiments are merely illustrative examples to clearly illustrate the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for fracturing hot dry rock using a combination of high-voltage electrical pulses and hydraulic pressure, characterized in that, include: Sampling equipment was used to obtain rock samples of the dry hot rock to be developed, and the actual temperature and actual geostress state of the rock samples were obtained. Several dry hot rock samples (5) were prepared from the above rock samples and tested using a high-voltage electric pulse combined with water pressure fracturing dry hot rock true triaxial experimental apparatus; among them, The experimental apparatus includes: A true triaxial stress loading mechanism (1) is used to apply a three-dimensional stress field to a dry hot rock sample (5); Heating mechanism (2) is used to heat the dry hot rock sample (5); Its characteristic is that it further includes: A high-voltage electric pulse mechanism (3) is used to apply a high-voltage electric pulse to the upper surface of the hot dry rock sample (5) so as to generate directional cracks on the surface of the hot dry rock sample (5); The hydraulic fracturing mechanism (4) is used to apply fracturing hydraulic pressure to the upper surface of the hot dry rock sample (5) to force the directional fractures to extend into the depth of the hot dry rock sample (5). The true triaxial stress loading mechanism (1) includes an upper loading pad (101), a lower loading pad (102), a front loading pad (103), a rear loading pad (104), a left loading pad (105), a right loading pad (106), and a loading rod (107) for loading each loading pad. The upper loading pad (101) has a hollow cavity (6) on the end face that contacts the dry hot rock sample (5), and an insulating sealing gasket (7) surrounding the hollow cavity (6) is placed between the upper loading pad (101) and the upper surface of the dry hot rock sample (5). The electrode (301) of the high voltage pulse mechanism (3) is disposed in the hollow cavity (6), and the water pressure fracturing mechanism (4) directly injects fracturing water into the hollow cavity (6); During the experiment, by adjusting the loading force of the true triaxial stress loading mechanism (1), the three-dimensional stress field of the dry hot rock sample (5) was made to match the actual geostress state of the obtained rock sample. At the same time, the temperature of the dry hot rock sample (5) was made to match the actual temperature of the obtained rock sample by the heating mechanism (2). By changing the pulse discharge parameters and the hydraulic fracturing parameters, the hydraulic fracturing depth of the dry hot rock sample (5) under different parameter states was obtained. All parameters and their corresponding hydraulic fracturing depth data were used as sample data and trained using machine learning algorithms to construct a hydraulic fracturing fracture depth prediction model. In actual production, the well group layout scheme is determined according to the depth and range of the hot dry rock reservoir. Hydraulic fracturing is carried out by injection wells and production wells facing each other. Before hydraulic fracturing, high-voltage electric pulses are applied to the well walls of injection wells and production wells through a high-voltage pulse device, so that directional fractures are generated on the surface of injection wells and production wells. Based on the pulse discharge parameters determined in the actual production process, the hydraulic fracturing parameters are obtained when the hydraulic fracturing depth is half the distance between the injection well and the production well using the constructed hydraulic fracturing depth prediction model. The obtained hydraulic fracturing parameters are then used to guide actual production.

2. The high-voltage electrical pulse combined with hydraulic fracturing method for dry hot rock according to claim 1, characterized in that: The heater of the heating mechanism (2) includes an upper heater (8) and a lower heater (9) that can work independently; The upper heater (8) is located around the upper part of the dry hot rock sample (5), and the lower heater (9) is located around the lower part of the dry hot rock sample (5).

3. The high-voltage electrical pulse combined with hydraulic fracturing method for hot dry rock according to claim 2, characterized in that: Each corner of the dry hot rock sample (5) is wrapped by an insulating heat-conducting box (13). The insulating heat-conducting box (13), together with the upper loading pad (101), lower loading pad (102), front loading pad (103), rear loading pad (104), left loading pad (105), and right loading pad (106), forms a loading chamber adapted to the dry hot rock sample (5).

4. The high-voltage electrical pulse combined with hydraulic fracturing method for hot dry rock according to any one of claims 1-3, characterized in that: The heating mechanism (2) is a heating furnace. Each of the loading pads is set outside the heating furnace and extends into the heating furnace. The loading pads are slidably connected to the furnace wall of the heating furnace.

5. The high-voltage electrical pulse combined with hydraulic fracturing method for hot dry rock according to any one of claims 1-3, characterized in that: The water pressure fracturing mechanism (4) includes a water tank (401), a water injection pipe (402), a water injection pump (403), and a pressure sensor (404). The upper loading pad (101) is provided with a water injection channel (14) that communicates with the bottom of the hollow cavity (6). One end of the water injection channel (14) is connected to the bottom of the hollow cavity (6). One end of the water injection pipe (402) is connected to the water injection channel (14), and the other end is connected to the water tank (401). The water injection pump (403) and the pressure sensor (404) are mounted on the water injection pipe (402).

6. The high-voltage electrical pulse combined with hydraulic fracturing method for dry hot rock according to claim 5, characterized in that: It also includes a liquid nitrogen cooling mechanism (15), which includes a liquid nitrogen source (151), a liquid nitrogen delivery pipe (152) and a liquid nitrogen delivery pump (153). The liquid nitrogen source (151) is connected to the water injection channel (14) through the liquid nitrogen delivery pipe (152), and the liquid nitrogen delivery pump (153) is installed on the liquid nitrogen delivery pipe (152).

7. The high-voltage electrical pulse combined with hydraulic fracturing method for dry hot rock according to claim 6, characterized in that: The water injection channel (14) is equipped with a control valve (16) that allows it to selectively connect to either the liquid nitrogen delivery pipe (152) or the water injection pipe (402).

8. The high-voltage electrical pulse combined with hydraulic fracturing method for dry hot rock according to claim 1, characterized in that: The pulse discharge parameters include discharge frequency, discharge voltage, and number of discharges, while the water pressure fracturing parameters include injection pressure and injection rate.

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