A liquid carbon dioxide phase-transition induced fracturing impact loading test device and method

Abstract

The application provides a liquid carbon dioxide phase change induced fracturing impact load test device and method, which comprises a gas explosion impact system, a temperature control system, a filling system, a data acquisition system and an assembly system. The liquid carbon dioxide phase change induced fracturing impact load test device provided by the application can simultaneously monitor the impact pressure and expansion pressure during the phase change induced fracturing of carbon dioxide through the gas explosion impact system, and has rich monitoring functions, high precision and safety and reliability, can improve the simulation degree of indoor model test on the field engineering condition, and provides higher reference value for the theoretical research of the liquid CO2 phase change induced fracturing technology.

Description

Technical Field

[0001] This application belongs to the field of exploration, soil and building testing technology, and more specifically, relates to a liquid carbon dioxide phase change-induced cracking impact load testing device and method. Background Technology

[0002] Liquid carbon dioxide phase change fracturing technology is a green and pollution-free blasting technique. It utilizes the high-pressure gas generated by the phase change of liquid CO2 to fracture rock. This phase change fracturing process is a physical explosion process without open flames or pollution, offering advantages such as higher safety than explosive blasting and less disturbance to nearby engineering structures. CO2 is an environmentally friendly and readily available chemical substance, and its extraction has high economic benefits and environmental sustainability, showing broad prospects for industrial applications. With the growth of global energy demand, liquid CO2 phase change fracturing technology has received widespread attention in energy and mineral extraction. Currently, theoretical research on liquid CO2 phase change fracturing technology lags behind engineering applications; therefore, it is necessary to clarify the impact load characteristics of the liquid carbon dioxide phase change fracturing process to promote the development of related theoretical research.

[0003] To describe the rock-breaking mechanism of liquid CO2 phase transformation fracturing, impact loading characteristics are commonly used as a quantitative descriptive method. Impact loading characteristics include the impact stress wave at the moment of fragmentation and the expansion pressure of the explosive gas. The impact stress wave is a crucial factor influencing the initial cracking of rock, while the wedging effect of the explosive gas promotes further crack propagation. Therefore, collecting data on the impact stress wave and expansion pressure during liquid CO2 phase transformation fracturing is essential. Traditional methods using the TNT equivalent method to describe the impact load during liquid CO2 phase transformation fracturing suffer from significant errors in calculating the explosive energy and are insufficient for analyzing the rock-breaking process under complex time-scale conditions. Therefore, more accurate and reliable research equipment and methods are urgently needed. Summary of the Invention

[0004] The purpose of this application is to provide a liquid carbon dioxide phase change-induced cracking impact load test device and method to solve the technical problem of large calculation errors in existing liquid CO2 phase change-induced cracking research devices and methods.

[0005] To achieve the above objectives, a first aspect of this application provides a liquid carbon dioxide phase change-induced cracking impact load testing apparatus, comprising:

[0006] A gas explosion impact system includes a phase change gas explosion module and an impact load module. The phase change gas explosion module includes a pressure vessel, a pneumatic valve, a gas explosion pipe, and a first clamp. The pneumatic valve is located at the outlet of the pressure vessel, and one end of the gas explosion pipe is connected to the pneumatic valve, while the other end is connected to the first clamp. The first clamp contains a rupture disc, and its outlet end has a gas explosion port. The impact load module includes an expansion vessel, an expansion vessel volume change control component, and an impact pressure measuring component. The expansion vessel has an interface communicating with the gas explosion port. The impact pressure measuring component includes a set of symmetrical impact sliders located near the gas explosion port. A first pressure sensor is provided on the impact sliders, and the first pressure sensor is used to detect the impact pressure of the rupture gas at the gas explosion port. A second pressure sensor is provided inside the expansion vessel, and the second pressure sensor is used to detect the expansion pressure inside the expansion vessel.

[0007] A temperature control system is used to control the temperature of carbon dioxide in the pressure vessel and the gas explosion tube;

[0008] A filling system for filling the pressure vessel with liquid carbon dioxide;

[0009] The data acquisition system acquires the pressure values ​​detected by the first pressure sensor and the second pressure sensor; and,

[0010] An assembly system for fixing and mounting the pressure vessel.

[0011] Furthermore, the impact pressure measuring assembly also includes at least two symmetrically arranged first rotating threaded rods; the impact slider includes an impact plate, a movable support, a movable slider, a second rotating threaded rod, and a slider base, wherein the impact plate, the movable support, and the slider base are hinged to each other, one end of the second rotating threaded rod is connected to the movable slider, and the movable slider slides with the rotation of the second rotating threaded rod and drives the impact plate to rotate around its hinge axis with the slider base; the expansion vessel is provided with a sliding track groove, and the impact slider can slide on the sliding track groove; one end of the first rotating threaded rod is connected to the slider base, and the slider base slides with the rotation of the first rotating threaded rod; the first pressure sensor is located at the central axis of the impact plate.

[0012] Furthermore, the assembly system includes a fixed support, two symmetrically arranged threaded rods, two layers of lifting brackets, and two sliding sleeves. Each layer of the lifting bracket includes a fixed plate, two nuts, and two inclined brackets. The inclined brackets are connected to the sleeves and the fixed plate by a first bolt assembly. The lifting brackets and the sliding sleeves are adjusted in position by the nuts. The upper layer of the lifting bracket is connected to the upper end of the pressure vessel by a linear bearing. The linear bearing can control the pressure vessel to move up and down relative to the upper layer of the lifting bracket.

[0013] Furthermore, the lower end of the pressure vessel passes through the central hole of the lower lifting bracket, and a weighing sensor is arranged around the central hole of the lower lifting bracket. The weighing sensor is in contact with the pressure vessel and is used to weigh the mass of carbon dioxide filled in the pressure vessel. The data acquisition system also collects the weight value of the weighing sensor.

[0014] Furthermore, the expansion vessel volume change control assembly includes at least two hollow hydraulic jacks symmetrically arranged on the expansion vessel and a hollow piston connected to one end of the hollow hydraulic jacks. The second pressure sensor is located at the central axis of the hollow hydraulic jacks and the hollow pistons. The hollow hydraulic jacks are fixed to the expansion vessel by a second bolt assembly. The hollow hydraulic jacks are connected to the drive hydraulic control box via hydraulic oil pipes.

[0015] Furthermore, a fixed support is also connected to the expansion vessel.

[0016] Furthermore, the expansion vessel is also provided with a second clamp, one end of which is connected to the inner cavity of the expansion vessel, and a rupture disc is provided inside the second clamp.

[0017] Furthermore, the temperature control system includes a ceramic heating core, an insulation layer, a hot runner spring heating coil, a heating core temperature control box, and a heating coil temperature control box. The ceramic heating core is located inside the pressure vessel. The hot runner spring heating coil is in direct contact with the gas explosion tube by winding. The heating core temperature control box is used to control the temperature of the ceramic heating core, and the heating coil temperature control box is used to control the temperature of the hot runner spring heating coil.

[0018] Furthermore, the filling system includes a nitrogen cylinder, a carbon dioxide cylinder, an air compressor, a booster pump, a high-pressure carbon dioxide cylinder, a three-way valve, a three-way valve, a safety valve, a solenoid valve, a solenoid valve switch, a high-pressure air supply pipe, and a pneumatic pipe. The two inlets of the three-way valve are connected to the nitrogen cylinder and the high-pressure carbon dioxide cylinder respectively through the high-pressure air supply pipe. The outlet of the three-way valve is connected to the solenoid valve through the high-pressure air supply pipe. The three-way valve is connected to the solenoid valve, the safety valve, and the pressure vessel respectively. The air compressor drives the booster pump and the actuator through the pneumatic pipe.

[0019] Furthermore, the data acquisition system includes a data acquisition instrument and a data processing terminal, wherein the data acquisition instrument is connected to the first pressure sensor, the second pressure sensor, and the data processing terminal.

[0020] A second aspect of this application provides a method for conducting liquid carbon dioxide phase change-induced fracturing impact load tests using the liquid carbon dioxide phase change-induced fracturing impact load testing apparatus described in any one of the above claims, comprising the following steps:

[0021] S1: Install the phase change gas explosion module, assemble the gas explosion tube and the first clamp onto the pneumatic valve, open the pneumatic valve to discharge the air in the pressure vessel and the gas explosion tube, close the pneumatic valve and install the rupture disc and the gas explosion port;

[0022] S2: Adjust the relative position between the gas explosion port and the impact slider to initialize the data acquisition system;

[0023] S3: Open the filling system to fill the pressure vessel with liquid carbon dioxide;

[0024] S4: Open the pneumatic valve and use the temperature control system to cause the liquid carbon dioxide in the pressure vessel and the gas explosion tube to expand and undergo phase change due to heat. When the pressure in the gas explosion tube exceeds the bearing capacity of the rupture disc, the supercritical carbon dioxide is rapidly released to achieve the gas explosion effect.

[0025] S5: Collect the impact pressure data on the impact slider through the data acquisition system, disassemble the gas explosion port, replace it with a new rupture disc and install the rupture disc of the expansion vessel, and connect the interface between the first clamp and the expansion vessel.

[0026] S6: Repeat the S3 and S4 processes to collect the expansion pressure data inside the expansion vessel through the data acquisition system.

[0027] Compared with the prior art, this application has the following technical effects:

[0028] The liquid carbon dioxide phase change cracking impact load test device of this application can simultaneously monitor the impact pressure and expansion pressure during carbon dioxide phase change cracking through the gas explosion impact system. It has rich monitoring functions, high accuracy and safety and reliability, which can improve the simulation degree of indoor model test on the field engineering conditions and provide higher reference value for the theoretical research of liquid CO2 phase change cracking technology.

[0029] Compared to traditional fracturing devices that are detonated by connecting an activator to an initiator, the liquid carbon dioxide phase change fracturing impact load testing device of this application has a simpler structure and is safer to use.

[0030] The method of conducting liquid carbon dioxide phase change cracking impact load test using the liquid carbon dioxide phase change cracking impact load test device of this application can effectively test the impact pressure and expansion pressure during the carbon dioxide phase change cracking process. It can clarify the time history curves of the impact pressure of the impact slider and the expansion pressure of the expansion vessel under different gas explosion parameters, and thus obtain the structural characteristics of the impact load during the carbon dioxide phase change cracking process. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the overall structure of a liquid carbon dioxide phase change-induced cracking impact load testing device provided in an embodiment of this application;

[0033] Figure 2 for Figure 1 A top view of the lower and middle level lifting support structure;

[0034] Figure 3 for Figure 1 A top view of the upper and middle level lifting support structure;

[0035] Figure 4 for Figure 1 Enlarged schematic diagram of a portion of the connection between the medium-pressure vessel and the linear bearing;

[0036] Figure 5 for Figure 1 A magnified schematic diagram of a portion of the structure at the installation location of the weighing sensor;

[0037] Figure 6 for Figure 1 Structural schematic diagram of the medium impact load module;

[0038] Figure 7 for Figure 6 A top-view structural diagram;

[0039] Figure 8 for Figure 6 A schematic diagram of the structure of the impact slider.

[0040] The following are the labeling elements in the figure:

[0041] 1. Fixed support, 2. Threaded rod, 3. Lifting bracket, 4. Sliding sleeve, 5. Fixed plate, 6. Nut, 7. Inclined bracket, 8. First bolt assembly, 9. Weighing sensor, 10. Linear bearing, 11. Pressure vessel, 12. Pneumatic valve, 13. Actuator, 14. Air explosion pipe, 15. First clamp, 16. Rupture disc, 17. Air explosion port, 18. Expansion vessel, 19. First rotating threaded rod, 20. Impact slider, 21. Hollow hydraulic jack, 22. Hollow piston, 23. Second clamp, 24. Hydraulic oil pipe, 25. Fixed support, 26. Drive hydraulic control box, 27. Sliding track groove, 28. Second bolt assembly, 29. 30. Interface; 31. Ceramic heating core; 32. Insulation layer; 33. Hot runner spring heating coil; 34. Heating core temperature control box; 35. Heating coil temperature control box; 36. Nitrogen cylinder; 37. Carbon dioxide cylinder; 38. Air compressor; 39. Booster pump; 40. High-pressure carbon dioxide cylinder; 41. Three-way valve; 42. Three-way valve; 43. Solenoid valve; 44. Solenoid valve switch; 45. High-pressure air guide pipe; 46. Pneumatic pipe; 47. Pressure sensor; 48. Data acquisition instrument; 49. Data processing terminal; 201. Impact plate; 202. Moving bracket; 203. Moving slider; 204. Second rotating threaded rod; 205. Slider base. Detailed Implementation

[0042] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0043] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0044] It should be understood that the terms "length", "upper", "lower", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not 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 application.

[0045] Furthermore, the terms "first," "second," "third," "fourth," and "fifth" 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. Therefore, a feature defined with "first," "second," "third," "fourth," or "fifth" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0046] Please refer to the following: Figures 1 to 8 The present application will now describe a liquid carbon dioxide phase change-induced cracking impact load test device and method provided in the embodiments of this application.

[0047] In one embodiment of this application, a liquid carbon dioxide phase change-induced cracking impact load testing device includes a gas explosion impact system, a temperature control system, a filling system, a data acquisition system, and an assembly system.

[0048] The gas explosion impact system includes a phase change gas explosion module and an impact load module. The phase change gas explosion module includes a pressure vessel 11, a pneumatic valve 12, a gas explosion pipe 14, and a first clamp 15. The pneumatic valve 12 is located at the outlet of the pressure vessel 11, and one end of the gas explosion pipe 14 is connected to the pneumatic valve 12, while the other end is connected to the first clamp 15. The first clamp 15 contains a rupture disc 16, and its outlet end is provided with a gas explosion port 17. The impact load module includes an expansion vessel 18, an expansion vessel volume change control component, and an impact pressure measuring component. The expansion vessel 18 is provided with an interface 29 that communicates with the gas explosion port 17. The impact pressure measuring component includes a set of symmetrical impact sliders 20 located near the gas explosion port 17. The impact sliders 20 are provided with a first pressure sensor, which is used to detect the impact pressure of the rupture gas at the gas explosion port 17. The expansion vessel 18 contains a second pressure sensor, which is used to detect the expansion pressure inside the expansion vessel 18.

[0049] The temperature control system controls the temperature of carbon dioxide inside the pressure vessel 11 and the gas explosion tube 14. The filling system fills the pressure vessel 11 with liquid carbon dioxide. The data acquisition system acquires the pressure values ​​detected by the first and second pressure sensors. The assembly system securely mounts the pressure vessel 11.

[0050] like Figure 1 As shown, in this embodiment of the application, the pressure vessel 11 and the gas explosion tube 14 are indirectly in contact through the pneumatic valve 12, and the gas explosion tube 14 and the gas explosion port 17 are indirectly in contact through the first clamp 15.

[0051] The pneumatic valve 12 in this embodiment can be a pneumatic ball valve. In the accompanying drawings, both the first pressure sensor and the second pressure sensor are labeled as pressure sensor 47.

[0052] The liquid carbon dioxide phase change cracking impact load test device of this application embodiment can simultaneously monitor the impact pressure and expansion pressure during carbon dioxide phase change cracking through the gas explosion impact system. It has rich monitoring functions, high accuracy and safety and reliability, which can improve the simulation degree of indoor model test on the field engineering conditions and provide higher reference value for the theoretical research of liquid CO2 phase change cracking technology.

[0053] Compared to traditional fracturing devices that are detonated by connecting an activator to an initiator, the liquid carbon dioxide phase change fracturing impact load test device of this application embodiment has a simpler structure and is safer to use.

[0054] Furthermore, the impact pressure measuring component of this application embodiment also includes at least two symmetrically arranged first rotating threaded rods 19; the impact slider 20 includes an impact plate 201, a movable support 202, a movable slider 203, a second rotating threaded rod 204, and a slider base 205, the impact plate 201, the movable support 202, and the slider base 205 are hinged to each other, one end of the second rotating threaded rod 204 is connected to the movable slider 203, the movable slider 203 slides with the rotation of the second rotating threaded rod 204 and drives the impact plate 201 to rotate around its hinge axis with the slider base 205; the expansion vessel 18 is provided with a sliding track groove 27, and the impact slider 20 can slide on the sliding track groove 27; one end of the first rotating threaded rod 19 is connected to the slider base 205, and the slider base 205 slides with the rotation of the first rotating threaded rod 19; the first pressure sensor is located at the central axis of the impact plate 201.

[0055] like Figure 1 , Figure 6 , Figure 7 , Figure 8 As shown, the impact pressure measuring assembly implemented in this application includes four first rotating threaded rods 19 and two impact sliders 20. Each impact slider 20 includes an impact plate 201, a movable bracket 202, a movable slider 203, a second rotating threaded rod 204, and a slider base 205. The impact plate 201, the movable bracket 202, and the slider base 205 are assembled by hinges. The second rotating threaded rod 204 passes through the movable slider 203, and the movable slider 203 slides with the rotation of the second rotating threaded rod 204, causing the impact plate 201 to rotate around... The hinge axis of the impact plate 201 rotates with the slider base 205, thereby changing the angle between the plate surface of the impact plate 201 and the central axis of the gas explosion port 17; the upper part of the expansion vessel 18 has a sliding track groove 27, and two first rotating threaded rods 19 pass through the slider base 205. The bottom of the impact slider 20 is provided with a T-shaped groove, which is connected to the expansion vessel 18 through the sliding track groove 27. The impact slider 20 moves with the rotation of the first rotating threaded rods 19, thereby changing the horizontal distance between the plate surface of the impact plate 201 and the central axis of the gas explosion port 17.

[0056] When measuring impact pressure, the gas explosion port 17 is aligned with the pressure sensor 47 on the impact plate 201. The relative horizontal distance between the gas explosion port 17 and the surface of the impact plate 201 is adjusted by rotating the first rotating threaded rod 19 to move the slider base 205. The second rotating threaded rod 204 is then rotated to move the slider 203, causing the impact plate 201 to rotate around its hinge axis with the slider base 205, thus adjusting the angle between the surface of the impact plate 201 and the central axis of the gas explosion port 17. The impact pressure during the gas explosion is then measured by the pressure sensor 47 on the impact plate 201. This method fully considers the changes in impact pressure measured when the relative position of the impact plate 201 and the gas explosion port 17 changes.

[0057] Furthermore, the assembly system of this application embodiment includes a fixed support 1, two symmetrically arranged threaded rods 2, two layers of lifting brackets 3 and two sliding sleeves 4. Each layer of lifting bracket 3 includes a fixed plate 5, two nuts 6 and two inclined brackets 7. The inclined brackets 7 are connected to the sleeves 4 and the fixed plate 5 through a first bolt assembly 8. The lifting brackets 3 and the sliding sleeves 4 are adjusted in position using nuts 6. The upper layer of lifting bracket 3 is connected to the upper end of the pressure vessel 11 through a linear bearing 10. The linear bearing 10 can control the pressure vessel 11 to move up and down relative to the upper layer of lifting bracket 3 within a certain range.

[0058] Furthermore, in this embodiment of the application, the lower end of the pressure vessel 11 passes through the central hole of the lower lifting bracket 3. Four weighing sensors 9 are arranged around the central hole of the lower lifting bracket 3. The weighing sensors 9 are in indirect contact with the pressure vessel 11 and are used to weigh the mass of carbon dioxide filled in the pressure vessel 11. They also provide support for the pressure vessel 11. The data acquisition system also collects the weight value of the weighing sensors 9.

[0059] Furthermore, the expansion vessel volume change control component of this application embodiment includes at least two hollow hydraulic jacks 21 symmetrically arranged on the expansion vessel 18 and a hollow piston 22 connected to one end of the hollow hydraulic jacks 21. A second pressure sensor is located at the central axis of the hollow hydraulic jacks 21 and the hollow piston 22. The hollow hydraulic jacks 21 are fixed to the expansion vessel 18 by a second bolt assembly 28. The hollow hydraulic jacks 21 are connected to the drive hydraulic control box 26 through a hydraulic oil pipe 24.

[0060] like Figure 1 , Figure 6As shown, the expansion vessel volume change control component of this application embodiment includes four hollow hydraulic jacks 21 and four hollow pistons 22. The four hollow hydraulic jacks 21 are fixed to the expansion vessel 18 by the second bolt assembly 28. The hollow jacks 21 are driven to extend and retract by the driving hydraulic control box 26 to control the position of the hollow pistons 22. The pressure sensors 47 on the four hollow pistons 22 can measure the expansion pressure at different positions in the expansion vessel 18 during gas explosion. The change in the experimental position of the hollow pistons 22 is the change in the volume of the cavity in the expansion vessel 18.

[0061] Furthermore, in this embodiment of the application, two fixed supports 25 are also connected to the lower side of the expansion vessel 18 for supporting the expansion vessel 18.

[0062] Furthermore, the expansion vessel 18 in this embodiment is also provided with a second clamp 23, one end of which is connected to the inner cavity of the expansion vessel 18, and a rupture disc is provided inside the second clamp 23. The expansion vessel 18 in this embodiment is provided with four second clamps 23, each connected to the expansion vessel 18 via a threaded structure, and each second clamp 23 contains a rupture disc. The pressure inside the expansion vessel 18 is controlled to reach its maximum value by the rupture disc within the second clamps 23. When the maximum value of the rupture disc within the expansion vessel 18 is reached, the rupture disc breaks, releasing carbon dioxide from the expansion vessel 18. The volume of the expansion vessel 18 is changed by adjusting the extension and retraction of the hollow hydraulic jack 21.

[0063] Furthermore, the temperature control system in this embodiment includes a ceramic heating core 30, an insulation layer 31, a hot runner spring heating coil 32, a heating core temperature control box 33, and a heating coil temperature control box 34. The ceramic heating core 30 is located inside the pressure vessel 11. The hot runner spring heating coil 32 is in direct contact with the gas explosion tube 14 through a winding method. The heating core temperature control box 33 is used to control the temperature of the ceramic heating core 30, and the heating coil temperature control box 34 is used to control the temperature of the hot runner spring heating coil 32. By using the ceramic heating core 30 and the hot runner spring heating coil 32 to control the heating phase change, liquid carbon dioxide phase change processes with different heating rates are achieved.

[0064] Furthermore, the filling system of this application embodiment includes a nitrogen cylinder 35, a carbon dioxide cylinder 36, an air compressor 37, a booster pump 38, a high-pressure carbon dioxide cylinder 39, a three-way valve 40, a three-way valve 41, a safety valve 42, a solenoid valve 43, a solenoid valve switch 44, a high-pressure air guide pipe 45, and a pneumatic pipe 46. The two inlets of the three-way valve 40 are connected to the nitrogen cylinder 35 and the high-pressure carbon dioxide cylinder 39 respectively through the high-pressure air guide pipe 45. The outlet of the three-way valve 40 is connected to the solenoid valve 43 through the high-pressure air guide pipe 45. The three-way valve 41 is connected to the solenoid valve 43, the safety valve 42, and the pressure vessel 11 respectively. The air compressor 37 drives the booster pump 38 and the actuator 13 through the pneumatic pipe 46. The actuator 13 controls the opening and closing of the pneumatic valve 12, and the solenoid valve switch 44 controls the operation of the actuator 13.

[0065] In use, first fill the pressure vessel 11 with nitrogen through nitrogen cylinder 35, and at the same time open the pneumatic valve 12 to release the air from the pressure vessel 11 and the gas explosion pipe 14. Then fill the pressure vessel 11 with liquid carbon dioxide through high-pressure carbon dioxide cylinder 39.

[0066] Furthermore, the data acquisition system of this application embodiment includes a data acquisition instrument 48 and a data processing terminal 49, wherein the data acquisition instrument 48 is connected to a first pressure sensor, a second pressure sensor and the data processing terminal 49.

[0067] A second aspect of this application provides a method for conducting liquid carbon dioxide phase change-induced fracturing impact load tests using the liquid carbon dioxide phase change-induced fracturing impact load testing apparatus described above, comprising the following steps:

[0068] S1: Install the phase change gas explosion module, assemble the gas explosion tube 14 and the first clamp 15 onto the pneumatic valve 12, open the pneumatic valve 12 to discharge the air in the pressure vessel 11 and the gas explosion tube 14, close the pneumatic valve 12 and install the rupture disc 16 and the gas explosion port 17; specifically, the air in the pressure vessel 11 and the gas explosion tube 14 can be discharged by connecting the nitrogen cylinder 35;

[0069] S2: Adjust the relative position between the air vent 17 and the impact slider 20 to initialize the data acquisition system; specifically, the relative position between the air vent 17 and the impact plate 201 can be adjusted to initialize the weighing sensor 9 and the data acquisition system.

[0070] S3: Open the filling system to fill the pressure vessel 11 with liquid carbon dioxide; specifically, open the high-pressure carbon dioxide cylinder 39 to fill with liquid carbon dioxide, and monitor the weighing sensor 9 in real time. After filling a certain mass, fix the upper lifting bracket 3 and the pressure vessel 11.

[0071] S4: Open the pneumatic valve 12, and use the temperature control system to cause the liquid carbon dioxide in the pressure vessel 11 and the gas explosion tube 14 to expand and undergo a phase change due to heat. When the pressure in the gas explosion tube 14 exceeds the bearing capacity of the rupture disc 16, the supercritical carbon dioxide is rapidly released to achieve the gas explosion effect. Specifically, the liquid carbon dioxide in the pressure vessel 11 and the gas explosion tube 14 can be heated by heating the ceramic heating core 30 and the hot runner spring heating coil 32.

[0072] S5: Collect impact pressure data on the impact slider 20 (impact plate 201) through the data acquisition system, that is, collect data through the data acquisition instrument 48 and automatically transmit the data to the data processing terminal 49, disassemble the gas explosion port 17, replace it with a new rupture disc 16 and install the rupture disc of the expansion vessel 18, and connect the interface 29 of the first clamp 15 and the expansion vessel 18.

[0073] S6: Repeat the S3 and S4 processes, collect the expansion pressure data in the expansion vessel 18 through the data acquisition system and automatically transmit the data to the data processing terminal 49.

[0074] In step S1 above, the dimensions of the gas explosion tube 14, the rupture disc 16, and the gas explosion port 17 can all be changed.

[0075] In step S2 above, the vertical distance between the impact plate 201 and the gas explosion port 17 is adjusted by the lifting bracket 3 and the hollow hydraulic jack 21 located at the bottom of the expansion vessel 18. The horizontal distance or angle between the impact plate 201 and the gas explosion port 17 can be adjusted by rotating the first rotating threaded rod 19 or the second rotating threaded rod 204.

[0076] In step S3 above, the mass of carbon dioxide filled is measured by weighing sensor 9.

[0077] In step S4 above, the heating rate of liquid carbon dioxide is controlled by adjusting the temperature of the ceramic heating core 30 and the hot runner spring heating coil 32.

[0078] In step S5 above, the pressure of expansion vessel 18 is controlled to reach the maximum value by the rupture disc inside the second clamp 23 of expansion vessel 18. When the maximum value of the rupture disc inside the expansion vessel is reached, the rupture disc breaks and the carbon dioxide inside the expansion vessel 18 is released. The volume change of expansion vessel 18 is achieved by adjusting the extension and retraction of the hollow hydraulic jack 21.

[0079] It should be noted that when measuring the expansion pressure, the gas explosion port 17 is disassembled, and the first clamp 15 and the rupture disc 16 are connected to the interface 29 on the expansion vessel 18 through a threaded structure. Then, the extension of the four hollow hydraulic jacks 21 is controlled by the drive hydraulic control box 26, so that the four hollow pistons 22 are in the experimental position, and the pressure sensor 47 is fixed in the middle of the hollow piston 22. At the same time, the predetermined rupture disc is installed in the four second clamps 23, and then the experiment is carried out. The pressure sensor 47 on the four hollow pistons 22 can measure the expansion pressure at different positions in the expansion vessel 18 during the gas explosion.

[0080] The sample method of this application fully considers the replaceability of the gas explosion tube 14, the rupture disc 16 and the gas explosion port 17, and makes full use of the flexibility of the impact slider 20 and the expansion vessel 18. By using the spatial distribution characteristics of the impact pressure and the loading and attenuation law of the expansion pressure, the impact load characteristics of the liquid carbon dioxide phase change cracking process are inverted.

[0081] The sample method of this application fully considers dimensional parameters such as carbon dioxide filling amount, inner diameter of gas explosion tube 14, thickness of rupture disc 16 and diameter of gas explosion port 17, and also considers changes in parameters such as heating rate, relative position of impact plate 201 and gas explosion port 17 and volume of expansion vessel 18, to analyze the distribution of impact stress wave and the loading and attenuation law of impact load.

[0082] The sample apparatus and method of this application can effectively test the impact pressure and expansion pressure during the carbon dioxide phase change fracturing process. The obtained impact pressure on the impact plate 201 helps to explore the spatiotemporal distribution characteristics of the impact stress wave under free field conditions during the carbon dioxide phase change fracturing process. The obtained expansion pressure inside the expansion vessel 18 helps to explore the pressure loading and attenuation laws of the phase change expansion process of supercritical carbon dioxide in a confined space and the process of releasing it into gaseous carbon dioxide. By comparing the impact pressure data of the impact plate 201 and the expansion pressure data of the expansion vessel 18 collected by controlling the heating rate and filling mass of liquid carbon dioxide in this experimental apparatus, it is helpful to determine the equation of state of the explosive gas under different initial conditions of carbon dioxide. By changing parameters such as carbon dioxide filling amount, heating rate, size of gas explosion tube 14, thickness of rupture disc 16, nozzle diameter of gas explosion port 17, position of impact slider 20, volume of expansion vessel 18, and thickness of rupture disc in expansion vessel 18 in each test, the impact pressure time history curves of impact plate 201 and expansion pressure of expansion vessel 18 under different gas explosion parameters can be clarified using the carbon dioxide phase change fracturing impact load test device and method provided in this application. This allows for the determination of the impact pressure time history curves of impact plate 201 and expansion vessel 18 under different gas explosion parameters, thereby obtaining the structural characteristics of impact load in the carbon dioxide phase change fracturing process. This can improve the simulation degree of indoor model test on field engineering conditions and provide higher reference value for theoretical research on liquid CO2 phase change fracturing technology.

[0083] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A liquid carbon dioxide phase change-induced cracking impact load testing device, characterized in that, include: A gas explosion impact system includes a phase change gas explosion module and an impact load module. The phase change gas explosion module includes a pressure vessel, a pneumatic valve, a gas explosion pipe, and a first clamp. The pneumatic valve is located at the outlet of the pressure vessel, and one end of the gas explosion pipe is connected to the pneumatic valve, while the other end is connected to the first clamp. The first clamp contains a rupture disc, and its outlet end has a gas explosion port. The impact load module includes an expansion vessel, an expansion vessel volume change control component, and an impact pressure measuring component. The expansion vessel has an interface communicating with the gas explosion port. The impact pressure measuring component includes a set of symmetrical impact sliders located near the gas explosion port. A first pressure sensor is provided on the impact sliders, and the first pressure sensor is used to detect the impact pressure of the rupture gas at the gas explosion port. A second pressure sensor is provided inside the expansion vessel, and the second pressure sensor is used to detect the expansion pressure inside the expansion vessel. A temperature control system is used to control the temperature of carbon dioxide in the pressure vessel and the gas explosion tube; A filling system for filling the pressure vessel with liquid carbon dioxide; The data acquisition system acquires the pressure values ​​detected by the first pressure sensor and the second pressure sensor; and, Assembly system for fixing and mounting the pressure vessel; The impact pressure measuring assembly further includes at least two symmetrically arranged first rotating threaded rods; the impact slider includes an impact plate, a movable support, a movable slider, a second rotating threaded rod, and a slider base, wherein the impact plate, the movable support, and the slider base are hinged to each other; one end of the second rotating threaded rod is connected to the movable slider, and the movable slider slides with the rotation of the second rotating threaded rod, thereby driving the impact plate to rotate about its hinge axis with the slider base; the expansion vessel is provided with a sliding track groove, and the impact slider can slide on the sliding track groove; one end of the first rotating threaded rod is connected to the slider base, and the slider base slides with the rotation of the first rotating threaded rod; the first pressure sensor is located at the central axis of the impact plate; The expansion vessel volume change control assembly includes at least two hollow hydraulic jacks symmetrically arranged on the expansion vessel and a hollow piston connected to one end of each hollow hydraulic jack. The second pressure sensor is located at the central axis of the hollow hydraulic jack and the hollow piston. The hollow hydraulic jacks are fixed to the expansion vessel by a second bolt assembly. The hollow hydraulic jacks are connected to the drive hydraulic control box via hydraulic oil pipes. The expansion vessel is also provided with a second clamp, one end of which is connected to the inner cavity of the expansion vessel, and a rupture disc is provided inside the second clamp.

2. The liquid carbon dioxide phase change-induced cracking impact load testing device as described in claim 1, characterized in that, The assembly system includes a fixed support, two symmetrically arranged threaded rods, two layers of lifting brackets, and two sliding sleeves. Each layer of the lifting bracket includes a fixed plate, two nuts, and two inclined brackets. The inclined brackets are connected to the sleeves and the fixed plate by a first bolt assembly. The lifting brackets and the sliding sleeves are adjusted in position by the nuts. The upper layer of the lifting bracket is connected to the upper end of the pressure vessel by a linear bearing. The linear bearing can control the pressure vessel to move up and down relative to the upper layer of the lifting bracket.

3. The liquid carbon dioxide phase change-induced cracking impact load test device as described in claim 2, characterized in that, The lower end of the pressure vessel passes through the central hole of the lower lifting bracket. A weighing sensor is arranged around the central hole of the lower lifting bracket. The weighing sensor is in contact with the pressure vessel and is used to weigh the mass of carbon dioxide filled in the pressure vessel. The data acquisition system also collects the weight value of the weighing sensor.

4. The liquid carbon dioxide phase change-induced cracking impact load testing device as described in claim 1, characterized in that, The expansion vessel is also connected to a fixed support.

5. The liquid carbon dioxide phase change-induced cracking impact load testing device as described in claim 1, characterized in that, The temperature control system includes a ceramic heating core, an insulation layer, a hot runner spring heating coil, a heating core temperature control box, and a heating coil temperature control box. The ceramic heating core is located inside the pressure vessel. The hot runner spring heating coil is in direct contact with the gas explosion tube by winding. The heating core temperature control box is used to control the temperature of the ceramic heating core, and the heating coil temperature control box is used to control the temperature of the hot runner spring heating coil.

6. The liquid carbon dioxide phase change-induced cracking impact load testing device as described in claim 1, characterized in that, The filling system includes a nitrogen cylinder, a carbon dioxide cylinder, an air compressor, a booster pump, a high-pressure carbon dioxide cylinder, a three-way valve, a three-way valve, a safety valve, a solenoid valve, a solenoid valve switch, a high-pressure gas delivery pipe, and a pneumatic hose. The two inlets of the three-way valve are connected to the nitrogen cylinder and the high-pressure carbon dioxide cylinder respectively via the high-pressure gas delivery pipe. The outlet of the three-way valve is connected to the solenoid valve via the high-pressure gas delivery pipe. The three-way valve is connected to the solenoid valve, the safety valve, and the pressure vessel. The air compressor drives the booster pump and the actuator via the pneumatic hose; and / or, The data acquisition system includes a data acquisition instrument and a data processing terminal. The data acquisition instrument is connected to the first pressure sensor, the second pressure sensor, and the data processing terminal.

7. A method for conducting liquid carbon dioxide phase change-induced cracking impact load tests using the liquid carbon dioxide phase change-induced cracking impact load testing apparatus according to any one of claims 1-6, characterized in that, Includes the following steps: S1: Install the phase change gas explosion module, assemble the gas explosion tube and the first clamp onto the pneumatic valve, open the pneumatic valve to discharge the air in the pressure vessel and the gas explosion tube, close the pneumatic valve and install the rupture disc and the gas explosion port; S2: Adjust the relative position between the gas explosion port and the impact slider to initialize the data acquisition system; S3: Open the filling system to fill the pressure vessel with liquid carbon dioxide; S4: Open the pneumatic valve and use the temperature control system to cause the liquid carbon dioxide in the pressure vessel and the gas explosion tube to expand and undergo phase change due to heat. When the pressure in the gas explosion tube exceeds the bearing capacity of the rupture disc, the supercritical carbon dioxide is rapidly released to achieve the gas explosion effect. S5: Collect the impact pressure data on the impact slider through the data acquisition system, disassemble the gas explosion port, replace it with a new rupture disc and install the rupture disc of the expansion vessel, and connect the interface between the first clamp and the expansion vessel. S6: Repeat the S3 and S4 processes to collect the expansion pressure data inside the expansion vessel through the data acquisition system.

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