A supercritical CO2 fracturing test device

Abstract

The present invention discloses a supercritical CO2 fracturing test device, comprising a fracturing tube, a rock and a protective steel cylinder surrounding the rock, a data acquisition component being fixed on the rock; the fracturing tube extends into a fracturing hole inside the rock; a clamp is provided on the outer sleeve of the fracturing tube, and the clamp is connected to the protective steel cylinder through at least two iron chains. A tightener is provided on each iron chain, and the tightener comprises a box body and a brake assembly fixed inside the box body for limiting the rotation of a driving gear, a motor is fixedly connected inside the box body, and the output shaft of the motor is fixedly connected to the central axis of the driving gear; winding gears are meshed on both sides of the driving gear, and the winding gears and a winch for winding the iron chain are fixed on the same rotating shaft, and the rotating shaft is rotatably connected to the box body through a bearing. The fracturing tube can be limited by the tightener, the clamp and the iron chain to prevent it from being displaced by force and affecting the test results or causing safety hazards due to the flying tube.

Description

Technical Field

[0001] The invention relates to the technical field of rock fracturing, and in particular to a supercritical CO2 fracturing test device. Background Art

[0002] Supercritical CO2 phase change rock fracturing is a physical rock breaking technology. Its principle is: after the fracturing tube is filled with liquid CO2, heat is quickly released by igniting the activator. After the liquid CO2 absorbs heat, it changes phase to form supercritical CO2, and its volume expands up to 600 times, causing the pressure inside the fracturing tube to rise rapidly. Finally, by destroying the bottom shear sheet, a supercritical CO2 jet is released to impact the borehole rock wall, causing rock damage. The energy released by the fracturing tube is much smaller than that of explosives, but it can still provide a large amount of energy to destroy the rock. In the process of rock breaking, the fracturing tube is placed in the borehole. When the energy in the tube is released, a huge recoil force will be generated in the hole. Inadequate protective measures will cause the fracturing tube to fly out, affecting the test results and even causing safety hazards. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention provides a supercritical CO2 fracturing test device, which solves the problem that the fracturing tube is easy to fly away during the test, affecting the test results and even causing safety hazards.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is:

[0005] A supercritical CO2 fracturing test device is provided, which comprises a fracturing tube and a protective steel cylinder surrounding a rock, a data acquisition component is fixed on the rock; the fracturing tube extends into a fracturing hole inside the rock; a clamp is provided on the outer sleeve of the fracturing tube, and the clamp is connected to the protective steel cylinder through at least two iron chains.

[0006] A tensioner is provided on each iron chain, and the tensioner includes a box body and a brake assembly fixed inside the box body for limiting the rotation of the driving gear. A motor is fixedly connected to the inside of the box body, and the output shaft of the motor is fixedly connected to the central axis of the driving gear; winding gears are meshed on both sides of the driving gear, and the winding gears and the winch for winding the iron chain are fixed on the same rotating shaft, and the rotating shaft is rotatably connected to the box body through a bearing; the motor, brake assembly, data acquisition assembly and clamp are all electrically connected to the control module.

[0007] The beneficial effects of the present invention are as follows: the motor can be turned on by the control module, thereby driving the driving gear and the winding gear to rotate and tightening the iron chain to reach a tightening state with a preset tension value, and then the control module controls the brake assembly to brake, thereby preventing the winding gear and the driving gear from spinning back after the iron chain is stressed. The tightened iron chain can tighten the fracturing tube, thereby preventing the fracturing tube from being displaced by force during rock breaking, thereby affecting the test results or causing safety hazards caused by the flying tube.

[0008] Furthermore, the brake assembly includes a first oil cylinder fixedly connected to the inner wall of the box body, the end of the telescopic rod of the first oil cylinder is fixedly connected to an arc-shaped brake plate, the brake plate is provided with an arc-shaped cavity inside, a brake sprocket disc slidably connected to the cavity wall is installed in the cavity, the meshing teeth of the brake sprocket disc extend from the opening of the cavity, and when the telescopic rod is extended to the limit position, the meshing teeth of the brake sprocket disc mesh with the driving gear. Buffer assemblies are tightly connected to both ends of the brake sprocket disc, and both buffer assemblies abut against the side walls of the cavity.

[0009] The beneficial effect of the above technical solution is that when in use, the first oil cylinder controls the extension and retraction of the telescopic rod to enable the brake plate to move up and down, so that the brake sprocket disc engages or disengages with the driving gear, and when the two are engaged, the driving gear can be prevented from rotating.

[0010] Furthermore, the buffer component is a high-strength spring, and the elastic modulus of the spring is:

[0011]

[0012] in, is the shear plate thickness of the cracked pipe; is the shear piece clamping diameter; is the shear strength of the shear sheet; is the ratio of pi; r is the radius of the fracture tube; R 1 is the radius of the capstan; n is the number of chains; R 3 is the radius of the driving gear; is the deformation of the spring; is the angle between the iron chain and the cracking tube; cos(·) is the cosine function.

[0013] Furthermore, the first oil cylinder is electrically connected to the control module, and a torque sensor for transmitting the collected torque signal to the control module is arranged on the central axis of the driving gear. When , the control module starts the first oil cylinder;

[0014] in, M The torque data collected by the torque sensor; T is the preset tension value of the chain; R 2 is the radius of the rotation axis.

[0015] Through the torque sensor, the limiting tension on the chain that prevents the fracturing tube from flying out can be monitored after the fracturing tube releases energy.

[0016] Furthermore, the clamp includes a sleeve-shaped second oil cylinder and at least two pistons arranged in a ring along the inner wall curved surface of the second oil cylinder, and the end of the piston is fixedly connected with an arc-shaped rubber pad; connecting plates equal to the number of iron chains are fixedly connected in a ring along the outer wall curved surface of the second oil cylinder, one end of the iron chain is fixed on the connecting plate, and the other end is fixed on the protective steel cylinder; the outer wall of the second oil cylinder is provided with a medium inlet and a medium outlet connected to the internal cavity of the second oil cylinder; the medium inlet is connected to an external third oil cylinder.

[0017] The beneficial effect of the above technical solution is: hydraulic oil medium is injected into the second oil cylinder through the medium inlet, the hydraulic oil pushes the piston to move radially, and the rubber pad connected to the piston will also move radially and press the middle fracturing tube, forming a clamping effect on the fracturing tube to limit the upward movement of the fracturing tube.

[0018] Furthermore, the third oil cylinder is electrically connected to the control module, and the outer wall of the second oil cylinder is provided with a pressure sensor for transmitting the collected pressure signal to the control module. When the control module controls the third oil cylinder to stop delivering the medium to the second oil cylinder;

[0019] in, Q The radial pressure collected by the pressure sensor; μ is the friction coefficient between the rubber pad and the crack-causing tube; L is the height of the clamp; r is the radius of the fracture tube.

[0020] The beneficial effects of the above technical solution are: in order to prevent the impact force generated by the explosion of the fracturing tube from causing the fracturing tube to fly out, the radial pressure monitored by the pressure sensor Q The injection of hydraulic oil can be stopped only when the above formula is satisfied. Therefore, the clamp can more accurately control the limiting force on the fracturing pipe and ensure that the fracturing pipe will not be blown away when it explodes.

[0021] Furthermore, the top of the protective steel cylinder is evenly fixed with a number of fixing rings equal to the number of iron chains along the ring, and lock buckles are welded at both ends of the iron chain. The iron chain is connected to the protective steel cylinder through the fixing rings and the lock buckles. The protective steel cylinder can not only prevent the debris from splashing around during the test, but also provide a reaction force through its own weight to prevent the flying pipe.

[0022] Furthermore, the data acquisition component includes a plurality of strain components and velocity sensors fixed to the rock surface and electrically connected to the control module to collect rock strain, pressure change data and vibration velocity data. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the supercritical CO2 fracturing test device;

[0024] Figure 2is a schematic diagram of the internal structure of the tightener;

[0025] Figure 3 is a schematic diagram of the structure of the brake assembly;

[0026] Figure 4 It is a structural schematic diagram of the clamp;

[0027] Figure 5 is a cross-sectional schematic diagram of a clamp;

[0028] Figure 6 It is a schematic diagram of the structure of the box body of the tightener.

[0029] Among them, 1. protective steel cylinder; 2. fixing ring; 3. rock; 31. fracturing hole; 4. tightener; 41. capstan; 42. rotating shaft; 43. motor; 44. chain; 45. winding gear; 46. torque sensor; 47. driving gear; 48. brake assembly; 481. first oil cylinder; 482. telescopic rod; 483. brake sprocket; 484. buffer assembly; 485. brake plate; 49. box body; 6. clamp; 61. rubber pad; 62. second oil cylinder; 63. medium inlet; 64. medium outlet; 65. pressure sensor; 66. connecting piece; 67. notch; 68. piston; 7. fracturing tube; 8. strain assembly; 9. speed sensor. DETAILED DESCRIPTION

[0030] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0031] like Figure 1 As shown, the supercritical CO2 fracturing test device of this scheme includes a fracturing tube 7 and a sleeve-shaped protective steel cylinder 1 surrounding a rock 3. A data acquisition component is fixed on the rock 3, and the data acquisition component includes a plurality of strain components 8 and a velocity sensor 9 fixed on the surface of the rock. The strain data, pressure data and velocity data of the rock 3 can be collected. The fracturing tube 7 extends into the fracturing hole 31 inside the rock 3; the outer sleeve of the fracturing tube 7 is provided with a clamp 6, and the clamp 6 is connected to the protective steel cylinder 1 through at least two iron chains 44.

[0032] refer to Figure 2 and Figure 6Each iron chain 44 is provided with a tightener 4, which includes a box body 49 and a brake assembly 48 fixed inside the box body 49 for limiting the rotation of the driving gear 47. The box body 49 is fixedly connected with a motor 43, and the output shaft of the motor 43 is fixedly connected with the central axis of the driving gear 47; both sides of the driving gear 47 are meshed with a winding gear 45, and the winding gear 45 and the winch 41 for winding the iron chain 44 are fixed on the same rotating shaft 42, and the rotating shaft 42 is rotatably connected with the box body 49 through a bearing; the motor 43, the brake assembly 48, the data acquisition assembly and the clamp 6 are all electrically connected to the control module. The tightener 4 can tighten the iron chain 44, thereby pulling the fracture tube 7 to prevent it from being displaced by force and affecting the test results or causing safety hazards due to the flying tube.

[0033] The principle of the tightener 4 is as follows: the control module turns on the motor 43, and the motor 43 drives the driving gear 47 to rotate in one direction (clockwise for example), thereby driving the two winding gears 45 meshing therewith to rotate counterclockwise, and driving the capstan 41 to rotate counterclockwise, thereby tightening the iron chain 44. After the tightening is completed, the control module controls the brake assembly 48 to cooperate with the driving gear 47 to limit its rotation, thereby limiting the rotation of the winding gear 45 and the capstan 41, and preventing the iron chain 44 from reversing and falling off.

[0034] Before blasting, a fracturing hole needs to be opened on the rock 3, and then the fracturing tube 7 is inserted into the fracturing hole for blasting. The energy of the fracturing tube 7 is released for a certain period of time, and the impact force generated in the early stage of blasting is sufficient to make the fracturing tube 7 fly out. In order to avoid blasting failure caused by premature tube flight, in actual blasting work, the gap between the fracturing hole and the fracturing tube 7 is filled with sand or the like, and the fracturing tube 7 is fixed by friction. The fracturing tube 7 will fly out after the rock 3 is completely broken.

[0035] However, during the test, the data acquisition components are fixed at different positions of the rock 3, and the displacement of the fracturing tube 7 caused by the shock wave will obviously affect the collection of test data, and thus affect the test results. The test conditions are different from the actual blasting conditions. The opening depth of the fracturing hole 31 in the test is limited, and the friction generated is small, which makes the traditional sand filling fixation method unreliable and unable to prevent the displacement of the fracturing tube 7. When the rock 3 breaks, the sand filling fixation layer is also destroyed, and the fracturing tube 7 can no longer be fixed. In this case, this fixing method is not suitable for this test device. Therefore, this solution additionally sets up a protective device for fixing the fracturing tube 7, which can prevent the fracturing tube 7 from being displaced during the test and thus affecting the test results.

[0036] In one embodiment of this solution, reference Figure 3The brake assembly 48 includes a first oil cylinder 481 fixedly connected to the inner wall of the box body 49, and an arc-shaped brake plate 485 is fixedly connected to the end of the telescopic rod 482 of the first oil cylinder 481. The brake plate 485 has an arc-shaped cavity inside, and a brake toothed disc 483 slidably connected to the cavity wall is installed in the cavity. The meshing teeth of the brake toothed disc 483 extend from the opening of the cavity, and when the telescopic rod 482 is extended to the limit position, the meshing teeth of the brake toothed disc 483 mesh with the driving gear 47. The two ends of the brake toothed disc 483 are tightly connected with buffer assemblies 484, and the two buffer assemblies 484 are both in contact with the inner wall of the cavity perpendicular to the center arc direction.

[0037] When in use, the first oil cylinder 481 controls the extension and retraction of the telescopic rod 482 to enable the brake plate 485 to move up and down, so that the brake toothed disc 483 is engaged or separated with the driving gear 47, and the driving gear 47 can be prevented from rotating when the two are engaged. Specifically, the brake toothed disc 483 includes a fixed plate and meshing teeth fixedly connected to the fixed plate, and the meshing teeth extend out of the cavity. The fixed plate is located in the cavity and is slidably connected to the cavity wall. Since the fixed plate is not fixed to the cavity wall, the size of the fixed plate needs to be larger than the opening of the cavity to prevent the brake toothed disc 483 from being separated from the cavity.

[0038] When the brake toothed disc 483 is meshed with the driving gear 47, the buffer assembly 484 prevents the brake toothed disc 483 from sliding along the cavity, thereby stopping the driving gear 47 from rotating and braking the winch 41. In addition, when the fracturing tube 7 explodes, the pulling force of the iron chain 44 on the fracturing tube 7 is converted into a clockwise torque of the winding gear 45, and is also transmitted to the brake toothed disc 483.

[0039] At this time, if the tension on the iron chain caused by the explosion moment is greater than the preset tension value, the brake sprocket 483 will be allowed to produce a smaller rotation under the action of the buffer component 484, causing the winch 41 to rotate a certain amount to buffer the limiting tension on the iron chain 44, thereby protecting the brake component 48 from being damaged.

[0040] Preferably, the buffer assembly 484 is a high-strength spring, and the elastic modulus of the spring is:

[0041] ;

[0042] in, is the shear plate thickness of the cracked pipe; is the shear piece clamping diameter; is the shear strength of the shear sheet; is the ratio of pi; r is the radius of the fracture tube; R 1 is the radius of the capstan; n is the number of chains; R 3 is the radius of the driving gear; is the deformation of the spring; is the angle between the iron chain and the cracking tube; cos(·) is the cosine function.

[0043] Since the CO2 in the fracturing tube 7 is released by destroying the bottom shearing piece to form a supercritical CO2 jet to impact the borehole rock wall, the rock is destroyed. The difference of the shearing piece of the fracturing tube 7 will affect the impact force during blasting, thereby affecting the preset tension value on the iron chain 44. During the test process, it is often necessary to use the selection of the shearing piece as a variable to conduct multiple groups of tests with different shearing pieces. Therefore, springs with different elastic moduli can be matched according to different shearing pieces to obtain the most suitable buffering effect. The deformation of the spring is preferably about 0~5mm.

[0044] The first oil cylinder 481 is electrically connected to the control module. The central axis of the driving gear 47 is provided with a torque sensor 46 for transmitting the collected torque signal to the control module. When , the control module controls the first oil cylinder 481 to start;

[0045] in, M The torque data collected by the torque sensor; T is the preset tension value of the chain; R 2 is the radius of the rotation axis.

[0046] The torque sensor 46 can monitor the limiting tension on the iron chain 44 to prevent the fracturing tube 7 from flying out after the fracturing tube 7 releases energy. The tension on the iron chain 44 can be calculated from the data M collected by the torque sensor 46. When the tension reaches a preset value, the first oil cylinder 481 can be activated to drive the brake sprocket 483 to move upward to mesh with the driving gear 47.

[0047] refer to Figure 4 and Figure 5 The clamp 6 includes a sleeve-shaped second oil cylinder 62 and at least two pistons 68 arranged in an annular manner along the inner wall curved surface of the second oil cylinder 62, and the end of the piston 68 is fixedly connected to an arc-shaped rubber pad 61; along the outer wall curved surface of the second oil cylinder 62, a connecting piece 66 equal to the number of the iron chain 44 is fixedly connected in an annular manner, one end of the iron chain 44 is fixed to the connecting piece 66, and the other end is fixed to the protective steel cylinder 1;

[0048] The outer wall of the second oil cylinder 62 is provided with a medium inlet 63 and a medium outlet 64 which are connected to the inner cavity of the second oil cylinder 62; the medium inlet 63 is connected to the third oil cylinder outside. The hydraulic oil medium is injected into the second oil cylinder 62 through the medium inlet 63, and the hydraulic oil pushes the piston 68 to move radially. The rubber pad 61 connected to the piston 68 will also move radially and press the fracturing tube 7 in the middle, forming a clamping effect on the fracturing tube 7 to limit the upward movement of the fracturing tube 7. The notch 67 is when the piston 68 is extended, driving the rubber pad 61 away from the second oil cylinder 62, thereby forming a gap between the second oil cylinder 62 and the rubber pad 61.

[0049] When the present invention is implemented, it is preferred that the third oil cylinder is electrically connected to the control module, and the outer wall of the second oil cylinder 62 is provided with a pressure sensor 65 for transmitting the collected pressure signal to the control module. When , the control module controls the third oil cylinder to stop delivering the medium to the second oil cylinder 62. Further, Q can take 1.5~2 times the radial pressure as the design value, that is, when or When the control module controls the third oil cylinder to stop delivering the medium to the second oil cylinder 62 .

[0050] in, Q The radial pressure collected by the pressure sensor; μ is the friction coefficient between the rubber pad and the crack-causing tube; L is the height of the clamp; r is the radius of the fracture tube.

[0051] In order to prevent the impact force generated after the fracturing tube 7 explodes from causing the fracturing tube 7 to fly out, the injection of hydraulic oil can be stopped only when the radial pressure Q monitored by the pressure sensor 65 satisfies the above formula. Therefore, the clamp 6 can more accurately control the limiting force on the fracturing tube 7 and ensure that the fracturing tube 7 will not be flushed out when it explodes.

[0052] Preferably, the top of the protective steel cylinder 1 is evenly fixed with fixing rings 2 in a ring shape equal to the number of iron chains 44, and lock buckles are welded at both ends of the iron chains 44. The iron chains 44 are connected to the protective steel cylinder 1 through the fixing rings 2 and the lock buckles. The protective steel cylinder 1 can not only prevent gravel from splashing around during the test, but also provide a reaction force through its own weight to prevent the flying pipe. The protective steel cylinder 1 can be fixed to the ground by anchor bolts and the like. The iron chains 44 can be straightened and tightened by the tightener 4. The number of iron chains 44 can be four, each of which is connected in the same way. The iron chains 44 in each direction are tightened by the tightener 4, and the fracturing tube 7 is centered in the fracturing hole 31 by cooperatively adjusting the tightening degree of the iron chains 44 in four directions.

[0053] The protective steel cylinder 1 is made of steel plate. In one embodiment, the diameter of the protective steel cylinder 1 is 2000 mm, the height is 1000 mm, and the thickness is 10 mm. The fixing ring 2 is made of a steel bar with a diameter of 12 mm and is connected to the protective steel cylinder 1 by welding. The lock buckle is a nut-type lock buckle, and the two ends of the opening are provided with threads. After the lock buckle is closed, the two ends of the opening can be tightly fixed and connected by rotating the nut.

[0054] The iron chain 44 can be made of high-strength manganese steel with high tensile strength. A single ring of the iron chain 44 is an elliptical ring formed by bending a steel bar with a diameter of 10 mm. The span of the minor axis of the ellipse is 7 mm, the major axis is 15 mm, and the length of a single iron chain is 1500 mm. The rock 3 is a rock collected by in-situ cutting or a rock model cast from similar materials, with a length, width and height of 1000 mm. The diameter of the fracture hole 31 is 100 mm and the depth is 500 mm.

[0055] In summary, the present invention can tighten the fracturing tube 7 through the tightener 4 and the clamp 6 to prevent the fracturing tube 7 from being displaced by the shock wave during the test, thereby preventing the test results from being affected or the flying tube from causing safety hazards.

Claims

1. A supercritical CO2 fracturing test device, characterized in that: It comprises a fracturing tube (7) and a protective steel cylinder (1) surrounding a rock (3), a data acquisition assembly being fixed on the rock (3); the fracturing tube (7) extending into a fracturing hole (31) inside the rock (3); a clamp (6) being provided on the outer shell of the fracturing tube (7), the clamp (6) being connected to the protective steel cylinder (1) via at least two iron chains (44); Each iron chain (44) is provided with a tensioner (4), the tensioner (4) comprising a box body (49) and a brake assembly (48) fixed inside the box body (49) and used to limit the rotation of the driving gear (47), the box body (49) is fixedly connected to the inside of a motor (43), the output shaft of the motor (43) is fixedly connected to the central axis of the driving gear (47); both sides of the driving gear (47) are meshed with winding gears (45), the winding gears (45) and a winch (41) for winding the iron chain (44) are fixed on the same rotating shaft (42), and the rotating shaft (42) is rotatably connected to the box body (49) via a bearing; the motor (43), The brake assembly (48), the data acquisition assembly and the clamp (6) are all electrically connected to the control module; the brake assembly (48) comprises a first oil cylinder (481) fixedly connected to the inner wall of the box body (49); an arc-shaped brake plate (485) is fixedly connected to the end of the telescopic rod (482) of the first oil cylinder (481); an arc-shaped cavity is provided inside the brake plate (485); a brake toothed disc (483) slidably connected to the cavity wall is installed in the cavity; meshing teeth of the brake toothed disc (483) extend from the opening of the cavity; and when the telescopic rod (482) is extended to the limit position, the meshing teeth of the brake toothed disc (483) mesh with the driving gear (47); The two ends of the brake toothed disc (483) are tightly connected with buffer components (484), and the two buffer components (484) are both in contact with the side wall of the cavity; The clamp (6) comprises a sleeve-shaped second oil cylinder (62) and at least two pistons (68) arranged in an annular shape along the inner wall curved surface of the second oil cylinder (62), and the ends of the pistons (68) are fixedly connected to arc-shaped rubber pads (61); connecting pieces (66) equal in number to the iron chains (44) are fixedly connected in an annular shape along the outer wall curved surface of the second oil cylinder (62), one end of the iron chain (44) is fixed to the connecting piece (66), and the other end is fixed to the protective steel cylinder (1); The outer wall of the second oil cylinder (62) is provided with a medium inlet (63) and a medium outlet (64) which are communicated with the internal cavity of the second oil cylinder (62); the medium inlet (63) is connected to an external third oil cylinder.

2. The supercritical CO2 fracturing test device according to claim 1, characterized in that: The buffer component (484) is a high-strength spring, and the elastic modulus of the spring is: in, is the shear plate thickness of the cracked pipe; is the shear piece clamping diameter; is the shear strength of the shear sheet; is the ratio of pi; r is the radius of the fracture tube; R 1 is the radius of the capstan; n is the number of chains; R 3 is the radius of the driving gear; is the deformation of the spring; is the angle between the iron chain and the cracking tube; cos(·) is the cosine function.

3. The supercritical CO2 fracturing test device according to claim 1, characterized in that: The first oil cylinder (481) is electrically connected to the control module. The central axis of the driving gear (47) is provided with a torque sensor (46) for transmitting the collected torque signal to the control module. When the control module starts the first oil cylinder (481); in, M The torque data collected by the torque sensor; T is the preset tension value of the chain; R 2 is the radius of the rotation axis.

4. The supercritical CO2 fracturing test device according to claim 1, characterized in that: The third oil cylinder is electrically connected to the control module. The outer wall of the second oil cylinder (62) is provided with a pressure sensor (65) for transmitting the collected pressure signal to the control module. When the control module controls the third oil cylinder to stop conveying the medium to the second oil cylinder (62); in, Q The radial pressure collected by the pressure sensor; is the shear plate thickness of the cracked pipe; is the shear strength of the shear sheet; is the shear piece clamping diameter; μ is the friction coefficient between the rubber pad and the crack-causing tube; L is the height of the clamp; r is the radius of the fracture tube.

5. The supercritical CO2 fracturing test device according to claim 1, characterized in that: The top end of the protective steel cylinder (1) is evenly fixed with fixing rings (2) in a ring shape, the number of which is equal to the number of the iron chain (44). Lock buckles are welded at both ends of the iron chain (44). The iron chain (44) is connected to the protective steel cylinder (1) via the fixing rings (2) and the lock buckles.

6. The supercritical CO2 fracturing test device according to claim 1, characterized in that: The data acquisition component comprises a plurality of strain components (8) and velocity sensors (9) fixed to the surface of the rock (3) and electrically connected to the control module.

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