Experimental device and method for the change of permeability and friction properties during fault slip

Abstract

The invention belongs to the technical field of geological carbon fixation, and discloses an experimental device and method for the change of permeability and friction properties during fault slip, including a constant flow and constant pressure pump, a fluid displacement system, a triaxial stress control system, a core clamp, an axial loading mechanism, a seepage metering system and a data acquisition system; the device of the invention has a simple structure, convenient operation, and simple and convenient post-data processing, and can apply triaxial stress to the core sample to simulate the actual stress condition of the rock underground; the method of the invention can monitor the change law of permeability and dynamic friction coefficient in the dynamic slip process of the fault in real time, explore the mechanical mechanism of fault slip induced by fluid injection, clarify the influencing factors of fault slip, and avoid CO 2 Injection activation faults provide effective scientific guidance.

Description

Technical Field

[0001] The invention belongs to the technical field of geological carbon fixation, and in particular relates to an experimental device and method for the changes in permeability and friction properties during fault slip. Background Art

[0002] In the process of CO2 geological storage, CO2 fluid is injected into the target reservoir, and a large amount of CO2 is injected into the formation and enters the fault, causing CO2 leakage along the fault, which in turn affects the safety of CO2 storage. At present, there is no experimental device and method to monitor the dynamic changes of permeability and dynamic friction coefficient during the dynamic slip of the fault, so it is impossible to carry out relevant research on the fault slip mechanism and slip stability. Summary of the invention

[0003] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and to provide an experimental device and method for monitoring the changes in permeability and friction properties during fault slip, so as to solve the problem that the prior art lacks an experimental device and method for monitoring the dynamic changes of permeability and dynamic friction coefficient during the dynamic slip of the fault, making it impossible to carry out relevant research on the fault slip mechanism and slip stability.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] On the one hand, an experimental device for the change of permeability and friction properties during fault slip, which includes a constant flow and pressure pump, a fluid displacement system, a triaxial stress control system, a core holder, an axial loading mechanism, a seepage metering system and a data acquisition system;

[0006] The constant flow and constant pressure pump is connected to the fluid displacement system through a pipeline; the fluid displacement system is connected to the core holder through a pipeline, and the fluid displacement system injects fluid into the core holder; a core sample is placed in the core holder; the triaxial stress control system is connected to the core holder and the axial loading mechanism through a high-pressure pipeline, respectively, so as to apply triaxial stress to the core sample; the axial loading mechanism is arranged above the core holder, and the axial loading mechanism applies Z-direction stress in the triaxial stress to the core sample;

[0007] The seepage metering system is connected with the lower liquid outlet of the core holder; the data acquisition system is respectively connected with the constant flow and pressure pump, the three-axis stress control system, the core holder and the seepage metering system signal.

[0008] Furthermore, the core holder comprises a holder body, the holder body is placed on the experimental frame, and a core sample is installed in a rock cavity at the center of the holder body.

[0009] Furthermore, a clamp upper cover is sealedly connected to the top of the clamp body, and an upper loading head is installed at the center of the clamp upper cover; the upper end face of the upper loading head is connected to the axial loading system, and the lower end face of the upper loading head is embedded in the rock cavity; the bottom of the clamp body is meshed and connected with the lower loading head.

[0010] Furthermore, the lower end face of the upper loading head and the upper end face of the lower loading head both include two end face types, one of which is end face type I, which is a stepped non-flush end face; the other end face type is end face type II, which is a flat end face;

[0011] The stepped non-flush end surface includes plane A and plane B; plane A is higher than plane B, and plane B is provided with a number of circular hole grooves. During the experiment, a silicone sheet is placed on plane B so that the end surface of plane B on which the silicone sheet is placed is kept flush with plane A;

[0012] During the experiment, if the core sample slips, the silicone sheet is pressed into the circular hole groove;

[0013] A plurality of groove water lines are distributed on the plane end surface.

[0014] Furthermore, the step-shaped non-flush end surface and the plane end surface of the upper loading head are both provided with injection holes and wiring holes; the step-shaped non-flush end surface and the plane end surface of the lower loading head are both provided with injection holes.

[0015] Furthermore, a core seepage rubber sleeve is provided on the outer side of the core sample, and the lower end surface of the upper loading head is embedded in the core seepage rubber sleeve.

[0016] Further, the clamp body is provided with an X-axis pipeline connection hole, and the X-axis pipeline connection hole is communicated with the X-axis confining pressure chamber;

[0017] The Y-axis loading hydraulic cylinders are symmetrically arranged on both sides of the clamp body, and the Y-axis loading hydraulic cylinders tightly support the side pressure plates of the core sample through piston cylinders; the Y-axis loading hydraulic cylinders apply lateral pressure in the Y direction to the core sample;

[0018] The triaxial stress control system is respectively connected to the axial loading mechanism, the Y-axis loading hydraulic cylinder and the X-axis pipeline connection hole on the core holder through high-pressure pipelines.

[0019] Furthermore, the X-axis confining pressure cavity is a cavity between the core sample and the through hole of the clamp body, and the fluid displacement system injects high-pressure fluid into the rock cavity through the X-axis pipeline connection hole, and the high-pressure fluid applies lateral pressure in the X direction to the core sample.

[0020] Furthermore, an upper injection hole is opened on the clamp body; the upper injection hole is connected to the fluid displacement system through a pipeline; and a constant flow and constant pressure pump injects the fluid in the fluid displacement system into the rock cavity through the upper injection hole.

[0021] In a second aspect, an experimental method of an experimental device for measuring changes in permeability and friction properties during fault slip comprises the following steps:

[0022] S1. Select the end face type of the upper loading head and the lower loading head according to the fracture morphology of the core sample;

[0023] When the starting point or end point of the crack falls on the end face, a stepped non-flush end face is selected, i.e., end face type I;

[0024] When the starting point or end point of the crack does not fall on the end face, the plane end face is selected, that is, the end face type II;

[0025] S2. Install the lower loading head on the lower end joint of the experimental frame;

[0026] S3, placing the clamp body on the experimental frame, and the lower loading head and the clamp body are engaged with each other;

[0027] S4. If the end face type of the lower loading head is end face type I, place the silicone gasket on the plane B on the stepped non-flush end face to make the entire stepped non-flush end face flat, and then place a guide plate on the flattened stepped non-flush end face;

[0028] If the end face type of the lower loading head is end face type II, place the guide plate directly on the flat end face;

[0029] S5. Place the rectangular core sample on the guide plate, and then put a core seepage rubber sleeve on the outside of the core sample;

[0030] S6, placing the upper cover of the clamper on the upper part of the clamper body;

[0031] S7. If the end face type of the upper loading head is end face type I, a guide plate and a silicone gasket are placed on the upper end face of the core sample in sequence;

[0032] If the end face type of the upper loading head is end face type II, a guide plate is placed on the upper end face of the core sample;

[0033] Then, the upper loading head is installed on the upper cover of the clamp, and the upper loading head is embedded in the square core seepage rubber sleeve to achieve the sealing of the rock cavity;

[0034] S8, connecting the Y-axis loading hydraulic cylinder and the X-axis pipeline connection hole to the pipelines of the fluid displacement system respectively;

[0035] S9, controlling the operation of the loading shaft of the axial loading system, bringing the loading shaft into contact with the upper end surface of the upper loading head, and installing a displacement sensor in the Z-axis direction;

[0036] S10, setting the triaxial stress conditions required for the experiment, and controlling the triaxial stress control system to apply triaxial stress to the core sample;

[0037] S11, setting the fluid injection conditions of the experiment through a constant flow and constant pressure pump, and starting to inject the fluid;

[0038] S12. During the experiment, the data acquisition system is used to collect and record the displacement, pressure, flow rate and temperature data of the core sample before and after dynamic shear slip in real time;

[0039] At the same time, the seepage metering system can realize automatic online metering of the outlet flow, and the computer can collect the outlet flow data in real time to calculate the permeability change of the core sample;

[0040] S13. End the experiment.

[0041] The experimental device and method for the change of permeability and friction properties during fault slip provided by the present invention have the following beneficial effects:

[0042] The invention has a simple structure, is easy to operate, and has simple and convenient post-data processing. It can be used to study the mechanism of fault slip induced by CO2 injection process, clarify the relationship between injection parameters and fault slip, and provide an effective theoretical basis and technical support for ensuring the safety of CO2 geological storage.

[0043] The present invention can apply triaxial stress, simulate the actual stress condition of rock underground, monitor the change law of permeability and dynamic friction coefficient in the dynamic slip process of fault in real time, explore the mechanical mechanism of fault slip induced by fluid injection, clarify the influencing factors of fault slip, and provide effective scientific guidance for avoiding CO2 injection to activate faults.

[0044] The present invention can not only be used to study the dynamic change of structural surface friction coefficient and the shear slip stability characteristics, but also can monitor the permeability change of the fault system before and after the fault surface slips, and can quantitatively evaluate the impact of the dynamic slip of the fault on the permeability of the system, thereby evaluating the risk of carbon dioxide leakage; on the other hand, the core clamp of the present invention can achieve precise control of the slip amount of the fault, and can set different initial slip amounts to control its slip rate, so as to better assist the study of the mechanical properties of the fault surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the structure of the experimental device for the change of permeability and friction properties during fault slip in the present invention.

[0046] Figure 2 It is a schematic diagram of the structure of the core holder of the present invention.

[0047] Figure 3 The core holder structure of the present invention is a side view Figure 1 .

[0048] Figure 4 The core holder structure of the present invention is a side view Figure 2 .

[0049] Figure 5 This is a structural diagram of the loading head end face type I of the present invention.

[0050] Figure 6 This is a structural diagram of the loading head end face type II of the present invention.

[0051] Figure 7 This is a structural diagram of the loading head end face type I of the present invention.

[0052] Figure 8 This is a structural diagram of the loading head end face type II of the present invention.

[0053] Fig. 9 This is a structural diagram of the starting point and end point of the vertical cracks of the core sample of the present invention at the upper and lower end surfaces.

[0054] Fig.10 This is a structural diagram of the starting point and end point of the vertical cracks in the core sample of the present invention on the side.

[0055] Fig.11 This is a structural diagram showing that the starting point and end point of the vertical crack of the core sample of the present invention are respectively on the upper end surface and the side surface.

[0056] Fig.12 This is a structural diagram showing that the starting point and end point of the vertical crack of the core sample of the present invention are respectively on the side surface and the lower end surface.

[0057] Among them, 1. constant flow and constant pressure pump; 2. fluid displacement system; 3. triaxial stress control system; 4. experimental stand; 5. core clamp; 6. axial loading mechanism; 7. seepage metering system; 8. data acquisition system; 5-1. upper injection hole; 5-2. guide plate; 5-3. core seepage rubber sleeve; 5-4. silicone gasket; 5-5. lower liquid outlet; 5-6. upper loading head; 5-7. lower loading head; 5-8. clamp upper cover; 5-9. clamp body; 5-10. Y-axis loading hydraulic cylinder; 5-11. Y-axis pressure plate; 5-12. X-axis confining pressure chamber; 5-13. X-axis pipeline connection hole. DETAILED DESCRIPTION

[0058] 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.

[0059] Example 1

[0060] This embodiment provides an experimental device for the change of permeability and friction properties during fault slip. This embodiment has a simple structure and is easy to operate. It can apply triaxial stress to the core sample to simulate the actual stress condition of the rock underground. It specifically includes:

[0061] Constant flow and pressure pump 1, fluid displacement system 2, triaxial stress control system 3, experimental stand 4, core holder 5, axial loading mechanism 6, seepage metering system 7 and data acquisition system 8;

[0062] refer to Figure 1 , a constant flow and constant pressure pump 1 is connected to a fluid displacement system 2 through a pipeline; the fluid displacement system 2 is connected to a core holder 5 through a pipeline, and the fluid displacement system 2 injects fluid into the core holder 5; a core sample is placed in the core holder 5; a triaxial stress control system 3 is connected to the core holder 5 and an axial loading mechanism 6 through a high-pressure pipeline, respectively, to apply triaxial stress to the core sample; the axial loading mechanism 6 is arranged above the core holder 5, and the axial loading mechanism 6 applies Z-direction stress in the triaxial stress to the core sample;

[0063] The seepage metering system 7 is connected to the lower liquid outlet 5-5 of the core holder 5; the data acquisition system 8 is signal-connected to the constant-current and constant-pressure pump 1, the three-axis stress control system 3, the core holder 5 and the seepage metering system 7 respectively.

[0064] Specifically, the constant flow and constant pressure pump 1 is connected to the fluid displacement system 2 to provide a fluid injection condition of constant flow or constant pressure for the experiment.

[0065] The triaxial stress control system 3 directly adopts the existing technology, which includes an electro-hydraulic servo pump, valves and process pipelines, and is used to provide hydraulic power for true triaxial loading of the three-dimensional stress of the core sample.

[0066] The fluid displacement system 2 is connected to the constant flow and pressure pump 1 and the core holder 5 respectively. The fluid displacement system 2 includes three fluid intermediate containers, and the intermediate containers are filled with fluids to be injected in the experiment.

[0067] The axial loading mechanism 6 includes an axial loading piston cylinder, a loading frame, and an axial load sensor, which are used to provide Z-direction stress loading of triaxial stress for the core sample; wherein, the loading piston cylinder is located at the top of the loading frame, controls the lifting and lowering and applies axial pressure to the core sample, the loading frame is used to bear the reaction force of the axial pressure, and the upper loading head 5-6 is directly pressed on the upper end of the core sample. The upper loading head 5-6 is a structure with a channel and a sealing joint in the middle, which is connected to the displacement pump through a process pipeline to transport the displacement fluid. The axial load sensor is used to monitor the axial load in real time and control the Z-axis load.

[0068] The seepage metering system 7 is connected to the core holder 5. The seepage metering system 7 uses a high-precision electronic balance to indirectly calculate the volume flow rate, which can realize automatic online metering of the outlet flow and realize automation; the high-precision balance is connected to a computer, and the computer collects and calculates the data in real time and instantly displays the permeability changes of the rock on the display.

[0069] The data acquisition system 8 includes a computer, several sensors and corresponding acquisition software, which are used to monitor and collect pressure, flow, load, stress and strain data during the experiment.

[0070] The core holder 5 is connected to the fluid displacement system 2 and the seepage metering system 7, and is used to simulate the shear slip process of the core sample containing fractures;

[0071] Specifically, refer to Figure 2 , Figure 3 and Figure 4 The core clamp 5 of this embodiment includes an upper injection hole 5-1, a guide plate 5-2, a core seepage rubber sleeve 5-3, a silicone gasket 5-4, a lower liquid outlet 5-5, an upper loading head 5-6, a lower loading head 5-7, a clamp upper cover 5-8, a clamp body 5-9, a Y-axis loading hydraulic cylinder 5-10, a Y-axis pressure plate 5-11, an X-axis confining pressure chamber 5-12 and an X-axis pipeline connecting hole 5-13.

[0072] Among them, the clamp body 5-9 is a square column made of metal, which is used to bear the pressure applied by the deformation when the internal X-axis and Y-axis are loaded. It is placed on the experimental frame 4. The clamp body 5-9 is provided with an X-axis pipeline connecting hole 5-13, which can introduce the pressure source into the X-axis confining pressure chamber 5-12. In addition, the Y-axis loading hydraulic cylinder 5-10 is also installed on the clamp body 5-9. In this way, the stress in the X and Y directions can be loaded separately, and the core sample is installed in the center of the clamp.

[0073] An upper injection hole 5-1 is also provided on the clamp body 5-9, and the upper injection hole 5-1 is connected to the fluid displacement system 2 through a pipeline; the constant flow and constant pressure pump 1 injects the fluid in the fluid displacement system 2 into the rock cavity through the upper injection hole 5-1.

[0074] A clamp upper cover 5-8 is sealingly connected to the top of the clamp main body 5-9, and a circular sealing rubber ring is provided below the clamp upper cover 5-8 to ensure that the rock cavity is a closed space.

[0075] An upper loading head 5-6 is installed at the center position of the clamp upper cover 5-8, and the upper end face of the upper loading head 5-6 is connected to the axial loading system. The axial loading system acts on the upper loading head 5-6, thereby applying the Z-direction stress of the triaxial stress to the core sample; the lower end face of the upper loading head 5-6 is embedded in the rock cavity; the lower end face of the clamp body 5-9 is meshed and connected with the lower loading head 5-7.

[0076] As a preferred embodiment of this embodiment, refer to Figures 5 to 8 , the lower end surface of the upper loading head 5-6 and the upper end surface of the lower loading head 5-7 both include two end surface types, one of which is end surface type I, and end surface type I is a stepped non-flush end surface; the other end surface type is end surface type II, and end surface type II is a flat end surface;

[0077] The stepped non-flush end surface includes plane A and plane B; plane A is higher than plane B, and such a design can ensure the opposite moving space of the core when the core slides; in addition, a plurality of circular hole grooves are distributed on plane B, and the circular hole grooves of this embodiment can also be called countersunk holes. During the experiment, when the core sample slides and moves oppositely, the excess silicone gasket 5-4 is pressed into the circular hole groove;

[0078] The plane end surface is flush and has a plurality of groove waterlines distributed thereon.

[0079] In this embodiment, the upper loading head 5-6 has injection holes and wiring holes on both the stepped non-flush end face and the flat end face; the lower loading head 5-7 has injection holes on both the stepped non-flush end face and the flat end face, and the wiring holes are used to provide channels for the later installation of strain gauges, optical fibers and other equipment.

[0080] refer to Figures 9 to 12 In this embodiment, the end face types of the upper loading head 5-6 and the lower loading head 5-7 are selected according to the fracture morphology of the core sample, which are specifically:

[0081] When the starting point or end point of the crack falls on the end face, a stepped non-flush end face is selected, i.e., end face type I;

[0082] When the starting point or end point of the crack does not fall on the end face, a flat end face is selected, that is, end face type II.

[0083] A core seepage rubber sleeve 5-3 is provided outside the core sample to ensure pressure stability during fluid displacement, and the lower end surface of the upper loading head 5-6 is embedded in the core seepage rubber sleeve 5-3.

[0084] The clamp body 5-9 is provided with an X-axis pipeline connecting hole 5-13, and the X-axis pipeline connecting hole 5-13 is connected with the X-axis confining pressure chamber 5-12; the X-axis confining pressure chamber 5-12 is a cavity between the core sample and the intermediate through hole of the clamp body 5-9, and the fluid displacement system 2 injects high-pressure fluid into the rock cavity through the X-axis pipeline connecting hole 5-13, and the high-pressure fluid applies lateral pressure in the X direction to the core sample.

[0085] Y-axis loading hydraulic cylinders 5-10 are symmetrically arranged on both sides of the clamp body 5-9. The Y-axis loading hydraulic cylinders 5-10 are composed of a piston cylinder and a hydraulic piston. Oil is pumped into the piston cylinder by an electro-hydraulic servo pump, and the side pressure plate that tightly supports the core is pressed by the piston cylinder, thereby applying lateral pressure to the core sample. In this embodiment, the Y-axis side pressure plate is in direct contact with the core sample, and lateral pressure is applied to the core by the pressure provided by the Y-axis loading hydraulic cylinder 5-10.

[0086] The experimental installation process of this embodiment is:

[0087] Example 2

[0088] This embodiment provides an experimental method for the change of permeability and friction properties during fault slip;

[0089] This embodiment is based on the experimental device of embodiment 1, and the experimental device is installed first:

[0090] The constant flow and constant pressure pump 1 is connected to the fluid displacement system 2 through a pipeline, and the fluid displacement system 2 is connected to the upper injection hole 5-1 through a pipeline to realize the function of injecting liquid into the core; the triaxial stress control system 3 is respectively connected to the axial loading mechanism 6, the Y-axis loading hydraulic cylinder 5-10 and the X-axis pipeline connection hole 5-13 on the core holder 5 through high-pressure pipelines to apply triaxial stress to the core sample; the lower liquid outlet 5-5 of the core holder 5 is connected to the seepage metering system 7; the data acquisition system 8 is respectively connected to the flow and pressure sensors in the constant flow and constant pressure pump 1, the pressure sensor in the triaxial stress control system 3, the displacement and pressure sensors on the core holder 5 and the high-precision electronic balance of the seepage metering system 7;

[0091] After completing the installation of the above experimental device, the specific steps of this embodiment include:

[0092] Step S1, selecting the end face types of the upper loading head 5-6 and the lower loading head 5-7 according to the fracture morphology of the core sample;

[0093] When the starting point or end point of the crack falls on the end face, a stepped non-flush end face is selected, i.e., end face type I;

[0094] When the starting point or end point of the crack does not fall on the end face, the plane end face is selected, that is, the end face type II;

[0095] Step S2, installing the lower loading head 5-7 on the lower end joint of the experimental frame 4;

[0096] Step S3, placing the clamp body 5-9 on the experimental frame 4, and the lower loading head 5-7 and the clamp body 5-9 are meshed and connected with each other;

[0097] Step S4, if the end face type of the lower loading head 5-7 is end face type I, place the silicone gasket 5-4 on the plane B on the stepped non-flush end face to make the entire stepped non-flush end face flat, and then place the guide plate 5-2 on the flattened stepped non-flush end face;

[0098] If the end face type of the lower loading head 5-7 is end face type II, the guide plate 5-2 is placed directly on the plane end face;

[0099] Step S5, placing a rectangular core sample with a size of 50 mm×50 mm×100 mm on the guide plate 5-2, and then putting a core seepage rubber sleeve 5-3 on the outside of the core sample;

[0100] Step S6, placing the clamp upper cover 5-8 on the clamp main body 5-9;

[0101] Step S7, if the end face type of the upper loading head 5-6 is end face type I, then place the guide plate 5-2 and the silicone gasket 5-4 on the upper end face of the core sample in sequence;

[0102] If the end face type of the upper loading head 5-6 is end face type II, a guide plate 5-2 is placed on the upper end face of the core sample;

[0103] Then install the upper loading head 5-6 on the upper cover 5-8 of the clamp, embed the upper loading head 5-6 into the square core seepage rubber sleeve 5-3 to achieve the sealing of the rock cavity, and finally tighten all the screws of the upper cover 5-8 of the clamp;

[0104] Step S8, connecting the Y-axis loading hydraulic cylinder 5-10 and the X-axis pipeline connection hole 5-13 to the pipelines of the fluid displacement system 2 respectively;

[0105] Step S9, controlling the operation of the loading shaft of the axial loading system, bringing the loading shaft into contact with the upper end surface of the upper loading head 5-6, and installing a displacement sensor in the Z-axis direction;

[0106] Step S10, setting the triaxial stress conditions required for the experiment, and controlling the triaxial stress control system 3 to apply triaxial stress to the core sample;

[0107] Step S11, setting the fluid injection conditions of the experiment through the constant flow and constant pressure pump 1, and starting to inject the fluid;

[0108] Step S12: During the experiment, the data acquisition system 8 is used to collect and record the displacement, pressure, flow rate and temperature data of the core sample before and after the dynamic shear slip occurs in real time;

[0109] At the same time, the seepage metering system 7 realizes automatic online metering of the outlet flow, and the outlet flow data is collected in real time based on the computer to calculate the permeability change of the core sample;

[0110] Step S13, end the experiment.

[0111] Although the specific implementation of the invention is described in detail in conjunction with the drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. An experimental device for the change of permeability and friction properties during fault slip, characterized by: It includes a constant flow and pressure pump, a fluid displacement system, a triaxial stress control system, a core holder, an axial loading mechanism, a seepage metering system and a data acquisition system; The constant flow and constant pressure pump is connected to the fluid displacement system through a pipeline; the fluid displacement system is connected to the core holder through a pipeline, and the fluid displacement system injects fluid into the core holder; A core sample is placed in the core holder; the triaxial stress control system is connected to the core holder and the axial loading mechanism through high-pressure pipelines to apply triaxial stress to the core sample; the axial loading mechanism is arranged above the core holder, and the axial loading mechanism applies Z-direction stress in the triaxial stress to the core sample; The seepage metering system is connected to the lower liquid outlet of the core holder; the data acquisition system is respectively connected to the constant flow and constant pressure pump, the three-axis stress control system, the core holder and the seepage metering system signal; The core holder comprises a holder body, the holder body is placed on the experimental frame, and a core sample is installed in a rock cavity at the center of the holder body; The upper part of the clamp body is sealed and connected with the clamp upper cover, and the center of the clamp upper cover is equipped with an upper loading head; the upper end surface of the upper loading head is connected with the axial loading system, and the lower end surface of the upper loading head is embedded in the rock cavity; the lower part of the clamp body is meshed and connected with the lower loading head; The lower end face of the upper loading head and the upper end face of the lower loading head both include two end face types, one of which is end face type I, which is a stepped non-flush end face; the other end face type is end face type II, which is a flat end face; The stepped non-flush end surface includes plane A and plane B; plane A is higher than plane B, and plane B is provided with a plurality of circular hole grooves. During the experiment, a silicone sheet is placed on plane B so that the end surface of plane B on which the silicone sheet is placed is kept flush with plane A; During the experiment, if the core sample slips, the silicone sheet is pressed into the circular hole groove; A plurality of groove waterlines are distributed on the plane end surface; The step-shaped non-flush end surface and the plane end surface of the upper loading head are both provided with injection holes and wiring holes; the step-shaped non-flush end surface and the plane end surface of the lower loading head are both provided with injection holes; The clamp body is provided with an X-axis pipeline connection hole, and the X-axis pipeline connection hole is communicated with the X-axis confining pressure chamber; The Y-axis loading hydraulic cylinders are symmetrically arranged on both sides of the clamp body, and the Y-axis loading hydraulic cylinders support the side pressure plates of the core sample tightly through piston cylinders; the Y-axis loading hydraulic cylinders apply lateral pressure in the Y direction to the core sample; The three-axis stress control system is respectively connected to the axial loading mechanism, the Y-axis loading hydraulic cylinder and the X-axis pipeline connection hole on the core holder through high-pressure pipelines; The X-axis confining pressure cavity is a cavity between the core sample and the through hole of the clamp body. The fluid displacement system injects high-pressure fluid into the rock cavity through the X-axis pipeline connection hole, and the high-pressure fluid applies lateral pressure in the X direction to the core sample.

2. The experimental device for the change of permeability and friction properties during fault slip according to claim 1, characterized in that: The outer side of the core sample is covered with a core seepage rubber sleeve, and the lower end surface of the upper loading head is embedded in the core seepage rubber sleeve.

3. The experimental device for the change of permeability and friction properties during fault slip according to claim 1, characterized in that: An upper injection hole is provided on the clamp body; the upper injection hole is connected to the fluid displacement system through a pipeline; the constant flow and constant pressure pump injects the fluid in the fluid displacement system into the rock cavity through the upper injection hole.

4. An experimental method using the experimental device for the change of permeability and friction properties during fault slip according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Select the end face type of the upper loading head and the lower loading head according to the fracture morphology of the core sample; When the starting point or end point of the crack falls on the end face, a stepped non-flush end face is selected, i.e., end face type I; When the starting point or end point of the crack does not fall on the end face, the plane end face is selected, that is, the end face type II; S2. Install the lower loading head on the lower end joint of the experimental frame; S3, placing the clamp body on the experimental frame, and the lower loading head and the clamp body are engaged with each other; S4. If the end face type of the lower loading head is end face type I, place the silicone gasket on the plane B on the stepped non-flush end face to make the entire stepped non-flush end face flat, and then place a guide plate on the flattened stepped non-flush end face; If the end face type of the lower loading head is end face type II, place the guide plate directly on the flat end face; S5. Place the rectangular core sample on the guide plate, and then put a core seepage rubber sleeve on the outside of the core sample; S6, placing the upper cover of the clamper on the upper part of the clamper body; S7. If the end face type of the upper loading head is end face type I, a guide plate and a silicone gasket are placed on the upper end face of the core sample in sequence; If the end face type of the upper loading head is end face type II, a guide plate is placed on the upper end face of the core sample; Then, the upper loading head is installed on the upper cover of the clamp, and the upper loading head is embedded in the square core seepage rubber sleeve to achieve the sealing of the rock cavity; S8, connecting the Y-axis loading hydraulic cylinder and the X-axis pipeline connection hole to the pipelines of the fluid displacement system respectively; S9, controlling the operation of the loading shaft of the axial loading system, bringing the loading shaft into contact with the upper end surface of the upper loading head, and installing a displacement sensor in the Z-axis direction; S10, setting the triaxial stress conditions required for the experiment, and controlling the triaxial stress control system to apply triaxial stress to the core sample; S11, setting the fluid injection conditions of the experiment through a constant flow and constant pressure pump, and starting to inject the fluid; S12. During the experiment, the data acquisition system is used to collect and record the displacement, pressure, flow rate and temperature data of the core sample before and after dynamic shear slip in real time; At the same time, the seepage metering system can realize automatic online metering of the outlet flow, and the computer can collect the outlet flow data in real time to calculate the permeability change of the core sample; S13. End the experiment.

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