Fracture flow guiding device for monitoring dynamic change of fracture width under stress and testing method of fracture flow guiding device

Abstract

The invention belongs to the technical field of oil and gas exploitation, and relates to a fracture flow guide device for monitoring dynamic change of fracture width under stress and a testing method thereof, the device comprises a main body unit, a rock sample sealing unit, a fluid pumping and monitoring unit, a stress loading unit and a fracture width monitoring unit; wherein the main body unit is used for fixing a rock sample; the rock sample sealing unit is used for sealing a rock sample; the fluid pumping and monitoring unit is used for pumping fluid and measuring the flow of a rock sample; the stress loading unit is used for simulating the stress borne by the rock sample; the crack width monitoring unit is used for measuring the crack width in the rock sample. According to the invention, the initial average crack width of the crack is obtained through CT scanning and image segmentation processing, and the displacement change of the crack under different stress conditions can be obtained through the crack width monitoring unit, so that the real-time monitoring of the crack width during the crack diversion test under different stress conditions is realized; the method has an important supporting effect on long-term yield prediction of the fractured reservoir and optimization of a reservoir transformation process.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas exploitation, and particularly relates to a fracture diversion device for monitoring the dynamic change of fracture width under stress and a testing method thereof. Background Art

[0002] As an important development technology for unconventional oil and gas resources, hydraulic fracturing is an effective means to connect reservoirs and wellbores and increase the production of individual oil and gas wells. The propped fractures and activated natural fractures formed by hydraulic fracturing are the main channels for oil and gas to flow from the formation to the wellbore, and their conductivity is an important factor affecting the long-term production capacity of oil and gas wells. During the depletion development process, due to the decrease in formation pressure, the fractures close and the fracture conductivity decreases to varying degrees. Accurately understanding the dynamic relationship between fracture width and conductivity under stress conditions is helpful to accurately predict the long-term production capacity of oil and gas wells and provide a basis for the design of fracturing projects or the optimization of drainage and production systems.

[0003] The cracks produced by hydraulic fracturing include two types: propped cracks supported by proppants and self-supported cracks without proppants. The conventional practice of measuring the conductivity of proppant cracks currently mainly refers to the experimental method provided in the petroleum industry standard SY / T 6302-2019 "Test Method for Conductivity of Fracturing Proppants". The experimental sample used in this method is a smooth rock plate. The initial filling width and the change in width of the crack are measured using a vernier caliper, and the monitoring accuracy of the change in the width of the crack is low. Although the use of split fracture rock samples for fracture conductivity testing can reflect the true fracture morphology, the initial width of the fracture varies at different positions on the fracture surface, and the vernier caliper cannot accurately obtain the initial average width by measuring the width. Patent document CN 111157419A discloses a fracture conductivity test device and method under triaxial confining pressure conditions. Although an extensometer is used to monitor the displacement of the rock sample, it can only test the displacement of the fracture, and no method for measuring the initial width is given, and the measurement accuracy is low. Regarding the test of the conductivity of self-supporting cracks, the patent document CN111103222A also does not provide a method for measuring the initial width of the cracks. In summary, the current crack conductivity devices and test methods cannot truly and reliably monitor the dynamic changes of the crack width under stress. Summary of the invention

[0004] In view of the above problems, the technical solution adopted by the present invention is as follows: a fracture diversion device for monitoring the dynamic change of fracture width under stress, the device comprises a main unit, a rock sample sealing unit, a fluid pumping and monitoring unit, a stress loading unit and a fracture width monitoring unit; wherein,

[0005] The main unit is used to fix the rock sample;

[0006] The rock sample sealing unit is used to seal the rock sample;

[0007] The fluid pumping and monitoring unit is used to pump fluid and measure the flow rate of rock samples;

[0008] The stress loading unit is used to simulate the stress on the rock sample;

[0009] The crack width monitoring unit is used to measure the width of cracks inside the rock sample.

[0010] Furthermore, the main unit includes a pseudo triaxial testing machine confining pressure chamber, an upper pressure head and a lower pressure head; wherein the upper pressure head and the lower pressure head are both rigid cylinders, and the diameters of the upper pressure head and the lower pressure head are the same as the diameter of the rock sample;

[0011] The lower pressure head is installed at the bottom of the inner side of the confining pressure chamber of the pseudo triaxial testing machine, the bottom of the rock sample is fixed on the lower pressure head, and the upper pressure head is fixed on the top of the rock sample.

[0012] Furthermore, the rock sample sealing unit comprises a heat shrink sleeve and an O-ring; wherein,

[0013] The heat shrink sleeve is arranged on the outside of the rock sample, and the upper end of the heat shrink sleeve is fixed on the upper pressure head, and the lower end of the heat shrink sleeve is fixed on the lower pressure head;

[0014] The O-ring comprises an upper O-ring and a lower O-ring, which are respectively installed in the grooves of the upper pressure head and the lower pressure head.

[0015] Furthermore, the fluid pumping and monitoring unit includes a liquid injection device, a liquid injection pipeline, a liquid outlet pipeline and a flow monitoring device; wherein,

[0016] The injection device is connected to one end of the injection pipeline, and the other end of the injection pipeline passes through the confining pressure chamber of the pseudo triaxial testing machine and the downward pressure head respectively, and is connected to the bottom of the rock sample;

[0017] The flow monitoring device is connected to one end of the liquid outlet pipeline, and the other end of the liquid outlet pipeline passes through the confining pressure chamber of the pseudo triaxial testing machine and the upper pressure head respectively, and is connected to the top of the rock sample.

[0018] Furthermore, the stress loading unit includes a confining pressure loading pump and a confining pressure pipeline; wherein,

[0019] The confining pressure loading pump is connected to the interior of the confining pressure chamber of the pseudo triaxial testing machine through the confining pressure pipeline. The confining pressure loading pump is used to fill the confining pressure chamber of the pseudo triaxial testing machine with confining pressure oil and perform pressurization to simulate the stress on the rock sample.

[0020] Further, the seam width monitoring unit includes a fixing device; wherein the fixing device includes a front pressing plate, a rear pressing plate, a fixing rod and a spring;

[0021] The front pressing plate and the rear pressing plate are connected by a fixing rod;

[0022] The front pressing plate and the rear pressing plate are arranged on both sides of the rock sample;

[0023] The spring is used to tighten the front pressing plate and the rear pressing plate so that the front pressing plate and the rear pressing plate are closely attached to the surface of the rock sample.

[0024] Further, the seam width monitoring unit further comprises a linear variable differential transformer sensor, wherein the linear variable differential transformer sensor comprises a coil and an iron core;

[0025] The coil is mounted on the front pressing plate, and the iron core is mounted on the rear pressing plate.

[0026] In addition, the present invention also proposes a test method for the above-mentioned crack diversion device for monitoring the dynamic change of crack width under stress, the method comprising the following steps:

[0027] S1. Prepare rock samples;

[0028] S2, pre-scratch the side of the rock sample along the axial direction of the rock sample, and then perform core splitting;

[0029] S3. If the conductivity of the propped fracture is tested, a proppant is placed in the middle fracture of the rock sample after core splitting; if the conductivity of the self-propped fracture is tested, the next step is directly performed;

[0030] S4. Obtain a three-dimensional scanning image of the rock sample containing proppant, and obtain the initial crack width W through image segmentation processing. f0 ;

[0031] S5. Place the rock sample on the lower pressure head, then take a heat shrink sleeve and put it on the outside of the rock sample, and press the rock sample with the upper pressure head; heat and shrink the heat shrink sleeve to completely seal the rock sample;

[0032] S6. Install the fixture in the middle of the rock sample and ensure that the front and rear pressure plates are parallel to the cracks;

[0033] S7, loading the rock sample into the confining pressure chamber of the pseudo triaxial testing machine, and connecting the fluid pumping and monitoring unit, the crack width monitoring unit and the stress loading unit;

[0034] S8. Start the stress loading unit to load the confining pressure to the set pressure P, calculate the stress σ acting on the crack surface; calculate the crack width W according to the displacement change Δs monitored by the crack width monitoring unit f ;

[0035] S9, start the fluid pumping and monitoring unit, open the injection device, pump the fluid in through the injection pipeline, and the fluid flows out through the outlet pipeline and enters the flow monitoring device; monitor and calculate the pressure difference Δp between the upper and lower ends of the rock sample through the fluid pressure sensor in the injection device and the flow monitoring device; measure the flow at the outlet end of the rock sample through the flow monitoring device, and calculate the fracture permeability K under the current stress;

[0036] S10. Calculate the fracture conductivity KW under the current stress f .

[0037] Furthermore, the stress σ is: σ = P; the crack width W f W f =W f0 -Δs.

[0038] Furthermore, the fracture permeability K is: Among them, μ represents fluid viscosity, Q represents fluid flow rate, and Δp represents the pressure difference between the upper and lower ends of the rock sample.

[0039] Furthermore, the fracture conductivity KW f for:

[0040]

[0041] Furthermore, step S1 includes: processing the rock sample into a cylindrical rock sample suitable for a pseudo triaxial compression test, grinding the two end faces of the rock core by a grinding machine so that the two end faces are perpendicular to the axis of the rock core and the axial angle deviation does not exceed 0.05°.

[0042] Compared with the prior art, the present invention has the following beneficial effects: the fracture diversion device and the testing method thereof for monitoring the dynamic change of fracture width under stress proposed by the present invention obtain the initial average fracture width through CT scanning and image segmentation processing, and the displacement change of the fracture under different stress conditions can be obtained through the fracture width monitoring unit, thereby realizing real-time monitoring of the fracture width during fracture diversion testing under different stress conditions, which plays an important supporting role in the long-term production prediction of fractured reservoirs and the optimization of reservoir transformation processes.

[0043] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 The overall schematic diagram of the crack diversion device for monitoring the dynamic change of crack width under stress;

[0046] Figure 2 It is a schematic diagram of the device of the seam width monitoring unit;

[0047] Figure 3 A schematic diagram of a testing method for a fracture diversion device for monitoring the dynamic change of fracture width under stress;

[0048] Figure 4 It is the curve of crack width changing with stress;

[0049] Figure 5 is the curve of conductivity changing with stress;

[0050] Figure numerals: 1. confining pressure chamber of pseudo triaxial testing machine; 2. upper pressure head; 3. lower pressure head; 4. rock sample; 5. heat shrink sleeve; 6. O-ring; 7. liquid injection device; 8. liquid injection pipeline; 9. liquid outlet pipeline; 10. flow monitoring device; 11. confining pressure loading pump; 12. confining pressure pipeline; 13. fixing device; 14. linear variable differential transformer sensor; 15. front pressure plate; 16. rear pressure plate; 17. fixing rod; 18. spring; 19. crack. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] like Figure 1 and Figure 2As shown, a fracture diversion device for monitoring the dynamic change of fracture width under stress includes a main unit, a rock sample sealing unit, a fluid pumping and monitoring unit, a stress loading unit and a fracture width monitoring unit. The main unit includes a pseudo triaxial testing machine confining pressure chamber 1, an upper pressure head 2 and a lower pressure head 3. The upper pressure head 2 and the lower pressure head 3 are both rigid cylinders with the same diameter as the rock sample 4 to be tested. The lower pressure head 3 is fixedly installed at the inner bottom of the triaxial testing machine confining pressure chamber 1, the bottom of the rock sample 4 is fixed on the lower pressure head 3, and the upper pressure head 2 is fixed on the top of the rock sample 4.

[0053] The rock sample sealing unit includes a heat shrink sleeve 5 and an O-ring 6. In the embodiment of the present invention, the O-ring 6 includes an upper and a lower O-ring, which are respectively installed in the grooves of the upper pressure head 2 and the lower pressure head 3. The heat shrink sleeve 5 is sleeved on the outside of the rock sample 4, and the upper end of the heat shrink sleeve 5 is sleeved on the upper pressure head 2, and the lower end is fixed on the lower pressure head 3.

[0054] The fluid pumping and monitoring unit includes an injection device 7, an injection pipeline 8, a liquid outlet pipeline 9 and a flow monitoring device 10. The injection device 7 is connected to one end of the injection pipeline 8, and the other end of the injection pipeline 8 passes through the pseudo-triaxial testing machine confining pressure chamber 1 and the lower pressure head 3, and is connected to the bottom of the rock sample 4; the flow monitoring device 10 is connected to one end of the liquid outlet pipeline 9, and the other end of the liquid outlet pipeline 9 passes through the pseudo-triaxial testing machine confining pressure chamber 1 and the upper pressure head 2, and is connected to the top of the rock sample 4.

[0055] The stress loading unit includes a confining pressure loading pump 11 and a confining pressure pipeline 12. The confining pressure loading pump 11 is connected to the interior of the confining pressure chamber 1 of the pseudo triaxial testing machine through the confining pressure pipeline 12. The confining pressure loading pump 11 is used to fill the confining pressure chamber 1 with confining pressure oil and pressurize to simulate the stress on the rock sample 4.

[0056] The crack width monitoring unit includes a fixing device 13 and a linear variable differential transformer sensor 14, and the fixing device 13 includes a front pressure plate 15, a rear pressure plate 16, a fixing rod 17 and a spring 18. In the embodiment of the present invention, there are two linear variable differential transformer sensors 14. Further, the coil of the linear variable differential transformer sensor 14 is installed on the front pressure plate 15, and the iron core is installed on the rear pressure plate 16. The front pressure plate 15 and the rear pressure plate 16 are respectively located at the front and rear sides of the rock sample 4, connected by a fixing rod 17 and can slide freely relative to each other, and can ensure that the front pressure plate 15 and the rear pressure plate 16 always remain parallel during the sliding process. The spring 18 is used to tighten the front pressure plate 15 and the rear pressure plate 16 so that the front pressure plate 15 and the rear pressure plate 16 are tightly attached to the surface of the rock sample 4. The crack width monitoring unit is used to accurately measure the internal crack width of the rock sample 4 during the experiment.

[0057] like Figure 3The present invention shows a testing method of the above-mentioned crack diversion device for monitoring the dynamic change of crack width under stress, which comprises the following steps:

[0058] S1: Prepare rock sample 4: The sources of rock sample 4 include underground core, outcrop core and artificial core. The rock sample 4 is processed into a cylindrical rock sample 4 of a certain specification suitable for pseudo triaxial compression test. The two end faces of the rock sample are flattened by a grinding machine so that the two end faces are perpendicular to the axis of the rock core, and the axial angle deviation does not exceed 0.05°;

[0059] S2: Making cracks: Pre-scratch a splitting scratch along the axial direction of the rock sample 4 on the side of the rock sample 4, then put it into the rock sample splitting device, adjust the core position according to the splitting scratch so that the splitting tool is aligned with the scratch, and fix the core to ensure that the splitting is successfully implemented in the core splitting device, and then slowly pressurize until the splitting pressure no longer increases sharply and the core cracks along the splitting scratch, so as to achieve core splitting;

[0060] S3: taking the rock sample 4 out of the rock sample splitting device, and placing a proppant in the middle crack of the rock sample 4 if the propped fracture conductivity is to be tested; and directly proceeding to the next step of the experiment without placing a proppant in the middle crack of the rock sample 4 if the self-propped fracture conductivity is to be tested;

[0061] S4: Obtaining the initial crack width: The rock sample 4 is placed in a CT scanner to obtain a three-dimensional scanning image of the rock sample containing proppant, and the initial crack width W is obtained by image segmentation processing. f0 ;

[0062] S5: Place the rock sample 4 on the lower pressure head 3, then take the heat shrink sleeve 5 and put it on the outside of the rock sample 4, and use the upper pressure head 2 to press and stabilize the rock sample 4, and use a hot air gun to heat and shrink it, so that the heat shrink sleeve 5 completely seals the rock sample 4, so that the rock sample 4 can be isolated from the confining pressure oil in the experiment;

[0063] S6: Install a fixture 13 and an LVDT sensor 14 for crack width monitoring, install the fixture 13 in the middle of the rock sample 4 and ensure that the front pressure plate 15 and the rear pressure plate 16 are parallel to the crack 19;

[0064] S7: loading the rock sample 4 into the confining pressure chamber 1 of the pseudo triaxial testing machine, and connecting the fluid pumping and monitoring unit, the crack width monitoring unit and the stress loading unit;

[0065] S8: Start the stress loading unit to load the confining pressure to the set pressure P, calculate the stress σ acting on the crack surface; calculate the crack width W in real time according to the displacement change Δs monitored by the crack width monitoring unit f ;

[0066] S9: Start the fluid pumping and monitoring unit, open the injection device 7, pump the fluid in through the injection pipeline 8, and the fluid flows out through the outlet pipeline 9 and enters the flow monitoring device 10 to conduct a permeability evolution experiment; monitor and calculate the pressure difference Δp between the upper and lower ends of the rock sample 4 through the fluid pressure sensor in the injection device 7 and the flow monitoring device 10; measure the flow data at the outlet end of the rock sample 4 through the flow monitoring device 10 to calculate the fracture permeability K under the current stress;

[0067] S10: Calculation of fracture conductivity using Darcy's law KW f :

[0068] In the above step S8, the stress σ is calculated by the formula: σ = P; the crack width W f The calculation formula is: f =W f0 -Δs; crack width W f The curve of stress σ is as follows Figure 4 As shown in the figure, the displacement change Δs is nonlinear with the stress σ, so the crack width W f The change with stress σ is also nonlinear, and as the stress σ increases, the crack width W f Gradually decreases. When the stress σ increases to 30MPa, the stress σ continues to increase, and the crack width W f Remains basically unchanged.

[0069] In the above step S9, the calculation formula of the crack permeability K is: Where μ represents fluid viscosity in mPa·s; Q represents fluid flow in cm 3 / min; Δp represents the pressure difference between the upper and lower ends of the rock sample 4, and the unit is kPa.

[0070] In the above step S10, the fracture conductivity KW f The calculation formula is: Fracture conductivity KW f The unit is μm 2 ·cm. Figure 5 The stress represented by the horizontal axis corresponds to the stress σ on the fracture surface. As the stress σ on the fracture surface increases, the fracture conductivity KW f Gradually decreases. When the stress σ on the fracture surface increases to 30MPa, it continues to increase. The fracture conductivity KW f Remains basically unchanged.

[0071] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A crack diversion device for monitoring the dynamic change of crack width under stress, characterized in that: The device comprises a main unit, a rock sample sealing unit, a fluid pumping and monitoring unit, a stress loading unit and a crack width monitoring unit; wherein, The main unit is used to fix the rock sample (4); The rock sample sealing unit is used to seal the rock sample (4); The fluid pumping and monitoring unit is used to pump fluid and measure the flow rate of the rock sample (4); The stress loading unit is used to simulate the stress on the rock sample (4); The crack width monitoring unit is used to measure the width of cracks inside the rock sample (4).

2. The device according to claim 1, characterized in that The main unit comprises a pseudo triaxial testing machine confining pressure chamber (1), an upper pressure head (2) and a lower pressure head (3); wherein: The upper pressure head (2) and the lower pressure head (3) are both rigid cylinders, and the diameters of the upper pressure head (2) and the lower pressure head (3) are the same as the diameter of the rock sample (4); The lower pressure head (3) is installed at the bottom of the inner side of the confining pressure chamber (1) of the pseudo triaxial testing machine, the bottom of the rock sample (4) is fixed on the lower pressure head (3), and the upper pressure head (2) is fixed on the top of the rock sample (4).

3. The device according to claim 1, characterized in that The rock sample sealing unit comprises a heat shrink sleeve (5) and an O-ring (6); wherein: The heat shrink sleeve (5) is sleeved on the outer side of the rock sample (4), and the upper end of the heat shrink sleeve (5) is fixed on the upper pressure head (2), and the lower end of the heat shrink sleeve (5) is fixed on the lower pressure head (3); The O-ring (6) comprises an upper O-ring and a lower O-ring, which are respectively installed in the grooves of the upper pressure head (2) and the lower pressure head (3).

4. The device according to claim 1, characterized in that The fluid pumping and monitoring unit comprises a liquid injection device (7), a liquid injection pipeline (8), a liquid outlet pipeline (9) and a flow monitoring device (10); wherein: The injection device (7) is connected to one end of the injection pipeline (8), and the other end of the injection pipeline (8) passes through the confining pressure chamber (1) of the pseudo triaxial testing machine and the lower pressure head (3) respectively, and is connected to the bottom of the rock sample (4); The flow monitoring device (10) is connected to one end of the liquid outlet pipeline (9), and the other end of the liquid outlet pipeline (9) passes through the pseudo triaxial testing machine confining pressure chamber (1) and the upper pressure head (2) respectively, and is connected to the top of the rock sample (4).

5. The device according to claim 1, characterized in that The stress loading unit comprises a confining pressure loading pump (11) and a confining pressure pipeline (12); wherein, The confining pressure loading pump (11) is connected to the interior of the confining pressure chamber (1) of the pseudo triaxial testing machine through the confining pressure pipeline (12). The confining pressure loading pump (11) is used to fill the confining pressure chamber (1) of the pseudo triaxial testing machine with confining pressure oil and to perform pressurization to simulate the stress to which the rock sample (4) is subjected.

6. The device according to claim 1, characterized in that The seam width monitoring unit comprises a fixing device (13); wherein the fixing device (13) comprises a front pressing plate (15), a rear pressing plate (16), a fixing rod (17) and a spring (18); The front pressing plate (15) and the rear pressing plate (16) are connected via a fixing rod (17); The front pressing plate (15) and the rear pressing plate (16) are arranged on both sides of the rock sample (4); The spring (18) is used to tighten the front pressure plate (15) and the rear pressure plate (16) so that the front pressure plate (15) and the rear pressure plate (16) are closely attached to the surface of the rock sample (4).

7. The device according to claim 6, characterized in that The seam width monitoring unit further comprises a linear variable differential transformer sensor (14), wherein the linear variable differential transformer sensor (14) comprises a coil and an iron core; The coil is mounted on the front pressure plate (15), and the iron core is mounted on the rear pressure plate (16).

8. A method for testing a crack diversion device for monitoring the dynamic change of crack width under stress as claimed in any one of claims 1 to 7, characterized in that: The method comprises the following steps: S1. preparing a rock sample (4); S2, pre-scratching a splitting mark along the axial direction of the rock sample (4) on the side of the rock sample (4), and then performing core splitting; S3, if the conductivity of the propped fracture is tested, then a proppant is placed in the middle fracture of the rock sample (4) after core splitting; if the conductivity of the self-propped fracture is tested, then the next step is directly performed; S4, obtaining a three-dimensional scanning image of the rock sample (4) containing the proppant, and obtaining the initial crack width W of the crack by image segmentation processing f0 ; S5, placing the rock sample (4) on the lower pressure head (3), then taking the heat shrink sleeve (5) and putting it on the outside of the rock sample (4), and pressing the rock sample (4) with the upper pressure head (2); heating and shrinking the heat shrink sleeve (5) so that it completely seals the rock sample (4); S6. Install the fixing device (13) in the middle of the rock sample (4), and ensure that the front pressing plate (15) and the rear pressing plate (16) remain parallel to the crack (19); S7, loading the rock sample (4) into the confining pressure chamber (1) of the pseudo triaxial testing machine, and connecting the fluid pumping and monitoring unit, the crack width monitoring unit and the stress loading unit; S8. Start the stress loading unit to load the confining pressure to the set pressure P, calculate the stress σ acting on the crack surface; calculate the crack width W according to the displacement change Δs monitored by the crack width monitoring unit f ; S9, start the fluid pumping and monitoring unit, open the liquid injection device (7), pump fluid into the liquid injection pipeline (8), and the fluid flows out through the liquid outlet pipeline (9) and enters the flow monitoring device (10); monitor and calculate the pressure difference Δp between the upper and lower ends of the rock sample (4) through the fluid pressure sensors in the liquid injection device (7) and the flow monitoring device (10); measure the flow rate at the outlet end of the rock sample (4) through the flow monitoring device (10), and calculate the fracture permeability K under the current stress; S10. Calculate the fracture conductivity KW under the current stress f .

9. The method according to claim 8, characterized in that Stress σ is: σ = P; crack width W f W f =W f0 -Δs.

10. The method according to claim 9, characterized in that The fracture permeability K is: Wherein, μ represents fluid viscosity, Q represents fluid flow rate, and Δp represents the pressure difference between the upper and lower ends of the rock sample (4).

11. The method according to claim 9, characterized in that Fracture conductivity KW f for:

12. The method according to any one of claims 8 to 11, characterized in that: Step S1 comprises: processing the rock sample (4) into a cylindrical rock sample (4) suitable for a pseudo triaxial compression test, grinding the two end faces of the rock core by a grinding machine so that the two end faces are perpendicular to the axis of the rock core and the axial angle deviation does not exceed 0.05°.

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