A method and apparatus for testing fracture conductivity under simulated in-situ conditions

Abstract

The present application relates to oil and gas exploration technology field, disclose a kind of fracture conductivity test method and device of formation condition simulation, the present application is based on similarity criterion selects and actual reservoir and similar material of surrounding rock as model raw material, then according to design size manufacturing surrounding rock model and reservoir model with fracturing fracture;Reservoir model and surrounding rock model are assembled to form reservoir surrounding rock model, and fixedly placed on triaxial loading unit;Reservoir surrounding rock model, triaxial loading unit and fluid injection and monitoring unit and displacement detection unit are connected to form fracture conductivity test experimental device, finally based on the experimental device carries out the fracturing fracture conductivity test experiment of reservoir surrounding rock model, and calculates the fracture conductivity coefficient of model.The present application can more accurately simulate the deformation law of fracture in actual reservoir, provide more accurate parameters for oil and gas reservoir numerical simulation model, so as to more accurately evaluate and calculate gas well productivity.

Description

Technical Field

[0001] This invention relates to the field of oil and gas exploration technology, specifically to a method and apparatus for testing the conductivity of fractures under simulated formation conditions. Background Technology

[0002] The rapid development of unconventional oil and gas resources has sparked a global boom in tight gas development. Compared to conventional gas reservoirs, tight gas reservoirs have small pore throats and extremely low permeability, requiring large-scale fracturing through long horizontal wells for effective extraction. Therefore, fracture conductivity plays a crucial role in tight gas extraction. Compared to the tight matrix, fractures are more susceptible to stress and deformation, causing changes in fracture conductivity and consequently affecting well productivity.

[0003] Fracture conductivity, defined as the product of fracture width and fracture permeability, is a crucial parameter in fracturing design for evaluating the effectiveness of fracturing operations, fundamentally determining the production capacity of wells after enhancement. Currently, tests for fracture conductivity fail to consider the influence of surrounding rock on reservoir stress and fracture deformation, leading to significant discrepancies between evaluated fracture conductivity and actual conditions. For example, invention patents CN111103222A and CN111157419A, both disclosing "a device and method for testing the conductivity of self-supporting fractures under triaxial confining pressure," merely design triaxial confining pressure loading on rock samples, failing to reflect the influence of surrounding rock on fracture conductivity. Summary of the Invention

[0004] To address the problems and shortcomings of the existing technologies, this invention proposes a method and apparatus for testing fracture conductivity under simulated formation conditions based on the reservoir deformation similarity criterion. By fabricating and assembling models of fractures, reservoirs, and surrounding rocks, the deformation patterns of fractures in actual reservoirs can be simulated more accurately, providing more accurate parameters for numerical simulation models of oil and gas reservoirs, thereby enabling more accurate evaluation and calculation of gas well productivity.

[0005] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows:

[0006] On the one hand, this invention proposes a method for testing the conductivity of fractures under simulated formation conditions, the method comprising the following steps:

[0007] Step S1. Design and determine the geometric parameters of the reservoir model and the surrounding rock model;

[0008] Step S2. Determine the geometric parameters of the hydraulic fractures in the reservoir model based on the monitoring results of the microseismic or wide-area electromagnetic method for the hydraulic fractures;

[0009] Step S3. Make reservoir model and surrounding rock model respectively, then check the air tightness of reservoir model, and finally attach three sets of strain gauges to the three mutually perpendicular outer surfaces of reservoir model.

[0010] Step S4. Assemble the reservoir model and the surrounding rock model to form a reservoir-surrounding rock model, and then place the assembled model on the triaxial loading unit and fix it.

[0011] Step S5. Combine the assembled reservoir surrounding rock model, triaxial loading unit, fluid injection and monitoring unit, and displacement detection unit to form a complete fracture conductivity testing experimental device;

[0012] Step S6. Conduct a test experiment on the hydraulic fracture conductivity of the model using the fracture conductivity testing experimental device, and calculate the hydraulic fracture conductivity coefficient of the model based on the experimental data.

[0013] Preferably, when making the reservoir model, fluid pipes are embedded in the reservoir model in advance as fluid inlets and outlets. The fluid inlets and outlets are connected to the fluid injection and monitoring unit, respectively. At the same time, pipeline channels are reserved in the surrounding rock model during its construction for the passage of the aforementioned fluid pipes.

[0014] Preferably, when making reservoir models and surrounding rock models, based on the Young's modulus and shear modulus of the actual reservoir and surrounding rock, similar materials are selected to make reservoir models and surrounding rock models according to the similarity criterion.

[0015] Preferably, the geometric parameters of the reservoir model and the surrounding rock model are the length, width, and height of the model, respectively; the geometric parameters of the hydraulic fracture include the number of fractures N, the fracture spacing d, and the length L of each fracture. fj Width w fj and height h fj , where (j = 1, 2, 3, ..., N).

[0016] Preferably, when checking the airtightness of the reservoir model, a thin layer of adhesive needs to be evenly applied to the outer surface of the reservoir model.

[0017] Preferably, the reservoir model and the surrounding rock model are made by casting and cutting.

[0018] Preferably, the portion of the fluid conduit located within the reservoir model has an opening.

[0019] Preferably, step S6 is as follows:

[0020] S6.1. Based on the actual reservoir stress, pore pressure magnitude, and the pressure variation range to be studied, set the initial state of the model; increase the stress on the X, Y, and Z axes through triaxial loading elements to simulate the actual reservoir stress magnitude; while increasing the model stress, increase the fluid pressure through the reservoir model fluid inlet and outlet to simulate the actual reservoir pore pressure P0;

[0021] S6.2. Close the triaxial loading unit and fix the model around its perimeter. Adjust the pressure regulating valve to reduce the pore pressure of the reservoir model by ΔP and keep it stationary. Record the strain gauge readings after it has come to a stop.

[0022] S6.2. Repeat the previous step, adjusting the pressure regulating valve each time to reduce the pore pressure of the reservoir model by ΔP, and record the strain gauge readings after the model comes to rest, until the pore pressure of the reservoir model drops to atmospheric pressure, and end the experiment.

[0023] S6.3. After the i-th pore pressure decrease, the change in the conductivity of the hydraulic fracture can be calculated from six strain variables and the pore pressure:

[0024]

[0025] Where k0w0 represents the initial conductivity of the hydraulic fracture. K m The bulk modulus of the material used to construct the reservoir model; e 1i e 2i e 3i e 4i e 5i and e 6i These are the readings of the six strain gauges after the i-th pore pressure drop; L fj w fj and h fj These represent the length, width, and height of the j-th crack in the model, respectively; ΔP i denoted as the i-th pore pressure drop value; L0, b0, and h0 are the geometric parameters of the reservoir model, respectively; kw is the hydraulic fracture conductivity.

[0026] Based on the same inventive concept, another aspect of the present invention provides a fracture conductivity testing device simulating formation conditions. This device is used to implement the aforementioned testing method and includes: a triaxial loading unit, a fluid injection and monitoring unit, and a displacement detection unit; wherein...

[0027] The three-axis loading unit includes a model support, a loading steel frame, a loading cylinder, and a gantry crane lifting device. The loading steel frame is fixed on the model support, and the loading cylinder is installed on the loading steel frame.

[0028] The fluid injection and monitoring unit includes a storage tank, a pressure regulating valve, a fluid injection pipeline, a back pressure valve, a flow meter, and an outlet pipeline. The storage tank is connected to one end of the fluid injection pipeline, and the other end of the fluid injection pipeline is connected to the inlet of the fluid pipeline of the reservoir surrounding rock model. The pressure regulating valve is installed on the fluid injection pipeline. One end of the outlet pipeline is connected to the outlet of the fluid pipeline of the reservoir surrounding rock model, and the other end is connected to the back pressure valve. The flow meter is connected to the back pressure valve.

[0029] The displacement detection unit includes strain gauges, which are connected to strain gauges attached to the reservoir surrounding rock model.

[0030] Preferably, the gantry crane includes a gantry and a lifting mechanism mounted on the gantry.

[0031] Preferably, the bottom of the gantry frame is provided with rollers.

[0032] The beneficial effects of this invention are:

[0033] 1. This invention, by creating and assembling models of fractures, reservoirs, and surrounding rocks, can more accurately simulate the deformation patterns of fractures in actual reservoirs, providing more accurate parameters for numerical simulation models of oil and gas reservoirs, thereby more accurately evaluating and calculating gas well productivity.

[0034] 2. This invention tests the conductivity of reservoir fractures by simulating actual formation conditions, which can accurately grasp the fracture deformation law. In turn, by changing the production system of oil and gas wells, the impact of fracture deformation on production can be reduced and the final recovery rate of a single well can be improved.

[0035] 3. This invention accurately grasps the crack deformation law, and after establishing a crack deformation model, it can use crack morphology, geometric parameters, and well test and production data obtained by means of microseismic monitoring to calculate the key parameters in the crack deformation model through inversion. Attached Figure Description

[0036] The foregoing and hereinafter detailed description of the invention becomes clearer when read in conjunction with the following drawings, in which:

[0037] Figure 1 This is a schematic diagram of the reservoir model and surrounding rock model assembled according to the present invention;

[0038] Figure 2 This is a structural diagram of the flow-guiding capacity testing device of the present invention;

[0039] Figure 3 This is a schematic diagram of the triaxial loading unit structure of the present invention.

[0040] In the picture:

[0041] 1. Model support; 2. Loading steel frame; 3. Loading cylinder; 4. Gantry crane; 5. Liquid storage tank; 6. Pressure regulating valve; 7. Injection pipeline; 8. Back pressure valve; 9. Flow meter; 10. Liquid outlet pipeline; 11. Reservoir model; 12. Surrounding rock model; 13. Fluid pipeline. Detailed Implementation

[0042] To enable those skilled in the art to better understand the technical solutions of this invention, several specific embodiments will be used to further illustrate the technical solutions for achieving the objectives of this invention. It should be noted that the technical solutions claimed by this invention include, but are not limited to, the following embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort should fall within the scope of protection of this invention.

[0043] The rapid development of unconventional oil and gas resources has sparked a global boom in tight gas development. Compared to conventional gas reservoirs, tight gas reservoirs have small pore throats and extremely low permeability, requiring large-scale fracturing through long horizontal wells for effective extraction. Therefore, fracture conductivity plays a crucial role in tight gas extraction. Compared to the tight matrix, fractures are more susceptible to stress and deformation, causing changes in fracture conductivity and consequently affecting well productivity.

[0044] Fracture conductivity, defined as the product of fracture width and fracture permeability, is a crucial parameter in fracturing design for evaluating the effectiveness of fracturing operations, fundamentally determining the production capacity of wells after enhancement. Currently, tests for fracture conductivity fail to consider the influence of surrounding rock on reservoir stress and fracture deformation, leading to significant discrepancies between the evaluated fracture conductivity and actual conditions. Under real formation conditions, the reservoir and surrounding rock are in close contact, and stress and strain are continuous at the boundary between them. However, conventional experimental testing methods do not consider the reservoir's influence and therefore cannot be considered to simulate formation conditions.

[0045] Based on this, embodiments of the present invention propose a method and apparatus for testing the conductivity of fractures under simulated formation conditions. By fabricating and assembling a model of fractures, reservoir, and surrounding rock, the present invention can more accurately simulate the deformation law of fractures in actual reservoirs, providing more accurate parameters for oil and gas reservoir numerical simulation models, thereby more accurately evaluating and calculating gas well productivity. Furthermore, by simulating actual formation conditions and testing the conductivity of reservoir fractures, the fracture deformation law can be accurately grasped, and the impact of fracture deformation on production can be reduced by changing the production regime of oil and gas wells, thereby improving the final recovery rate of single wells.

[0046] To facilitate understanding of the technical solution of this invention, the present invention first introduces and explains the method for testing the conductivity of cracks.

[0047] This embodiment discloses a method for testing the conductivity of fractures under simulated formation conditions. The method mainly includes the following steps.

[0048] Step S1. Based on the Young's modulus and shear modulus of the actual reservoir and surrounding rock, select similar materials to make reservoir and surrounding rock models based on similarity criteria; then, design and determine the geometric parameters of the reservoir and surrounding rock models according to the required fracture scale, technological level and laboratory environment; including the length L0, width b0 and height h0 of the reservoir model and the length L, width b and height h of the surrounding rock model.

[0049] In the embodiments described in this invention, the geometric parameters of the surrounding rock model are typically more than five times those of the reservoir model in order to eliminate the influence of the surrounding rock boundary on reservoir deformation.

[0050] It should also be noted that geometric parameters usually refer to the three parameters of the model: length, width, and height.

[0051] In the embodiments described in this invention, the similarity criterion refers to the similarity of elastic deformation, specifically that the ratio of the elastic modulus of the reservoir and surrounding rock to the elastic modulus of the model is equal to the ratio of the normal strain of the reservoir and surrounding rock to the normal strain of the model, and the ratio of the shear modulus of the reservoir and surrounding rock to the shear modulus of the model is equal to the ratio of the tangential strain of the reservoir and surrounding rock to the modulus tangential strain.

[0052] Step S2. Based on the monitoring results of microseismic or wide-area electromagnetic methods for fractured reservoirs, determine the geometric parameters of the fractures in the reservoir model, including the number of fractures N, the fracture spacing d, and the length L of each fracture. fj Width w fj and height h fj , where (j = 1, 2, 3, ..., N).

[0053] In the embodiments described in this invention, a hydraulic fracture refers to a hydraulic fracture formed after reservoir hydraulic fracturing.

[0054] Step S3. Cast the selected similar materials to form a reservoir model and a surrounding rock model respectively. During the reservoir model casting process, it needs to be fabricated based on the length, width, and height geometric parameters obtained in Step S1 and the pressure fracture geometric parameters obtained in Step S2. The length, width, and height of the fractures can be controlled by the mold. Furthermore, during the fabrication of the reservoir model, a flexible tube with an inner diameter of 2–4 mm needs to be embedded inside the reservoir model. Both ends of the tube extend to the outside of the reservoir model; one end serves as the fluid inlet, and the other end as the fluid outlet. The portion of the tube inside the reservoir model has a slender opening structure along its axial direction. The fluid introduced into the tube flows into the reservoir model through the opening structure.

[0055] Furthermore, the surrounding rock model is made based on the geometric parameters obtained in step S1, and during the casting process, attention should be paid to reserving pipeline channels of appropriate size on the model for installing the flexible hoses embedded in the reservoir model, so that they can be finally assembled with the reservoir model to form a whole.

[0056] In this invention, it should be noted that, in addition to the casting method described above, the reservoir model and the surrounding rock model can also be made by cutting. If the reservoir and surrounding rock models are made by cutting, the reservoir model is cut using a cutting instrument according to the geometric parameters of the pressure fracture determined in step S2 to form a reservoir model containing pressure fractures. When cutting the surrounding rock model, it is important to note that the size should be 3 to 5 times that of the reservoir. It is best to divide the surrounding rock model into three parts: upper, middle, and lower, and cut them separately. The upper and lower parts are consistent, and the height of the middle part is exactly equal to the height of the reservoir model.

[0057] It should also be noted that, for ease of calculation and analysis later, the model is usually made in the shape of a cuboid, but it can also be other shapes, but it is more complicated to calculate the strain from the strain value measured in the experiment.

[0058] In the embodiments described in this invention, after the model is made, a thin layer of adhesive is evenly applied to the outer periphery of the reservoir model to seal it. Then the airtightness of the model is checked. After the airtightness meets the requirements, three sets of thin strain gauges that are perpendicular to each other are attached to the three mutually perpendicular outer surfaces of the reservoir model. Then, pressure is evenly applied to the other three outer surfaces of the model to check the sensitivity of each strain gauge.

[0059] Step S4. Assemble the reservoir model and the surrounding rock model into a whole, forming the reservoir-surrounding rock model. After assembly, the two ends of the flexible hoses of the reservoir model extend to the outside of the entire model. Then, based on the actual reservoir stress, fracture pressure, pore pressure, and model geometric parameters, elastic modulus, and shear modulus, design the dimensions and maximum stress of the triaxial loading unit of the model. Then, design and manufacture the triaxial loading unit based on the dimensions and maximum stress of the triaxial loading unit. Finally, place the assembled reservoir-surrounding rock model on the triaxial loading unit and fix it.

[0060] In this invention, installation space for the reservoir model is reserved inside the surrounding rock model during the design phase. After the reservoir model is fabricated, it is embedded into the middle of the surrounding rock model. The entire model is then connected to the external fluid injection and monitoring unit via a flexible hose embedded in the reservoir model. A structural diagram of the assembled reservoir model and surrounding rock model is attached to the specification. Figure 1 As shown.

[0061] In this invention, it should be noted that the triaxial loading unit is a novel triaxial loading unit designed and manufactured based on the dimensions and maximum stress of a conventional triaxial testing machine. It differs from conventional triaxial testing machines and mainly consists of a model support 1, a loading steel frame 2, a loading cylinder 3, and a gantry crane 4. The entire loading steel frame 2 is fixed to the model support 1, and the top steel frame of the loading steel frame 2 is detachable for placing the model. The loading cylinder 3 is fixed to the loading steel frame 2. After the model is assembled, the assembled reservoir rock model is hoisted onto the model support 1 using the gantry crane 4, and then the top steel frame is fixed with screws. The four sides of the model are fixed by sliding steel plates 11 that allow for staggered loading, ensuring that the load is directly and effectively applied to the model.

[0062] Step S5. The assembled reservoir surrounding rock model is combined and connected with the fluid injection and monitoring unit and the displacement detection unit respectively. The combined body formed after connection, together with the triaxial loading unit, forms a complete experimental device for testing fracture conductivity.

[0063] Step S6. Test and calculate the hydraulic fracture conductivity coefficient of the model using the fracture conductivity testing experimental device formed by the above combination.

[0064] In this invention, the method for calculating the conductivity coefficient of the model hydraulic fracture in step S6 is as follows:

[0065] ① Based on the actual reservoir stress, pore pressure, and the required pressure variation range, the initial state of the model is set: stresses along the X, Y, and Z axes are increased using three stress loading cylinders to simulate the actual reservoir stress; simultaneously, fluid pressure is increased through the reservoir model's fluid inlet and outlet to simulate the actual reservoir pore pressure P0. Throughout this process, it is crucial to maintain close contact between the reservoir and surrounding rock model, ensuring that the fluid pressure remains consistently lower than the triaxial stress.

[0066] ② Turn off the three stress loading cylinders and fix the model around its perimeter. Adjust the pressure regulating valve to reduce the pore pressure ΔP in the reservoir model and keep it stationary. Record the strain gauge readings e after the model comes to a stop. 11 e 21 e 31 e 41 e 51 and e 61 .

[0067] ③ Repeat the previous step, adjusting the pressure regulating valve each time to reduce the pore pressure of the reservoir model by ΔP (the pressure reduction value ΔP can be different each time during the pressure regulation process), and record the strain reading e after it comes to rest. 1i e 2i e 3i e 4i e 5i and e6i (i represents the i-th adjustment of pore pressure), until the pore pressure of the reservoir model drops to atmospheric pressure, and the experiment ends.

[0068] ④ After the i-th pore pressure decrease, the change in the conductivity of the hydraulic fracture can be calculated from the six strain variables and the pore pressure. The calculation expression is as follows:

[0069]

[0070] Where k0w0 represents the initial conductivity of the hydraulic fracture. K m e is the bulk modulus of the material used in constructing the reservoir model. 1i e 2i e 3i e 4i e 5i and e 6i These are the readings of the six strain gauges after the i-th pore pressure drop; L fj w fj and h fj These represent the length, width, and height of the j-th crack in the model, respectively; ΔP i is the pore pressure drop value of the i-th time; L0, b0, and h0 are the geometric parameters of the reservoir model, respectively; kw is the current conductivity of the hydraulic fracture.

[0071] In this invention, it should be noted that k represents the equivalent permeability of the fracture, w represents the equivalent aperture of the fracture, and the product of these two parameters represents the fracture conductivity. w0 means the initial equivalent aperture of the fracture, and the product of k0 and w0 refers to the initial conductivity of the fracture. Therefore, the experiment of this invention ultimately obtains the dimensionless variation law of the fracture conductivity.

[0072] Furthermore, based on the same inventive concept, an embodiment of the present invention also provides a fracture conductivity testing device simulating formation conditions, as described in the appendix to the specification. Figure 2 and attached Figure 3 Specifically, the device may include a triaxial loading unit, a fluid injection and monitoring unit, and a displacement detection unit. The structure will be described in detail below.

[0073] The triaxial loading unit includes a model support 1, a loading steel frame 2, loading cylinders 3, and a gantry crane 4. The loading steel frame 2 is fixed on the model support 1 and is a cuboid frame structure composed of a four-sided steel frame and a top steel frame, wherein the top steel frame is detachable. The loading cylinders 3 are installed on the loading steel frame 2, and loading cylinders 3 are set in the X-axis, Y-axis, and Z-axis directions to apply loads to the top surface and four sides of the model to simulate in-situ formation pressure. The gantry crane 4 is located above the model support 1 and is used to hoist the assembled reservoir surrounding rock model.

[0074] The fluid injection and monitoring unit includes a storage tank 5, a pressure regulating valve 6, an injection pipeline 7, a back pressure valve 8, a flow meter 9, and an outlet pipeline 10. The storage tank 5 is connected to one end of the injection pipeline 7, and the other end of the injection pipeline 7 is connected to the inlet of the hose of the reservoir surrounding rock model. The pressure regulating valve 6 is installed on the fluid injection pipeline 7. One end of the outlet pipeline 10 is connected to the outlet of the hose of the reservoir surrounding rock model, and the other end is connected to the back pressure valve 8. The flow meter 9 is connected to the back pressure valve 8.

[0075] The displacement detection unit includes a strain gauge, which is connected to three strain gauges attached to the reservoir surrounding rock model.

[0076] After the reservoir model and surrounding rock model are assembled, the top steel frame of the loading steel frame 2 is disassembled. Then, the assembled reservoir and surrounding rock model is lifted using the gantry crane 4 and placed on the model support 1 from the top of the loading steel frame 2. The top steel frame is then reinstalled, and the entire model is located within the space enclosed by the loading steel frame 2. Then, the loading cylinder 3 is activated, and the loading cylinders 3 in the X, Y, and Z axes apply loads to the top surface and four sides of the model to simulate in-situ formation pressure. The fluid injection and monitoring unit and the displacement detection unit are then activated. The fluid in the storage tank 5 is pumped into the model through the fluid injection line 7 and the hose to simulate the actual pore pressure of the reservoir. The fluid flows out through the outlet line 10. By adjusting the pressure regulating valve, the pressure value of the fluid pumped into the model is continuously changed, thereby changing the pore pressure in the model. The displacement detection unit collects the strain gauge readings after each change in pore pressure. Finally, based on the initial pore pressure value, the change in pore pressure value, the strain gauge readings, the length, width and height of the fracture, and the geometric parameters of the reservoir model, the dimensionless variation law of the fracture conductivity is obtained.

[0077] In this invention, the gantry crane lifting device 4 includes a gantry 41 and a lifting mechanism 42 mounted on the gantry 41. The bottom of the gantry 41 is provided with rollers to facilitate the movement and handling of the device. The lifting mechanism 42 can slide on the crossbeam of the gantry and is used to lift the assembled reservoir rock model and place the model on the model support 1 from the top of the loading steel frame 2. The lifting mechanism 42 includes a lifting component and a hook connected to the lifting component. The lifting component can be a manual hoist, electric hoist, or other machine with lifting function.

[0078] In this invention, when the loading cylinder 3 applies a load, a loading steel plate 11 is provided between the loading head of the loading cylinder 3 and the model.

[0079] In this invention, a first pressure gauge is installed on the injection line and a second pressure gauge is installed on the outlet line.

[0080] The above description is merely a preferred embodiment of the present invention and is not intended to hinder the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for testing the conductivity of fractures under simulated formation conditions, characterized in that, Includes the following steps: Step S1. Design and determine the geometric parameters of the reservoir model and the surrounding rock model; Step S2. Determine the geometric parameters of the hydraulic fractures in the reservoir model based on the monitoring results of the microseismic or wide-area electromagnetic method for the hydraulic fractures; Step S3. Make reservoir model and surrounding rock model respectively, then check the air tightness of reservoir model, and finally attach three sets of strain gauges to the three mutually perpendicular outer surfaces of reservoir model. Step S4. Assemble the reservoir model and the surrounding rock model to form a reservoir-surrounding rock model, and then place the assembled model on the triaxial loading unit and fix it. Step S5. Connect and combine the assembled reservoir surrounding rock model, triaxial loading unit, fluid injection and monitoring unit and displacement detection unit to form a complete fracture conductivity testing experimental device; Step S6. Conduct a test experiment on the hydraulic fracture conductivity of the model using the fracture conductivity testing experimental device, and calculate the hydraulic fracture conductivity coefficient of the model based on the experimental data.

2. A method for testing the conductivity of fractures under simulated formation conditions, characterized in that, When constructing the reservoir model, fluid pipes are pre-embedded within the reservoir model as fluid inlets and outlets. These fluid inlets and outlets are connected to the fluid injection and monitoring units, respectively. Meanwhile, pipeline channels are reserved in the surrounding rock model during its construction for the passage of the aforementioned fluid pipes.

3. According to the method for testing fracture conductivity under simulated formation conditions as described in claim 1, when making reservoir models and surrounding rock models, based on the Young's modulus and shear modulus of the actual reservoir and surrounding rock, similar materials are selected to make reservoir models and surrounding rock models based on similarity criteria.

4. The method for testing fracture conductivity under simulated formation conditions according to claim 1, characterized in that, The geometric parameters of the reservoir model and the surrounding rock model are the length, width, and height of the model, respectively. The geometric parameters of the fracture include the number of fractures N, the fracture spacing d, and the length L of each fracture. fj Width w fj and height h fj , where (j = 1, 2, 3, ..., N).

5. The method for testing fracture conductivity under simulated formation conditions according to claim 1, characterized in that, When checking the airtightness of the reservoir model, a thin layer of adhesive needs to be evenly applied to the outer surface of the reservoir model.

6. The method for testing fracture conductivity under simulated formation conditions according to claim 1, characterized in that, The reservoir model and surrounding rock model are made by casting and cutting.

7. The method for testing fracture conductivity under simulated formation conditions according to claim 2, characterized in that, The portion of the fluid conduit located within the reservoir model has an opening.

8. The method for testing fracture conductivity under simulated formation conditions according to claim 1, characterized in that, Step S6 is as follows: S6.

1. Based on the actual reservoir stress, pore pressure magnitude, and the pressure variation range to be studied, set the initial state of the model; increase the stress on the X, Y, and Z axes through triaxial loading elements to simulate the actual reservoir stress magnitude; while increasing the model stress, increase the fluid pressure through the reservoir model fluid inlet and outlet to simulate the actual reservoir pore pressure P0; S6.

2. Close the triaxial loading unit and fix the model around its perimeter. Adjust the pressure regulating valve to reduce the pore pressure of the reservoir model by ΔP and keep it stationary. Record the strain gauge readings after it has come to a stop. S6.

3. Repeat the previous step, adjusting the pressure regulating valve each time to reduce the pore pressure of the reservoir model by ΔP, and record the strain gauge readings after the model comes to rest, until the pore pressure of the reservoir model drops to atmospheric pressure, and end the experiment. S6.

4. After the i-th pore pressure decrease, the change in the conductivity of the hydraulic fracture can be calculated from six strain variables and the pore pressure: Where k0w0 represents the initial conductivity of the hydraulic fracture. K m The bulk modulus of the material used to construct the reservoir model; e 1i e 2i e 3i e 4i e 5i and e 6i These are the readings of the six strain gauges after the i-th pore pressure drop; L fj w fj and h fj These represent the length, width, and height of the j-th crack in the model, respectively; ΔP i denoted as the i-th pore pressure drop value; L0, b0, and h0 are the geometric parameters of the reservoir model, respectively; kw is the hydraulic fracture conductivity.

9. A device for testing fracture conductivity under simulated formation conditions, characterized in that, The crack conductivity testing device is used to implement the testing method described in any one of claims 1-8, and includes: a triaxial loading unit, a fluid injection and monitoring unit, and a displacement detection unit; wherein... The three-axis loading unit includes a model support, a loading steel frame, a loading cylinder, and a gantry crane lifting device. The loading steel frame is fixed on the model support, and the loading cylinder is installed on the loading steel frame. The fluid injection and monitoring unit includes a storage tank, a pressure regulating valve, an injection pipeline, a back pressure valve, a flow meter, and an outlet pipeline. The storage tank is connected to one end of the injection pipeline, and the other end of the injection pipeline is connected to the inlet of the fluid pipeline of the reservoir surrounding rock model. The pressure regulating valve is installed on the injection pipeline. One end of the outlet pipeline is connected to the outlet of the fluid pipeline of the reservoir surrounding rock model, and the other end is connected to the back pressure valve. The flow meter is connected to the back pressure valve. The displacement detection unit includes a strain gauge, which is connected to a strain gauge attached to the reservoir surrounding rock model.

10. A fracture conductivity testing device simulating formation conditions according to claim 9, characterized in that, The gantry crane includes a gantry and a lifting mechanism mounted on the gantry.

11. A fracture conductivity testing device simulating formation conditions according to claim 10, characterized in that, The bottom of the gantry frame is equipped with rollers.

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