Multi-well true triaxial hydraulic fracturing outlet pressurizing plate and stress interference monitoring experiment device and method

Abstract

The embodiment of the invention provides a multi-well true triaxial hydraulic fracturing outlet pressurizing plate and a stress interference monitoring experiment device and method. The multi-well true triaxial hydraulic fracturing outlet pressurizing plate at an outlet of a core cabin is designed in a split mode, the requirement of a multi-well true triaxial hydraulic fracturing experiment is met, the split structure of a metal sliding block and a rectangular groove can be freely adjusted and positioned according to the layout of a shaft, and the problem that the position of the shaft of a traditional integral pressurizing plate is fixed is solved; in addition, high-strength sealing is carried out on the rock sample on the basis that the overall size of the cubic rock sample is not changed, and fluid changes in the actual fracturing process on site are restored more truly. A three-dimensional induced stress model is constructed in stress interference monitoring, and a pressure fluctuation dynamic correction mechanism is combined to quantify an inter-well stress interference effect, so that the problem of insufficient spatial resolution caused by local discrete points in a traditional monitoring means is solved, and the goodness of fit between an experimental result and an actual fracturing working condition is improved.

Description

Technical Field

[0001] The present application relates to the technical field of oilfield development, and in particular to a multi-well true triaxial hydraulic fracturing outlet pressure plate, a stress interference monitoring experimental device and a method. Background Art

[0002] Fracturing crosstalk refers to the pressure changes and crack expansion caused by the injection of liquid during the hydraulic fracturing process, which not only affects the output of a single well, but may also cause pressure interference between wells and even trigger unpredictable changes in the formation.

[0003] At present, indoor hydraulic fracturing experiments are an effective means to study the propagation of fractures. However, in indoor experiments with multiple fractures or multiple wells, the problem of crosstalk between wells cannot be effectively monitored, making it impossible to quantify the changes in the stress field at different locations within the rock sample. Summary of the Invention

[0004] The embodiments of the present application provide a multi-well true triaxial hydraulic fracturing outlet pressure plate, a stress interference monitoring experimental device and method, which are used to quantify the stress magnitude at different locations inside a rock sample.

[0005] In the first aspect, the embodiment of the present application provides a multi-well true triaxial hydraulic fracturing outlet pressure plate, comprising: a pressure plate body 100 and a plurality of metal sliders 200; the four corners of the pressure plate body 100 are respectively provided with mounting holes 101, and the mounting holes 101 are used to fix the inner surface of the pressure plate body 100 to the core chamber of the stress interference monitoring experimental device; a rectangular groove 102 is provided in the central area of ​​the outer side of the pressure plate body 100, the length of the rectangular groove 102 is equal to the length of the pressure plate body 100 and passes through the pressure plate body 100, and the width of the rectangular groove 102 is equal to the length of the pressure plate body 100 and passes through the pressure plate body 100. The height of the rectangular groove 102 is equal to the sum of the widths of multiple metal sliders 200; a plurality of through-hole grooves 103 are arranged in the rectangular groove 102, and fixing holes 104 are symmetrically arranged on both sides of each hole groove 103; a matching hole 201 is provided in the central area of ​​each metal slider 200, and fixing grooves 202 are symmetrically arranged on both sides of the matching hole 201; the matching hole 201 is used to connect to the wellbore in the core chamber passing through the hole groove 103, and the fixing groove 202 is used to fix the metal slider 200 to the fixing hole 104 of the rectangular groove 102.

[0006] Optionally, a plurality of through holes 103 are arranged in parallel along the width direction of the rectangular groove 102 .

[0007] In a second aspect, an embodiment of the present application provides a stress interference monitoring experimental device, comprising: a core chamber, a carrying device, a three-dimensional stress loading device, an injection system, a pressure monitoring and data acquisition system, and a multi-well true triaxial hydraulic fracturing outlet pressure plate as described in the first aspect above; the core chamber is located in the carrying device and is used to place the target rock sample; a left pressure plate is provided on the outer side of the left side of the core chamber, an upper pressure plate is provided on the outer side of the upper side of the core chamber, a lower pressure plate is provided on the outer side of the lower side of the core chamber, a front pressure plate is provided on the outer side of the front side of the core chamber, and a rear pressure plate is provided on the outer side of the rear side of the core chamber; the multi-well true triaxial hydraulic fracturing outlet pressure plate is located on the outer side of the outlet of the core chamber; the three-dimensional stress loading device comprises pressure plates provided on the upper pressure plate, the left pressure plate and the front pressure plate, respectively. The outer hydraulic cylinder is used to apply triaxial stress to the target rock sample; the injection system includes a dual-cylinder injection pump, a first fracturing fluid container, a second fracturing fluid container, a first pressure sensor and a second pressure sensor; the dual-cylinder injection pump is connected to the first fracturing fluid container and the second fracturing fluid container respectively through fracturing pipelines, and the first fracturing fluid container is connected to the wellbore of the first simulated well pre-buried in the target rock sample through the first injection pipeline; the second fracturing fluid container is connected to the wellbore of the second simulated well pre-buried in the target rock sample through the second injection pipeline; the first pressure sensor is located on the first injection pipeline, and the second pressure sensor is located on the second injection pipeline; the pressure monitoring and data acquisition system is connected to the first pressure sensor, the second pressure sensor and the dual-cylinder injection pump for collecting and processing pressure data.

[0008] In a third aspect, an embodiment of the present application provides a stress interference monitoring experimental method, which adopts the stress interference monitoring experimental device as described in the second aspect above, including: taking a cubic rock sample for a stress interference monitoring experiment, sealing the cubic rock sample to obtain a treated rock sample; drilling two simulated wells at preset positions on the treated rock sample, and lowering a wellbore into each simulated well and performing cementing treatment to obtain a target rock sample; placing the target rock sample into a core chamber, and sealing the outlet of the core chamber using a multi-well true triaxial hydraulic fracturing outlet pressure plate; connecting each wellbore to an injection system through an injection pipeline; applying triaxial stress to the target rock sample through a three-dimensional stress loading device; starting a double-cylinder injection pump to inject fluid into each wellbore, and collecting pressure data of the first pressure sensor and the second pressure sensor through a pressure monitoring and data acquisition system; and calculating the stress state at any position in the target rock sample based on the pressure data.

[0009] In one possible embodiment, a cubic rock sample is sealed to obtain a treated rock sample, including: coating each surface of the cubic rock sample with high-strength epoxy resin glue; allowing the cubic rock sample coated with the high-strength epoxy resin glue to stand for a preset time to allow the high-strength epoxy resin glue to solidify; wrapping the cubic rock sample solidified with the high-strength epoxy resin glue with a polyolefin film, and placing the polyolefin film in a hot oven to shrink the polyolefin film; and cooling the polyolefin film after shrinking to obtain the treated rock sample.

[0010] In one possible embodiment, the dual-cylinder injection pump is started to inject fluid into each wellbore, and the pressure data of the first pressure sensor and the second pressure sensor are collected through the pressure monitoring and data acquisition system, including: setting the first injection pressure of the first simulation well and the first injection flow rate of the second simulation well through the dual-cylinder injection pump; injecting fluid into the first simulation well and the second simulation well through the dual-cylinder injection pump; at the moment when the target rock sample breaks, recording the instantaneous pressure fluctuation value collected by the first pressure sensor; setting the second injection flow rate of the first simulation well through the dual-cylinder injection pump, and injecting fluid into the first simulation well and the second simulation well through the dual-cylinder injection pump until the target rock sample breaks again.

[0011] In one possible embodiment, calculating the stress state at any location within a target rock sample based on pressure data includes: collecting a current pressure value of a first pressure sensor and determining the pressure value as a current fluid pressure within a fracture; calculating the frictional pressure of the target rock sample based on a pressure decay curve of a dual-cylinder injection pump, wherein the pressure decay curve is acquired by a pressure monitoring and data acquisition system after the dual-cylinder injection pump is stopped; calculating the net pressure of the fluid within the compressed fracture based on the current fluid pressure within the fracture, the frictional pressure, and a preset minimum horizontal principal stress; measuring the length and height of a main fracture formed after the target rock sample is re-fractured; establishing a three-dimensional coordinate system with the center of the main fracture as the origin, the direction of the maximum horizontal principal stress as the x-axis, the direction of the minimum horizontal principal stress as the y-axis, and the direction of the vertical principal stress as the z-axis; calculating the three-dimensional induced stress component at any location in the three-dimensional coordinate system based on the net fluid pressure within the compressed fracture, the length of the main fracture, and the height of the main fracture; and correcting the three-dimensional induced stress component at any location based on an instantaneous pressure fluctuation value to obtain the actual stress magnitude at any location.

[0012] In one possible implementation, the three-dimensional induced stress component at any location is corrected based on the instantaneous pressure fluctuation value, including: calculating the difference between the instantaneous pressure fluctuation value and the friction pressure to determine the inter-well stress interference intensity; calculating the difference between the three-dimensional induced stress component and the inter-well stress interference intensity, and determining the absolute value of the difference as a correction coefficient; if the difference between the three-dimensional induced stress component and the inter-well stress interference intensity is greater than or equal to 0, then the actual stress magnitude at any location is the difference between the three-dimensional induced stress component and the correction coefficient; if the difference between the three-dimensional induced stress component and the inter-well stress interference intensity is less than 0, then the actual stress magnitude at any location is the sum of the three-dimensional induced stress component and the correction coefficient.

[0013] In one possible implementation, the formula for calculating the three-dimensional induced stress component at any location is:

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020] Where, σ cxx represents the stress component in the x-axis direction at any position; σ czz represents the stress component in the z-axis direction at any position; σ cyy represents the stress component in the y-axis direction at any position; σ cxz represents the stress component at any position in the xz plane; σ cxy represents the stress component at any position in the xy plane; σ cyz represents the stress component at any position in the yz plane; R represents the distance from any position to the origin of the three-dimensional coordinate system; R1 represents the distance from any position to the positive end point of the crack length; R2 represents the distance from any position to the negative end point of the crack length; r1 represents the distance from any position to the negative end point of the crack height; r2 represents the distance from any position to the positive end point of the crack height; θ represents the angle between R and the positive direction of the x-axis; θ1 represents the angle between R1 and the positive direction of the x-axis; θ2 represents the angle between R2 and the positive direction of the x-axis; α represents the angle between R and the negative direction of the z-axis; α1 represents the angle between r1 and the negative direction of the z-axis; α2 represents the angle between r2 and the negative direction of the z-axis; H represents the crack height; L represents the crack length; p net represents the net pressure of the fluid in the compressed fracture; v represents the Poisson's ratio of the target rock sample.

[0021] In one possible implementation, the formula for calculating the net pressure of the fluid in the compressed seam is:

[0022]

[0023] Where p net Indicates the net pressure of the fluid in the compressed seam; p f Indicates the current fluid pressure in the crack; p b Indicates the preset minimum horizontal principal stress; p s Indicates friction pressure.

[0024] The multi-well true triaxial hydraulic fracturing outlet pressure plate, stress interference monitoring experimental device and method provided in the embodiments of the present application meet the needs of multi-well true triaxial hydraulic fracturing experiments by adopting a split design for the multi-well true triaxial hydraulic fracturing outlet pressure plate at the core chamber outlet. The split structure of the metal slider and the rectangular groove can be freely adjusted and positioned according to the wellbore layout, solving the problem of the fixed wellbore position of the traditional integral pressure plate. In addition, the rock sample is sealed with high strength without changing the overall size of the cubic rock sample, which more realistically restores the fluid changes during the actual on-site fracturing process. By constructing a three-dimensional induced stress model in stress interference monitoring and combining it with a dynamic correction mechanism for pressure fluctuations to quantify the stress interference effect between wells, the problem of insufficient spatial resolution caused by local discrete points in traditional monitoring methods is solved, and the consistency between the experimental results and the actual fracturing conditions is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0026] Figure 1 A schematic diagram of the structure of the multi-well true triaxial hydraulic fracturing outlet pressure plate provided in this application;

[0027] Figure 2 A schematic diagram of the structure of a stress interference monitoring experimental device provided in an embodiment of the present application;

[0028] Figure 3 A schematic flow chart of the stress interference monitoring experimental method provided in an embodiment of the present application.

[0029] Reference numerals:

[0030] 100-pressure plate body; 200-metal slider; 101-mounting hole; 102-rectangular groove; 103-hole groove; 104-fixing hole; 201-matching hole; 202-fixing groove; 301-core chamber; 302-bearing device; 303-three-axis stress loading device; 304-injection system; 305-pressure monitoring and data acquisition system; 306-multi-well true triaxial hydraulic fracturing outlet pressure plate; 303a-hydraulic cylinder; 304a-dual-cylinder injection pump; 304b-first fracturing fluid container; 304c-second fracturing fluid container; 304d-first pressure sensor; 304e-second pressure sensor.

[0031] The above drawings illustrate specific embodiments of the present application, which will be described in more detail below. These drawings and the textual description are not intended to limit the scope of the present application in any way, but rather to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0032] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

[0033] In order to clearly understand the technical solution of the present application, the solution of the prior art is first introduced in detail. With the continuous growth of global energy demand, the efficient exploitation of oil and gas resources has become an important issue in the energy industry. Among them, hydraulic fracturing technology has been widely used because it can effectively increase the output of oil and gas wells. Fracturing interference in the hydraulic fracturing process refers to the pressure change and crack expansion caused by the injection of liquid. Studies in recent years have shown that fracturing interference not only affects the output of a single well, but may also cause pressure interference between wells, and even cause unpredictable changes in the formation. At present, indoor hydraulic fracturing experiments are an effective means to study the expansion of fracturing cracks. However, in indoor experiments of multi-crack or multi-well fracturing, the problem of inter-well interference cannot be effectively monitored, and thus the problem of quantifying the stress field changes at different positions inside the real rock sample cannot be solved.

[0034] In order to solve the above technical problems, the inventors thought of realizing independent sealing control of multiple wellbores by designing a modular multi-well true triaxial hydraulic fracturing outlet pressure plate, and setting a penetrating rectangular groove on the pressure plate body of the multi-well true triaxial hydraulic fracturing outlet pressure plate. The width of the rectangular groove matches the width of the metal slider to form an independent sealing unit for each wellbore. The multi-well true triaxial hydraulic fracturing outlet pressure plate is integrated into a stress interference monitoring experimental device, and the formation stress field is simulated by a three-dimensional stress loading device. The dual-cylinder injection pump and pressure sensor are used to realize independent monitoring of the injection pressure of each wellbore, thereby constructing an experimental system that can quantify inter-well stress interference, solving the problem that the current indoor hydraulic fracturing experiment cannot monitor inter-well interference.

[0035] The following specific embodiments describe in detail the technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0036] Figure 1 The schematic diagram of the structure of the multi-well true triaxial hydraulic fracturing outlet pressure plate provided in this application is as follows: Figure 1 As shown, the multi-well true triaxial hydraulic fracturing outlet pressure plate includes: a pressure plate body 100 and a plurality of metal sliders 200.

[0037] The four corners of the pressure plate body 100 are respectively provided with mounting holes 101 , which are used to fix the inner surface of the pressure plate body 100 to the core chamber of the stress interference monitoring experimental device.

[0038] Specifically, the mounting holes 101 are countersunk, allowing the heads of the fastening bolts to completely sink into the inner surface of the pressure plate body. This ensures a smooth, protruding contact surface between the pressure plate body and the core chamber when installed. The depth of the countersunk hole matches the height of the bolt head. For example, an M10 bolt corresponds to a hole depth of 6mm. The flatness error of the inner surface of the pressure plate after bolt tightening is controlled within ±0.03mm using a CNC lathe. The diagonal distance tolerance of the four mounting holes 101 is controlled within ±0.03mm, and a jig boring machine is used to ensure that the perpendicularity between the hole axis and the mounting surface is ≤0.1mm.

[0039] A rectangular groove 102 is provided in the central area of ​​the outside of the pressure plate body 100. The length of the rectangular groove 102 is equal to the length of the pressure plate body 100 and passes through the pressure plate body 100. The width of the rectangular groove 102 is equal to the sum of the widths of multiple metal sliders 200. The height of the rectangular groove 102 is equal to the height of each metal slider 200.

[0040] Specifically, the inner surface of the pressure plate body 100 is fixed to the core chamber of the stress interference monitoring experimental device. A rectangular groove 102 is provided in the center of the outer surface. The length of the rectangular groove 102 is equal to the entire length of the pressure plate body and runs through the entire pressure plate body 100. The width of the rectangular groove 102 is designed to be the sum of the widths of the multiple metal sliders 200. The height of the rectangular groove 102 is consistent with the height of the metal sliders 200. After the metal sliders 200 are embedded, the height difference between the outer surface and the outer plane of the pressure plate body 100 is ≤0.03mm, forming a continuous and flat pressure-bearing surface.

[0041] A plurality of through slots 103 are provided in the rectangular groove 102 , and fixing holes 104 are symmetrically provided on both sides of each slot 103 .

[0042] Specifically, rectangular groove 102 is provided with multiple through-hole slots 103, whose diameters are adapted to the outer diameter of the wellbore. For example, a 10mm outer diameter corresponds to a 12mm diameter for the slots 103, with a 2mm buffer gap reserved to ensure smooth insertion of the wellbore. Fixing holes 104 are symmetrically arranged on either side of each slot 103. These holes are machined using a CNC drilling and tapping machine to achieve 6H-grade thread precision, with a hole pitch tolerance of ±0.2mm. A thread plug gauge and vernier caliper are used for dual verification to ensure coaxiality of the bolted connection with the fixing slot 202 of ≤0.1mm.

[0043] In this embodiment, a plurality of through holes 103 are arranged in parallel along the width direction of the rectangular groove 102 .

[0044] Specifically, a plurality of through slots 103 are arranged in parallel along the width direction of the rectangular slot 102. The slots 103 are arranged parallel to the width direction of the rectangular slot 102, so that the wellbores are distributed in a transverse array at the core chamber outlet.

[0045] A matching hole 201 is formed in the center of each metal slider 200 , and fixing grooves 202 are symmetrically provided on both sides of the matching hole 201 .

[0046] Specifically, a matching hole 201 is provided in the central area of ​​each metal slider 200, and its inner diameter is designed to be an interference fit with the outer diameter of the wellbore, wherein the interference is set according to the pressure level: 0.02mm for ≤30MPa and 0.05mm for 30-50MPa. An annular sealing groove is provided on the inner wall of the matching hole 201 to accommodate a nitrile rubber O-ring. Fixed grooves 202 are symmetrically distributed on both sides of the matching hole 201. The fixed grooves 202 are long strips and are adapted to the fixed holes 104 on the pressure plate body 100. After the metal slider 200 is installed in the rectangular groove 102, the metal slider 200 is fixed to the pressure plate body 100 by installing fasteners such as screws at the corresponding positions of the fixing holes 104 and the fixing grooves 202.

[0047] The matching hole 201 is used to connect to the wellbore in the core chamber passing through the hole groove 103 , and the fixing groove 202 is used to fix the metal slider 200 to the fixing hole 104 of the rectangular groove 102 .

[0048] Specifically, the matching hole 201 is connected to the hole groove 103 in the rectangular groove 102 of the pressure plate body 100, and is coaxially adapted to the wellbore through which the core chamber passes to construct a fluid channel for fracturing fluid injection. The fixing groove 202 utilizes the coordinated cooperation with the fixing hole 104 on the rectangular groove 102 to achieve the limitation of the metal slider 200 on the pressure plate body 100 with the help of fasteners.

[0049] The above-described embodiment demonstrates that the split design of the multi-well true triaxial hydraulic fracturing outlet pressure plate at the core chamber outlet addresses the needs of multi-well true triaxial hydraulic fracturing experiments. The split structure of the metal slider and rectangular groove allows for flexible adjustment and positioning based on the wellbore layout, resolving the wellbore positional issues associated with traditional integral pressure plates. Furthermore, once embedded, the metal slider aligns with the outer plane of the pressure plate body, forming a continuous, flat pressure-bearing surface that avoids stress concentration in the rock sample caused by high-pressure loading during the experiment.

[0050] Figure 2 A schematic diagram of the structure of the stress interference monitoring experimental device provided in the embodiment of the present application is shown as follows: Figure 2 As shown, the stress interference monitoring experimental device includes: a core chamber 301, a bearing device 302, a three-axis stress loading device 303, an injection system 304, a pressure monitoring and data acquisition system 305, and the multi-well true triaxial hydraulic fracturing outlet pressure plate 306 in the above embodiment.

[0051] The core chamber is located in the carrying device and is used to place the target rock sample.

[0052] A left pressure plate is provided on the outer side of the left side of the core chamber, an upper pressure plate is provided on the outer side of the upper side of the core chamber, a lower pressure plate is provided on the outer side of the lower side of the core chamber, a front pressure plate is provided on the outer side of the front side of the core chamber, and a rear pressure plate is provided on the outer side of the rear side of the core chamber.

[0053] Specifically, the core chamber 301, located within the support device 302, is welded from high-strength metal, with its inner walls treated for rust prevention. It is used to secure the target rock sample. The six outer sides of the core chamber 301 are fitted with the left, upper, lower, front, and rear pressure plates, as well as the multi-well true triaxial hydraulic fracturing outlet pressure plate 306. This creates a closed pressure-bearing space for the rock sample, ensuring uniform stress on the target rock sample and preventing fluid leakage during the experiment.

[0054] The multi-well true triaxial hydraulic fracturing outlet pressure plate is located outside the outlet of the core chamber.

[0055] Specifically, the multi-well true triaxial hydraulic fracturing outlet pressure plate 306 is installed outside the core chamber outlet. Its main plate body 100 is secured to the core chamber via countersunk mounting holes 101 at its four corners. Multiple metal sliders 200 are embedded within the outer rectangular grooves 102. The mating hole 201 of each metal slider has an interference fit with the wellbore through the hole slot 103 and is sealed with an O-ring. The fixing slot 202 is bolted to the fixing hole 104.

[0056] Specifically, the supporting device 302 is a frame structure, made of H-shaped steel or rectangular steel pipes, with shock-absorbing supports such as rubber pads installed at the bottom. Its internal space dimensions are designed according to the specifications of the core chamber to provide rigid support for the core chamber.

[0057] The three-dimensional stress loading device includes hydraulic cylinders respectively arranged on the outer sides of the upper pressure plate, the left pressure plate and the front pressure plate, and is used to apply three-dimensional stress to the target rock sample.

[0058] Specifically, the three-dimensional stress loading device 303 comprises hydraulic cylinders 303a mounted on the outside of the upper, left, and front pressure plates. Powered by a hydraulic station, these cylinders independently adjust the stress values ​​of the upper, left, and front pressure plates. Force sensors are positioned between the hydraulic cylinder piston rods and the pressure plates to monitor the loading force in real time, simulating the three-dimensional ground stress state of the formation.

[0059] The injection system includes a dual-cylinder injection pump 304a, a first fracturing fluid container 304b, a second fracturing fluid container 304c, a first pressure sensor 304d and a second pressure sensor 304e; the dual-cylinder injection pump 304a is connected to the first fracturing fluid container 304b and the second fracturing fluid container 304c respectively through fracturing pipelines, and the first fracturing fluid container 304b is connected to the wellbore of the first simulated well pre-buried in the target rock sample through the first injection pipeline; the second fracturing fluid container 304c is connected to the wellbore of the second simulated well pre-buried in the target rock sample through the second injection pipeline.

[0060] The first pressure sensor 304d is located on the first liquid injection line, and the second pressure sensor 304e is located on the second liquid injection line.

[0061] Specifically, the injection system 304 utilizes a dual-cylinder injection pump 304a, connected to a first fracturing fluid container 304b and a second fracturing fluid container 304c via fracturing lines. This allows for independent control of the injection flow and pressure of the two fracturing fluids. The first and second injection lines are pre-buried within the target rock sample and connect to the wellbores of the first and second simulated wells, respectively, enabling synchronous or asynchronous injection of multiple wells, simulating cluster well fracturing operations. The fracturing lines utilize high-pressure rubber hoses with a pressure resistance of 60 MPa.

[0062] The pressure monitoring and data acquisition system is connected to the first pressure sensor 304d, the second pressure sensor and the dual-cylinder injection pump 304a, and is used to collect and process pressure data.

[0063] Specifically, the pressure monitoring and data acquisition system 305 is connected to the first pressure sensor 304d, the second pressure sensor 304e and the control module of the dual-cylinder injection pump 304a through a data line, and collects data such as injection pressure and pump displacement in real time at a sampling frequency of 100Hz, and performs signal processing, curve drawing and data storage through dedicated software.

[0064] The above examples demonstrate that the rectangular grooves of the outlet pressure plate of a multi-well true triaxial hydraulic fracturing system are arranged with parallel slots. Each metal slider independently seals its corresponding wellbore. Combined with the injection system's dual-cylinder injection pump and independent pressure sensors, the injection pressure and displacement of the fracturing fluid in each well can be controlled synchronously or asynchronously. A three-dimensional stress loading device applies adjustable three-dimensional stress to the rock sample via hydraulic cylinders, simulating formation principal stress differences. Combined with the stress concentration control structure of the outlet pressure plate of a multi-well true triaxial hydraulic fracturing system, surface stress fluctuations in the rock sample are kept within 5%, ensuring the authenticity of inter-well stress interference. This stress interference monitoring experimental device, through modular design and precise control, achieves realistic simulation of inter-well interference during multi-well fracturing.

[0065] Figure 3 Schematic diagram of the process of stress interference monitoring experimental method provided in the embodiment of the present application. The stress interference monitoring experimental method adopts the stress interference monitoring experimental device of the above embodiment, such as Figure 3 As shown, the method includes:

[0066] S301: taking a cubic rock sample for a stress interference monitoring experiment, performing a sealing treatment on the cubic rock sample, and obtaining a treated rock sample.

[0067] Specifically, a cubic rock sample that meets the experimental requirements is selected and sealed. The sealing treatment includes:

[0068] Sa1: Coat each surface of the cubic rock sample with high-strength epoxy resin glue.

[0069] Specifically, each surface of the cubic rock sample was roughened with 80-grit sandpaper, and then wiped with acetone to remove dust and oil stains. Bisphenol A epoxy resin and polyamide curing agent were mixed in a weight ratio of 2:1, and 10% silica powder was added. The six surfaces of the rock sample were evenly coated with a scraper. The coating thickness was 0.3-0.5mm, and the edges and corners were repainted with a brush.

[0070] Sa2: The cubic rock sample coated with high-strength epoxy resin glue is left to stand for a preset time to allow the high-strength epoxy resin glue to solidify.

[0071] Specifically, the coated rock samples were placed in an environment with a temperature of 25±2°C and a humidity of ≤60% for 48 hours, flipping them every 12 hours to ensure uniform stress on all surfaces. After curing, the adhesive layer was tested using a Shore durometer to achieve a hardness of 60-70 Shore D, and a pull-out test verified a bond strength of ≥15MPa.

[0072] Sa3: A cubic rock sample solidified with high-strength epoxy resin glue was wrapped with polyolefin film and placed in a hot oven to shrink the polyolefin film.

[0073] Specifically, a 0.1mm thick polyolefin film was cut to wrap the rock sample, and the seam was sealed with a hot melt gun and placed in a hot air circulation oven. The temperature was raised to 120°C at 5°C / min and kept warm for 30 minutes. The 15-20% shrinkage rate of the film was used to form a radial constraint force of 0.1-0.2MPa on the rock sample to eliminate the micro gaps in the adhesive layer.

[0074] Sa4: After the polyolefin film shrinks, it is cooled to obtain the treated rock sample.

[0075] Specifically, after heat preservation, the oven is closed and the rock sample is allowed to cool naturally to room temperature at a rate of ≤10℃ / h. The rock sample is placed in a -0.09MPa environment for 30 minutes using the vacuum leak detection method to observe bubbles with a diameter of ≤1mm and a number of ≤3, or the weight change in 24 hours is confirmed by weighing method to be ≤0.1%. The treated rock sample is obtained to ensure that the permeability of the treated rock sample is ≤1×10⁻¹ 5 m².

[0076] S302: Drill two simulation wells at preset positions on the processed rock sample, run a wellbore into each simulation well and perform cementing treatment to obtain target rock samples.

[0077] Specifically, two simulated wells were drilled on the rock sample using a CNC drill press at a preset well spacing, with a verticality error of ≤0.5°. A stainless steel wellbore was then lowered, with a 15° bevel angle machined into the bottom to avoid damaging the rock sample. Cement slurry or high-strength resin was used for cementing, followed by a 48-hour post-cementing curing period. Acoustic logging was used to verify cementing quality, ensuring a bond strength of ≥20 MPa between the wellbore and the rock sample.

[0078] S303: Place the target rock sample into the core chamber, and seal the outlet of the core chamber using a multi-well true triaxial hydraulic fracturing outlet pressure plate.

[0079] Specifically, the target rock sample is placed in the center of the core chamber, and pressure plates are installed on the six sides of the core chamber. The multi-well true triaxial hydraulic fracturing outlet pressure plate is fixed to the core chamber outlet through the mounting holes at the four corners. A metal slider is embedded in the rectangular groove, which involves first passing the wellbore through the hole groove, and then inserting the metal slider into the wellbore through the matching hole, and fixing it with bolts through the fixing groove and the fixing hole. After installation, an air pressure test is performed to ensure sealing.

[0080] S304: Connect each wellbore to the injection system through an injection pipeline.

[0081] Specifically, high-pressure hoses were used to connect the wellbore to the injection system: the first simulated well was connected to the first fracturing fluid container via the first injection line, and the second simulated well was connected to the second fracturing fluid container via the second injection line. Metal-sealed joints were used at the pipeline connections, and the airtightness was tested with soapy water to ensure that no bubbles were generated. Pressure sensors were installed in series with the injection lines, ≤100 mm from the rock sample inlet.

[0082] S305: Apply triaxial stress to the target rock sample through a triaxial stress loading device.

[0083] Specifically, the three-axis stress loading device was activated, applying stress in stages via the upper, left, and front hydraulic cylinders: first, the confining pressure was applied to the target value, then the vertical stress was applied to the set value. The loading rate was controlled at 0.5 MPa / min. After reaching the target value, the pressure was maintained for 30 minutes to stabilize the stress state of the rock sample. During the stress loading process, force sensors were used to monitor the stress in real time, ensuring that the three-axis stress deviation was ≤±0.3 MPa.

[0084] S306: Start the dual-cylinder injection pump to inject fluid into each wellbore, and collect pressure data from the first pressure sensor and the second pressure sensor through the pressure monitoring and data acquisition system.

[0085] Specifically, the dual-cylinder injection pumps are started, and fluid is injected simultaneously into the two wellbores at a preset displacement. The injection pressure is gradually increased until the rock sample fractures. The first and second pressure sensors collect pressure data at a frequency of 100Hz. The data acquisition system records the pressure-time curve in real time, automatically marking the fracture pressure and extension pressure. This process includes:

[0086] Sb1: Set the first injection pressure of the first simulation well and the first injection flow rate of the second simulation well through the double-cylinder injection pump.

[0087] Specifically, the first injection pressure of the first simulation well and the first injection flow rate of the second simulation well are independently set through the control system of the double-cylinder injection pump.

[0088] Sb2: Inject fluid into the first simulation well and the second simulation well through a double-cylinder injection pump.

[0089] Specifically, the dual-cylinder injection pump was started to inject fluid into the two simulated wells synchronously. The first pressure sensor and the second pressure sensor collected injection pressure data in real time at a frequency of 100 Hz. The data acquisition system synchronously recorded the pressure-time curve and pump displacement parameters.

[0090] Sb3: At the moment the target rock sample breaks, record the instantaneous pressure fluctuation value collected by the first pressure sensor.

[0091] Specifically, when the target rock sample reaches the fracture pressure (a sudden drop in the curve), the system automatically marks the fracture moment and records the instantaneous pressure fluctuation value of the first pressure sensor. The instantaneous pressure fluctuation value represents the stress interference at the bottom of the first simulation well during the fracturing process of the second simulation well.

[0092] Sb4: Set the second injection flow rate of the first simulation well by the double-cylinder injection pump, and inject fluid into the first simulation well and the second simulation well by the double-cylinder injection pump until the target rock sample is broken again.

[0093] Specifically, the double-cylinder injection pump is adjusted to change the flow rate of the first simulation well to the second injection flow rate, the flow rate of the second simulation well is kept unchanged, and the injection into the two wells is continued until the rock sample breaks again.

[0094] S307: Calculate the stress state at any position in the target rock sample based on the pressure data.

[0095] Specifically, a three-dimensional stress model of the rock sample is established using the injection pressure of each wellbore and the three-dimensional loading stress as boundary conditions to calculate the magnitude and direction of the principal stress at any location. This process includes:

[0096] Sc1: Collect the current pressure value of the first pressure sensor and determine the pressure value as the current fluid pressure in the slit.

[0097] Specifically, the current pressure value of the first pressure sensor is collected in real time by the pressure monitoring and data acquisition system, and is directly determined as the current fluid pressure in the slit.

[0098] Sc2: Calculate the friction pressure of the target rock sample based on the pressure decay curve of the dual-cylinder injection pump. The pressure decay curve is collected by the pressure monitoring and data acquisition system after the dual-cylinder injection pump stops pumping.

[0099] Specifically, after the dual-cylinder injection pump stops pumping, the pressure decay curve of the dual-cylinder injection pump is collected using the pressure monitoring and data acquisition system, and the friction pressure of the target rock sample is calculated based on the curve. The formula for fitting the pressure decay curve using the exponential decay model is:

[0100]

[0101] Where, P t It represents the pressure value at time t after the pump is stopped; P0 represents the pressure at the moment the pump is stopped; k represents the attenuation coefficient, P res Indicates residual pressure.

[0102] Specifically, the friction pressure is the difference between the instantaneous pressure when the pump stops and the residual pressure.

[0103] Sc3: Calculate the net pressure of the fluid in the compressed fracture based on the current fracture fluid pressure, friction pressure and the preset minimum horizontal principal stress.

[0104] The net pressure of the fluid in the fracture reflects the effective pressure of the fracturing fluid to promote the expansion of the fracture after overcoming the friction resistance and the minimum horizontal principal stress in the fracture.

[0105] Specifically, based on the current fluid pressure, friction pressure, and the preset minimum horizontal principal stress in the fracture, the formula for calculating the net pressure of the fluid in the compressed fracture is:

[0106]

[0107] Where, P net Indicates the net pressure of the fluid in the compressed seam, P f Indicates the current fluid pressure in the crack, P b Indicates the preset minimum horizontal principal stress, P s Indicates friction pressure.

[0108] Sc4: Measure the length and height of the main fracture formed after the target rock sample breaks again.

[0109] Specifically, after the target rock sample fractures again, the length and height of the main fracture formed are measured using equipment such as an ultrasonic flaw detector or a 3D laser scanner. The center of the main fracture is used as the reference point, and the fracture length is measured along the direction of maximum horizontal principal stress, while the fracture height is measured vertically.

[0110] Sc5: Establish a three-dimensional coordinate system with the center of the main seam as the origin, the direction of the maximum horizontal principal stress as the x-axis, the direction of the minimum horizontal principal stress as the y-axis, and the direction of the vertical principal stress as the z-axis.

[0111] Specifically, a three-dimensional coordinate system is established with the center of the main seam as the origin, the direction of the maximum horizontal principal stress as the x-axis, the direction of the minimum horizontal principal stress as the y-axis, and the direction of the vertical principal stress as the z-axis.

[0112] Sc6: In a three-dimensional coordinate system, calculate the three-dimensional induced stress components at any location based on the net pressure of the fluid in the compressed fracture, the length and height of the main fracture.

[0113] Specifically, in the established three-dimensional coordinate system, the formula for calculating the three-dimensional induced stress component at any position is as follows based on the net pressure of the fluid in the compressed fracture, the length of the main fracture, and the fracture height:

[0114]

[0115]

[0116]

[0117]

[0118]

[0119]

[0120] Where, σ cxx represents the stress component in the x-axis direction at any position; σ czz represents the stress component in the z-axis direction at any position; σ cyy represents the stress component in the y-axis direction at any position; σ cxz represents the stress component at any position in the xz plane; σ cxy represents the stress component at any position in the xy plane; σ cyz represents the stress component at any position in the yz plane; R represents the distance from any position to the origin of the three-dimensional coordinate system; R1 represents the distance from any position to the positive end point of the crack length; R2 represents the distance from any position to the negative end point of the crack length; r1 represents the distance from any position to the negative end point of the crack height; r2 represents the distance from any position to the positive end point of the crack height; θ represents the angle between R and the positive direction of the x-axis; θ1 represents the angle between R1 and the positive direction of the x-axis; θ2 represents the angle between R2 and the positive direction of the x-axis; α represents the angle between R and the negative direction of the z-axis; α1 represents the angle between r1 and the negative direction of the z-axis; α2 represents the angle between r2 and the negative direction of the z-axis; H represents the crack height; L represents the crack length; p net represents the net pressure of the fluid in the compressed fracture; v represents the Poisson's ratio of the target rock sample.

[0121] Sc7: According to the instantaneous pressure fluctuation value, the three-dimensional induced stress component at any position is corrected to obtain the actual stress magnitude at any position.

[0122] Specifically, the pressure fluctuation value reflects the sudden change of stress at the moment of rupture. By superimposing the stress increment caused by the pressure fluctuation on the induced stress component, the induced stress can be corrected. Specifically, the correction method includes:

[0123] Sd1: Calculate the difference between the instantaneous pressure fluctuation value and the friction pressure to determine the inter-well stress interference intensity.

[0124] Specifically, the pressure fluctuation at the moment of rock sample failure, obtained through the pressure monitoring system, is subtracted from the friction pressure calculated after pumping is stopped to obtain the interwell stress interference intensity. This value eliminates the influence of fluid flow resistance and quantifies the degree of stress interference caused by fluid injection from adjacent wells on the fracture propagation of the target well during multi-well fracturing.

[0125] Sd2: Calculate the difference between the three-dimensional induced stress component and the interwell stress interference intensity, and determine the absolute value of the difference as the correction coefficient.

[0126] Specifically, the three-dimensional induced stress component is subtracted from the interwell stress interference intensity, and the absolute value of the difference is taken as the correction coefficient. This coefficient is used to quantify the degree of deviation between the theoretical induced stress calculation value and the actual stress interference effect.

[0127] Sd3: If the difference between the three-dimensional induced stress component and the interwell stress interference intensity is greater than or equal to 0, the actual stress at any position is the difference between the three-dimensional induced stress component and the correction coefficient.

[0128] Specifically, when the difference between the 3D induced stress component and the interwell stress interference intensity is greater than or equal to 0, the actual stress is the induced stress component minus the correction factor. This applies to areas far from the fracture center, where the induced stress dominates. Deducting the deviation makes the calculated result closer to the actual stress state.

[0129] Sd4: If the difference between the three-dimensional induced stress component and the interwell stress interference intensity is less than 0, the actual stress at any position is the sum of the three-dimensional induced stress component and the correction coefficient.

[0130] Specifically, when the difference between the 3D induced stress component and the interwell stress interference intensity is less than 0, the actual stress magnitude is the induced stress component plus a correction factor. This applies to the near-fracture region, where pressure fluctuations at the moment of rupture can induce significant dynamic stress increments, requiring the addition of a correction factor to compensate for the inadequacy of the induced stress calculation.

[0131] It can be seen from the above embodiments that by sealing the cubic rock sample, the rock sample is sealed with high strength without changing the overall size of the cubic rock sample, ensuring that it is always in a closed boundary state during the stress interference monitoring experiment. Even if the fracturing cracks extend to the rock surface, the fracturing fluid in the cracks will not be lost from the cracks, thereby losing the fluid pressure in the cracks. This more realistically restores the fluid changes during the actual on-site fracturing over a long period of time, and ensures precision and accuracy for monitoring stress interference and inter-well crosstalk within the rock sample.

[0132] In addition, by constructing a three-dimensional induced stress model in stress interference monitoring and combining it with a dynamic correction mechanism for pressure fluctuations, the inter-well stress interference effect is quantified, which solves the problem of insufficient spatial resolution caused by local discrete points in traditional monitoring methods. This enables real-time inversion of the stress state at any position in the rock sample, effectively improving the consistency between the experimental results and actual fracturing conditions.

[0133] In the above embodiments, the description of each embodiment has its own emphasis. For parts not described in detail in a particular embodiment, please refer to the relevant description of other embodiments. The technical features of the above embodiments can be combined in any way. To keep the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0134] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present application that follow the general principles of the present application and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

[0135] It should be understood that the present application is not limited to the exact structure described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A multi-well true triaxial hydraulic fracturing outlet pressure plate, characterized in that: include: A pressure plate body (100) and a plurality of metal sliders (200); The four corners of the pressure plate body (100) are respectively provided with mounting holes (101), and the mounting holes (101) are used to fix the inner surface of the pressure plate body (100) to the core chamber of the stress interference monitoring experimental device; A rectangular groove (102) is provided in the central area of ​​the outer surface of the pressure plate body (100), wherein the length of the rectangular groove (102) is equal to the length of the pressure plate body (100) and passes through the pressure plate body (100), the width of the rectangular groove (102) is equal to the sum of the widths of the plurality of metal sliders (200), and the height of the rectangular groove (102) is equal to the height of each metal slider (200); A plurality of through-hole slots (103) are provided in the rectangular groove (102), and fixing holes (104) are symmetrically provided on both sides of each hole slot (103); A matching hole (201) is provided in the central area of ​​each metal slider (200), and fixing grooves (202) are symmetrically provided on both sides of the matching hole (201); The matching hole (201) is used to connect to the wellbore in the core chamber passing through the hole groove (103), and the fixing groove (202) is used to fix the metal slider (200) to the fixing hole (104) of the rectangular groove (102).

2. The multi-well true triaxial hydraulic fracturing outlet pressure plate according to claim 1, characterized in that: The plurality of through holes (103) are arranged in parallel along the width direction of the rectangular groove (102).

3. A stress interference monitoring experimental device, characterized in that: include: A core chamber, a bearing device, a three-dimensional stress loading device, a fluid injection system, a pressure monitoring and data acquisition system, and a multi-well true triaxial hydraulic fracturing outlet pressure plate according to any one of claims 1 to 2; The core chamber is located in the carrying device and is used to place the target rock sample; A left pressure plate is provided on the outer side of the left side of the core chamber, an upper pressure plate is provided on the outer side of the upper side of the core chamber, a lower pressure plate is provided on the outer side of the lower side of the core chamber, a front pressure plate is provided on the outer side of the front side of the core chamber, and a rear pressure plate is provided on the outer side of the rear side of the core chamber; The multi-well true triaxial hydraulic fracturing outlet pressure plate is located outside the outlet of the core chamber; The three-dimensional stress loading device includes hydraulic cylinders respectively arranged on the outer sides of the upper pressure plate, the left pressure plate and the front pressure plate, and is used to apply three-dimensional stress to the target rock sample; The injection system includes a dual-cylinder injection pump, a first fracturing fluid container, a second fracturing fluid container, a first pressure sensor, and a second pressure sensor; the dual-cylinder injection pump is connected to the first fracturing fluid container and the second fracturing fluid container respectively through fracturing pipelines, the first fracturing fluid container is connected to the wellbore of a first simulated well pre-buried in the target rock sample through a first injection pipeline; the second fracturing fluid container is connected to the wellbore of a second simulated well pre-buried in the target rock sample through a second injection pipeline; The first pressure sensor is located on the first liquid injection pipeline, and the second pressure sensor is located on the second liquid injection pipeline; The pressure monitoring and data acquisition system is connected to the first pressure sensor, the second pressure sensor and the double-cylinder injection pump, and is used to collect and process pressure data.

4. A stress interference monitoring experimental method, characterized in that: The stress interference monitoring experimental device according to claim 3 comprises: Taking a cubic rock sample for a stress interference monitoring experiment, and performing a sealing treatment on the cubic rock sample to obtain a treated rock sample; Drilling two simulated wells at preset positions on the treated rock sample, and running a wellbore into each simulated well to perform cementing treatment to obtain a target rock sample; The target rock sample is placed in the core chamber, and the outlet of the core chamber is sealed using the multi-well true triaxial hydraulic fracturing outlet pressure plate; Connecting each wellbore to the injection system via an injection pipeline; Applying triaxial stress to the target rock sample by the triaxial stress loading device; Starting the dual-cylinder injection pump to inject fluid into each wellbore, and collecting pressure data of the first pressure sensor and the second pressure sensor through the pressure monitoring and data acquisition system; The stress state at any position in the target rock sample is calculated based on the pressure data.

5. The method according to claim 4, characterized in that The sealing treatment of the cubic rock sample to obtain the treated rock sample comprises: Each surface of the cubic rock sample is coated with high-strength epoxy resin glue; The cubic rock sample coated with the high-strength epoxy resin glue is left to stand for a preset time to allow the high-strength epoxy resin glue to solidify; Wrapping the cubic rock sample solidified with the high-strength epoxy resin adhesive with a polyolefin film, and placing the sample in a hot oven to shrink the polyolefin film; The polyolefin film is cooled after shrinking to obtain the treated rock sample.

6. The method according to claim 4, characterized in that The step of starting the dual-cylinder injection pump to inject fluid into each wellbore and collecting pressure data of the first pressure sensor and the second pressure sensor through the pressure monitoring and data acquisition system includes: Setting a first injection pressure of the first simulation well and a first injection flow rate of the second simulation well by the double-cylinder injection pump; injecting liquid into the first simulated well and the second simulated well by the double-cylinder injection pump; At the moment when the target rock sample breaks, recording the instantaneous pressure fluctuation value collected by the first pressure sensor; The second injection flow rate of the first simulation well is set by the double-cylinder injection pump, and the double-cylinder injection pump is used to inject liquid into the first simulation well and the second simulation well until the target rock sample is broken again.

7. The method according to claim 6, characterized in that Calculating the stress state at any position in the target rock sample based on the pressure data includes: collecting a current pressure value of the first pressure sensor and determining the pressure value as the current fluid pressure in the slit; Calculating the frictional pressure of the target rock sample according to a pressure decay curve of the dual-cylinder injection pump, wherein the pressure decay curve is acquired through a pressure monitoring and data acquisition system after the dual-cylinder injection pump is stopped; Calculating the net pressure of the fluid in the compressed fracture according to the current fracture fluid pressure, the friction pressure and the preset minimum horizontal principal stress; measuring the length and height of the main fracture formed after the target rock sample is fractured again; A three-dimensional coordinate system is established with the center of the main seam as the origin, the direction of the maximum horizontal principal stress as the x-axis, the direction of the minimum horizontal principal stress as the y-axis, and the direction of the vertical principal stress as the z-axis; In the three-dimensional coordinate system, the three-dimensional induced stress component at any position is calculated based on the net pressure of the fluid in the compressed seam, the seam length and the seam height of the main seam; According to the instantaneous pressure fluctuation value, the three-dimensional induced stress component at any position is corrected to obtain the actual stress magnitude at any position.

8. The method according to claim 7, characterized in that The correcting of the three-dimensional induced stress component at any position according to the instantaneous pressure fluctuation value includes: Calculating the difference between the instantaneous pressure fluctuation value and the friction pressure to determine the interwell stress interference intensity; calculating a difference between the three-dimensional induced stress component and the interwell stress interference intensity, and determining an absolute value of the difference as a correction coefficient; If the difference between the three-dimensional induced stress component and the inter-well stress interference intensity is greater than or equal to 0, then the actual stress magnitude at any position is the difference between the three-dimensional induced stress component and the correction coefficient; If the difference between the three-dimensional induced stress component and the inter-well stress interference intensity is less than 0, the actual stress magnitude at any position is the sum of the three-dimensional induced stress component and the correction coefficient.

9. The method according to claim 7, characterized in that The formula for calculating the three-dimensional induced stress component at any position is: Where σ cxx represents the stress component at any position in the x-axis direction; σ czz represents the stress component in the z-axis direction at any position; σ cyy represents the stress component in the y-axis direction at any position; σ cxz represents the stress component at any position in the xz plane; σ cxy represents the stress component at any position in the xy plane; σ cyz represents the stress component of any position in the yz plane; R represents the distance from any position to the origin of the three-dimensional coordinate system, R1 represents the distance from any position to the positive end point of the slit length; R2 represents the distance from any position to the negative end point of the slit length; r1 represents the distance from any position to the negative end point of the slit height; r2 represents the distance from any position to the positive end point of the slit height; θ represents the angle between R and the positive direction of the x-axis; θ1 represents the angle between R1 and the positive direction of the x-axis; θ2 represents the angle between R2 and the positive direction of the x-axis; α represents the angle between R and the negative direction of the z-axis; α1 represents the angle between r1 and the negative direction of the z-axis; α2 represents the angle between r2 and the negative direction of the z-axis; H represents the slit height; L represents the slit length; p net represents the net pressure of the fluid in the compressed fracture; v represents the Poisson's ratio of the target rock sample.

10. The method according to claim 7, characterized in that The formula for calculating the net pressure of the fluid in the compressed seam is: Where p net represents the net pressure of the fluid in the compressed seam; p f represents the current fluid pressure in the seam; p b represents the preset minimum horizontal principal stress; p s represents the friction pressure.

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