A method for optimizing and adjusting multi-fracture synchronous perforation interval based on injection flow dynamic monitoring

Abstract

The application discloses a kind of based on injection flow dynamic monitoring's multiple cracks synchronous perforation interval optimization adjustment method, including rock sample test piece, high temperature-high pressure flow monitoring meter, data acquisition etc..Method includes the following steps: setting temperature, confining pressure and injection flow rate;Record perforation interval;Record analysis multiple crack propagation path;Establish the relationship between crack propagation path and injection parameter;Determine the optimal perforation interval under certain temperature, pressure, injection flow rate.The optimization adjustment method of the application can obtain the multiple crack synchronous cracking propagation law of rock mass under THM coupling state on the basis of specific test research, fundamentally reveal the synchronous cracking propagation control mechanism of rock mass multiple crack from "non-equilibrium" to "equilibrium" transformation under stress shadow effect, and the determination of best perforation interval in specific engineering practice can not only greatly improve coalbed gas production, realize safe and efficient exploitation of coalbed gas, but also greatly reduce the investment of early cost.

Description

Technical Field

[0001] This invention relates to the field of perforation fracturing technology for coalbed methane extraction, and in particular to a method for optimizing and adjusting the synchronous perforation spacing of multiple fractures based on dynamic monitoring of injection flow rate. Background Technology

[0002] The current stage is one of rapid growth in my country's energy demand. Coalbed methane (CBM), as a clean energy source in the primary energy consumption structure, can not only fill some of the current energy gap but also reduce the greenhouse effect caused by the direct release of CBM into the atmosphere during coal mining operations (the greenhouse effect of CBM is 21 times that of carbon dioxide). Current measures to increase CBM production mainly include horizontal well fracturing and multi-cluster perforation fracturing. The existing problems include:

[0003] Firstly, during multi-cluster perforation fracturing, the uneven development of multiple fractures prevents the reservoir from being fully modified, which can lead to the failure of some fracturing perforations within the cluster, resulting in wasted costs.

[0004] Secondly, since some dominant fractures have obtained the vast majority of fracturing fluid, their development is at risk of getting out of control. Excessively long fractures may connect with adjacent fracturing wells, causing serious inter-well interference and leading to reduced production in neighboring wells.

[0005] Therefore, to achieve "balanced" fracture development during multi-fracture fracturing, save fracturing costs, and improve coalbed methane extraction rates, physical experiments are needed to study the influence of perforation spacing on the synchronous propagation of multiple fractures in fracturing sample rock masses, and to determine the optimal perforation spacing under certain injection parameters. However, in actual multi-fracture synchronous initiation fracturing experiments (taking 3-hole fracturing as an example), the influence of different perforation spacings leads to stress shadow interference between the synchronously initiated and propagating fractures in the rock mass, affecting the propagation effect of the fracturing fractures. In practical engineering applications, this will ultimately affect the coalbed methane extraction effect. Summary of the Invention

[0006] To address the aforementioned problems, this invention aims to provide a method for optimizing the perforation spacing in multi-fracture synchronous fracturing based on dynamic monitoring of injection flow rate. This method dynamically monitors the injection flow rate of different perforations under simultaneous multi-fracture initiation and fracturing, determining the optimal perforation spacing under specific injection flow rate parameters by observing the actual fracture propagation morphology. The flow monitoring equipment can monitor the injection pressure, flow rate, and temperature in each perforation in real time. Based on this, the perforation spacing optimization method of this application, in practical engineering, can significantly improve coalbed methane production, achieving safe and efficient coalbed methane extraction, and greatly reducing initial investment costs.

[0007] To achieve the above objectives, the technical solution adopted by this invention is as follows: A method for optimizing and adjusting the synchronous perforation spacing of multiple fractures based on dynamic monitoring of injection flow rate, comprising rock sample specimens, a high-temperature-high-pressure flow meter, a data acquisition and fracturing fluid injection control system, characterized in that the method includes the following steps:

[0008] S1. Fix the prepared rock sample specimen on a true triaxial press and place it in the fracturing chamber. Connect each of the multiple perforations in the fracturing wellbore to a high-temperature-high-pressure flow meter and connect it to the data acquisition and fracturing fluid injection control system.

[0009] S2. Set the test temperature, confining pressure, and injection flow rate. Apply stress and temperature to the predetermined values ​​step by step using a true triaxial press and stabilize the pressure.

[0010] S3. After the temperature and pressure stabilize, simultaneously turn on the high-temperature-high-pressure flow monitoring meter and the hydraulic fracturing system. Conduct hydraulic fracturing experiments on multiple fractures in the rock mass with different perforation spacings within the cluster at a constant injection rate. During the experiment, determine the evolution law of injection pressure, the propagation path of multiple fractures and the deflection distance. When fracturing fluid is observed on the surface of the rock sample, end the experiment, replace the sample and repeat the experiment.

[0011] Furthermore, the plurality of perforations have a first perforation position at the center of the rock sample specimen. Based on the initial crack formed, the spacing between adjacent perforations is gradually increased on both sides to determine the critical spacing at which the crack can change direction, which is the optimal perforation spacing for specimen fracturing.

[0012] Furthermore, the repeated experiments also include gradually increasing the test temperature, confining pressure, and injection flow rate, recording the readings of the flow monitoring meter for each fracturing hole at different hole spacings, establishing a relationship with the multi-fracture propagation path, analyzing the synchronous fracture initiation and propagation control mechanism of the transformation from "non-equilibrium" to "equilibrium" under the stress shadow effect during multi-fracture propagation, obtaining the optimal perforation spacing that can achieve the best fracturing effect under this temperature, confining pressure, and injection rate, and determining the specific test parameters.

[0013] Furthermore, the interference between the perforations under different temperatures, confining pressures, and injection rates was recorded to determine the stress shadow range and the optimal perforation spacing.

[0014] The beneficial effects of this invention are as follows: The optimization and adjustment method disclosed in this application can, based on specific experimental research, derive the synchronous initiation and propagation law of multiple fractures in rock mass under THM coupling state. Through a high-temperature-high-pressure flow meter, the relationship between the injection flow parameters and dynamic distribution law of each fracturing hole and the fracture propagation morphology can be qualitatively analyzed. This fundamentally reveals the synchronous initiation and propagation control mechanism of multiple fractures in rock mass under stress shadow effect, transforming from "non-equilibrium" to "equilibrium" under multiple factors. The optimal perforation spacing under certain injection parameter conditions can be determined, providing guidance for engineering practice under specific conditions. In specific engineering practice, determining the optimal perforation spacing can not only greatly improve coalbed methane production and achieve safe and efficient coalbed methane extraction, but also significantly reduce initial investment costs. Attached Figure Description

[0015] Figure 1 This is a structural diagram of a conventional flow meter according to the present invention.

[0016] Figure 2 This is a diagram of the physical monitoring model of the conventional flow meter of the present invention for the synchronous expansion of multiple cracks.

[0017] Figure 3 This is a schematic diagram of the high-temperature-high-pressure flow monitoring meter of the present invention.

[0018] Figure 4 This is a diagram of the internal structure of the high-temperature-high-pressure flow meter of the present invention.

[0019] Figure 5 This is a physical illustration of the high-temperature-high-pressure flow monitoring meter of the present invention.

[0020] Figure 6 This is a diagram of the multi-crack synchronous perforation fluid injection system of the present invention.

[0021] Figure 7 This is a flowchart of the method for optimizing and adjusting the spacing of synchronous perforations in multiple cracks according to the present invention.

[0022] Figure 8 The diagram illustrates the crack initiation and propagation patterns of porous hydraulic fracturing under different crack spacing conditions according to the present invention.

[0023] Figure 9 This is a dynamic percentage diagram of the injection flow rate of each specimen under different fracturing hole spacing conditions according to the present invention.

[0024] Figure 10 This represents the percentage of total fluid injection flow rate in the fracturing holes on the left, right, and center of different specimens in this invention.

[0025] Figure 1 In the middle: 1-1—Two-way valve 1; 1-2—Pressure sensor; 1-3—Flow rate sensor; 1-4—Two-way valve 2; 1-5—Block switch;

[0026] Figure 2 In the middle section: 2-1—Fracturing specimen; 2-2—Two-way connector; 2-3—Four-way connector; 2-4—One-way valve; 2-5—Sealing adhesive (epoxy resin); 2-6—Filling material (salt, etc.); 2-7—Fracturing hole; 2-8—Flow meter; 2-9—Fracturing tube; 2-10—Pressure gauge; 2-11—Data acquisition and fracturing fluid injection control system;

[0027] Figure 3 In the middle: 3-1—Two-way valve 1; 3-2—Sensor device; 3-3—Electronic display screen; 3-4—Cut-off switch; 3-5—Two-way connector; 3-6—Two-way valve 2;

[0028] Figure 4 In the middle: 1-Data acquisition unit; 2-Axial telescopic rod; 3-Vernier caliper; 4-Two-way single-pass valve; 5-One-way double-pass valve; 6-Linked piston rod; 7-Miniature data display; 8-High-pressure sealed vessel; 9-Fluid cavity; 10-Vernier caliper fixing clamp; 11-14 Switches;

[0029] Figure 6 In the middle section: 2-1—Fracturing specimen; 2-2—Two-way connector; 2-3—One-way valve; 2-4—Four-way connector; 2-5—Sealing adhesive (epoxy resin adhesive); 2-6—Filling material (salt, etc.); 2-7—Fracturing hole; 2-9—Fracturing tube; 2-10—Pressure gauge; 2-11—Data acquisition and fracturing fluid injection control system; 3-7—High temperature-high pressure dynamic flow meter. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0031] The existing optimal perforation spacing for simultaneous multi-fracture propagation is determined based on traditional flow meters and fracture propagation conditions. Traditional flow meters can monitor the flow rate of a single fracturing tube, performing well in single-hole fracturing, and can monitor the entire pipeline in multi-hole fracturing. The principle behind determining the optimal perforation spacing in multi-hole fracturing is to compare and analyze the flow parameters recorded in real time on the injection main pipeline based on the simultaneous propagation of multiple fractures. Furthermore, traditional flow meters can achieve real-time monitoring of the fracturing fluid velocity and pressure in the fracturing tube, forming a system such as... Figure 1 As shown in the figure. The physical monitoring model for the synchronous propagation of multiple cracks based on traditional flow meters is illustrated in the figure below. Figure 2 As shown.

[0032] The traditional flow meter works by injecting fracturing fluid through a fracturing pipe (10mm outer diameter, 6mm inner diameter) into the flow meter via a two-way valve 1-4. Valve 1-5 is a flow cut-off switch that can open or close the injection of fracturing fluid. Valves 1-2 and 1-3 are pressure and velocity sensors, respectively, which monitor the pressure and velocity of the fracturing fluid in real time and display the data on an electronic screen. The fracturing fluid then passes through a two-way valve 1-1 to the main fracturing pipeline of the specimen to be fracturing. During three-hole fracturing of a 300×300×300mm specimen, the flow meter can provide real-time information on the fracturing fluid velocity and pressure in the main fracturing pipeline and the branch pipelines within each fracturing hole.

[0033] The fracturing monitoring system works by injecting fracturing fluid with constant pressure, flow rate, and temperature into the fracturing tube 2-9 through the fracturing fluid injection control system 2-11. The pressure gauge 2-10 ensures that the outlet fracturing fluid pressure is within a safe range. The fracturing tube 2-9 is connected to the inlet end of the flow meter 2-8, and the outlet end is connected to the fracturing tube extending from the three fracturing holes 2-7 (diameter 10.5 mm, hole depth 170 mm) of the specimen 2-1 to be fractured through the four-way connector 2-3.

[0034] To prevent the sealing adhesive (7102 epoxy resin) from clogging the fracturing tube opening during fracturing hole sealing, the fracturing hole is filled with a filler material such as salt before sealing. Test specimen 2-1 is subjected to fracturing under a triaxial servo loading system. The fracture propagation caused by fracturing is correlated with the injection parameters recorded by the flow meter. By changing the injection parameters, the fracture development is adjusted from "non-equilibrium" to "equilibrium," thus determining the optimal injection parameters for achieving the optimal perforation spacing under multi-hole fracturing.

[0035] However, this technical solution can only monitor the injection parameters of the main fracturing pipe, and cannot monitor the injection parameters of each fracturing hole in real time, nor reveal the interaction between the injection parameters and the fracture development of each fracturing hole. Furthermore, the flow meter performs poorly at high temperatures and cannot achieve real-time monitoring of injection parameters under THM (temperature-stress-fluid velocity) coupling, meaning it cannot perform accurate qualitative analysis of fracture propagation under multi-phase coupling effects at each fracturing hole. Consequently, it cannot reveal the range of stress shadow interference between fractures under THM coupling effects, and cannot truly determine the optimal perforation spacing.

[0036] Traditional flowmeters are suitable for fracturing experiments involving single-fracture initiation and propagation. They can monitor fluid pressure and velocity within the fracturing tube, meeting the requirements for single-hole fracturing tests. However, considering the THM (temperature-stress-fluid velocity) coupling effect in deep formations, temperature control, especially high-temperature monitoring, is also crucial, which traditional flowmeters cannot handle. Traditional flowmeters have poor high-temperature resistance and are designed for high-flow-rate measurements, but they are not suitable for high-pressure conditions. They are primarily designed for low-flow-rate measurements (0-100 mL), and there are no flowmeters capable of handling extremely low flow rates under high temperatures and pressures.

[0037] For experimental research on multi-fracture initiation and propagation, i.e., multi-hole fracturing, the stress shadow effect during fracturing can affect the synchronous initiation and propagation of multiple fractures. In order to determine the most reasonable perforation spacing under certain temperature, pressure and flow rate of fracturing fluid, it is necessary to monitor the temperature, flow rate and pressure of fracturing fluid in different boreholes in real time. This is something that traditional flow meters cannot meet. Traditional ones are for low pressure ranges, are basically not pressure resistant, and measure very large values. However, the flow meter used in this application is for measuring under extremely low flow conditions and has a high temperature and high pressure resistant measuring device. Therefore, it is necessary to study the flow distribution law in each fracturing hole under multi-hole fracturing and optimize and adjust the technical solution to achieve the optimal perforation spacing based on this.

[0038] Technical solution of this application

[0039] To reveal the synchronous initiation and propagation patterns of multiple fractures in hydraulic fracturing under different cluster perforation spacings, and to uncover the inter-fracture stress shadow range under THM coupling, thus determining the optimal perforation spacing, a method for optimizing and adjusting the synchronous perforation spacing of multiple fractures based on dynamic monitoring of injection flow rate is proposed. This method utilizes a high-temperature-high-pressure flow meter.

[0040] Test apparatus

[0041] The experiment used a large-size true triaxial fracturing flow simulation device of type TCHFSM-I. Since the fracturing device is not the main content of this invention, it will not be described. The main content is flow monitoring and perforation spacing optimization adjustment method.

[0042] The composition of a high-temperature-high-pressure flow meter is as follows: Figure 3 As shown, the principle is as follows: the fracturing fluid is connected to the fracturing pipe through the two-way connector 3-5, and then introduced into the two-way valve 3-6. Afterwards, it flows through a high-precision temperature and flow rate sensor and a high-frequency pressure sensor device. This sensor device can achieve accurate monitoring under high temperature and high pressure. The pressure, temperature, and flow rate data of the fracturing fluid are displayed in real time on the electronic display screen 3-3. Finally, the fracturing fluid flows out through the two-way valve 3-1 and exits the high-temperature and high-pressure flow meter.

[0043] according to Figure 4 The internal structure of the high-temperature-high-pressure flow meter is shown in the diagram. Its working principle is as follows: It monitors the liquid injection status of the high-temperature-high-pressure flow meter (the solution volume in the flow meter chamber is 100mL; liquid is injected into the fluid cavity 9 externally, driving the linkage piston 6 to move up and down, which is then displayed and recorded by the micro data display 7), thereby monitoring the injection flow rate in each fracture. Operating procedure: Turn on switches 13 and 12, and turn off switches 11 and 14. An external double-cylinder pump injects water into the flow meter through switch 12, driving the linkage piston rod 6 downwards (the main flow rate returns to zero). The water in the chamber is discharged through switch 13, thus completing the water storage in the flow meter. During fracturing tests, turn off switches 12 and 13, and turn on switches 11 and 14. Switch 14 connects to a double-cylinder water injection pump, and switch 11 connects to the specimen fracturing tube. The water injection pump injects water into the flow meter through switch 14, driving the piston upwards, thereby monitoring the injection flow rate.

[0044] Multi-fracture synchronous perforation injection system based on dynamic monitoring of injection flow rate using a high-temperature-high-pressure flow meter, such as... Figure 6 As shown, the principle is as follows: fracturing fluid with constant pressure, flow rate, and temperature is injected into the fracturing tube through the fracturing fluid injection control system 2-11. The pressure gauge 2-10 ensures that the outlet fracturing fluid pressure is within a safe range. The fracturing tube 2-9 is connected to the two-way connector at the inlet end of the high-temperature-high-pressure flow meter. The outlet end of the high-temperature-high-pressure flow meter is connected to the inlet ends of three high-temperature-high-pressure flow meters arranged on the fracturing tubes extending from the three fracturing holes through the four-way connector 2-4. The outlet ends of the three high-temperature-high-pressure flow meters are connected to the fracturing tubes on the fracturing holes through two-way valves. The subsequent arrangement is the same as in the prior art and will not be described again.

[0045] Technical solution

[0046] Experimental conditions: The experimental temperature was set at 40℃, which could be provided by the heating rods integrated into the true triaxial fracturing and seepage simulation device. This heating device could achieve a maximum heating temperature of 150℃ with precise temperature control of ±1℃. The true triaxial stress state was used to simulate the triaxial stress conditions of the rock mass in the formation. Axial pressure (σV) and horizontal stress (σH, σh) were constantly applied to the specimen using five servo-controlled high-precision hydraulic cylinders with a loading accuracy of 0.01 kN / s. The experimental stress state ranged from 25 to 45 MPa.

[0047] Experimental Design and Procedure: Table 1 shows the experimental design for hydraulic fracturing of large-size rock masses with multiple fractures under different perforation spacings within clusters. The prepared rock sample specimens were fixed on a true triaxial press and placed inside the fracturing chamber. Each of the three perforations in the fracturing wellbore was independently connected to a high-temperature-high-pressure flow meter, which was then connected to the data acquisition and fracturing fluid injection control system. Subsequently, the true triaxial press applied stress and temperature progressively to predetermined values ​​and maintained the pressure.

[0048]

[0049] Table 1 Experimental schemes for hydraulic fracturing of large-sized coal and rock masses with multiple fractures under different perforation spacing within clusters.

[0050] Finally, after the temperature and pressure stabilized, the high-temperature-high-pressure flow meter and the hydraulic fracturing system were simultaneously activated. Multi-fracture hydraulic fracturing experiments were conducted in the rock mass with different perforation spacings within clusters at a constant injection rate of 30 mL / min. During the experiment, the evolution of injection pressure, the propagation path of multiple fractures, and the deflection distance were measured. The experiment was terminated when fracturing fluid (clear water) was observed on the surface of the specimen. The sample was then replaced, and the experiment was repeated.

[0051] Method for optimizing and adjusting the perforation spacing

[0052] During the synchronous initiation and propagation of multiple cracks, the newly generated cracks alter the initial stress distribution, causing the crack propagation direction to deviate from the initial maximum principal stress direction, resulting in stress shadowing. Therefore, the perforation spacing has a certain influence on inter-crack interference during crack propagation; as the perforation spacing increases, the inter-crack interference gradually weakens.

[0053] The first perforation location is assumed to be the center of the specimen. Based on the initial fracture, the critical spacing at which the fracture can change direction is determined by continuously increasing the perforation spacing; this is the optimal perforation spacing for specimen fracturing. In practical engineering, the optimal perforation spacing needs to be determined within the critical spacing range, taking into account both the logging interpretation of the horizontal well section and the cementing quality.

[0054] Under conditions of 40℃, confining pressures of 30MPa, 35MPa, and 25MPa, and an injection rate of 30mL / min, the number of perforations within the cluster was 3, and the perforation spacing within the cluster gradually increased from 10mm to 60mm in increments of 5mm. The readings (temperature, pressure, and flow rate) of the flowmeter for each fracturing hole were observed and recorded at different perforation spacings, and their relationship with the multi-fracture propagation path was established. The synchronous fracturing initiation and propagation control mechanism, which transforms from "non-equilibrium" to "equilibrium" under the stress shadow effect during multi-fracture propagation, was analyzed. The optimal perforation spacing that achieves the best fracturing effect under these temperature, confining pressure, and injection rate was determined, and specific experimental parameters were identified. Figure 8 The crack initiation and propagation characteristics of porous hydraulic fracturing under different crack spacing conditions are shown.

[0055] Dynamic evolution characteristics of injection flow rate under different fracture morphologies

[0056] Figure 9 The figure shows the dynamic evolution of the percentage of real-time injection flow rate in the right, left, and middle fracturing holes under different fracturing hole spacing conditions. Figure 10The figure shows the percentage of total fluid injection flow rate in the fracturing holes on the left, right, and middle sides of each specimen.

[0057] from Figure 9 , 10 It can be seen that when the fracture spacing between the fracturing holes is relatively close, the injection flow rate of the outer fracturing holes on the left and right sides is relatively large, while the injection flow rate of the fracturing hole in the middle is extremely low. For example, 1 # 2 # 3 # The total injection volume percentages of the fracturing holes on the right side of specimen #4 were 49.86%, 48.94%, 41.51%, and 42.14%, respectively, while those on the left side were 41.63%, 45.68%, 49.54%, and 42.03%. The injection flow rate percentages of the fracturing holes in the middle were 8.51%, 5.38%, 8.95%, and 15.83% of the total injection flow rate. Overall, the injection flow rate percentages of the fracturing holes on the left and right sides gradually decreased, while the percentage of injection volume in the middle fracturing holes increased with the increase in the distance between the fracturing holes and the fractures. Therefore, based on the injection flow rate distribution of specimens #1 to #4, less injection was performed in the middle, resulting in a shorter fracture propagation distance, while more injection was performed in the fracturing holes on the left and right sides, resulting in a longer hydraulic fracturing fracture propagation path.

[0058] As the fracture spacing between the fracturing holes gradually increased (for specimens #5 to #10), the proportion of total injection volume in the right-side fracturing holes was 38.52%, 36.98%, 35.74%, 33.73%, 36.91%, and 36.26%, respectively, while the proportion in the left-side fracturing holes was 36.43%, 34.78%, 33.55%, 33.84%, 32.54%, and 33.79%, respectively. Meanwhile, the percentage of injection flow rate in the middle fracturing holes was 24.95%, 30.71%, 32.43%, 30.55%, and 29.95% of the total injection flow rate. The injection flow rates in the left and right fracturing holes gradually decreased, while the injection flow rate in the middle fracturing hole gradually increased, eventually reaching a balance among the three fracturing holes. Therefore, when the spacing between the fracturing holes increases to 60 mm or more, the injection flow rate in the three fracturing holes is basically the same, which helps the hydraulic fracturing fractures to develop uniformly and produce three independent fracturing fractures.

[0059] Based on the above research, it is evident that a small fracture spacing between fracturing holes typically leads to uneven fracture propagation in porous hydraulic fracturing. Furthermore, due to the uneven distribution of injection flow, only one or two main fractures are generated, significantly impacting reservoir stimulation volume. Closer fracture hole spacing results in additional stress exerted by external fracturing holes on internal ones, creating a stress shadowing effect around the central fracturing hole. This significantly affects the injection flow distribution within each fracturing hole, increasing flow resistance within the central fracture and causing fracturing fluid to migrate to the external fractures. Therefore, to maximize fracturing production, the fracture spacing between fracturing holes should be appropriately increased to reduce the impact of stress shadowing on fractures, effectively promoting the uniform extension and propagation of fractures in porous hydraulic fracturing.

[0060] Based on the above analysis steps, the inter-fracture interference under different temperatures, confining pressures, and injection rates can also be analyzed to study the stress shadow range and determine the optimal perforation spacing. The flowchart of the method for optimizing and adjusting the synchronous perforation spacing of multiple fractures based on dynamic monitoring of injection flow rate is shown below. Figure 7 As shown.

[0061] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for optimizing and adjusting the spacing of synchronous perforations in multiple fractures based on dynamic monitoring of injection flow rate, comprising rock sample specimens, a high-temperature-high-pressure flow meter, a data acquisition and fracturing fluid injection control system, characterized in that, The method includes the following steps: S1. Fix the prepared rock sample specimen on a true triaxial press and place it in the fracturing chamber. Connect each of the multiple perforations in the fracturing wellbore to a high-temperature-high-pressure flow meter and connect it to the data acquisition and fracturing fluid injection control system. S2. Set the test temperature, confining pressure, and injection flow rate. Apply stress and temperature to the predetermined values ​​step by step using a true triaxial press and stabilize the pressure. S3. After the temperature and pressure stabilize, the high-temperature-high-pressure flow meter and the hydraulic fracturing system are turned on simultaneously. The hydraulic fracturing experiment of multiple fractures in the rock mass under different perforation spacings within the cluster is carried out at a constant injection rate. During the experiment, the evolution law of injection pressure, the propagation path of multiple fractures and the deflection distance are measured. When the fracturing fluid is observed on the surface of the rock sample, the experiment is ended, the sample is replaced and the experiment is repeated. The plurality of perforations have a first perforation position at the center of the rock sample specimen. Based on the initial crack formed, the spacing between adjacent perforations is gradually increased on both sides to determine the critical spacing at which the crack can change direction, which is the optimal perforation spacing for specimen fracturing. The repeated experiments also included gradually increasing the test temperature, confining pressure, and injection flow rate, recording the readings of the flow monitoring meter for each fracturing hole at different hole spacings, establishing a relationship with the multi-fracture propagation path, analyzing the synchronous fracturing control mechanism of the transformation from "non-equilibrium" to "equilibrium" under the stress shadow effect during multi-fracture propagation, obtaining the optimal perforation spacing that can achieve the best fracturing effect under this temperature, confining pressure, and injection rate, and determining the specific test parameters; The interference between the perforations under different temperatures, confining pressures, and injection rates was recorded to determine the stress shadow range and the optimal perforation spacing.

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