A coal mine underground hydraulic fracturing method and hydraulic fracturing system

Abstract

The present application relates to a kind of coal mine underground hydraulic fracturing method, comprising: control fracturing pump is injected into the first fracturing fluid to the fracturing hole located in target coal seam;During the first fracturing fluid injection, the initial position of the crack of target coal seam is collected based on the microseismic sensor arranged in roadway surrounding rock;And, the crack is scanned based on the scanning probe arranged in target coal seam and generates the three-dimensional image of crack;Based on the three-dimensional image of crack, the deflection angle of crack is obtained;If the deflection angle of crack is greater than the preset crack deflection angle value, then control fracturing pump is injected into the second fracturing fluid smaller than the first fracturing fluid to the fracturing hole, to correct the deflection angle of crack.The present application can directly show the morphology of crack, dynamic guide correction crack direction;Crack deflection angle can be effectively corrected, so as to effectively inhibit the disorderly expansion and deflection degree of crack, reduce even avoid fracturing fluid into non-target rock layer and cause non-target rock layer damage.

Description

Technical Field

[0001] This invention relates to the field of hydraulic fracturing technology, and more specifically, to a hydraulic fracturing method and system for underground coal mines. Background Technology

[0002] Hydraulic fracturing technology in coal mines is a crucial measure for enhancing coal seam permeability, gas extraction, and preventing rockbursts. It primarily involves injecting fracturing fluid into the coal or rock strata using a high-pressure pump. When the pressure exceeds the tensile strength of the rock, fractures extend. Fracture monitoring and control are paramount. Current technologies typically employ surface potential methods for fracture monitoring, which only provide a general direction and extent of the fractures. Construction personnel must assess the effectiveness several hours after the operation through underground inspections or sample analysis. Therefore, real-time feedback on fracture morphology is impossible, hindering real-time control of fracture propagation direction. This can lead to uncontrolled fracturing fluid expansion and infiltration into non-target rock strata. Summary of the Invention

[0003] This invention provides a hydraulic fracturing method for underground coal mines, which solves the technical problem in the prior art that the inability to provide real-time feedback on fracture dynamics makes it impossible to control the direction of fracture propagation in real time, resulting in uncontrolled propagation of fracturing fluid and its infiltration into non-target rock formations.

[0004] This invention provides a method for hydraulic fracturing in coal mines, comprising: Control the fracturing pump to inject the first fracturing fluid into the fracturing hole located in the target coal seam; During the first fracturing fluid injection process, the initial position of the fracture in the target coal seam is acquired based on the microseismic sensor installed in the surrounding rock of the roadway; and the fracture is scanned based on the scanning probe installed in the target coal seam to generate a three-dimensional image of the fracture. Based on the three-dimensional image of the crack, the deflection angle of the crack is obtained; If the deflection angle of the fracture is greater than a preset fracture deflection angle value, the fracturing pump is controlled to inject a second fracturing fluid into the fracturing hole to correct the deflection angle of the fracture. The viscosity of the first fracturing fluid is less than that of the second fracturing fluid.

[0005] Furthermore, the hydraulic fracturing method further includes: If the corrected fracture deflection angle is less than or equal to the preset fracture deflection angle value, then the fracturing pump is controlled to inject the first fracturing fluid into the fracturing hole.

[0006] Furthermore, the fracturing orifice has at least two and is spaced apart; the outlet of the fracturing pump is connected to a fracturing pipeline, and the fracturing pipeline is equipped with at least two first control valves, which are used to connect or disconnect the fracturing pipeline from the fracturing orifice; The step of determining whether the deflection angle of the fracture is greater than a preset fracture deflection angle value, and then controlling the fracturing pump to inject a second fracturing fluid into the fracturing hole, includes: Based on the deflection angle of the crack, a first deflection region and a second deflection region of the crack are obtained, wherein the deflection angle of the crack in the first deflection region is greater than the preset crack deflection angle value and the preset crack deflection angle value is greater than the crack deflection angle in the second deflection region. If the first deflection region exists, the first control valves corresponding to the first deflection region and the second deflection region are closed to stop the injection of the first fracturing fluid into the fracturing hole. Open the first control valve corresponding to the first deflection area and keep the first control valve corresponding to the second deflection area closed, and control the fracturing pump to inject the second fracturing fluid into the fracturing hole corresponding to the first deflection area to correct the deflection angle of the fracture in the first deflection area.

[0007] Furthermore, after the step of controlling the fracturing pump to inject the second fracturing fluid into the fracturing hole corresponding to the first deflection region, the hydraulic fracturing method further includes: If the deflection angle of the fracture in the corrected first deflection region is less than or equal to the preset fracture deflection angle value, then the first control valve corresponding to the first deflection region and the first control valve corresponding to the second deflection region remain open, and the fracturing pump is controlled to inject the first fracturing fluid into the fracturing hole.

[0008] Furthermore, the inlet of the fracturing pump is connected to a storage tank, and the storage tank is equipped with a fluid viscosity sensor for monitoring the viscosity of the gel in the second fracturing fluid; The step of controlling the fracturing pump to inject the second fracturing fluid into the fracturing hole corresponding to the first deflection region further includes: determining if the viscosity of the gel fluctuates abnormally, and then adjusting the injection rate or injection ratio of the gel.

[0009] Furthermore, the step of determining whether the viscosity of the gel fluctuates abnormally, and then adjusting the injection rate or injection ratio of the gel, includes: If the ratio of the change in viscosity of the gel within a first time period to a preset viscosity value is greater than a preset viscosity ratio, then the injection rate or injection ratio of the gel is reduced; otherwise, the injection rate or injection ratio of the gel is increased. Alternatively, if the viscosity of the gel is greater than a preset viscosity value during the second time period, the injection rate or injection ratio of the gel is reduced; otherwise, the injection rate or injection ratio of the gel is increased.

[0010] Furthermore, the return port of the fracturing pump is connected to a flowback pipeline, which is equipped with a second control valve for connecting or disconnecting the return port of the fracturing pump from the flowback pipeline; the end of the flowback pipeline furthest from the return port of the fracturing pump is sequentially connected to a cyclone settler, a filter, a mineralization enhancement device, and a recovery liquid tank; the hydraulic fracturing method further includes: Based on the three-dimensional image of the fracture, if it is determined that the fracture extends beyond a preset target boundary, the second control valve is opened to connect the return port of the fracturing pump and the flowback pipeline. The first fracturing fluid or the second fracturing fluid flows into the recovery fluid tank sequentially through the fracturing pipeline, the return port of the fracturing pump, the flowback pipeline, the cyclone precipitator, the filter, and the mineralization enhancement device.

[0011] Furthermore, the hydraulic fracturing method further includes: Based on the three-dimensional image of the crack, if it is determined that the crack extends beyond a preset target boundary, the fracturing pump is controlled to inject a curing agent into the fracturing hole through the fracturing pipeline to seal the crack.

[0012] Furthermore, after the step of controlling the fracturing pump to inject a curing agent into the fracturing hole through the fracturing pipeline to seal the fracture, the hydraulic fracturing method further includes: The fracturing pump is controlled to inject the first fracturing fluid into the fracturing hole through the fracturing pipeline to enhance the bonding strength between the curing agent and the fracture.

[0013] Furthermore, the first fracturing fluid is water, and the second fracturing fluid is a mixture of gel and water.

[0014] This invention provides a method for hydraulic fracturing in coal mines, which has at least the following beneficial technical effects: On the one hand, through the coordinated monitoring of microseismic sensors and scanning probes, the initial position of the crack can be captured in real time and a three-dimensional image of the crack can be generated. Based on the three-dimensional image of the crack, the deflection angle of the crack can be obtained, and the shape of the crack can be displayed intuitively, which can dynamically guide the correction of the crack direction. On the other hand, based on the relationship between the deflection angle of the crack and the preset deflection angle value, if the deflection angle of the crack is greater than the preset deflection angle value, the fracturing pump is controlled to inject a second fracturing fluid with a viscosity higher than that of the first fracturing fluid into the fracturing hole. This can effectively correct the deflection angle of the crack, thereby effectively suppressing the disorderly propagation and deflection of the crack, and reducing or even avoiding the entry of fracturing fluid into non-target rock layers and causing damage to non-target rock layers.

[0015] The present invention also provides a hydraulic fracturing system that applies the above-described hydraulic fracturing method for underground coal mines, the hydraulic fracturing system comprising: A fracturing injection module is used to control the fracturing pump to inject the first fracturing fluid into the fracturing hole; The fracturing monitoring module includes a microseismic sensor and a scanning probe. The microseismic sensor is used to acquire the initial location of the fractures in the target coal seam; the scanning probe is used to scan the fractures and generate a three-dimensional image of the fractures. The fracturing control module is used to obtain the deflection angle of the fracture based on the three-dimensional image of the fracture; if the deflection angle of the fracture is greater than a preset deflection angle value, the module controls the fracturing pump to inject a second fracturing fluid into the fracturing hole to correct the deflection angle of the fracture.

[0016] The hydraulic fracturing system provided by this invention applies the above-described hydraulic fracturing method for underground coal mines and has all the advantages of the method, which will not be elaborated here. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a hydraulic fracturing system corresponding to a hydraulic fracturing method for underground coal mines provided in an embodiment of the present invention; Figure 2 A flowchart illustrating a hydraulic fracturing method for underground coal mines provided in this embodiment of the invention. Figure 1 ; Figure 3 A flowchart illustrating a hydraulic fracturing method for underground coal mines provided in this embodiment of the invention. Figure 2 ; Figure 4 A flowchart illustrating a hydraulic fracturing method for underground coal mines provided in this embodiment of the invention. Figure 3 ; Figure 5 This is a structural block diagram of a hydraulic fracturing system corresponding to a hydraulic fracturing method for underground coal mines provided in an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures: 1. Fracturing injection module; 2. Fracturing monitoring module; 3. Fracturing control module; 10. Storage tank; 110. Fluid viscosity sensor; 20. Fracturing pump; 210. Fracturing pipeline; 211. First control valve; 220. Return pipeline; 221. Second control valve; 30. Fracturing hole; 40. Scanning probe; 50. Micro-vibration sensor; 60. Swirl settler; 70. Filter; 80. Mineralization enhancement device; 90. Return tank; A. Target coal seam; B. Roadway surrounding rock. Detailed Implementation

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the following description is provided in conjunction with the accompanying drawings. Figure 1-5 Specific embodiments of the present invention will be described in detail below.

[0020] This invention provides a method for hydraulic fracturing in coal mines, see appendix. Figure 1 and Figure 2 The underground hydraulic fracturing method for this coal mine includes: S102, control the fracturing pump 20 to inject the first fracturing fluid into the fracturing hole 30 located in the target coal seam A; wherein, in this step, the first preset pressure of the injected first fracturing fluid is between 2-5 MPa; S104, during the first fracturing fluid injection process, the initial position of the crack in the target coal seam A is acquired based on the microseismic sensor 50 installed in the surrounding rock of the roadway B; and the crack is scanned based on the scanning probe 40 installed in the target coal seam A and a three-dimensional image of the crack is generated. S106, Based on the three-dimensional image of the crack, obtain the deflection angle of the crack; S108, if the fracture deflection angle is greater than the preset fracture deflection angle value, then control the fracturing pump 20 to inject the second fracturing fluid into the fracturing hole 30 to correct the fracture deflection angle; otherwise, continue to execute step S102, control the fracturing pump 20 to inject the first fracturing fluid into the fracturing hole 30 located in the target coal seam A; in this step, the preset fracture deflection angle value is between 10-30°; the first preset pressure of the injected first fracturing fluid is between 6-12MPa; The viscosity of the first fracturing fluid is lower than that of the second fracturing fluid. For example, the first fracturing fluid can be water; the second fracturing fluid can be a mixture of gel and water, wherein the gel has a preset concentration value, the preset concentration value being between 0.3% and 1.5%; preferably, the preset concentration value is between 0.5% and 1.5%; preferably, the gel can be an expanding polyacrylamide gel, with a water expansion rate of 200% to 300%, which can effectively fill fracture branches and promote fracture orientation adjustment.

[0021] The present invention provides a hydraulic fracturing method for underground coal mines. On the one hand, through the coordinated monitoring of a micro-vibration sensor 50 and a scanning probe 40, the initial position of the fracture can be captured in real time and a three-dimensional image of the fracture can be generated. Based on the three-dimensional image of the fracture, the deflection angle of the fracture can be obtained, and the morphology of the fracture can be intuitively displayed, which can dynamically guide the correction of the fracture direction. On the other hand, based on the relationship between the deflection angle of the fracture and a preset deflection angle value, if the deflection angle of the fracture is greater than the preset deflection angle value, the fracturing pump 20 is controlled to inject a second fracturing fluid with a viscosity higher than that of the first fracturing fluid into the fracturing hole 30. This can effectively correct the deflection angle of the fracture, thereby effectively suppressing the disorderly expansion and deflection of the fracture, and reducing or even avoiding the entry of fracturing fluid into non-target rock layers and causing damage to non-target rock layers.

[0022] In this embodiment of the invention, see appendix. Figure 2Before step S102, when the controlled fracturing pump 20 injects the first fracturing fluid into the fracturing hole 30 located in the target coal seam A, the hydraulic fracturing method further includes: S100, a micro-vibration sensor 50 is installed in the surrounding rock B of the roadway, and fracturing holes 30 and scanning probes 40 are arranged in the target coal seam A; it should be noted that there are multiple fracturing holes 30, and multiple scanning probes 40 are arranged around each fracturing hole 30. The arrangement of multiple scanning probes 40 can be in various ways, for example, multiple scanning probes 40 can be in a linear array; or, for example, multiple scanning probes 40 can be in a circular array.

[0023] In this embodiment of the invention, see appendix. Figure 2 Hydraulic fracturing methods also include: S110, if the corrected fracture deflection angle is less than or equal to the preset fracture deflection angle value, then control the fracturing pump 20 to inject the first fracturing fluid into the fracturing hole 30.

[0024] In this embodiment of the invention, see appendix. Figure 1 The fracturing orifice 30 has at least two holes spaced apart, for example, two, three, or other numbers. The outlet of the fracturing pump 20 is connected to a fracturing pipeline 210, which is equipped with at least two first control valves 211, for example, two, three, or other numbers. The number of first control valves 211 matches the number of fracturing orifices 30. The first control valves 211 are used to connect or disconnect the fracturing pipeline 210 from the fracturing orifices 30. The first control valve 211 is a pressure-sensitive flow valve, also known as a flow control valve, which is a control device that can automatically adjust the flow rate in the fracturing pipeline 210. The pressure-sensitive flow valve senses changes in flow rate and automatically adjusts the valve opening to achieve flow control. Specifically, when the flow rate in the fracturing pipeline 210 changes, the sensor in the pressure-sensitive flow valve detects this change and controls the valve opening to adjust the flow rate, thereby maintaining a stable flow rate in the fracturing pipeline 210.

[0025] See appendix Figure 3 The step S108, which determines whether the fracture deflection angle is greater than the preset fracture deflection angle value, involves controlling the fracturing pump 20 to inject the second fracturing fluid into the fracturing hole 30. S1081, Based on the deflection angle of the crack, obtain the first deflection region and the second deflection region of the crack, wherein the deflection angle of the crack in the first deflection region is greater than a preset crack deflection angle value and the preset crack deflection angle value is greater than the crack deflection angle in the second deflection region. S1082, if it is determined that a first deflection region exists, then control the closure of the first control valves 211 corresponding to the first deflection region and the second deflection region respectively, and stop injecting the first fracturing fluid into the fracturing hole 30. S1083, open the first control valve 211 corresponding to the first deflection area and keep the first control valve 211 corresponding to the second deflection area closed, and control the fracturing pump 20 to inject the second fracturing fluid into the fracturing hole 30 corresponding to the first deflection area to correct the deflection angle of the fracture in the first deflection area.

[0026] The hydraulic fracturing method for coal mines provided in this invention involves controlling and real-time detection of fracture deflection angles to obtain a first deflection region. If a first deflection region exists, all control valves are closed, and the injection of first fracturing fluid into the fracturing hole 30 is stopped. Then, the control valve corresponding to the first deflection region is opened while the control valve corresponding to the second deflection region remains closed. A second fracturing fluid with a viscosity greater than that of the first fracturing fluid is injected into the fracturing hole 30 of the first deflection region to increase the fluid pressure in the first deflection region. This controls the asymmetric stress field to force a reduction in the deflection angle of the fracture in the first deflection region, and utilizes the local support effect of the high-viscosity second fracturing fluid to suppress the propagation of the fracture in the first deflection region. Simultaneously, the control valve for the second deflection region remains closed, ensuring that the deflection angle of the fracture in the second deflection region remains stable.

[0027] In this embodiment of the invention, see appendix. Figure 3 After step S1083, where the fracturing pump 20 injects the second fracturing fluid into the fracturing hole 30 corresponding to the first deflection region, the hydraulic fracturing method further includes: S1084, if it is determined that the deflection angle of the fracture in the corrected first deflection region is less than or equal to the preset fracture deflection angle value, then the first control valve 211 corresponding to the first deflection region and the first control valve 211 corresponding to the second deflection region remain open, and the fracturing pump 20 is controlled to inject the first fracturing fluid into the fracturing hole 30. With this setting, when the deflection angle of the fracture in the first deflection region is corrected to be less than or equal to the preset fracture deflection angle value, the system switches to injecting low-viscosity first fracturing fluid into the fracturing hole 30. The low-viscosity first fracturing fluid can reduce the pressure loss within the fracture, promoting the fracture to extend and prolong to a greater distance.

[0028] In this embodiment of the invention, see appendix. Figure 1 The inlet of the fracturing pump 20 is connected to a storage tank 10, and a fluid viscosity sensor 110 is installed in the storage tank 10 to monitor the viscosity of the gel in the second fracturing fluid. The step S1083, which involves controlling the fracturing pump 20 to inject the second fracturing fluid into the fracturing hole 30 corresponding to the first deflection region, further includes: if the viscosity of the gel fluctuates abnormally, adjusting the injection rate or injection ratio of the gel. This setting avoids fracture deflection caused by the instability of the second fracturing fluid, thereby suppressing disorderly fracture propagation.

[0029] In this embodiment of the invention, abnormal fluctuations in the viscosity of the gel may include short-term fluctuations or continuous deviations; specifically as follows: For example, the determination in step S1083 that if the viscosity of the gel fluctuates abnormally, adjusting the injection rate or injection ratio of the gel includes: if the ratio of the change in viscosity of the gel within a first time period to a preset viscosity value is greater than a preset viscosity ratio, then the injection rate or injection ratio of the gel is decreased; conversely, the injection rate or injection ratio of the gel is increased. The preset viscosity ratio ranges from -10% to 10%.

[0030] For example, the determination in step S1083 that if the viscosity of the gel fluctuates abnormally, adjusting the injection rate or injection ratio of the gel includes: if the viscosity of the gel is greater than a preset viscosity value within a second time period, then reducing the injection rate or injection ratio of the gel; conversely, increasing the injection rate or injection ratio of the gel. The preset viscosity value is between 50 and 200 mPa·s.

[0031] In this embodiment of the invention, see appendix. Figure 1 The return port of the fracturing pump 20 is connected to a return pipeline 220. The return pipeline 220 is equipped with a second control valve 221, which is used to connect or disconnect the return port of the fracturing pump 20 from the return pipeline 220. At the end of the return pipeline 220 furthest from the return port of the fracturing pump 20, a cyclone precipitator 60, a filter 70, a mineralization enhancement device 80, and a recovery fluid tank are connected in sequence. (See attached diagram) Figure 4 Hydraulic fracturing methods also include: S112, based on the three-dimensional image of the fracture, if it is determined that the fracture extends beyond the preset target boundary, the second control valve 221 is opened to connect the return port of the fracturing pump 20 and the return pipeline 220. The first or second fracturing fluid flows sequentially through the fracturing pipeline 210, the return port of the fracturing pump 20, the return pipeline 220, the cyclone settler 60, the filter 70, and the mineralization enhancement device 80 into the recovery tank. This setup establishes a closed-loop hydraulic circulation system, including a three-stage treatment system of cyclone settler, nanofiltration membrane, and mineralization enhancement device 80, enabling the recovery of the first or second fracturing fluid. The recovered fluid can be directly used for subsequent fracturing, reducing the cost of the first or second fracturing fluid and significantly improving its resource utilization efficiency.

[0032] In this embodiment of the invention, see appendix. Figure 4 Hydraulic fracturing methods also include: S114, based on the three-dimensional image of the crack, if it is determined that the crack has extended beyond the preset target boundary, the fracturing pump 20 is controlled to inject a curing agent into the fracturing hole 30 through the fracturing pipeline 210 to seal the crack. This setting achieves crack sealing.

[0033] In this embodiment of the invention, after step S114, which involves controlling the fracturing pump 20 to inject a curing agent into the fracturing hole 30 via the fracturing pipeline 210 to seal the fracture, the hydraulic fracturing method further includes: S116, control the fracturing pump 20 to inject the first fracturing fluid into the fracturing hole 30 through the fracturing pipeline 210 to enhance the bonding strength between the hardener and the fracture.

[0034] This invention also provides a hydraulic fracturing system that applies the above-described hydraulic fracturing method for underground coal mines. (See attached diagram.) Figure 5 The hydraulic fracturing system includes: The fracturing injection module 1 is equipped with a fracturing pump 20 connected to the fracturing hole 30, which is used to inject the first fracturing fluid or the second fracturing fluid into the fracturing hole 30. The fracturing monitoring module 2 includes a microseismic sensor 50 and a scanning probe 40. The microseismic sensor 50 is used to acquire the initial location of the fractures in the target coal seam A; the scanning probe 40 is used to scan the fractures and generate a three-dimensional image of the fractures. The fracturing control module 3 is used to obtain the deflection angle of the fracture based on the three-dimensional image of the fracture; if the deflection angle of the fracture is greater than the preset deflection angle value, the fracturing pump 20 is controlled to inject the second fracturing fluid into the fracturing hole 30 to correct the deflection angle of the fracture.

[0035] The hydraulic fracturing system provided in this embodiment of the invention applies the above-mentioned underground hydraulic fracturing method for coal mines and has all the advantages of the above-mentioned underground hydraulic fracturing method for coal mines, which will not be repeated here.

[0036] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for hydraulic fracturing in coal mines, characterized in that, include: The fracturing pump (20) is controlled to inject the first fracturing fluid into the fracturing hole (30) located in the target coal seam (A); During the first fracturing fluid injection process, the initial position of the fracture in the target coal seam (A) is acquired based on the microseismic sensor (50) installed in the surrounding rock (B) of the roadway; and the fracture is scanned based on the scanning probe (40) installed in the target coal seam (A) and a three-dimensional image of the fracture is generated. Based on the three-dimensional image of the crack, the deflection angle of the crack is obtained; If the deflection angle of the fracture is greater than the preset fracture deflection angle value, the fracturing pump (20) is controlled to inject a second fracturing fluid into the fracturing hole (30) to correct the deflection angle of the fracture. Wherein, the viscosity of the first fracturing fluid is less than that of the second fracturing fluid; the first fracturing fluid is water, and the second fracturing fluid is a mixture of gel and water; The fracturing holes (30) are at least two and spaced apart; the outlet of the fracturing pump (20) is connected to a fracturing pipeline (210), and the fracturing pipeline (210) is provided with at least two first control valves (211), which are used to connect or disconnect the fracturing pipeline (210) from the fracturing holes (30). The step of determining whether the deflection angle of the fracture is greater than a preset fracture deflection angle value, and then controlling the fracturing pump (20) to inject the second fracturing fluid into the fracturing hole (30), includes: Based on the deflection angle of the crack, a first deflection region and a second deflection region of the crack are obtained, wherein the deflection angle of the crack in the first deflection region is greater than the preset crack deflection angle value and the preset crack deflection angle value is greater than the crack deflection angle in the second deflection region. If the first deflection region exists, the first control valve (211) corresponding to the first deflection region and the second deflection region is closed to stop the injection of the first fracturing fluid into the fracturing hole (30). Open the first control valve (211) corresponding to the first deflection area and keep the first control valve (211) corresponding to the second deflection area closed, and control the fracturing pump (20) to inject the second fracturing fluid into the fracturing hole (30) corresponding to the first deflection area to correct the deflection angle of the fracture in the first deflection area.

2. The method for hydraulic fracturing in coal mines according to claim 1, characterized in that, The hydraulic fracturing method further includes: If the deflection angle of the corrected fracture is less than or equal to the preset fracture deflection angle value, then the fracturing pump (20) is controlled to inject the first fracturing fluid into the fracturing hole (30).

3. The method for hydraulic fracturing in coal mines according to claim 1 or 2, characterized in that, After the step of controlling the fracturing pump (20) to inject the second fracturing fluid into the fracturing hole (30) corresponding to the first deflection region, the hydraulic fracturing method further includes: If the deflection angle of the fracture in the first deflection region after correction is less than or equal to the preset fracture deflection angle value, then the first control valve (211) corresponding to the first deflection region and the first control valve (211) corresponding to the second deflection region are kept open, and the fracturing pump (20) is controlled to inject the first fracturing fluid into the fracturing hole (30).

4. The method for hydraulic fracturing in coal mines according to claim 1 or 2, characterized in that, The inlet of the fracturing pump (20) is connected to a storage tank (10), and the storage tank (10) is equipped with a fluid viscosity sensor (110) for monitoring the viscosity of the gel in the second fracturing fluid. The step of controlling the fracturing pump (20) to inject the second fracturing fluid into the fracturing hole (30) corresponding to the first deflection region further includes: if the viscosity of the gel fluctuates abnormally, then adjusting the injection rate or injection ratio of the gel.

5. The method for hydraulic fracturing in coal mines according to claim 4, characterized in that, The step of determining whether to adjust the injection rate or injection ratio of the gel if the viscosity of the gel fluctuates abnormally includes: If the ratio of the change in viscosity of the gel within a first time period to a preset viscosity value is greater than a preset viscosity ratio, then the injection rate or injection ratio of the gel is reduced; otherwise, the injection rate or injection ratio of the gel is increased. Alternatively, if the viscosity of the gel is greater than a preset viscosity value during the second time period, the injection rate or injection ratio of the gel is reduced; otherwise, the injection rate or injection ratio of the gel is increased.

6. The method for hydraulic fracturing in coal mines according to claim 1 or 2, characterized in that, The return port of the fracturing pump (20) is connected to a return pipeline (220), and the return pipeline (220) is equipped with a second control valve (221). The second control valve (221) is used to connect or disconnect the return port of the fracturing pump (20) from the return pipeline (220). At the end of the return pipeline (220) away from the return port of the fracturing pump (20), a cyclone precipitator (60), a filter (70), a mineralization enhancement device (80), and a recovery liquid tank are connected in sequence. The hydraulic fracturing method further includes: Based on the three-dimensional image of the fracture, if it is determined that the fracture extends beyond the preset target boundary, the second control valve (221) is opened to connect the return port of the fracturing pump (20) and the return pipeline (220). The first fracturing fluid or the second fracturing fluid flows into the recovery liquid tank sequentially through the fracturing pipeline (210), the return port of the fracturing pump (20), the return pipeline (220), the cyclone precipitator (60), the filter (70), and the mineralization enhancement device (80).

7. The method for hydraulic fracturing in coal mines according to claim 1 or 2, characterized in that, The hydraulic fracturing method further includes: Based on the three-dimensional image of the crack, if it is determined that the crack extends beyond the preset target boundary, the fracturing pump (20) is controlled to inject a curing agent into the fracturing hole (30) through the fracturing pipeline (210) to seal the crack.

8. The method for hydraulic fracturing in coal mines according to claim 7, characterized in that, After the step of controlling the fracturing pump (20) to inject a curing agent into the fracturing hole (30) through the fracturing pipeline (210) to seal the fracture, the hydraulic fracturing method further includes: The fracturing pump (20) is controlled to inject the first fracturing fluid into the fracturing hole (30) through the fracturing pipeline (210) to enhance the bonding strength between the curing agent and the fracture.

9. A hydraulic fracturing system, characterized in that, The hydraulic fracturing method for coal mines according to any one of claims 1-8, wherein the hydraulic fracturing system comprises: The fracturing injection module (1) is used to control the fracturing pump (20) to inject the first fracturing fluid or the second fracturing fluid into the fracturing hole (30); The fracturing monitoring module (2) includes a microseismic sensor (50) and a scanning probe (40). The microseismic sensor (50) is used to acquire the initial location of the fractures in the target coal seam (A). The scanning probe (40) is used to scan the fractures and generate a three-dimensional image of the fractures. The fracturing control module is used to obtain the deflection angle of the fracture based on the three-dimensional image of the fracture; if the deflection angle of the fracture is greater than the preset deflection angle value, the fracturing pump (20) is controlled to inject a second fracturing fluid into the fracturing hole (30) to correct the deflection angle of the fracture.

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