An automatic control system and method for hydraulic staged fracturing in a coal mine underground

Abstract

The application discloses a kind of coal mine underground hydraulic subsection fracturing automatic control system and method, system includes central main control module, high-pressure liquid supply module, underground subsection execution module, monitoring feedback module and automatic push module.Well. Central main control module is arranged with the automatic operation control logic based on state machine, state jump is automatically triggered according to monitoring feedback signal, and the coordinated action of each module is closed-loop controlled.Double-redundancy redundant configuration is used for hole sealing pressure sensor, and seamless switching is realized when fault occurs.Automatic push module uses feedforward-feedback compound step control algorithm, and millimeter-level subsection positioning is realized by position closed loop.Automatic pressure relief circuit executes time sequence grading unloading strategy, and pilot slow unloading, main valve fast unloading are used to suppress water hammer impact.Central main control module realizes the quantitative evaluation of fracturing effect by calculating fracturing energy index.The application realizes the unmanned automatic operation of underground subsection fracturing, and improves the subsection accuracy and operation safety.

Description

Technical Field

[0001] This invention belongs to the field of underground hydraulic fracturing technology in coal mines, and relates to an automatic control system and method for underground hydraulic segmented fracturing in coal mines. Background Technology

[0002] In underground coal mining, the difficulty in collapsing a hard roof and the low permeability of coal seams are major problems affecting safe production and efficient extraction. Hydraulic fracturing technology, as an effective means of rock strata control and permeability enhancement, is widely used in underground coal mines. It creates artificial fractures by injecting high-pressure fluid into target rock strata or coal seams, thereby weakening the roof or increasing the permeability of the coal seam.

[0003] Existing downhole hydraulic fracturing operations mainly rely on manual operation, which has the following significant drawbacks: First, the process is labor-intensive and lacks precision in segmentation. Coal mine boreholes are typically tens or even hundreds of meters deep, requiring multi-stage fracturing along the borehole axis. Current technologies often use manual push rods or manual hoists to move the sealing device assembly, resulting in extremely high labor intensity for workers. More importantly, this method relies solely on visual inspection or simple markings to determine the distance moved each time, failing to provide closed-loop control and real-time compensation for the movement process. This leads to large errors in the actual segment spacing and uneven distribution of fracturing segments, directly affecting the uniform weakening of rock strata or the uniform permeability enhancement of coal seams.

[0004] Secondly, operators face high safety risks. During fracturing, the start-up and shutdown of the high-pressure pump, the sealing of the borehole, and the switching of fracturing water valves are all manually performed by operators near the borehole. The pressure in the high-pressure pipeline system can reach tens of megapascals. Once a pipeline ruptures, a joint detaches, or a seal fails, high-pressure fluid will be ejected instantly, directly threatening the lives of the operators. In addition, relying on manual judgment and emergency response in abnormal operating conditions makes it difficult to guarantee the speed and accuracy of response.

[0005] Furthermore, the control precision is poor and the process coordination is weak. Sealing and fracturing are closely linked and pressure-coupled processes. Manual observation of pointer-type pressure gauges suffers from visual lag and reading errors, making it difficult to accurately determine whether the sealing pressure has stabilized and met process requirements. Often, fracturing is initiated before the sealing pressure is sufficient, leading to axial slippage of the packer under high pressure; or, failure to promptly and smoothly depressurize after fracturing causes problems such as packer retraction difficulties and tool string jamming. Simultaneously, the entire "sealing-fracturing-depressurization" cycle lacks standardized automated logic control, and the coordination between processes relies entirely on the operator's personal experience, resulting in large fluctuations in work quality and overall low efficiency.

[0006] In summary, existing technologies suffer from problems such as high labor intensity of manual operation, inability to guarantee segmented positioning accuracy, high safety risks of high-pressure operation, and rough coordination control of multiple processes such as sealing and fracturing. There is an urgent need for a hydraulic segmented fracturing control system and method for coal mines that can achieve automated, high-precision, and unmanned operation. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide an automatic control system and method for hydraulic fracturing in coal mines, which aims to solve the problems of high labor intensity, low segment positioning accuracy and high safety risk of high-pressure operation in the prior art, and improve the automation level of hydraulic fracturing in coal mines.

[0008] In a first aspect, the present invention provides an automatic control system for hydraulic fracturing in coal mines, comprising: The central control module is used to receive sensor data, process control logic, and issue action commands. The high-pressure fluid supply module communicates with the central control module and is used to provide the high-pressure fluid required for fracturing operations. The high-pressure fluid supply module includes a variable frequency high-pressure pump set and an intelligent valve control set. The underground segmented execution module is connected to the high-pressure fluid supply module through a high-pressure pipeline and extends into the underground borehole of the coal mine to isolate and fracturing the target section inside the borehole. The monitoring and feedback module is located at the output end of the high-pressure fluid supply module and the downhole segment execution module. It is used to monitor the system pressure, flow rate and sealing status in real time and feed the signals back to the central main control module. An automatic propulsion and walking module is connected to the downhole segment execution module and is used to control the axial movement of the downhole segment execution module within the borehole. The central control module is equipped with automatic operation control logic based on a state machine. The state machine includes at least six states in sequence: system standby, push-in, sealing and pressurizing, fracturing operation, depressurization and recovery, and step transition. The central control module automatically triggers state transitions based on the comparison results between the real-time signals from the monitoring feedback module and the preset thresholds, so as to control the coordinated operation of the high-pressure liquid supply module and the automatic propulsion and walking module in a closed loop.

[0009] Optionally, the downhole segmented execution module is a modular series structure, including a front-end guide assembly, a front packer, a fracturing release device, and a rear packer connected in sequence; the front packer and the rear packer form an independent fracturing chamber; the intelligent valve control group includes a sealing water circuit solenoid valve and a fracturing water circuit solenoid valve, which are used to control the expansion of the front packer and the rear packer and the opening of the fracturing release device, respectively.

[0010] Optionally, the monitoring and feedback module includes: The main flow sensor is installed at the outlet of the variable frequency high-pressure pump set. A sealing pressure sensor is installed on the pipeline leading to the pre-packer and the post-packer; A fracturing pressure sensor is installed on the pipeline leading to the fracturing release device; The central control module has a preset sealing pressure threshold. When the detected sealing pressure reaches the sealing pressure threshold, it automatically switches to the fracturing program.

[0011] Optionally, the sealing pressure sensor is configured with dual redundancy, including a primary sensor and a backup sensor, both installed at the same pressure measurement point; the central main control module executes redundancy management logic: when the primary sensor signal is lost or the difference between the primary sensor and the backup sensor exceeds the preset failure deviation threshold, it automatically and seamlessly switches to the backup sensor as the control signal source and triggers a sensor maintenance alarm through the human-machine interface.

[0012] Optionally, the automatic propulsion and walking module includes an explosion-proof tracked vehicle body and a hydraulic push-pull manipulator mounted on the explosion-proof tracked vehicle body; the hydraulic push-pull manipulator clamps the high-pressure pipeline connecting to the downhole segment execution module; the central main control module has a built-in stepping control algorithm, which adopts a feedforward-feedback composite control strategy: the central main control module plans an S-shaped or trapezoidal target velocity curve in real time based on the preset propulsion distance, maximum allowable speed and acceleration, and outputs it as a feedforward control quantity to the hydraulic proportional valve; at the same time, it receives the actual displacement feedback from the displacement sensor mounted on the hydraulic push-pull manipulator in real time, calculates the deviation from the theoretical target position, generates a feedback compensation quantity through a PID controller, and superimposes it on the feedforward control quantity to form a position closed loop.

[0013] Furthermore, the intelligent valve control group also includes an automatic pressure relief circuit; when the central main control module controls the automatic pressure relief circuit, it executes a time-sequential graded unloading strategy: Open a pilot unloading valve with a smaller diameter to gradually reduce the system pressure at the initial rate; Once the pressure drops to the preset intermediate threshold, open a main unloading valve with a larger diameter to quickly depressurize to below the safety threshold at a second rate. The first speed is less than the second speed.

[0014] Optionally, the central control module includes a PLC controller, a human-machine interface touch screen, and a data storage unit; the data storage unit automatically records the complete process data package for each fracturing operation, and the process data package includes at least: segment number, timestamp, sealing pressure-time curve, fracturing pressure-time curve, instantaneous flow rate-time curve, cumulative water injection volume, and advance distance; The central control module has a built-in fracturing effect evaluation algorithm, which automatically calculates the fracturing energy index E for each stage based on the process data package. The formula for calculating the fracturing energy index E is: , where P iQ represents the instantaneous fracturing pressure value at the i-th sampling point during the effective fracturing holding phase. i Let Δt be the instantaneous fracturing flow rate at the i-th sampling point. i Σ represents the sampling time interval, and Σ represents the integral summation of all sampling points over the entire effective fracturing holding phase.

[0015] Secondly, the present invention also provides an automatic control method for hydraulic fracturing in coal mines, applied to the aforementioned automatic control system, comprising the following steps: S1: Initialization and self-test: After the central main control module is powered on, it performs communication self-test on each module to confirm that the liquid level of the high-pressure liquid supply module, the status of the variable frequency high-pressure pump group and the intelligent valve control group are normal, and the position of the automatic propulsion walking module is returned to zero. S2: Operational parameter settings: Operators can set the number of segments, single-segment advance distance, single-segment water injection volume, pressure holding time, sealing pressure threshold, fracturing pressure upper limit, and system safety unloading pressure through the human-machine interface touch screen. S3: Automatic positioning of the first stage: The central control module controls the automatic propulsion and walking module to push the downhole segment execution module to the first target fracturing stage at the deepest point of the borehole; S4: Automatic sealing: The central main control module controls the high-pressure fluid supply module to start and opens the sealing water circuit solenoid valve in the intelligent valve control group, driving the variable frequency high-pressure pump group at the first preset frequency to inject fluid into the packer in the downhole segment execution module; when the monitoring feedback module detects that the sealing pressure reaches the sealing pressure threshold, it maintains the current pressure and completes the sealing. S5: Automatic fracturing: After the sealing pressure stabilizes, the central main control module automatically closes the sealing water circuit solenoid valve, opens the fracturing water circuit solenoid valve, and drives the variable frequency high-pressure pump group at the second preset frequency to inject high-pressure fluid into the target fracturing section for fracturing; at the same time, the injection volume is accumulated in real time through the main pipe flow sensor. When the accumulated injection volume reaches the single-stage injection volume or the holding time reaches the holding time, the fracturing of this stage is completed. S6: Automatic pressure relief and recovery: The central main control module closes the fracturing water circuit solenoid valve and opens the automatic pressure relief circuit to allow the high-pressure fluid in the system to flow back; when the monitoring feedback module detects that the system pressure has dropped below the system's safe unloading pressure, it controls the packer to be recovered. S7: Automatic step conversion: The central main control module controls the automatic propulsion and walking module to pull the downhole segment execution module outward by a single segment propulsion distance, so that the fracturing release device is aligned with the next target segment; S8: Cyclic operation: Repeat steps S4 to S7 until all set fracturing operations are completed. Then the system will automatically enter standby mode and issue an audible and visual prompt.

[0016] Optionally, the automated fracturing in step S5 may also include: The central control module monitors the fracturing pressure in real time and dynamically stabilizes the fracturing pressure within the process requirements range through the built-in PID regulator. When the fracturing pressure is detected to exceed the upper limit of the fracturing pressure, the frequency of the variable frequency high-pressure pump group is automatically adjusted to perform pressure limiting protection.

[0017] The beneficial effects of this invention are as follows: This invention provides an automatic control system and method for hydraulic fracturing in coal mines. Through a combination of modular design and state machine closed-loop control logic, it integrates traditionally decentralized manual operations into a fully automated workflow. Operators only need to set parameters and start the system on the human-machine interface. The central control module automatically completes the entire cycle from initial positioning to final fracturing. During this process, operators do not need to approach the high-pressure area at the borehole opening, thus avoiding the safety threats posed by high-pressure fluid jets and pipeline ruptures.

[0018] In terms of segmentation accuracy, the automatic propulsion and walking module adopts a feedforward-feedback composite stepping control algorithm. By planning the speed curve in real time and forming a position closed loop with displacement feedback compensation, the repeatability of each segmentation step reaches the millimeter level, ensuring the uniformity of the spacing between each fracturing segment and providing a reliable position benchmark for the uniform weakening of rock strata or the uniform permeability enhancement of coal seams.

[0019] In terms of process coordination, the system uses a sealing pressure sensor to provide real-time feedback. It automatically switches to the fracturing procedure only after the sealing pressure accurately reaches the set threshold, eliminating the lag and error of manual judgment and avoiding packer slippage caused by incomplete sealing. The dual-redundancy configuration and seamless switching logic of the sealing pressure sensor ensure continuous and reliable system operation even in the event of a single sensor failure.

[0020] In terms of safety protection, the automatic pressure relief circuit adopts a time-sequential graded unloading strategy, first using a small-diameter pilot valve to gently release pressure, and then using a large-diameter main valve to quickly release pressure, which avoids the water hammer impact on pipelines and equipment caused by the instantaneous release of high-pressure fluid, and helps to extend the service life of the equipment.

[0021] In terms of operational effectiveness evaluation, the fracturing energy index algorithm built into the central control module performs integral calculations on the pressure and flow data of each fracturing process, replacing the qualitative judgments that previously relied on manual experience with quantitative indicators. This allows operators to intuitively compare the fracturing effects of each stage and provides data references for optimizing process parameters.

[0022] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 The overall architecture block diagram of the automatic control system for hydraulic fracturing in coal mines provided by the present invention; Figure 2 This is a schematic diagram showing the hardware composition and connection relationship of the automatic control system for hydraulic fracturing in coal mines provided by the present invention. Figure 3 The flowchart of the automatic control method for hydraulic segmented fracturing in coal mines provided by the present invention is shown.

[0024] Figure label: 100-Central main control module; 110-PLC controller; 120-Human machine interface terminal; 130-Data storage unit; 200-High pressure fluid supply module; 210-Water tank; 220-Variable frequency high pressure pump set; 230-Intelligent valve control group; 231-Sealing water circuit solenoid valve; 232-Fracturing water circuit solenoid valve; 233-Automatic pressure relief circuit; 240-Main pipe flow sensor; 300-Downhole segmented execution module; 310-Front-end guide assembly; 320-Pre-packer; 330-Fracturing release device; 340-Rear packer; 400-Monitoring feedback module; 410-Sealing pressure sensor; 420-Fracturing pressure sensor; 430-Micro-vibration monitoring unit; 500-Automatic propulsion and walking module; 510-Explosion-proof tracked vehicle body; 520-Hydraulic push-pull manipulator. Detailed Implementation

[0025] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0026] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0027] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0028] In underground hydraulic fracturing operations in coal mines, existing technologies largely rely on manual push rod movement of the sealing device, manual control of high-pressure pump start-up and shutdown and valve switching, and visual inspection of pressure gauge readings. This results in high labor intensity, poor segmented positioning accuracy, high safety risks associated with high-pressure operations, and inefficient coordination between sealing and fracturing processes. To address these technical problems, this invention provides an automatic control system and method for underground hydraulic segmented fracturing in coal mines, which will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Reference Figure 1 and Figure 2 This embodiment provides an automatic control system for hydraulic fracturing in coal mines, including a central main control module 100, a high-pressure fluid supply module 200, an underground segment execution module 300, a monitoring and feedback module 400, and an automatic propulsion and walking module 500.

[0030] The central control module 100, serving as the system's control core, includes a PLC controller 110, a human-machine interface 120, and a data storage unit 130. The central control module 100 incorporates state machine-based automatic operation control logic, with the state machine sequentially comprising six states: system standby, push-in positioning, borehole sealing and pressurization, fracturing operation, pressure relief and recovery, and step transition. Based on the comparison between the real-time signal from the monitoring feedback module 400 and preset thresholds, the central control module 100 automatically triggers state transitions to achieve closed-loop control of the coordinated operation of the high-pressure fluid supply module 200 and the automatic propulsion and walking module 500.

[0031] The high-pressure liquid supply module 200 is communicatively connected to the central main control module 100 and includes a water tank 210, a variable frequency high-pressure pump set 220, and an intelligent valve control group 230. The intelligent valve control group 230 includes a sealing water circuit solenoid valve 231, a fracturing water circuit solenoid valve 232, and an automatic pressure relief circuit 233.

[0032] The downhole segmented execution module 300 has a modular, series structure. It is connected to the high-pressure fluid supply module 200 via a high-pressure pipeline and extends into the coal mine borehole. The downhole segmented execution module 300 includes a front-end guide assembly 310, a pre-packer 320, a fracturing release device 330, and a rear-packer 340 connected in sequence. The pre-packer 320 and the rear-packer 340 form an independent fracturing chamber. The sealing water circuit solenoid valve 231 and the fracturing water circuit solenoid valve 232 are used to control the expansion of the pre-packer 320 and the rear-packer 340, and the opening of the fracturing release device 330, respectively.

[0033] The monitoring feedback module 400 includes a main pipe flow sensor 240, a perforation pressure sensor 410, and a fracturing pressure sensor 420. The main pipe flow sensor 240 is located at the outlet of the variable frequency high-pressure pump set 220 and is used to accumulate the injection volume in real time. The perforation pressure sensor 410 is located on the pipeline leading to the pre-packer 320 and the post-packer 340. The fracturing pressure sensor 420 is located on the pipeline leading to the fracturing release device 330. The central control module 100 has a preset perforation pressure threshold. The perforation pressure sensor 410 adopts a dual-redundancy configuration, including a primary sensor and a backup sensor, both installed at the same pressure measuring point. The monitoring feedback module 400 also includes a microseismic monitoring unit 430. The fracturing release device 330 integrates an acoustic wave generator. The microseismic monitoring unit 430 receives the acoustic wave signal from the fracturing release device 330 and the rock fracture signal during the fracturing process to determine the fracture propagation range.

[0034] The automatic propulsion and walking module 500 is connected to the downhole segment execution module 300, and includes an explosion-proof tracked vehicle body 510 and a hydraulic push-pull manipulator 520 mounted on the vehicle body. The hydraulic push-pull manipulator 520 clamps the high-pressure pipeline connected to the downhole segment execution module 300. The central main control module 100 has a built-in stepping control algorithm.

[0035] The high-pressure fluid supply module 200 is connected to the downhole segment execution module 300 via a quick-connect coupling. The modules are electrically connected using explosion-proof aviation plugs to enable rapid disassembly and reassembly of the system.

[0036] Based on the above system, this embodiment provides an automatic control method for hydraulic fracturing in coal mines, including the following steps: S1. Initialization and Self-Test After the central main control module 100 is powered on, it performs a communication self-test on each module to confirm that the water level in the water tank 210 of the high-pressure liquid supply module 200 meets the operation requirements, the variable frequency high-pressure pump group 220 is in normal condition, and all solenoid valves in the intelligent valve control group 230 are in the closed position. It also controls the hydraulic push-pull manipulator 520 of the automatic propulsion and walking module 500 to return to the zero position.

[0037] S2, Operation Parameter Setting Operators set the following operating parameters via the human-machine interface terminal 120: number of segments N, single-segment advance distance L, and single-segment water injection volume V. set Holding time T hold Sealing pressure threshold P seal Upper limit of fracturing pressure P max Intermediate threshold P mid System safety unloading pressure P safe and sensor failure deviation threshold.

[0038] S3, First segment automatically positioned The central control module 100 controls the automatic propulsion and walking module 500 to push the downhole segment execution module 300 to the first target fracturing section at the deepest point of the borehole.

[0039] S4, Automatic Sealing This step includes the following sub-steps: S4-1, The central main control module 100 controls the variable frequency high-pressure pump group 220 to start softly at the first preset frequency f1, and at the same time opens the sealing water circuit solenoid valve 231 in the intelligent valve control group 230 to inject fluid into the front packer 320 and the rear packer 340 in the downhole segment execution module 300, so that it expands step by step and fits tightly against the borehole wall. S4-2, the sealing pressure sensor 410 continuously transmits the pressure value back to the central main control module 100. The central main control module 100 compares the values ​​of the main sensor and the backup sensor in real time. When the main sensor signal is lost or the difference between the main sensor and the backup sensor exceeds the preset sensor failure deviation threshold, it automatically and seamlessly switches to the backup sensor as the control signal source and triggers a sensor maintenance alarm through the human-machine interface terminal 120. S4-3, When the monitoring feedback module 400 detects that the sealing pressure has reached the sealing pressure threshold P seal At that time, the central main control module 100 controls the variable frequency high-pressure pump group 220 to maintain the current pressure and complete the sealing.

[0040] S5, Automatic Fracturing This process includes the following sub-steps: S5-1 After confirming that the sealing pressure is stable, the central main control module 100 closes the sealing water circuit solenoid valve 231, opens the fracturing water circuit solenoid valve 232, and increases the operating frequency of the variable frequency high-pressure pump group 220 to the second preset frequency f2, injecting high-pressure fluid into the target fracturing section for fracturing. S5-2, the central control module 100 monitors fracturing pressure in real time and dynamically stabilizes the fracturing pressure within the process requirements range through a built-in PID controller; when the fracturing pressure is detected to exceed the upper limit P, max At that time, the frequency of the variable frequency high-pressure pump unit 220 is automatically adjusted for pressure limiting protection; S5-3, Main pipe flow sensor 240, real-time cumulative water injection volume; when the cumulative water injection volume reaches the single-stage water injection volume V... set Or the holding time reaches the holding time T hold At that time, the central control module 100 determines that the fracturing operation of this section is completed.

[0041] S6, Automatic Pressure Relief and Recovery This process includes the following sub-steps: S6-1, The central control module 100 closes the fracturing water circuit solenoid valve 232, opens the automatic pressure relief circuit 233, and executes a time-sequential graded unloading strategy to allow high-pressure fluid in the system to flow back; the time-sequential graded unloading strategy specifically involves: firstly, opening the pilot unloading valve with a smaller diameter in the automatic pressure relief circuit 233 to gradually reduce the system pressure at a first rate; and then waiting for the pressure to drop to a preset intermediate threshold P. mid Then, open the main unloading valve with a larger diameter in the automatic pressure relief circuit 233 to quickly depressurize to the system's safe unloading pressure P at a second rate. safe The following applies: the first rate is less than the second rate; S6-2, When the monitoring feedback module 400 detects that the system pressure has dropped to the system safe unloading pressure P... safe After that, the central control module 100 controls the packer to be retrieved.

[0042] S7, Automatic Step Conversion This process includes the following sub-steps: S7-1, The central main control module 100 calls the built-in stepping control algorithm. The stepping control algorithm adopts a feedforward-feedback composite control strategy: based on the preset single-segment propulsion distance L, as well as the system's preset maximum allowable speed and acceleration, it plans an S-shaped or trapezoidal target speed curve in real time, which is then output to the hydraulic proportional valve as a feedforward control quantity. S7-2, the central main control module 100 receives the actual displacement feedback from the displacement sensor set on the hydraulic push-pull manipulator 520 in real time, calculates the deviation from the theoretical target position, generates feedback compensation through the PID regulator, and superimposes it on the feedforward control quantity to form a position closed loop. Under the aforementioned composite control, the S7-3 hydraulic push-pull manipulator 520 pulls the downhole segment execution module 300 outward by a single-segment advance distance L, so that the fracturing release device 330 is aligned with the next target segment, and the step-by-step repeat positioning accuracy is controlled within ±5mm.

[0043] S8, Cyclic Operation Repeat steps S4 to S7 until all N designated fracturing operations are completed.

[0044] Throughout the entire operation, the data storage unit 130 automatically records the complete process data package for each segment of the fracturing operation. The process data package includes at least: segment number, timestamp, sealing pressure-time curve, fracturing pressure-time curve, instantaneous flow rate-time curve, cumulative water injection volume, and advance distance.

[0045] The central control module 100 has a built-in fracturing effect evaluation algorithm that automatically calculates the fracturing energy index E for each segment. The formula for calculating the fracturing energy index E is as follows: , where P i Q represents the instantaneous fracturing pressure value at the i-th sampling point during the effective fracturing holding phase. i Let Δt be the instantaneous fracturing flow rate at the i-th sampling point. i The sampling time interval is Σ, which represents the integral summation of all sampling points over the entire effective fracturing holding phase. The fracturing energy index E of each segment is displayed in a bar chart on the human-computer interaction terminal 120, correlated with the location of each segment.

[0046] The central control module 100 receives signals from the microseismic monitoring unit 430, calls the built-in microseismic event localization algorithm, inverts the three-dimensional spatial location of the microseismic event in real time, automatically generates the spatial distribution pattern of the crack, and displays it as an overlay layer on the borehole trajectory model of the human-computer interaction terminal 120.

[0047] Once all tasks are completed in a cycle, the system will automatically enter standby mode and issue an audible and visual alert.

[0048] This invention upgrades traditional, decentralized, manual, and high-risk fracturing operations to unmanned operation mode through modular system design and a state machine-based fully automatic closed-loop control method. Dual-redundant perforation pressure sensor redundancy management logic ensures high reliability of critical control signals; the feedforward-feedback composite stepping control algorithm achieves millimeter-level segmented positioning accuracy, guaranteeing uniform fracturing in each fracturing segment; the time-sequential graded unloading strategy effectively suppresses the impact of water hammer on the equipment; and the introduction of the fracturing energy index E elevates the fracturing effect from empirical qualitative judgment to data-driven quantitative evaluation. Operators remain completely away from the high-pressure danger zone at the orifice, fundamentally improving intrinsic safety.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An automatic control system for hydraulic fracturing in coal mines, characterized in that, include: The central control module is used to receive sensor data, process control logic, and issue action commands. The high-pressure fluid supply module is communicatively connected to the central main control module and is used to provide high-pressure fluid required for fracturing operations. The high-pressure fluid supply module includes a variable frequency high-pressure pump group and an intelligent valve control group. The underground segmented execution module is connected to the high-pressure fluid supply module via a high-pressure pipeline and extends into the underground borehole of the coal mine for isolating and fracturing the target section within the borehole. The monitoring and feedback module is located at the output end of the high-pressure fluid supply module and the downhole segment execution module. It is used to monitor the system pressure, flow rate and sealing status in real time and feed the signal back to the central main control module. An automatic propulsion and walking module is connected to the downhole segment execution module and is used to controllably drive the downhole segment execution module to move axially within the borehole. The central control module is equipped with automatic operation control logic based on a state machine. The state machine includes at least six states in sequence: system standby, push-in, sealing and pressurizing, fracturing operation, depressurization and recovery, and step transition. The central control module automatically triggers a state transition based on the comparison result between the real-time signal from the monitoring feedback module and the preset threshold, thereby controlling the coordinated operation of the high-pressure liquid supply module and the automatic propulsion and walking module in a closed loop.

2. The automatic control system according to claim 1, characterized in that, The downhole segmented execution module is a modular series structure, including a front-end guide assembly, a front packer, a fracturing release device, and a rear packer connected in sequence; the front packer and the rear packer form an independent fracturing chamber; the intelligent valve control group includes a sealing water circuit solenoid valve and a fracturing water circuit solenoid valve, which are used to control the expansion of the front packer and the rear packer and the opening of the fracturing release device, respectively.

3. The automatic control system according to claim 2, characterized in that, The monitoring feedback module includes: A main flow sensor is installed at the outlet of the variable frequency high-pressure pump unit; A sealing pressure sensor is installed on the pipeline leading to the pre-packer and the post-packer; A fracturing pressure sensor is installed on the pipeline leading to the fracturing release device; The central control module is preset with a sealing pressure threshold. When the detected sealing pressure reaches the sealing pressure threshold, it automatically switches to the fracturing program.

4. The automatic control system according to claim 3, characterized in that, The sealing pressure sensor is a dual-redundant configuration, including a primary sensor and a backup sensor, both installed at the same pressure measurement point. The central control module executes redundancy management logic: when the primary sensor signal is lost or the difference between the primary sensor and the backup sensor exceeds a preset failure deviation threshold, it automatically and seamlessly switches to the backup sensor as the control signal source and triggers a sensor maintenance alarm through the human-machine interface.

5. The automatic control system according to claim 1, characterized in that, The automatic propulsion and walking module includes an explosion-proof tracked vehicle body and a hydraulic push-pull manipulator mounted on the explosion-proof tracked vehicle body; the hydraulic push-pull manipulator clamps the high-pressure pipeline connected to the downhole segment execution module; the central main control module has a built-in stepping control algorithm, which adopts a feedforward-feedback composite control strategy: the central main control module plans an S-shaped or trapezoidal target velocity curve in real time based on the preset propulsion distance, maximum allowable speed and acceleration, and outputs it as a feedforward control quantity to the hydraulic proportional valve; at the same time, it receives the actual displacement feedback from the displacement sensor mounted on the hydraulic push-pull manipulator in real time, calculates the deviation from the theoretical target position, generates a feedback compensation quantity through a PID controller, and superimposes it on the feedforward control quantity to form a position closed loop.

6. The automatic control system according to claim 1, characterized in that, The intelligent valve control group also includes an automatic pressure relief circuit; when the central main control module controls the automatic pressure relief circuit, it executes a time-sequential graded unloading strategy: Open a pilot unloading valve with a smaller diameter to gradually reduce the system pressure at the initial rate; Once the pressure drops to the preset intermediate threshold, open a main unloading valve with a larger diameter to quickly depressurize to below the safety threshold at a second rate. The first rate is less than the second rate.

7. The automatic control system according to claim 1, characterized in that, The central control module includes a PLC controller, a human-machine interface touch screen, and a data storage unit. The data storage unit automatically records the complete process data package for each fracturing operation. The process data package includes at least: segment number, timestamp, sealing pressure-time curve, fracturing pressure-time curve, instantaneous flow rate-time curve, cumulative water injection volume, and advance distance. The central control module has a built-in fracturing effect evaluation algorithm, which is used to automatically calculate the fracturing energy index E for each stage based on the process data package. The formula for calculating the fracturing energy index E is as follows: , where P i Q represents the instantaneous fracturing pressure value at the i-th sampling point during the effective fracturing holding phase. i Let Δt be the instantaneous fracturing flow rate at the i-th sampling point. i Σ represents the sampling time interval, and Σ represents the integral summation of all sampling points over the entire effective fracturing holding phase.

8. An automatic control method for hydraulic fracturing in coal mines, applied to the automatic control system described in any one of claims 1-7, characterized in that, Includes the following steps: S1: Initialization and self-test: After the central main control module is powered on, it performs communication self-test on each module to confirm that the liquid level of the high-pressure liquid supply module, the status of the variable frequency high-pressure pump group and the intelligent valve control group are normal, and the position of the automatic propulsion walking module is returned to zero. S2: Operational parameter settings: Operators can set the number of segments, single-segment advance distance, single-segment water injection volume, pressure holding time, sealing pressure threshold, fracturing pressure upper limit, and system safety unloading pressure through the human-machine interface touch screen. S3: Automatic positioning of the first stage: The central control module controls the automatic propulsion and walking module to push the downhole segment execution module to the first target fracturing stage at the deepest point of the borehole; S4: Automatic sealing: The central main control module controls the high-pressure fluid supply module to start and opens the sealing water circuit solenoid valve in the intelligent valve control group, driving the variable frequency high-pressure pump group at the first preset frequency to inject fluid into the packer in the downhole segment execution module; When the monitoring and feedback module detects that the sealing pressure has reached the sealing pressure threshold, it maintains the current pressure and completes the sealing process. S5: Automatic fracturing: After the sealing pressure stabilizes, the central main control module automatically closes the sealing water circuit solenoid valve, opens the fracturing water circuit solenoid valve, and drives the variable frequency high-pressure pump group at the second preset frequency to inject high-pressure fluid into the target fracturing section for fracturing; at the same time, the injection volume is accumulated in real time through the main pipe flow sensor. When the accumulated injection volume reaches the single-stage injection volume or the holding time reaches the holding time, the fracturing of this stage is completed. S6: Automatic pressure relief and recovery: The central main control module closes the fracturing water circuit solenoid valve and opens the automatic pressure relief circuit to allow the high-pressure fluid in the system to flow back; when the monitoring feedback module detects that the system pressure has dropped below the system's safe unloading pressure, it controls the packer to be recovered. S7: Automatic step conversion: The central main control module controls the automatic propulsion and walking module to pull the downhole segment execution module outward by a single segment propulsion distance, so that the fracturing release device is aligned with the next target segment; S8: Cyclic operation: Repeat steps S4 to S7 until all set fracturing operations are completed. Then the system will automatically enter standby mode and issue an audible and visual prompt.

9. The automatic control method according to claim 8, characterized in that, The automated fracturing described in step S5 also includes: The central control module monitors the fracturing pressure in real time and dynamically stabilizes the fracturing pressure within the process requirements range through the built-in PID regulator. When the fracturing pressure is detected to exceed the upper limit of the fracturing pressure, the frequency of the variable frequency high-pressure pump group is automatically adjusted for pressure limiting protection.

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