A coal seam nitrogen injection intelligent linkage regulation and control system and method based on multi-parameter feedback

Abstract

The application discloses a coal seam nitrogen injection intelligent linkage regulation and control system and method based on multi-parameter feedback and belongs to the technical field of coal seam gas extraction. The underground execution unit of the system adopts a double-pipeline interlocking architecture, realizes uniform-speed pressurization and depressurization in combination with a first electric control proportional regulating valve and a second electric control proportional regulating valve, and avoids pressure impact; a sensing and monitoring unit collects nitrogen injection pressure and gas extraction multi-parameters in real time; an intelligent control unit adaptively regulates and controls pulse nitrogen injection parameters based on pressure feedback and effect diagnosis after fusion analysis of the gas extraction multi-parameters; and an uphole monitoring platform establishes an independent file for each nitrogen injection borehole, realizing personalized management of "one borehole one strategy". The application solves the problems of large equipment loss, easy damage of hole sealing structure, insufficient regulation and control intelligence and extensive nitrogen injection strategy in the prior art, improves gas displacement efficiency and extraction effect, and helps efficient and green development of coalbed methane.

Description

Technical Field

[0001] This invention belongs to the field of coal seam gas extraction technology, and particularly relates to an intelligent linkage control system and method for coal seam nitrogen injection based on multi-parameter feedback. Background Technology

[0002] Driven by the "dual carbon" strategic goals, coalbed methane, as an important unconventional natural gas resource, has dual significance in terms of energy supply and emission reduction through efficient extraction and utilization. Coalbed nitrogen injection for gas displacement is a key method for enhanced gas extraction in low-permeability coalbeds. By injecting nitrogen into the coal seam, the gas displacement and pressure-driven effects are utilized to reduce the partial pressure of the gas, promoting the desorption of adsorbed gas and its migration towards the extraction borehole, thereby improving gas extraction efficiency.

[0003] Existing nitrogen injection systems typically consist of nitrogen generators, nitrogen delivery pipelines, nitrogen injection boreholes, valve assemblies, and basic monitoring instruments. Control methods often rely on manual experience to preset parameters, or only achieve simple constant-pressure nitrogen injection and fixed-sequence pulse control, resulting in numerous shortcomings:

[0004] 1. The implementation method of pulse nitrogen injection to replace gas is unreasonable, which reduces the service life of the equipment:

[0005] Existing technologies often achieve pulsed nitrogen injection by frequently starting and stopping the nitrogen generator or booster pump. This working mode not only has high energy consumption, but also accelerates the wear and aging of key components such as motors and pumps due to repeated starting current surges and mechanical stress shocks, shortening the overall lifespan of the equipment and increasing maintenance costs, which is contrary to the actual requirements of long-term, stable and reliable operation in the well.

[0006] 2. The pressure control method is simple and crude, which can easily damage the sealing structure and reduce the uniformity of displacement.

[0007] Existing systems often use solenoid valves or butterfly valves for rapid opening and closing, resulting in sudden increases and decreases in nitrogen injection pipeline pressure, creating significant step-like pressure shocks. This impact load easily causes shear stress and fatigue damage between the sealing material and the pore wall, leading to gas leakage, which in turn reduces the efficiency of nitrogen injection pressure transmission and causes the injected nitrogen gas to preferentially flow along large fissures, making it difficult to achieve uniform displacement of adsorbed gas in micropores and affecting the overall extraction effect.

[0008] 3. The control logic is simple and rigid, lacking adaptive optimization capabilities based on multi-parameter feedback:

[0009] While existing systems may be equipped with basic sensors and PLCs, their control strategies are mostly based on preset fixed parameters or simple timing sequences, failing to establish a real-time closed-loop feedback between nitrogen injection parameters (pressure, flow rate, pulse timing) and gas extraction responses (concentration change trends, pressure recovery characteristics, flow rate fluctuations). The systems cannot automatically identify nitrogen injection effects (such as crossflow, blockage, and sufficient displacement) based on the dynamic response of the coal seam and adjust the nitrogen injection strategy in real time, resulting in a low level of intelligence.

[0010] 4. A one-size-fits-all approach to nitrogen injection makes it difficult to achieve differentiated and precise control:

[0011] Existing nitrogen injection systems typically apply uniform nitrogen injection parameters to all boreholes, ignoring the inherent differences in sealing quality, local geological conditions, and gas occurrence among different boreholes. This extensive approach leads to leaks in boreholes with poor sealing quality, while boreholes with good conditions may experience insufficient nitrogen injection, failing to maximize nitrogen injection potential and resulting in overall low efficiency.

[0012] Therefore, there is an urgent need to develop a nitrogen injection control system and method that features refined pressure control, intelligent regulation, real-time feedback, and personalized solutions to address the shortcomings of existing technologies. Summary of the Invention

[0013] To address the problems existing in the prior art, the purpose of this invention is to provide an intelligent linkage control system and method for coal seam nitrogen injection based on multi-parameter feedback.

[0014] To solve the above problems, the present invention adopts the following technical solution:

[0015] A coal seam nitrogen injection intelligent linkage control system based on multi-parameter feedback includes an underground execution unit, a sensor monitoring unit, an intelligent control unit, and an above-ground monitoring platform. Each unit is interconnected through a mining industrial ring network to form a complete closed loop.

[0016] The downhole actuator is the core actuator of the system, employing a multi-pressure branch interlocking architecture. Nitrogen generated by the nitrogen generator is divided into at least two pressure branches via a diversion structure. Interlocking of the solenoid valves in each branch is achieved through a relay group, ensuring that only one pressure branch is active at any given time, thus guaranteeing stable gas source pressure. The confluence of these pressure branches forms the main nitrogen injection pipeline, connected in series with a first electrically controlled proportional control valve. This allows for uniform or gradient pressurization, avoiding the pressure jumps caused by traditional on / off valves. The main nitrogen injection pipeline branches into a nitrogen injection branch and a pressure relief branch. The nitrogen injection branch connects to the nitrogen injection borehole for injecting nitrogen into the coal seam, while the pressure relief branch connects in series with a second electrically controlled proportional control valve, enabling uniform pressure relief and further preventing damage to the sealing structure from sudden pressure drops.

[0017] The extraction boreholes are set up in conjunction with the nitrogen injection boreholes to extract the gas displaced by nitrogen. The extraction branch pipes connected to the extraction boreholes are then connected to the main extraction pipeline to achieve centralized extraction and transportation of gas.

[0018] The sensing and monitoring unit includes a pressure monitoring element and a gas monitoring element. The pressure monitoring element is used to collect nitrogen injection pressure data in real time to provide a basis for pressure feedback control. The gas monitoring element is used to collect multi-parameter data such as concentration, flow rate, and pressure during the gas extraction process to provide support for nitrogen injection effect evaluation.

[0019] The intelligent control unit includes a controller, which receives data collected by the sensing and monitoring unit, executes preset control logic, controls the operating status of components such as solenoid valves and electronically controlled proportional regulating valves in the downhole execution unit, and realizes automated control of the nitrogen injection process.

[0020] The wellhead monitoring platform is interconnected with the controller and has functions for parameter setting, effect diagnosis and strategy distribution. Staff can remotely set parameters such as nitrogen injection mode and pressure upper and lower limits through the wellhead monitoring platform. The platform diagnoses the nitrogen injection effect based on the collected multi-parameter data and dynamically distributes control strategies to achieve intelligent management.

[0021] As a preferred option, the flow splitting structure adopts a first three-way flow splitter. The nitrogen generator splits into two pressure branches through the first three-way flow splitter: a high-pressure branch connected to the booster pump and a low-pressure branch that directly delivers nitrogen. The high-pressure branch is connected in series with a first solenoid valve, and the low-pressure branch is connected in series with a second solenoid valve. The first and second solenoid valves are linked and controlled by a first relay to ensure that the high-pressure branch and the low-pressure branch will not be connected at the same time, thus ensuring stable system pressure.

[0022] The nitrogen injection branch is connected in series with a third solenoid valve to control the on / off state of the nitrogen injection branch; the pressure relief branch includes a first pressure relief branch and a second pressure relief branch. The first pressure relief branch is connected in series with a fourth solenoid valve and then leads to the roadway atmosphere. The second pressure relief branch is connected in series with a fifth solenoid valve and a second electrically controlled proportional regulating valve and then leads to the roadway atmosphere. The third solenoid valve is linked with the fourth and fifth solenoid valves through a second relay to realize intelligent switching between nitrogen injection and pressure relief, avoiding pressure conflicts during nitrogen injection.

[0023] A pressure relief valve and an intelligent digital display pressure gauge are connected in series on the nitrogen injection branch. The pressure relief valve is used to automatically release pressure when the pipeline pressure is abnormally high, protecting the pipeline and equipment. The intelligent digital display pressure gauge, as a pressure monitoring element, can not only collect nitrogen injection pressure data in real time, but also has pressure upper and lower limit setting and signal triggering functions. The signal triggering time can be set, and it can directly send a switch signal to the controller to trigger nitrogen injection start and stop and parameter adjustment, improving the control response speed.

[0024] The gas monitoring element includes a multi-parameter gas monitoring sensor and a pressure gauge; the multi-parameter gas monitoring sensor includes a first multi-parameter gas monitoring sensor and a second multi-parameter gas monitoring sensor; the pressure gauge includes a first pressure gauge and a second pressure gauge. The corresponding multi-parameter gas monitoring sensor, the corresponding pressure gauge, and a sixth or seventh solenoid valve are connected in series on the extraction branch pipe. The multi-parameter gas monitoring sensor synchronously monitors the gas concentration and flow data, and the pressure gauge monitors the pressure data of the extraction pipeline, so as to realize the comprehensive perception of the gas extraction status.

[0025] The intelligent control unit also includes an underground monitoring substation and an explosion-proof power supply. The underground execution unit and sensor monitoring unit are all connected to the underground monitoring substation. The underground monitoring substation is responsible for aggregating sensor data and transmitting it to the controller, while simultaneously distributing control commands from the controller to each execution component. The explosion-proof power supply provides power to all underground equipment, meeting underground explosion-proof safety requirements. The controller is preferably a PLC (Programmable Logic Controller), possessing logic operation and data processing capabilities, and can flexibly adapt to different control strategies.

[0026] The number of nitrogen injection boreholes is set according to the actual conditions of the downhole working face. Each nitrogen injection borehole is configured with at least two extraction boreholes to ensure that the nitrogen injection displacement effect can be fully evaluated. The extraction main pipeline is connected in series with an automatic water drainer and a gas extraction pump. The automatic water drainer is used to separate water from the gas to prevent water from affecting the operation of the gas extraction pump. The gas extraction pump provides power for gas extraction.

[0027] The sealing sections of nitrogen injection boreholes and extraction boreholes are located between the elastic zone and the original stress zone of the stress concentration area. The stress environment at this location is stable. Combined with the stable pressure control of this system, the sealing performance and stability of the sealing structure can be further improved, and nitrogen leakage can be reduced.

[0028] This invention also provides a control method for the above-mentioned system, including steps such as system initialization, mode execution, data acquisition, adaptive pulse nitrogen injection, multi-parameter closed-loop control, and personalized management.

[0029] S1: System initialization, the well monitoring platform sets the nitrogen injection mode parameters. The nitrogen injection modes include low-pressure continuous nitrogen injection mode, high-pressure continuous nitrogen injection mode and high-low pressure pulse cycle step nitrogen injection mode. At the same time, the pressure upper and lower limits, duration and other parameters corresponding to each mode are set.

[0030] S2: The downhole execution unit operates according to the set mode, controls the on and off of the solenoid valve group through the relay group, switches the corresponding pressure branch, and combines the opening adjustment of the first and second solenoid proportional regulating valves to achieve uniform pressurization or gradient pressurization to avoid pressure shock.

[0031] S3: The sensor monitoring unit collects data such as nitrogen injection pressure, gas concentration, flow rate, and extraction pressure in real time, and uploads them to the intelligent control unit and the surface monitoring platform via the downhole monitoring substation;

[0032] S4: Adaptive Pulse Nitrogen Injection Based on Nitrogen Injection Pressure Feedback: When the intelligent digital pressure gauge detects that the pressure has reached the preset upper limit, the controller controls the closure of the third solenoid valve corresponding to the nitrogen injection branch and the opening of the fourth and fifth solenoid valves corresponding to the pressure relief branch. The pressure relief rate is adjusted through the second electronically controlled proportional regulating valve to achieve uniform pressure relief. When the pressure drops to the preset lower limit, the controller controls the closure of the fourth and fifth solenoid valves and the opening of the third solenoid valve to resume nitrogen injection. The controller also analyzes the pressure decay rate. If the decay rate is fast, it indicates poor sealing quality, and the upper limit of the pressure for the next cycle is adaptively lowered. If the decay is too slow and the extraction effect is not as expected, the upper limit of the pressure is appropriately increased or the pulse cycle is shortened to achieve parameter self-optimization.

[0033] S5: Closed-loop control of gas extraction effect based on multi-parameter feedback: The well monitoring platform has a built-in expert rule base. Based on the changes in gas concentration, flow rate, and pressure, it diagnoses the nitrogen injection effect, specifically including five typical situations and corresponding control strategies: Situation 1: The gas concentration drops sharply and remains at a low concentration. After the extraction pipeline is closed, the pressure rises rapidly, which is determined to be nitrogen crossflow. At this time, the nitrogen injection pressure should be reduced or the nitrogen injection time should be shortened to prevent nitrogen from directly entering the extraction pipeline; Situation 2: The gas concentration drops slowly and remains at a moderate concentration. After the extraction pipeline is closed, the pressure rises slowly and the fluctuation is ≤0.2MPa, which is determined to be a moderate displacement effect. The injection pressure should be increased. Nitrogen pressure, to enhance displacement; Scenario 3: Gas concentration continues to decrease, and the pressure remains basically unchanged and low after the extraction pipeline is closed, indicating low gas content. Nitrogen injection resources for this borehole can be reduced to avoid resource waste; Scenario 4: Gas concentration fluctuates and decreases, and the flow rate fluctuates. After the extraction pipeline is closed, the pressure fluctuates drastically, indicating leakage in the sealing borehole. Nitrogen injection pressure should be reduced or the sealing borehole should be filled to restore sealing performance; Scenario 5: Gas concentration decreases rapidly and the flow rate decreases synchronously. After the extraction pipeline is closed, the pressure rises and then falls rapidly, indicating blockage of the displacement path. High-pressure pulse mode should be switched and the number of pulses increased to clear coal seam fractures;

[0034] S6: Establish an independent file for each nitrogen injection borehole, recording its geological information, borehole sealing quality assessment results (calculated based on pressure decay rate), historical nitrogen injection parameters, and extraction response characteristics. Based on the file, the well monitoring platform assigns differentiated nitrogen injection modes, pressure limits, and pulse frequencies to each borehole, achieving personalized control with "one policy per borehole" and maximizing the extraction potential of each borehole.

[0035] The specific execution process of the low-pressure continuous nitrogen injection mode is as follows: open the second solenoid valve corresponding to the low-pressure branch, close the first solenoid valve corresponding to the high-pressure branch, adjust the opening of the first electronically controlled proportional regulating valve, so that the nitrogen injection pressure rises steadily to the target value and remains stable. It is suitable for scenarios with shallow gas content and average sealing quality.

[0036] The specific execution process of the high-pressure continuous nitrogen injection mode is as follows: open the first solenoid valve corresponding to the high-pressure branch and close the second solenoid valve corresponding to the low-pressure branch. After the nitrogen is boosted by the booster pump, it is adjusted by the first electronically controlled proportional regulating valve to make the pressure rise steadily to the target high-pressure value and maintain it. It is suitable for low-permeability coal seams and deep gas occurrence scenarios.

[0037] The specific execution process of the high-low pressure pulse cyclic stepped nitrogen injection mode is as follows: High-pressure nitrogen injection stage: Open the first solenoid valve and close the second solenoid valve. Adjust the first electronically controlled proportional regulating valve to raise the pressure to the upper limit of high pressure and maintain it for a set time. Use high-pressure nitrogen to clear coal seam fractures and displace gas. High-pressure depressurization stage: Close the third solenoid valve and open the fourth and fifth solenoid valves. Adjust the second electronically controlled proportional regulating valve to lower the pressure to the lower limit of low pressure at a uniform rate to avoid damage to the sealing structure from a sudden pressure drop. Low-pressure nitrogen injection stage: Open the second solenoid valve and close the first solenoid valve. Maintain it for a set time and use low-pressure nitrogen to supplement displacement and expand the displacement range. Then repeat the high-pressure nitrogen injection stage to form a cycle, which is suitable for gas extraction under complex geological conditions.

[0038] The beneficial effects of this invention are:

[0039] Compared with the prior art, the advantages of this invention are:

[0040] 1. Protection of equipment and sealing structure: The combination of multi-pressure branch interlocking architecture and electronically controlled proportional regulating valve achieves uniform pressurization and depressurization, completely avoiding the pressure step impact caused by traditional switching valves. This reduces start-up and shutdown losses of equipment such as nitrogen generators and booster pumps, extends equipment service life, protects the integrity of the sealing structure, and reduces the risk of nitrogen leakage. The sealing section is arranged in a stress-stable area, further improving the reliability of the sealing.

[0041] 2. Improve the level of intelligent control: Construct a dual closed-loop control system of pressure feedback and gas extraction multi-parameter feedback. Based on pressure feedback, realize adaptive pulse nitrogen injection, and based on gas multi-parameter feedback, realize dynamic control of effect, get rid of dependence on manual experience, and realize the automation of nitrogen injection process;

[0042] 3. Achieve precise and differentiated control: Establish an independent file for each nitrogen injection borehole, and formulate personalized nitrogen injection strategies based on differences in sealing quality, geological conditions, and gas occurrence status, avoiding the extensive "one-size-fits-all" approach, maximizing the gas extraction potential of each borehole, and improving overall extraction efficiency.

[0043] 4. Optimize gas displacement effect: Stable pressure changes promote uniform nitrogen permeation in the coal seam, fully desorb adsorbed gas in micropores, expand the effective displacement range, and, combined with precise control of multi-parameter feedback, significantly improve gas displacement efficiency and extraction effect, helping the efficient and green development of coalbed methane and aligning with dual carbon targets. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0045] Figure 2 This is a partial structural schematic diagram of the present invention;

[0046] Figure 3 This is a simplified structural diagram of the present invention;

[0047] Figure 4 This is a schematic diagram of the nitrogen injection pressure-time curve in the low-pressure continuous nitrogen injection mode of the present invention;

[0048] Figure 5 This is a schematic diagram of the nitrogen injection pressure-time curve for the high-pressure continuous nitrogen injection mode of the present invention;

[0049] Figure 6 This is a schematic diagram of the nitrogen injection pressure-time curve of the high and low pressure pulse cyclic step nitrogen injection mode of the present invention.

[0050] In the diagram: 1. Nitrogen generator; 2. Booster pump; 3. Nitrogen injection manifold; 4. Main extraction pipeline; 5. Nitrogen injection borehole; 6. Extraction borehole; 7-1. First solenoid valve; 7-2. Second solenoid valve; 7-3. Third solenoid valve; 7-4. Fourth solenoid valve; 7-5. Fifth solenoid valve; 7-6. Sixth solenoid valve; 7-7. Seventh solenoid valve; 8-1. First relay; 8-2. Second relay; 8-3. Third relay; 9-1. First electronic control unit. Example: Control valve; 9-2, Second electrically controlled proportional control valve; 10-1, First gas multi-parameter monitoring sensor; 10-2, Second gas multi-parameter monitoring sensor; 11, Intelligent digital display pressure gauge; 12-1, First pressure gauge; 12-2, Second pressure gauge; 13, Pressure relief valve; 14, Downhole monitoring substation; 15, Explosion-proof power supply; 16, Controller; 17, Surface monitoring platform; 18, Gas drainage pump; 19, Automatic water drainer; 20, Sealing section. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] like Figure 1-3 As shown, the present invention provides a technical solution: a coal seam nitrogen injection intelligent linkage control system based on multi-parameter feedback, including a downhole execution unit, a sensing and monitoring unit, an intelligent control unit and a surface monitoring platform 17.

[0053] In the downhole execution unit, nitrogen generator 1 branches into two pressure branches via a first three-way distributor. The first branch connects to booster pump 2 and is connected in series with first solenoid valve 7-1, forming a high-pressure branch. The second branch is connected in series with second solenoid valve 7-2, forming a low-pressure branch. First solenoid valve 7-1 and second solenoid valve 7-2 are linked and controlled by first relay 8-1 to ensure that only one branch is active at any given time. The two branches are merged into a nitrogen injection main pipeline via a first three-way manifold, connected in series with first electrically controlled proportional regulating valve 9-1 to achieve uniform or gradient pressurization.

[0054] The main nitrogen injection line branches into a nitrogen injection branch and a first pressure relief branch via a second three-way diverter. The nitrogen injection branch is connected in series with a third solenoid valve 7-3 and then to nitrogen injection borehole 5. The first pressure relief branch is connected in series with a fourth solenoid valve 7-4 and then to the roadway atmosphere. The nitrogen injection branch branches into a second pressure relief branch via a third three-way diverter. The second pressure relief branch is connected in series with a fifth solenoid valve 7-5 and a second electrically controlled proportional regulating valve 9-2 and then to the roadway atmosphere for uniform pressure relief.

[0055] A pressure relief valve 13 and a smart digital pressure gauge 11 are connected in series on the nitrogen injection branch. The pressure relief valve 13 is used for pipeline overpressure protection, and the smart digital pressure gauge 11 is used to monitor the nitrogen injection pressure in real time and trigger control signals. The third solenoid valve 7-3 is linked with the fourth solenoid valve 7-4 and the fifth solenoid valve 7-5 through the second relay 8-2, and the smart digital pressure gauge 11 is linked with the third solenoid valve 7-3 through the third relay 8-3, realizing intelligent switching between nitrogen injection and pressure relief.

[0056] The number of nitrogen injection boreholes 5 is determined according to the actual conditions of the downhole working face. Each nitrogen injection borehole 5 has a corresponding extraction borehole 6 on both sides. A sixth solenoid valve 7-6 or a seventh solenoid valve 7-7, a first gas multi-parameter monitoring sensor 10-1 or a second gas multi-parameter monitoring sensor 10-2, and a first pressure gauge 12-1 or a second pressure gauge 12-2 are connected in series on the extraction branch pipes. All extraction branch pipes are then connected to the main extraction pipeline 4. The main extraction pipeline 4 is connected in series with an automatic water drainer 19 and a gas extraction pump 18 to complete gas extraction and transportation. The sealing sections 20 of the nitrogen injection boreholes 5 and extraction boreholes 6 are arranged between the elastic zone and the original stress zone of the stress concentration area to improve sealing stability.

[0057] The sensing and monitoring unit includes an intelligent digital display pressure gauge 11, a first gas multi-parameter monitoring sensor 10-1, a second gas multi-parameter monitoring sensor 10-2, a first pressure gauge 12-1, and a second pressure gauge 12-2. Each sensor collects data such as nitrogen injection pressure, gas concentration, flow rate, and extraction pressure in real time, and transmits them to the controller 16 via the downhole monitoring substation 14.

[0058] The intelligent control unit includes an underground monitoring substation 14, an explosion-proof power supply 15, and a mining intrinsically safe PLC programmable logic controller 16. The explosion-proof power supply 15 supplies power to all underground equipment. The underground monitoring substation 14 realizes data aggregation and instruction distribution. The controller 16 executes control logic and interconnects with the surface monitoring platform 17 to realize remote monitoring and control.

[0059] The control method of this system includes the following steps:

[0060] S1: System initialization, well monitoring platform 17 sets nitrogen injection mode parameters. Nitrogen injection modes include low-pressure continuous nitrogen injection mode, high-pressure continuous nitrogen injection mode and high-low pressure pulse cycle step nitrogen injection mode. At the same time, set the upper and lower pressure limits, duration and other parameters corresponding to each mode.

[0061] S2: The downhole execution unit operates according to the set mode, controls the on and off of the solenoid valve group through the relay group, switches the corresponding pressure branch, and combines the opening adjustment of the first electronically controlled proportional regulating valve 9-1 and the second electronically controlled proportional regulating valve 9-2 to achieve uniform pressurization or gradient pressurization and avoid pressure shock.

[0062] An example of an achievable nitrogen injection pressure loading / unloading path is as follows: Figure 4-6 As shown:

[0063] The specific execution process of the low-pressure continuous nitrogen injection mode is as follows: the second solenoid valve 7-2 is opened, the first solenoid valve 7-1 is adaptively closed through the first relay 8-1, and the pressurization time is set on the ground platform. The controller 16 adjusts the opening of the first electronically controlled proportional regulating valve 9-1 to make the nitrogen injection pressure rise steadily to the target value and remain stable, which is suitable for scenarios with shallow gas content and average sealing quality.

[0064] The specific execution process of the high-pressure continuous nitrogen injection mode is as follows: the first solenoid valve 7-1 is opened and the second solenoid valve 7-2 is closed adaptively through the first relay 8-1. After the nitrogen is boosted by the booster pump 2, it is regulated by the first electronically controlled proportional regulating valve 9-1 so that the pressure rises steadily to the target high pressure value and is maintained. This mode is suitable for low-permeability coal seams and deep gas occurrence scenarios.

[0065] The specific execution process of the high-low pressure pulse cyclic stepped nitrogen injection mode is as follows: Set the upper and lower pressure limits of the intelligent digital display pressure gauge 11, and set the step interval time. High-pressure nitrogen injection stage: Open the first solenoid valve 7-1, close the second solenoid valve 7-2, adjust the first electronically controlled proportional regulating valve 9-1 to raise the pressure to the high-pressure upper limit, maintain it for the set time, and use high-pressure nitrogen to clear coal seam fractures and displace gas; High-pressure depressurization stage: Close the third solenoid valve 7-3, open the fourth solenoid valve 7-4 and the fifth solenoid valve 7-5, adjust the second electronically controlled proportional regulating valve 9-2 to lower the pressure to the low-pressure lower limit at a uniform speed, avoiding damage to the sealing structure from a sudden pressure drop; Low-pressure nitrogen injection stage: Open the second solenoid valve 7-2, close the first solenoid valve 7-1, maintain it for the set time, and use low-pressure nitrogen to supplement displacement and expand the displacement range; Then repeat the high-pressure nitrogen injection stage to form a cycle, which is suitable for gas extraction under complex geological conditions;

[0066] S3: The sensing and monitoring unit collects data such as nitrogen injection pressure, gas concentration, flow rate, and extraction pressure in real time, and uploads them to the intelligent control unit and the surface monitoring platform 17 via the downhole monitoring substation 14;

[0067] S4: Adaptive Pulse Nitrogen Injection Based on Nitrogen Injection Pressure Feedback: When the intelligent digital display pressure gauge 11 detects that the pressure has reached the preset upper limit, the controller 16 controls the closure of the third solenoid valve 7-3 corresponding to the nitrogen injection branch and the opening of the fourth solenoid valve 7-4 and the fifth solenoid valve 7-5 corresponding to the pressure relief branch. The pressure relief rate is adjusted by the second electronically controlled proportional regulating valve 9-2 to achieve uniform pressure relief. When the pressure drops to the preset lower limit, the controller 16 controls the closure of the fourth solenoid valve 7-4 and the fifth solenoid valve 7-5 and the opening of the third solenoid valve 7-3 to resume nitrogen injection. The controller 16 also analyzes the pressure decay rate. If the decay rate is fast, it indicates that the sealing quality is poor, and the upper limit of the pressure in the next cycle is adaptively lowered. If the decay is too slow and the extraction effect is not as expected, the upper limit of the pressure is appropriately increased or the pulse cycle is shortened to achieve parameter self-optimization.

[0068] S5: Closed-loop control of gas extraction effect based on multi-parameter feedback: The well monitoring platform 17 has a built-in expert rule base. Based on the changes in gas concentration, flow rate, and pressure, it diagnoses the nitrogen injection effect, specifically including five typical situations and corresponding control strategies: Situation 1: The gas concentration drops sharply and remains at a low concentration. After the extraction pipeline is closed, the pressure rises rapidly, which is determined to be nitrogen cross-flow. At this time, the nitrogen injection pressure should be reduced or the nitrogen injection time should be shortened to prevent nitrogen from directly entering the extraction pipeline; Situation 2: The gas concentration drops slowly and remains at a moderate concentration. After the extraction pipeline is closed, the pressure rises slowly and the fluctuation is ≤0.2MPa, which is determined to be a general displacement effect. The pressure should be increased. Nitrogen injection pressure to enhance displacement; Scenario 3: Gas concentration continues to decrease, and the pressure remains basically unchanged and low after the extraction pipeline is closed, indicating low gas content. Nitrogen injection resources for this borehole can be reduced to avoid resource waste; Scenario 4: Gas concentration fluctuates and decreases, and the flow rate fluctuates. After the extraction pipeline is closed, the pressure fluctuates drastically, indicating leakage in the sealing borehole. Nitrogen injection pressure should be reduced or the sealing borehole should be filled to restore sealing performance; Scenario 5: Gas concentration decreases rapidly and the flow rate decreases synchronously. After the extraction pipeline is closed, the pressure rises and then falls rapidly, indicating blockage of the displacement path. The high-pressure pulse mode should be switched and the number of pulses increased to clear coal seam fractures;

[0069] S6: Establish an independent file for each nitrogen injection borehole 5, recording its geological information, borehole sealing quality assessment results (calculated based on pressure decay rate), historical nitrogen injection parameters, and extraction response characteristics. Based on the file, the well monitoring platform 17 assigns differentiated nitrogen injection modes, pressure limits, and pulse frequencies to each borehole, achieving personalized control with "one policy per borehole" and maximizing the extraction potential of each borehole.

[0070] This invention addresses many shortcomings of existing technologies through hardware architecture innovation and software logic optimization, improving the intelligence level and extraction efficiency of coal seam nitrogen injection for gas displacement, and has significant practical value and promotional significance.

[0071] Although specific embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for intelligent linkage control of nitrogen injection in coal seams based on multi-parameter feedback, characterized in that, This includes an intelligent linkage control system for nitrogen injection into coal seams based on multi-parameter feedback; The system includes an underground execution unit, a sensor monitoring unit, an intelligent control unit, and an above-ground monitoring platform (17). The underground execution unit and the sensor monitoring unit are interconnected with the intelligent control unit and the above-ground monitoring platform (17) through the mining industrial ring network. The downhole execution unit includes a nitrogen generator (1), a booster pump (2), a nitrogen injection borehole (5), a extraction borehole (6), a solenoid valve group, a relay group, an electronically controlled proportional regulating valve group, and an extraction main pipeline (4). The nitrogen generator (1) branches into at least two pressure branches through a diversion structure. Each pressure branch is interlocked with the solenoid valve group through the relay group to ensure that a single pressure branch is open. The pressure branches converge to form a nitrogen injection main pipeline. The nitrogen injection main pipeline is connected in series with a first electronically controlled proportional regulating valve (9-1). The nitrogen injection main pipeline branches into a nitrogen injection branch and a pressure relief branch. The nitrogen injection branch is connected to the nitrogen injection borehole (5). The pressure relief branch is connected in series with a second electronically controlled proportional regulating valve (9-2). The extraction borehole (6) is set in correspondence with the nitrogen injection borehole (5). The extraction branch pipes connected to the extraction borehole (6) are connected to the extraction main pipeline (4) after being aggregated. The control method includes the following steps: S1: System initialization, well monitoring platform (17) sets nitrogen injection mode parameters, the nitrogen injection mode includes low pressure continuous nitrogen injection mode, high pressure continuous nitrogen injection mode and high and low pressure pulse cycle step nitrogen injection mode; S2: The downhole execution unit controls the on / off of the solenoid valve group through the relay group according to the set mode, and achieves uniform pressurization or gradient pressurization in combination with the first electrically controlled proportional regulating valve (9-1) and the second electrically controlled proportional regulating valve (9-2); S3: The sensing and monitoring unit collects nitrogen injection pressure and gas extraction multi-parameter data in real time and uploads them to the intelligent control unit and the well monitoring platform (17). S4: Adaptive pulse nitrogen injection based on nitrogen injection pressure feedback: When the pressure monitoring element detects that the pressure has reached the preset upper limit, the third solenoid valve (7-3) is closed, and the fourth solenoid valve (7-4) and the fifth solenoid valve (7-5) are opened. Uniform pressure relief is achieved through the second electronically controlled proportional regulating valve (9-2); when the pressure drops to the preset lower limit, the fourth solenoid valve (7-4) and the fifth solenoid valve (7-5) are closed, and the third solenoid valve (7-3) is opened to resume nitrogen injection; by analyzing the pressure decay rate, the upper limit of the pressure in the next cycle is adaptively adjusted. S5: Closed-loop control of gas extraction effect based on multi-parameter feedback: The well monitoring platform (17) has a built-in expert rule base, which diagnoses the nitrogen injection effect based on the characteristics of gas concentration, flow rate and pressure changes, and dynamically adjusts the nitrogen injection parameters; The nitrogen injection effect diagnosis and control strategies include: Scenario 1: The gas concentration drops sharply and remains at a low level. After the extraction pipeline is shut down, the pressure rises rapidly. This is determined to be nitrogen crossflow. Reduce the nitrogen injection pressure or shorten the nitrogen injection time. Scenario 2: The gas concentration decreases slowly and remains at a moderate level. After the extraction pipeline is shut down, the pressure rises slowly and fluctuates by ≤0.2MPa. This indicates that the displacement effect is average, and the nitrogen injection pressure should be increased. Scenario 3: The gas concentration continues to decrease, and the pressure remains basically unchanged and low after the extraction pipeline is shut down. This indicates that the gas content is low, and nitrogen injection resources should be reduced. Scenario 4: Gas concentration fluctuates and decreases, and flow rate fluctuates. After shutting down the extraction pipeline, the pressure fluctuates drastically. This is determined to be a leak in the sealing hole. Reduce the nitrogen injection pressure or fill the sealing hole. Scenario 5: The gas concentration drops rapidly and the flow rate drops simultaneously. After the extraction pipeline is shut down, the pressure rises and then drops rapidly. This is determined to be a blockage in the displacement path. Switch to high-pressure pulse mode and increase the number of pulses. S6: Establish an independent file for each nitrogen injection borehole (5) to record geological information, borehole sealing quality assessment results and historical nitrogen injection parameters.

2. The intelligent linkage control method for coal seam nitrogen injection based on multi-parameter feedback according to claim 1, characterized in that, The sensing and monitoring unit includes a pressure monitoring element for collecting nitrogen injection pressure and a gas monitoring element for collecting gas extraction parameters. The intelligent control unit includes a controller (16) for receiving data collected by the sensing and monitoring unit and controlling the operation of the downhole execution unit; The well monitoring platform (17) is interconnected with the controller (16) for parameter setting, effect diagnosis and strategy distribution.

3. The intelligent linkage control method for coal seam nitrogen injection based on multi-parameter feedback as described in claim 1, characterized in that, The diversion structure is a first three-way diverter. The nitrogen generator (1) splits into two pressure branches through the first three-way diverter, namely a high-pressure branch connected to the booster pump (2) and a low-pressure branch that directly delivers nitrogen. The high-pressure branch is connected in series with a first solenoid valve (7-1), and the low-pressure branch is connected in series with a second solenoid valve (7-2). The first solenoid valve (7-1) and the second solenoid valve (7-2) are linked and controlled by a first relay (8-1). The nitrogen injection branch is connected in series with a third solenoid valve (7-3). The pressure relief branch includes a first pressure relief branch and a second pressure relief branch. The first pressure relief branch is connected in series with a fourth solenoid valve (7-4) and then leads to the roadway atmosphere. The second pressure relief branch is connected in series with a fifth solenoid valve (7-5) and a second electronically controlled proportional regulating valve (9-2) and then leads to the roadway atmosphere. The third solenoid valve (7-3) is linked and controlled by a second relay (8-2) with a fourth solenoid valve (7-4) and a fifth solenoid valve (7-5).

4. The intelligent linkage control method for coal seam nitrogen injection based on multi-parameter feedback as described in claim 3, characterized in that, The nitrogen injection branch is also connected in series with a pressure relief valve (13) and an intelligent digital display pressure gauge (11). The intelligent digital display pressure gauge (11) is the pressure monitoring element, which has the functions of setting upper and lower pressure limits and signal triggering. The signal triggering time can be set, and it is linked with the third solenoid valve (7-3) through the third relay (8-3).

5. The intelligent linkage control method for coal seam nitrogen injection based on multi-parameter feedback according to claim 2, characterized in that, The gas monitoring element includes a gas multi-parameter monitoring sensor and a pressure gauge; the gas multi-parameter monitoring sensor is used to monitor gas concentration and flow rate, and includes a first gas multi-parameter monitoring sensor (10-1) and a second gas multi-parameter monitoring sensor (10-2); the pressure gauge is used to monitor the pressure of the extraction pipeline, and includes a first pressure gauge (12-1) and a second pressure gauge (12-2); the corresponding gas multi-parameter monitoring sensor, the corresponding pressure gauge, and a sixth solenoid valve (7-6) or a seventh solenoid valve (7-7) are connected in series on the extraction branch pipe.

6. The intelligent linkage control method for coal seam nitrogen injection based on multi-parameter feedback according to claim 2, characterized in that, The intelligent control unit also includes a downhole monitoring substation (14) and an explosion-proof power supply (15). The downhole execution unit and the sensing and monitoring unit are connected to the downhole monitoring substation (14). The explosion-proof power supply (15) supplies power to each device. The controller (16) is a programmable logic controller that interacts with the downhole monitoring substation (14) for data exchange.

7. The intelligent linkage control method for coal seam nitrogen injection based on multi-parameter feedback according to claim 1, characterized in that, The number of nitrogen injection boreholes (5) is set according to the actual situation of the downhole working face, and each nitrogen injection borehole (5) is configured with at least two extraction boreholes (6). The extraction main pipeline (4) is connected in series with an automatic water drainer (19) and a gas extraction pump (18). The sealing sections (20) of the nitrogen injection boreholes (5) and extraction boreholes (6) are arranged between the elastic zone and the original stress zone of the stress concentration zone.

8. The intelligent linkage control method for coal seam nitrogen injection based on multi-parameter feedback according to claim 1, characterized in that, In step S2: The low-pressure continuous nitrogen injection mode uses the second solenoid valve (7-2) to open, the first solenoid valve (7-1) to close, and the first electronically controlled proportional regulating valve (9-1) to adjust the pressure to rise steadily to the target value and maintain it. The high-pressure continuous nitrogen injection mode opens the first solenoid valve (7-1), closes the second solenoid valve (7-2), and after being pressurized by the booster pump (2), the first electronically controlled proportional regulating valve (9-1) is adjusted to make the pressure rise steadily to the target value and maintain it. The high-low pressure pulse cyclic step nitrogen injection mode includes: High-pressure nitrogen injection stage: Open the first solenoid valve (7-1), close the second solenoid valve (7-2), adjust the first electronically controlled proportional regulating valve (9-1) to raise the pressure to the high-pressure upper limit, and maintain it for the set time; High pressure relief stage: Close the third solenoid valve (7-3), open the fourth solenoid valve (7-4) and the fifth solenoid valve (7-5), and adjust the second electronically controlled proportional regulating valve (9-2) to reduce the pressure to the lower limit of low pressure; Low-pressure nitrogen injection stage: Open the second solenoid valve (7-2), close the first solenoid valve (7-1), maintain for the set time, and then repeat the high-pressure nitrogen injection stage to form a cycle.

9. The intelligent linkage control method for coal seam nitrogen injection based on multi-parameter feedback according to claim 1, characterized in that, In step S4, the pressure decay rate is used to evaluate the sealing quality. If the decay rate is too fast, the upper limit of the pressure for the next cycle is lowered. If the decay is too slow and the extraction effect does not meet expectations, the upper limit of the pressure is increased or the pulse cycle is shortened.

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