Deep well long-life drainage gas recovery system and ground power device and control method thereof

Abstract

The invention discloses a deep well long-life drainage gas production system and a ground power device and a control method thereof, and relates to the technical field of drainage gas production of natural gas and coal rock gas. The deep well long-life drainage gas production system comprises an underground pump set and a ground power device connected with the underground pump set. The ground power device comprises a water tank for storing power liquid and a power pump connected with the water tank and used for pressurizing the power liquid; the ground power device further comprises a motor, and the motor is connected with the power pump through a belt and used for driving the power pump to rotate so as to pressurize the power liquid in the water tank and provide power. The motor is a variable-frequency reluctance motor or a variable-frequency permanent magnet motor. The control method comprises the steps of monitoring the number of rotation turns of the motor, and performing motor speed reduction and system reversing based on the number of rotation turns. Flexible reversing control in a power system is achieved, impact on quick-wear parts is effectively avoided, and the flexible reversing valve has the advantages of being simple in structure, low in cost, long in service life and low in maintenance cost.

Description

Technical Field

[0001] This invention relates to the field of natural gas and coal rock gas drainage and gas production technology, and in particular to a deep well long-life drainage and gas production system and its surface power unit and control method. Background Technology

[0002] In the middle and later stages of their production lifecycle, deep coalbed methane and natural gas wells commonly face the problem of declining formation pressure and increased water production leading to wellbore fluid accumulation. This fluid accumulation increases bottom hole back pressure, reduces the production pressure differential, and lowers gas production efficiency. Therefore, it is necessary to remove the bottom hole fluid through artificial lifting to achieve normal gas production from deep coalbed methane.

[0003] Under normal circumstances, to drive the downhole pump set motor plunger for production without contact between the power fluid and the produced fluid, two non-interfering power fluid lines are required to achieve the up and down strokes of the downhole pump set motor plunger. This makes the surface power reversing device more complex and increases the energy consumption of the system. In addition, existing equipment cannot precisely control the flow rate of high-pressure power fluid during reversing, and cannot achieve flexible reversing. This causes significant impact on valves, pipelines, and downhole tubing in the hydraulic circuit, greatly shortening their service life.

[0004] Therefore, the applicant intends to provide a surface power unit and control method for a deep well long-life drainage and gas production system to meet the needs of natural gas and deep coal and rock gas drainage and production. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a deep well long-life drainage gas production system, its surface power unit, and control method, thereby solving the problems of complex surface power units, short service life, and large pipeline impacts in the drainage gas production process of deep coal rock gas or natural gas.

[0006] To achieve the above objectives, the present invention provides the following solutions: A surface power unit for a deep well long-life drainage and gas production system is disclosed. The surface power unit is connected to a downhole pump unit and is used to drive the motor plunger of the downhole pump unit during the drainage of natural gas or deep coal and rock gas, thereby realizing the drainage process of the downhole pump unit. The surface power unit includes a water tank for storing power fluid and a power pump connected to the water tank and pressurizing the power fluid. Its unique feature is that the surface power unit also includes a motor, which is connected to the power pump via a belt and is used to drive the power pump to rotate, thereby pressurizing and providing power to the power fluid in the water tank. The motor is a variable frequency reluctance motor or a variable frequency permanent magnet motor.

[0007] As a preferred embodiment, the power pump is a three-cylinder plunger pump, and an accumulator is installed on its outlet pipe.

[0008] As a preferred embodiment, the outlet of the water tank is connected to the inlet of the power pump via a pipeline. The outlet of the power pump is divided into two lines: a supply pipeline A and a supply pipeline B. The end of the supply pipeline A furthest from the power pump is connected to the lower end of the motor plunger of the downhole pump unit. The end of the supply pipeline B furthest from the power pump is connected to the upper end of the motor plunger of the downhole pump unit. A branch is provided on the supply pipeline A as a return pipeline B, and the end of the return pipeline B furthest from the supply pipeline A is connected to the return port of the water tank, so that the downhole pump unit is connected to the return port of the water tank through the return pipeline B. A branch is provided on the supply pipeline B as a return pipeline A, and the end of the return pipeline A furthest from the supply pipeline B is connected to the return port of the water tank, so that the downhole pump unit is connected to the return port of the water tank through the return pipeline A.

[0009] As a preferred embodiment, the ground power unit further includes: An electromagnetic reversing valve is installed at the outlet of the power pump and connected to the power pump through a pipeline, dividing the outlet of the power pump into two paths; the inlet of the electromagnetic reversing valve is connected to the outlet of the power pump, and there are two outlets, which are respectively connected to the supply pipeline A and the supply pipeline B. Two check valves are provided, one of which is located on the liquid supply line A and between the solenoid directional valve and the return line B, and the other is located on the liquid supply line B and between the solenoid directional valve and the return line A. A speed sensor is mounted on the motor.

[0010] As a preferred embodiment, the electromagnetic directional valve is a three-way electromagnetic directional valve, which includes one inlet and two outlets; the inlet of the three-way electromagnetic directional valve is connected to the outlet of the power pump, and the two outlets are respectively connected to supply line A and supply line B; or, the electromagnetic directional valve is two two-position two-way electromagnetic switching valves, the inlets of the two two-position two-way electromagnetic switching valves are both connected to the outlet of the power pump, and the outlets are respectively connected to supply line A and supply line B.

[0011] As a preferred embodiment, the ground power unit further includes: A first pressure sensor is disposed between the power pump and the solenoid directional valve; The second pressure sensor and the first flow sensor are installed on the liquid supply line A. The third pressure sensor and the second flow sensor are installed on the liquid supply line B; The top stroke return water valve is installed on the return liquid line A and is used to control the opening and closing of the return liquid line A; The downstroke return water valve is installed on the return liquid line B and is used to control the opening and closing of the return liquid line B. The return water flow meter is installed on the return liquid line A and is located on the pipeline between the upper stroke return water valve and the supply liquid line B.

[0012] Furthermore, both the upper stroke return valve and the lower stroke return valve are two-position two-way solenoid valves.

[0013] As a preferred embodiment, the ground power unit further includes: An automatic vent valve is installed on the liquid supply line B to discharge gas from the downhole pump unit connected to the liquid supply line B. A spring-reset safety valve is installed on the pipeline between the first pressure sensor and the power pump; A pressure gauge is installed on the pipeline between the spring-reset safety valve and the first pressure sensor.

[0014] The present invention also provides a deep well long-life drainage and gas production system, including a downhole pump set for drainage and gas production and a surface power unit connected to the downhole pump set, wherein the surface power unit is the aforementioned surface power unit.

[0015] This invention also provides a control method for the aforementioned deep well long-life drainage and gas production system, which is characterized by including the following steps: 1) Before using the aforementioned surface power unit for drainage, the total volume V of the discharged fluid discharged by the downhole pump unit in one upstroke is determined through preliminary tests. T1 and the corresponding number of motor rotations C T1 The total volume V of the discharged fluid in one downstroke T2 and the corresponding number of motor rotations C T2 ; 2) When using the ground power unit for mining, monitor the number of motor rotations and switch between the upstroke and downstroke based on the number of motor rotations to achieve cyclic mining between the upstroke and downstroke; wherein, before switching between the upstroke and downstroke, the motor speed is reduced to 0~25 rpm, and after switching, the motor speed is increased to the rated speed and maintained at the rated speed. The switching criteria for the upstroke and downstroke include: If the current state is during the upstroke, monitor the number of motor revolutions during the current stroke. When the number of motor revolutions reaches (0.85~0.9)×C... T1 At this time, reduce the motor speed to 0-25 rpm, and wait until the number of motor revolutions in the current stroke reaches C. T1 At that time, switch to the downstroke; If the current state is in the downstroke, monitor the number of motor revolutions during the current stroke. When the number of motor revolutions reaches (0.85~0.9)×C... T2 At this time, reduce the motor speed to 0-25 rpm, and wait until the number of motor revolutions in the current stroke reaches C. T2 At that time, switch to the top stroke.

[0016] As a preferred embodiment, the switching between the upstroke and downstroke is achieved through an electromagnetic directional valve.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention discloses a deep well long-life drainage and gas production system, its surface power unit, and control method. It can realize the circulation drainage process of the downhole pump group using only a motor, a power pump, and connecting pipelines. Furthermore, it uses a variable frequency reluctance motor or a variable frequency permanent magnet motor to realize flexible reversing control in the hydraulic control system, effectively avoiding impact on vulnerable parts. It has the advantages of simple power system, low cost, long service life of vulnerable parts, and low maintenance cost, and is especially suitable for coal and rock gas wells and natural gas wells at depths of 2500~4000 meters.

[0018] This invention achieves the cyclic drainage process of the downhole pump unit by controlling the motor speed and the flow rate of the power pump. It features a simple structure and low energy consumption. The invention uses a variable frequency reluctance motor or a variable frequency permanent magnet motor, offering a wide speed range of >50%, capable of changing speed from 0 to rated speed, making it easy to implement and energy-efficient. The invention employs an electromagnetic directional valve for directional control. Through the action of the power pump and a check valve, the pressurized hydraulic fluid flows unidirectionally into the downhole pump unit to achieve the up and down strokes of the motor plunger. Flow sensors, pressure sensors, and speed sensors monitor the pressure, flow rate, speed of the hydraulic fluid, and the number of motor revolutions. By controlling the volume of fluid discharged during the up and down strokes of the downhole pump unit and the number of motor revolutions, the variable frequency reluctance motor or variable frequency permanent magnet motor speed is reduced. This allows for directional control using the electromagnetic directional valve, achieving flexible directional control in the hydraulic control system, avoiding pipeline impact, and extending pipeline lifespan.

[0019] This invention utilizes the pressure energy of the fluid stored in the accumulator to regulate, compensate, and protect the system's energy, thus avoiding the impact of pulsation during the plunger's suction and discharge reversal in a three-cylinder plunger power pump on the control accuracy of the power unit.

[0020] This invention uses an automatic vent valve installed on the liquid supply line B to vent gas from the double-layer tubing annular pipeline connected to the liquid supply line B. The automatic vent valve consists of a filter, an vent valve, and an electromagnetic safety valve, and the vent valve operates normally under the protection of the electromagnetic safety valve.

[0021] This invention collects relevant parameter information from pressure sensors, flow sensors, and speed sensors during the drainage process of downhole pump sets, and continuously optimizes the performance of the control system through adaptive learning. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the ground power unit of the present invention; Figure 2 This is a diagram showing the pipeline layout scheme of the ground power unit of the present invention; In the diagram: 1. Water tank; 2. Motor; 3. Power pump; 4. Accumulator; 5. Spring-return safety valve; 6. Pressure gauge; 7. First pressure sensor; 8. Solenoid directional valve; 9. Check valve; 10. First flow sensor; 11. Second pressure sensor; 12. Automatic air vent valve; 13. Second flow sensor; 14. Third pressure sensor; 15. Upstroke return water valve; 16. Return water flow meter; 17. Downstroke return water valve; 18. Downhole pump set; 19. Belt. Detailed Implementation

[0023] To better explain the present invention, the main contents of the present invention are further illustrated below with reference to specific embodiments, but the contents of the present invention are not limited to the following embodiments.

[0024] Example 1 This invention discloses a surface power unit for a deep well long-life drainage and gas production system, particularly suitable for coal-rock gas wells and natural gas wells at depths of 2500-4000 meters. The deep well long-life drainage and gas production system includes a surface power unit and a downhole pump unit 18, used for drainage and gas production of natural gas and deep coal-rock gas. The surface power unit is connected to the motor plunger of the downhole pump unit 18 via a double-layer pipeline, driving the movement of the motor plunger of the downhole pump unit 18, thereby realizing the drainage and production process of the downhole pump unit 18.

[0025] like Figures 1-2The diagram shows the surface power unit of the deep well long-life drainage gas production system of the present invention, including a water tank 1, a power pump 3 connected to the water tank 1, and a motor 2 connected to the power pump 3. The water tank 1 is used to store power fluid and recover spent power fluid. The motor 2 is connected to the power pump 3 via a belt 19; the motor 2 is a variable frequency reluctance motor or a variable frequency permanent magnet motor, used to drive the power pump 3 to rotate, thereby pressurizing and providing power to the power fluid flowing out of the water tank 1 and through the power pump 3; the motor 2 is equipped with a motor control system for controlling the operation of the motor 2. The power pump 3 is a three-cylinder plunger pump, connected to the water tank 1 via a pipeline, used to pressurize the power fluid flowing into the water tank 1, thereby providing power to the power fluid; the three-cylinder plunger pump uses ceramic plungers and a combined seal; the structure of the three-cylinder plunger pump is existing technology and will not be described in detail here. An accumulator 4 is installed on the outlet pipe of the power pump 3 to buffer the pump displacement, ensure pressure stability during the operation of the power pump 3, and achieve the functions of regulating, compensating and protecting the system energy. This avoids the impact of pulsation during the plunger suction and discharge reversal in the power pump 3 on the control accuracy of the ground power unit, and extends the service life through flexible reversal. The belt 19 is a V-belt.

[0026] Specifically, the outlet of water tank 1 is connected to the inlet of power pump 3 through a pipeline. The outlet of power pump 3 is divided into two lines, namely supply pipeline A and supply pipeline B. The end of supply pipeline A away from power pump 3 is connected to the lower end of motor plunger of downhole pump set 18 through a pipeline. The end of supply pipeline B away from power pump 3 is connected to the upper end of motor plunger of downhole pump set 18 through a pipeline. Supply line A connects to the central pipe of the double-layer pipeline of downhole pump unit 18. The central pipe of the double-layer pipeline of downhole pump unit 18 connects to the lower end of the motor plunger of downhole pump unit 18, thereby delivering the power fluid in supply line A to the lower end of the motor plunger of downhole pump unit 18. Supply line B connects to the annulus pipe of the double-layer pipeline of downhole pump unit 18. The annulus pipe of the double-layer pipeline of downhole pump unit 18 connects to the upper end of the motor plunger of downhole pump unit 18, thereby delivering the power fluid in supply line B to the upper end of the motor plunger of downhole pump unit 18. Thus, supply lines A and B are respectively connected to downhole pump unit 18. Supply lines A and B are used to deliver pressurized power fluid to downhole pump unit 18 for drainage and gas production.

[0027] A branch line is set on the supply pipeline A as the return pipeline B, that is, the return pipeline B is connected at point A1 on the supply pipeline A. The end of the return pipeline B away from the supply pipeline A is connected to the return water port of the water tank 1, so that the downhole pump unit 18 is connected to the water tank 1 through the central pipeline, the pipeline section from point A1 on the supply pipeline A to the connection with the return pipeline B, and the return pipeline B. A branch line is set on the supply pipeline B as the return pipeline A, that is, the return pipeline A is connected at point B1 on the supply pipeline B. The end of the return pipeline A away from the supply pipeline B is connected to the return water port of the water tank 1, so that the downhole pump unit 18 is connected to the water tank 1 through the annulus pipeline, the pipeline section from point B1 on the supply pipeline B to the connection with the return pipeline A, and the return pipeline A. The downhole pump unit 18 is connected to the return port of the water tank 1, and the spent power fluid in the downhole pump unit 18 is returned to the water tank 1 through the return fluid line B and the return fluid line A respectively. The water tank 1, the power pump 3, the supply fluid line A, the downhole pump unit 18, the return fluid line A, and the water tank 1 form one power fluid flow cycle; the water tank 1, the power pump 3, the supply fluid line B, the downhole pump unit 18, the return fluid line B, and the water tank 1 form another power fluid flow cycle.

[0028] The double-layer piping system comprises a central piping system and an annular piping system, provided by a double-layer tubing string. The double-layer tubing string consists of a central tubing and a main tubing system. The central tubing contains the central piping system, and the space between the central tubing and the main tubing is the annular piping system. The central piping system connects to the lower end of the motor plunger of the downhole pump unit, and the annular piping system connects to the upper end of the motor plunger of the downhole pump unit. This part is existing technology for downhole pump units and will not be elaborated upon here.

[0029] The operation method of the ground power unit is as follows: When the motor plunger of the downhole pump set 18 is at the lower end, the motor 2 drives the power pump 3 through the belt 19 to draw power fluid from the water tank 1 and pressurize the power fluid. Then, the power fluid is transported to the lower end of the motor plunger of the downhole pump set 18 through the supply pipeline A, pushing the motor plunger of the downhole pump set 18 to move upward. At this time, the exhausted power fluid returns from the upper end of the motor plunger of the downhole pump set 18 through the annulus pipeline, the pipeline section from the connection point B1 of the supply pipeline B and the return pipeline A to the connection point of the return pipeline A, and the return pipeline A back to the water tank 1, forming a... The power fluid circulation is formed. When the motor plunger of the downhole pump set 18 moves to the upper end, the motor 2 drives the power pump 3 through the belt 19 to draw power fluid from the water tank 1 and pressurize the power fluid. Then, the power fluid is transported to the upper end of the motor plunger of the downhole pump set 18 through the supply pipeline B, pushing the motor plunger of the downhole pump set 18 to move downward. At this time, the exhausted power fluid returns from the lower end of the motor plunger of the downhole pump set 18 through the central pipeline, the pipeline section from the connection point A1 of the supply pipeline A and the return pipeline B to the connection point of the central pipeline, and the return pipeline B back to the water tank 1, forming a power fluid circulation.

[0030] like Figure 2As shown, the above-mentioned ground power unit also includes a control system, which is used to control the structural operation of the above-mentioned ground power unit during the drainage of natural gas or deep coal and rock gas, thereby realizing the cyclic drainage process of the downhole pump group 18.

[0031] The control system includes an electromagnetic directional valve 8, installed on the pipeline at the outlet of the power pump 3, used to regulate the flow direction at the outlet of the power pump 3. The electromagnetic directional valve 8 divides the outlet of the power pump 3 into two paths: one is supply pipeline A, and the other is supply pipeline B. The electromagnetic directional valve 8 can be a three-way electromagnetic directional valve or two two-position two-way electromagnetic directional valves. If a three-way electromagnetic directional valve is used, it includes one inlet and two outlets. The inlet of the three-way electromagnetic directional valve is connected to the outlet of the power pump 3 via a pipeline, and the two outlets are connected to supply pipeline A and supply pipeline B respectively. If two two-position two-way electromagnetic directional valves are used, the inlets of both valves are connected to the outlet of the power pump 3 via pipelines, and the outlets are connected to supply pipeline A and supply pipeline B respectively. When the outlet of the solenoid directional valve 8 connected to the supply line A is opened, the power fluid flowing out of the outlet of the power pump 3 flows into the supply line A. At this time, the pipeline from point B1 on the supply line B to the downhole pump group 18, together with the return line A, serves as the waste power fluid return path. When the outlet of the solenoid directional valve 8 connected to the supply line B is opened, the power fluid flowing out of the outlet of the power pump 3 flows into the supply line B. At this time, the pipeline from point A1 on the supply line A to the downhole pump group 18, together with the return line B, serves as the waste power fluid return path. The solenoid directional valve 8, supply line A, return line B, supply line B, and return line A can realize a closed hydraulic system circuit and power fluid circulation.

[0032] The control system also includes two check valves 9. One is installed on the supply line A, between the solenoid directional valve 8 and the return line B, specifically on the line between point A1 on the supply line A and the solenoid directional valve 8. The other is installed on the supply line B, between the solenoid directional valve 8 and the return line A, specifically on the line between point B1 on the supply line B and the solenoid directional valve 8. The check valves 9 ensure unidirectional flow of the power fluid after passing through the solenoid directional valve 8, preventing backflow when the line pressure is high.

[0033] The control system also includes a speed sensor installed on the motor 2 to monitor the speed of the motor 2 and record the total number of rotations of the motor 2. In conjunction with the flow sensor, when the speed of the variable frequency reluctance motor or variable frequency permanent magnet motor is close to the preset number of rotations of the motor 2, the speed is reduced to achieve flexible commutation.

[0034] The control system also includes an upstroke return valve 15 and a downstroke return valve 17. The upstroke return valve 15 is installed on return line A and controls the opening and closing of return line A. The downstroke return valve 17 is installed on return line B and controls the opening and closing of return line B. Both the upstroke return valve 15 and the downstroke return valve 17 are two-position two-way solenoid valves.

[0035] The control system also includes a first pressure sensor 7, which is installed on the connecting pipeline between the power pump 3 and the solenoid directional valve 8, for detecting pipeline pressure.

[0036] The control system also includes a first flow sensor 10 and a second pressure sensor 11, installed on the pipeline between point A1 on the supply line A and the solenoid directional valve 8, to monitor the pressure and flow rate of the power fluid entering the central pipeline through the supply line A; a second flow sensor 13 and a third pressure sensor 14, installed on the pipeline between point B1 on the supply line B and the downhole pump unit 18, to monitor the pressure and flow rate of the power fluid entering the annulus pipeline through the supply line B or the waste power fluid flowing from the annulus pipeline into the return line A. The second pressure sensor 11 and the third pressure sensor 14 are used to monitor the pressure in the supply line, and to shut down the system when the pressure is abnormal.

[0037] The control system also includes a return water flow meter 16, which is installed on the return water line A between the upstroke return water valve 15 and the supply line B. It monitors the drainage status of the closed hydraulic circulation system. By comparing the return water flow rate during the upstroke with the injected power fluid, the drainage flow rate can be calculated. By adjusting the working status of the hydraulic circulation system, the working conditions can be continuously optimized. This is a key technical path to improve drainage efficiency, reduce energy consumption, and extend equipment life to achieve the ideal drainage state.

[0038] The control system also includes a spring-reset safety valve 5, a pressure gauge 6, and an automatic vent valve 12. The spring-reset safety valve 5 is installed on the pipeline between the first pressure sensor 7 and the power pump 3, specifically on the pipeline between the first pressure sensor 7 and the accumulator 4. It is a safety protection device that automatically opens and closes using spring force to prevent the power hydraulic pressure from exceeding a set threshold and causing a safety accident. The pressure gauge 6 is installed on the pipeline between the spring-reset safety valve 5 and the first pressure sensor 7. The automatic vent valve 12 is installed on the fluid supply line B and is used to discharge gas from the downhole pump unit 18, specifically the gas in the double-layer tubing annulus line connected to the fluid supply line B. The automatic vent valve 12 consists of a filter, a vent valve, and a solenoid safety valve. The automatic vent valve 12 operates normally under the protection of the solenoid safety valve.

[0039] The control system also includes a control cabinet for receiving signals from sensors in the pipeline, thereby monitoring the system and controlling the opening and closing of the solenoid directional valves.

[0040] All of the above-mentioned pipe connections are threaded connections.

[0041] The above-mentioned ground power unit operates as follows: Motor 2 drives power pump 3 via belt 19 to pressurize the power fluid, and then the pressurized power fluid drives downhole pump group 18 under the control of electromagnetic reversing valve 8 to achieve high-pressure power fluid delivery. The variable frequency reluctance motor or variable frequency permanent magnet motor uses relevant parameter information from flow sensor, pressure sensor, and speed sensor, and the frequency converter controls the motor speed and total number of rotations, achieving flexible reversing control in the hydraulic control system, avoiding pipeline impact, and extending pipeline service life.

[0042] The above-mentioned operation method of the ground power unit is based on the position and direction of the motor plunger movement of the downhole pump unit 18, and specifically includes the following operating conditions: Upstroke: The motor control system controls the motor 2 to drive the power pump 3, which pressurizes the power fluid in the water tank 1. At this time, the outlet of the solenoid directional valve 8 connected to the supply line A is open and the outlet of the supply line B is closed. The supply line A is open and the supply line B is closed. The power fluid enters the lower end of the motor plunger of the downhole pump set 18 from the central pipeline of the double-layer tubing along the pipeline of the supply line A, pushing the motor plunger to move upward. The upstroke return water valve 15 is open and the downstroke return water valve 17 is closed. The waste power fluid at the upper end of the motor plunger in the downhole pump set 18 returns to the water tank 1 through the annulus pipeline and the return water pipeline A.

[0043] Downstroke: The motor control system controls the motor 2 to drive the power pump 3, pressurizing the power fluid in the water tank 1 via the power pump 3. At this time, the outlet of the solenoid directional valve 8 connected to the supply pipeline A is closed, and the outlet of the supply pipeline B is open. The supply pipeline A is closed, and the supply pipeline B is open. The power fluid enters the upper end of the motor plunger of the downhole pump set 18 from the annulus of the double-layer tubing through the supply pipeline B, pushing the motor plunger to move downward. The upstroke return water valve 15 is closed, and the downstroke return water valve 17 is open. The exhausted power fluid at the lower end of the motor plunger in the downhole pump set 18 returns to the water tank 1 via the central pipeline through the return water pipeline B.

[0044] After the upstroke is completed, the system performs a downstroke by controlling the solenoid reversing valve 8, and the corresponding return water valve is opened accordingly, and the entire drainage and gas extraction process is completed in a cycle.

[0045] Example 2 This invention discloses a deep well long-life drainage and gas production system, comprising a downhole pump unit 18 for drainage and gas production and a surface power unit connected to the downhole pump unit 18. The surface power unit is the same as that described in Embodiment 1, and the connection method between the surface power unit and the downhole pump unit 18 is also described in Embodiment 1. The downhole pump unit 18 has a motor plunger. The power fluid flowing into the surface power unit drives the motor plunger to move up and down, thereby realizing drainage and gas production from the downhole pump unit 18. The structure of the downhole pump unit 18 adopts existing technology and will not be described in detail here.

[0046] Example 3 This invention discloses a control method for a deep well long-life drainage and gas production system, which can realize the control of the above-mentioned surface power unit and drainage and gas production system. The method includes monitoring the number of rotations of the motor through a speed sensor, controlling the power fluid flow rate by controlling the speed of the motor 2 according to the signal transmitted by the speed sensor, and reducing the speed of the motor 2 when the motor plunger of the downhole pump 18 is close to the top dead center or bottom dead center according to the total volume of the discharged fluid during the upper and lower strokes, thereby reducing the power fluid flow rate. Then, the electromagnetic reversing valve 8 is controlled to reverse, realizing flexible reversing control.

[0047] Specifically, the following steps are included: 1) Before using the surface power unit for drainage, determine the total volume V of the discharged fluid in one upstroke of the downhole pump unit 18 through preliminary tests. T1 and the corresponding number of rotations C of motor 2 T1 Similarly, determine the total volume V of the discharged fluid in one downstroke of the downhole pump unit 18. T2 and the corresponding number of rotations C of motor 2 T2 ; 2) When using a ground power unit for drilling, the rotation number of motor 2 is monitored by a speed sensor. Based on the rotation number of motor 2, the speed of motor 2 and the reversing of the solenoid valve 8 are adjusted to achieve switching between the upstroke and downstroke and cyclic drilling. Before switching between the upstroke and downstroke (before the solenoid valve 8 reverses), the speed of motor 2 is reduced to 0-25 rpm. After switching, the speed of motor 2 is increased to the rated speed within 0.8-1.5 seconds and maintained at the rated speed. The specific operation is as follows: Upstroke: The solenoid directional valve 8 reverses, switching the downhole pump unit 18 to the upstroke mode. The speed of motor 2 is increased to the rated speed within 0.8~1.5s and maintained at the rated speed. The number of rotations of motor 2 is monitored from the start of the solenoid directional valve 8 reversal. When the number of motor rotations during this upstroke reaches (0.85~0.9) × C... T1 At that time, within 1.5~2 seconds, reduce the speed of motor 2 to 0~25 rpm, and wait until the number of motor revolutions in the current stroke reaches C. T1At that time, the outlet direction of the electromagnetic reversing valve 8 is switched, thereby switching to the downstroke of the downhole pump unit 18; Downstroke: After the solenoid directional valve 8 switches, the current state becomes the downstroke, increasing the speed of motor 2 to the rated speed within 0.8~1.5s and maintaining the rated speed. The number of rotations of motor 2 is monitored from the start of the solenoid directional valve 8 switching. When the number of motor rotations during this downstroke reaches (0.85~0.9) × C... T2 Within 1.5 to 2 seconds, reduce the speed of motor 2 to 0 to 25 rpm, until the number of motor revolutions during the current stroke reaches C. T2 At that time, the outlet direction of the electromagnetic reversing valve 8 is switched, thereby switching to the upstroke of the downhole pump unit 18; After the solenoid reversing valve 8 switches, it switches back to the upstroke, and the above operation is repeated to achieve cyclic sampling of upstroke and downstroke.

[0048] In this invention, when the surface power unit is used in a deep well drainage project, it employs a variable frequency reluctance motor or permanent magnet motor and a three-cylinder plunger pump, with a cost of less than 100,000 yuan. Because the power pump uses ceramic plungers and a combined sealed three-cylinder plunger pump, the lifespan of vulnerable parts can reach 2200 hours. In contrast, the existing hydraulic system, consisting of a motor, a closed-loop plunger pump, an oil tank, a single-cylinder double-acting piston pump, and a base, uses a motor to drive the closed-loop plunger pump, controlling the hydraulic oil in the oil tank to enter the piston pump's oil chamber, thus driving the piston pump to perform its stroke and transporting the power fluid from the water chambers at both ends of the oil chamber to the downhole pump. This system costs 143,000 yuan, requires frequent piston replacement, and has a vulnerable part lifespan of only 400 hours.

[0049] It is evident that the ground power unit of the present invention reduces costs by at least 30% and increases service life by 4.5 times compared to existing technologies.

[0050] In summary, the deep well long-life drainage and gas production system, its surface power unit, and control method disclosed in this invention have the advantages of simple power system, low cost, long service life of vulnerable parts, and low maintenance cost.

Claims

1. A surface power unit for a deep well long-life drainage and gas production system, wherein the surface power unit is connected to a downhole pump group (18) and is used to drive the motor plunger of the downhole pump group (18) to move during the drainage of natural gas or deep coal and rock gas, thereby realizing the drainage process of the downhole pump group (18); the surface power unit includes a water tank (1) for storing power fluid and a power pump (3) connected to the water tank (1) and pressurizing the power fluid; characterized in that: The ground power unit also includes a motor (2), which is connected to the power pump (3) via a belt (19) and is used to drive the power pump (3) to rotate, thereby pressurizing the power fluid in the water tank (1) and providing power; the motor (2) is a variable frequency reluctance motor (2) or a variable frequency permanent magnet motor (2).

2. The ground power unit according to claim 1, characterized in that: The power pump (3) is a three-cylinder plunger pump, and an accumulator (4) is installed on its outlet pipe.

3. The ground power unit according to claim 1, characterized in that: The outlet of the water tank (1) is connected to the inlet of the power pump (3) via a pipeline. The outlet of the power pump (3) is divided into two lines, namely supply pipeline A and supply pipeline B. The end of supply pipeline A away from the power pump (3) is connected to the lower end of the motor plunger of the downhole pump set (18). The end of supply pipeline B away from the power pump (3) is connected to the upper end of the motor plunger of the downhole pump set (18). A branch is provided on supply pipeline A as a return pipeline. Pipeline B, the end of the return pipeline B away from the supply pipeline A is connected to the return port of the water tank (1), so that the downhole pump group (18) is connected to the return port of the water tank (1) through the return pipeline B; a branch is set on the supply pipeline B as the return pipeline A, the end of the return pipeline A away from the supply pipeline B is connected to the return port of the water tank (1), so that the downhole pump group (18) is connected to the return port of the water tank (1) through the return pipeline A.

4. The ground power unit according to claim 3, characterized in that: The ground power unit also includes: An electromagnetic reversing valve (8) is installed at the outlet of the power pump (3) and connected to the power pump (3) through a pipeline, and divides the outlet of the power pump (3) into two paths; the inlet of the electromagnetic reversing valve (8) is connected to the outlet of the power pump (3), and there are two outlets, which are respectively connected to the supply pipeline A and the supply pipeline B; Two check valves (9) are provided, one of which is provided on the liquid supply line A and located between the electromagnetic reversing valve (8) and the return line B, and the other is provided on the liquid supply line B and located between the electromagnetic reversing valve (8) and the return line A. A speed sensor is installed on the motor (2).

5. The ground power unit according to claim 4, characterized in that: The electromagnetic reversing valve (8) is a three-way electromagnetic reversing valve. The inlet of the three-way electromagnetic reversing valve is connected to the outlet of the power pump (3), and the two outlets are respectively connected to the supply line A and the supply line B; or, the electromagnetic reversing valve (8) is two two-position two-way electromagnetic switch valves. The inlets of the two two-position two-way electromagnetic switch valves are both connected to the outlet of the power pump, and the outlets are respectively connected to the supply line A and the supply line B.

6. The ground power unit according to claim 4, characterized in that: The ground power unit also includes: The first pressure sensor (7) is located between the power pump (3) and the electromagnetic reversing valve (8); The second pressure sensor (11) and the first flow sensor (10) are installed on the liquid supply line A; The third pressure sensor (14) and the first flow sensor (13) are installed on the liquid supply line B; The top stroke return water valve (15) is installed on the return liquid line A and is used to control the opening and closing of the return liquid line A; The downstroke return water valve (17) is installed on the return liquid pipeline B and is used to control the opening and closing of the return liquid pipeline B; The return water flow meter (16) is installed on the return liquid line A and is located on the pipeline between the upper stroke return water valve (15) and the supply liquid line B.

7. The ground power unit according to claim 6, characterized in that: Both the upstroke return valve (15) and the downstroke return valve (17) are two-position two-way solenoid valves.

8. The ground power unit according to claim 6, characterized in that: Also includes: An automatic vent valve (12) is installed on the liquid supply line B to discharge the gas from the downhole pump group (18) connected to the liquid supply line B; A spring-reset safety valve (5) is installed on the pipeline between the first pressure sensor (7) and the power pump (3); A pressure gauge (6) is installed on the pipeline between the spring-reset safety valve (5) and the first pressure sensor (7).

9. A deep well long-life drainage and gas production system, comprising a downhole pump unit (18) for drainage and gas production and a surface power unit connected to the downhole pump unit (18), characterized in that: The ground power unit is the ground power unit as described in any one of claims 1 to 8.

10. The control method for the deep well long-life drainage gas production system according to claim 9, characterized in that: Includes the following steps: 1) Before using the aforementioned surface power unit for drainage, the total volume V of the discharged fluid discharged by the downhole pump unit in one upstroke is determined through preliminary tests. T1 and the corresponding number of motor rotations C T1 The total volume V of the discharged fluid in one downstroke T2 and the corresponding number of motor rotations C T2 ; 2) When using the ground power unit for mining, monitor the number of motor rotations and switch between the upstroke and downstroke based on the number of motor rotations to achieve cyclic mining between the upstroke and downstroke; wherein, before switching between the upstroke and downstroke, the motor speed is reduced to 0~25 rpm, and after switching, the motor speed is increased to the rated speed and maintained at the rated speed. The switching criteria for the upstroke and downstroke include: If the current state is during the upstroke, monitor the number of motor revolutions during the current stroke. When the number of motor revolutions reaches (0.85~0.9)×C... T1 At this time, reduce the motor speed to 0-25 rpm, and wait until the number of motor revolutions in the current stroke reaches C. T1 At that time, switch to the downstroke; If the current state is in the downstroke, monitor the number of motor revolutions during the current stroke. When the number of motor revolutions reaches (0.85~0.9)×C... T2 At this time, reduce the motor speed to 0-25 rpm, and wait until the number of motor revolutions in the current stroke reaches C. T2 At that time, switch to the top stroke.

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