Coal bed gas exploitation device

Abstract

The coal bed gas mining device comprises a liquid supply assembly, a gas production tree assembly and an operation pump assembly, the liquid supply assembly comprises a plunger pump, a motor, a frequency converter and a liquid containing piece, the frequency converter is electrically connected with the motor, the motor is connected with the plunger pump, and the liquid containing piece is connected with the gas production tree assembly. The liquid containing piece is communicated with the liquid inlet end of the plunger pump. The christmas tree assembly is provided with a liquid inlet, a flowback liquid outlet, a liquid outlet and a gas outlet, and the liquid inlet is communicated with the liquid discharge end of the plunger pump; the operation pump assembly comprises a piston pump and a pipeline assembly, the piston pump is provided with a connector inner pipe and a connector outer pipe, the connector inner pipe is communicated with the liquid outlet through the pipeline assembly, and the connector outer pipe is communicated with the flow-back liquid outlet and the air outlet through the pipeline assembly. The coal bed gas mining device can solve the problems that equipment needs to be replaced, the workload is large and the working efficiency is low in the current coal bed gas mining process.

Description

Technical Field

[0001] The present application belongs to the technical field of oil and gas exploitation, and specifically relates to a coalbed methane exploitation device. Background Art

[0002] The process of coalbed methane extraction is generally divided into three stages. In the first stage, since the critical desorption pressure of the coal seam has not been reached, generally only water is produced; in the second stage, as the reservoir pressure drops, when the pressure reaches the critical desorption pressure, adsorbed gas desorbs to form bubbles, but has not yet flowed; in the third stage, as the reservoir pressure further decreases, the gas saturation exceeds the critical flow saturation, forming a gas-water two-phase flow. At present, in order to adapt to the above three stages, screw pumps are usually used for extraction in the early stage of gas extraction, and piston pumps are replaced for extraction in the later stage. However, since the pipe string needs to be lifted and lowered twice during the equipment replacement process, the workload is large and the work efficiency is low. Utility Model Content

[0003] The purpose of the embodiment of the present application is to provide a coalbed methane mining device to solve the problem that equipment needs to be replaced during the current coalbed methane mining process, resulting in a large workload and low work efficiency.

[0004] The embodiment of the present application discloses a coalbed methane mining device, which includes a liquid supply component, a gas tree component and an operating pump component, wherein the liquid supply component includes a plunger pump, a motor, a frequency converter and a liquid container, wherein the frequency converter is electrically connected to the motor, and the motor is connected to the plunger pump, and the liquid container is connected to the liquid inlet end of the plunger pump;

[0005] The gas tree assembly is provided with a liquid inlet, a return liquid outlet, a liquid outlet and a gas outlet, and the liquid inlet is connected to the liquid discharge end of the plunger pump;

[0006] The working pump assembly includes a piston pump and a pipeline assembly. The piston pump is provided with a connector inner tube and a connector outer tube. The connector inner tube is connected to the liquid outlet through the pipeline assembly, and the connector outer tube is connected to both the return liquid port and the air outlet through the pipeline assembly.

[0007] The embodiment of the present application discloses a coalbed methane mining device, wherein the liquid supply component is connected to the working pump component through the gas tree component, so that the plunger pump can drive the power liquid in the liquid container to be transported to the piston pump through the gas tree component to drive the piston pump to work, and correspondingly, the return liquid and coalbed methane extracted by the piston pump can be output through the gas tree component, so as to realize the mining of coalbed methane. In addition, by making the frequency converter electrically connected to the plunger pump by the motor, the flow of the plunger pump can be controlled by the frequency converter by controlling the speed of the motor and other parameters, thereby controlling the running speed of the piston pump, achieving the purpose of controlling its displacement, ensuring that the displacement of the piston pump can be based on the different needs of each stage in the coalbed methane mining process, so that there is no need to replace equipment, so as to reduce the workload and improve the mining efficiency of coalbed methane. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0009] Figure 1 This is a schematic diagram of the structure of a liquid supply component in a coalbed methane mining device disclosed in an embodiment of the present application;

[0010] Figure 2 It is a schematic diagram of assembling a gas tree assembly and an operating pump assembly in a coalbed methane production device disclosed in an embodiment of the present application;

[0011] Figure 3 This is a schematic diagram of the structure of a piston pump in a coalbed methane extraction device disclosed in an embodiment of the present application.

[0012] Reference numerals:

[0013] 100-liquid supply assembly, 110-piston pump, 120-frequency converter, 130-liquid container, 140-filter, 150-liquid level sensor, 160-flow sensor, 170-pressure sensor, 180-holding tank,

[0014] 210-gas tree structure, 220-hanger, 230-tubing tee, 240-casing cross, 251-power fluid valve, 252-flowback valve, 253-gas production valve, 254-inspection valve,

[0015] 300-piston pump, 311-first one-way valve A, 312-first one-way valve B, 313-second one-way valve A, 314-second one-way valve B, 321-first reversing valve assembly, 322-second reversing valve assembly, 331-piston, 332-piston rod, 340-filter assembly, 351-first power fluid chamber, 352-second power fluid chamber, 361-first well fluid chamber, 362-second well fluid chamber, 371-first pump barrel, 372-second pump barrel, 381-connector inner tube, 382-connector outer tube, 383-core tube, 391-isolator, 392-isolator seal,

[0016] 410-casing, 420-mixing oil pipe, 430-center oil pipe,

[0017] 500-Downhole tool string. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0019] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0020] The present application embodiment discloses a coal bed methane mining device, which can be used to mine coal bed methane. Figure 1-Figure 3 As shown, the coalbed methane mining device includes a liquid supply component 100, a gas tree component and an operating pump component. Among them, the liquid supply component 100 is a driving mechanism of the operating pump component, the gas tree component is used as a connecting structure between the liquid supply component 100 and the operating pump component, and the operating pump component is directly used to provide mining.

[0021] In detail, the liquid supply assembly 100 includes a plunger pump 110, a motor, a frequency converter 120 and a liquid container 130, the gas tree assembly is provided with a liquid inlet, a return liquid port, a liquid outlet and a gas outlet, and the working pump assembly includes a piston pump 300 and a pipeline assembly. Of course, the coalbed methane mining device may also include other components such as a downhole tool string 500 disposed at the lower end of the working pump assembly, and at least one of the liquid supply assembly 100, the gas tree assembly and the working pump assembly may also include other components, which will not be described in detail here for the sake of brevity.

[0022] In more detail, in the process of assembling the coalbed methane extraction device, the frequency converter 120 is electrically connected to the plunger pump 110 by using the electric motor, that is, the frequency converter 120 is electrically connected to the electric motor, and the electric motor is connected to the plunger pump 110. This allows the frequency converter 120 to control the working parameters of the plunger pump 110, thereby controlling the movement frequency of the plunger pump 110 by controlling the rotation speed of the electric motor connected to the plunger pump 110, and thereby achieving the purpose of controlling the flow rate of the power fluid in the plunger pump 110, so that the operating speed of the piston pump 300 driven by the plunger pump 110 can also be controlled. In different stages of coalbed methane extraction, the displacement of the piston pump 300 can be correspondingly controlled by the frequency converter 120. This allows the coalbed methane extraction device disclosed in the embodiment of the present application to meet the displacement requirements of each stage in the coalbed methane extraction process, and thus there is no need to replace the extraction equipment, which can greatly reduce the workload and improve work efficiency. More specifically, in the coalbed methane extraction device disclosed in the embodiment of the present application, the piston pump 300 includes a double-acting piston pump, which has a relatively large upper flow limit, so that it can better adapt to various stages of coalbed methane extraction and ensure that the coalbed methane extraction efficiency is always relatively high. Based on this, in the following description of the present application, the piston pump 300 specifically includes a double-acting piston pump.

[0023] As for the fluid connectivity in the coalbed methane extraction device, in detail, the liquid container 130 is connected to the liquid inlet end of the plunger pump 110, so that the water or other power fluid in the liquid container 130 can be transported to the plunger pump 110, and the discharge end of the plunger pump 110 can be connected to the liquid inlet of the gas production tree assembly, and the liquid outlet of the gas production tree assembly is connected to the connector inner tube 381 of the piston pump 300 through the pipeline assembly, so that the power fluid output by the plunger pump 110 can be transported to the piston pump 300 through the pipeline assembly and the gas production tree assembly to drive the piston pump 300 to work.

[0024] Correspondingly, for the return fluid extracted by the piston pump 300, the connector outer tube 382 in the piston pump 300 is also connected to the return fluid port of the gas production tree assembly through the pipeline assembly, and the return fluid port is also connected to the liquid recovery device, so that the return fluid can be transported to the liquid recovery device and other equipment through the pipeline assembly and the gas production tree assembly for recovery. Of course, the return fluid can also be discharged to the plant pipeline, etc. for recovery, which is not limited in this article. It should be noted that although the power fluid and the return fluid are both transported by the pipeline assembly, in actual applications, by making the pipeline assembly include multiple pipelines arranged in parallel, or by making multiple pipelines set in a package, the pipeline assembly can form multiple fluid transport paths that do not interfere with each other, ensuring that the power fluid and the return fluid can be independently transported by the pipeline assembly.

[0025] In more detail, Figure 2 As shown, the pipeline assembly may include a casing 410, a mixing oil pipe 420 and a central oil pipe 430, and the gas tree assembly includes a gas tree structure 210, a hanger 220, an oil pipe tee 230 and a casing cross 240. Of course, the gas tree assembly may also be provided with a power fluid valve 251, a return fluid valve 252, a gas production valve 253 and a maintenance valve 254, etc.

[0026] Among them, one end of the mixed oil pipe 420 is suspended on the casing spool 240, and the other end of the mixed oil pipe 420 is connected to the piston pump 300. The central oil pipe 430 is suspended on the hanger 220, and one end of the central oil pipe 430 is connected to the discharge end of the plunger pump 110 through the power fluid valve 251, and the other end of the central oil pipe 430 is inserted into the piston pump 300. The casing 410 is sleeved outside the mixed oil pipe 420, and the annulus between the casing 410 and the mixed oil pipe 420 is the oil-casing annulus, which is connected to the gas production valve 253 and the inspection valve 254. The annulus between the mixed oil pipe 420 and the central oil pipe 430 is the oil pipe annulus, and the oil pipe annulus is connected to the return valve on the oil pipe tee 230 for conveying return fluid. The gas production valve 253 is used for gas production and conveying coalbed methane to the gas gathering station; the inspection valve 254 is used for sampling and inspection.

[0027] The piston pump 300 may specifically include a first reversing valve assembly 321, a first pump barrel 371, a separator assembly, a second pump barrel 372, a second reversing valve assembly 322, a filter assembly 340, and a connector inner and outer pipe assembly. One end of the piston pump 300 where the second reversing valve assembly 322 is located is directly connected to the gas tree assembly through a pipeline assembly. Specifically, the connector outer pipe 382 is threadedly connected to the mixing oil pipe 420, one end of the connector inner pipe 381 is inserted into the core pipe 383, and the other end is threadedly connected to the central oil pipe 430. Two pistons 331 are arranged in the piston pump 300, and the two pistons 331 are connected by a piston rod 332. The piston rod 332 passes through the separator 391 and is sealed and installed in the separator 391. A separator seal 392 is arranged in the separator 391, and its inner ring plays the role of sealing the piston rod 332, and the outer ring plays the role of sealing the inner hole of the separator 391.

[0028] When the above-mentioned coalbed methane extraction device is used to extract coalbed methane, the plunger pump 110 pressurizes the power fluid so that the power fluid is transported to the gas production tree assembly, further enters the central oil pipe 430 through the hanger 220, and is filtered through the filter assembly 340. Thereafter, the power fluid enters the second power fluid chamber 352 through the second reversing valve assembly 322, and the piston is driven to move toward the end where the first reversing valve assembly 321 is located. At this time, the volume of the second well fluid chamber 362 becomes smaller, so that the first one-way valve B312 is closed, and the well fluid is discharged from the second one-way valve B314; the volume of the first well fluid chamber 361 is The accumulation increases, the second one-way valve A313 is closed, and the well fluid is sucked from the first one-way valve A311; when the piston hits the top rod of the first reversing valve assembly 321, the first reversing valve assembly 321 acts to switch the power fluid channel. At this time, the power fluid enters from the first power fluid chamber 351, driving the piston to move toward the end where the second reversing valve assembly 322 is located; the first well fluid chamber 361 becomes smaller, the first one-way valve A311 is closed, the well fluid is discharged from the second one-way valve A313, the second well fluid chamber 362 becomes larger, the second one-way valve B314 is closed, and the well fluid is sucked from the first one-way valve B312. Furthermore, in the process of coalbed methane extraction using the piston pump 300 disclosed in the embodiment of the present application, no matter in which direction the piston 331 moves, there is always one chamber to absorb well fluid and the other chamber to discharge well fluid, which is the so-called double-acting piston pump.

[0029] Moreover, during the extraction process of the return fluid, coalbed methane will be extracted together with the return fluid. For this reason, the connector outer tube is also connected to the gas outlet of the gas production tree assembly through the pipeline assembly, so that the coalbed methane can be transported to the column gas collection device through the pipeline assembly and the gas outlet of the gas production tree assembly.

[0030] The embodiment of the present application discloses a coalbed methane mining device, wherein the liquid supply component 100 is connected to the working pump component through the gas tree component, so that the plunger pump 110 can drive the power liquid in the liquid container 130 to be transported to the piston pump 300 through the gas tree component to drive the piston pump 300 to work, and correspondingly, the return liquid and coalbed methane extracted by the piston pump 300 can be output through the gas tree component, thereby realizing the coalbed methane mining. In addition, by making the frequency converter 120 electrically connected to the plunger pump 110 using the motor, the flow rate of the plunger pump 110 can be controlled by the frequency converter 120 by controlling the speed of the motor and other parameters accordingly, thereby controlling the running speed of the piston pump 300, achieving the purpose of controlling its displacement, ensuring that the displacement of the piston pump 300 can be based on the different needs of each stage in the coalbed methane mining process, so that there is no need to replace the equipment, so as to reduce the workload and improve the coalbed methane mining efficiency.

[0031] In addition, by using a double-acting piston pump in the coalbed methane extraction device disclosed in the embodiment of the present application, the displacement of the operating pump assembly is relatively large, which can better meet the displacement requirements of each stage in coalbed methane extraction.

[0032] As described above, the backflow liquid extracted by the piston pump 300 can be recovered by the backflow liquid recovery device, or the backflow liquid port of the gas production tree assembly can be connected to the plant service pipeline, etc., so as to achieve the purpose of recovering the backflow liquid. In order to improve the efficiency of the use of power fluid and reduce the number of devices or connecting pipelines required to be set during the mining process, in another embodiment of the present application, the backflow liquid port can be connected to the liquid container 130, so that the backflow liquid can be transported into the liquid container 130, and then the backflow liquid can be transported to the plunger pump 110 as power fluid again.

[0033] Of course, considering that the flowback fluid includes spent power fluid and well fluid, the amount of the flowback fluid transported back to the liquid container 130 is usually greater than the amount of power fluid output from the liquid container 130. In order to prevent the liquid container 130 from overflowing, in a specific embodiment of the present application, the liquid container 130 is provided with an overflow port, which can be connected to an external site. In order to improve the utilization rate of the power fluid, in another embodiment of the present application, the overflow port can be provided with an overflow pipeline, and a holding pool 180 can be formed in the mining area, so that the liquid in the liquid container 130 can be transported to the holding pool 180 through the overflow pipeline for temporary storage, so as to facilitate subsequent reuse.

[0034] When the return liquid port of the gas tree assembly is connected to the liquid container 130, and the liquid container 130 is provided with an overflow port, the water level in the liquid container 130 is usually located within a preset spacing range below the overflow port. In a specific embodiment of the present application, the liquid supply assembly 100 may also include a liquid level sensor 150, which is disposed in the liquid container 130 and is used to detect the liquid level in the liquid container 130. During the mining process, if the liquid level in the liquid container 130 is lower than the preset liquid level range, it can be generally considered that the liquid container 130 or the pipeline may have a fault such as liquid leakage. Based on this, when the staff obtains the abnormal liquid level, the shutdown and maintenance work can be carried out immediately. Alternatively, the liquid level sensor 150 can also be connected to the controller of the coalbed methane mining device so that when the liquid level is abnormal, the mining work can be automatically stopped by the controller.

[0035] Taking into account that the return fluid transported back into the liquid container 130 may usually include impurities such as gravel, in order to prevent the impurities from adversely affecting the normal operation and service life of the plunger pump 110 when the return fluid is used as power fluid to be re-transported to the plunger pump 110, in a specific embodiment of the present application, a filter 140 is provided on the pipeline between the liquid container 130 and the plunger pump 110. The filter 140 can be used to filter the liquid transported from the liquid container 130 to the plunger pump 110, thereby improving the working stability and service life of the plunger pump 110.

[0036] In another embodiment of the present application, a plurality of settling plates may be provided in the liquid container 130, and the plurality of settling plates may be arranged at intervals in the vertical direction, so that the impurities in the return liquid may be uniformly precipitated to the bottom of the liquid container 130 through multi-stage sedimentation by using the plurality of settling plates, so that the cleanliness of the liquid in the upper region of the liquid container 130 is relatively high. On this basis, the end of the pipeline between the liquid container 130 and the plunger pump 110 that is in communication with the liquid container 130 may be located above each settling plate, so that the liquid transported to the plunger pump 110 is basically the portion with relatively high cleanliness in the upper region of the liquid container 130, so as to reduce the probability of the plunger pump 110 being affected by impurities and causing failure.

[0037] More specifically, a plurality of the above-mentioned sedimentation plates may be arranged in the liquid container 130, and a filter 140 may be arranged on the pipeline between the liquid container 130 and the plunger pump 110, so as to further improve the cleanliness of the liquid delivered to the plunger pump 110 and ensure that the service life of the plunger pump 110 is relatively long.

[0038] In order to further improve the working accuracy and reliability during the mining process, in the coalbed methane mining device disclosed in the embodiment of the present application, the liquid supply component 100 may also include a flow sensor 160, which is arranged on the pipeline between the liquid container 130 and the plunger pump 110, so that the flow sensor 160 can detect the flow of the power liquid input into the plunger pump 110, and when the actual value of the flow is too much lower than the preset value, the staff can inspect the device to confirm whether there is insufficient liquid in the liquid container 130 or a fault light of the plunger pump 110. Of course, the flow sensor 160 can also be connected to the controller of the coalbed methane mining device, so that when the detection data of the flow sensor 160 is abnormal, the controller automatically detects whether the components in the device are working normally or directly shuts down for inspection.

[0039] Furthermore, in the coalbed methane extraction device disclosed in the embodiment of the present application, the liquid supply component 100 may also include a pressure sensor 170, and the pressure sensor 170 is arranged at the discharge end of the plunger pump 110 to detect the output pressure of the discharge end of the plunger pump 110 to the power fluid. Accordingly, when the output pressure of the plunger pump 110 is too high or too low, it means that at least one of the operating pump component and the plunger pump 110 may be faulty, so as to ensure that the staff can check and repair it in time. Of course, the pressure sensor 170 can also be connected to the controller of the coalbed methane extraction device, so that when the detection value of the pressure sensor 170 does not meet the preset range, the controller can automatically control the extraction process to stop working, so as to prevent more serious consequences.

[0040] In addition, the normal parameter ranges of the above-mentioned liquid level sensor 150, flow sensor 160 and pressure sensor 170 can be flexibly determined according to actual conditions, and the actual values ​​of each parameter range can be determined according to different displacement requirements of the piston pump 300 in different coalbed methane production stages.

[0041] As described above, the liquid supply assembly 100 includes a liquid container 130, a frequency converter 120 and a plunger pump 110. Optionally, the three are independently arranged, and after being transported to the work site, the relative positions of the three are flexibly controlled based on the specific conditions of the work site, and the three are connected to each other in a corresponding manner.

[0042] In another embodiment of the present application, the liquid supply assembly 100 can also include a skid body, and the plunger pump 110, the frequency converter 120 and the liquid container 130 are all installed on the skid body, so that in the process of transporting the coalbed methane mining device, the aforementioned components of the liquid supply assembly 100 can be transported together, which can reduce the difficulty of transporting the liquid supply assembly 100, and when the liquid supply assembly 100 is transported to the work site, it is only necessary to install the corresponding pipelines on the liquid container 130 and the plunger pump 110 to complete the assembly of the liquid supply assembly 100, which can greatly reduce the difficulty of disassembly and assembly of the liquid supply assembly 100.

[0043] As described above, during the coalbed methane extraction process, the coalbed methane will be mixed in the return fluid and extracted together by the piston pump 300. In order to prevent too much coalbed methane from being sent into the connector inner tube 381, causing the piston pump 300 to be gas locked, in the coalbed methane extraction device disclosed in the embodiment of the present application, the operating pump assembly may also include a gas anchor, and the gas anchor is arranged at the end of the connector inner tube 381 away from the gas production tree, so as to utilize the gas anchor to separate the gas from the return fluid as much as possible, and the coalbed methane can be transported to the gas production tree assembly through the connector outer tube 382, ​​thereby ensuring that the piston pump 300 has a high working efficiency.

[0044] As described above, in the coalbed methane extraction device disclosed in the embodiment of the present application, the return liquid port of the gas production tree assembly can be connected to the liquid container 130, so as to realize the reuse of the power fluid, and the impurities in the return liquid can be filtered out by setting at least one of the filter 140 and the multi-layer sedimentation plate, thereby ensuring that the cleanliness of the power fluid delivered to the plunger pump 110 is relatively high.

[0045] In another embodiment of the present application, the operating pump assembly may further include a screen tube and a sand settling tube, wherein the screen tube and the sand settling tube are both connected to one end of the connector inner tube 381 away from the gas production tree assembly, so as to use the screen tube and the sand settling tube to pre-filter the return fluid extracted by the piston pump 300, and try to remove impurities such as gravel mixed in the return fluid extracted by the piston pump 300, thereby improving the cleanliness of the return fluid from the source, and preventing impurities from adversely affecting the normal operation and service life of the piston pump 300.

[0046] It should be noted that, in this article, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0047] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

Claims

1. A coalbed methane mining device, characterized in that: The invention comprises a liquid supply assembly, a gas tree assembly and an operation pump assembly, wherein the liquid supply assembly comprises a plunger pump, a motor, a frequency converter and a liquid container, wherein the frequency converter is electrically connected to the motor, and the motor is connected to the plunger pump, and the liquid container is connected to the liquid inlet end of the plunger pump; The gas tree assembly is provided with a liquid inlet, a return liquid outlet, a liquid outlet and a gas outlet, and the liquid inlet is connected to the liquid discharge end of the plunger pump; The working pump assembly includes a piston pump and a pipeline assembly. The piston pump is provided with a connector inner tube and a connector outer tube. The connector inner tube is connected to the liquid outlet through the pipeline assembly, and the connector outer tube is connected to both the return liquid port and the air outlet through the pipeline assembly.

2. The coalbed methane mining device according to claim 1, characterized in that: The drainback port is in communication with the liquid receiving member.

3. The coalbed methane mining device according to claim 2, characterized in that: A filter is provided on the pipeline between the liquid container and the plunger pump; And / or a plurality of sedimentation plates are provided in the liquid container, the plurality of sedimentation plates are spaced apart in the vertical direction, and an end of the pipeline between the liquid container and the plunger pump that is connected to the liquid container is located above each of the sedimentation plates.

4. The coalbed methane mining device according to claim 2, characterized in that: The liquid supply assembly further includes a liquid level sensor, which is disposed in the liquid container.

5. The coalbed methane mining device according to claim 2, characterized in that: The liquid supply assembly further includes a flow sensor, which is disposed on a pipeline between the liquid container and the plunger pump.

6. The coalbed methane mining device according to claim 2, characterized in that: The liquid supply assembly also includes a pressure sensor, which is arranged at the discharge end of the plunger pump.

7. The coalbed methane mining device according to claim 1, characterized in that: The piston pump comprises a double-acting piston pump.

8. The coalbed methane mining device according to claim 1, characterized in that: The liquid supply assembly further comprises a skid, and the plunger pump, the frequency converter and the liquid container are all mounted on the skid.

9. The coalbed methane mining device according to claim 1, characterized in that: The working pump assembly further comprises an air anchor, and the air anchor is arranged at one end of the connector inner tube away from the gas tree assembly.

10. The coalbed methane mining device according to claim 1, characterized in that: The working pump assembly further comprises a screen tube and a sand settling pipe, wherein the screen tube and the sand settling pipe are both connected to an end of the connector inner tube away from the gas tree assembly.

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