Downhole liquid drainage device

Abstract

The invention relates to the technical field of coal-bed gas drainage and gas recovery, in particular to an underground liquid drainage device which comprises a shaft assembly, a liquid drainage device, a liquid drainage device and a liquid drainage device, and the shaft assembly is used for being arranged in a coal-bed gas well; the hydraulic pump assembly is arranged at the bottom end of the shaft assembly; the injection pump assembly is arranged on the shaft assembly, communicates with the hydraulic pump assembly and is located above the hydraulic pump assembly; the setting assembly is used for replacing the injection pump assembly; wherein under the condition that the liquid displacement of the coal-bed gas well is larger than or equal to 25 cubic meters per day, the hydraulic pump assembly serves as a liquid channel, and liquid in the coal-bed gas well is discharged through the injection pump assembly; under the condition that the liquid displacement of the coal-bed gas well is smaller than 25 cubic meters per day, the setting assembly is adopted to replace the injection pump assembly, the setting assembly serves as a liquid channel, liquid in the coal-bed gas well is discharged through the hydraulic pump assembly, and the device is suitable for coal-bed gas wells with different displacements. In addition, liquid drainage can be achieved only by replacing the used pump body, and the replacement operation and the operation process are simple.

Description

Technical Field

[0001] The present invention relates to the technical field of coalbed methane drainage and gas production, and more specifically, the present invention relates to a downhole liquid drainage device. Background Art

[0002] Currently, coalbed methane is mainly drained and gas produced by equipment such as pumping units, screw pumps, and electrical submersible pumps, which to a certain extent ensures the normal production of coalbed methane wells. However, the currently developed deep coalbed methane wells have a large burial depth, a high salinity, and a wide range of liquid discharge and gas production throughout the life cycle. Due to the large range of exhaust gas flow, the current downhole liquid drainage devices have great inadaptability and are difficult to cope with the scenarios of liquid discharge changes.

[0003] Therefore, it is necessary to propose a downhole liquid drainage device to at least partially solve the problems existing in the prior art. Summary of the Invention

[0004] A series of simplified concepts are introduced in the Summary of the Invention section, which will be further elaborated in detail in the Detailed Description section. The Summary of the Invention section of the present invention does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the protection scope of the claimed technical solution.

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art or related technologies.

[0006] To this end, the present invention provides a downhole liquid drainage device.

[0007] In view of this, according to an embodiment of the present application, a downhole liquid drainage device is proposed, including:

[0008] A wellbore assembly for being disposed in a coalbed methane well;

[0009] A hydraulic pump assembly disposed at the bottom end of the above-mentioned wellbore assembly;

[0010] An ejector pump assembly disposed in the above-mentioned wellbore assembly, communicating with the above-mentioned hydraulic pump assembly, and located above the above-mentioned hydraulic pump assembly;

[0011] A setting assembly for replacing the above-mentioned ejector pump assembly;

[0012] Wherein, when the liquid discharge of the above-mentioned coalbed methane well is greater than or equal to 25 cubic meters per day, the above-mentioned hydraulic pump assembly serves as a liquid passage, and the liquid under the above-mentioned coalbed methane well is discharged through the above-mentioned ejector pump assembly;

[0013] When the liquid displacement of the coalbed methane well is less than 25 cubic meters per day, the above-mentioned setting packer assembly is used to replace the above-mentioned jet pump assembly. The above-mentioned setting packer assembly serves as a liquid passage, and the liquid under the coalbed methane well is discharged through the above-mentioned hydraulic pump assembly.

[0014] In a feasible implementation manner, the above-mentioned wellbore assembly includes:

[0015] A plurality of pipe sections;

[0016] A joint, arranged between adjacent above-mentioned pipe sections;

[0017] Wherein, each pipe section is provided with a first sleeve and a second sleeve. The above-mentioned first sleeve is sleeved on the above-mentioned second sleeve, and an annular space is formed between the above-mentioned first sleeve and the above-mentioned second sleeve. The above-mentioned hydraulic pump assembly and the above-mentioned jet pump assembly are arranged in the above-mentioned second sleeve.

[0018] In a feasible implementation manner, the above-mentioned jet pump assembly includes:

[0019] A pump core, arranged in the above-mentioned second sleeve;

[0020] A first fishing joint, connected to one end of the above-mentioned pump core away from the above-mentioned hydraulic pump assembly;

[0021] A nozzle, arranged at one end of the above-mentioned pump core close to the above-mentioned hydraulic pump assembly;

[0022] A diffuser tube, arranged below the above-mentioned nozzle;

[0023] A throat tube, arranged between the above-mentioned nozzle and the above-mentioned diffuser tube;

[0024] A liquid outlet, communicated with the above-mentioned diffuser tube and located below the above-mentioned diffuser tube.

[0025] In a feasible implementation manner, the above-mentioned hydraulic pump assembly includes:

[0026] A hydraulic pump body, communicated with the above-mentioned annular space;

[0027] A plunger, arranged inside the above-mentioned hydraulic pump body and used for reciprocating motion inside the above-mentioned hydraulic pump body.

[0028] In a feasible implementation manner, the above-mentioned downhole liquid drainage device further includes: a first buffer member. A plurality of the above-mentioned hydraulic pump assemblies are arranged along the arrangement direction of the above-mentioned wellbore assembly, and the above-mentioned first buffer member is arranged between two adjacent above-mentioned hydraulic pump assemblies;

[0029] A second buffer member, arranged between the above-mentioned plunger close to the above-mentioned jet pump assembly and the above-mentioned jet pump assembly.

[0030] In a feasible implementation manner, the above-mentioned first buffer member includes:

[0031] A first buffer body, and a first insertion block is provided at the bottom end of the first buffer body;

[0032] A second buffer body, which is arranged below the first buffer body, and a first insertion slot is provided on the end face of the second buffer body facing the first buffer body, and the position of the first insertion block corresponds to the position of the first insertion slot;

[0033] The above-mentioned second buffer member includes:

[0034] A third buffer body, and a second insertion slot is provided at the bottom end of the third buffer body;

[0035] A fourth buffer body, which is arranged below the first buffer body, and a second insertion block is provided on the end face of the fourth buffer body facing the third buffer body, and the position of the second insertion block corresponds to the position of the second insertion slot;

[0036] Wherein, when the plunger moves in a direction away from the injection pump assembly, the first buffer body moves towards the second buffer body, and the first insertion block is inserted into the first insertion slot;

[0037] When the plunger moves in a direction close to the injection pump assembly, the fourth buffer body moves towards the third buffer body, and the second insertion block is inserted into the second insertion slot.

[0038] In a feasible implementation manner, the above-mentioned packer assembly includes:

[0039] A packer string, which is used to be arranged in the second sleeve, and the packer string is communicated with the hydraulic pump assembly;

[0040] A second fishing joint, which is connected to the top end of the packer string;

[0041] A sealing ring, which is arranged on the circumferential side of the packer string.

[0042] In a feasible implementation manner, the above-mentioned downhole liquid drainage device further includes:

[0043] A traveling valve, which is arranged between adjacent above-mentioned plungers, and between the inlet pipe of the hydraulic pump assembly and the above-mentioned plunger adjacent to the inlet pipe.

[0044] In a feasible implementation manner, the above-mentioned downhole liquid drainage device further includes:

[0045] A screen pipe, which is arranged at the bottom of the above-mentioned wellbore assembly.

[0046] In a feasible implementation manner, the above-mentioned downhole liquid drainage device further includes:

[0047] A fixed valve is arranged between the above-mentioned screen pipe and the above-mentioned hydraulic pump body near the bottom of the above-mentioned wellbore assembly.

[0048] Compared with the prior art, the present invention has at least the following beneficial effects: The downhole liquid drainage device provided by the embodiments of the present application is provided with a wellbore assembly, a hydraulic pump assembly, a jet pump assembly and a setting assembly. Among them, the wellbore assembly is arranged in the coalbed methane well, and the hydraulic pump group is arranged at the bottom end of the coalbed methane well. The liquid in the coalbed methane well can be pumped to the ground through the hydraulic pump group. The jet pump assembly is arranged in the wellbore assembly and is connected to the hydraulic pump assembly and is located above the hydraulic pump assembly. The liquid in the coalbed methane well can be pumped to the ground through the jet pump assembly. Specifically, when the liquid discharge rate of the coalbed methane well is greater than or equal to 25 cubic meters per day, it indicates that the discharge rate of the coalbed methane well is relatively large, and the liquid can be discharged without a large pumping force. At this time, the hydraulic pump assembly only serves as a liquid channel, and the liquid in the coalbed methane well is pumped to the ground through the jet pump assembly through the liquid channel. When the liquid discharge rate of the coalbed methane well is less than 25 cubic meters per day, it indicates that the discharge rate of the coalbed methane well is relatively small, and a large pumping force is required to discharge the liquid. At this time, the jet pump assembly is taken out, and the setting assembly is replaced with the jet pump assembly and placed at the position of the jet pump assembly. The setting assembly can serve as a liquid channel, and the liquid in the coalbed methane well is pumped to the ground through the hydraulic pump assembly through the liquid channel. With such a setting, it can be applicable to coalbed methane wells with different discharge rates, improving adaptability. And only by replacing the used pump body can the liquid drainage be realized. The replacement operation and the operation process are relatively simple and more targeted.

[0049] For the downhole liquid drainage device provided by the present invention, other advantages, objectives and features of the present invention will be partially reflected by the following description, and will also be understood by those skilled in the art through the research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of this specification. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0051] Figure 1 It is a schematic structural diagram of a downhole liquid drainage device provided by an embodiment of the present application;

[0052] Figure 2 It is a schematic structural diagram of a jet pump assembly provided by an embodiment of the present application.

[0053] Among them, Figure 1 and Figure 2 The corresponding relationship between the reference numerals and the component names in the drawings is as follows:

[0054] 110 Wellbore assembly, 111 pipe section, 1111 first sleeve, 1112 second sleeve, 1113 annular space, 112 joint, 120 hydraulic pump assembly, 121 hydraulic pump body, 122 plunger, 123 inlet pipe, 130 jet pump assembly, 131 pump core, 132 first fishing joint, 133 nozzle, 134 diffuser pipe, 135 throat pipe, 136 liquid outlet, 140 packer assembly, 141 packer string, 142 second fishing joint, 143 sealing ring, 150 first buffer, 151 first buffer body, 152 second buffer body, 153 first slot, 154 first plug, 160 second buffer, 161 third buffer body, 162 fourth buffer body, 163 second slot, 164 second plug, 170 traveling valve, 180 screen pipe, 190 fixed valve. Detailed implementation mode

[0055] In order to better understand the above technical solutions, the technical solutions of the embodiments of the present application will be described in detail below through the accompanying drawings and specific embodiments. It should be understood that the specific features in the embodiments of the present application and the embodiments are detailed descriptions of the technical solutions of the embodiments of the present application, rather than limitations on the technical solutions of the present application. Without conflict, the technical features in the embodiments of the present application and the embodiments can be combined with each other.

[0056] As Figure 1 and Figure 2 shown, a downhole liquid drainage device is proposed according to an embodiment of the present application, including: a wellbore assembly 110 for being arranged in a coalbed methane well; a hydraulic pump assembly 120 arranged at the bottom end of the above wellbore assembly 110; a jet pump assembly 130 arranged in the above wellbore assembly 110, communicated with the above hydraulic pump assembly 120, and located above the above hydraulic pump assembly 120; a packer assembly 140 for replacing the above jet pump assembly 130; wherein, when the liquid discharge rate of the above coalbed methane well is greater than or equal to 25 cubic meters per day, the above hydraulic pump assembly 120 serves as a liquid channel, and the liquid under the above coalbed methane well is discharged through the above jet pump assembly 130; when the liquid discharge rate of the coalbed methane well is less than 25 cubic meters per day, the above packer assembly 140 is used to replace the above jet pump assembly 130, the above packer assembly 140 serves as a liquid channel, and the liquid under the above coalbed methane well is discharged through the above hydraulic pump assembly 120.

[0057] It can be understood that the downhole liquid drainage device provided by the embodiments of the present application is provided with a wellbore assembly 110, a hydraulic pump assembly 120, a jet pump assembly 130, and a setting assembly 140. Among them, the wellbore assembly 110 is arranged in the coalbed methane well, and the hydraulic pump assembly is arranged at the bottom of the coalbed methane well, and the liquid in the coalbed methane well can be pumped to the ground through the hydraulic pump assembly. The jet pump assembly 130 is arranged in the wellbore assembly 110 and is connected to the hydraulic pump assembly 120, and is located above the hydraulic pump assembly 120. The liquid in the coalbed methane well can be pumped to the ground through the jet pump assembly 130. Specifically, when the liquid discharge of the coalbed methane well is greater than or equal to 25 cubic meters per day, it indicates that the discharge of the coalbed methane well is relatively large, and the liquid can be discharged without a large pumping force. At this time, the hydraulic pump assembly 120 only serves as a liquid passage, and the liquid in the coalbed methane well is pumped to the ground through the jet pump assembly 130 through the liquid passage. When the liquid discharge of the coalbed methane well is less than 25 cubic meters per day, it indicates that the discharge of the coalbed methane well is relatively small, and a large pumping force is required to discharge the liquid. At this time, the jet pump assembly 130 is taken out, and the setting assembly 140 is used to replace the jet pump assembly 130 and is placed at the position of the jet pump assembly 130. The setting assembly 140 can serve as a liquid passage, and the liquid in the coalbed methane well is pumped to the ground through the hydraulic pump assembly 120 through the liquid passage. With such a setting, it can be applicable to coalbed methane wells with different discharges, improving the adaptability. And only by replacing the used pump body can the liquid drainage be realized. The replacement operation and the operation process are relatively simple and more targeted.

[0058] In some examples, such as Figure 1 shown, the above-mentioned wellbore assembly 110 includes: a plurality of pipe sections 111; a joint 112, arranged between adjacent pipe sections 111; among them, each pipe section 111 is provided with a first sleeve 1111 and a second sleeve 1112, the first sleeve 1111 is sleeved on the second sleeve 1112, and an annular space 1113 is formed between the first sleeve 1111 and the second sleeve 1112, and the hydraulic pump assembly 120 and the jet pump assembly 130 are arranged in the second sleeve 1112.

[0059] It can be understood that the wellbore assembly 110 is provided with a plurality of pipe segments 111 and joints 112. According to the actual situation, the plurality of pipe segments 111 can be connected through the joints 112 to meet the depth requirements of the coalbed methane well. Specifically, each pipe segment 111 is provided with a first sleeve 1111 and a second sleeve 1112, and the first sleeve 1111 is sleeved on the second sleeve 1112. An annular space 1113 is formed between the first sleeve 1111 and the second sleeve 1112, and the annular space 1113 can be used as a liquid flow channel. Threads are provided on the end faces of both the first sleeve 1111 and the second sleeve 1112, and the joint 112 is provided with corresponding threads. The first sleeve 1111 is connected to the joint 112 and the second sleeve 1112 is connected to the joint 112 by means of threaded connection. The second sleeve 1112 is a hollow pipe string, and both the hydraulic pump assembly 120 and the jet pump assembly 130 are arranged inside the second sleeve 1112.

[0060] Exemplarily, according to the actual situation, the number of pipe segments 111 is determined to be three, namely the first pipe segment 111, the second pipe segment 111, and the third pipe segment 111. Among them, the first pipe segment 111 is located at the topmost position, and the first pipe segment 111 and the second pipe segment 111 are connected by the first joint 112. The third pipe segment 111 is located at the bottommost position, and the second pipe segment 111 and the third pipe segment 111 are connected by the second joint 112. The jet pump assembly 130 is arranged inside the second sleeve 1112 of the first pipe segment 111. There are two hydraulic pump assemblies 120, which are respectively arranged inside the second sleeve 1112 of the second pipe segment 111 and inside the second sleeve 1112 of the third pipe segment 111. The three pipe segments 111 communicate with each other to form a liquid channel.

[0061] In some examples, such as Figure 1 and Figure 2 shown, the above-mentioned jet pump assembly 130 includes: a pump core 131, arranged inside the above-mentioned second sleeve 1112; a first fishing joint 132, connected to one end of the above-mentioned pump core 131 far from the above-mentioned hydraulic pump assembly 120; a nozzle 133, arranged at one end of the above-mentioned pump core 131 close to the above-mentioned hydraulic pump assembly 120; a diffuser tube 134, arranged below the above-mentioned nozzle 133; a throat tube 135, arranged between the above-mentioned nozzle 133 and the above-mentioned diffuser tube 134; a liquid outlet 136, communicating with the above-mentioned diffuser tube 134 and located below the above-mentioned diffuser tube 134.

[0062] It is understandable that the jet pump assembly 130 is provided with a pump core 131, a first fishing joint 132, a nozzle 133, a diffuser tube 134, a throat tube 135, and a liquid outlet 136. Among them, the pump core 131 is fixed within the second sleeve 1112 of the topmost pipe section 111. The first fishing joint 132 is connected to the top end of the pump core 131, so as to facilitate fixing the first fishing joint 132 through a hoisting tool and pulling out the jet pump assembly 130 from the second sleeve 1112 to improve the replacement efficiency. The nozzle 133 is arranged at one end of the pump core 131 close to the hydraulic pump assembly 120. The diffuser tube 134 is arranged below the nozzle 133, and the throat tube 135 is arranged between the nozzle 133 and the diffuser tube 134. And the liquid outlet 136 communicates with the diffuser tube 134 and communicates with the ground to discharge the liquid in the coalbed methane well to the ground through the liquid outlet 136. The liquid outlet 136 is located below the diffuser tube 134.

[0063] It should be noted that when the jet pump assembly 130 is used to discharge the liquid in the coalbed methane well, the pressurized liquid can be conveyed to the nozzle 133 through the top end of the second sleeve 1112 at the ground and enter the liquid outlet 136 after passing through the diffuser tube 134. Due to the action of the pressurized liquid, the pressure from the pump core 131 to the diffuser tube 134 is relatively large, and the pressure below the diffuser tube 134 is relatively small. In order to balance the pressure, the liquid in the coalbed methane well is sucked upward. At this time, the plunger 122 of the hydraulic pump assembly 120 moves to the topmost end of the hydraulic pump body 121 under the pressure of the discharged liquid, and the liquid reaches the diffuser tube 134 through the liquid channel of the hydraulic pump assembly 120. After forming a mixed liquid with the pressurized liquid at the liquid outlet 136, it is discharged to the ground.

[0064] It should be noted that in order to increase the displacement of the jet pump assembly 130 during operation, the diameter of the pump core 131 can be appropriately increased according to the size of the coalbed methane well.

[0065] In some examples, such as Figure 1 and Figure 2 as shown, the above-mentioned hydraulic pump assembly 120 includes: a hydraulic pump body 121, which communicates with the above-mentioned annular space 1113; a plunger 122, which is arranged inside the above-mentioned hydraulic pump body 121 and is used for reciprocating motion inside the above-mentioned hydraulic pump body 121.

[0066] It can be understood that the hydraulic pump assembly 120 is provided with a hydraulic pump body 121 and a plunger 122. Among them, a liquid passage is formed inside the hydraulic pump body 121, and the plunger 122 is arranged inside the hydraulic pump body 121 and can reciprocate inside the hydraulic pump body 121. The cavity inside the hydraulic pump body 121 where the plunger 122 is arranged serves as the rod chamber, and the cavity between the plunger 122 and the end face of the hydraulic pump body 121 serves as the rodless chamber. The hydraulic pump body 121 communicates with the annular space 1113. With such a setting, when the liquid discharge of the coalbed methane well meets the requirement of being discharged using the hydraulic pump assembly 120, the jet pump assembly 130 is removed, and the setting packer assembly 140 is installed at the position of the jet pump assembly 130. The pressurized liquid can be transported to the rodless chamber through the second sleeve 1112 at the ground, pushing the plunger 122 to move downward. The plunger 122 squeezes the liquid in the rod chamber into the annular space 1113. At this time, a negative pressure is formed in the rodless chamber, causing the liquid to enter the rodless chamber. The plunger 122 moves downward until the maximum stroke. At the ground, the direction of the pressurized liquid is changed so that the pressurized liquid enters the rod chamber from the annular space 1113, pushing the plunger 122 to move upward. The plunger 122 squeezes the liquid in the rodless chamber and discharges it to the ground through the liquid passage of the setting packer assembly 140. By repeatedly changing the transport direction of the ground pressurized liquid in this way, the plunger 122 reciprocates inside the hydraulic pump body 121, thereby realizing the continuous discharge of the liquid in the coalbed methane well.

[0067] In some examples, such as Figure 1 and Figure 2 shown, the above downhole liquid drainage device further includes: a first buffer member 150. A plurality of the above hydraulic pump assemblies 120 are provided, and the plurality of the above hydraulic pump assemblies 120 are arranged along the setting direction of the above wellbore assembly 110. The first buffer member 150 is arranged between two adjacent ones of the above hydraulic pump assemblies 120; a second buffer member 160, arranged between the above plunger 122 close to the above jet pump assembly 130 and the above jet pump assembly 130.

[0068] It is understandable that the downhole liquid discharging device is also provided with a first buffer member 150 and a second buffer member 160. Specifically, a plurality of plungers 122 can be provided according to the actual length of the hydraulic pump body 121, and the plurality of plungers 122 are arranged along the arrangement direction of the wellbore assembly 110. The first buffer member 150 is arranged between two adjacent plungers 122 to prevent the impact generated by one plunger 122 on the adjacent plunger 122 from being too large during the reciprocating motion, which may cause damage to the plunger 122, affect the service life of the plunger 122, shorten the replacement period, and increase the use cost. At the same time, a second buffer member 160 is arranged between the plunger 122 closest to the jet pump assembly 130 and the jet pump assembly 130. Specifically, the second buffer member 160 can be arranged in the rodless cavity of the hydraulic pump body 121 to prevent the impact generated by the upward movement of the plunger 122 on the hydraulic pump body 121 from being too large, which may cause damage to the hydraulic pump body 121, affect the service life of the hydraulic pump body 121, shorten the replacement period, and increase the use cost. A conveying channel is formed in the middle of the first buffer member 150 and the second buffer member 160, and the conveying channels are respectively communicated with the hydraulic pump assembly 120 and the jet pump assembly 130 to ensure smooth liquid conveyance.

[0069] In some examples, such as Figure 1 and Figure 2 shown, the above-mentioned first buffer member 150 includes: a first buffer body 151, and a first insertion block 154 is provided at the bottom end of the first buffer body 151; a second buffer body 152, which is arranged below the first buffer body 151, and a first slot 153 is provided on the end face of the second buffer body 152 facing the first buffer body 151, and the position of the first insertion block 154 corresponds to the position of the first slot 153; the above-mentioned second buffer member 160 includes: a third buffer body 161, and a second slot 163 is provided at the bottom end of the third buffer body 161; a fourth buffer body 162, which is arranged below the first buffer body 151, and a second insertion block 164 is provided on the end face of the fourth buffer body 162 facing the third buffer body 161, and the position of the second insertion block 164 corresponds to the position of the second slot 163; wherein, when the plunger 122 moves in a direction away from the jet pump assembly 130, the first buffer body 151 moves towards the second buffer body 152, and the first insertion block 154 is inserted into the first slot 153; when the plunger 122 moves in a direction close to the jet pump assembly 130, the fourth buffer body 162 moves towards the third buffer body 161, and the second insertion block 164 is inserted into the second slot 163.

[0070] It can be understood that the first buffer member 150 is provided with a first buffer body 151 and a second buffer body 152. Through the mutual cooperation of the first buffer body 151 and the second buffer body 152, when the plunger 122 reciprocates, the impact force generated on the adjacent plunger 122 is reduced. Specifically, the second buffer body 152 is located below the first buffer body 151, and a first insertion block 154 is provided on the end face of the first buffer body 151 facing the second buffer body 152, and a first slot 153 is provided on the end face of the second buffer body 152 facing the first buffer body 151, and the positions of the first insertion block 154 and the first slot 153 correspond to each other. With such a setting, when the plunger 122 moves in a direction away from the injection pump assembly 130, the plunger 122 pushes the first buffer body 151 downward, causing the first insertion block 154 to be inserted into the first slot 153, thereby absorbing the impact force of the plunger 122 and achieving a buffering effect. This avoids the situation where when the plunger 122 moves in a direction away from the injection pump assembly 130, the impact on the adjacent plunger 122 is too large, causing damage to the plunger 122, affecting the service life of the plunger 122, shortening the replacement cycle, and increasing the use cost.

[0071] The second buffer member 160 is provided with a third buffer body 161 and a fourth buffer body 162. Through the mutual cooperation of the third buffer body 161 and the fourth buffer body 162, when the plunger 122 reciprocates, the impact force generated on the injection pump assembly 130 and the joint 112 of the pipe string is reduced. Specifically, the fourth buffer body 162 is located below the third buffer body 161, and a second slot 163 is provided on the end face of the third buffer body 161 facing the fourth buffer body 162, and a second insertion block 164 is provided on the end face of the fourth buffer body 162 facing the third buffer body 161, and the positions of the second insertion block 164 and the second slot 163 correspond to each other. With such a setting, when the plunger 122 moves in a direction close to the injection pump assembly 130, the plunger 122 pushes the third buffer body 161 upward, causing the second insertion block 164 to be inserted into the second slot 163, thereby absorbing the impact force of the plunger 122 and achieving a buffering effect. This avoids the situation where when the plunger 122 moves in a direction close to the injection pump assembly 130, the impact on the injection pump assembly 130 and the corresponding joint 112 of the pipe string is too large, causing damage to the plunger 122, the injection pump assembly 130, and the joint 112, affecting the service life, shortening the replacement cycle, and increasing the use cost.

[0072] Exemplarily, the hydraulic pump assembly 120 is provided with two plungers 122 in total. The first plunger 122 is closer to the injection pump assembly 130, and the second plunger 122 is farther away from the injection pump assembly 130. The first plunger 122 is arranged in the second pipe section 111, and the second plunger 122 is arranged in the third pipe section 111. The first buffer body 151 is arranged in the second pipe section 111 and is threadedly connected to the joint 112 between the first pipe section 111 and the second pipe section 111. The top end of the first plunger 122 can be threadedly connected to the bottom of the second buffer body 152, and the bottom end of the first plunger 122 can be threadedly connected to the top of the third buffer body 161. The fourth buffer body 162 is located in the second pipe section 111 and is threadedly connected to the joint 112 between the second pipe section 111 and the third pipe section 111.

[0073] Exemplarily, the diameter of the first plunger 122 is 63 mm to 70 mm, and the diameter of the second plunger 122 is 32 mm to 38 mm; the outer diameter of the hydraulic pump body 121 is 101.6 mm to 108 mm, and the length of the hydraulic pump body 121 is 8 m to 12 m; the outer diameter of the injection pump assembly 130 is 76 mm to 92 mm, the outer diameter of the pump core 131 is 27 mm to 42 mm, and the length of the injection pump assembly 130 is 900 mm to 1590 mm.

[0074] In some examples, such as Figure 1 and Figure 2 shown, the above-mentioned packer assembly 140 includes: a packer string 141 for being arranged in the above-mentioned second sleeve 1112, and the packer string 141 communicates with the above-mentioned hydraulic pump assembly 120; a second fishing joint 142 connected to the top end of the packer string 141; and a sealing ring 143 arranged on the circumferential side of the packer string 141.

[0075] It can be understood that the packer assembly 140 is provided with a packer string 141, a second fishing joint 142 and a sealing ring 143. Among them, the packer string 141 is a hollow pipe string, and a liquid flow channel is formed inside it. The second fishing joint 142 is connected to the top end of the packer string 141. After the injection pump assembly 130 is removed and removed from the second sleeve 1112 by connecting the first fishing joint 132 with a lifting tool, the lifting tool can be used to connect the second fishing joint 142 to move the packer string 141 to the installation position of the original injection pump assembly 130 for installation. The size of the packer string 141 is the same as that of the injection pump assembly 130, so as to facilitate installation and disassembly, improve efficiency and reduce the operation difficulty. Two sealing rings 143 can be provided, one of which is located on the circumferential side of the top end of the packer string 141, and the other is located on the circumferential side of the bottom end of the packer string 141.

[0076] In some examples, such as Figure 1 and Figure 2As shown, the above-mentioned downhole liquid discharging device further includes: a traveling valve 170, which is arranged between adjacent ones of the above-mentioned plungers 122, and between the inlet pipe 123 of the above-mentioned hydraulic pump assembly 120 and the above-mentioned plunger 122 adjacent to the above-mentioned inlet pipe 123.

[0077] It can be understood that the downhole liquid discharging device is also provided with a traveling valve 170. The traveling valve 170 can be arranged between adjacent plungers 122, can reciprocate with the plunger 122, and can act as a one-way ball valve. When the liquid is discharged upward, the traveling valve 170 is in a closed state to prevent the liquid from flowing back and ensure the normal discharge of the liquid. An inlet pipe 123 can be arranged at the bottom end of the hydraulic pump body 121, and the liquid can enter the rod chamber of the hydraulic pump body 121 from the inlet pipe 123 to push the plunger 122 to move upward. The traveling valve 170 can be arranged between the inlet pipe 123 and the plunger 122 adjacent to the inlet pipe 123. Thus, when the liquid is discharged upward, it is ensured that the liquid does not flow back from the inlet pipe 123 and the normal discharge of the liquid is ensured.

[0078] In some examples, such as Figure 1 As shown, the above-mentioned downhole liquid discharging device further includes: a screen pipe 180, which is arranged at the bottom of the above-mentioned wellbore assembly 110.

[0079] It can be understood that the downhole liquid discharging device is also provided with a screen pipe 180, and the screen pipe 180 can be connected to the bottom of the wellbore assembly 110 through a joint 112. The impurities in the liquid in the coalbed methane well can be screened out through the screen pipe 180 to ensure smooth liquid transportation and avoid impurities blocking the liquid channel.

[0080] In some examples, such as Figure 1 and Figure 2 As shown, the above-mentioned downhole liquid discharging device further includes: a fixed valve 190, which is arranged between the above-mentioned screen pipe 180 and the above-mentioned hydraulic pump body 121 close to the bottom of the above-mentioned wellbore assembly 110.

[0081] It can be understood that the downhole liquid discharging device is also provided with a fixed valve 190. Specifically, the fixed valve 190 is arranged between the joint 112 of the screen pipe 180 and the hydraulic pump body 121 close to the bottom of the wellbore assembly 110. The fixed valve 190 acts as a one-way valve. When the liquid is discharged upward, it prevents the liquid from flowing back from the inlet pipe 123 and ensures the normal discharge of the liquid. Moreover, the fixed valve 190 has a small torque, a small deformation amount of the valve seat, stable sealing performance, and a long service life.

[0082] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "rear", etc. is based on the orientation or positional relationship shown in the drawings. These terms are only used for convenience in describing the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0083] In the description of this specification, the descriptions of terms such as "one embodiment", "some embodiments", "specific embodiments", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or instance. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0084] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An underground liquid drainage device, characterized in that, it includes: a wellbore assembly for being arranged in a coalbed methane well; a hydraulic pump assembly arranged at the bottom end of the wellbore assembly; an ejector pump assembly arranged in the wellbore assembly, communicated with the hydraulic pump assembly and located above the hydraulic pump assembly; a setting packer assembly for replacing the ejector pump assembly; wherein, when the liquid discharge of the coalbed methane well is greater than or equal to 25 cubic meters per day, the hydraulic pump assembly serves as a liquid passage, and the liquid under the coalbed methane well is discharged through the ejector pump assembly; when the liquid discharge of the coalbed methane well is less than 25 cubic meters per day, the setting packer assembly is used to replace the ejector pump assembly, and the setting packer assembly serves as a liquid passage, and the liquid under the coalbed methane well is discharged through the hydraulic pump assembly.

2. The underground liquid drainage device according to claim 1, characterized in that, the wellbore assembly includes: a plurality of pipe sections; a joint arranged between adjacent pipe sections; wherein, each pipe section is provided with a first sleeve and a second sleeve, the first sleeve is sleeved on the second sleeve, and an annular space is formed between the first sleeve and the second sleeve, and the hydraulic pump assembly and the ejector pump assembly are arranged in the second sleeve.

3. The underground liquid drainage device according to claim 2, characterized in that, the ejector pump assembly includes: a pump core arranged in the second sleeve; a first fishing joint connected to one end of the pump core away from the hydraulic pump assembly; a nozzle arranged at one end of the pump core close to the hydraulic pump assembly; a diffuser pipe arranged below the nozzle; a throat pipe arranged between the nozzle and the diffuser pipe; a liquid outlet communicated with the diffuser pipe and located below the diffuser pipe.

4. The underground liquid drainage device according to claim 2, characterized in that, the hydraulic pump assembly includes: a hydraulic pump body communicated with the annular space; a plunger arranged inside the hydraulic pump body and used for reciprocating motion inside the hydraulic pump body.

5. The underground liquid drainage device according to claim 4, characterized in that, it further includes: a first buffer member, there are a plurality of the hydraulic pump assemblies, and the plurality of hydraulic pump assemblies are arranged along the arrangement direction of the wellbore assembly, and the first buffer member is arranged between two adjacent hydraulic pump assemblies; a second buffer member arranged between the plunger close to the ejector pump assembly and the ejector pump assembly.

6. The underground liquid drainage device according to claim 5, characterized in that, the first buffer member includes: a first buffer body, and a first insertion block is arranged at the bottom end of the first buffer body; a second buffer body arranged below the first buffer body, and a first slot is arranged on the end face of the second buffer body facing the first buffer body, and the position of the first insertion block corresponds to the position of the first slot; the second buffer member includes: a third buffer body, and a second slot is arranged at the bottom end of the third buffer body; A fourth buffer body is arranged below the first buffer body, and a second insertion block is provided on an end face of the fourth buffer body facing the third buffer body, and a position of the second insertion block corresponds to a position of the second slot; Wherein, when the plunger moves in a direction away from the jet pump assembly, the first buffer body moves towards the second buffer body, and the first insertion block is inserted into the first slot; When the plunger moves in a direction close to the jet pump assembly, the fourth buffer body moves towards the third buffer body, and the second insertion block is inserted into the second slot.

7. The downhole liquid drainage device according to claim 2, characterized in that, The setting assembly includes: A setting string for being arranged in the second sleeve, and the setting string is communicated with the hydraulic pump assembly; A second fishing joint connected to a top end of the setting string; A sealing ring arranged on a peripheral side of the setting string.

8. The downhole liquid drainage device according to claim 4, characterized in that, It further includes: A traveling valve arranged between adjacent plungers and between an inlet pipe of the hydraulic pump assembly and the plunger adjacent to the inlet pipe.

9. The downhole liquid drainage device according to claim 4, characterized in that, It further includes: A screen pipe arranged at a bottom of the wellbore assembly.

10. The downhole liquid drainage device according to claim 9, characterized in that, It further includes: A fixed valve arranged between the screen pipe and the hydraulic pump body close to the bottom of the wellbore assembly.

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