A rotation-preventing load reducer for a liner pipe

Abstract

The application discloses a kind of anti-rotation type load reducing devices suitable for lining tubing, including external structure and internal structure;The top of the external structure is provided with tubing joint, and the top of the internal structure is provided with oil outlet joint;Two upper anti-rotation structures are provided on the radial outer circumferential surface of the oil outlet joint, and the two upper anti-rotation structures are symmetrical along the central axis of the inner hole of the oil outlet joint;Two lower anti-rotation structures are provided on the inner hole of the tubing joint, and the two lower anti-rotation structures are symmetrical along the central axis of the inner hole of the tubing joint;When working, by lowering the oil outlet joint, the upper anti-rotation structure on it enters the lower anti-rotation structure of the tubing joint, to prevent the oil outlet joint from rotating relative to the tubing joint, so as to ensure that the tubing does not rotate when the pipe string is disassembled, and the tubing is easy to disassemble. By using the anti-rotation mechanism of the load reducing device of the application, the rotation of the pipe string during construction can be prevented, and the safety of construction is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to an improvement of a rod pump deep pumping lifting load reducing device for oil field, in particular to an anti-rotation load reducing device applicable to a lined tubing. BACKGROUND

[0002] Low permeability reservoir is the main position of oil field development, generally the reservoir is buried deep, in order to improve the development effect, through deep pumping to enlarge the production pressure difference, to improve the oil well production and development benefit. Deepening pump hanging deep pumping will inevitably cause the increase of the suspension point load, and the reduction of the rod string life, therefore, the researchers have invented several load reducing devices. Through the load reducing device, not only the suspension point load of the pumping unit can be reduced, but also the rod string cyclic stress ratio can be reduced, to achieve the purpose of reducing cost and increasing efficiency and increasing the rod string life.

[0003] The patent with publication number CN201714351U discloses a rod pump deep pumping assisting device, comprising an oil pumping rod, a small pump cylinder, a small plunger, a large plunger, a tension pipe and a large pump cylinder. The large pump cylinder, the small pump cylinder, the small plunger, the large plunger and the liquid inlet connector are sequentially installed in the tension pipe. The upper end of the small plunger and the lower end of the large plunger and the liquid inlet connector are connected with the oil pumping rod. The small plunger and the large plunger and the liquid inlet connector are connected together. The present application has the characteristics of unlimited pump hanging depth, pump cylinder in cantilever beam state, eliminating the difficulty of rod string downstroke caused by the eccentricity of the plunger, improving the application reliability, reducing the suspension point load of the horse head, reducing the influence of rod string expansion and contraction on the oil pumping pump, improving the pump efficiency, and remarkable energy saving effect, which is widely applied in the rod pumping oil pumping deep pumping process of oil exploitation.

[0004] The patent with publication number CN202971147U discloses a deep pumping load reducing device, comprising a tension pipe and a large pump cylinder connected together, a small plunger and a large plunger are arranged in the pipe cavity formed by the above two. The small plunger is sleeved with a small pump cylinder and is suspended in the tension pipe through a suspension connector arranged on the outer side of the upper end of the small pump cylinder. The large plunger is connected to the lower end of the small plunger through the upper coupling of the upper end of the large plunger. The upper end of the small plunger is connected with the oil pumping rod through an oil outlet connector, and the lower coupling of the lower end of the large plunger is connected with the oil pumping rod through a liquid inlet connector. The oil outlet connector is provided with an oil outlet hole, and the liquid inlet connector is provided with a liquid inlet hole. The lower end of the tension pipe is provided with an oil leakage hole. The present application eliminates the difficulty of rod string downstroke caused by the eccentricity of the plunger, deepens the pump hanging, reduces the stroke loss of the well pipe and rod string, improves the liquid production of the oil well, reduces the energy consumption, and avoids pollution during operation.

[0005] The patent with publication number CN202971146U discloses an inserted sealing type deep pumping assisting device, which comprises a sealing sleeve, a tension pipe and a large pump cylinder connected in sequence, a small plunger and a large plunger connected together through a conversion joint in the pipe cavity formed by the above three, a sealing core pipe and a small pump cylinder connected together through a variable diameter joint on the outside of the small plunger from top to bottom. Two groups of sealing assemblies on the sealing core pipe comprise sealing rings, sleeve rings, spacer rings and sealing copper rings matched together from top to bottom. The upper end of the small plunger is connected with a sucker rod through a liquid outlet joint, and the lower end of the large plunger is connected with the sucker rod through a sucker rod joint. A liquid outlet hole is arranged on the liquid outlet joint, and a liquid inlet hole is arranged on the sucker rod joint. The sealing sleeve is connected with the tension pipe through a tension pipe joint, and the tension pipe is connected with the large pump cylinder through a large pump cylinder joint. A breathing hole is arranged on the large pump cylinder joint. The present application completely solves the problems of the prior art, such as the limited pumping depth and the necessity of a blowout preventer.

[0006] The outstanding defects of the prior art are that, in reducing the load of the suspension point, some problems have occurred. Because the load reducing device involved in the patent needs to be matched with a disengager in the application process, the disengager is also undergoing structural improvement for field application. Initially, the disengager adopts a lower docking and upper lifting type disengaging process, and the disadvantage of this process is that the disengager will automatically disengage from the load reducing device during use, and the reliability of the pipe string is problematic.

[0007] In order to overcome the disengagement problem of the disengager and the load reducing device during use, a load reducing pipe string that only disengages is designed, which overcomes the disengagement defect of the load reducing device and the disengager during use, but has the problem of not being applicable to a liner pipe string.

[0008] With the high water cut exploitation of oilfields, the corrosion and eccentric wear of oil pipes are serious, and many oil wells use liner pipes. Therefore, the use of the existing load reducing device is restricted. In order to overcome the above two defects, the disengager is improved by the designer and designed as a rotary disengager. This disengager is connected with the load reducing device through rotation. If the original load reducing device is still used, the pipe string will rotate during use, which is very difficult for the operator to operate and has serious safety hazards. Therefore, a rotation-preventing load reducing device suitable for liner pipes is urgently needed. SUMMARY

[0009] The purpose of the present application is to provide a new type of load reducing device suitable for deep pumping and lifting of a rod pump, especially a rotation-preventing load reducing device suitable for liner pipe oil wells.

[0010] The technical solution adopted by the present application is as follows.

[0011] A rotation-preventing load reducing device suitable for liner pipes, characterized by comprising an external structure and an internal structure.

[0012] The top end of the outer structure is provided with a tubing joint, and the top end of the inner structure is provided with an oil outlet joint; two upper anti-rotation structures are arranged on the radial outer circumferential surface of the oil outlet joint, and the two upper anti-rotation structures are symmetrical along the central axis of the inner hole of the oil outlet joint; two lower anti-rotation structures are arranged on the inner hole of the tubing joint, and the two lower anti-rotation structures are symmetrical along the central axis of the inner hole of the tubing joint; during operation, the oil outlet joint is lowered, and the upper anti-rotation structures on the oil outlet joint enter the lower anti-rotation structures of the tubing joint, thereby preventing the oil outlet joint from rotating relative to the tubing joint, so that the tubing does not rotate during disassembly of the pipe string, and the tubing is convenient to disassemble.

[0013] As a preferred technical solution, the inner diameter of the top end of the inner hole of the tubing joint is larger than the inner diameter of the remaining part of the inner hole of the tubing joint, thereby forming a stepped inner hole below the top end of the inner hole of the tubing joint; the upper anti-rotation structure is an arc-shaped long protrusion with an arc-shaped horizontal cross section arranged on the radial outer circumferential surface of the oil outlet joint at a certain height; the lower anti-rotation structure is an arc-shaped groove with an arc-shaped horizontal cross section arranged on the stepped inner hole of the tubing joint, and the opening of the arc-shaped groove is upward; when the oil outlet joint is lowered, each arc-shaped long protrusion on the oil outlet joint can enter the arc-shaped groove of the tubing joint, thereby preventing the oil outlet joint from rotating relative to the tubing joint.

[0014] As a preferred technical solution, the arc length of any horizontal cross section of each arc-shaped groove is greater than the arc length of each horizontal cross section of the arc-shaped long protrusion.

[0015] As a preferred technical solution, the left and right side surfaces of each arc-shaped long protrusion intersect with the radial outer circumferential surface of the oil outlet joint to form two curves, and the distance between the upper ends of the two curves is greater than the distance between the lower ends of the two curves.

[0016] As a preferred technical solution, the distance between the upper ends of the two curves is equal, and the distance between the lower ends of the two curves gradually decreases from top to bottom or decreases in sections.

[0017] As a preferred technical solution, the left and right side surfaces of each arc-shaped long protrusion intersect with the radial outer circumferential surface of the oil outlet joint to form two curves, and the bottom of the two curves intersects, thereby forming a downward sharp end at the bottom end of the arc-shaped long protrusion.

[0018] As a preferred technical solution, the horizontal cross section of the upper part of the separation part of the two adjacent arc-shaped grooves on the stepped inner hole gradually narrows from bottom to top at the left and right ends, thereby forming an upward sharp end; when the oil outlet joint is lowered, one side surface of the arc-shaped long protrusion is tangent to one side wall of the arc-shaped groove below, thereby facilitating the arc-shaped long protrusion to enter the arc-shaped groove below.

[0019] As a preferred technical solution, the diameter of the radial inner circumferential surface of the top end of each arc-shaped groove of the tubing joint is greater than the diameter of the radial inner circumferential surface of the bottom end.

[0020] As a preferred technical scheme, the diameter of the radially inner circumferential surface of each arc-shaped groove of the pipe joint gradually decreases from top to bottom or decreases in sections.

[0021] As a preferred technical scheme, the external structure comprises, from top to bottom, in sequence through threaded connection, the tubing joint, the tubing spool, the large pump cylinder joint, the large pump cylinder and the tubing lower joint with the inner hole central axis being on the same straight line.

[0022] The internal structure comprises, from top to bottom, in sequence through threaded connection, the oil outlet joint, the small plunger, the large plunger joint, the large plunger and the sucker rod joint with the inner hole central axis of the oil outlet joint being on the same straight line as the inner hole central axis of the tubing joint.

[0023] The radially outer circumferential surface of the small plunger is sleeved with the small pump cylinder; the radially outer circumferential surface of the small pump cylinder is not in contact with the tubing spool; the upper end of the small plunger is located in the inner hole of the lower end of the tubing joint, and the lower end of the small plunger is located in the inner hole of the large pump cylinder; the upper end of the large plunger joint is located in the inner hole of the large pump cylinder, and the lower end of the large plunger joint is located in the inner hole of the tubing lower joint; the large plunger is embedded on the radially outer circumferential surface of the middle part; and the radially outer circumferential surface of the large plunger is in contact with the radially inner circumferential surface of the large pump cylinder.

[0024] The upper end of the tubing spool is sleeved on the inner hole of the lower end of the tubing joint; the lower end of the tubing spool is sleeved on the inner hole of the top end of the large pump cylinder joint; the upper end of the large pump cylinder is sleeved on the inner hole of the bottom end of the large pump cylinder joint, and the lower end of the large pump cylinder is sleeved on the inner hole of the top end of the tubing lower joint.

[0025] The beneficial effects of the present application are that the anti-rotation structure design is respectively carried out at the oil outlet joint and the tubing joint, the upper anti-rotation structure is designed at the oil outlet joint, the lower anti-rotation structure is designed at the tubing joint, the upper anti-rotation structure and the lower anti-rotation structure are matched with each other in the use process, and the anti-rotation function of the pipe string is completed. In the normal oil pumping process, the upper anti-rotation mechanism and the lower anti-rotation mechanism do not contact, only in the operation process, the lower anti-rotation mechanism is contacted, the pipe string rotation is prevented, and the construction safety is ensured. By using the load reduction device, the deep pumping of low-permeability oil reservoirs can be successfully implemented, and the yield of oil wells is improved. By using the load reduction device, the use range is expanded, which can not only be applied to the load reduction deep pumping process of ordinary oil pipes, but also be applied to the load reduction deep pumping process of the inner lining oil pipe. By using the anti-rotation mechanism of the load reduction device, the pipe string rotation in the construction process is prevented, and the construction safety is greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a structure schematic view of the anti-rotation type load reduction device suitable for the inner lining oil pipe of the present application.

[0027] Figure 2 is a structure schematic view of A part of Figure 1 .

[0028] Figure 3 is a partial enlarged view of part D of Figure 2

[0029] Figure 4 is a partial enlarged view of part B of Figure 1

[0030] Figure 5 is a partial enlarged view of part C of Figure 1

[0031] Figure 6 is a perspective view of the oil outlet joint.

[0032] Figure 7 is a top view of Figure 6

[0033] Figure 8 is a perspective view of the oil pipe joint.

[0034] Figure 9 is a top view of Figure 8

[0035] Figure 10 is a schematic view of the oil outlet joint combined with the oil pipe joint.

[0036] Figure 11 is a sectional view along E-E' of Figure 10

[0037] Wherein: oil outlet joint-1, oil pipe joint-2, stepped inner hole-21, arc-shaped long convex strip-101, arc-shaped groove strip-201, separation part-202, small plunger-3, oil pipe short section-4, small pump cylinder-5, large pump cylinder joint-6, large pump cylinder-7, large plunger joint-8, large plunger-9, oil pipe lower joint-10, sucker rod joint-11. DETAILED DESCRIPTION

[0038] The invention will be further described below in conjunction with the drawings and examples.

[0039] Example 1. As shown in Figures 1-11 , a rotation-preventing load reduction device suitable for an inner lining oil pipe, characterized by: comprising an external structure and an internal structure.

[0040] ​​​​​​The outer structure top end is provided with a tubing joint 2, and the inner structure top end is provided with an oil outlet joint 1; the radial outer peripheral surface of the oil outlet joint 1 is provided with two upper anti-rotation structures, which are symmetrical along the central axis of the inner hole of the oil outlet joint 1; the inner hole of the tubing joint 2 is provided with two lower anti-rotation structures, which are symmetrical along the central axis of the inner hole of the tubing joint 2; during operation, the oil outlet joint 1 is lowered, and the upper anti-rotation structures on the oil outlet joint 1 enter the lower anti-rotation structures of the tubing joint 2, thereby preventing the oil outlet joint 1 from rotating relative to the tubing joint 2, so that the oil pipe does not rotate during disassembly of the pipe string, and the oil pipe is convenient to disassemble.

[0041] The inner hole of the top end of the tubing joint 2 has a larger diameter than the inner diameter of the rest of the inner hole of the tubing joint 2, thereby forming a stepped inner hole 21 below the top end of the inner hole of the tubing joint 2; the upper anti-rotation structure is an arc-shaped long protrusion 101 with an arc-shaped horizontal cross section arranged on the radial outer peripheral surface of the lower part of the oil outlet joint 1; the lower anti-rotation structure is an arc-shaped groove 201 with an arc-shaped horizontal cross section arranged on the stepped inner hole of the tubing joint 2, and the opening of the arc-shaped groove 201 is upward; when the oil outlet joint 1 is lowered, each arc-shaped long protrusion 101 on the oil outlet joint 1 can enter the arc-shaped groove 201 of the tubing joint 2, thereby preventing the oil outlet joint 1 from rotating relative to the tubing joint 2.

[0042] The arc length of any horizontal cross section of each arc-shaped groove 201 is greater than the arc length of each horizontal cross section of the arc-shaped long protrusion 101.

[0043] The left and right side surfaces of each arc-shaped long protrusion 101 intersect with the radial outer peripheral surface of the oil outlet joint 1 to form two curves, and the distance between the upper ends of the two curves is greater than the distance between the lower ends of the two curves.

[0044] The distance between the upper ends of the two curves is equal, and the distance between the lower ends of the two curves gradually decreases from top to bottom or decreases in segments.

[0045] The bottom of the two curves formed by the left and right side surfaces of the arc-shaped long protrusion 101 intersecting with the radial outer peripheral surface of the oil outlet joint 1 intersects, thereby forming a downward pointed end at the bottom end of the arc-shaped long protrusion 101.

[0046] The horizontal cross section of the upper part of the separation part 202 of the two adjacent arc-shaped grooves 201 on the stepped inner hole 21 gradually narrows from bottom to top at the left and right ends, thereby forming an upward pointed end; when the oil outlet joint 1 is lowered, one side surface of the arc-shaped long protrusion 101 is tangent to one side wall of the arc-shaped groove 201 below, thereby facilitating the arc-shaped long protrusion 101 to enter the arc-shaped groove 201 below.

[0047] The diameter of the radial inner peripheral surface of the top end of each arc-shaped groove 201 of the tubing joint 2 is greater than the diameter of the radial inner peripheral surface of the bottom end.

[0048] The diameter of the radially inner circumferential surface of each arc-shaped groove strip 201 of the pipe joint 2 gradually decreases from top to bottom or decreases in sections.

[0049] The external structure comprises, from top to bottom, the tubing joint 2, the tubing spool 4, the large pump cylinder joint 6, the large pump cylinder 7 and the tubing lower joint 10 which are sequentially connected by threads.

[0050] The internal structure comprises, from top to bottom, the oil outlet joint 1, the small plunger 3, the large plunger joint 8, the large plunger 9 and the sucker rod joint 11 which are sequentially connected by threads.

[0051] The radially outer circumferential surface of the small plunger 3 is sleeved with the small pump cylinder 5; the radially outer circumferential surface of the small pump cylinder 5 does not contact the tubing spool 4; the upper end of the small plunger 3 is located in the inner hole of the lower end of the tubing joint 2, and the lower end of the small plunger 3 is located in the inner hole of the large pump cylinder 7; the upper end of the large plunger joint 8 is located in the inner hole of the large pump cylinder 7, and the lower end of the large plunger joint 8 is located in the inner hole of the tubing lower joint 10; the large plunger 9 is embedded on the radially outer circumferential surface of the middle part; and the radially outer circumferential surface of the large plunger 9 contacts the radially inner circumferential surface of the large pump cylinder 7.

[0052] The upper end of the tubing spool 4 is sleeved on the inner hole of the lower end of the tubing joint 2; the lower end of the tubing spool 4 is sleeved on the inner hole of the top end of the large pump cylinder joint 6; the upper end of the large pump cylinder 7 is sleeved on the inner hole of the bottom end of the large pump cylinder joint 6, and the lower end of the large pump cylinder 7 is sleeved on the inner hole of the top end of the tubing lower joint 10.

[0053] In use, the deep pumping and load-reducing pipe column is segmented and lowered, and the pump depth is 2500m, and the load-reducing device is designed as 1200m for example. First, the oil pump and the pipe column above 1300m are lowered into the well, and then the 1300m sucker rod is lowered, at which time the sucker rod joint 11 and the tubing lower joint 10 of the load-reducing device are respectively connected with the lowered sucker rod and the tubing. The lower part of the disengager is connected with the oil outlet joint 1, and the remaining 1200m tubing and the remaining 1200m sucker rod are lowered, and the bottom of the sucker rod is provided with the upper part of the disengager. After being lowered to the position, the disengager is rotated and connected. In use, the upper part of the anti-rotation mechanism and the lower part of the anti-rotation mechanism do not contact. Only when the operation is performed, the protrusion of the upper anti-rotation mechanism is lowered into the concave structure, and the concave structure can prevent the pipe column from rotating, thereby ensuring the safety of construction.

[0054] The anti-rotation structure is designed at the outlet joint and the tubing joint, respectively, wherein the upper anti-rotation structure is designed at the outlet joint, the lower anti-rotation structure is designed at the tubing joint, the upper anti-rotation structure and the lower anti-rotation structure are matched with each other to complete the anti-rotation function of the pipe column during the use. The upper anti-rotation structure and the lower anti-rotation structure are not contacted during the normal oil pumping process, and are contacted only during the operation to prevent the pipe column from rotating and ensure the safety of the construction. The load reducing device can be used to successfully implement the deep pumping of the low-permeability oil reservoir and improve the yield of the oil well. The load reducing device can be used to expand the application range and can be applied to the load reducing and deep pumping process of the ordinary tubing and the load reducing and deep pumping process of the inner lining tubing. The anti-rotation structure of the load reducing device can prevent the pipe column from rotating during the construction process, and the safety of the construction is greatly improved.

[0055] In the embodiment 2, the outer side surface of the two arc-shaped long protrusions 101 intersects with the plane through the central axis to form two curves, the upper ends of the two curves are spaced apart by an equal line, and the lower ends of the two curves are spaced apart by a line which is gradually or sectionally reduced from top to bottom. The diameter of the radial inner circumferential surface of each arc-shaped groove strip 201 of the pipe joint 2 is gradually or sectionally reduced from top to bottom.

[0056] The above-mentioned embodiments are only used for understanding the present application, and are not intended to limit the technical solutions described in the present application. Based on the technical solutions described in the claims, those skilled in the art can make various changes or modifications. All equivalent changes or modifications should be covered in the protection scope of the present application. The details not described in the present application are the known technology of those skilled in the art.

Claims

1. A type of anti-rotation unloading device suitable for lined oil pipes, characterized in that: The outer structure and the inner structure are included; The outer structure top end is provided with a tubing joint (2), and the inner structure top end is provided with an oil outlet joint (1); the radial outer peripheral surface of the oil outlet joint (1) is provided with two upper anti-rotation structures, and the two upper anti-rotation structures are symmetrical along the central axis of the inner hole of the oil outlet joint (1); the inner hole of the tubing joint (2) is provided with two lower anti-rotation structures, and the two lower anti-rotation structures are symmetrical along the central axis of the inner hole of the tubing joint (2); during operation, the upper anti-rotation structures on the oil outlet joint (1) are made to enter the lower anti-rotation structures of the tubing joint (2) by lowering the oil outlet joint (1), so that the oil outlet joint (1) is prevented from rotating relative to the tubing joint (2), thereby ensuring that the tubing does not rotate during disassembly of the pipe string, and facilitating disassembly of the tubing. The hole diameter of the top end of the inner hole of the tubing joint (2) is greater than the inner diameter of the remaining part of the inner hole of the tubing joint (2), thereby forming a stepped inner hole (21) below the top end of the inner hole of the tubing joint (2); the upper anti-rotation structure is an arc-shaped long protrusion (101) with an arc-shaped horizontal cross section arranged on the radial outer peripheral surface of the lower part of the oil outlet joint (1); the lower anti-rotation structure is an arc-shaped groove strip (201) with an arc-shaped horizontal cross section arranged on the stepped inner hole of the tubing joint (2), and the opening of the arc-shaped groove strip (201) faces upwards; when the oil outlet joint (1) is lowered, each arc-shaped long protrusion (101) on the oil outlet joint (1) can enter the arc-shaped groove strip (201) of the tubing joint (2), thereby preventing the oil outlet joint (1) from rotating relative to the tubing joint (2). The arc length of any horizontal cross section of each arc-shaped groove strip (201) is greater than the arc length of each horizontal cross section of the arc-shaped long protrusion (101). The left and right side surfaces of each arc-shaped long protrusion (101) intersect with the radial outer peripheral surface of the oil outlet joint (1) to form two curves, and the distance between the upper ends of the two curves is greater than the distance between the lower ends of the two curves. The distance between the upper ends of the two curves is equal, and the distance between the lower ends of the two curves gradually decreases from top to bottom or decreases in sections. The bottom parts of the two curves intersect, thereby forming a downward sharp point at the bottom end of the arc-shaped long protrusion (101). The width of the left and right ends of the horizontal cross section of the separation part (202) of the two adjacent arc-shaped groove strips (201) on the stepped inner hole (21) gradually decreases from bottom to top, thereby forming an upward sharp point; when the oil outlet joint (1) is lowered, one side surface of the arc-shaped long protrusion (101) is tangent to one side wall of the arc-shaped groove strip (201) below the arc-shaped long protrusion (101), thereby facilitating the arc-shaped long protrusion (101) to enter the arc-shaped groove strip (201) below the arc-shaped long protrusion (101).

2. A swivel preventing load reducing device for use in a lined tubing as defined in claim 1, characterized in that: The diameter of the radial inner peripheral surface of the top end of each arc-shaped groove strip (201) of the tubing joint (2) is greater than the diameter of the radial inner peripheral surface of the bottom end of each arc-shaped groove strip (201) of the tubing joint (2).

3. A swivel preventing load reducing device for use in a lined pipe as claimed in claim 2, characterised in that: The diameter of the radial inner peripheral surface of each arc-shaped groove strip (201) of the tubing joint (2) gradually decreases from top to bottom or decreases in sections.

4. A swivel preventing load reducing device for use in a lined tubing as defined in claim 1, characterized in that: The outer structure includes, from top to bottom, the tubing joint (2), the tubing short joint (4), the large pump cylinder joint (6), the large pump cylinder (7), and the tubing lower joint (10) which are sequentially connected by threads and have the same central axis of the inner hole. The internal structure comprises, from top to bottom, an oil outlet joint (1) with the inner hole central axis of the oil outlet joint (1) and the inner hole central axis of the tubing joint (2) in the same straight line, a small plunger (3), a large plunger joint (8), a large plunger (9), and a sucker rod joint (11) connected by threads in sequence; The radial outer peripheral surface of the small plunger (3) is sleeved with a small pump cylinder (5); the radial outer peripheral surface of the small pump cylinder (5) is not in contact with the tubing short joint (4); the upper end of the small plunger (3) is located in the inner hole of the lower end of the tubing joint (2), and the lower end of the small plunger (3) is located in the inner hole of the large pump cylinder (7); the upper end of the large plunger joint (8) is located in the inner hole of the large pump cylinder (7), and the lower end of the large plunger joint (8) is located in the inner hole of the tubing lower joint (10); the large plunger (9) is embedded on the radial outer peripheral surface of the middle part; the radial outer peripheral surface of the large plunger (9) is in contact with the radial inner peripheral surface of the large pump cylinder (7); The upper end of the tubing short joint (4) is sleeved on the inner hole of the lower end of the tubing joint (2); the lower end of the tubing short joint (4) is sleeved on the inner hole of the top end of the large pump cylinder joint (6); the upper end of the large pump cylinder (7) is sleeved on the inner hole of the bottom end of the large pump cylinder joint (6), and the lower end of the large pump cylinder (7) is sleeved on the inner hole of the top end of the tubing lower joint (10).

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