A sucker rod string load reducing device
By designing a sucker rod string unloading device, the problems of oil draining and construction safety in production tubing in deep, low-permeability reservoirs were solved, achieving efficient and safe sucker rod string operation and meeting the exploitation needs of deep, low-permeability reservoirs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2025-07-16
- Publication Date
- 2026-07-21
AI Technical Summary
Existing unloading devices have the problem of production tubing not being able to drain oil in deep, low-permeability reservoirs, and there are construction safety hazards after the sucker rod string is exposed above the wellhead blowout preventer.
A sucker rod string unloading device was designed, comprising a small plunger and a large plunger, as well as a small pump barrel and a large pump barrel. It is equipped with an oil drainer, a breather hole, and a sand scraper ring. The oil drainer achieves oil drainage from the upper production string through an impact-type oil drainer, and the multi-section small plunger structure prevents jamming. Combined with the sand scraper ring, it prevents sand particles from entering and ensures safe production.
It has enabled efficient exploitation of deep, low-permeability oil reservoirs, reduced construction safety risks and labor intensity, improved work efficiency, and met the exploitation needs of deep, low-permeability oil reservoirs.
Smart Images
Figure CN224532945U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to a load reduction device for oil well pumps in the petroleum industry, and in particular to a sucker rod string load reduction device. Background Technology
[0002] In low-permeability sections of oilfields, pumping unit wells have become the dominant lifting method for low-permeability reservoirs. The rated load of pumping units is mainly 12t and 10t, while the pumps are primarily 44mm and 38mm. Statistical analysis of low-permeability pumping wells shows that the average pumping depth of a 38mm pump in the well is 2069m, while the average pumping depth of a 44mm pump is 1886m, with an average daily fluid production of only 8.2m³. 3 / d, the average working efficiency of the pumping system is only 18.39%.
[0003] With the continuous development of oil fields, major domestic oil fields have increased their efforts in developing shale oil and tight oil reservoirs. These reservoirs are characterized by deep oil layer burial (above 3500m) and high gas-oil ratio (not less than 50m). 3 The deep, low-permeability oil reservoirs exhibit complex geological characteristics, including high temperatures (above 100℃) and low permeability. Because the average dynamic fluid level in these reservoirs exceeds 2000m, water wells cannot effectively replenish energy. To ensure effective production and coordinate well supply and drainage, it is necessary to deepen the pump string for small-pump deep pumping to improve production rate and recovery. However, conventional rod-pump deep pumping with small pumps presents challenges due to the deep burial depth and high gas-oil ratio. Using a sucker rod string deloading device can effectively reduce load while fully utilizing existing lifting equipment, thus unlocking the well's potential.
[0004] To this end, the on-site technicians did a lot of work and the following patented technologies emerged.
[0005] Patent application CN202222787639.1 discloses a rod pump unloading oil extraction device, wherein the pump diameter of the upper pump barrel is smaller than that of the lower pump barrel. The upper pump barrel, the flow divider, and the lower pump barrel are connected in sequence. The upper plunger is connected to the lower plunger. The flow divider has a lateral connecting hole, which communicates with the lower part of the upper pump barrel and the upper part of the lower pump barrel. The upper part of the upper plunger is connected to the upper hollow rod connector, and the lower part of the lower plunger is connected to the lower hollow rod connector. An oil outlet is provided on the side wall of the flow divider. The lower part of the upper oil pipe is connected to the upper part of the diverter, with the connection point located above the lateral connecting hole. An upper oil outlet channel is formed between the upper oil pipe and the upper pump barrel, and the lower end of the upper oil outlet channel communicates with the oil outlet channel. The upper part of the lower oil pipe is connected to the middle thread of the diverter, with the connection point located below the lateral connecting hole and above the lower end of the oil outlet channel. A lower oil outlet channel is formed between the lower oil pipe and the lower pump barrel, and the upper end of the lower oil outlet channel communicates with the oil outlet channel.
[0006] Patent application CN202020162012.5 discloses a load-reducing rod pump, comprising a support assembly, a plunger assembly, a pump barrel assembly, and a ball valve assembly. The support assembly is connected to the pump barrel assembly, the plunger assembly is disposed within the pump barrel assembly, and the ball valve assembly is disposed within the pump barrel assembly and the plunger assembly at an end away from the support assembly. The plunger assembly includes a first plunger and a second plunger connected to each other. The first plunger is close to the support assembly and connected to a valve stem. The diameter of the second plunger is larger than that of the first plunger, and the connection between the second plunger and the first plunger forms an annular stepped surface. A breather hole is provided on the pump barrel assembly near the first plunger. The ball valve assembly includes an inlet valve and an outlet valve, the inlet valve being located within the pump barrel assembly, and the outlet valve being located within the plunger assembly. The load-reducing rod pump of the above-mentioned utility model can reduce the suspension point load and lift energy consumption in rod pump wells.
[0007] Patent application CN201420592144.6 discloses a double-layer unloaded deep well pumping pump, comprising an outer cylinder, within which an upper pump cylinder and a lower pump cylinder are installed and connected to each other. A breather hole, penetrating the outer wall of the outer cylinder and communicating with the outside, is provided at the connection between the upper and lower pump cylinders. A hollow lower plunger is provided in the lower pump cylinder, and an upper plunger with a smaller outer diameter and communicating with the lower plunger is connected to its upper end. An upstream moving valve is provided at the upper end of the upper plunger, and a downstream moving valve is provided at the lower end of the lower plunger. The pump also includes a fixed valve installed at the end of the lower pump cylinder. Compared with ordinary tubular pumps, this utility model can achieve a greater pumping depth while maintaining the same pump displacement, allowing tubular pumps with the same working pump diameter to have a greater limit pumping depth. Similarly, without changing the surface equipment's load-bearing capacity, it can complete pumping work with a larger displacement under the same pump setup conditions, or pumping work with a greater pumping depth under the same displacement conditions.
[0008] The above-mentioned patented technologies, when using existing ground lifting equipment, can achieve a greater insertion depth compared to ordinary tubing without a load shedding device, while maintaining the same pump discharge rate, thus meeting the development needs of deep, low-permeability oil reservoirs.
[0009] However, the aforementioned patented technologies also have the following problems: The unloading device is generally deployed at a depth of about 1000m, and there is a problem that the production tubing above the unloading device cannot drain oil; furthermore, the small plunger in the unloading device can be up to 9m long, and when the sucker rod string is stuck, it can only move upwards. This causes the length of the sucker rod string protruding from the wellhead blowout preventer to exceed the height of the workover rig. At this point, the small plunger must be cut off, posing a safety hazard during construction. Summary of the Invention
[0010] The purpose of this invention is to provide a sucker rod string unloading device that, while making full use of existing surface lifting equipment, increases the insertion depth of the sucker pump, solving the problems of oil leakage from the production tubing above the unloading device and construction safety issues after the sucker rod string is exposed above the wellhead blowout preventer. This meets the needs of deep, low-permeability oil reservoir development, improves the recovery rate of low-permeability reservoirs, ensures safe production, and reduces the labor intensity of construction personnel.
[0011] The technical solution of this utility model is: a sucker rod string unloading device, including a small plunger and a large plunger, as well as a small pump barrel and a large pump barrel installed in the housing, wherein: an oil drainer is connected in the upper body of the housing and a breather is provided in the lower body; the upper section of the small plunger, which is composed of two or more sections connected together, is provided with an upper liquid passage hole; the upper end of the large plunger is connected to the small plunger and the upper sucker rod from bottom to top, and the lower end is connected to the reducing joint with a lower liquid passage hole and the lower sucker rod from top to bottom; The small and large plungers can reciprocate up and down within the small and large pump barrels installed in the housing.
[0012] Preferably, the drain valve is an impact-type drain valve and is threadedly connected to the housing above the bottom dead center of the small plunger; a centralizer is fixed in the upper sucker rod, which is made of nylon material and is heat-fused to the upper sucker rod at the position above the drain valve in the housing as it descends.
[0013] Preferably, the two or more small plungers are connected by threads; the upper end of the small plunger is threaded to the upper sucker rod through a sucker rod coupling and the upper fluid passage is set in the sucker rod coupling; the upper fluid passage is set in one or more.
[0014] Preferably, the inner circle of the outer shell is a non-uniform diameter inner circle and a sealing step is provided in the middle. A sealing cylinder is suspended on the sealing step, and the small pump cylinder is threadedly connected to the sealing cylinder; the large pump cylinder is threadedly connected in the lower inner circle of the outer shell.
[0015] Preferably, the sealing cylinder has a T-shaped cylindrical structure with an inner circle larger than the outer circle of the sucker rod coupling. The upper outer circle of the sealing cylinder is pressed against the sealing step of the outer shell, and the lower outer circle of the sealing cylinder is interference-fitted with the sealing step.
[0016] Preferably, the breather holes are radially arranged in the housing of the outer shell, and there is more than one breather hole; the position of the breather hole corresponds to the annulus formed by the sealing step, sealing cylinder, small pump cylinder, small plunger and large plunger in the outer shell; when the unloading device is lowered into the well, the breather hole contacts the upper end of the dynamic fluid surface in the well.
[0017] Preferably, a scraping ring is embedded in the upper part of the large plunger or the large pump barrel, on the outer circle of the large plunger or on the inner circle of the large pump barrel; the outer circle of the scraping ring embedded in the outer circle of the large plunger is interference-fitted with the inner circle of the large pump barrel; the inner circle of the scraping ring embedded in the inner circle of the large pump barrel is interference-fitted with the outer circle of the large plunger; the scraping ring is made of plastic material.
[0018] Preferably, a limiting step is threadedly connected to the bottom inner circle of the housing and below the large pump barrel, and the inner diameter of the limiting step is smaller than the outer diameter of the large plunger.
[0019] Preferably, the sealing step in the sealing cylinder and the outer shell forms a sand settling chamber in the upper part of the inner cavity of the outer shell.
[0020] Preferably, the diameter of the small plunger is set between 38mm and 44mm, and the diameter of the large plunger is set between 70mm and 83mm.
[0021] Compared with the prior art, the significant effects of this utility model are as follows: 1. An oil drainer is connected and installed in this unloading device. The oil drainer is an impact type oil drainer, which is convenient to construct and operate. It can conveniently drain the oil in the production tubing above this utility model during well workover operations.
[0022] 2. The small plunger in this invention is composed of two or more connected sections, with the upper fluid passage located in the sucker rod coupling connected to the upper section of the small plunger. In the event of jamming of the small or large plunger, even if the sucker rod string is jammed and rises above the wellhead blowout preventer, it is not necessary to cut off the small plunger. Simply disassemble the connected small plungers at an appropriate location. This facilitates construction operations, reduces the labor intensity of workers, improves work efficiency, and reduces construction safety risks.
[0023] 3. This unloading device is equipped with a sand settling chamber and a sand scraping ring. A small amount of sand particles flowing into the production tubing above through the upper fluid passage can settle in the sand settling chamber. The sand scraping ring can prevent sand particles entering through the breather hole from entering the large pump barrel, preventing the large plunger from getting stuck and causing the sucker rod to surge up to the wellhead, thus ensuring safe production, ensuring the personal safety of on-site employees, and reducing the labor intensity of employees and production costs.
[0024] 4. To ensure the sucker rod string connected to this invention is more centered in the wellbore and to prevent the drawbacks caused by uneven wear on the outer casing, a centralizer is connected to the upper sucker rod as it descends to the position above the bleeder inside the outer casing. This does not obstruct the use of the bleeder and also provides centralization for the sucker rod string.
[0025] 5. When the pumping unit is running, because the breather in this device is connected to the downhole dynamic fluid surface, it remains within the annulus formed by the small plunger, small pump barrel, and large plunger during the reciprocating motion of the sucker rod string. This provides greater load shearing force, allowing the pumping unit to reach greater depths. Using a standard 12-type beam pumping unit, a Φ44mm pump can be lowered to depths below 2500m, and a Φ38mm pump to depths below 3000m, fully meeting the needs of deep, low-permeability reservoir development. Furthermore, it significantly reduces the risk of sand jamming the sucker rod string, achieving safe and environmentally friendly operations.
[0026] In summary, this utility model has significant practical effects and can generate good economic benefits, and has a promising application prospect. Attached Figure Description
[0027] The accompanying drawings are provided to further illustrate the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the structure of this utility model.
[0028] In the diagram: 1. Upper sucker rod; 2. Centralizer; 3. Oil drainer; 4. Outer casing; 5. Upper fluid passage; 6. Sand settling chamber; 7. Sealing cylinder; 8. Small plunger; 9. Small pump barrel; 10. Breather hole; 11. Sand scraper ring; 12. Large plunger; 13. Large pump barrel; 14. Lower fluid passage; 15. Limiting step; 16. Reducing connector; 17. Lower sucker rod. Detailed Implementation
[0029] The accompanying drawings are for reference and illustration only and are not intended to limit the scope of protection of this utility model. The technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the scope of protection of this utility model.
[0030] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.
[0031] In the description of this utility model, it should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, in the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.
[0032] See Figure 1 A sucker rod string unloading device includes a small plunger 8 and a large plunger 12, as well as a small pump barrel 9 and a large pump barrel 13, installed in a housing 4. The upper body of the housing 4 is connected to an oil drainer 3, and the lower body has a breather 10. The upper section of the small plunger 8, composed of two or more connected sections, has an upper fluid passage 5. The upper end of the large plunger 12 is connected from bottom to top to the small plunger 8 and the upper sucker rod 1, and the lower end is connected from top to bottom to a reducing joint 16 with a lower fluid passage 14 and the lower sucker rod 17. The small plunger 8 and the large plunger 12 can reciprocate up and down within the small pump barrel 9 and the large pump barrel 13 installed in the housing 4. The produced fluid from the oil well enters the large plunger 12 and the small plunger 8 through the lower fluid passage 14, flows through the upper fluid passage 5 into the upper production string, and is discharged to the surface.
[0033] To address the issues of oil drainage from the production tubing above the current unloading device and construction safety after the sucker rod string protrudes from the wellhead blowout preventer, this invention incorporates an oil drainer 3 connected to the upper body of the outer casing 4. During well workover, when the upper sucker rod 1 above the unloading device is pulled out of the production tubing, the oil drainer 3 can be opened to drain oil from the production tubing above the device. This solves the problem that existing unloading devices cannot drain oil from the upper production tubing, facilitating well workover operations and construction.
[0034] Meanwhile, to address the issue of having to cut off the small plunger if the unloading device gets stuck downhole or surges above the blowout preventer at the wellhead, the small plunger 8 in this invention is composed of two or more connected sections. Thus, if such a situation occurs, the small plunger 8 can be directly removed from its appropriate location. This avoids safety risks during construction, reduces the labor intensity of workers, and improves work efficiency.
[0035] After using this invention, the oil well fluid enters through the lower fluid passage 14 and flows out through the upper fluid passage 15 to be pumped to the surface. This unloading device has a simple structure, which can drain oil and avoids the defect of sawing off the small plunger at the wellhead.
[0036] Based on the above embodiment one, the present invention also has the following embodiments: In a preferred embodiment: the drain valve 3 is an impact-type drain valve and is threadedly connected to the housing 4 above the bottom dead center of the small plunger 8; a centralizer 2 is fixed in the upper sucker rod 1. The centralizer 2 is made of nylon material and is heat-fused to the upper sucker rod 1 at the position above the drain valve 3 in the housing 4 as it descends. The centralizer 2 is existing technology and has various structures and shapes, any of which can be installed on the outside of the upper sucker rod 1. This further ensures the centering of the sucker rod, reduces the failure rate of the sucker rod string, further improves the service life of the sucker rod, and reduces production costs.
[0037] In a preferred embodiment: the two or more small plungers 8 are connected by threads, so that if the sucker rod string moves to the wellhead, it can be easily disassembled, and the threaded small plungers 8 are easier to disassemble; the upper end of the small plunger 8 is threaded to the upper sucker rod 1 through a sucker rod coupling and the upper fluid passage 5 is set in the sucker rod coupling; the upper fluid passage 5 is set in one or more.
[0038] In a preferred embodiment: the inner circle of the outer shell 4 is a non-uniform diameter inner circle and a sealing step is provided in the middle. A sealing cylinder 7 is suspended on the sealing step, and the small pump cylinder 9 is threadedly connected to the sealing cylinder 7; the large pump cylinder 13 is threadedly connected to the lower inner circle of the outer shell 4.
[0039] In a preferred embodiment, the sealing cylinder 7 has a T-shaped cylindrical structure with an inner circle larger than the outer circle of the sucker rod coupling. The upper outer circle of the sealing cylinder 7 is pressed against the sealing step of the outer shell 4, and the lower outer circle of the sealing cylinder 7 is interference-fitted with the sealing step.
[0040] In a preferred embodiment: the breather holes 10 are radially arranged in the housing of the outer shell 4 and there are more than one such hole; the position of the breather holes 10 corresponds to the annulus formed by the sealing step, sealing cylinder 7, small pump cylinder 9, small plunger 8 and large plunger 12 in the outer shell 4; when the unloading device is lowered into the well, the breather holes 10 come into contact with the upper end of the dynamic fluid surface in the well, making the pumping of the sucker rod string smoother and increasing the unloading capacity.
[0041] When the pumping unit is running, because the breather 10 in this device is connected to the downhole dynamic fluid surface, during the reciprocating motion of the sucker rod string, the breather 10 is always within the annulus formed by the small plunger 8, the small pump barrel 9, and the large plunger 12. This provides greater load shearing force to the device, allowing the pumping unit to reach a greater depth. Under the condition of using a conventional Type 12 beam pumping unit, a Φ44mm pumping unit can be lowered to a depth of over 2500m, and a Φ38mm pumping unit can be lowered to a depth of over 3000m.
[0042] In a preferred embodiment: a scraping ring 11 is embedded in the upper part of the large plunger 12 or the large pump barrel 13, on the outer circle of the large plunger 12 or the inner circle of the large pump barrel 13; the outer circle of the scraping ring 11 embedded in the outer circle of the large plunger 12 is interference-fitted with the inner circle of the large pump barrel 13; the inner circle of the scraping ring 11 embedded in the inner circle of the large pump barrel 13 is interference-fitted with the outer circle of the large plunger 12; the scraping ring 11 is made of plastic material. Figure 1 The scraper ring 11 shown is embedded in the inner circle of the large pump cylinder 13.
[0043] In a preferred embodiment, a limiting step 15 is threadedly connected to the bottom inner circle of the outer casing 4 and below the large pump barrel 13. The inner diameter of the limiting step 15 is smaller than the outer diameter of the large plunger 12. The limiting step 15 prevents the large plunger 12 from falling out of the large pump barrel 13 during operation.
[0044] In a preferred embodiment, the sealing steps in the sealing cylinder 7 and the outer shell 4 form a sand settling chamber 6 in the upper part of the inner cavity of the outer shell 4. When the well is shut down, the sand particles carried in the produced fluid can be deposited in the sand settling chamber 6, preventing the sand particles from entering between the small plunger 8 and the small pump cylinder 9, jamming the small plunger 8, or even causing the sucker rod string to surge up above the blowout preventer at the wellhead after the well is opened.
[0045] In a preferred embodiment, the diameter of the small plunger 8 is set between 38mm and 44mm, and the diameter of the large plunger 12 is set between 70mm and 83mm.
[0046] The embodiments described above are merely typical examples, but the present invention is not limited to these embodiments. Those skilled in the art can make modifications without departing from the spirit and teachings of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the inventive spirit and concept of the present invention should be included within the protection scope of the present invention. Therefore, the protection scope is not limited to the above description.
Claims
1. A sucker rod string unloading device, comprising a small plunger and a large plunger, as well as a small pump barrel and a large pump barrel, installed in a housing, characterized in that: The upper body of the housing is connected to an oil drain device, and the lower body is provided with a breather hole; the upper section of the small plunger, which is composed of two or more sections, is provided with an upper fluid passage hole; the upper end of the large plunger is connected to the small plunger and the upper sucker rod from bottom to top, and the lower end is connected to the reducing joint with a lower fluid passage hole and the lower sucker rod from top to bottom; the small plunger and the large plunger can reciprocate up and down in the small pump barrel and the large pump barrel installed in the housing.
2. The sucker rod string unloading device as described in claim 1, characterized in that, The drain device is an impact-type drain device and is threadedly connected to the housing above the bottom dead center of the small plunger; a centralizer is fixed in the upper sucker rod, which is made of nylon material and is heat-fused to the upper sucker rod at the position above the drain device in the housing as it descends.
3. The sucker rod string unloading device as described in claim 2, characterized in that, The two or more small plungers are connected by threads; the upper end of the small plunger is threaded to the upper sucker rod through a sucker rod coupling and the upper fluid passage is set in the sucker rod coupling; the upper fluid passage is set in one or more.
4. The sucker rod string unloading device as described in claim 2, characterized in that, The inner circle of the outer shell is a non-uniform diameter inner circle and has a sealing step in the middle. A sealing cylinder is suspended on the sealing step, and the small pump cylinder is threadedly connected to the sealing cylinder. The large pump cylinder is threadedly connected to the lower inner circle of the outer shell.
5. The sucker rod string unloading device as described in claim 4, characterized in that, The sealing cylinder has a T-shaped cylindrical structure with an inner circle larger than the outer circle of the sucker rod coupling. The upper outer circle of the sealing cylinder is pressed against the sealing step of the outer shell, and the outer circle of the lower cylinder is interference-fitted with the sealing step.
6. The sucker rod string unloading device as described in claim 5, characterized in that, The breather holes are radially arranged in the shell of the outer casing, and there is more than one breather hole. The position of the breather hole corresponds to the annulus formed by the sealing step, sealing cylinder, small pump cylinder, small plunger and large plunger in the outer casing. When the unloading device is lowered into the well, the breather hole contacts the upper end of the dynamic fluid surface in the well.
7. A sucker rod string unloading device as described in claim 4, characterized in that, in The upper part of the large plunger or large pump barrel has a scraping ring embedded in the outer circle of the large plunger or the inner circle of the large pump barrel; the outer circle of the scraping ring embedded in the outer circle of the large plunger is interference-fitted with the inner circle of the large pump barrel; the inner circle of the scraping ring embedded in the inner circle of the large pump barrel is interference-fitted with the outer circle of the large plunger; the scraping ring is made of plastic material.
8. The sucker rod string unloading device as described in claim 7, characterized in that, A limiting step is threadedly connected to the bottom inner circle of the housing and below the large pump barrel. The inner diameter of the limiting step is smaller than the outer diameter of the large plunger.
9. A sucker rod string unloading device as described in claim 5, characterized in that, The sealing steps in the sealing cylinder and the outer shell form a sand settling chamber in the upper part of the inner cavity of the outer shell.
10. A sucker rod string unloading device as described in claim 7, characterized in that, The diameter of the small plunger is set between 38mm and 44mm, and the diameter of the large plunger is set between 70mm and 83mm.