Pressure buffering device for well cementation rubber plug

Abstract

The invention belongs to the field of petroleum and natural gas exploration and development, and particularly relates to a pressure buffering device for a well cementation rubber plug. The device comprises a body, a protection cylinder and an action part. The body is of a hollow cylindrical structure, and a first drainage hole and a connecting section capable of being connected with a rubber plug are arranged on the body. The protection cylinder is arranged on the outer side of the body in a sleeving mode, and a third drainage hole is formed in the protection cylinder. The action part is arranged between the body and the protective cylinder and comprises a piston and a spring arranged below the piston, and a second drainage hole is formed in the piston. And the piston is constructed to be capable of compressing the spring and moving upwards in response to abnormal well cementation pressure, so that the first drainage hole, the second drainage hole and the third drainage hole are communicated to perform pressure relief operation. The device can reduce the damage of the rubber plug caused by overlarge pressure fluctuation in the well cementation effect to a great extent, and has a good application prospect in the field.

Description

Technical Field

[0001] The invention belongs to the field of oil and gas exploration and development, and in particular relates to a pressure buffer device for a cementing plug. Background Art

[0002] With the development of oil exploration technology, wells are deeper and hotter, and the pressure during cementing construction is gradually increasing. As an important tool for replacing slurry during cementing, the importance of rubber plugs in cementing construction cannot be ignored. As the pressure of cementing construction continues to increase, when the pressure in the tubing fluctuates, it is very easy to damage the rubber plug system, affect the cementing quality, and then affect the oil and gas production. At present, the conventional rubber plug system connects the rubber plug to other cementing tools through threads, and is sealed by a rubber bowl. There is no pressure buffer mechanism, and the ability to cope with pressure fluctuations in the tubing is weak. Summary of the invention

[0003] In order to solve the problem in the prior art that the rubber plug is easily damaged due to pressure fluctuation in the pipe string during the cementing process, the present invention provides a pressure buffer device for the cementing rubber plug.

[0004] The pressure buffer device for cementing plug comprises:

[0005] The body is constructed as a hollow cylindrical structure, and is provided with a first leakage hole and a connecting section capable of being connected to a rubber plug;

[0006] A protective tube, which is constructed as a hollow cylindrical structure, is sleeved on the outer side of the body, and includes a third leakage hole opened on the protective tube; and

[0007] The action part is arranged between the body and the protection tube, and comprises a piston and a spring arranged above the piston, and a second leakage hole is opened on the piston.

[0008] The piston is configured to compress the spring and move upward in response to abnormal cementing pressure, so that the first leakage hole, the second leakage hole and the third leakage hole are connected to perform pressure relief operations.

[0009] As an extension of the above technical solution, the present invention also provides the following embodiments:

[0010] The main body includes a working section, a bearing section and a tail section which are sequentially connected and arranged in order from bottom to top and whose outer diameters increase sequentially, the protective tube abuts against the lower end surface of the tail section, the action part is arranged inside an action chamber between the protective tube and the working section, and the spring is connected to the lower end surface of the bearing section.

[0011] An auxiliary hole is provided on the main body and penetrates through the side wall of the main body so as to connect the middle cavity of the main body with the action chamber.

[0012] The connecting section is disposed below the working section, and the connecting section is configured to have an outer diameter smaller than that of the working section.

[0013] An annular groove is provided on the inner wall of the protection tube, and the third leakage holes are configured to be communicated with the annular groove.

[0014] The sum of the flow areas of all the third leakage holes, the sum of the flow areas of all the first leakage holes, and the sum of the flow areas of all the second leakage holes are all constructed to be no less than the flow area of ​​the body.

[0015] It includes sealing components arranged between the piston and the body, between the piston and the protection tube, and between the protection tube and the body.

[0016] The sealing assembly includes a special-shaped ring assembly and a first sealing ring which are arranged between the body and the piston and are respectively located below and above the first leakage hole. The special-shaped ring assembly includes a special-shaped ring and two retaining rings located on the upper and lower sides of the special-shaped ring.

[0017] The special-shaped ring assembly is constructed so as to remain within the sealing stroke of the special-shaped ring assembly when the second leakage hole performs the pressure relief operation.

[0018] The piston structure is a surface treated with micro-texture.

[0019] The advantages of the present invention compared to the prior art are:

[0020] Through the combined use of the main body, the protective tube and the action part, the automatic pressure relief function is realized when the pressure fluctuation in the tubing is too large, which greatly reduces the probability of rubber plug damage due to excessive pressure fluctuation in the tubing during cementing operations, ensures the smooth progress of cementing operations, improves the work efficiency of cementing operations, and reduces cementing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic structural diagram of the pressure buffer device for cementing plug according to the present invention in a non-pressure relief state;

[0022] Figure 2 It is a structural schematic diagram of the pressure buffer device used for cementing rubber plug when it is connected to the rubber plug;

[0023] Figure 3 It is a schematic diagram of the structure of the protection tube;

[0024] Figure 4It is a structural schematic diagram of the special-shaped ring;

[0025] Figure 5 It is a structural diagram of the retaining ring.

[0026] All drawings in the present invention are schematic diagrams for illustrating structures and principles, and are not necessarily drawn according to actual sizes and proportions.

[0027] The specific meanings of the reference numerals in the figures are as follows:

[0028] 1. Main body; 11. First leakage hole; 12. Connecting section; 121. Thread; 122. First sealing groove; 13. Working section; 14. Bearing section; 141. Blind hole; 15. Tail section; 16. Middle cavity; 17. Auxiliary hole; 18. Second connecting hole; 2. Action part; 21. Piston; 211. Second leakage hole; 22. Spring; 23. Action chamber; 3. Protective tube; 31. Third leakage hole; 32. Annular groove; 33. First connecting hole; 4. Sealing assembly; 41. Special-shaped ring assembly; 411. Special-shaped ring; 412. Retaining ring; 42. First sealing ring; 43. Second sealing ring; 44. Third sealing ring; 5. Pin; 100. Pressure buffer device for cementing plug; 200. Plug. DETAILED DESCRIPTION

[0029] The present invention will be described in more detail below with reference to the accompanying drawings.

[0030] Figure 1 is a schematic structural diagram of a pressure buffer device 100 for cementing plug according to the present invention (hereinafter referred to as device 100 ) in a non-pressure relief state, Figure 2 It is a schematic diagram of the structure when the device 100 is connected to the rubber plug 200. As shown in the figure, the device 100 includes a body 1, a protective tube 3 and an action part 2. The body 1 is constructed as a hollow bottomless cylindrical structure, and a first leakage hole 11 is opened on the body 1, and the body 1 includes a connecting section 12 that is configured to be connected to the rubber plug 200. The protective tube 3 is also constructed as a hollow bottomless cylindrical structure, and the protective tube 3 is sleeved on the outside of the body 1, and a third leakage hole 31 is opened on the protective tube 3. The opening position of the third leakage hole 31 corresponds to the opening position of the first leakage hole 11. The action part 2 is arranged between the body 1 and the protective tube 3, including a piston 21 and a spring 22 arranged above the piston 21, and a second leakage hole 211 is opened on the piston 21. The position distribution of the second leakage hole 211 in the circumferential direction of the piston 21 corresponds to the position distribution of the first leakage hole 11 in the circumferential direction of the body 1. The piston 21 is also constructed to compress the spring 22 and move upward in response to abnormal cementing pressure (referring to the situation where the cementing operation pressure is too high), so that the first leakage hole 11, the second leakage hole 211 and the third leakage hole 31 are connected to perform pressure relief operations.

[0031] like Figure 2 As shown, during the specific operation, the staff connects the rubber plug 200 to the device 100 through the intermediate component, and lowers the device 100 into the appropriate position of the pipe string (not shown), and starts to inject cement slurry into the pipe string from the wellhead connected to the device 100. The cement slurry moves downward through the middle cavity 16 of the body 1 and the rubber plug 200 constructed as a hollow structure. When the density of cement slurry is too high and the flow of cement slurry is blocked, pressure will be generated below the device 100 and the plug 200, that is, at this time, the cementing pressure in the pipe string will increase abnormally and fluctuate greatly. Since there is a pressure holding section below the device 100 and the plug 200, the mud and liquid in the pipe string will flow upward through the plug 200 as the cement slurry is continuously injected at any time. Since the plug 200 has a one-way sealing effect, the liquid in the pipe string can only flow upward through the plug 200, which eventually causes the pressure holding section to expand to the device 100. Since there is a relatively narrow area above the plug 200, the pressure holding will act on the plug 200 and the piston 22 at the same time, exerting a downward thrust on the plug 200 and an upward thrust on the piston 21. When the thrust applied to the piston 21 is large enough, it will trigger the piston 21 to compress the spring 22 and move upward. Before the piston 21 moves upward, the first leakage hole 11, the second leakage hole 211 and the third leakage hole 31 are in a non-connected state. When the piston 21 moves upward to the right position, the first leakage hole 11, the second leakage hole 211 and the third leakage hole 31 are connected. The fluid such as cement slurry in the middle cavity 16 of the body 1 flows into the annulus between the device 100 and the pipe string through the channel formed by the first leakage hole 11, the second leakage hole 211 and the third leakage hole 31, thereby playing a pressure relief function, achieving a buffer for pressure fluctuations, avoiding the situation where the rubber plug 200 is released in advance when the pressure accumulated to the release pressure of the rubber plug 200, and ensuring the normal progress of cementing construction.

[0032] According to the device 100 of the present invention, through the combined use of the present invention 1, the protective tube 3 and the action part 2, an automatic pressure relief function is realized when the fluctuation is too large due to the abnormal increase of pressure in the tubular column, which greatly reduces the probability of premature release and damage of the rubber plug 200 due to excessive pressure fluctuation in the tubular during cementing operations, ensures the smooth progress of cementing operations, improves the work efficiency of cementing operations, and reduces cementing costs.

[0033] In some embodiments of the present invention, the body 1 , the protective tube 3 and the piston 21 maintain optimal coaxiality during the processing to ensure that the piston 21 can be reset under the action of the spring 22 after the pressure relief operation.

[0034] In some embodiments of the present invention, the spring 22 is a high-strength spring, and its elastic force requirement is that no leakage occurs under normal cementing pressure, and after exceeding the normal cementing cycle pressure, it will contract under the action of the piston 21 to complete the leakage action. It should be noted that the normal cementing pressure is less than the pressure that can release the rubber plug 200, and there is a large pressure range between the normal cementing pressure and the pressure that can release the rubber plug 200.

[0035] like Figure 1 As shown, in some embodiments of the present invention, the body 1 includes an operating section 13, a bearing section 14 and a tail end 15 which are sequentially connected and arranged from bottom to top and whose outer diameters are sequentially increased. The protective tube 3 abuts against the lower end surface of the tail section 15, an action chamber 23 is formed between the protective tube 3 and the operating section 13, the action part 2 is arranged in the action chamber 23, and the spring 22 is connected to the lower end surface of the bearing section 14. This design helps to improve the structural stability of the device 100.

[0036] like Figure 1 As shown, in some embodiments of the present invention, an auxiliary hole 17 is provided on the body 1. The auxiliary hole 17 is configured to penetrate the side wall of the body 1 so as to connect the middle cavity 16 of the body 1 with the action chamber 23. Through this design, during the movement of the spring 22 and the piston 21, the liquid or gas inside the action chamber 23 can flow into the middle cavity 16 through the auxiliary hole 17, thereby avoiding the situation where the piston 21 cannot move smoothly due to air pressure or hydraulic pressure due to the fact that the inside of the action chamber 23 is in a completely sealed state, thereby ensuring the smooth realization of the function of the device 100.

[0037] like Figure 1 As shown, in some embodiments of the present invention, the connecting section 12 is connected and disposed below the working section 13 , and the connecting section 12 is configured to have an outer diameter smaller than that of the connecting section 13 .

[0038] Preferably, in some embodiments of the present invention, a thread 121 for connecting with the rubber plug 200 is provided on the outer side of the connecting section 12 .

[0039] Preferably, in some embodiments of the present invention, a first sealing groove 122 is provided on the outer side of the connecting section 12 at a position above and / or below the thread 121. The staff can achieve the sealing function by installing a sealing member in the first sealing groove 122.

[0040] like Figure 1 and Figure 3As shown, in some embodiments of the present invention, an annular groove 32 is provided on the inner wall of the protective tube 3, and all the third leakage holes 31 are configured to be connected to the annular groove 32. Through the provision of the annular groove 32 and the structural design that the third leakage holes 31 are connected to the annular groove 32, as long as the liquid passing through the first leakage hole 11 and the second leakage hole 211 can flow into the annular groove 32, it can flow out from the third leakage hole 31 along the annular groove 32, thereby reducing the correspondence between the shapes of the first leakage hole 11 and the second leakage hole 211 and the positions of the first leakage hole 11 and the second leakage hole 211 and the shape and position relationship of the third leakage hole 31, while also achieving complete conduction between the first leakage hole 11, the second leakage hole 211 and the third leakage hole 31.

[0041] Further, in some embodiments of the present invention, the sum of the flow areas of all the third leakage holes 31, the sum of the flow areas of all the first leakage holes 11, and the sum of the flow areas of all the second leakage holes 211 are all constructed to be not less than the flow area of ​​the body 1. Through this design, when there is a pressure-blocking condition in the tubing string, the liquid flowing into the body 1 can quickly and completely pass through the first leakage holes 11, the second leakage holes 211, and the third leakage holes 31 and flow into the annulus between the tubing string and the device 100, thereby realizing the function of quickly relieving the pressure-blocking condition and ensuring the smooth progress of the cementing operation.

[0042] Preferably, in some embodiments of the present invention, the sum of the flow areas of all the third leakage holes 31 , the sum of the flow areas of all the first leakage holes 11 , and the sum of the flow areas of all the second leakage holes 211 are constructed to be equal to the flow area of ​​the body 1 .

[0043] like Figure 1 As shown, in some embodiments of the present invention, the device 100 includes a sealing assembly 4 disposed between the piston 21 and the body 1, between the piston 21 and the protective cylinder 3, and between the protective cylinder 3 and the body 1. Through the design of the sealing assembly 4, a partial sealing of the action chamber 23 is achieved, so that the hydraulic pressure outside the action chamber 23 can smoothly push the piston 21 to move, thereby ensuring the smooth realization of the function of the device 100.

[0044] like Figure 1 , Figure 4 and Figure 5As shown, in some embodiments of the present invention, the sealing assembly 4 includes a special-shaped ring assembly 41 and a first sealing ring 42, which are arranged between the body 1 and the piston 21 and are respectively located below and above the first leakage hole 11, and the special-shaped ring assembly 41 includes a special-shaped ring 41 and two retaining rings 412 located on the upper and lower sides of the special-shaped ring 411. The special-shaped ring 41 is constructed to have a transverse cross-section similar to "Ω", and it is combined with the two retaining rings 412 to form a relatively flatter sealing surface on the side facing the piston 21, and the special-shaped ring 41 is combined with the two retaining rings 412 to form a firm sealing structure, which can greatly reduce the probability of the special-shaped ring assembly 41 falling off and being damaged due to the sliding of the piston 21 and the scratching of the second leakage hole 211, and ensure the smooth progress of subsequent cementing operations.

[0045] Furthermore, in some embodiments of the present invention, in order to achieve a better sealing effect, the special-shaped ring assembly 41 is configured to remain within the sealing stroke of the special-shaped ring assembly 41 when the second leakage hole 211 performs a pressure relief operation. This embodiment can be achieved by adjusting the maximum distance between the special-shaped ring assembly 41 and the first leakage hole 11 to be smaller than the length of the portion of the piston 21 below the second leakage hole 211.

[0046] In some embodiments of the present invention, the retaining ring 412 is selected to be an “L”-shaped retaining ring having an “L”-shaped cross section or a “T”-shaped retaining ring having a “T”-shaped cross section.

[0047] like Figure 1 As shown, in some embodiments of the present invention, a second sealing ring 43 is provided between the piston 21 and the protection tube 3 , and a third sealing ring 44 is provided between the protection tube 3 and the body 1 .

[0048] It is obvious that corresponding sealing grooves are provided on the body 1 , the piston 21 and the protective tube 3 at positions corresponding to the special-shaped ring assembly 41 , the first sealing ring 42 , the second sealing ring 43 and the third sealing ring 44 .

[0049] In some embodiments of the present invention, the first sealing ring 42 , the second sealing ring 43 , and the third sealing ring 44 are all selected to be “O”-shaped rings with an “O”-shaped cross-section.

[0050] In some embodiments of the present invention, the piston 21 is structured to have a micro-textured surface, that is, a plurality of fine lines are provided on the surface of the piston 21. This treatment enables the piston 21 to maintain a good lubrication effect during the reciprocating motion.

[0051] In some embodiments of the present invention, the piston 21 is made of aluminum bronze.

[0052] In some embodiments of the present invention, in order to enable the device 100 to be used for a long time in an underground environment, the body 1, the protective tube 3 and the action part 2 are all constructed to be rust-proof and anti-corrosion treated.

[0053] like Figure 1 As shown, in some embodiments of the present invention, a first connection hole 33 is provided in the protective tube 3 at a position corresponding to the bearing section 14, and a blind hole 141 is provided in the bearing section 14 at a position corresponding to the position of the first connection hole 33. The protective tube 3 is fixedly connected to the body 1 by inserting the pin 5 into the first connection hole 33 and the blind hole 141.

[0054] like Figure 1 As shown, in some embodiments of the present invention, a second connection hole 18 is provided on the tail section 15 for connecting the device 100 with other downhole tools.

[0055] According to the device 100 of the present invention, through the combined use of the present invention 1, the protective tube 3 and the action part 2, an automatic pressure relief function is achieved when the fluctuation is too large due to the abnormal increase of pressure in the tubular column, which greatly reduces the probability of damage to the rubber plug 200 due to excessive pressure fluctuation in the tubular during cementing operations, ensures the smooth progress of cementing operations, improves the work efficiency of cementing operations, and reduces cementing costs.

[0056] In the present invention, "connection" includes "direct connection" and "indirect connection".

[0057] In the present invention, the specific meanings of the terms "upper", "lower", "left", "right", "inner", "outer", "middle", "side" and the like when indicating directions are as follows: Figure 1 The drawing state of the device 100 is used as a reference.

[0058] Finally, it should be noted that although the present invention has been described in detail with reference to the preferred embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present invention. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there is no structural conflict. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A pressure buffer device for cementing plug, comprising: The body (1) is constructed as a hollow cylindrical structure, and is provided with a first leakage hole (11) and a connecting section (12) configured to be connected to a rubber plug (200); The protective tube (3) is constructed as a hollow cylindrical structure, is sleeved on the outside of the body (1), and comprises a third leakage hole (31) opened on the protective tube (3); and The action part (2) is arranged between the body (1) and the protection tube (3), and comprises a piston (21) and a spring (22) arranged above the piston (21). A second leakage hole (211) is opened on the piston (21). The piston (21) is configured to compress the spring (22) and move upward in response to abnormal cementing pressure, so that the first leakage hole (11), the second leakage hole (211) and the third leakage hole (31) are connected to perform pressure relief operations.

2. The pressure buffer device for cementing plug according to claim 1, characterized in that: The body (1) comprises an operating section (13), a bearing section (14) and a tail section (15) which are sequentially connected and arranged in order from bottom to top and whose outer diameters increase sequentially; the protective tube (3) is in contact with the lower end surface of the tail section (15); the action part (2) is arranged inside an action chamber (23) between the protective tube (3) and the operating section (13); and the spring (22) is connected to the lower end surface of the bearing section (14).

3. The pressure buffer device for cementing plug according to claim 2, characterized in that: The main body (1) is provided with an auxiliary hole (17) which penetrates through the side wall of the main body (1) so as to connect the middle cavity (16) of the main body (1) with the action chamber (23).

4. The pressure buffer device for cementing plug according to claim 3, characterized in that: The connecting section (12) is arranged below the working section (13), and the connecting section (12) is configured to have an outer diameter smaller than that of the working section (13).

5. The pressure buffer device for cementing plug according to claim 4, characterized in that: An annular groove (32) is provided on the inner wall of the protection tube (3), and the third leakage holes (31) are configured to be in communication with the annular groove (32).

6. The pressure buffer device for cementing plug according to claim 5, characterized in that: The sum of the flow areas of all the third leakage holes (31), the sum of the flow areas of all the first leakage holes (11), and the sum of the flow areas of all the second leakage holes (211) are all constructed to be no less than the flow area of ​​the body (1).

7. The pressure buffer device for cementing plug according to any one of claims 1 to 6, characterized in that: It comprises a sealing component (4) arranged between the piston (21) and the body (1), between the piston (21) and the protective cylinder (3), and between the protective cylinder (3) and the body (1).

8. The pressure buffer device for cementing plug according to claim 7, characterized in that: The sealing assembly (4) comprises a special-shaped ring assembly (41) and a first sealing ring (42) which are arranged between the body (1) and the piston (21) and are respectively located below and above the first leakage hole (11); the special-shaped ring assembly (41) comprises a special-shaped ring (411) and two retaining rings (412) located on the upper and lower sides of the special-shaped ring (411).

9. The pressure buffer device for cementing plug according to claim 8, characterized in that: The special-shaped ring assembly (41) is constructed so that when the second leakage hole (211) performs the pressure relief operation, it remains within the sealing stroke of the special-shaped ring assembly (41).

10. The pressure buffer device for cementing plug according to claim 9, characterized in that: The piston (21) is structured such that its surface is subjected to micro-texture treatment.

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