Air-tight seal oil casing pipe screwed joint

Abstract

The utility model relates to an air-tight seal oil casing pipe screwed joint. The sealing structure comprises an internal thread part, internal threads and an internal sealing structure extending to the inner side of the internal threads are arranged on the inner surface of the internal thread part, and the internal sealing structure comprises a cylindrical hole, a short conical hole, a long conical hole, a transition arc and a torque shoulder which are sequentially arranged in the direction away from the internal threads and connected. The external thread part is arranged at the end of the pipe, external threads and an external sealing structure extending to the inner side of the external threads are arranged on the outer surface of the external thread part, the internal threads are matched with the external threads, and the external sealing structure comprises a cylindrical face, a conical face, a main sealing arc, an end transition arc and an end face which are sequentially arranged in the direction away from the external threads and connected; after the internal thread piece and the external thread piece are screwed in a matched mode, the cylindrical hole and the cylindrical face, the short conical hole and the conical face, the long conical hole and the main sealing arc, and the torque shoulder and the end face are all in interference fit. The sealing reliability of the joint is enhanced.

Description

Technical Field

[0001] The utility model relates to the technical field of oil pipe thread connection, in particular to an airtight oil casing thread joint. Background Art

[0002] Oil casing is a special pipe used for the extraction of oil and natural gas. Each oil casing is about 10 meters long and is connected by threads to form a pipe string as long as 3,000-8,000 meters. During service, the pipe string is subjected to various loads for a long time, and the threaded connection is the weakest link in the pipe string.

[0003] Threaded connection parts are generally called joints. Joints should have excellent technical performance. They should be easy to process and manufacture, strong and durable, and have high connection strength and maintain good sealing performance under composite loads such as tension, compression, bending and torsion.

[0004] Currently, conventional oil casing and tubing typically utilize API joints, which conform to API (American Petroleum Institute) standards and are technologically mature and suitable for general use. However, in recent years, the harsher conditions in which crude oil and natural gas are extracted have led to an increasing use of premium threaded joints.

[0005] A search of prior art literature revealed a Chinese patent application with the publication number CN 207212289 U, dated April 10, 2018. The utility model patent is titled "Oil Casing, Oil Casing Coupling, and Oil Casing Joint." This patent improves API joints. The patent relates to a threaded joint comprising a coupling and a pipe body. The coupling is symmetrically arranged, from the outside inward, with internal threads, a cylindrical sealing structure, and a counter-torque shoulder. Correspondingly, the pipe body is sequentially arranged with external threads, a spherical sealing structure, and a counter-end face. When the joint is tightened, the spherical / cylindrical surface experiences radial interference, providing the primary sealing function. The internal threads and external threads form an interference fit, providing a secondary sealing function. The counter-torque shoulder and the counter-end face experience axial interference, providing a make-up positioning function and also providing a secondary sealing function. The utility model utilizes a sealing structure composed of a cylindrical sealing portion adjacent to the internal threads and a spherical sealing portion adjacent to the external threads, combined with the auxiliary sealing effect of the shoulder surface, to achieve excellent sealing performance. Its disadvantage is that there is only one radial metal sealing structure. Once the sealing structure composed of the cylindrical seal and the spherical seal fails, the joint will not be able to perform the sealing function and the sealing reliability is not high.

[0006] With the development of drilling technology, ultra-deep wells, high-temperature and high-pressure natural gas wells have put forward higher requirements on the sealing performance of joints. Existing technology can no longer meet them, and it is necessary to design special threaded joints with higher sealing reliability. Summary of the Invention

[0007] To this end, the utility model provides an airtight oil casing threaded joint, which enhances the sealing reliability of the joint and is suitable for use in ultra-deep wells, high-temperature, and high-pressure natural gas wells.

[0008] In order to solve the above technical problems, the utility model provides an airtight oil casing threaded joint, comprising:

[0009] An internal threaded part, wherein the inner surface of the internal threaded part is provided with an internal thread and an internal sealing structure extending inside the internal thread, the internal sealing structure comprising a cylindrical hole, a short tapered hole, a long tapered hole, a transition arc and a torque shoulder sequentially arranged and connected in a direction away from the internal thread;

[0010] An external threaded member is provided at the end of the pipe, wherein the outer surface of the external threaded member is provided with an external thread and an external sealing structure extending inside the external thread, the internal thread and the external thread cooperate with each other, and the external sealing structure includes a cylindrical surface, a conical surface, a main sealing arc, an end transition arc and an end surface sequentially arranged and connected in a direction away from the external thread;

[0011] Among them, after the internal threaded part and the external threaded part are tightened together, interference fit is achieved between the cylindrical hole and the cylindrical surface, between the short conical hole and the conical surface, between the long conical hole and the main sealing arc, and between the torque shoulder and the end face.

[0012] In one embodiment of the present invention, the inclination angle between the torque shoulder and the radial section of the internal threaded member and the inclination angle between the end face and the radial section of the external threaded member are both α;

[0013] The inclination angle between the short conical hole and the radial section of the internal threaded member and the inclination angle between the conical surface and the radial section of the external threaded member are both β;

[0014] Among them, α=9~18°, β=(2.0~2.5)ɑ.

[0015] In one embodiment of the present invention, the length of the main sealing arc is L1, the length of the conical surface is L2, the length of the long conical hole is L3, and the length of the short conical hole is L4;

[0016] Among them, L1=7.5mm~12.5mm, L2=2.0mm~2.5mm, L3=L1+1.5mm, L4=L2-0.5mm.

[0017] In one embodiment of the present invention, the radius of the main sealing arc is 55-60 mm. After the internal threaded component and the external threaded component are tightened together, the main sealing arc is tangent to the long conical hole.

[0018] In one embodiment of the present invention, after the internal threaded part and the external threaded part are tightened together, a first fitting gap for storing thread compound is formed between the boundary of the fitting place between the internal thread and the external thread and the boundary of the fitting place between the cylindrical hole and the cylindrical surface, and the gap value of the first fitting gap is between 1.5 and 2.5 mm.

[0019] In one embodiment of the present invention, after the internal threaded part and the external threaded part are tightened together, a second fitting gap for storing thread grease is formed between the boundary of the fitting place between the short conical hole and the conical surface and the boundary of the fitting place between the long conical hole and the main sealing arc, and the gap value of the second fitting gap is between 1.5 and 2.5 mm.

[0020] In one embodiment of the present invention, a third fitting gap for storing thread grease is formed between the boundary of the long conical hole and the main sealing arc and the boundary of the torque shoulder and the end face, and the gap value of the third fitting gap is 1.5 to 2.5 mm.

[0021] In one embodiment of the present invention, the interference fit amount is as follows:

[0022] When the outer diameter of the pipe is 60.3mm to 101.6mm:

[0023] The interference between the cylindrical hole and the cylindrical surface is 0.10mm to 0.12mm;

[0024] The interference between the long conical hole and the main sealing arc is 0.25mm to 0.30mm;

[0025] The interference between the torque shoulder and the end face is 0.08mm to 0.10mm;

[0026] When the outer diameter of the pipe is 114.3mm to 244.5mm:

[0027] The interference between the cylindrical hole and the cylindrical surface is 0.25mm to 0.30mm;

[0028] The interference between the long conical hole and the main sealing arc is 0.55mm to 0.60mm;

[0029] The interference between the torque shoulder and the end face is 0.13mm to 0.15mm;

[0030] When the outer diameter of the pipe is 250.8mm to 339.7mm:

[0031] The interference between the cylindrical hole and the cylindrical surface is 0.35mm to 0.40mm;

[0032] The interference between the long conical hole and the main sealing arc is 0.95mm to 1.10mm;

[0033] The interference between the torque shoulder and the end face is 0.15 mm to 0.20 mm.

[0034] The above technical solution of the utility model has the following advantages compared with the prior art:

[0035] This utility model describes an airtight oil casing threaded joint. The primary seal comprises three metal seals: a cylindrical hole and a cylindrical surface, a short tapered hole and a tapered surface, and a long tapered hole and a primary sealing arc. The torque shoulder also provides auxiliary sealing. Clearances are provided at the front, middle, and rear of the multiple metal seals to store thread grease, effectively lubricating the sealing surfaces. Consequently, the joint's sealing reliability is significantly enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0037] Figure 1 Schematic diagram of the joint structure of the present invention.

[0038] Figure 2 An enlarged view of the secret part of this utility model.

[0039] Figure 3 Schematic diagram of the sealing structure of an internally threaded part.

[0040] Figure 4 Schematic diagram of the sealing structure of an external threaded part.

[0041] Description of the accompanying drawings:

[0042] 1. Internal threaded part; 2. Internal thread; 3. Internal sealing structure; 4. External threaded part; 5. External thread; 6. External sealing structure; 7. Cylindrical surface; 8. Conical surface; 9. Main sealing arc; 10. End transition arc; 11. End face; 12. Cylindrical hole; 13. Short conical hole; 14. Long conical hole; 15. Transition arc; 16. Torque shoulder; 17. First gap; 18. Second gap; 19. Third gap. DETAILED DESCRIPTION

[0043] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0044] In the present invention, if there is a description of directions (up, down, left, right, front and back), it is only for the convenience of describing the technical solution of the present invention, and does not indicate or imply that the technical features referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0045] In this utility model, "several" means one or more, "multiple" means more than two, "greater than," "less than," "exceeds," etc. are understood to exclude the number itself; "above," "below," "within," etc. are understood to include the number itself. In the description of this utility model, the use of "first" or "second" is solely for the purpose of distinguishing technical features and is not to be construed as indicating or implying relative importance, implicitly specifying the number of the indicated technical features, or implicitly specifying the order of the indicated technical features.

[0046] In this utility model, unless otherwise expressly defined, terms such as "disposed," "installed," and "connected" should be interpreted broadly. For example, they may refer to direct connection or indirect connection through an intermediate medium; fixed connection or detachable connection or integral molding; mechanical connection or electrical connection or mutual communication; and internal connection between two components or interaction between two components. Those skilled in the art can reasonably determine the specific meanings of these terms in this utility model based on the specific content of the technical solution.

[0047] Example 1

[0048] Reference Figure 1 、 Figure 2 As shown, a gas-tight oil casing threaded joint comprises:

[0049] An internally threaded component 1, wherein the inner surface of the internally threaded component 1 is provided with an internal thread 2 and an internal sealing structure 3 extending inside the internal thread 2, the internal sealing structure 3 comprising a cylindrical hole 12, a short tapered hole 13, a long tapered hole 14, a transition arc 15, and a torque shoulder 16, which are sequentially arranged and connected in a direction away from the internal thread 2;

[0050] An external threaded member 4 is provided at the end of the pipe. The outer surface of the external threaded member 4 is provided with an external thread 5 and an external sealing structure 6 extending inside the external thread 5. The internal thread 2 cooperates with the external thread 5. The external sealing structure 6 includes a cylindrical surface 7, a conical surface 8, a main sealing arc 9, an end transition arc 10 and an end surface 11, which are sequentially arranged and connected in a direction away from the external thread 5;

[0051] Among them, after the internal threaded part 1 and the external threaded part 4 are tightened together, interference fit is achieved between the cylindrical hole 12 and the cylindrical surface 7, between the short conical hole 13 and the conical surface 8, between the long conical hole 14 and the main sealing arc 9, and between the torque shoulder 16 and the end face 11.

[0052] With this arrangement, when the joint is tightened, internal thread 2 and external thread 5 form an interference fit, providing a connection. Cylindrical hole 12 and cylindrical surface 7, short tapered hole 13 and tapered surface 8, and long tapered hole 14 and main sealing arc 9 form an interference fit, forming a multi-metal seal. Torque shoulder 16 and end surface 11 form an interference fit, providing a snap-on positioning function and also providing an auxiliary sealing effect. This multi-metal seal significantly improves sealing reliability.

[0053] Specifically, internal threads 2 and an internal sealing structure 3 are machined on the inner surface of an internally threaded component 1, while external threads 5 and an external sealing structure 6 are machined on the outer surface of an externally threaded component 4. These threads are tapered pipe threads with a taper of 1:16, a 10° lead angle, and a -3° load angle, resulting in a serrated thread shape. When screwed together, they function as a connection, providing tensile and compressive resistance equivalent to that of the pipe body. The internal sealing structure 3 and the external sealing structure 6 work together to provide a seal, providing an airtight seal that reaches the yield pressure of the pipe's inner wall.

[0054] Reference Figure 3 、 Figure 4 As shown, the inclination angle between the torque shoulder 16 and the radial section of the internal threaded member 1 and the inclination angle between the end face 11 and the radial section of the external threaded member 4 are both α;

[0055] The inclination angle between the short conical hole 13 and the radial section of the internal threaded component 1 and the inclination angle between the conical surface 8 and the radial section of the external threaded component 4 are both β; wherein α=9~18°, β=(2.0~2.5)ɑ.

[0056] Reference Figure 3 、 Figure 4 As shown, the length of the main sealing arc 9 is L1, the length of the conical surface 8 is L2, the length of the long conical hole 14 is L3, and the length of the short conical hole 13 is L4;

[0057] Among them, L1=7.5mm~12.5mm, L2=2.0mm~2.5mm, L3=L1+1.5mm, L4=L2-0.5mm.

[0058] Specifically, the radius of the main sealing arc 9 is 55 to 60 mm. After the internally threaded member 1 and the externally threaded member 4 are tightened together, the main sealing arc 9 is tangent to the long conical hole 14. A larger arc radius can provide a larger contact area between the metal sealing surfaces, and the tangency between the main sealing arc 9 and the long conical hole 14 can achieve a more uniform distribution of contact pressure on the metal sealing surfaces.

[0059] Specifically, refer to Figure 2 As shown, after the internal threaded part 1 and the external threaded part 4 are tightened together, a first fitting gap for storing thread compound is formed between the boundary of the fitting place between the internal thread 2 and the external thread 5 and the boundary of the fitting place between the cylindrical hole 12 and the cylindrical surface 7, and the gap value of the first fitting gap is 1.5 to 2.5 mm.

[0060] After the internal threaded part 1 and the external threaded part 4 are tightened together, a second fitting gap for storing thread compound is formed between the boundary of the short conical hole 13 and the conical surface 8 and the boundary of the long conical hole 14 and the main sealing arc 9. The gap value of the second fitting gap is 1.5 to 2.5 mm.

[0061] A third fitting gap for storing thread compound is formed between the boundary between the long conical hole 14 and the main sealing arc 9 and the boundary between the torque shoulder 16 and the end face 11. The gap value of the third fitting gap is 1.5 to 2.5 mm.

[0062] By setting the first to third fitting gaps at the front, middle and rear parts of the multiple metal seals to store sufficient thread grease, the sealing surface is well lubricated, the anti-galling ability is stronger, the sealing surface is avoided from being damaged by friction, and the sealing reliability is improved.

[0063] Specifically, the interference fit is as follows (all units are mm):

[0064]

[0065] Traditional special threaded joints have only one main sealing structure, either spherical / cylindrical or conical / conical. The utility model has three main sealing structures, including cylindrical / conical, conical / conical and spherical / conical. Once one of the metal seals is damaged, the remaining two can still function independently as seals, thereby enhancing the sealing ability and sealing reliability.

[0066] Example 2

[0067] This example is for a 73.0 x 5.51 mm diameter oil pipe made of P110 steel. The pipe's geometric dimensions, including outer diameter and wall thickness, conform to API standards, and the material meets API requirements for P110 steel. Both the internal and external threads 2 and 5 have a tooth height of 1.0 mm and a pitch of 3.175 mm (8 threads / 25.4 mm). The guide angle is 10°, the load angle is -3°, and the taper is 1:16.

[0068] The dimensions of the inner sealing structure 3 are: inclination angle α = 15°, inclination angle β = 35°. The length of the main sealing arc 9 is L1 = 7.5mm, correspondingly, the length of the long conical hole 14 is L3 = 9.0mm, the length of the conical surface 8 is L2 = 2.0mm, correspondingly, the length of the short conical hole 13 is L4 = 1.5mm. The radius of the main sealing arc 9 on the outer sealing structure 6 is 55mm. After the joint is tightened, the main sealing arc 9 is tangent to the long conical hole 14 on the inner sealing structure 3, and the taper of the long conical hole 14 is 1:10. The front, middle and rear parts of the multiple metal seals are provided with a first gap 17, a second gap 18 and a third gap 19 for storing thread grease, and the gap value is 2.0mm. The radial interference between the cylindrical hole 12 and the cylindrical surface 7 is 0.10mm, the interference between the long conical hole 14 and the main sealing arc 9 is 0.28mm, and the interference between the torque shoulder 16 and the end face 11 is 0.1mm. The airtight sealing resistance of this joint can reach over 101MPa and the connection strength is over 887kN.

[0069] Example 3

[0070] This embodiment is for casing measuring 193.7 mm x 10.92 mm in diameter, made of Q125 steel. The casing body's geometric dimensions, including outer diameter and wall thickness, conform to API standards. The casing material meets the API standard requirements for Q125 steel-grade oil pipe. The internal thread 2 and external thread 5 have tooth heights of 1.775 mm and 1.575 mm, respectively, with a pitch of 5.08 mm (5 threads / 25.4 mm). The guide angle is 10°, the load angle is -3°, and the taper is 1:16.

[0071] The dimensions of the inner sealing structure 3 are: inclination angle α1 = 15°, inclination angle β1 = 35°. The length of the main sealing arc 9 is L1 = 12.5mm, corresponding to the length of the long conical hole 14 is L3 = 14.0mm, and the length of the conical surface 8 is L2 = 2.5mm, corresponding to the length of the short conical hole 13 is L4 = 2.0mm. The radius of the main sealing arc 9 on the outer sealing structure 6 is 60mm. After the joint is tightened, the main sealing arc 9 is tangent to the long conical hole 14 on the inner sealing structure 3, and the taper of the long conical hole 14 is 1:10. The front, middle and rear parts of the multiple metal seals are provided with a first gap 17, a second gap 18 and a third gap 19 for storing thread grease, with a gap value of 2.0mm. The radial interference between the cylindrical hole 12 and the cylindrical surface 7 is 0.30mm, the interference between the long conical hole 14 and the main sealing arc 9 is 0.60mm, and the interference between the torque shoulder 16 and the end face 11 is 0.13mm. The airtight sealing resistance of this joint can reach more than 85MPa and the connection strength is more than 5405kN.

[0072] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the utility model and are not limiting. Although the utility model is described in detail with reference to examples, ordinary technicians in this field should understand that the technical solution of the utility model can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the utility model, which should be included in the scope of the claims of the utility model.

Claims

1. A gas-tight oil-tight casing threaded joint, characterized in that: include: An internal threaded part (1), wherein the inner surface of the internal threaded part (1) is provided with an internal thread (2) and an internal sealing structure (3) extending inside the internal thread (2), the internal sealing structure (3) comprising a cylindrical hole (12), a short conical hole (13), a long conical hole (14), a transition arc (15) and a torque shoulder (16) sequentially arranged and connected in a direction away from the internal thread (2); An external threaded part (4) is provided at the end of the pipe, the outer surface of the external threaded part (4) is provided with an external thread (5) and an external sealing structure (6) extending inside the external thread (5), the internal thread (2) and the external thread (5) cooperate, and the external sealing structure (6) includes a cylindrical surface (7), a conical surface (8), a main sealing arc (9), an end transition arc (10) and an end surface (11) which are sequentially arranged and connected in a direction away from the external thread (5); Wherein, after the internal threaded part (1) and the external threaded part (4) are tightened together, interference fit is achieved between the cylindrical hole (12) and the cylindrical surface (7), between the short conical hole (13) and the conical surface (8), between the long conical hole (14) and the main sealing arc (9), and between the torque shoulder (16) and the end surface (11).

2. The airtight oil casing threaded joint according to claim 1, characterized in that: The inclination angle between the torque shoulder (16) and the radial section of the internal threaded part (1) and the inclination angle between the end face (11) and the radial section of the external threaded part (4) are both α; The inclination angle between the short conical hole (13) and the radial section of the internal threaded part (1) and the inclination angle between the conical surface (8) and the radial section of the external threaded part (4) are both β; Among them, α=9~18°, β=(2.0~2.5)ɑ.

3. The airtight oil casing threaded joint according to claim 1, characterized in that: The length of the main sealing arc (9) is L1, the length of the conical surface (8) is L2, the length of the long conical hole (14) is L3, and the length of the short conical hole (13) is L4; Among them, L1=7.5mm~12.5mm, L2=2.0mm~2.5mm, L3=L1+1.5mm, L4=L2-0.5mm.

4. The airtight oil casing threaded joint according to claim 1, characterized in that: The radius of the main sealing arc (9) is 55 to 60 mm. After the internal threaded part (1) and the external threaded part (4) are tightened together, the main sealing arc (9) is tangent to the long conical hole (14).

5. The airtight oil casing threaded joint according to claim 1, characterized in that: After the internal threaded part (1) and the external threaded part (4) are tightened together, a first fitting gap for storing thread grease is formed between the boundary of the fitting location of the internal thread (2) and the external thread (5) and the boundary of the fitting location of the cylindrical hole (12) and the cylindrical surface (7), and the gap value of the first fitting gap is between 1.5 and 2.5 mm.

6. The airtight oil casing threaded joint according to claim 1, characterized in that: After the internal threaded part (1) and the external threaded part (4) are tightened together, a second fitting gap for storing thread grease is formed between the boundary of the fitting position of the short conical hole (13) and the conical surface (8) and the boundary of the fitting position of the long conical hole (14) and the main sealing arc (9), and the gap value of the second fitting gap is 1.5 to 2.5 mm.

7. The airtight oil casing threaded joint according to claim 1, characterized in that: A third fitting gap for storing thread grease is formed between the boundary of the fitting location of the long conical hole (14) and the main sealing arc (9) and the boundary of the fitting location of the torque shoulder (16) and the end face (11), and the gap value of the third fitting gap is 1.5 to 2.5 mm.

8. The airtight oil casing threaded joint according to claim 1, characterized in that: The interference fit is as follows: When the outer diameter of the pipe is 60.3mm to 101.6mm: The interference between the cylindrical hole (12) and the cylindrical surface (7) is 0.10 mm to 0.12 mm; The interference between the long conical hole (14) and the main sealing arc (9) is 0.25 mm to 0.30 mm; The interference between the torque shoulder (16) and the end surface (11) is 0.08 mm to 0.10 mm; When the outer diameter of the pipe is 114.3mm to 244.5mm: The interference between the cylindrical hole (12) and the cylindrical surface (7) is 0.25 mm to 0.30 mm; The interference between the long conical hole (14) and the main sealing arc (9) is 0.55 mm to 0.60 mm; The interference between the torque shoulder (16) and the end surface (11) is 0.13 mm to 0.15 mm; When the outer diameter of the pipe is 250.8mm to 339.7mm: The interference between the cylindrical hole (12) and the cylindrical surface (7) is 0.35 mm to 0.40 mm; The interference between the long conical hole (14) and the main sealing arc (9) is 0.95 mm to 1.10 mm; The interference between the torque shoulder (16) and the end face (11) is 0.15 mm to 0.20 mm.

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