Threaded joint for oil casing

Abstract

The invention provides an oil casing pipe screwed joint. The oil casing screwed joint comprises an inner screwed joint and an outer screwed joint, and the sealing part comprises a sealing cambered surface which is arranged on the peripheral side of the outer screwed joint and protrudes in the direction away from the central axis in the radial direction of the oil casing screwed joint. The composite sealing surface is arranged on the inner peripheral side of the internal thread joint and comprises a main sealing conical surface and an auxiliary sealing conical surface which are connected with each other and are sequentially arranged, the distance between the main sealing conical surface and the central axis and the distance between the auxiliary sealing conical surface and the central axis are gradually reduced, and an angle beta 1 is formed between the main sealing conical surface and the central axis; an angle beta 2 is formed between the auxiliary sealing conical surface and the central axis, and the angle beta 1 is larger than the angle beta 2. According to the technical scheme, the problems that in the prior art, an oil casing pipe threaded connector is poor in sealing stability, compression resistance and thread gluing resistance under the action of combined loads are solved.

Description

[0001] This application claims priority to the patent application filed on April 29, 2025, with China National Intellectual Property Administration, application number 2025105582539, entitled "Oil-Sheet Pipe Threaded Joint". Technical Field

[0002] This invention relates to the field of oil pipeline engineering technology, and more specifically, to an oil casing threaded joint. Background Technology

[0003] As the development environment of oil and gas fields becomes increasingly complex, stricter requirements are placed on the sealing performance of oil casing threaded joints. These joints must maintain excellent sealing robustness and excellent compression performance under various complex and harsh working conditions such as tension, compression, internal pressure, external pressure, bending, and temperature, as well as accidental external factors.

[0004] Standard API (American Petroleum Institute) threaded tubing suffers from design flaws that result in low threaded joint strength, poor resistance to combined loads, and lack of gas-tightness, making it unsuitable for demanding well conditions. It is mainly used in shallow wells, low-pressure wells, and other wells with less stringent operating requirements.

[0005] Chinese patent publication number CN2575286Y discloses a utility model patent entitled "Oil and Sleeve Threaded Joint". The patented technology features an improved trapezoidal thread structure and a sealing structure with a cylindrical outer sealing surface and a spherical inner sealing surface. This sealing structure can maintain stable sealing performance under the stress of the oil and sleeve. However, the use of a spherical inner sealing surface can lead to difficulties in production, processing and testing. Moreover, since the spherical and cylindrical surfaces are in line contact, repeated uncoupling can easily result in poor anti-sticking performance and accidental damage to the sealing structure.

[0006] Chinese patent publication number CN202946041U discloses a utility model patent technology entitled "Gas-tight Sawtooth Oil Well Pipe Threaded Joint Structure". This technology adopts a sawtooth tooth structure with the tooth top and bottom parallel to the thread generatrix, resulting in high thread connection strength and reducing the impact of external loads on sealing performance. The sealing structure and the positioning shoulder form a wedge structure to maintain sealing stability. This patented threaded joint has good connection strength and sealing performance. However, since the sealing structure is close to the positioning shoulder, its sealing performance is affected by the stress state of the positioning shoulder, resulting in low sealing stability. When the oil well pipe threaded joint is subjected to external loads, it is prone to poor sealing robustness. Summary of the Invention

[0007] The main objective of this invention is to provide an oil-jacket threaded joint to solve the problems of poor sealing robustness, poor compression resistance, and poor anti-galling performance of existing oil-jacket threaded joints under combined loads.

[0008] To achieve the above objectives, the present invention provides a threaded connector for an oil casing pipe. The oil casing pipe threaded connector has a central axis and includes an internal threaded connector and an external threaded connector. Along the central axis, a threaded portion, a first grooved portion, a sealing portion, a second grooved portion, and a shoulder are sequentially provided between the internal threaded connector and the external threaded connector. The threaded portion includes an external thread provided on the external threaded connector and an internal thread provided on the internal threaded connector. The internal and external threads are threadedly connected. The first and second grooved portions are capable of storing thread grease. The sealing portion includes a sealing arc surface provided on the outer periphery of the external threaded connector, protruding radially away from the central axis along the oil casing pipe threaded connector. The sealing surface is located on the inner circumference of the internal threaded joint. The composite sealing surface includes a main sealing cone surface and an auxiliary sealing cone surface connected to each other. In the direction from the pipe end of the internal threaded joint to the pipe body of the internal threaded joint, the main sealing cone surface and the auxiliary sealing cone surface are arranged sequentially, and the distance between the main sealing cone surface and the central axis of both the main sealing cone surface and the auxiliary sealing cone surface gradually decreases. The main sealing cone surface has an angle β1 with the central axis, and the auxiliary sealing cone surface has an angle β2 with the central axis. Angle β1 is greater than angle β2. When the internal threaded joint and the external threaded joint are screwed together, the main sealing cone surface and the sealing arc surface are sealed together. When the oil sleeve threaded joint is subjected to external load, both the main sealing cone surface and the auxiliary sealing cone surface are sealed together.

[0009] Furthermore, angles β1 and β2 satisfy the condition: 0.2° < angle β1 - angle β2 < 2°.

[0010] Furthermore, the range of angle β1 is: 4°≤β1≤9°; and / or, the range of angle β2 is: 3°≤β2≤8°.

[0011] Furthermore, the axial length L21 of the main sealing cone surface is in the range of 2.5mm≤L21≤4mm; and / or, the axial length L22 of the auxiliary sealing cone surface is in the range of 1mm≤L22≤2.5mm.

[0012] Furthermore, the range of the arc radius R10 of the sealing arc surface is: 200mm≤R10≤500mm.

[0013] Furthermore, the nose of the external threaded connector has an axial length L10, and the sealing arc surface has an axial length L11. The ratio of the axial length L11 to the axial length L10 satisfies: 0.3≤L11 / L10≤0.9.

[0014] Furthermore, when the external threaded connector and the internal threaded connector are screwed together, the sealing arc surface and the main sealing cone surface first make contact at the initial contact tangent point P. There is an axial distance L30 between the tangent point P and the external thread. The nose of the external threaded connector has an axial length L10. The ratio of the axial distance L30 to the axial length L10 satisfies: 0.56≤L30 / L10≤0.86.

[0015] Furthermore, the nose of the external threaded connector has an axial length L10, which satisfies the following condition: 10mm≤L10≤30mm.

[0016] Furthermore, the external threaded connector has an outer cylindrical surface for connecting the sealing arc surface and the external thread, and the internal threaded connector has an inner cylindrical surface for connecting the internal thread and the main sealing cone surface. Part of the internal thread, the inner cylindrical surface, and the outer cylindrical surface together form the first groove.

[0017] Furthermore, the internal threaded joint is provided with an internal connecting surface, which is connected to the side of the auxiliary sealing cone surface that is away from the main sealing cone surface, and part of the sealing arc surface and the internal connecting surface form a second groove.

[0018] Furthermore, the inner connecting surface is a cylindrical surface; or, the inner connecting surface is a conical surface, and the angle between the inner connecting surface and the central axis is between 0° and 3°.

[0019] Furthermore, the shoulder portion includes: a first shoulder surface disposed on an external threaded joint; and a second shoulder surface disposed on an internal threaded joint, wherein the first shoulder surface and the second shoulder surface are interference-fitted when the internal threaded joint and the external threaded joint are screwed together.

[0020] Furthermore, the first shoulder surface and the cross-section of the external threaded joint have an angle α1, which satisfies: 5°≤α1≤15°.

[0021] Furthermore, the second shoulder surface and the cross-section of the internal threaded joint have an angle β3, and the angle β3 and angle α1 satisfy: 0°≤β3-α1≤0.5°.

[0022] Furthermore, along the central axis A, there is an axial distance L20 between the end of the main sealing cone surface near the internal thread and the second shoulder surface. The axial distance L20 and the axial length L21 of the main sealing cone surface satisfy the following condition: 0.1≤L21 / L20≤0.5.

[0023] Furthermore, the nose of the external threaded connector is provided with an inner surface, and the inner surface of the nose has an angle α2 with respect to the central axis, the angle α2 satisfying: 0°≤α2≤10°.

[0024] Applying the technical solution of this invention, on the one hand, compared to the prior art where the inner sealing surface is set as a spherical surface, this invention sets the sealing arc surface on the outer periphery of the external threaded joint. This not only simplifies the processing difficulty but also facilitates quality inspection of the oil-jacket threaded joint during the production stage. Furthermore, both the main sealing cone surface and the auxiliary sealing cone surface are in surface contact with the sealing arc surface, thus increasing the sealing contact area. This allows the sealing arc surface and the composite sealing surface to bear force evenly along the entire contact length, effectively dispersing stress concentration during the tightening process. This not only avoids the problem of poor anti-sticking performance caused by repeated uncoupling operations but also prevents accidental damage to the sealing part, thereby maintaining a long-term stable connection and sealing effect. On the other hand, compared to the poor sealing performance of the sealing structure in the prior art, this invention further improves the sealing performance of the oil-jacket threaded joint when it is subjected to external loads, especially compressive loads and external pressure loads. Specifically, when the external threaded joint and the internal threaded joint are screwed together, a preliminary sealing fit is formed between the main sealing cone surface and the sealing arc surface. When the oil-jacket threaded joint is subjected to further... When subjected to loads under complex operating conditions, the auxiliary sealing cone surface can also participate in the sealing. The auxiliary sealing cone surface and the sealing arc surface form a second seal, greatly increasing the sealing contact area. This composite sealing structure design not only improves the initial sealing performance under no-load conditions, but also, when subjected to external compressive loads and external pressure loads, the sealing cooperation between the main sealing cone surface and the sealing arc surface makes the contact pressure distribution of the sealing part more uniform. This can avoid the problem of sealing failure caused by pressure concentration, thereby enhancing the gas-tightness and pressure resistance of the oil-jacket threaded joint, and thus improving the sealing performance of the oil-jacket threaded joint. At the same time, this multi-position contact sealing method also improves the gas-tightness of the oil-jacket threaded joint, maintaining a good sealing state even under extreme composite loads. Furthermore, the sealing arc surface protrudes radially away from the central axis A of the oil-jacket threaded joint. Since the thickness reduction of the sealing arc surface in the axial direction is less than that of the sealing cone surface, the thickness of the shoulder surface of the sealing arc surface can be larger, thus giving the oil-jacket threaded joint higher compressive strength. Attached Figure Description

[0025] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0026] Figure 1 A schematic diagram of an embodiment of the oil casing threaded joint of the present invention is shown;

[0027] Figure 2 It shows Figure 1 A schematic diagram of the external threaded joint of the oil casing threaded joint;

[0028] Figure 3 It shows Figure 1 A schematic diagram of the internal thread joint of the oil casing threaded connector;

[0029] Figure 4 It shows Figure 2 A partial enlarged view of the external threaded connector;

[0030] Figure 5 It shows Figure 3 A partial enlarged view of an internal threaded joint;

[0031] Figure 6 It shows Figure 3 Another enlarged view of the internal threaded joint;

[0032] Figure 7 It shows Figure 1 A schematic diagram of the point of contact P where the sealing arc surface of the external threaded joint and the main sealing cone surface of the internal threaded joint first come into contact.

[0033] Figure 8 The stress contour plot of a prior art oil-casing threaded joint subjected to maximum compressive load is shown.

[0034] Figure 9 The stress cloud diagram of the oil casing threaded joint of the present invention under the maximum compressive load is shown;

[0035] Figure 10 A comparison diagram of the sealing contact pressure distribution of the prior art and the oil casing threaded joint of the present invention under external pressure and compressive load is shown.

[0036] Figure 11 A comparison diagram of the sealing contact pressure distribution of the oil casing threaded joint of the present invention under external pressure and tensile load is shown.

[0037] The above figures include the following reference numerals:

[0038] 1. External threaded connector; 10. Outer cylindrical surface; 11. Sealing arc surface; 12. First shoulder surface; 13. Cylindrical surface; 14. Nose inner surface; 2. Internal threaded connector; 20. Inner cylindrical surface; 21. Inclined surface; 22. Main sealing cone surface; 23. Auxiliary sealing cone surface; 24. Inner connecting surface; 25. Second shoulder surface; 30. Threaded part; 31. Internal thread; 32. External thread; 40. First groove part; 50. Sealing part; 60. Second groove part; 70. Shoulder part. Detailed Implementation

[0039] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0040] It should be noted that, in the embodiments of the present invention, the external load refers to the multidimensional composite load consisting of tensile load, compressive load, internal pressure load, external pressure load, and bending load acting on the oil casing threaded joint after the internal threaded joint 2 and the external threaded joint 1 are screwed together. Specifically, the external pressure load refers to the pressure acting on the outer surface of the oil casing threaded joint, and the internal pressure load refers to the pressure acting on the inner surface of the oil casing threaded joint. Large tubing mainly bears the external pressure load, while internal tubing mainly bears the internal pressure load. The compressive load is an axial force load caused by thermal expansion due to high downhole temperatures, as well as the axial thrust exerted by human intervention during tubing string downhole operations. This is commonly seen in complex conditions during drilling, completion, and production processes of oil casing. The tensile load refers to the axial tensile force borne by the oil casing threaded joint. During oil extraction, the tensile load is caused by the weight of the tubing itself, the lifting of the oil casing, and cyclic thermal expansion and contraction.

[0041] It should be noted that, in the embodiments of the present invention, the nose end of the external threaded connector 1 refers to the pipe end of the external threaded connector 1.

[0042] It should be noted that in the embodiments of the present invention, axial length refers to the length in the direction of the central axis, and axial distance refers to the distance in the direction of the central axis.

[0043] like Figures 1 to 11As shown, an embodiment of the present invention provides an oil casing threaded joint. The oil casing threaded joint has a central axis A and includes an internal threaded joint 2 and an external threaded joint 1. Along the central axis A, a threaded portion 30, a first groove portion 40, a sealing portion 50, a second groove portion 60, and a shoulder portion 70 are sequentially provided between the internal threaded joint 2 and the external threaded joint 1. The threaded portion 30 includes an external thread 32 provided on the external threaded joint 1 and an internal thread 31 provided on the internal threaded joint 2, which are threadedly connected. The first groove portion 40 and the second groove portion 60 can store thread grease. The sealing portion 50 includes: a sealing arc surface 11, provided on the outer peripheral side of the external threaded joint 1, protruding in a direction away from the central axis A along the radial direction of the oil casing threaded joint; and a composite sealing surface, provided on the inner peripheral side of the internal threaded joint 2, the composite sealing surface including a connected main seal. Conical surface 22 and auxiliary sealing conical surface 23 are arranged sequentially in the direction from the pipe end of the internal threaded joint 2 to the pipe body of the internal threaded joint 2. The distance between the main sealing conical surface 22 and the auxiliary sealing conical surface 23 and the central axis A gradually decreases. The main sealing conical surface 22 has an angle β1 with the central axis A, and the auxiliary sealing conical surface 23 has an angle β2 with the central axis A. Angle β1 is greater than angle β2. When the internal threaded joint 2 and the external threaded joint 1 are screwed together, the main sealing conical surface 22 and the sealing arc surface 11 are sealed together. When the oil casing threaded joint is subjected to compressive load and external pressure load (such as simple compressive load, compression + internal pressure load, compression + external pressure load, external pressure load, external pressure + tensile load, etc.), both the main sealing conical surface 22 and the auxiliary sealing conical surface 23 are sealed together with the sealing arc surface 11.

[0044] In the above technical solution, on the one hand, compared with the prior art where the inner sealing surface is set as a spherical surface, the present invention sets the sealing arc surface 11 on the outer periphery of the external threaded joint 1. This not only simplifies the processing difficulty but also facilitates the quality inspection of the oil sleeve threaded joint during the production stage. Furthermore, both the main sealing cone surface 22 and the auxiliary sealing cone surface 23 are in surface contact with the sealing arc surface 11, which increases the sealing contact area. This allows the sealing arc surface 11 and the composite sealing surface to be evenly stressed along the entire contact length, effectively dispersing stress concentration during the tightening process. This not only avoids stress concentration caused by repeated uncoupling but also... The invention addresses the issue of poor anti-sticking performance caused by operation and prevents accidental damage to the sealing part 50, thus maintaining a long-term stable connection and sealing effect. Furthermore, compared to the poor sealing performance of existing sealing structures, the present invention further improves the sealing performance of the oil-jacket threaded joint under external loads, especially compressive and external pressure loads. Specifically, when the external threaded joint 1 and the internal threaded joint 2 are screwed together, a preliminary sealing fit is formed between the main sealing cone surface 22 and the sealing arc surface 11. Moreover, when the oil-jacket threaded joint is under complex working conditions… When subjected to load, the auxiliary sealing cone surface 23 also participates in the sealing, forming a second seal with the sealing arc surface 11, greatly increasing the sealing contact area. This composite sealing structure design not only improves the initial sealing performance under no-load conditions, but also ensures that both the main sealing cone surface 22 and the auxiliary sealing cone surface 23 seal with the sealing arc surface 11 when subjected to external compressive and external pressure loads. This makes the contact pressure distribution of the sealing part 50 more uniform, avoiding the sealing failure problem that may be caused by pressure concentration, thereby enhancing the gas-tightness of the oil sleeve threaded joint. The robustness and compressive strength of the oil-jacket threaded joint can improve its sealing performance. At the same time, this multi-position contact sealing method also improves the gas tightness of the oil-jacket threaded joint, maintaining a good sealing state even under extreme combined loads. Furthermore, the sealing arc surface 11 protrudes radially away from the central axis A of the oil-jacket threaded joint. Since the thickness of the sealing arc surface 11 is reduced less in the axial direction compared to the sealing cone surface, the thickness of the first shoulder surface 12 of the sealing arc surface 11 can be increased, thereby giving the oil-jacket threaded joint higher compressive strength.

[0045] Furthermore, the first groove 40 and the second groove 60 further optimize the performance of the oil sleeve threaded joint during operation. The first groove 40 and the second groove 60 can not only store excess thread grease to reduce the interference of the high back pressure caused by the thread grease after threading on the sealing performance, but also improve the reliability of the thread sealing performance.

[0046] To achieve 100% compressibility, the oil-jacket threaded joint disclosed in Chinese Patent CN202946041U often requires a pipe end reduction process, which leads to high production and processing costs. Therefore, in this invention, the use of a sealing arc surface 11 allows the first shoulder surface 12 of the oil-jacket threaded joint to have a larger thickness, which is beneficial to enhancing the compressibility of the oil-jacket threaded joint, while also giving the sealing arc surface 11 and the composite sealing surface excellent sealing performance.

[0047] Preferably, in the embodiments of the present invention, after the external threaded connector 1 and the internal threaded connector 2 are screwed together, the sealing arc surface 11 and the main sealing cone surface 22 make interference contact, that is, the sealing arc surface 11 and the main sealing cone surface 22 are sealed together; when the oil casing threaded connector is subjected to compressive load, the main sealing cone surface 22 and the auxiliary sealing cone surface both make interference contact with the sealing arc surface 11, and together form the sealing part 50. In this way, the oil casing threaded connector can have excellent and stable sealing performance under complex working conditions.

[0048] It should be noted that the radial direction of the oil casing threaded joint is perpendicular to the central axis.

[0049] It should be noted that, according to Figure 10 As shown in the diagram, under external pressure and compressive loads, a comparison of the sealing contact pressure distribution of the oil-jacket threaded joint in the prior art and the oil-jacket threaded joint of the present invention reveals that the peak sealing contact pressure of the oil-jacket threaded joint of the present invention is significantly lower than that of the prior art, reducing the probability of fretting wear and seizing. Simultaneously, it can be seen that the sealing contact pressure length of the oil-jacket threaded joint in the prior art is greater than that of the prior art, implying that the present invention has better sealing performance. According to... Figure 11 As shown in the diagram, under external pressure and tensile loads, a comparison of the sealing contact pressure distribution between the existing patented oil-jacket threaded joint and the oil-jacket threaded joint of this invention reveals that the peak sealing contact pressure of the oil-jacket threaded joint of this invention is significantly lower than that of the existing patented oil-jacket threaded joint, reducing the probability of fretting wear and seizing. Simultaneously, it can be seen that the sealing contact pressure length of the existing patented oil-jacket threaded joint is greater, implying that this invention has better sealing performance. Therefore, the sealing performance of the oil-jacket threaded joint of this invention under complex working conditions is superior to that of the existing patented oil-jacket threaded joint.

[0050] like Figure 6 As shown, in the embodiments of the present invention, angles β1 and β2 satisfy: 0.2° < angle β1 - angle β2 < 2°.

[0051] In the above technical solution, by setting the aforementioned angle range, when the internal threaded connector 2 and the external threaded connector 1 are screwed together, and when the oil casing threaded connector is not subjected to external load, the main sealing cone surface 22 can contact the sealing arc surface 11, while avoiding contact between the auxiliary sealing cone surface 23 and the sealing arc surface 11. When the internal threaded connector 2 and the external threaded connector 1 are screwed together, and when the oil casing threaded connector is subjected to external load, the auxiliary sealing cone surface 23 can fully contact the sealing arc surface 11, avoiding the problem of insufficient sealing capacity between the auxiliary sealing cone surface 23 and the sealing arc surface 11, and also avoiding the problem of excessive contact pressure between the composite sealing surface and the sealing arc surface 11. In this way, the problem of fretting damage to the sealing surface can be avoided. Therefore, the aforementioned angle range ensures that the oil casing threaded connector has excellent sealing performance while effectively preventing excessive contact and damage to the sealing surface.

[0052] Preferably, in an embodiment of the present invention, the angle β1-angle β2 is 0.95°.

[0053] like Figure 6 As shown in the embodiments of the present invention, the angle β1 ranges from 4° to 9°. By using the sealing angle within the above range, the oil sleeve threaded joint can achieve excellent sealing distribution and good anti-sticking performance of the sealing surface.

[0054] like Figure 6 As shown, in the embodiments of the present invention, the range of angle β2 is: 3°≤β2≤8°.

[0055] By using the sealing angle within the above range, under the action of compressive load, both the main sealing cone surface 22 and the auxiliary sealing cone surface 23 can come into contact with the sealing arc surface 11, thereby jointly forming the sealing part 50. In this way, the sealing performance of the oil sleeve threaded joint under complex working conditions can have excellent stability.

[0056] like Figure 5 and Figure 6 As shown, in the embodiment of the present invention, the axial length L21 of the main sealing cone surface 22 is in the range of 2.5mm≤L21≤4mm.

[0057] In the above technical solution, the selection of the range of L21 can enable the main sealing cone surface 22 to effectively disperse stress when bearing external composite loads, avoiding stress concentration at a certain point and damage to the seal. When bearing compressive loads or external pressure loads, the main sealing cone surface 22 with a suitable length can form a more uniform contact pressure distribution with the sealing arc surface 11 of the external threaded joint 1, ensuring that even under harsh working conditions, the sealing part 50 can maintain its sealing ability and structural integrity under high pressure.

[0058] like Figure 5 and Figure 6As shown, in the embodiment of the present invention, the axial length L22 of the auxiliary sealing cone surface 23 is in the range of 1mm≤L22≤2.5mm.

[0059] In the above technical solution, the specific range of L22 can optimize the stress distribution of the oil-jacket threaded joint under combined loads, effectively avoiding seal failure caused by stress concentration. When the oil-jacket threaded joint operates under complex conditions, the combined contact between the auxiliary sealing cone surface 23 and the sealing arc surface 11 not only increases the overall sealing contact area but also allows the contact pressure to be evenly distributed over a wider range, thereby greatly reducing the risk of damage to a single sealing surface due to excessive pressure and enhancing the joint's resistance to combined loads.

[0060] like Figure 4 As shown, in the embodiments of the present invention, the radius R10 of the sealing arc surface 11 is in the range of 200mm≤R10≤500mm. Preferably, the sealing arc surface 11 is a circular arc surface.

[0061] With the above configuration, the first shoulder surface 12 of the external threaded connector 1 can have a larger thickness, which is beneficial to enhancing the compression resistance of the oil-jacket threaded connector (for example, under the maximum compressive load, the oil-jacket threaded connector of the present invention...). Figure 9 The compressive strength of the stress cloud diagram shown is significantly better than that of existing oil casing threaded joints. Figure 8 (as shown in the stress cloud diagram). At the same time, setting the arc radius R10 to the above range can increase the sealing contact area between the sealing arc surface 11 and the composite sealing surface, thereby giving the sealing part 50 excellent anti-sticking performance.

[0062] like Figure 4 As shown in the embodiment of the present invention, the nose of the external threaded connector 1 has an axial length L10, the sealing arc surface 11 has an axial length L11, and the ratio of the axial length L11 to the axial length L10 satisfies: 0.3≤L11 / L10≤0.9.

[0063] The above settings can improve the rigidity of the sealing part 50 of the oil jacket threaded joint, thereby improving the sealing stability.

[0064] like Figure 7 As shown in the embodiment of the present invention, when the external threaded connector 1 and the internal threaded connector 2 are screwed together, the sealing arc surface 11 and the main sealing cone surface 22 first make contact at the initial contact tangent point P. There is an axial distance L30 between the tangent point P and the external thread 32. The nose end of the external threaded connector 1 has an axial length L10. The ratio of the axial distance L30 to the axial length L10 satisfies: 0.56≤L30 / L10≤0.86.

[0065] By controlling the position of the tangent point P and the ratio of L30 / L10, it can be ensured that the sealing arc surface 11 and the main sealing cone surface 22 can quickly establish a smooth and stable contact in the initial stage of screwing. Furthermore, by reasonably setting the position of the tangent point P, excessive wear or unstable contact of the sealing surface due to premature or late contact can be avoided, thereby extending the service life of the threaded joint and reducing the maintenance and replacement costs caused by threaded joint failure.

[0066] It should be noted that, as Figure 7 As shown in the embodiment of the present invention, the tangent point P is located at the foremost position where the sealing arc surface 11 intersects with the main sealing cone surface 22 during the tightening process of the external threaded connector 1 and the internal threaded connector 2, that is, the point where the sealing arc surface 11 and the main sealing cone surface 22 first come into contact during the tightening process of the external threaded connector 1 and the internal threaded connector 2.

[0067] It should be noted that, as Figure 7 As shown, in the embodiment of the present invention, the axial distance L30 refers to the distance between the end of the external thread 32 facing the sealing arc surface 11 and the tangent point P in the direction of the central axis A, that is, the distance between the starting position of the external thread 32 and the tangent point P.

[0068] like Figure 4 and Figure 7 As shown in the embodiment of the present invention, based on the different specifications of the oil casing threaded joint, the nose of the external threaded joint 1 has an axial length L10, and the axial length L10 satisfies: 10mm≤L10≤30mm.

[0069] The above settings allow for a better balance between connection strength and sealing performance in the oil casing threaded joint.

[0070] like Figure 1 , Figure 4 and Figure 5 As shown in the embodiment of the present invention, the external threaded connector 1 is provided with an outer cylindrical surface 10 for connecting the sealing arc surface 11 and the external thread 32, and the internal threaded connector 2 is provided with an inner cylindrical surface 20 for connecting the internal thread 31 and the main sealing cone surface 22. A portion of the internal thread 31, the inner cylindrical surface 20, and the outer cylindrical surface 10 together form a first groove portion 40. In this way, the first groove portion 40 can store excess thread grease, thereby preventing thread grease pressure from affecting the sealing performance.

[0071] like Figure 1 , Figure 4 and Figure 5As shown in the embodiment of the present invention, the internal threaded connector 2 is provided with an internal connecting surface 24, which is connected to the side of the auxiliary sealing cone surface 23 opposite to the main sealing cone surface 22. A portion of the sealing arc surface 11 and the internal connecting surface 24 form a second groove portion 60. In this way, the second groove portion 60 can store excess thread grease, thereby avoiding the impact of thread grease pressure on the sealing performance.

[0072] It should be noted that the first groove 40 and the second groove 60 are formed by the mating of the internal threaded connector 2 and the external threaded connector 1. They can store excess thread grease applied during well operations and reduce the impact of thread grease pressure on the performance of the oil casing threaded connector. In this way, there is no need to specially process the groove structure on the external threaded connector 1 or the internal threaded connector 2, which improves processing efficiency.

[0073] Specifically, such as Figure 5 As shown in the embodiment of the present invention, the internal threaded connector 2 is provided with an inclined surface 21 for connecting the inner cylindrical surface 20 and the main sealing cone surface 22, and an arc R20 is provided between the inclined surface 21 and the inner cylindrical surface 20, so that the transition connection between the inner cylindrical surface 20 and the main sealing cone surface 22 can be realized.

[0074] Preferably, such as Figure 5 As shown, in an embodiment of the present invention, the inner connecting surface 24 is a cylindrical surface.

[0075] In one embodiment, the inner connecting surface 24 is a conical surface, and the angle between the inner connecting surface 24 and the central axis A is between 0° and 3°. By setting the angle within the above range, the second groove portion 60 of the oil sleeve threaded joint can better accommodate excessive thread grease, while avoiding affecting the contact of adjacent sealing surfaces (sealing arc surface 11 and composite sealing surface).

[0076] like Figure 1 , Figure 4 and Figure 5 As shown, in an embodiment of the present invention, the shoulder portion 70 includes: a first shoulder surface 12 disposed on the external threaded joint 1; and a second shoulder surface 25 disposed on the internal threaded joint 2. When the internal threaded joint 2 and the external threaded joint 1 are screwed together, the first shoulder surface 12 and the second shoulder surface 25 are interference-fitted.

[0077] Through the above configuration, the interference fit between the first shoulder surface 12 and the second shoulder surface 25 forms the shoulder portion 70. This serves to provide screw-in positioning and compression resistance, preventing uncertain screw-in positions of the oil casing threaded joint and preventing structural damage under extreme conditions of high compression, thereby maintaining the connection strength and overall structural stability of the oil casing threaded joint. When the internal threaded joint 2 and the external threaded joint 1 are screwed into their final positions, the interference contact between the first shoulder surface 12 and the second shoulder surface 25 causes the sealing arc surface 11 to form a tighter sealing contact with the main sealing cone surface 22 and the auxiliary sealing cone surface 23. This tight contact mechanism, especially the interference fit, greatly improves the robustness and reliability of the seal, maintaining an effective sealing effect even under high-pressure gas or liquid media.

[0078] Furthermore, the interference fit between the first shoulder surface 12 and the second shoulder surface 25 of the shoulder portion 70 provides a clear termination mark for the tightening operation of the threaded joint. The operator can judge whether the tightening has reached the ideal state by feeling the obvious damping when the first shoulder surface 12 contacts the second shoulder surface 25, thereby avoiding over-tightening or under-tightening, improving the accuracy and convenience of on-site operation, and also reducing damage to the threaded joint caused by improper operation.

[0079] like Figure 4 As shown, in an embodiment of the present invention, there is an angle α1 between the first shoulder surface 12 and the cross-section of the external threaded connector 1, and the angle α1 satisfies: 5°≤α1≤15°.

[0080] With the above settings, after the first shoulder surface 12 and the second shoulder surface 25 are in interference contact, the first shoulder surface 12 can be subjected to more uniform force, thereby giving the oil sleeve threaded joint good compression performance.

[0081] It should be noted that, in the embodiments of the present invention, the cross-section of the external threaded connector 1 is perpendicular to the central axis A.

[0082] Specifically, in an embodiment of the present invention, a transition arc R11 is provided between the first shoulder surface 12 and the sealing arc surface 11, and the value range of the transition arc R11 satisfies: 0.6mm≤R11≤2.0 mm.

[0083] like Figures 4 to 6 As shown, in an embodiment of the present invention, there is an angle β3 between the cross-section of the second shoulder surface 25 and the internal threaded connector 2, and the angle β3 and the angle α1 satisfy: 0°≤β3-α1≤0.5°.

[0084] The above settings can compensate for the increased interference on the shoulder surface near R11 caused by the necking of the pipe end of the external threaded connector 1, and also compensate for the reduced interference on the shoulder surface away from R11 caused by the necking of the pipe end of the external threaded connector 1. In this way, the first shoulder surface 12 and the second shoulder surface 25 can be subjected to force contact more evenly, thereby giving the oil sleeve threaded connector good compression performance.

[0085] It should be noted that, in the embodiments of the present invention, the cross-section of the internal threaded connector 2 is perpendicular to the central axis A.

[0086] like Figure 6 As shown, in an embodiment of the present invention, along the central axis A, there is an axial distance L20 between the end of the main sealing cone surface 22 near the internal thread 31 and the second shoulder surface 25. The axial distance L20 and the axial length L21 of the main sealing cone surface 22 satisfy: 0.1≤L21 / L20≤0.5.

[0087] With the above settings, the sealing part 50 of the oil-jacket threaded joint can be moved away from the shoulder 70, and the rigidity of the sealing part 50 is improved. This effectively avoids the sealing part 50 (sealing arc surface 11 and composite sealing surface sealing contact) being affected by the stress state of the shoulder 70 when it is in a sealing contact state. As a result, the oil-jacket threaded joint can have excellent stability and compression performance in sealing under complex working conditions.

[0088] like Figure 4 As shown, in an embodiment of the present invention, the nose end of the external threaded connector 1 is provided with a nose end inner surface 14, and the nose end inner surface 14 and the central axis A have an angle α2, which satisfies: 0°≤α2≤10°.

[0089] With the above settings, the nose of the external threaded connector 1 can be more easily deformed, that is, the axial stiffness of the nose of the external threaded connector 1 is reduced. In this way, the compression performance of the oil sleeve threaded connector is improved, and at the same time, it is conducive to the uniform circumferential contact deformation of the sealing part 50, so that the sealing contact pressure is evenly distributed in the circumferential direction.

[0090] In one embodiment, when α2 = 0°, that is, the inner surface of the nose tip simultaneously has a cylindrical surface 13 ( Figure 4 The cylindrical surface 13 (shown by the dashed line) and the inner surface 14 (shown by the conical tip) are shown by the dashed line.

[0091] In one embodiment, when α2 = 8°, the axial stiffness of the nose tip is reduced while the stiffness of the sealing surface is increased.

[0092] It should be noted that the present invention provides an oil casing threaded joint with excellent compression performance and robust gas sealing performance. The threaded joint still has good structural integrity and sealing integrity under various complex and harsh load conditions, especially with excellent sealing performance under external pressure combined conditions. It is suitable for oil and gas wells with complex geological conditions such as high temperature, high pressure, and ultra-deep conditions, and is mainly used in well conditions with demanding requirements for gas sealing and compression performance.

[0093] Preferably, the embodiment of the present invention uses a 196.85mm × 12.7mm casing with a steel grade of 140V. The geometric parameters of the oil casing threaded joint are as follows: pitch P = 5 threads / inch, thread taper 1:16, L10 = 21mm, L30 / L10 = 0.57, L11 / L10 = 0.60, R10 = 250, α1 = 8°, α2 = 8°, L21 = 3.5 mm, L22 = 1.6 mm, β3 - α1 = 0.3°, L21 / L20 = 0.24. The connection strength of this oil casing threaded joint can reach 7094kN, the compressive strength can reach 7094kN, the gas sealing performance can reach over 109.1Mpa, the external pressure resistance can reach over 85.8Mpa, the bending resistance can reach over 20° / 30 meters, and it meets the requirement of non-sticking after three sets of uncoupling. Meanwhile, the oil casing threaded joint has good operability in terms of threading and insertion, and has robust sealing performance.

[0094] From the above description, it can be seen that the embodiments of the present invention achieve the following technical effects: On the one hand, compared with the prior art where the inner sealing surface is set as a spherical surface, the present invention sets the sealing arc surface on the outer periphery of the external threaded joint. This not only simplifies the processing difficulty but also facilitates the quality inspection of the oil casing threaded joint during the production stage. Furthermore, both the main sealing cone surface and the auxiliary sealing cone surface are in surface contact with the sealing arc surface, which increases the sealing contact area. This allows the sealing arc surface and the composite sealing surface to be evenly stressed along the entire contact length, effectively dispersing stress concentration during the tightening process. This not only avoids the problem of poor anti-sticking performance caused by repeated uncoupling operations but also prevents accidental damage to the sealing part, thus maintaining a long-term stable connection and sealing effect. On the other hand, compared with the poor sealing performance of the sealing structure in the prior art, the present invention further improves the sealing performance when the oil casing threaded joint is subjected to external loads, especially compressive loads and external pressure loads. Specifically, when the external threaded joint and the internal threaded joint are screwed together, a preliminary sealing fit is formed between the main sealing cone surface and the sealing arc surface. When the oil-jacket threaded joint is subjected to loads under complex working conditions, the auxiliary sealing cone surface can also participate in the sealing. The auxiliary sealing cone surface and the sealing arc surface form a second seal, which greatly increases the sealing contact area. This composite sealing structure design not only improves the initial sealing performance under no-load conditions, but also, when subjected to external compressive loads and external pressure loads, the sealing cooperation between the main sealing cone surface and the sealing arc surface makes the contact pressure distribution of the sealing part more uniform. This can avoid the problem of sealing failure caused by pressure concentration, thereby enhancing the gas-tightness and pressure resistance of the oil-jacket threaded joint, and thus improving the sealing performance of the oil-jacket threaded joint. At the same time, this multi-position contact sealing method also improves the gas-tightness of the oil-jacket threaded joint, and can maintain a good sealing state even under extreme composite loads. Furthermore, the sealing arc surface protrudes radially away from the central axis A of the oil-jacket threaded joint. Since the thickness reduction of the sealing arc surface in the axial direction is less than that of the sealing cone surface, the thickness of the shoulder surface of the sealing arc surface can be larger, thus giving the oil-jacket threaded joint higher compressive strength.

[0095] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A threaded joint for an oil sleeve, characterized in that, The oil casing threaded joint has a central axis (A). The oil casing threaded joint includes an internal threaded joint (2) and an external threaded joint (1). Along the central axis (A), the internal threaded joint (2) and the external threaded joint (1) are sequentially provided with a threaded portion (30), a first groove portion (40), a sealing portion (50), a second groove portion (60), and a shoulder portion (70). The threaded portion (30) includes an external thread (32) provided on the external threaded joint (1) and an internal thread (31) provided on the internal threaded joint (2). The internal thread (31) and the external thread (32) are threadedly connected. The first groove portion (40) and the second groove portion (60) can store thread grease. The sealing part (50) includes: A sealing arc surface (11) is provided on the outer periphery of the external threaded joint (1). Along the radial direction of the oil sleeve threaded joint, the sealing arc surface (11) protrudes in a direction away from the central axis (A). A composite sealing surface is provided on the inner circumference of the internal threaded joint (2). The composite sealing surface includes a main sealing cone surface (22) and an auxiliary sealing cone surface (23) connected to each other. In the direction from the pipe end of the internal threaded joint (2) to the pipe body of the internal threaded joint (2), the main sealing cone surface (22) and the auxiliary sealing cone surface (23) are arranged sequentially, and the distance between the main sealing cone surface (22) and the auxiliary sealing cone surface (23) and the central axis (A) gradually decreases. The distance between the main sealing cone surface (22) and the auxiliary sealing cone surface (23) is... An angle β1 exists between the central axis (A) and the auxiliary sealing cone (23) exists between the central axis (A) and the auxiliary sealing cone (23). Angle β1 is greater than angle β2. When the internal threaded joint (2) and the external threaded joint (1) are screwed together, the main sealing cone (22) and the sealing arc surface (11) are sealed together. When the oil casing threaded joint is subjected to external load, both the main sealing cone (22) and the auxiliary sealing cone (23) are sealed together with the sealing arc surface (11).

2. The oil casing threaded joint according to claim 1, characterized in that, The angles β1 and β2 satisfy the following condition: 0.2° < angle β1 - angle β2 < 2°.

3. The oil casing threaded joint according to claim 2, characterized in that, The angle β1 ranges from: 4° ≤ β1 ≤ 9°; and / or, The range of angle β2 is: 3°≤β2≤8°.

4. The oil casing threaded joint according to claim 1, characterized in that, The axial length L21 of the main sealing cone surface (22) is in the range of: 2.5mm ≤ L21 ≤ 4mm; and / or, The axial length L22 of the auxiliary sealing cone surface (23) is in the range of 1mm≤L22≤2.5mm.

5. The oil casing threaded joint according to claim 1, characterized in that, The radius R10 of the sealing arc surface (11) is in the range of 200mm≤R10≤500mm.

6. The oil casing threaded joint according to any one of claims 1 to 5, characterized in that, The nose of the external threaded connector (1) has an axial length L10, and the sealing arc surface (11) has an axial length L11. The ratio of the axial length L11 to the axial length L10 satisfies: 0.3≤L11 / L10≤0.

9.

7. The oil casing threaded joint according to any one of claims 1 to 5, characterized in that, When the external threaded connector (1) and the internal threaded connector (2) are screwed together, the sealing arc surface (11) and the main sealing cone surface (22) first make contact at the initial contact tangent point P. The tangent point P and the external thread (32) have an axial distance L30. The nose of the external threaded connector (1) has an axial length L10. The ratio of the axial distance L30 and the axial length L10 satisfies: 0.56≤L30 / L10≤0.

86.

8. The oil casing threaded joint according to any one of claims 1 to 5, characterized in that, The nose of the external threaded connector (1) has an axial length L10, which satisfies the following condition: 10mm≤L10≤30mm.

9. The oil casing threaded joint according to any one of claims 1 to 5, characterized in that, The external threaded connector (1) is provided with an outer cylindrical surface (10) for connecting the sealing arc surface (11) and the external thread (32), and the internal threaded connector (2) is provided with an inner cylindrical surface (20) for connecting the internal thread (31) and the main sealing cone surface (22). Part of the internal thread (31), the inner cylindrical surface (20), and the outer cylindrical surface (10) together form the first groove portion (40).

10. The oil casing threaded joint according to any one of claims 1 to 5, characterized in that, The internal threaded connector (2) is provided with an internal connecting surface (24), which is connected to the side of the auxiliary sealing cone surface (23) away from the main sealing cone surface (22). Part of the sealing arc surface (11) and the internal connecting surface (24) form the second groove (60).

11. The oil casing threaded joint according to claim 10, characterized in that, The inner connecting surface (24) is a cylindrical surface; or the inner connecting surface (24) is a conical surface, and the angle between the inner connecting surface (24) and the central axis (A) is between 0° and 3°.

12. The oil casing threaded joint according to any one of claims 1 to 5, characterized in that, The shoulder portion (70) includes: The first shoulder surface (12) is provided on the external threaded joint (1); The second shoulder surface (25) is provided on the internal threaded joint (2). When the internal threaded joint (2) and the external threaded joint (1) are screwed together, the first shoulder surface (12) and the second shoulder surface (25) are interference fit.

13. The oil casing threaded joint according to claim 12, characterized in that, The first shoulder surface (12) and the cross section of the external threaded joint (1) have an angle α1, which satisfies: 5°≤α1≤15°.

14. The oil casing threaded joint according to claim 13, characterized in that, The second shoulder surface (25) and the cross section of the internal threaded connector (2) have an angle β3, and the angle β3 and the angle α1 satisfy: 0°≤β3-α1≤0.5°.

15. The oil casing threaded joint according to claim 13, characterized in that, Along the central axis (A), the end of the main sealing cone (22) near the internal thread (31) has an axial distance L20 with the second shoulder surface (25), and the axial distance L20 and the axial length L21 of the main sealing cone (22) satisfy: 0.1≤L21 / L20≤0.

5.

16. The oil casing threaded joint according to any one of claims 1 to 5, characterized in that, The nose end of the external threaded connector (1) is provided with a nose end inner surface (14), and the nose end inner surface (14) and the central axis (A) have an angle α2, which satisfies: 0°≤α2≤10°.

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