Threaded joint for oil casing

Abstract

The utility model provides an oil casing pipe screwed joint. An outer sealing part, a first-stage thread part, a torque bearing part, a second-stage thread part and an inner sealing part are sequentially arranged between the external thread connector and the internal thread connector from the outer side to the inner side, the internal thread connector is connected with the external thread connector through the first-stage thread part and the second-stage thread part, and the torque bearing part is used for bearing part of torque and achieving positioning; the outer sealing part comprises a first outer conical surface and a second outer conical surface which are correspondingly arranged on the internal thread joint and the external thread joint respectively, and the first outer conical surface and the second outer conical surface are in sealing fit; the inner sealing part comprises a first inner conical surface and a second inner conical surface which are correspondingly arranged on the inner threaded connector and the outer threaded connector respectively, and the first inner conical surface and the second inner conical surface are in sealing fit. According to the technical scheme, the problem that fluid inside and outside an oil sleeve is difficult to seal at the same time through an oil sleeve threaded connector in the prior art is solved, and the oil pipe threaded connector further has the advantages of being high in torsion resistance and not prone to thread gluing.

Description

Technical Field

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

[0002] Oil pipes generally include oil pipes and casings. The outer diameter of the oil pipe is generally less than 114.3mm, and the outer diameter of the casing is generally greater than 114.3mm but less than 508mm. In the process of oil and natural gas extraction, hundreds of oil pipes and casings are connected by threaded joints to form a pipe string that is thousands of meters long. The pipe string is subjected to very complex loads, including internal pressure, external pressure, tension, bending, torsion and temperature loads. The joint is the weakest link in the entire pipe string, and it is easy to cause joint breakage and leakage failure.

[0003] At present, most of the joints used in oil casing are API joints. API joints are joints that are processed and manufactured according to API (American Petroleum Institute) standards. Its disadvantages are: there is no metal / metal sealing structure, and it only relies on the interference fit of the thread to achieve sealing, which has poor sealing performance, especially the air sealing performance. Secondly, the torsion resistance is not good, and the thread often fails due to sticking, which cannot meet the requirements of multiple loading and unloading.

[0004] The inventor found through searching the prior art documents that the Chinese patent publication number is CN2731065Y, the publication date is October 5, 2005, and the utility model patent name is "gas-sealed casing threaded joint", which improves the API thread structure. Among them, the structure includes an internal thread joint, a coupling, a thread, a cutter groove or transition zone, a sealing surface, a transition surface of the internal thread joint shoulder, a shoulder surface and other parts. The internal thread joint is provided with a coupling, and a sealing structure of a cone face to a cone face is adopted, and the taper of the sealing part is the same, the length of the sealing part is at least 5mm, and the radial interference is greater than 0.20mm. There are a cutter groove or transition zone, a sealing surface, a transition surface of the internal thread joint shoulder, and a shoulder surface between the internal thread joint and the coupling. The external thread adopts a three-stage taper structure, the taper of the thread part in the diameter direction is 1 / 16, the taper of the sealing part is within the range of 1 / 12 to 1 / 6, the taper of the end is 1 / 5 to 1 / 3, and the tapers are transitioned by arcs. The internal thread adopts a two-stage or three-stage taper structure, and the taper size is the same as the corresponding external thread. The thread part and the sealing part adopt a cylindrical transition. The joint adds a main sealing structure and a secondary sealing structure, so the sealing performance is enhanced.

[0005] Compared with API joints, the above patent has a metal / metal sealing structure designed to block the leakage channels at the top and bottom of the teeth of the male and female threads after tightening, so it can play a sealing role. However, since the sealing structure of this joint is located close to the inner wall of the pipe, it is effective in sealing the fluid medium in the pipe column, but the external fluid medium can easily enter the thread, making it difficult to achieve the effect of sealing the fluid inside and outside the casing at the same time. Secondly, the torque of the joint is mainly borne by the torque shoulder, but the torque shoulder is too close to the sealing surface. If the shoulder is over-torqued, it is easy to damage the metal / metal seal, resulting in seal failure. Utility Model Content

[0006] The main purpose of the utility model is to provide an oil casing threaded joint to solve the problem that the oil casing threaded joint in the prior art is difficult to achieve simultaneous sealing of the fluid inside and outside the oil casing, and the threaded joint also has the characteristics of strong torsion resistance and not prone to galling.

[0007] In order to achieve the above-mentioned purpose, the utility model provides an oil casing threaded joint, including: an internal threaded joint; an external threaded joint connected to the internal threaded joint, along the axial direction of the oil casing threaded joint, an external sealing part, a first-level threaded part, a torque bearing part, a second-level threaded part and an internal sealing part are arranged in sequence from the outside to the inside between the external threaded joint and the internal threaded joint, the internal threaded joint is connected to the external threaded joint through the first-level threaded part and the second-level threaded part, and the torque bearing part is used to bear part of the torque and achieve positioning; the external sealing part includes a first outer conical surface and a second outer conical surface respectively corresponding to the internal threaded joint and the external threaded joint, and the first outer conical surface and the second outer conical surface are sealed together; the internal sealing part includes a first inner conical surface and a second inner conical surface respectively corresponding to the internal threaded joint and the external threaded joint, and the first inner conical surface and the second inner conical surface are sealed together.

[0008] Furthermore, there is a contact width A between the first outer conical surface and the second outer conical surface, and the contact width A satisfies the following relationship: 2.5mm≤A≤3.5mm; and / or, there is a contact width B between the first inner conical surface and the second inner conical surface, and the contact width B satisfies the following relationship: 2.5mm≤B≤3.5mm.

[0009] Further, the first outer conical surface and the second outer conical surface are interference fit, and along the radial direction of the oil casing threaded joint, the interference amount between the first outer conical surface and the second outer conical surface is greater than or equal to 0.12 mm and less than or equal to 0.22 mm; and / or, the first inner conical surface and the second inner conical surface are interference fit, and along the radial direction of the oil casing threaded joint, the interference amount between the first inner conical surface and the second inner conical surface is greater than or equal to 0.12 mm and less than or equal to 0.22 mm.

[0010] Further, an angle ɑ is provided between the first outer conical surface and the axis of the oil casing threaded joint, and an angle ɑ is provided between the second outer conical surface and the axis of the oil casing threaded joint, and the angle ɑ satisfies the following formula: 10°≤ɑ≤14°; and / or an angle β is provided between the first inner conical surface and the axis of the oil casing threaded joint, and an angle β satisfies the following formula: 10°≤β≤14°.

[0011] Furthermore, the torque bearing portion includes a first shoulder and a second shoulder which are arranged in sequence along the axial direction of the oil casing threaded joint, the first shoulder is arranged on the internal threaded joint, the second shoulder is arranged on the external threaded joint, the second shoulder is provided with an arc-shaped recessed portion, the first shoulder is provided with an arc-shaped convex portion, and the arc-shaped recessed portion cooperates with the arc-shaped convex portion.

[0012] Further, the arc-shaped concave portion and the arc-shaped convex portion both have an arc radius R, and the arc radius R satisfies the following formula: 1.5 mm≤R≤2.0 mm.

[0013] Further, along the radial direction of the oil casing threaded joint, the first shoulder has a width H2, the second shoulder has a width H1, and the width H1 and the width H2 are both greater than 2.5 mm.

[0014] Furthermore, an internal shoulder is provided on the internal threaded joint, and a shoulder surface is provided on the side of the internal shoulder facing the external threaded joint along the axial direction of the oil casing threaded joint. A gap δ is provided between the end face of the external threaded joint and the shoulder surface, and the gap δ satisfies the following formula: 0.15mm≤δ≤0.5mm.

[0015] Further, the first-level threaded portion includes a first internal thread and a first external thread that are meshed together, the first internal thread is arranged in the internal thread joint, the first external thread is arranged in the external thread joint, and there is a storage gap between the first internal thread and the first external thread, and the storage gap is greater than or equal to 0.1mm and less than or equal to 0.15mm; and / or, the second-level threaded portion includes a second internal thread and a second external thread that are meshed together, the second internal thread is arranged in the internal thread joint, the second external thread is arranged in the external thread joint, and there is a storage gap between the second internal thread and the second external thread, and the storage gap is greater than or equal to 0.1mm and less than or equal to 0.15mm.

[0016] Further, the oil casing threaded joint also includes an outer transition portion for connecting the outer sealing portion and the first-level threaded portion, the outer transition portion includes a first outer cylindrical surface arranged on the internal threaded joint and a second outer cylindrical surface arranged on the external threaded joint, and along the radial direction of the oil casing threaded joint, there is a storage gap between the first outer cylindrical surface and the second outer cylindrical surface, and the storage gap is greater than or equal to 0.1mm and less than or equal to 0.15mm; and / or, the oil casing threaded joint also includes an inner transition portion for connecting the inner sealing portion and the second-level threaded portion, the inner transition portion includes a first inner cylindrical surface arranged on the internal threaded joint and a second inner cylindrical surface arranged on the external threaded joint, and along the radial direction of the oil casing threaded joint, there is a storage gap between the first inner cylindrical surface and the second inner cylindrical surface, and the storage gap is greater than or equal to 0.1mm and less than or equal to 0.15mm.

[0017] By applying the technical solution of the utility model, on the one hand, by setting an outer sealing part, the fluid medium outside the oil casing can be prevented from entering the first-stage threaded part, the torque bearing part and the second-stage threaded part, and by setting an inner sealing part, the fluid medium inside the oil casing can be prevented from entering the second-stage threaded part, the torque bearing part and the first-stage threaded part, and the outer sealing part and the inner sealing part are arranged at intervals along the axial direction of the oil casing threaded joint, so that the inner sealing part and the outer sealing part can be arranged independently of each other, so that the inner sealing part and the outer sealing part can respectively and simultaneously seal the internal and external fluid media of the oil casing to improve the sealing effect of the threaded joint; on the other hand, compared with the poor torsion resistance of the API joint in the prior art, which leads to frequent sticking failure of the thread and is difficult to meet the requirements of multiple mounting and dismounting, in this embodiment, by additionally setting a torque bearing part, part of the torque can be borne, thereby reducing the probability of frequent sticking failure of the thread, and the torque bearing part is located between the first-stage threaded part and the second-stage threaded part, which can avoid damage to the sealing surface, thereby avoiding sealing failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0019] Figure 1 A structural schematic diagram of an embodiment of an oil casing threaded joint of the utility model is shown;

[0020] Figure 2 Shows Figure 1 A partial enlarged view of the D part of the oil casing threaded joint;

[0021] Figure 3 Shows Figure 1 A partial enlarged view of the E part of the oil casing threaded joint;

[0022] Figure 4 Shows Figure 1 A partial enlarged view of location C of the oil casing threaded joint.

[0023] The above drawings include the following reference numerals:

[0024] 1. External thread joint; 2. Second external cone surface; 3. Second external cylindrical surface; 4. First external thread; 5. Second shoulder; 6. Second external thread; 7. Second internal cylindrical surface; 8. Second internal cone surface; 9. End face; 10. First external cone surface; 11. First external cylindrical surface; 12. First internal thread; 13. First shoulder; 14. Second internal thread; 15. First internal cylindrical surface; 16. First internal cone surface; 17. Internal shoulder; 18. Internal thread joint. DETAILED DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present utility model will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0026] like Figures 1 to 4 As shown, an embodiment of the utility model provides an oil casing threaded joint. The oil casing threaded joint includes an internal threaded joint 18 and an external threaded joint 1. Among them, the external threaded joint 1 is connected to the internal threaded joint 18, and along the axial direction of the oil casing threaded joint, an outer sealing part, a first-level threaded part, a torque bearing part, a second-level threaded part and an inner sealing part are sequentially arranged between the external threaded joint 1 and the internal threaded joint 18 from the outside to the inside. The internal threaded joint 18 is connected to the external threaded joint 1 through the first-level threaded part and the second-level threaded part, and the torque bearing part is used to bear part of the torque and achieve positioning; the external sealing part includes a first outer conical surface 10 and a second outer conical surface 2 respectively arranged on the internal threaded joint 18 and the external threaded joint 1, and the first outer conical surface 10 and the second outer conical surface 2 are sealed together; the internal sealing part includes a first inner conical surface 16 and a second inner conical surface 8 respectively arranged on the internal threaded joint 18 and the external threaded joint 1, and the first inner conical surface 16 and the second inner conical surface 8 are sealed together.

[0027] In the above technical scheme, on the one hand, by setting the outer sealing part, the fluid medium outside the oil casing can be prevented from entering the first-stage threaded part, the torque bearing part and the second-stage threaded part, and by setting the inner sealing part, the fluid medium inside the oil casing can be prevented from entering the second-stage threaded part, the torque bearing part and the first-stage threaded part, and the outer sealing part and the inner sealing part are arranged at intervals along the axial direction of the oil casing threaded joint, so that the inner sealing part and the outer sealing part can be arranged independently of each other, so that the inner sealing part and the outer sealing part can respectively and simultaneously seal the internal and external fluid media of the oil casing to improve the sealing effect of the threaded joint; on the other hand, compared with the poor torsion resistance of the API joint in the prior art, which leads to frequent sticking failure of the thread and is difficult to meet the requirements of multiple mounting and dismounting, in this embodiment, by additionally setting the torque bearing part, part of the torque can be borne, thereby reducing the probability of frequent sticking failure of the thread, and the torque bearing part is located between the first-stage threaded part and the second-stage threaded part, which can avoid damage to the sealing surface, thereby avoiding sealing failure.

[0028] It should be noted that in the embodiments of the present invention, the outside refers to the outside of the oil casing threaded joint, and the inside refers to the inside of the oil casing threaded joint; along the axis direction of the oil casing threaded joint, from the outside to the inside refers to Figure 1 The direction from left to right.

[0029] Specifically, in the embodiment of the utility model, the oil casing threaded joint is made of metal material.

[0030] Specifically, in the embodiment of the utility model, the external threaded joint 1 and the internal threaded joint 18 are connected to the two ends of the oil casing by friction welding, and can also be formed by directly upsetting the ends of the casing. The external threaded joint 1 and the internal threaded joint 18 cooperate with each other and are tightened together.

[0031] like Figure 3 and Figure 4 As shown, in an embodiment of the utility model, there is a contact width A between the first outer cone surface 10 and the second outer cone surface 2, and the contact width A satisfies the following relationship: 2.5mm≤A≤3.5mm; and / or, there is a contact width B between the first inner cone surface 16 and the second inner cone surface 8, and the contact width B satisfies the following relationship: 2.5mm≤B≤3.5mm.

[0032] In the above technical solution, by controlling the contact width A, the contact stress distribution between the first outer conical surface 10 and the second outer conical surface 2 can be improved, so that the oil casing threaded joint can seal the fluid medium outside the oil casing; by controlling the contact width B, the contact stress distribution between the first inner conical surface 16 and the second inner conical surface 8 can be improved, so that the oil casing threaded joint can seal the fluid medium inside the oil casing.

[0033] Preferably, in an embodiment of the present invention, the contact width A and the contact width B are equal.

[0034] It should be noted that in the embodiment of the present invention, the contact width A refers to the contact width between the first outer conical surface 10 and the second outer conical surface 2 in the axial direction of the threaded joint; similarly, the contact width B refers to the contact width between the first inner conical surface 16 and the second inner conical surface 8 in the axial direction of the threaded joint.

[0035] like Figure 3 and Figure 4 As shown, in the embodiment of the utility model, the first outer conical surface 10 and the second outer conical surface 2 are interference fit, and along the radial direction of the oil casing threaded joint, the interference between the first outer conical surface 10 and the second outer conical surface 2 is greater than or equal to 0.12mm, and less than or equal to 0.22mm; and / or, the first inner conical surface 16 and the second inner conical surface 8 are interference fit, and along the radial direction of the oil casing threaded joint, the interference between the first inner conical surface 16 and the second inner conical surface 8 is greater than or equal to 0.12mm, and less than or equal to 0.22mm.

[0036] In the above technical solution, on the one hand, the first outer cone surface 10 and the second outer cone surface 2, as well as the first inner cone surface 16 and the second inner cone surface 8, are radially interfered with each other, forming two independent metal / metal sealing surfaces to respectively and simultaneously seal the internal and external fluid media of the oil casing; on the other hand, by controlling the interference fit, the contact stress distribution between the first outer cone surface 10 and the second outer cone surface 2, as well as between the first inner cone surface 16 and the second inner cone surface 8 can be improved, so that the oil casing threaded joint can seal the fluid media inside and outside the oil casing.

[0037] It should be noted that, in the embodiment of the present invention, the contact width and the interference are both formed after the external threaded joint 1 and the internal threaded joint 18 are tightened.

[0038] like Figure 3 and Figure 4 As shown, in the embodiment of the utility model, there is an angle ɑ between the first outer conical surface 10 and the axis of the oil casing threaded joint, and there is an angle ɑ between the second outer conical surface 2 and the axis of the oil casing threaded joint, and the angle ɑ satisfies the following formula: 10°≤ɑ≤14°; and / or, there is an angle β between the first inner conical surface 16 and the axis of the oil casing threaded joint, and there is an angle β between the second inner conical surface 8 and the axis of the oil casing threaded joint, and the angle β satisfies the following formula: 10°≤β≤14°.

[0039] In the above technical solution, by controlling the included angle ɑ, the contact stress distribution between the first outer conical surface 10 and the second outer conical surface 2 can be improved, so that the oil casing threaded joint can seal the fluid medium outside the oil casing; by controlling the included angle β, the contact stress distribution between the first inner conical surface 16 and the second inner conical surface 8 can be improved, so that the oil casing threaded joint can seal the fluid medium inside the oil casing.

[0040] Preferably, in an embodiment of the present utility model, ɑ=β.

[0041] In summary, compared with the prior art, in order to solve the sealing problem of the joint, the methods of optimizing the metal / metal sealing structure, developing sealing thread grease, adding sealing rings, etc. are adopted, in this embodiment, by setting two independent metal / metal sealing structures (i.e., the outer sealing part and the inner sealing part), and by controlling the parameters such as the contact width, the interference and the angle ɑ, the contact stress distribution on the sealing surface is improved, so that the oil casing threaded joint can independently seal the fluid medium inside and outside the oil casing.

[0042] In the Chinese patent known to the inventor (publication number CN2731065Y), the torque is mainly borne by the torque shoulder, but the torque shoulder is too close to the sealing surface. In the case of over-torque of the shoulder, the metal / metal seal is easily damaged, resulting in seal failure.

[0043] Therefore, if Figure 2 As shown, in the embodiment of the utility model, the torque bearing portion includes a first shoulder 13 and a second shoulder 5 which are sequentially arranged along the axial direction of the oil casing threaded joint, the first shoulder 13 is arranged on the internal threaded joint 18, the second shoulder 5 is arranged on the external threaded joint 1, an arc-shaped concave portion is provided on the second shoulder 5, and an arc-shaped convex portion is provided on the first shoulder 13, and the arc-shaped concave portion cooperates with the arc-shaped convex portion.

[0044] In the above technical scheme, on the one hand, compared with the method of using plane contact in the prior art, in this embodiment, by providing an arc-shaped recessed portion on the second shoulder 5 and an arc-shaped convex portion on the first shoulder 13, and the arc-shaped recessed portion cooperates with the arc-shaped convex portion, the contact area between the first shoulder 13 and the second shoulder 5 can be increased, thereby increasing the friction resistance between the first shoulder 13 and the second shoulder 5, so as to maximize the torsion resistance of the threaded joint and thereby reduce the occurrence of over-torque; on the other hand, by providing the torque-bearing portion between the first-level threaded portion and the second-level threaded portion, the torque-bearing portion can be kept away from the sealing surface (inner and outer sealing portions), so that even in the case of over-torque, the sealing effect of the sealing surface will not be affected, thereby avoiding sealing failure.

[0045] It should be noted that in the embodiment of the utility model, the make-up torque is borne by five parts, namely the first-stage threaded portion, the second-stage threaded portion, the outer sealing portion, the inner sealing portion and the torque-bearing portion. Among them, the make-up torque of the torque-bearing portion accounts for about 70% of the total torque of the threaded joint and is the main anti-torsion structure.

[0046] like Figure 2 As shown, in the embodiment of the utility model, the arc-shaped concave portion and the arc-shaped convex portion both have an arc radius R, and the arc radius R satisfies the following formula: 1.5mm≤R≤2.0mm. In this way, the contact area between the first shoulder 13 and the second shoulder 5 can be increased to improve the torsion resistance.

[0047] like Figure 2 As shown, in the embodiment of the utility model, along the radial direction of the oil casing threaded joint, the first shoulder 13 has a width H2, and the second shoulder 5 has a width H1, and the width H1 and the width H2 are both greater than 2.5 mm. In this way, the contact area between the first shoulder 13 and the second shoulder 5 can be increased as much as possible to improve the torsion resistance.

[0048] Preferably, in the embodiment of the present invention, the width H1 is equal to the width H2.

[0049] It should be noted that, in the embodiment of the present invention, the width H1 of the first shoulder 13 refers to the width of the first shoulder 13 in the radial direction of the threaded joint; similarly, the width H2 of the second shoulder 5 refers to the width of the second shoulder 5 in the radial direction of the threaded joint.

[0050] like Figure 4 As shown, in the embodiment of the utility model, an internal shoulder 17 is provided on the internal threaded joint 18, and along the axial direction of the oil casing threaded joint, a shoulder surface is provided on the side of the internal shoulder 17 facing the external threaded joint 1, and a gap δ is provided between the end face 9 of the external threaded joint 1 and the shoulder surface, and the gap δ satisfies the following formula: 0.15mm≤δ≤0.5mm.

[0051] In the above technical solution, compared with the prior art, in which the end face 9 and the inner shoulder 17 are subjected to interference in the axial direction of the oil casing threaded joint, which affects the sealing effect between the first inner conical surface 16 and the second inner conical surface 8, the gap δ is set to avoid axial deformation of the end face 9 and the inner shoulder 17, so as to avoid affecting the sealing effect between the first inner conical surface 16 and the second inner conical surface 8, taking into account the machining tolerance and the over-torque make-up operation.

[0052] It should be noted that, in the embodiment of the present invention, the gap δ is formed after the external threaded joint 1 and the internal threaded joint 18 are tightened.

[0053] like Figure 1As shown, in an embodiment of the utility model, the first-level threaded portion includes a first internal thread 12 and a first external thread 4 that are meshed together, the first internal thread 12 is arranged on the internal thread joint 18, the first external thread 4 is arranged on the external thread joint 1, and there is a storage gap between the first internal thread 12 and the first external thread 4, and the storage gap is greater than or equal to 0.1mm and less than or equal to 0.15mm; and / or, the second-level threaded portion includes a second internal thread 14 and a second external thread 6 that are meshed together, the second internal thread 14 is arranged on the internal thread joint 18, the second external thread 6 is arranged on the external thread joint 1, and there is a storage gap between the second internal thread 14 and the second external thread 6, and the storage gap is greater than or equal to 0.1mm and less than or equal to 0.15mm.

[0054] In the above technical solution, on the one hand, by meshing the first internal thread 12 with the first external thread 4 and the second internal thread 14 with the second external thread 6, the external thread joint 1 and the internal thread joint 18 can be connected; on the other hand, the above storage gap plays the role of storing thread grease, so that the screwing parts of the entire threaded joint can be well lubricated, thereby avoiding damage to the threaded joint due to the threading operation and extending the service life of the threaded joint.

[0055] It should be noted that, in the embodiments of the present invention, a storage gap exists between the second internal thread 14 and the second external thread 6, which means that there is a storage gap between the tooth top of the second internal thread 14 and the tooth bottom of the second external thread 6, and between the tooth bottom of the second internal thread 14 and the tooth top of the second external thread 6; a storage gap exists between the first internal thread 12 and the first external thread 4, which means that there is a storage gap between the tooth top of the first internal thread 12 and the tooth bottom of the first external thread 4, and between the tooth bottom of the first internal thread 12 and the tooth top of the first external thread 4.

[0056] like Figure 1 As shown, in an embodiment of the utility model, the oil casing threaded joint also includes an outer transition portion for connecting the outer sealing portion and the first-level threaded portion, the outer transition portion includes a first outer cylindrical surface 11 arranged on the internal threaded joint 18 and a second outer cylindrical surface 3 arranged on the external threaded joint 1, and along the radial direction of the oil casing threaded joint, there is a storage gap between the first outer cylindrical surface 11 and the second outer cylindrical surface 3, and the storage gap is greater than or equal to 0.1mm and less than or equal to 0.15mm; and / or, the oil casing threaded joint also includes an inner transition portion for connecting the inner sealing portion and the second-level threaded portion, the inner transition portion includes a first inner cylindrical surface 15 arranged on the internal threaded joint 18 and a second inner cylindrical surface 7 arranged on the external threaded joint 1, and along the radial direction of the oil casing threaded joint, there is a storage gap between the first inner cylindrical surface 15 and the second inner cylindrical surface 7, and the storage gap is greater than or equal to 0.1mm and less than or equal to 0.15mm.

[0057] Through the above arrangement, the storage gap can store thread grease, so that the screwing part of the entire threaded joint can be well lubricated, thereby avoiding damage to the threaded joint due to the make-up operation and extending the service life of the threaded joint.

[0058] It should be noted that, in the embodiment of the present utility model, the storage gap is formed after the external threaded joint 1 and the internal threaded joint 18 are tightened.

[0059] From the above description, it can be seen that the above-mentioned embodiments of the utility model achieve the following technical effects: on the one hand, by setting the outer sealing part, the fluid medium outside the oil casing can be prevented from entering the first-stage threaded part, the torque bearing part and the second-stage threaded part, and by setting the inner sealing part, the fluid medium inside the oil casing can be prevented from entering the second-stage threaded part, the torque bearing part and the first-stage threaded part, and the outer sealing part and the inner sealing part are arranged at intervals along the axial direction of the oil casing threaded joint, so that the inner sealing part and the outer sealing part can be arranged independently of each other, so that the inner sealing part and the outer sealing part can respectively and simultaneously seal the inner and outer fluid media of the oil casing to improve the sealing effect of the threaded joint; on the other hand, compared with the poor torsion resistance of the API joint in the prior art, which leads to frequent sticking failure of the thread and is difficult to meet the requirements of multiple mounting and dismounting, in this embodiment, by additionally setting the torque bearing part, part of the torque can be borne, thereby reducing the probability of frequent sticking failure of the thread, and the torque bearing part is located between the first-stage threaded part and the second-stage threaded part, which can avoid damaging the sealing surface, thereby avoiding sealing failure.

[0060] The above description is only the preferred embodiment of the utility model, and is not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

Claims

1. A threaded joint for oil casing, characterized in that: include: Internal thread connector (18); An external threaded joint (1) is connected to the internal threaded joint (18); along the axial direction of the oil casing threaded joint, an external sealing portion, a first-stage threaded portion, a torque bearing portion, a second-stage threaded portion and an internal sealing portion are sequentially provided between the external threaded joint (1) and the internal threaded joint (18) from the outside to the inside; the internal threaded joint (18) is connected to the external threaded joint (1) via the first-stage threaded portion and the second-stage threaded portion; the torque bearing portion is used to bear part of the torque and achieve positioning; The outer sealing portion comprises a first outer conical surface (10) and a second outer conical surface (2) which are respectively arranged on the inner thread joint (18) and the outer thread joint (1), and the first outer conical surface (10) and the second outer conical surface (2) are sealingly matched; The inner sealing portion comprises a first inner conical surface (16) and a second inner conical surface (8) which are respectively arranged on the inner thread joint (18) and the outer thread joint (1), and the first inner conical surface (16) and the second inner conical surface (8) are sealingly matched.

2. The oil casing threaded joint according to claim 1, characterized in that: There is a contact width A between the first outer conical surface (10) and the second outer conical surface (2), and the contact width A satisfies the following relationship: 2.5 mm ≤ A ≤ 3.5 mm; and / or, There is a contact width B between the first inner conical surface (16) and the second inner conical surface (8), and the contact width B satisfies the following relationship: 2.5 mm ≤ B ≤ 3.5 mm.

3. The oil casing threaded joint according to claim 1, characterized in that: The first outer conical surface (10) and the second outer conical surface (2) are interference fit, and along the radial direction of the oil casing threaded joint, the interference between the first outer conical surface (10) and the second outer conical surface (2) is greater than or equal to 0.12 mm and less than or equal to 0.22 mm; and / or, The first inner conical surface (16) and the second inner conical surface (8) are interference fit, and along the radial direction of the oil casing threaded joint, the interference between the first inner conical surface (16) and the second inner conical surface (8) is greater than or equal to 0.12 mm and less than or equal to 0.22 mm.

4. The oil casing threaded joint according to claim 1, characterized in that: An included angle ɑ is formed between the first outer conical surface (10) and the axis of the oil casing threaded joint, and an included angle ɑ is formed between the second outer conical surface (2) and the axis of the oil casing threaded joint, and the included angle ɑ satisfies the following formula: 10°≤ɑ≤14°; and / or, An included angle β is formed between the first inner conical surface (16) and the axis of the oil casing threaded joint, and an included angle β is formed between the second inner conical surface (8) and the axis of the oil casing threaded joint. The included angle β satisfies the following formula: 10°≤β≤14°.

5. The oil casing threaded joint according to any one of claims 1 to 4, characterized in that: The torque bearing portion comprises a first shoulder (13) and a second shoulder (5) which are sequentially arranged along the axial direction of the oil casing threaded joint, wherein the first shoulder (13) is arranged on the internal threaded joint (18), and the second shoulder (5) is arranged on the external threaded joint (1), and an arc-shaped concave portion is arranged on the second shoulder (5), and an arc-shaped convex portion is arranged on the first shoulder (13), and the arc-shaped concave portion cooperates with the arc-shaped convex portion.

6. The oil casing threaded joint according to claim 5, characterized in that: The arc-shaped concave portion and the arc-shaped convex portion both have an arc radius R, and the arc radius R satisfies the following formula: 1.5 mm ≤ R ≤ 2.0 mm.

7. The oil casing threaded joint according to claim 5, characterized in that: Along the radial direction of the oil casing threaded joint, the first shoulder (13) has a width H2, and the second shoulder (5) has a width H1, and both the width H1 and the width H2 are greater than 2.5 mm.

8. The oil casing threaded joint according to any one of claims 1 to 4, characterized in that: The internal threaded joint (18) is provided with an internal shoulder (17), and along the axial direction of the oil casing threaded joint, a shoulder surface is provided on the side of the internal shoulder (17) facing the external threaded joint (1), and a gap δ is provided between the end face (9) of the external threaded joint (1) and the shoulder surface, and the gap δ satisfies the following formula: 0.15mm≤δ≤0.5mm.

9. The oil casing threaded joint according to any one of claims 1 to 4, characterized in that: The first-stage threaded portion comprises a first internal thread (12) and a first external thread (4) which are meshed together, the first internal thread (12) being arranged on the internal thread joint (18), the first external thread (4) being arranged on the external thread joint (1), a storage gap being provided between the first internal thread (12) and the first external thread (4), the storage gap being greater than or equal to 0.1 mm and less than or equal to 0.15 mm; and / or, The second-stage threaded portion comprises a second internal thread (14) and a second external thread (6) which are meshed together, the second internal thread (14) being arranged on the internal thread joint (18), the second external thread (6) being arranged on the external thread joint (1), and a storage gap being provided between the second internal thread (14) and the second external thread (6), wherein the storage gap is greater than or equal to 0.1 mm and less than or equal to 0.15 mm.

10. The oil casing threaded joint according to any one of claims 1 to 4, characterized in that: The oil casing threaded joint further comprises an outer transition portion for connecting the outer sealing portion and the first-stage threaded portion, the outer transition portion comprising a first outer cylindrical surface (11) provided on the internal threaded joint (18) and a second outer cylindrical surface (3) provided on the external threaded joint (1), and along the radial direction of the oil casing threaded joint, a storage gap is provided between the first outer cylindrical surface (11) and the second outer cylindrical surface (3), and the storage gap is greater than or equal to 0.1 mm and less than or equal to 0.15 mm; and / or, The oil casing threaded joint further comprises an inner transition portion for connecting the inner sealing portion and the second-stage threaded portion, the inner transition portion comprising a first inner cylindrical surface (15) arranged on the inner threaded joint (18) and a second inner cylindrical surface (7) arranged on the outer threaded joint (1), and along the radial direction of the oil casing threaded joint, a storage gap is provided between the first inner cylindrical surface (15) and the second inner cylindrical surface (7), and the storage gap is greater than or equal to 0.1 mm and less than or equal to 0.15 mm.

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