A threaded joint based on position control

Abstract

The present invention discloses a threaded joint based on position control, including a male thread and a female thread, wherein the cross-sectional shapes of the male thread and the female thread are trapezoidal threads, rectangular threads or inverted trapezoidal threads; in the thread structure, the tooth top is parallel to the tooth bottom, the angle between the tooth side and the tooth top or tooth bottom is ≥80°, the thread taper is 1:8~1:14, the thread tooth height is 1.0mm~1.6mm, and the pitch is 6mm / tooth~8mm / tooth. The present invention realizes the position control of the pipe tightening during the threading process by adopting a special thread structure. By adopting this structural method, the over-tightening problem existing in the existing API threaded joints can be avoided; at the same time, the problem that conventional special threaded joints require special torque equipment for threading and complicated operation can also be avoided.

Description

Technical Field

[0001] The invention relates to the field of petroleum pipe engineering machinery, and in particular to a threaded joint based on position control. Background Art

[0002] Oil pipe is mainly used for drilling oil and gas wells and transporting oil and gas. It includes oil drill pipe, oil casing and pumping pipe. Oil drill pipe is mainly used to connect drill collar and drill bit and transmit drilling power. Oil casing is mainly used to support the well wall during drilling and after completion to ensure the normal operation of the drilling process and the entire oil well after completion. Pumping pipe mainly transports oil and gas at the bottom of the oil well to the ground.

[0003] Oil casing is the lifeline to maintain the operation of oil wells. Due to different geological conditions, the stress state downhole is complex, and the combined effects of tension, compression, bending and torsion stress act on the pipe body, which puts higher requirements on the quality of the casing itself. Once the casing itself is damaged for some reason, it may lead to a reduction in production of the entire well or even scrapping.

[0004] In 1924, API formulated the first oil well pipe standard. The thread of the oil casing joint was V-thread with 10 teeth per inch and 8 teeth per inch, but it was later replaced by API 8-tooth round thread and eccentric thread, which are still used today. API SPEC 5B standard stipulates that the commonly used casing threads are round thread (abbreviated as CSG) and eccentric thread (abbreviated as BCSG). These two thread joints are commonly used in my country's oil and gas fields.

[0005] Round threads are divided into short round threads for casing (abbreviated in English as CSG) and long round threads for casing (LCSG). The English abbreviation for round threads for oil pipes is TBG, which is subdivided into non-thickened oil pipe threads (TBG) and external thickened oil pipe threads (UP TBG). Round threads are shoulder-free tapered pipe threads that require coupling connections. The thread profile is triangular, with a round top and round bottom, a tooth angle of 60°, a thread taper of 1:16, and the bisector of the tooth angle is perpendicular to the axis. When the thread is tightened, it is sealed by the tooth side surfaces of the internal and external threads.

[0006] The slanted trapezoidal thread is designed to improve the ability to resist axial tensile or axial compression loads and provide leakage resistance. It is abbreviated as BCSG in English. It is a non-shoulder tapered pipe thread that requires a coupling connection. The tooth type is slanted trapezoidal, flat top and flat bottom. The specification is 41 / 2-13 5 / 8 casing slanted trapezoidal thread, the taper on the diameter is 62.5mm / m, and there are 5 threads per 25.4mm (the pitch is 5.08mm); the angle between the guide tooth side and the perpendicular line of the thread axis is 10°; the angle between the load side and the perpendicular line of the thread axis is 3°; the tooth top and tooth bottom are conical and parallel to the thread taper; the fillet radius of the guide side tooth top (0.762mm R) is larger than the fillet radius of the load side tooth top (0.203mm R), which is helpful for butt and make-up.

[0007] With the exploration and development of oil and gas in my country, especially the increase of deep wells, ultra-deep wells, high-pressure gas wells, directional wells, and wells containing hydrogen sulfide, higher requirements are put forward for the performance of oil casing joints. The air tightness, connection strength, and corrosion resistance of API round threads and partial ladder threads are no longer suitable for the requirements. For this reason, countries have launched the development and application of special thread joints, among which the representative ones are Tenaris Blue series and Wedge series, VAM VAM TOP series and VAM 21 series, JFE Lion series and Tiger series, Hunting SEAL-LOCK series, etc. This type of thread is generally called non-API thread or special thread. The structure, shape and use requirements of this type of thread are mainly implemented in accordance with the standards or requirements of each manufacturer.

[0008] API standard round threads and trapezoidal threads both use tapered threads and have no anti-torque shoulders. API round threads are mainly controlled by torque, and trapezoidal threads are mainly controlled by the triangular mark on the pipe body. Both methods have the risk of over-tightening and causing threaded joint failure.

[0009] Special threaded joints are generally equipped with anti-torque shoulders, and precise torque meters are used for make-up control, which significantly reduces the risk of over-tightening the joints. However, such threaded joints require torque meters to monitor and record the make-up process, which is more complicated to operate. Some manufacturers do not have such equipment and do not have the operating conditions.

[0010] The Chinese patent document with the announcement number CN201391239Y and the name "A torque shoulder cladding corrosion-resistant alloy and sealing ring seal connection coupling" discloses a connection coupling with a sealing ring seal, which includes a steel coupling base arranged on a pipe body, a torque shoulder cladding corrosion-resistant alloy layer is arranged in the middle of the steel coupling base, and a back-off groove of cladding corrosion-resistant alloy layer is arranged at the root of the outer side of the torque shoulder, and a sealing ring is placed in the back-off groove. The connection coupling disclosed in the patent document has a simple structure and is easy to use and operate. The sealing effect is achieved by cladding corrosion-resistant alloy and sealing ring, and can be used for the anti-corrosion integrity and sealing integrity connection of composite oil pipes and casings, but it cannot be interchanged with standard casing or joint products.

[0011] The Chinese patent document with the announcement number CN2409331Y and the name "Oil and Casing Trapezoidal Threaded Joint" involves an oil and casing trapezoidal threaded joint suitable for oilfield drilling. It is composed of a pipe body and a pipe coupling screwed together by a trapezoidal pipe taper thread. The taper of the middle diameter, tooth bottom and tooth top of the trapezoidal pipe taper thread of the pipe body and the pipe coupling is 1: T. The tooth top taper of the trapezoidal pipe taper thread of the pipe coupling is slightly increased to 1: (T-ζ) over an effective length at the beginning of the trapezoidal pipe taper thread of the pipe coupling, and ζ is 4 to 9. The technical solution involved in the patent document achieves a limiting effect by changing the processing technology or the thread morphology to reduce the risk of joint buckling, but it has a certain processing difficulty.

[0012] The Chinese patent document with publication number CN202125257U and titled “High over-torque resistance, high sealing, anti-seizing oil casing joint” discloses an oil casing joint with high torque resistance, strong sealing and good anti-seizing effect. The oil pipe joint is formed by connecting a pipe body with external threads at the end and a coupling with internal threads. The pipe body is provided with a pipe body shoulder, a pipe body sealing surface and a pipe body right-angle shoulder, and the coupling is provided with a coupling shoulder, a coupling sealing surface and a coupling right-angle shoulder. After the external and internal threads are connected, the pipe body sealing surface and the coupling sealing surface, the pipe body shoulder and the coupling shoulder, and the pipe body right-angle shoulder and the coupling right-angle shoulder respectively form three sealing structures. The external and internal threads are trapezoidal threads with unequal tooth heights.

[0013] Patent CN203008801U introduces an integral oil casing threaded joint with an air-sealing structure, which consists of sealing parts at both ends and a threaded section in the middle, where each sealing part is composed of a sealing surface and a torque-stop shoulder. Through this optimized structure, the joint has good sealing performance, is easy to process and inspect, and can be screwed multiple times under high torque conditions. Summary of the invention

[0014] The object of the present invention is to provide a threaded joint based on position control to solve the above technical problems.

[0015] To achieve the above purpose, the present invention adopts the following technical solutions:

[0016] A threaded joint based on position control comprises a male thread and a female thread, wherein the cross-sectional shapes of the male thread and the female thread are trapezoidal threads, rectangular threads or inverted trapezoidal threads; in the thread structure, the tooth top is parallel to the tooth bottom, the angle between the tooth side and the tooth top or tooth bottom is ≥80°, the thread taper is 1:8~1:14, the thread tooth height is 1.0mm~1.6mm, and the pitch is 6mm / tooth~8mm / tooth.

[0017] As a further scheme of the present invention, the cross-section of the male thread and the female thread gradually changes along the spiral direction of the thread, which is manifested as the tooth height remains unchanged, the tooth width of the male thread gradually increases, and the tooth width of the female thread gradually decreases. The tooth width change rate of the male thread and the female thread is the same, which is 0.2mm / tooth~1.0mm / tooth, that is, the tooth width of the male thread increases by 0.2mm~1mm for each rotation toward the larger end, and the tooth width of the female thread decreases by 0.2mm~1mm for each rotation toward the larger end.

[0018] As a further solution of the present invention, the cross-sectional shape of the male thread and the female thread is a rectangular thread as an example, and a section of the thread is cut, wherein the male thread and the female thread have a gradual tooth shape and mesh with each other;

[0019] In a section of thread cut, dp is the tooth width of the male thread corresponding to the meshing position, db The tooth width of the female thread corresponding to the meshing position, do is the tooth gap between the front and rear female threads, d is the thread pitch, then:

[0020] db + do = d ;

[0021] Male thread in screw-in direction dp Gradually smaller; female thread db Gradually increasing, the thread pitch d is a fixed value, the female thread corresponds to do Gradually decrease,

[0022] As the thread is screwed in gradually, dp and db Rotate to the corresponding position so that:

[0023] db + dp = d ;

[0024] Right now dp = do At this time, the male and female threads fit together. Due to the wedge effect formed by the gradual tooth shape of the male and female threads, the threads cannot be screwed in further, and the male and female threads reach the ideal screwing position and stop screwing;

[0025] Select appropriate points on the male and female threads respectively so that the points correspond to the tooth width of the male and female threadsdp , db satisfy:

[0026] db + dp = d ;

[0027] The distance from this point to the end face of the male thread shoulder is Lp , the distance from this point to the end face of the female thread is Lb , so that Lp Greater than Lb ,set up

[0028] Δd = Lp - Lb ;

[0029] In the actual process of tightening the pipe, the gap between the male thread shoulder and the female thread end face after tightening is observed to determine whether the pipe is tightened in place. Δd , indicating that the pipe is screwed into place; otherwise, it is judged that the pipe is not screwed into place.

[0030] Compared with the prior art, the present invention has the following advantages: the present invention develops a new threaded joint, which realizes the control of the pipe screwing position during the screwing process by adopting a special thread structure. By adopting this structure, the over-tightening problem existing in the existing API threaded joint can be avoided; at the same time, the problem that the conventional special threaded joint needs a special torque device for screwing and the operation is complicated can also be avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the thread cross section of the present invention (where a is a trapezoidal thread, b is a rectangular thread, and c is an inverted trapezoidal thread).

[0032] Figure 2 Schematic diagram of thread engagement of the present invention.

[0033] Figure 3 It is a schematic diagram of the threaded connection of the present invention. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] A threaded joint based on position control includes a male thread and a female thread, the cross-sectional shape of the male thread and the female thread is a trapezoidal thread, a rectangular thread or an inverted trapezoidal thread; in the thread structure, the tooth top is parallel to the tooth bottom, the angle between the tooth side and the tooth top or tooth bottom is ≥80°, the thread taper is 1:8~1:14, the thread tooth height is 1.0mm~1.6mm, and the pitch is 6mm / tooth~8mm / tooth. The cross-section of the male thread and the female thread gradually changes along the spiral direction of the thread, which is manifested as the tooth height remains unchanged, the male thread tooth width gradually increases, and the female thread tooth width gradually decreases. The male thread and the female thread tooth width change rate is the same, which is 0.2mm / tooth~1.0mm / tooth, that is, the male thread increases 0.2mm~1mm in tooth width for each rotation toward the large end, and the female thread decreases 0.2mm~1mm in tooth width for each rotation toward the large end.

[0036] like Figure 2 , taking the cross-sectional shape of the male and female threads as a rectangular thread as an example, a section of the thread is cut, wherein the male and female threads are in a gradual tooth shape and mesh with each other;

[0037] In a section of thread cut, dp is the tooth width of the male thread corresponding to the meshing position, db The tooth width of the female thread corresponding to the meshing position, do is the tooth gap between the front and rear female threads, d is the thread pitch, then:

[0038] db + do = d ;

[0039] Male thread in screw-in direction dp Gradually smaller; female thread db Gradually increasing, the thread pitch d is a fixed value, the female thread corresponds to do Gradually decrease,

[0040] As the thread is screwed in gradually, dp and db Rotate to the corresponding position so that:

[0041] db + dp = d ;

[0042] Right now dp = do At this time, the male and female threads fit together. Due to the wedge effect formed by the gradual tooth shape of the male and female threads, the threads cannot be screwed in further, and the male and female threads reach the ideal screwing position and stop screwing;

[0043] Select appropriate points on the male and female threads respectively so that the points correspond to the tooth width of the male and female threads dp , db satisfy:

[0044] db + dp = d ;

[0045] The distance from this point to the end face of the male thread shoulder is Lp , the distance from this point to the end face of the female thread is Lb , so that Lp Greater than Lb ,set up

[0046] Δd = Lp - Lb ;

[0047] In the actual process of tightening the pipe, the gap between the male thread shoulder and the female thread end face after tightening is observed to determine whether the pipe is tightened in place. Δd , indicating that the pipe is screwed into place; otherwise, it is judged that the pipe is not screwed into place.

[0048] Specific example: Select the 101.6mm×7.8mm specification and design an inverted trapezoidal thread. The tooth top is parallel to the tooth bottom, and the angle between the tooth side and the tooth top or tooth bottom is 84.5°. The thread taper is 1:2, the thread tooth height is 1.475mm, and the pitch is 7mm / tooth. The change rate of the male and female thread tooth width is 0.3mm / tooth, that is, the tooth width of the male thread increases by 0.3mm for each rotation toward the large end, and the tooth width of the female thread decreases by 0.3mm for each rotation toward the large end.

[0049] Select a point on the thread such that:

[0050] db = dp = 3.5 mm ;

[0051] Meet the thread matching requirements for pipe tightening.

[0052] According to the thread structure relationship, the Lp =37.3mm, Lb =37mm. Then Δd =0.3mm.

[0053] In actual pipe tightening, observe the gap between the male thread shoulder end face and the female thread end face after tightening to determine whether the pipe is tightened in place. If the gap between the male and female end faces is less than or equal to 0.3mm after the pipe tightening, it indicates that the pipe is tightened in place; otherwise, it is judged that the pipe is not tightened in place.

[0054] The above is a preferred embodiment of the present invention. For ordinary technicians in this field, according to the teachings of the present invention, without departing from the principles and spirit of the present invention, changes, modifications, substitutions and variations made to the implementation methods are still within the scope of protection of the present invention.

Claims

1. A threaded joint based on position control, characterized in that: It includes male threads and female threads, and the cross-sectional shapes of the male threads and female threads are trapezoidal threads, rectangular threads or inverted trapezoidal threads; in the thread structure, the tooth top is parallel to the tooth bottom, the angle between the tooth side and the tooth top or tooth bottom is ≥80°, the thread taper is 1:8~1:14, the thread tooth height is 1.0mm~1.6mm, and the pitch is 6mm / tooth~8mm / tooth; the cross-sectional shapes of the male threads and female threads gradually change along the spiral direction of the thread, which is manifested as the tooth height remains unchanged, the male thread tooth width gradually increases, and the female thread tooth width gradually decreases. The tooth width change rate of the male threads and female threads is the same, which is 0.2mm / tooth~1.0mm / tooth, that is, the tooth width of the male thread increases by 0.2mm~1mm for each rotation of the male thread toward the large end, and the tooth width of the female thread decreases by 0.2mm~1mm for each rotation of the female thread toward the large end; the cross-sectional shape of the male threads and female threads is a rectangular thread, and a section of the thread is cut, in which the male thread and the female thread have a gradual tooth shape and mesh with each other; In a section of thread cut, dp is the tooth width of the male thread at the meshing position, db The tooth width of the female thread corresponding to the meshing position, do is the tooth gap between the front and rear female threads, d is the thread pitch, then: ； Male thread in screw-in direction dp Gradually smaller; female thread db Gradually increasing, the thread pitch d is a fixed value, the female thread corresponds to do Gradually decrease, As the thread is screwed in gradually, dp and db Rotate to the corresponding position so that: ； Right now dp=do At this time, the male and female threads fit together. Due to the wedge effect formed by the gradual tooth shape of the male and female threads, the threads cannot be screwed in further, and the male and female threads reach the ideal screwing position and stop screwing; Select appropriate points on the male and female threads respectively so that the points correspond to the tooth width of the male and female threads dp , db satisfy: ； The distance from this point to the end face of the male thread shoulder is Lp , the distance from this point to the end face of the female thread is Lb , so that Lp Greater than Lb ,set up ； In the actual process of tightening the pipe, the gap between the male thread shoulder and the female thread end face after tightening is observed to determine whether the pipe is tightened in place. Δd , indicating that the pipe is screwed into place; otherwise, it is judged that the pipe is not screwed into place.

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