High-torsion-resistance sleeve air-tight seal screwed joint structure

Abstract

The invention belongs to the field of petroleum industry, and discloses a high-torsion-resistance casing air-tight seal screwed joint structure which comprises a male end screwed joint and a female end screwed joint, and the male end screwed joint comprises male end threads, a male end inner sealing face, a male end outer sealing face, a male end inner circular bead and a male end outer circular bead. The female end screwed joint part comprises a female end thread, a female end inner sealing surface, a female end outer sealing surface, a female end inner circular bead and a female end outer circular bead; in the screwing process of the male end threaded connector and the female end threaded connector, the male end outer circular bead and the female end outer circular bead firstly make contact with each other and abut against each other, then bear torque and continue screwing, then the male end inner circular bead and the female end inner circular bead make contact with each other and abut against each other, screwing and screwing are finished, and a special thread form with high connection strength and excellent air-tight sealing capacity is formed. The over-torsion torque can be more than four times that of a common API connector, the connector is not damaged, and the air-tight sealing performance and the connecting performance can still be guaranteed.

Description

Technical Field

[0001] This invention belongs to the petroleum industry and relates to a high-torsion-resistant gas-tight threaded joint structure for sleeves. Background Technology

[0002] With the development of deep and ultra-deep shale gas, the performance requirements for special threaded joints in production casing are becoming increasingly stringent. Shale gas wells are mostly horizontal, with horizontal sections typically exceeding 2000 meters in length. This makes casing installation difficult due to high friction. Conventional sliding casing installation methods can lead to helical buckling, resulting in casing failure or incomplete installation. To cope with the enormous friction during installation, casing joints need to possess extremely high resistance to over-torque.

[0003] Most existing technical solutions struggle to balance high torsional resistance and sealing performance, as detailed below: Chinese patent CN222010135U discloses a deformation-resistant, high-torsion milling pipe threaded joint. By optimizing the structure and dimensional tolerances of the thread, it meets the requirements for ultra-high torsion fast connection. However, the gas seal is difficult to handle for use in deep well development.

[0004] Chinese patent CN203022650U discloses a high-torsion-resistance sleeve threaded joint. The joint includes a coupling and connecting pipe fittings, as well as a set of anti-torsion structures. The joint has high torsional resistance, and its torsional resistance can reach 3 to 3.5 times that of ordinary API joints. Although it has high connection strength and good airtight performance, the sealing surface of the joint may be damaged due to scratches, collisions or stress deformation during the installation process, which may pose a hidden danger for airtight failure in subsequent production processes.

[0005] Chinese patent CN205387913U discloses a special double-step sealing connection structure, which includes a sleeve with an external thread at one end and a coupling with an internal thread that are screwed together. The sealing parts of the external thread of the sleeve and the internal thread of the coupling are both in the shape of two steps. At the same time, the sealing surface material will not easily undergo local yielding deformation when the joint is subjected to high torsional stress. However, its processing is complicated and the cost is high.

[0006] Chinese patent CN106168121A discloses an integral threaded joint structure for upsetting the pipe end of an oil casing pipe. It increases the wall thickness by upsetting the pipe end and adopts a two-stage thread structure. It combines the quantitative relationship formula between the shoulder size and the pipe body parameters. However, the two-stage thread structure it adopts is relatively complex to process and requires high manufacturing precision. Although its torsional resistance (2 times API) is better than conventional products, it still needs to be further improved to meet the extremely harsh downhole friction of ultra-long horizontal wells.

[0007] Therefore, it is necessary to develop a high-torsion-resistant gas-tight threaded joint for complex and extremely demanding well conditions such as horizontal wells with large displacement, while meeting users' requirements for high torsion and gas tightness in well conditions. Summary of the Invention

[0008] To address the structural deficiencies in existing technologies, the present invention aims to provide a high-torsion-resistance casing gas-tight threaded joint structure to solve the problem of difficulty in running long horizontal casing sections in shale gas wells or directional wells. By upsetting the casing end, the upset end of the casing simultaneously possesses an inner shoulder and an outer shoulder. A structural design with the inner and outer shoulders completely aligned is adopted. The height of the inner shoulder at the male end and the outer shoulder at the female end are determined by combining the upset outer diameter, the thread loss length, and the thread taper, ensuring high over-torsion capacity and gas-tight performance. This achieves a significant improvement in over-torsion torque resistance, reaching more than 4 times that of ordinary API joints, thus meeting the extreme performance requirements of casing joints in ultra-deep shale gas development.

[0009] The technical solution for achieving the objective of this invention is: This invention provides a high-torsion-resistant gas-tight threaded joint structure for bushings. The threaded joint includes a male threaded joint and a female threaded joint. The male threaded joint is located on the upset portion of the male bushing end, and the female threaded joint is located on the upset portion of the female bushing end. The male threaded joint includes a male thread, an inner sealing surface, an outer sealing surface, an inner shoulder, and an outer shoulder. The female threaded joint includes a female thread, an inner sealing surface, an outer sealing surface, an inner shoulder, and an outer shoulder. The male and female threaded joints are symmetrical structures and simultaneously satisfy the following formula: T = h1 + h2 + Ls * τ; (Wd) / 2=T; h1 + h2 = (80%~100%)t; h1 = (40%~50%)t; In the formula: W is the outer diameter of the upset pipe end, d is the inner diameter of the upset pipe end, h1 is the inner shoulder height of the male end; h2 is the outer shoulder height of the female end; t is the nominal wall thickness of the sleeve; T is the wall thickness of the sleeve end after upset; Ls is the thread roll loss length; τ is the thread taper.

[0010] During the tightening process of the male and female threaded connectors, the outer shoulders of the male and female ends first come into contact and align, bearing the torque and continuing tightening. Subsequently, the inner shoulders of the male and female ends come into contact and align, completing the tightening. Through the sequential alignment of the inner and outer shoulders, the connector's excellent torque resistance and airtightness are ensured.

[0011] Furthermore, the outer diameter of the upset portion at the end of the casing is 1.03 to 1.05 times the outer diameter of the casing body.

[0012] Furthermore, the male end thread and the female end thread are trapezoidal threads, and the thread taper τ ranges from 1:20 to 1:8.

[0013] Furthermore, the bearing-side angle of the male end thread and the female end thread is -2 to -10°, and the guide-side angle is 8 to 20°.

[0014] Furthermore, the pitch of the male end thread and the female end thread is 3.63mm~6.35mm.

[0015] Furthermore, the tooth height of both the male and female threads is 0.8~1.575mm.

[0016] Furthermore, for the female threaded connector, the thread loss length is a negative tolerance (0, -a); for the male threaded connector, the thread loss length is a positive tolerance (+a, 0), where 0 <a≤0.5。

[0017] Furthermore, the angle between the inner shoulder of the male end and the inner shoulder of the female end and the axis is 75°~90°, and the angle between the outer shoulder of the male end and the outer shoulder of the female end and the axis direction is 75°~90°.

[0018] Furthermore, the taper of the inner sealing surface of the female end, the outer sealing surface of the female end, the inner sealing surface of the male end, and the outer sealing surface of the male end along the axis of the pipe body is 1:20 to 1:8.

[0019] The advantages and beneficial effects of this invention are: This invention determines the height of the inner shoulder of the male end and the outer shoulder of the female end by parametrically adjusting the size of the upset outer diameter, the thread loss length, and the thread taper after upsetting the casing end. Based on the use of a single-stage thread, a special thread structure with high connection strength and excellent gas sealing capability is formed. The over-torque can reach more than 4 times that of ordinary API joints without damage to the joint, thus ensuring gas sealing performance and connection performance. Especially in complex and extreme well conditions such as large-displacement horizontal wells in shale gas development, the over-torque capability is significantly improved, avoiding thread sticking and sealing surface damage caused by over-torque. The inner and outer double sealing surfaces can effectively ensure the penetration of internal and external pressures and ensure gas sealing performance under alternating loads. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the female end threaded joint structure of the high-torsion-resistant sleeve gas-tight threaded joint structure of the present invention. Figure 2 This is a schematic diagram of the male end threaded joint structure of the high-torsion-resistant sleeve gas-tight threaded joint structure of the present invention. Figure 3 This is a schematic diagram of the male and female ends of the high-torsion sleeve gas-tight threaded joint structure of the present invention after screwing.

[0021] The reference numerals in the attached diagram are as follows: 1-Female threaded connector, 2-Female inner shoulder, 3-Female inner sealing surface, 4-Female outer shoulder, 5-Female outer sealing surface, 6-Female thread, 7-Male threaded connector, 8-Male inner shoulder, 9-Male inner sealing surface, 10-Male outer shoulder, 11-Male outer sealing surface, 12-Male thread. Detailed Implementation

[0022] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0023] like Figures 1-3 The diagram illustrates a high-torsion-resistance gas-tight threaded joint structure for a bushing. The joint includes a male threaded joint 7 and a female threaded joint 1. The male threaded joint 7 is located on the upset portion of the male bushing end, and the female threaded joint 1 is located on the upset portion of the female bushing end. The male threaded joint 7 includes a male thread, an inner sealing surface 9, an outer sealing surface 11, an inner shoulder 8, and an outer shoulder 10. The female threaded joint 1 includes a female thread 6, an inner sealing surface 3, an outer sealing surface 5, an inner shoulder 2, and an outer shoulder 4. The male threaded joint 7 and the female threaded joint 1 are symmetrical structures and satisfy the following formula: T = h1 + h2 + Ls * τ; (Wd) / 2=T; h1 + h2 = (80%~100%)t; h1 = (40%~50%)t; In the formula: W: outer diameter of the tube end after upsetting d: Inner diameter of the pipe end after upsetting h1: Height of the inner shoulder of the male end; h2: Height of the outer shoulder of the mother end; t: Nominal wall thickness of the casing; T: Thickness of the pipe end wall after upsetting of the casing Ls: Thread loss length τ: Thread taper During the tightening process of the male threaded connector 7 and the female threaded connector 1, the outer shoulder 10 of the male end and the outer shoulder 4 of the female end first come into contact and align, then bear the torque and continue tightening. Subsequently, the inner shoulder 8 of the male end and the inner shoulder 2 of the female end come into contact and align, and the tightening ends. Through the sequential alignment of the inner and outer shoulders, the connector's excellent torque resistance and airtightness are ensured.

[0024] The bearing side angle of the male end thread and the female end thread is -2 to -10°, and the guide side angle is 8 to 20°.

[0025] The angle between the inner shoulder of the male end and the inner shoulder of the female end and the axis is 75°~90°, and the angle between the outer shoulder of the male end and the outer shoulder of the female end and the axis direction is 75°~90°.

[0026] The male and female threads are trapezoidal threads with a pitch of 3.63mm to 6.35mm, a taper of 1:20 to 1:8, a male thread height of 0.8 to 1.575mm, and a female thread height of 0.8 to 1.575mm.

[0027] The nominal length of the thread loss of the high-torsion sleeve gas-tight threaded joint is Ls. For the female end threaded joint, the thread loss length has a negative tolerance of (0, -a); for the male end threaded joint, the thread loss length has a positive tolerance of (+a, 0), where 0 <a≤0.5。

[0028] The functionality of this invention applied to the gas-tight threaded joint structure of high-torsion sleeves is achieved as follows: Taking the sleeve design specification of 139.7*12.7mm as an example: like Figure 1 and Figure 2 As shown, the angle of the trapezoidal toothed thread on the bearing side is -3°, and the angle on the guide side is 20°. The tooth height of the male thread is 1.42mm, the tooth height of the female thread is 1.42mm, the pitch is 4.23mm, the thread taper τ is 1:16, and the taper of the sealing surface along the pipe axis is 1:10. The angle between the inner shoulder of the male and female ends and the axis is 75°, and the angle between the outer shoulder of the male and female ends and the axis is 90°. The height of the inner shoulder of the male end h1 is 5.55mm, the height of the outer shoulder of the female end h2 is 4.7mm, the outer diameter W of the upset pipe end is 146mm, the inner diameter d of the upset pipe end is 113mm, the wall thickness T of the upset pipe end is 16.5mm, and the nominal wall thickness t of the pipe body is 12.7mm, satisfying the formula requirements of h1 + h2 = (80%~100%)t and h1 = (40%~50%)t. The upper clipping loss length Ls=100mm, a=0.3mm.

[0029] like Figure 3 As shown, the wall thickness of the pipe end after upsetting is T, the nominal wall thickness of the pipe body is t, h1 is the height of the inner shoulder of the male end, and h2 is the height of the outer shoulder of the female end. During the thread tightening process, a sufficiently large tightening torque needs to be applied to ensure that the inner and outer shoulders of the male and female ends are tightly pressed together and a certain amount of interference is generated. This is a necessary condition to ensure the airtightness of the joint. By controlling h1 and h2, the over-torque capacity is improved, avoiding thread sticking and damage to the sealing surface caused by over-torque. The double sealing surfaces can effectively ensure the penetration of internal and external pressures and ensure the airtight performance under alternating loads.

[0030] Currently, shale gas development generally involves using large-angle horizontal wells combined with volumetric fracturing. In well types with a large vertical drop, the horizontal section length typically exceeds 2500 meters. Conventional casing running methods are insufficient to achieve the required depth, so a rotating casing string method is usually used for casing installation.

[0031] For 139.7*12.7mm upset sleeves, the optimal torque for conventional installation is between 12000NM. Through over-torsion testing, the yield torque reaches 48000NM. For sleeve installation, if the rotational torque does not exceed 48000NM, the joint sealing performance can be guaranteed without damage.

[0032] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept, and these all fall within the protection scope of the present invention.

Claims

1. A high-torsion-resistant sleeve gas-tight threaded joint structure, comprising a male threaded joint (7) and a female threaded joint (1), wherein the male threaded joint (7) is disposed on the upset portion of the male sleeve end, and the female threaded joint (1) is disposed on the upset portion of the female sleeve end, characterized in that, The male threaded connector (7) includes a male thread (12), a male inner sealing surface (9), a male outer sealing surface (11), a male inner shoulder (8), and a male outer shoulder (10). The female threaded connector (1) includes a female thread (6), a female inner sealing surface (3), a female outer sealing surface (5), a female inner shoulder (2), and a female outer shoulder (4). The male threaded connector (7) and the female threaded connector (1) are symmetrical structures, and their parameters simultaneously satisfy the following formula: T = h1 + h2 + Ls * τ; (Wd) / 2=T; h1 + h2 = (80%~100%)t; h1 = (40%~50%)t; In the formula, W is the outer diameter of the upset pipe end, d is the inner diameter of the upset pipe end, h1 is the inner shoulder height of the male end, h2 is the outer shoulder height of the female end, t is the nominal wall thickness of the sleeve, T is the wall thickness of the sleeve end after upset, Ls is the thread loss length, and τ is the thread taper.

2. The high-torsion-resistance sleeve gas-tight threaded joint structure according to claim 1, characterized in that, The male end thread (12) and the female end thread (6) are trapezoidal threads with a thread taper range of 1:20 to 1:

8.

3. The high-torsion-resistance sleeve gas-tight threaded joint structure according to claim 1, characterized in that, The pitch of the male end thread (12) and the female end thread (6) is 3.63mm~6.35mm.

4. The high-torsion-resistant sleeve gas-tight threaded joint structure according to claim 1, characterized in that, The tooth height of the male end thread (12) and the female end thread (6) is 0.8~1.575mm.

5. The high-torsion-resistant sleeve gas-tight threaded joint structure according to claim 1, characterized in that, The outer diameter of the upset portion at the end of the casing is 1.03 to 1.05 times the outer diameter of the casing.

6. The high-torsion-resistant sleeve gas-tight threaded joint structure according to claim 1, characterized in that, For the female threaded connector (1), the thread loss length is a negative tolerance (0, -a); for the male threaded connector (7), the thread loss length is a positive tolerance (+a, 0), where 0 <a≤0.5。 7. The high-torsion-resistance sleeve gas-tight threaded joint structure according to claim 1, characterized in that, The male end inner shoulder (8) and the female end inner shoulder (2) have an angle of 75°~90° with the axis, and the male end outer shoulder (10) and the female end outer shoulder (4) have an angle of 75°~90° with the axis direction.

8. The high-torsion-resistant sleeve gas-tight threaded joint structure according to claim 1, characterized in that, The taper of the inner sealing surface (3) of the female end, the outer sealing surface (5) of the female end, the inner sealing surface (9) of the male end, and the outer sealing surface (11) of the male end along the axis of the pipe body is 1:20~1:8.

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