Threaded joint for thin-wall oil casing

Abstract

The invention discloses a thin-wall oil casing threaded connector which comprises a pipe body, a coupling is arranged on the pipe body in a matched mode, an external thread of a negative-angle heptagon structure is formed in the outer wall of the pipe body, an internal thread of a negative-angle hexagon structure is formed in the inner wall of the coupling, the external thread is in interference fit with the internal thread, and an external sealing structure is arranged on the outer wall, close to the end, of the pipe body. The coupling is provided with an inner sealing structure, and the outer sealing structure is in interference fit with the inner sealing structure. According to the thin-wall oil casing threaded connector, a small-sliding-distance, anti-thread-gluing, high-sealing-interference and low-thread-interference structure is adopted, the rotating sliding distance of a sealing face in the screwing process of an upper buckle is reduced, the sealing and anti-thread-gluing capacity is improved while sealing is achieved, and the technological requirements of high-pressure operation such as fracturing of long horizontal wells of oil fields are met; the problem of high-pressure leakage of a special thread of a thin-wall oil casing in an oil field is solved.

Description

Technical Field

[0001] This invention belongs to the technical field of oil casing pipe joints, and relates to thin-walled oil casing pipe threaded joints. Background Technology

[0002] In recent years, with the continuous decrease in high-yield oil and gas wells, oil extraction has gradually shifted towards low-permeability or even tight oil and gas reservoirs. The proportion of complex wells such as deep wells, ultra-deep wells, horizontal wells, extended reach wells, and high-temperature, high-pressure wells is increasing. In the development of unconventional oil and gas such as shale oil and gas, well conditions are becoming increasingly demanding, placing higher requirements on the performance of oil and gas tubing strings. In oilfield development, fracturing technology is an important production enhancement technique and a crucial measure to increase oil production. To increase single-well production, oilfields often employ long horizontal well processes. To maximize reservoir stimulation and improve recovery rates, oilfields are now increasingly using large-volume, multi-stage fracturing processes with higher fracturing pressures, some exceeding 100 MPa, and an increasing number of fracturing operations, sometimes exceeding 30. The high-pressure, multi-stage fracturing of long horizontal wells places higher demands on the tubing string, especially the joints, in terms of their resistance to internal pressure, which can easily lead to leaks at the joints and tubing string failure. In addition, the difficulty in running long horizontal well casing has led to the increasing adoption of new top-drive rotary casing running technology in oilfields. This technology can easily result in joint shoulder deformation and failure under high torque and compression, causing wellbore obstruction. At the same time, due to pressure on oil and gas extraction costs and the need to improve quality and efficiency, oilfields are increasingly using thin-walled special threaded tubing strings. High-pressure leakage is causing more tubing string failures in oilfields.

[0003] Existing technologies suffer from poor torque resistance of joints and high-pressure leakage at tubing connections. Summary of the Invention

[0004] The purpose of this invention is to provide a thin-walled oil casing threaded joint, which solves the problems of poor torque resistance and high-pressure leakage at the pipe connection in the prior art.

[0005] The technical solution adopted in this invention is a thin-walled oil casing threaded joint, including a pipe body, a coupling provided with the pipe body, an external thread with a negative angle hexagonal structure on the outer wall of the pipe body, an internal thread with a negative angle hexagonal structure on the inner wall of the coupling, the external thread and the internal thread are interference fit, an external sealing structure is provided on the outer wall of the pipe body near the end, an internal sealing structure is provided on the coupling, and the external sealing structure and the internal sealing structure are interference fit.

[0006] The invention is further characterized by:

[0007] The angle formed by the pitch diameter of the external thread and the axis of the pipe body The angle is 1.49°-1.69°; the angle formed by the pitch diameter of the internal thread and the axis of the coupling. The angle is 1.49°-1.69°; the interference fit between the external and internal threads is 0.1mm-0.3mm; the interference fit between the external and internal sealing structures is 0.3mm-0.8mm.

[0008] When the wall thickness of the pipe body is d≥12.7mm, the tooth height H1 of the external thread is 1.7mm-1.9mm, the tooth height H2 of the upper tooth of the external thread is 0.85mm-0.95mm, and the tooth height H3 of the lower tooth of the external thread is 0.85mm-0.95mm.

[0009] If the wall thickness of the pipe body is 9.17mm≤d<12.7mm, the tooth height of the external thread is 1.5mm-1.7mm, the tooth height of the upper tooth of the external thread is 0.75mm-0.85mm, and the tooth height of the lower tooth of the external thread is 0.75mm-0.85mm.

[0010] If the wall thickness of the pipe body is 6.45mm≤d<9.17mm, the tooth height of the external thread is 0.96mm-1.06mm, the tooth height of the upper tooth of the external thread is 0.48mm-0.53mm, and the tooth height of the lower tooth of the external thread is 0.48mm-0.53mm.

[0011] If the wall thickness of the pipe is d < 6.45 mm, the tooth height of the external thread is 0.8 mm - 0.9 mm, the tooth height of the upper tooth of the external thread is 0.4 mm - 0.45 mm, and the tooth height of the lower tooth of the external thread is 0.4 mm - 0.45 mm.

[0012] The wall thickness of the pipe body is d≥12.7mm. The tooth height H4 of the internal thread on the coupling corresponding to the external thread on the pipe body is 1.8mm-2mm, the tooth height H5 of the upper tooth of the internal thread is 0.85mm-0.95mm, and the tooth height H6 of the lower tooth of the internal thread is 0.95mm-1.05mm.

[0013] If the wall thickness of the pipe body is 9.17mm≤d<12.7mm, the tooth height H4 of the internal thread on the coupling corresponding to the external thread on the pipe body is 1.6mm-1.8mm, the upper tooth height of the internal thread is 0.75mm-0.85mm, and the lower tooth height of the internal thread is 0.85mm-0.95mm.

[0014] If the wall thickness of the pipe body is 6.45mm≤d<9.17mm, the tooth height H4 of the internal thread on the coupling corresponding to the external thread on the pipe body is 1.06mm-1.16mm, the upper tooth height of the internal thread is 0.48mm-0.53mm, and the lower tooth height of the internal thread is 0.58mm-0.63mm.

[0015] If the wall thickness of the pipe body is d < 6.45 mm, the tooth height H4 of the internal thread on the coupling corresponding to the external thread on the pipe body is 0.89 mm - 1 mm, the upper tooth height of the internal thread is 0.4 mm - 0.45 mm, and the lower tooth height of the internal thread is 0.49 mm - 0.55 mm.

[0016] The external thread includes several sequentially connected external thread guide surfaces, external upper thread perpendicularity adjustment surfaces, guide surface crest surface arcs, external thread crest surfaces, crest surface bevel surface arcs, interference upper thread protection bevel surfaces, bevel surface right angle bearing surface arcs, external thread right angle bearing surface, external thread bearing surface, bearing surface root surface arcs, external thread root surface, and external thread root surface guide surface arcs;

[0017] The angle formed by the guide surface of the external thread and the pitch diameter of the external thread. The angle between the outer upper thread perpendicularity adjustment surface and the mean diameter of the external thread is 101.59°-101.79°. The angle between the right-angle bearing surface of the external thread and the pitch diameter of the external thread is 121.59°-121.79°. The angle between the bearing surface of the external thread and the pitch diameter of the external thread is 88.21°-88.41°. The range is 85.21°–85.41°.

[0018] The radius R1 of the guide surface crest arc is 0.3mm-0.4mm; the radius R5 of the beveled surface arc is 0.2mm-0.3mm; the radius R4 of the right-angle bearing surface arc is 0.2mm-0.3mm; the radius R3 of the bearing surface root arc is 0.2mm-0.3mm; and the radius R2 of the guide surface arc of the external thread root is 0.3mm-0.4mm.

[0019] The internal thread includes several sequentially connected internal thread guide surfaces, guide surface root arc, internal thread root surface, root surface bearing surface arc, internal thread bearing surface, internal thread right angle bearing surface, right angle bearing surface crest arc, internal thread crest surface, crest thread verticality adjustment surface arc, and internal upper thread verticality adjustment surface.

[0020] The angle formed by the guide surface of the internal thread and the pitch diameter of the internal thread. The angle between the bearing surface of the internal thread and the pitch diameter of the internal thread is 78.21°-78.41°. The angle between the right-angle bearing surface of the internal thread and the pitch diameter of the internal thread is 86.8°-87°. The angle between the inner upper thread perpendicularity adjustment surface and the mean diameter of the internal thread is 88.21°-88.41°. The range is 58.21°–58.41°.

[0021] The radius R9 of the guide surface bottom arc is 0.3mm-0.4mm, the radius R8 of the bottom bearing surface arc is 0.2mm-0.3mm, the radius R7 of the right-angle bearing surface top arc is 0.2mm-0.3mm, and the radius R6 of the top perpendicularity adjustment surface arc is 0.3mm-0.4mm.

[0022] The internal sealing structure includes a central hole surface, a central hole surface shoulder arc, an internal sealing shoulder surface, a shoulder surface sealing surface arc, a sealing surface, and a sealing cylindrical surface connected in sequence. The sealing cylindrical surface is an annular groove with a rectangular cross-section set on the inner wall of the coupling.

[0023] The angle between the inner sealing shoulder surface and the axis of the coupling The angle between the sealing surface and the axis of the coupling is 75°-77°. The angle is 14.1°-14.3°; the radius R12 of the sealing surface arc of the shoulder is 0.6mm-0.7mm;

[0024] The length L4 of the central hole is 13.0mm-19.0mm, the thickness H9 of the inner sealing shoulder is 3.8mm-5.1mm, and the length L3 of the sealing surface projected onto the coupling axis is 4.0mm-13.2mm.

[0025] The external sealing structure includes, in sequence, an inner diameter reduction surface shoulder arc, an outer sealing shoulder, a shoulder main sealing cone arc, a first sealing cone, a main sealing arc, a second sealing cone, and an inner diameter reduction surface; the inner diameter reduction surface shoulder arc, the outer sealing shoulder, the shoulder main sealing cone arc, and the first sealing cone are located on the end face of the pipe body, while the main sealing arc, the second sealing cone, and the inner diameter reduction surface are located on the outer wall of the pipe body;

[0026] The angle between the first sealing cone surface and the axis of the pipe body The angle between the outer sealing shoulder surface and the axis of the pipe body is 14.1°-14.3°. The angle between the second sealing cone surface and the axis of the pipe body is 75°-77°. The range is 1.49°–1.69°.

[0027] The thickness H7 of the outer sealing shoulder is less than the thickness H9 of the inner sealing shoulder, and the difference H10 between H7 and H9 is 0.3mm-0.6mm. The thickness H7 of the outer sealing shoulder is greater than 3.3mm. The radial distance H8 between the second sealing cone and the inner diameter reduction surface and the root surface of the external thread closest to the end on the pipe body is 0.39mm-0.46mm.

[0028] The radius R10 of the main sealing cone arc on the shoulder surface is 0.7mm-0.8mm, the length L1 of the first sealing cone projection in the axial direction of the pipe body is 3.0mm-5.8mm, the radius R11 of the main sealing arc is 5mm-8mm, and the length L2 of the second sealing cone projection in the axial direction of the pipe body is 3.1mm-8.0mm.

[0029] The beneficial effects of this invention are as follows: The pipe body and coupling of this invention are interference-fitted, and adopt a structure with small sliding distance, anti-sticking, high sealing interference, and low thread interference. This reduces the rotational sliding distance of the sealing surface during the tightening process, improving the sealing and high-pressure resistance while preventing sticking. The threaded part only needs to bear the joint connection strength requirements. The low thread interference design maximizes the protection of the joint's sealing ability and ensures that the joint does not stick not only during three tightening and two loosening operations in the production workshop, but also during repeated tightening and loosening on the drilling platform. The sealing structure adopts a high interference design, ensuring that the gas sealing efficiency reaches VME95% under combined loads such as tension / compression, internal / external pressure, bending, and high temperature. This meets the high-pressure operation requirements of oilfield long horizontal well fracturing and solves the high-pressure leakage problem of special threads in thin-walled oil casing in the oilfield. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the thin-walled oil sleeve threaded joint of the present invention;

[0031] Figure 2 This is a schematic diagram of the external thread structure in this invention;

[0032] Figure 3 This is a schematic diagram of the structural parameters of the external thread in this invention;

[0033] Figure 4 This is a schematic diagram of the internal thread structure in this invention;

[0034] Figure 5 This is a schematic diagram of the structural parameters of the internal thread in this invention;

[0035] Figure 6 This is a schematic diagram of the internal sealing structure in this invention;

[0036] Figure 7 This is a schematic diagram of the structural parameters of the inner sealing structure in this invention;

[0037] Figure 8 This is a schematic diagram of the external sealing structure in this invention;

[0038] Figure 9 This is a schematic diagram of the structural parameters of the outer sealing structure in this invention;

[0039] Figure 10 This is a schematic diagram of the threaded connection between the tube body and the coupling in this invention;

[0040] Figure 11 for Figure 10 Enlarged structural diagram at point A;

[0041] Figure 12 for Figure 10 A magnified structural diagram at point B in the middle.

[0042] In the diagram, 1. Pipe body; 2. External thread; 201. External thread guide surface; 202. External upper thread perpendicularity adjustment surface; 203. Guide surface crest arc; 204. External thread crest surface; 205. Chamfered surface arc of crest surface; 206. Interference fit upper thread protection chamfered surface; 207. Chamfered surface right angle bearing surface arc; 208. External thread right angle bearing surface; 209. External thread bearing surface; 2010. Bearing surface root arc; 2011. External thread root surface; 2012. External thread root surface guide surface arc; 3. Coupling; 4. Internal thread; 401. Internal thread guide surface; 402. Guide surface root arc; 403. Internal thread root surface; 404. Root surface bearing surface arc; 405. Internal thread... Thread bearing surface; 406, right-angle bearing surface of internal thread; 407, right-angle bearing surface tooth crest arc; 408, internal thread tooth crest surface; 409, tooth crest verticality adjustment surface arc; 4010, inner upper thread verticality adjustment surface; 5, external sealing structure; 501, inner diameter reduction surface; 502, inner diameter reduction surface shoulder arc; 503, external sealing shoulder surface; 504, shoulder surface main sealing cone arc; 505, first sealing cone surface; 506, main sealing arc; 507, second sealing cone surface; 6, internal sealing structure; 601, central hole surface; 602, central hole surface shoulder arc; 603, internal sealing shoulder surface; 604, shoulder surface sealing arc; 605, sealing surface; 606, sealing cylindrical surface. Detailed Implementation

[0043] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0044] Thin-walled oil sleeve threaded joint, such as Figure 1 As shown, the device includes a pipe body 1, which is fitted with a coupling 3. The outer wall of the pipe body 1 has an external thread 2 with a negative angle hexagonal structure, and the inner wall of the coupling 3 has an internal thread 4 with a negative angle hexagonal structure. The external thread 2 and the internal thread 4 are interference-fitted. The outer wall of the pipe body 1 near the end has an external sealing structure 5, and the coupling 3 has an internal sealing structure 6. The external sealing structure 5 and the internal sealing structure 6 are interference-fitted.

[0045] The angle formed by the mean diameter of external thread 2 and the axis of pipe body 1 The external thread 2 features a tapered design with an angle of 1.49°-1.69° to ensure effective thread length and connection strength. The internal thread 4 has an angle formed between its pitch diameter and the axis of the coupling 3. The internal thread 4 has a tapered design with a 1.49°-1.69° angle, which matches the tapered design of the external thread 2 to ensure the connection strength of the joint; the interference fit between the external thread 2 and the internal thread 4 is 0.1mm-0.3mm, and the low interference fit design between the external thread 2 and the internal thread 4 ensures reasonable and easily identifiable shoulder torque; the interference fit between the external sealing structure 5 and the internal sealing structure 6 is 0.3mm-0.8mm.

[0046] Based on the wall thickness of pipe body 1, the tooth height of external thread 2 is designed in stages. When the wall thickness of pipe body 1 is d≥12.7mm, the tooth height H1 of external thread 2 is 1.7mm-1.9mm to enhance the torsional resistance of the threaded pipe with a large wall thickness. The tooth height H2 of the upper tooth of external thread 2 is 0.85mm-0.95mm, and the tooth height H3 of the lower tooth of external thread 2 is 0.85mm-0.95mm. If the wall thickness of pipe body 1 is 9.17mm≤d<12.7mm, the tooth height of external thread 2 is 1.5mm-1.7mm, the tooth height of the upper tooth of external thread 2 is 0.75mm-0.85mm, and the tooth height of the lower tooth of external thread 2 is 0.75mm-0.85mm. The high and low tooth height structure improves the accuracy of the pitch diameter interference design. If the wall thickness of the pipe body 1 is 6.45mm≤d<9.17mm, the tooth height of the external thread 2 is 0.96mm-1.06mm, the upper tooth height of the external thread 2 is 0.48mm-0.53mm, and the lower tooth height of the external thread 2 is 0.48mm-0.53mm. If the wall thickness of the pipe body 1 is d<6.45mm, the tooth height of the external thread 2 is 0.8mm-0.9mm, the upper tooth height of the external thread 2 is 0.4mm-0.45mm, and the lower tooth height of the external thread 2 is 0.4mm-0.45mm. The graded tooth height structure of the external thread 2 improves the effective thread length and connection strength.

[0047] Based on the wall thickness of pipe body 1, the tooth height of internal thread 4 is designed in stages. When the wall thickness of pipe body 1 is d≥12.7mm, the tooth height H4 of internal thread 4 on coupling 3 corresponding to external thread 2 on pipe body 1 is 1.8mm-2mm, the upper tooth height H5 of internal thread 4 is 0.85mm-0.95mm, and the lower tooth height H6 of internal thread 4 is 0.95mm-1.05mm. The tooth crest of external thread 2 and the tooth root of internal thread 4 are clearance-fitted to improve the thread's anti-sticking ability. If the wall thickness of pipe body 1 is 9.17mm≤d<12.7mm, the tooth height H4 of internal thread 4 on coupling 3 corresponding to external thread 2 on pipe body 1 is 1.6mm-1.8mm, and the upper tooth height of internal thread 4 is 0.75mm-0.85mm. m, the lower tooth height of the internal thread 4 is 0.85mm-0.95mm; if the wall thickness of the pipe body 1 is 6.45mm≤d<9.17mm, the tooth height H4 of the internal thread 4 on the coupling 3 corresponding to the external thread 2 on the pipe body 1 is 1.06mm-1.16mm, the upper tooth height of the internal thread 4 is 0.48mm-0.53mm, and the lower tooth height of the internal thread 4 is 0.58mm-0.63mm; if the wall thickness of the pipe body 1 is d<6.45mm, the tooth height H4 of the internal thread 4 on the coupling 3 corresponding to the external thread 2 on the pipe body 1 is 0.89mm-1mm, the upper tooth height of the internal thread 4 is 0.4mm-0.45mm, and the lower tooth height of the internal thread 4 is 0.49mm-0.55mm.

[0048] like Figure 2 As shown, the external thread 2 includes several external thread guide surfaces 201, external upper thread perpendicularity adjustment surfaces 202, guide surface tooth crest arc 203, external thread tooth crest surface 204, tooth crest surface bevel arc 205, interference upper thread protection bevel surface 206, bevel surface right angle bearing surface arc 207, external thread right angle bearing surface 208, external thread bearing surface 209, bearing surface tooth root arc 2010, external thread tooth root surface 2011, and external thread tooth root surface guide surface arc 2012, which are connected in sequence.

[0049] like Figure 3 As shown, the angle formed by the external thread guide surface 201 and the mean diameter of the external thread 2 is... The angle is 101.59°-101.79° to improve the joint's compression resistance. The angle formed by the outer upper thread perpendicularity adjustment surface 202 and the mean diameter line of the external thread 2 is [not specified]. The angle is 121.59°-121.79° to ensure the alignment of the tubing string and reduce the risk of damage to the guide surface during the threading process. The angle formed by the right-angle bearing surface 208 of the external thread and the pitch diameter of the external thread 2 is... The angle is 88.21°-88.41°, which reduces the machining difficulty of the bearing surface on the inner wall and improves the machining efficiency of the bearing surface on the inner wall. The angle formed by the bearing surface 209 of the external thread and the mean diameter of the external thread 2 is... The radius of the guide surface arc 203 is 0.3mm-0.4mm; the radius of the beveled surface arc 205 is 0.2mm-0.3mm; the radius of the right-angle bearing surface arc 207 is 0.2mm-0.3mm; the radius of the bearing surface arc 2010 is 0.2mm-0.3mm; the radius of the guide surface arc 2012 is 0.3mm-0.4mm; the structural design of the thread transition arc ensures that the internal thread 4 and the external thread 2 do not stick together after multiple turns.

[0050] like Figure 4 As shown, the internal thread 4 includes several internal thread guide surfaces 401, guide surface tooth root arc 402, internal thread tooth root surface 403, tooth root surface bearing surface arc 404, internal thread bearing surface 405, internal thread right angle bearing surface 406, right angle bearing surface tooth crest arc 407, internal thread tooth crest surface 408, tooth crest verticality adjustment surface arc 409, and internal upper thread verticality adjustment surface 4010 connected in sequence.

[0051] like Figure 5 As shown, the angle formed by the internal thread guide surface 401 and the pitch diameter of the internal thread 4 is... The angle is 78.21°-78.41°, which improves the joint's compression resistance. The angle formed by the internal thread bearing surface 405 and the pitch diameter of the internal thread 4 is... The angle is 86.8°-87° to improve the tensile strength of the joint. The angle formed by the right-angle bearing surface 406 of the internal thread and the pitch diameter of the internal thread 4 is [missing information]. The angle is 88.21°-88.41°, which reduces the machining difficulty of the bearing surface on the inner wall and improves the machining efficiency of the bearing surface on the inner wall. The included angle is formed by the inner upper thread perpendicularity adjustment surface 4010 and the mean diameter line of the internal thread 4. The angle is 58.21°-58.41° to ensure the alignment of the tubing and reduce the risk of damage to the guide surface during the threading process; the radius R9 of the guide surface tooth bottom arc 402 is 0.3mm-0.4mm, the radius R8 of the tooth bottom bearing surface arc 404 is 0.2mm-0.3mm, the radius R7 of the right angle bearing surface tooth top arc 407 is 0.2mm-0.3mm, and the radius R6 of the tooth top threading verticality adjustment surface arc 409 is 0.3mm-0.4mm. The structural design of the thread transition arc ensures that the internal thread 4 and the external thread 2 do not stick together after multiple threading processes.

[0052] like Figure 6As shown, the inner sealing structure 6 includes a central hole surface 601, a central hole surface shoulder arc 602, an inner sealing shoulder surface 603, a shoulder surface sealing surface arc 604, a sealing surface 605, and a sealing cylindrical surface 606 connected in sequence. The sealing cylindrical surface 606 is an annular groove with a rectangular cross-section set on the inner wall of the coupling 3.

[0053] like Figure 7 As shown, the angle between the inner sealing shoulder surface 603 and the axis of the coupling 3 is... The angle is 75°-77°, increasing the contact area of ​​the shoulder and improving its compression resistance. The angle between the sealing surface 605 and the axis of the coupling 3 is [missing information]. The angle is 14.1°-14.3°, increasing the contact length of the sealing surface and improving the sealing stability of the joint; the radius R12 of the shoulder sealing surface arc 604 is 0.6mm-0.7mm, achieving effective fit between the inner and outer shoulders, and the clearance fit at the shoulder arc effectively discharges excess thread grease and ensures sealing contact pressure; the length L4 of the middle hole surface 601 is 13.0mm-19.0mm, reducing the risk of expansion of the field end coupling 3 after factory threading; the thickness H9 of the inner sealing shoulder surface 603 is 3.8mm-5.1mm, improving the compression and external pressure resistance of the thin-walled oil sleeve threaded joint; the length L3 of the sealing surface 605 projected onto the axial direction of the coupling 3 is 4.0mm-13.2mm.

[0054] like Figure 8 As shown, the outer sealing structure 5 includes an inner diameter reduction surface shoulder arc 502, an outer sealing shoulder surface 503, a shoulder surface main sealing cone arc 504, a first sealing cone surface 505, a main sealing arc 506, a second sealing cone surface 507, and an inner diameter reduction surface 501 connected in sequence; the inner diameter reduction surface shoulder arc 502, the outer sealing shoulder surface 503, the shoulder surface main sealing cone arc 504, and the first sealing cone surface 505 are located on the end face of the pipe body 1, while the main sealing arc 506, the second sealing cone surface 507, and the inner diameter reduction surface 501 are located on the outer wall of the pipe body 1;

[0055] like Figure 9 As shown, the angle between the first sealing cone surface 505 and the axis of the pipe body 1 is... The angle is 14.1°-14.3°, increasing the contact length of the sealing surface and improving the sealing stability of the joint. This angle is the angle between the outer sealing shoulder surface 503 and the axis of the pipe body 1. The angle is 75°-77°, increasing the contact area of ​​the shoulder and improving its compression resistance. The angle between the second sealing cone surface 507 and the axis of the pipe body 1 is [not specified]. The angle is 1.49°-1.69°, consistent with the thread taper, effectively preventing the thread cutter from scratching the first sealing surface during thread machining; the thickness H7 of the outer sealing shoulder surface 503 is less than the thickness H9 of the inner sealing shoulder surface 603, and the difference H10 between H7 and H9 is 0.3mm-0.6mm. After threading, the inner hole of the pipe end and the middle hole of the coupling are flush, and the sealing surface is not damaged under high pressure fluid. The thickness H7 of the outer sealing shoulder surface 503 is greater than 3.3mm, improving the compression resistance and external pressure resistance of the thin-walled special threaded joint; the radial distance H8 between the connection between the second sealing cone surface 507 and the inner diameter reduction surface 501 and the outer thread root surface 2011 closest to the port on the pipe body 1 is 0.39mm-0.46mm. This invention addresses the issues of insufficient effective thread length in the circumferential direction and excessive black thread tolerance caused by the elliptical shape of thin-walled oil casing threads. The radius R10 of the main sealing cone arc 504 on the shoulder surface is 0.7mm-0.8mm, achieving effective fit between the inner and outer shoulders. The clearance fit at the shoulder arc effectively removes excess thread grease, ensuring sealing contact pressure. The length L1 of the first sealing cone 505 projected onto the axial direction of the pipe body 1 is 3.0mm-5.8mm, and the radius R11 of the main sealing arc 506 is 5mm-8mm. The sealing contact morphology is saddle-shaped, preventing plastic deformation of the parabolic contact morphology at the maximum contact pressure position. The length L2 of the second sealing cone 507 projected onto the axial direction of the pipe body 1 is 3.1mm-8.0mm.

[0056] like Figure 10 As shown, the pipe body 1 is embedded in the coupling 3, the external thread 2 and the internal thread 4 are in a low interference fit, and the external sealing structure 5 and the internal sealing structure 6 are in a high interference fit.

[0057] like Figure 11 As shown, the external thread guide surface 201 is in close contact with the internal thread guide surface 401, the external thread crest surface 204 is in contact with the internal thread root surface 403, the external thread right angle bearing surface 208 is in contact with the internal thread bearing surface 405, and the external thread root surface 2011 is in contact with the internal thread crest surface 408.

[0058] like Figure 12 As shown, the outer sealing shoulder surface 503 and the inner sealing shoulder surface 603 are tightly fitted together, the main sealing cone arc 504 of the shoulder surface is embedded in the sealing surface arc 604 of the shoulder surface, and the second sealing cone surface 507 is tightly fitted with the sealing surface 605.

[0059] In this invention, the pipe body 1 and the coupling 3 are interference-fitted, employing a small sliding distance, anti-sticking, high sealing interference, and low thread interference structure. The thread interference and sealing interference work together, with a diameter thread interference of 0.1mm-0.3mm and a diameter sealing interference of 0.3mm-0.8mm. The sealing sliding distance is ≤1.5mm, reducing the rotational sliding distance of the sealing surface during the tightening process, improving the sealing and high-pressure resistance while preventing sticking. In this invention, the design is based on the wall thickness of the pipe body 1, with tooth height, thread length, and pitch diameter as graded components. The connection strength is determined according to the pipe body strength. The design incorporates a 1.1x angle to maximize shoulder thickness, addressing the sealing instability issues encountered when using special threads on thin-walled oil casing pipes in oilfield applications. The end of pipe body 1 employs a structure with small tooth height, short thread length, and a median diameter close to the shoulder, while ensuring thread connection efficiency. The sealing structure of this invention adopts a design of small conical surface + large arc + small conical surface / small conical surface, increasing the sealing contact length even with a significant reduction in threaded sealing pressure. Under external pressure load, the sealing surface contact length is ≥0.9mm, ensuring overall sealing capacity and stability.

[0060] The thread structure adopts a tapered structure parallel to the pipe string axis. The external thread 2 adopts a negative angle heptagonal design, which adds an external upper thread verticality adjustment surface 202, an interference upper thread protection bevel surface 206, and a segmented bearing surface structure compared to conventional threads. The internal thread 4 adopts a negative angle hexagonal design, which adds an internal upper thread verticality adjustment surface 4010 and a segmented bearing surface structure compared to conventional threads. The internal upper thread verticality adjustment surface 4010 and the external upper thread verticality adjustment surface 202 can effectively solve the problem of incorrect upper threading caused by non-vertical and misaligned pipe string, while speeding up the on-site upper threading speed and saving valuable time costs in oilfield drilling and completion. The interference upper thread protection bevel surface 206 can effectively ensure that the thread is not damaged or stuck during the three upper and two lower processes. The segmented bearing surface structure, which adds a right-angle bearing surface, effectively improves thread processing efficiency and yield while ensuring joint efficiency.

[0061] The ends of pipe body 1 are upsetting, reducing diameter, and heat treatment to reduce the inner diameter of the ends while keeping the residual stress controllable. For high-grade oil casing, stainless steel, titanium alloy and other alloy steel materials, and large-diameter casing, pipe end upsetting and heat treatment are used. For ordinary small and medium-diameter API steel grades, pipe end reducing is used. However, when the reduction exceeds 3%, stress relief annealing and other pipe end heat treatments must be performed.

[0062] This invention effectively ensures the structural and sealing integrity of thin-walled special threaded tubular columns, while solving the problems of poor joint torque resistance and tubular failure caused by high-pressure leakage in existing structures, and improving the yield and processing efficiency in the threaded sealing process.

[0063] Example 1

[0064] This embodiment proposes a thin-walled oil sleeve threaded joint, such as... Figure 1 As shown, the device includes a pipe body 1, which is fitted with a coupling 3. The outer wall of the pipe body 1 has an external thread 2 with a negative angle hexagonal structure, and the inner wall of the coupling 3 has an internal thread 4 with a negative angle hexagonal structure. The external thread 2 and the internal thread 4 are interference-fitted. An external sealing structure 5 is located on the outer wall of the pipe body 1 near its end, and an internal sealing structure 6 is located on the coupling 3. The external sealing structure 5 and the internal sealing structure 6 are interference-fitted. The angle formed by the mean diameter line of the external thread 2 and the axis of the pipe body 1 is... The angle is 1.49; the angle formed by the pitch diameter of the internal thread 4 and the axis of the coupling 3. The interference fit between external thread 2 and internal thread 4 is 0.1 mm; the interference fit between external sealing structure 5 and internal sealing structure 6 is 0.3 mm. When the wall thickness of pipe body 1 is d≥12.7 mm, the tooth height H1 of external thread 2 is 1.7 mm, the upper tooth height H2 of external thread 2 is 0.85 mm, and the lower tooth height H3 of external thread 2 is 0.85 mm; when the wall thickness of pipe body 1 is d≥12.7 mm, the tooth height H4 of internal thread 4 on coupling 3 corresponding to external thread 2 on pipe body 1 is 1.8 mm, the upper tooth height H5 of internal thread 4 is 0.85 mm, and the lower tooth height H6 of internal thread 4 is 0.95 mm.

[0065] like Figure 2 As shown, the external thread 2 includes several sequentially connected external thread guide surfaces 201, external upper thread perpendicularity adjustment surfaces 202, guide surface crest arc 203, external thread crest surface 204, crest surface bevel arc 205, interference fit upper thread protection bevel surface 206, bevel surface right angle bearing surface arc 207, external thread right angle bearing surface 208, external thread bearing surface 209, bearing surface root arc 2010, external thread root surface 2011, and external thread root surface guide surface arc 2012; as shown Figure 3 As shown, the angle formed by the external thread guide surface 201 and the mean diameter of the external thread 2 is... The angle is 101.59°, which is the angle formed by the outer upper thread perpendicularity adjustment surface 202 and the mean diameter line of the external thread 2. The angle is 121.59°, which is the angle formed by the right-angle bearing surface 208 of the external thread and the pitch diameter of the external thread 2. The angle is 88.21°, which is the angle formed by the bearing surface 209 of the external thread and the pitch diameter of the external thread 2. The radius of the guide surface arc 203 is 0.3 mm; the radius of the beveled surface arc 205 is 0.2 mm; the radius of the right-angle bearing surface arc 207 is 0.2 mm; the radius of the bearing surface arc 2010 is 0.2 mm; and the radius of the guide surface arc 2012 is 0.3 mm.

[0066] like Figure 4 As shown, the internal thread 4 includes several sequentially connected internal thread guide surfaces 401, guide surface root arc 402, internal thread root surface 403, root surface bearing arc 404, internal thread bearing surface 405, internal thread right-angle bearing surface 406, right-angle bearing surface crest arc 407, internal thread crest surface 408, crest thread verticality adjustment surface arc 409, and internal thread verticality adjustment surface 4010; Figure 5 As shown, the angle formed by the internal thread guide surface 401 and the pitch diameter of the internal thread 4 is... The angle is 78.21°, which is the angle formed by the pitch diameter of the internal thread bearing surface 405 and the internal thread 4. The angle is 86.8°, which is the angle formed by the right-angle bearing surface 406 of the internal thread and the pitch diameter of the internal thread 4. The angle is 88.21°, which is the angle formed by the inner upper thread perpendicularity adjustment surface 4010 and the mean diameter line of the internal thread 4. The radius of the guide surface tooth bottom arc 402 is 0.3mm, the radius of the tooth bottom bearing surface arc 404 is 0.2mm, the radius of the right angle bearing surface tooth top arc 407 is 0.2mm, and the radius of the tooth top verticality adjustment surface arc 409 is 0.3mm.

[0067] like Figure 6 As shown, the inner sealing structure 6 includes a central hole surface 601, a central hole surface shoulder arc 602, an inner sealing shoulder surface 603, a shoulder surface sealing surface arc 604, a sealing surface 605, and a sealing cylindrical surface 606 connected in sequence. The sealing cylindrical surface 606 is an annular groove with a rectangular cross-section set on the inner wall of the coupling 3; as shown... Figure 7 As shown, the angle between the inner sealing shoulder surface 603 and the axis of the coupling 3 is... The angle is 75°, the angle between the sealing surface 605 and the axis of the coupling 3. The radius R12 of the sealing surface arc 604 of the shoulder surface is 0.6mm; the length L4 of the central hole surface 601 is 13.0mm; the thickness H9 of the inner sealing shoulder surface 603 is 3.8mm; and the length L3 of the sealing surface 605 projected onto the coupling 3 axis is 4mm.

[0068] like Figure 8 As shown, the outer sealing structure 5 includes an inner diameter reduction surface shoulder arc 502, an outer sealing shoulder surface 503, a shoulder surface main sealing cone arc 504, a first sealing cone surface 505, a main sealing arc 506, a second sealing cone surface 507, and an inner diameter reduction surface 501 connected in sequence; the inner diameter reduction surface shoulder arc 502, the outer sealing shoulder surface 503, the shoulder surface main sealing cone arc 504, and the first sealing cone surface 505 are located on the end face of the pipe body 1, while the main sealing arc 506, the second sealing cone surface 507, and the inner diameter reduction surface 501 are located on the outer wall of the pipe body 1; as Figure 9 As shown, the angle between the first sealing cone surface 505 and the axis of the pipe body 1 is... The angle between the outer sealing shoulder surface 503 and the axis of the tube body 1 is 14.1°. The angle between the second sealing cone surface 507 and the axis of the pipe body 1 is 75°. The angle is 1.49°; the thickness H7 of the outer sealing shoulder surface 503 is less than the thickness H9 of the inner sealing shoulder surface 603, and the difference H10 between H7 and H9 is 0.3mm, while the thickness H7 of the outer sealing shoulder surface 503 is greater than 3.3mm; the radial distance H8 between the connection between the second sealing cone surface 507 and the inner diameter reduction surface 501 and the external thread root surface 2011 closest to the port on the pipe body 1 is 0.39mm; the radius R10 of the arc 504 of the main sealing cone surface of the shoulder surface is 0.7mm, the length L1 of the projection of the first sealing cone surface 505 onto the axial direction of the pipe body 1 is 3.0mm, the radius R11 of the main sealing arc 506 is 5mm, and the length L2 of the projection of the second sealing cone surface 507 onto the axial direction of the pipe body 1 is 3.1mm.

[0069] Example 2

[0070] This embodiment proposes a thin-walled oil sleeve threaded joint, such as... Figure 1 As shown, the device includes a pipe body 1, which is fitted with a coupling 3. The outer wall of the pipe body 1 has an external thread 2 with a negative angle hexagonal structure, and the inner wall of the coupling 3 has an internal thread 4 with a negative angle hexagonal structure. The external thread 2 and the internal thread 4 are interference-fitted. An external sealing structure 5 is located on the outer wall of the pipe body 1 near its end, and an internal sealing structure 6 is located on the coupling 3. The external sealing structure 5 and the internal sealing structure 6 are interference-fitted. The angle formed by the mean diameter line of the external thread 2 and the axis of the pipe body 1 is... The angle is 1.69°; the angle formed by the pitch diameter of the internal thread 4 and the axis of the coupling 3. The angle is 1.69°; the interference fit between external thread 2 and internal thread 4 is 0.3mm; the interference fit between external sealing structure 5 and internal sealing structure 6 is 0.8mm. When the wall thickness of pipe body 1 is d≥12.7mm, the tooth height H1 of external thread 2 is 1.9mm, the upper tooth height H2 of external thread 2 is 0.95mm, and the lower tooth height H3 of external thread 2 is 0.95mm; when the wall thickness of pipe body 1 is d≥12.7mm, the tooth height H4 of internal thread 4 on coupling 3 corresponding to external thread 2 on pipe body 1 is 2mm, the upper tooth height H5 of internal thread 4 is 0.95mm, and the lower tooth height H6 of internal thread 4 is 1.05mm;

[0071] like Figure 2As shown, the external thread 2 includes several external thread guide surfaces 201, external upper thread perpendicularity adjustment surfaces 202, guide surface tooth crest arc 203, external thread tooth crest surface 204, tooth crest surface bevel arc 205, interference upper thread protection bevel surface 206, bevel surface right angle bearing surface arc 207, external thread right angle bearing surface 208, external thread bearing surface 209, bearing surface tooth root arc 2010, external thread tooth root surface 2011, and external thread tooth root surface guide surface arc 2012, which are connected in sequence.

[0072] like Figure 3 As shown, the angle formed by the external thread guide surface 201 and the mean diameter of the external thread 2 is... The angle is 101.79°, which is the included angle formed by the outer upper thread perpendicularity adjustment surface 202 and the mean diameter line of the external thread 2. The angle is 121.79°, which is the angle formed by the right-angle bearing surface 208 of the external thread and the pitch diameter of the external thread 2. The angle is 88.41°, which is the angle formed by the bearing surface 209 of the external thread and the pitch diameter of the external thread 2. The radius of the guide surface arc 203 is 0.4 mm; the radius of the guide surface arc 205 is 0.3 mm; the radius of the right angle bearing surface arc 207 is 0.3 mm; the radius of the bearing surface arc 2010 is 0.3 mm; and the radius of the guide surface arc 2012 is 0.4 mm.

[0073] like Figure 4 As shown, the internal thread 4 includes several sequentially connected internal thread guide surfaces 401, guide surface root arc 402, internal thread root surface 403, root surface bearing arc 404, internal thread bearing surface 405, internal thread right-angle bearing surface 406, right-angle bearing surface crest arc 407, internal thread crest surface 408, crest thread verticality adjustment surface arc 409, and internal thread verticality adjustment surface 4010; Figure 5 As shown, the angle formed by the internal thread guide surface 401 and the pitch diameter of the internal thread 4 is... The angle is 78.41°, which is the angle formed by the pitch diameter of the internal thread bearing surface 405 and the internal thread 4. The angle is 87°, the angle formed by the right-angle bearing surface 406 of the internal thread and the pitch diameter of the internal thread 4. The angle is 88.41°, which is the angle formed by the inner upper thread perpendicularity adjustment surface 4010 and the mean diameter line of the internal thread 4. The radius of the guide surface tooth bottom arc 402 is 0.4 mm, the radius of the tooth bottom bearing surface arc 404 is 0.3 mm, the radius of the right angle bearing surface tooth top arc 407 is 0.3 mm, and the radius of the tooth top verticality adjustment surface arc 409 is 0.4 mm.

[0074] like Figure 6 As shown, the inner sealing structure 6 includes a central hole surface 601, a central hole surface shoulder arc 602, an inner sealing shoulder surface 603, a shoulder surface sealing surface arc 604, a sealing surface 605, and a sealing cylindrical surface 606 connected in sequence. The sealing cylindrical surface 606 is an annular groove with a rectangular cross-section set on the inner wall of the coupling 3; as shown... Figure 7 As shown, the angle between the inner sealing shoulder surface 603 and the axis of the coupling 3 is... The angle is 77°, the angle between the sealing surface 605 and the axis of the coupling 3. The radius R12 of the sealing surface arc 604 of the shoulder surface is 0.7mm; the length L4 of the central hole surface 601 is 19.0mm; the thickness H9 of the inner sealing shoulder surface 603 is 5.1mm; and the length L3 of the sealing surface 605 projected onto the coupling 3 axis is 13.2mm.

[0075] like Figure 8 As shown, the outer sealing structure 5 includes an inner diameter reduction surface shoulder arc 502, an outer sealing shoulder surface 503, a shoulder surface main sealing cone arc 504, a first sealing cone surface 505, a main sealing arc 506, a second sealing cone surface 507, and an inner diameter reduction surface 501 connected in sequence; the inner diameter reduction surface shoulder arc 502, the outer sealing shoulder surface 503, the shoulder surface main sealing cone arc 504, and the first sealing cone surface 505 are located on the end face of the pipe body 1, while the main sealing arc 506, the second sealing cone surface 507, and the inner diameter reduction surface 501 are located on the outer wall of the pipe body 1; as Figure 9 As shown, the angle between the first sealing cone surface 505 and the axis of the pipe body 1 is... The angle is 14.3°, which is the angle between the outer sealing shoulder surface 503 and the axis of the tube body 1. The angle between the second sealing cone surface 507 and the axis of the pipe body 1 is 77°. The angle is 1.69°; the thickness H7 of the outer sealing shoulder surface 503 is less than the thickness H9 of the inner sealing shoulder surface 603, and the difference H10 between H7 and H9 is 0.6mm, while the thickness H7 of the outer sealing shoulder surface 503 is greater than 3.3mm; the radial distance H8 between the connection between the second sealing cone surface 507 and the inner diameter reduction surface 501 and the external thread root surface 2011 closest to the port on the pipe body 1 is 0.46mm; the radius R10 of the arc 504 of the main sealing cone surface of the shoulder surface is 0.8mm, the length L1 of the projection of the first sealing cone surface 505 onto the axial direction of the pipe body 1 is 5.8mm, the radius R11 of the main sealing arc 506 is 8mm, and the length L2 of the projection of the second sealing cone surface 507 onto the axial direction of the pipe body 1 is 8.0mm.

[0076] Example 3

[0077] This embodiment proposes a thin-walled oil sleeve threaded joint, such as... Figure 1 As shown, the device includes a pipe body 1, which is fitted with a coupling 3. The outer wall of the pipe body 1 has an external thread 2 with a negative angle hexagonal structure, and the inner wall of the coupling 3 has an internal thread 4 with a negative angle hexagonal structure. The external thread 2 and the internal thread 4 are interference-fitted. An external sealing structure 5 is located on the outer wall of the pipe body 1 near its end, and an internal sealing structure 6 is located on the coupling 3. The external sealing structure 5 and the internal sealing structure 6 are interference-fitted. The angle formed by the mean diameter line of the external thread 2 and the axis of the pipe body 1 is... The angle is 1.59°; the angle formed by the pitch diameter of the internal thread 4 and the axis of the coupling 3. The angle is 1.59°; the interference fit between external thread 2 and internal thread 4 is 0.2mm; the interference fit between external sealing structure 5 and internal sealing structure 6 is 0.5mm. When the wall thickness of pipe body 1 is d≥12.7mm, the tooth height H1 of external thread 2 is 1.8mm, the upper tooth height H2 of external thread 2 is 0.90mm, and the lower tooth height H3 of external thread 2 is 0.90mm; when the wall thickness of pipe body 1 is d≥12.7mm, the tooth height H4 of internal thread 4 on coupling 3 corresponding to external thread 2 on pipe body 1 is 1.9mm, the upper tooth height H5 of internal thread 4 is 0.90mm, and the lower tooth height H6 of internal thread 4 is 1.0mm;

[0078] like Figure 2 As shown, the external thread 2 includes several sequentially connected external thread guide surfaces 201, external upper thread perpendicularity adjustment surfaces 202, guide surface crest arc 203, external thread crest surface 204, crest surface bevel arc 205, interference fit upper thread protection bevel surface 206, bevel surface right angle bearing surface arc 207, external thread right angle bearing surface 208, external thread bearing surface 209, bearing surface root arc 2010, external thread root surface 2011, and external thread root surface guide surface arc 2012; as shown Figure 3 As shown, the angle formed by the external thread guide surface 201 and the mean diameter of the external thread 2 is... The angle is 101.69°, which is the included angle formed by the outer upper thread perpendicularity adjustment surface 202 and the mean diameter line of the external thread 2. The angle is 121.69°, which is the angle formed by the right-angle bearing surface 208 of the external thread and the pitch diameter of the external thread 2. The angle is 88.31°, which is the angle formed by the bearing surface 209 of the external thread and the pitch diameter of the external thread 2. The radius of the guide surface arc 203 is 85.31°; the radius of the guide surface arc 205 is 0.35mm; the radius of the guide surface arc 205 is 0.25mm; the radius of the guide surface arc 207 is 0.25mm; the radius of the guide surface arc 2010 is 0.25mm; the radius of the guide surface arc 2012 is 0.35mm.

[0079] like Figure 4 As shown, the internal thread 4 includes several sequentially connected internal thread guide surfaces 401, guide surface root arc 402, internal thread root surface 403, root surface bearing arc 404, internal thread bearing surface 405, internal thread right-angle bearing surface 406, right-angle bearing surface crest arc 407, internal thread crest surface 408, crest thread verticality adjustment surface arc 409, and internal thread verticality adjustment surface 4010; Figure 5 As shown, the angle formed by the internal thread guide surface 401 and the pitch diameter of the internal thread 4 is... The angle is 78.31°, which is the angle formed by the bearing surface 405 of the internal thread and the pitch diameter of the internal thread 4. The angle is 86.9°, which is the angle formed by the right-angle bearing surface 406 of the internal thread and the pitch diameter of the internal thread 4. The angle is 88.31°, which is the angle formed by the inner upper thread perpendicularity adjustment surface 4010 and the mean diameter line of the internal thread 4. The radius of the guide surface tooth bottom arc 402 is 0.35mm, the radius of the tooth bottom bearing surface arc 404 is 0.25mm, the radius of the right angle bearing surface tooth top arc 407 is 0.25mm, and the radius of the tooth top verticality adjustment surface arc 409 is 0.35mm.

[0080] like Figure 6 As shown, the inner sealing structure 6 includes a central hole surface 601, a central hole surface shoulder arc 602, an inner sealing shoulder surface 603, a shoulder surface sealing surface arc 604, a sealing surface 605, and a sealing cylindrical surface 606 connected in sequence. The sealing cylindrical surface 606 is an annular groove with a rectangular cross-section set on the inner wall of the coupling 3.

[0081] like Figure 7 As shown, the angle between the inner sealing shoulder surface 603 and the axis of the coupling 3 is... The angle is 76°, the angle between the sealing surface 605 and the axis of the coupling 3. The radius R12 of the sealing surface arc 604 of the shoulder surface is 0.65mm; the length L4 of the central hole surface 601 is 16.0mm; the thickness H9 of the inner sealing shoulder surface 603 is 4.6mm; and the length L3 of the sealing surface 605 projected onto the coupling 3 axis is 8.6mm.

[0082] like Figure 8As shown, the outer sealing structure 5 includes an inner diameter reduction surface shoulder arc 502, an outer sealing shoulder surface 503, a shoulder surface main sealing cone arc 504, a first sealing cone surface 505, a main sealing arc 506, a second sealing cone surface 507, and an inner diameter reduction surface 501 connected in sequence; the inner diameter reduction surface shoulder arc 502, the outer sealing shoulder surface 503, the shoulder surface main sealing cone arc 504, and the first sealing cone surface 505 are located on the end face of the pipe body 1, while the main sealing arc 506, the second sealing cone surface 507, and the inner diameter reduction surface 501 are located on the outer wall of the pipe body 1;

[0083] like Figure 9 As shown, the angle between the first sealing cone surface 505 and the axis of the pipe body 1 is... The angle between the outer sealing shoulder surface 503 and the axis of the tube body 1 is 14.2°. The angle between the second sealing cone surface 507 and the axis of the pipe body 1 is 76°. The angle is 1.59°; the thickness H7 of the outer sealing shoulder surface 503 is less than the thickness H9 of the inner sealing shoulder surface 603, and the difference H10 between H7 and H9 is 0.45mm, and the thickness H7 of the outer sealing shoulder surface 503 is greater than 3.3mm; the radial distance H8 between the connection between the second sealing cone surface 507 and the inner diameter reduction surface 501 and the external thread root surface 2011 closest to the port on the pipe body 1 is 0.43mm; the radius R10 of the arc 504 of the main sealing cone surface of the shoulder surface is 0.75mm, the length L1 of the projection of the first sealing cone surface 505 onto the axial direction of the pipe body 1 is 4.4mm, the radius R11 of the main sealing arc 506 is 6.5mm, and the length L2 of the projection of the second sealing cone surface 507 onto the axial direction of the pipe body 1 is 5.6mm.

[0084] Example 4

[0085] This embodiment proposes a thin-walled oil casing threaded joint, such as... Figure 1 As shown, the device includes a pipe body 1 with an outer diameter of 73.02 mm and a wall thickness of 5.51 mm. A coupling 3 is fitted onto the pipe body 1. The outer wall of the pipe body 1 has an external thread 2 with a negative angle hexagonal structure, and the inner wall of the coupling 3 has an internal thread 4 with a negative angle hexagonal structure. The external thread 2 and internal thread 4 are interference-fitted. An external sealing structure 5 is located on the outer wall of the pipe body 1 near its end, and an internal sealing structure 6 is located on the coupling 3. The external sealing structure 5 and internal sealing structure 6 are interference-fitted. The angle formed by the mean diameter line of the external thread 2 and the axis of the pipe body 1 is... The angle is 1.49°; the angle formed by the pitch diameter of the internal thread 4 and the axis of the coupling 3. The angle is 1.49°; the interference fit between the external thread 2 and the internal thread 4 is 0.13mm; the interference fit between the external sealing structure 5 and the internal sealing structure 6 is 0.35mm.

[0086] When the wall thickness of pipe body 1 is d < 6.45 mm, the tooth height of external thread 2 is 0.82 mm, the upper tooth height of external thread 2 is 0.41 mm, and the lower tooth height of external thread 2 is 0.41 mm. When the wall thickness of pipe body 1 is d < 6.45 mm, the tooth height H4 of internal thread 4 on coupling 3 corresponding to external thread 2 on pipe body 1 is 0.9 mm, the upper tooth height of internal thread 4 is 0.41 mm, and the lower tooth height of internal thread 4 is 0.49 mm.

[0087] like Figure 2 As shown, the external thread 2 includes several sequentially connected external thread guide surfaces 201, external upper thread perpendicularity adjustment surfaces 202, guide surface crest arc 203, external thread crest surface 204, crest surface bevel arc 205, interference fit upper thread protection bevel surface 206, bevel surface right angle bearing surface arc 207, external thread right angle bearing surface 208, external thread bearing surface 209, bearing surface root arc 2010, external thread root surface 2011, and external thread root surface guide surface arc 2012; as shown Figure 3 As shown, the angle formed by the external thread guide surface 201 and the mean diameter of the external thread 2 is... The angle is 101.59°, which is the angle formed by the outer upper thread perpendicularity adjustment surface 202 and the mean diameter line of the external thread 2. The angle is 121.59°, which is the angle formed by the right-angle bearing surface 208 of the external thread and the pitch diameter of the external thread 2. The angle is 88.21°, which is the angle formed by the bearing surface 209 of the external thread and the pitch diameter of the external thread 2. The radius of the guide surface arc 203 is 0.3 mm; the radius of the beveled surface arc 205 is 0.2 mm; the radius of the right-angle bearing surface arc 207 is 0.2 mm; the radius of the bearing surface arc 2010 is 0.2 mm; and the radius of the guide surface arc 2012 is 0.3 mm.

[0088] like Figure 4 As shown, the internal thread 4 includes several sequentially connected internal thread guide surfaces 401, guide surface root arc 402, internal thread root surface 403, root surface bearing arc 404, internal thread bearing surface 405, internal thread right-angle bearing surface 406, right-angle bearing surface crest arc 407, internal thread crest surface 408, crest thread verticality adjustment surface arc 409, and internal thread verticality adjustment surface 4010; Figure 5 As shown, the angle formed by the internal thread guide surface 401 and the pitch diameter of the internal thread 4 is... The angle is 78.21°, which is the angle formed by the pitch diameter of the internal thread bearing surface 405 and the internal thread 4. The angle is 86.8°, which is the angle formed by the right-angle bearing surface 406 of the internal thread and the pitch diameter of the internal thread 4. The angle is 88.21°, which is the angle formed by the inner upper thread perpendicularity adjustment surface 4010 and the mean diameter line of the internal thread 4. The radius of the guide surface tooth bottom arc 402 is 0.3mm, the radius of the tooth bottom bearing surface arc 404 is 0.2mm, the radius of the right angle bearing surface tooth top arc 407 is 0.2mm, and the radius of the tooth top verticality adjustment surface arc 409 is 0.3mm.

[0089] like Figure 6 As shown, the inner sealing structure 6 includes a central hole surface 601, a central hole surface shoulder arc 602, an inner sealing shoulder surface 603, a shoulder surface sealing surface arc 604, a sealing surface 605, and a sealing cylindrical surface 606 connected in sequence. The sealing cylindrical surface 606 is an annular groove with a rectangular cross-section set on the inner wall of the coupling 3; as shown... Figure 7 As shown, the angle between the inner sealing shoulder surface 603 and the axis of the coupling 3 is... The angle is 75°, the angle between the sealing surface 605 and the axis of the coupling 3. The radius R12 of the sealing surface arc 604 of the shoulder surface is 0.7mm; the length L4 of the central hole surface 601 is 13.3mm; the thickness H9 of the inner sealing shoulder surface 603 is 4.0mm; and the length L3 of the sealing surface 605 projected onto the coupling 3 axis is 4.55mm.

[0090] like Figure 8 As shown, the outer sealing structure 5 includes an inner diameter reduction surface shoulder arc 502, an outer sealing shoulder surface 503, a shoulder surface main sealing cone arc 504, a first sealing cone surface 505, a main sealing arc 506, a second sealing cone surface 507, and an inner diameter reduction surface 501 connected in sequence; the inner diameter reduction surface shoulder arc 502, the outer sealing shoulder surface 503, the shoulder surface main sealing cone arc 504, and the first sealing cone surface 505 are located on the end face of the pipe body 1, while the main sealing arc 506, the second sealing cone surface 507, and the inner diameter reduction surface 501 are located on the outer wall of the pipe body 1; as Figure 9 As shown, the angle between the first sealing cone surface 505 and the axis of the pipe body 1 is... The angle between the outer sealing shoulder surface 503 and the axis of the tube body 1 is 14.1°. The angle between the second sealing cone surface 507 and the axis of the pipe body 1 is 75.5°. The angle is 1.49°; the thickness H7 of the outer sealing shoulder surface 503 is 3.4 mm, the thickness H7 of the outer sealing shoulder surface 503 is less than the thickness H9 of the inner sealing shoulder surface 603, and the difference H10 between H7 and H9 is 0.4 mm; the radial distance H8 between the connection between the second sealing cone surface 507 and the inner diameter reduction surface 501 and the external thread root surface 2011 closest to the port on the pipe body 1 is 0.40 mm; the radius R10 of the arc 504 of the main sealing cone surface of the shoulder surface is 0.8 mm, the length L1 of the projection of the first sealing cone surface 505 onto the axial direction of the pipe body 1 is 3.1 mm, the radius R11 of the main sealing arc 506 is 5 mm, and the length L2 of the projection of the second sealing cone surface 507 onto the axial direction of the pipe body 1 is 3.9 mm.

[0091] The torque parameter design takes into account both field application in the oilfield and shoulder interference design. The design of thin-walled oil casing threaded joints must also consider the change in seal after threading. Torque parameter design is based on the range of seal parameter changes under different torques. The outer seal diameter parameter of the thin-walled oil casing threaded joint changes the most after threading / unthreading, as shown in Table 1. The change in the outer seal diameter parameter of the thin-walled oil casing threaded joint with a pipe body specification of Φ73.02×5.51mm and steel grade of P110 is used as a reference to determine the torque parameter design criteria. Other specifications and steel grades can be determined using this method to determine reasonable torque parameters.

[0092] Table 1 Torque Parameters

[0093]

Claims

1. A thin wall oil casing threaded joint comprising a tubular body (1) fitted with a coupling (3), characterized in that, The outer wall of the pipe body (1) is provided with an outer thread (2) in the form of a negative angle heptagon, the inner wall of the coupling (3) is provided with an inner thread (4) in the form of a negative angle hexagon, the outer thread (2) and the inner thread (4) are in interference fit, the outer wall of the pipe body (1) near the end is provided with an outer sealing structure (5), the coupling (3) is provided with an inner sealing structure (6), and the outer sealing structure (5) and the inner sealing structure (6) are in interference fit.

2. A thin wall oil sleeve threaded joint as claimed in claim 1, characterized in that, The included angle formed by the center line of the external thread (2) and the axis of the pipe body (1) is 1.49°-1.69° The included angle formed by the center line of the internal thread (4) and the axis of the coupling (3) is 1.49°-1.69° The interference amount of the interference fit between the external thread (2) and the internal thread (4) is 0.1mm-0.3mm; and the interference amount of the interference fit between the external sealing structure (5) and the internal sealing structure (6) is 0.3mm-0.8mm.

3. A thin-wall oil casing threaded joint according to claim 2, characterized in that, When the wall thickness of the pipe body (1) is d≥12.7mm, the tooth height H1 of the outer thread (2) is 1.7mm-1.9mm, the upper tooth height H2 of the outer thread (2) is 0.85mm-0.95mm, and the lower tooth height H3 of the outer thread (2) is 0.85mm-0.95mm; When the wall thickness of the pipe body (1) is 9.17mm≤d<12.7mm, the tooth height of the outer thread (2) is 1.5mm-1.7mm, the upper tooth height of the outer thread (2) is 0.75mm-0.85mm, and the lower tooth height of the outer thread (2) is 0.75mm-0.85mm; When the wall thickness of the pipe body (1) is 6.45mm≤d<9.17mm, the tooth height of the outer thread (2) is 0.96mm-1.06mm, the upper tooth height of the outer thread (2) is 0.48mm-0.53mm, and the lower tooth height of the outer thread (2) is 0.48mm-0.53mm; When the wall thickness of the pipe body (1) is d<6.45mm, the tooth height of the outer thread (2) is 0.8mm-0.9mm, the upper tooth height of the outer thread (2) is 0.4mm-0.45mm, and the lower tooth height of the outer thread (2) is 0.4mm-0.45mm.

4. A thin-wall oil casing threaded joint according to claim 3, characterized in that, When the wall thickness of the pipe body (1) is d≥12.7mm, the tooth height H4 of the inner thread (4) corresponding to the outer thread (2) on the pipe body (1) on the coupling (3) is 1.8mm-2mm, the upper tooth height H5 of the inner thread (4) is 0.85mm-0.95mm, and the lower tooth height H6 of the inner thread (4) is 0.95mm-1.05mm; When the wall thickness of the pipe body (1) is 9.17mm≤d<12.7mm, the tooth height H4 of the inner thread (4) corresponding to the outer thread (2) on the pipe body (1) on the coupling (3) is 1.6mm-1.8mm, the upper tooth height of the inner thread (4) is 0.75mm-0.85mm, and the lower tooth height of the inner thread (4) is 0.85mm-0.95mm; When the wall thickness of the pipe body (1) is 6.45mm≤d<9.17mm, the tooth height H4 of the inner thread (4) corresponding to the outer thread (2) on the pipe body (1) on the coupling (3) is 1.06mm-1.16mm, the upper tooth height of the inner thread (4) is 0.48mm-0.53mm, and the lower tooth height of the inner thread (4) is 0.58mm-0.63mm; If the wall thickness of the pipe body (1) is d < 6.45mm, the tooth height H4 of the internal thread (4) on the coupling (3) a corresponding to the external thread (2) on the pipe body (1) is 0.89mm-1mm, the upper tooth height of the internal thread (4) is 0.4mm-0.45mm, and the lower tooth height of the internal thread (4) is 0.49mm-0.55mm.

5. A thin-wall oil casing threaded joint according to claim 1, characterized in that, The external thread (2) comprises a plurality of sequentially connected external thread guide surfaces (201), external make-up perpendicularity adjusting surfaces (202), guide surface crest surface arcs (203), external thread crest surfaces (204), crest surface bevel surface arcs (205), interference make-up protection bevel surfaces (206), bevel surface right angle bearing surface arcs (207), external thread right angle bearing surfaces (208), external thread bearing surfaces (209), bearing surface root surface arcs (2010), external thread root surfaces (2011), external thread root surface guide surface arcs (2012); The angle formed by the outer thread guide surface (201) and the pitch line of the external thread (2) 101.59°-101.79°, the angle formed by the outer upper make-up perpendicularity adjustment surface (202) and the pitch line of the external thread (2) 121.59°-121.79°, the angle formed by the outer thread right angle load bearing surface (208) and the pitch line of the external thread (2) 88.21°-88.41°, the angle formed by the outer thread load bearing surface (209) and the pitch line of the external thread (2) 85.21°-85.41°; The radius R1 of the guide surface crest surface arc (203) is 0.3mm-0.4mm; the radius R5 of the crest surface bevel surface arc (205) is 0.2mm-0.3mm; the radius R4 of the bevel surface right angle bearing surface arc (207) is 0.2mm-0.3mm; the radius R3 of the bearing surface root surface arc (2010) is 0.2mm-0.3mm; and the radius R2 of the external thread root surface guide surface arc (2012) is 0.3mm-0.4mm.

6. A thin-wall oil casing threaded joint according to claim 1, characterized in that, The internal thread (4) comprises a plurality of sequentially connected internal thread guide surfaces (401), guide surface root surface arcs (402), internal thread root surfaces (403), root surface bearing surface arcs (404), internal thread bearing surfaces (405), internal thread right angle bearing surfaces (406), right angle bearing surface crest arcs (407), internal thread crest surfaces (408), crest make-up perpendicularity adjusting surface arcs (409), internal make-up perpendicularity adjusting surfaces (4010); the angle formed by the inner thread guide surface (401) with the center line of the inner thread (4) is 78.21°-78.41°, the angle formed by the inner thread load surface (405) with the center line of the inner thread (4) is 86.8°-87°, the angle formed by the inner thread right angle load surface (406) with the center line of the inner thread (4) is 88.21°-88.41°, the angle formed by the inner make-up perpendicularity adjustment surface (4010) with the center line of the inner thread (4) is 58.21°-58.41°; The radius R9 of the guide surface root surface arc (402) is 0.3mm-0.4mm, the radius R8 of the root surface bearing surface arc (404) is 0.2mm-0.3mm, the radius R7 of the right angle bearing surface crest arc (407) is 0.2mm-0.3mm, and the radius R6 of the crest make-up perpendicularity adjusting surface arc (409) is 0.3mm-0.4mm.

7. A thin-wall oil casing threaded joint according to claim 1, characterized in that, The internal sealing structure (6) comprises a plurality of sequentially connected middle hole surfaces (601), middle hole surface shoulder surface arcs (602), internal sealing shoulder surfaces (603), shoulder surface sealing surface arcs (604), sealing surfaces (605), and sealing cylindrical surfaces (606), wherein the sealing cylindrical surfaces (606) are rectangular annular grooves arranged on the inner wall of the coupling (3); The inner sealing shoulder face (603) is at an angle of 75°-77° with the axis of the coupling (3) The sealing face (605) is at an angle of 14.1°-14.3° with the axis of the coupling (3) The radius R12 of the shoulder face sealing face arc (604) is 0.6mm-0.7mm; The length L4 of the middle hole surface (601) is 13.0mm-19.0mm, the thickness H9 of the internal sealing shoulder surface (603) is 3.8mm-5.1mm, and the length L3 of the sealing surface (605) projected on the axial direction of the coupling (3) is 4.0mm-13.2mm.

8. A thin-wall oil casing threaded joint according to claim 1, characterized in that, The outer sealing structure (5) comprises, in sequence, an inner diameter reducing surface shoulder surface circular arc (502), an outer sealing shoulder surface (503), a shoulder surface main sealing taper surface circular arc (504), a first sealing taper surface (505), a main sealing circular arc (506), a second sealing taper surface (507), and an inner diameter reducing surface (501); the inner diameter reducing surface shoulder surface circular arc (502), the outer sealing shoulder surface (503), the shoulder surface main sealing taper surface circular arc (504), and the first sealing taper surface (505) are located on the end surface of the pipe body (1), and the main sealing circular arc (506), the second sealing taper surface (507), and the inner diameter reducing surface (501) are located on the outer wall of the pipe body (1); the angle of the first sealing cone (505) with the axis of the pipe body (1) is 14.1°-14.3°, the angle of the outer sealing shoulder (503) with the axis of the pipe body (1) is 75°-77°, the angle of the second sealing cone (507) with the axis of the pipe body (1) is 1.49°-1.69°; The thickness H7 of the outer sealing shoulder surface (503) is less than the thickness H9 of the inner sealing shoulder surface (603), and the difference H10 between H7 and H9 is 0.3mm-0.6mm, and the thickness H7 of the outer sealing shoulder surface (503) is greater than 3.3mm; the radial distance H8 between the connection between the second sealing taper surface (507) and the inner diameter reducing surface (501) and the outer thread root surface (2011) closest to the port on the pipe body (1) is 0.39mm-0.46mm; The radius R10 of the shoulder surface main sealing taper surface circular arc (504) is 0.7mm-0.8mm, the length L1 of the first sealing taper surface (505) projected in the axial direction of the pipe body (1) is 3.0mm-5.8mm, the radius R11 of the main sealing circular arc (506) is 5mm-8mm, and the length L2 of the second sealing taper surface (507) projected in the axial direction of the pipe body (1) is 3.1mm-8.0mm.

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