High torsional resistance drill pipe joint for rapid make-up in extra-deep wells

Abstract

The present invention provides a high torsional resistance drill pipe joint for rapid make-up in ultra-deep wells, including a male threaded joint and a female threaded joint threadedly connected thereto. The size of the clearance ΔL1 from the small end of the male thread to the inner shoulder surface is increased, and the angle δ between the bearing surface and the tangent of the tooth bottom fillet is increased. The cross-sections of the inner and outer shoulders are optimized to be composed of a fillet section, a large ellipse section, a small ellipse section, a fillet section and a straight line section, and the inner and outer shoulder surfaces are designed to be inclined. The step surfaces of the male and female joints are optimized. An elliptical stress relief groove is provided on the male joint. In addition, the thread pitches on both sides of the thread engagement section are increased. This solution achieves stiffness matching while achieving the purpose of eliminating high stress areas and enhancing sealing, improves the stress distribution on the thread teeth and the stress concentration at the inner and outer shoulder threads during male and female thread engagement, optimizes the bearing capacity distribution of the engaged threads, speeds up the make-up and break-out speed of the thread joint, improves the torsional resistance strength and sealing performance of the drill string thread joint, and prevents secondary make-up accidents.

Description

Technical Field

[0001] The present invention relates to the field of drill pipe joints, and particularly to a high anti-torsion drill pipe joint for rapid make-up in ultra-deep wells. Background Art

[0002] In recent years, with the successive development of a large number of deep wells, ultra-deep wells and even ten-thousand-meter ultra-deep wells in the oil and gas exploration industry, higher requirements have been put forward for the performance of drill pipes used in the drilling process. The optimization of the mechanical properties of drill pipes is mainly carried out from two aspects: material properties and structural design. The improvement of drill pipe material properties mainly relies on the progress of materials science. Only by optimizing the structural design can the performance of drill pipes be improved in a short time. Since the length of a single conventional drill pipe is only 9 to 13 meters, while the drilling depth needs to reach 10,000 meters or even deeper, hundreds of drill pipes need to be connected end to end through threaded joints to form an integral pipe string that can transmit torque. When the drill pipe is working, it not only has to withstand huge torque and alternating stress, but also has to withstand the huge pressure of the drilling fluid inside the pipe. At the same time, the weight of the drill pipes in the entire well section can reach 1,000 tons. This puts forward higher requirements for the rapid make-up and break-out of drill pipes, the rationality of the threaded force distribution, and the joint sealing performance, so as to avoid the threaded joint structure of the drill pipe becoming an obstacle restricting the breakthrough of the drilling depth. According to the existing API (American Petroleum Institute) standard, oil and gas wells with a well depth of 4,500 to 6,000 meters are called deep wells, those with a well depth of 6,000 to 9,000 meters are called ultra-deep wells, and those with a well depth of more than 9,000 meters are called ultra-deep wells. At present, the development of ten-thousand-meter ultra-deep wells is underway in China. Since the designed well depth exceeds 11,000 m, as the depth increases, the service life of devices such as drill bits decreases rapidly, and it is necessary to frequently replace downhole devices such as drill bits. During the process of tripping out to replace the drill bit, the time required to disassemble the drill pipe reaches several days. During this period, since the drill pipes need to be continuously taken out of the wellhead, the wellhead is in a period of weak sealing, which is not conducive to wellhead pressure control. In severe cases, even blowout and other serious accidents may occur. Moreover, during the drilling process, the top drive drilling system or downhole motor at the wellhead continuously applies torque to the drill pipe, causing the make-up of the drill pipe joint to be too tight, and thus it is inconvenient to break the joint.

[0003] At present, the design of drill pipe joints in the petroleum industry mainly refers to the API standards issued by the American Petroleum Institute. Such drill pipe joints include male and female thread joints that can be threadedly engaged with each other. The joint body from the outer shoulder surface to its end is successively a taper pipe thread base, a taper pipe male thread, and a front end of the taper pipe thread; the female thread joint body engaged with its thread includes a main end face of the female thread joint. On this joint body, from the main end face of the female thread joint along the axis from outside to inside are successively a female thread base, a taper pipe female thread, and a female thread end hole. The taper pipe male thread and the taper hole female thread used for mutual engagement have the same thread pitch, as well as corresponding thread profiles and thread tapers. When the joints are connected and used, the outer shoulder surface of the male thread joint and the main end face of the female thread joint are interference-fitted with each other, bearing and transmitting the torque of the drill pipe and playing a sealing role. Research shows that the threaded part of the threaded joint will bear most of the torque, and the stress and torque are mainly concentrated on the last three thread teeth of the threaded part. The stress borne by these three thread teeth can reach more than 50% of the total stress at most, and gradually decreases from the mating shoulder to the front end thread. The front end thread teeth hardly bear stress. Therefore, the stress on the thread teeth is extremely uneven, directly affecting the fatigue resistance and service life of the joint, and making the mechanical strength of the joint not fully utilized. When used in ultra-deep wells or extremely complex wells, due to excessive and concentrated torque, it is extremely easy to cause failure accidents such as thread fracture of the male thread or swelling of the female thread.

[0004] In view of the above technical problems, a prior Chinese patent proposed a high anti-torsion and fully sealed drill pipe threaded joint (patent publication number CN104131788B). It increases the pitch or length of the male and female threads in the rear section of the joint to 1.0 to 1.1 times that of the male and female threads in the front section. After the male and female thread joints are tightened by a certain number of turns, the threaded parts combined in the front section produce different elastic deformation amounts from the threaded parts in the rear section. The elastic deformation amount in the front section is greater than that in the rear section, forcing the force on the threaded parts in the rear section to transfer to the threaded parts in the front section, thus effectively solving the problem of serious non-uniformity of the connecting threads of the joint along the length direction. However, the bearing side area of the thread is too large, which is likely to cause an increase in friction, and then make it difficult to make up and break out the connection, reducing the drilling efficiency.

[0005] A Chinese patent discloses a high-torsion-resistant drill pipe threaded joint (application publication number CN105909183A), in which the taper range of the preferred thread section is 1:6 to 1:16, and the cylindrical small end of the male threaded joint and the cylindrical large end of the female threaded joint are set to an interference fit to increase the make-up torque. However, the interference contact between the male and female joints at the end faces will make it difficult to make and break out the threaded joint, reducing drilling efficiency. In order to achieve precise interference dimensions, processing will be difficult, and the torque provided by the wellhead or downhole power drill during actual drilling will inevitably cause secondary make-up of the drill pipe joint, but with different degrees of severity. The structure designs the end face as an interference fit, which will cause the end face to bear the axial load caused by the secondary make-up and the radial load caused by the interference fit at the same time. Once the stress at this point reaches a certain level, rotational fatigue and even crack initiation will occur during the drilling process, seriously affecting the safety of the drill tool.

[0006] A Chinese patent for a quick-make threaded joint with an anti-galling effect (application publication number CN114320175A) uses a design with a male and female pitch of 5.08mm to 6.35mm and a taper of 1:6 to 1:16. It also uses a double-thread design, so that there are two symmetrically distributed thread starting points in the thread starting plane, each thread starting point corresponds to a complete helix, and the two helices are arranged parallel and equidistantly without affecting each other. Therefore, the lead of the double-thread on the same workpiece is doubled compared to the lead of the single-thread of the same specification. Under the same thread length, the thread tightening stroke is halved, which increases the make-up speed. However, the double-start thread has its own unique disadvantages, such as high manufacturing cost, difficult installation, susceptibility to environmental influences, difficulty in controlling the tightening torque, and damage to any thread will cause the entire joint to need to be replaced.

[0007] A Chinese patent for a threaded drill pipe joint (authorization announcement number CN102678068B) preferably has a thread taper of 1:16, an effective number of threads of the male thread on the male joint is 12, and a total of 16 threads of the female thread on the female joint. The first flank angle of the threaded tapered thread is 30°, the second flank angle is 45°, and the pitch is 1 / 3 inch. An extension section is provided at the thread end of the female joint. Compared with the API standard, this structure increases the second flank angle to 45°, which can increase the radial average thickness of the thread, reduce the fatigue sensitivity of the thread root, and reduce the occurrence of fatigue or brittle fracture of the thread. However, increasing the second flank angle will increase the length of the guide thread bearing surface 4, which will increase the friction of the thread contact to a certain extent, resulting in a decrease in the efficiency of make-up and make-out. The simple extension section provided at the thread end does not alleviate the high stress area near the thread. Even when subjected to a huge axial load, the high stress area expands, which in turn leads to crack initiation accidents in the threaded joint.

[0008] A Chinese patent for a variable tooth width threaded joint (authorization announcement number CN110410024B) preferably has tooth width enlarged sections on both sides of the meshing section of the male variable tooth width threaded joint, an API standard tooth width section in the middle, and the pitches of both the male and female threaded joints are equal to the pitch of the API standard thread. Therefore, the problem of large stress concentration at the large end of the male threaded joint during male-female thread meshing is solved, the bearing capacity distribution of the meshing threads is optimized, and the bearing capacity of the threaded joint is improved. However, on both sides of the male and female threads in the thread meshing section, using variable pitch threads can also achieve an increase in the cross-sectional area of the thread material within the same length, thereby improving strength and improving the high stress distribution. And the bearing surface angle is set to 45 degrees, which will increase the bearing surface area, resulting in an increase in friction and a decrease in the make-up and break-out speed.

[0009] In summary, the present application proposes a high anti-torsion drill pipe joint for rapid make-up in ultra-deep wells to solve the problems existing in the prior art. Summary of the Invention

[0010] The purpose of the present invention is to provide a high anti-torsion drill pipe joint for rapid make-up in ultra-deep wells in view of the deficiencies of the prior art, and this high anti-torsion drill pipe joint for rapid make-up in ultra-deep wells can well solve the above problems.

[0011] To meet the above requirements, the technical solution adopted by the present invention is: to provide a high anti-torsion drill pipe joint for rapid make-up in ultra-deep wells, which includes a male threaded joint and a female threaded joint that is threadedly connected to it, and optimizes the tooth profile structures of the male and female threads and the drill pipe joint structure; the male threaded joint is sequentially provided with a male joint outer shoulder surface, a male joint large end stress relief groove, a male joint large end thread chamfering section, a male joint near-outer shoulder thread pitch enlargement section, a male joint middle thread pitch standard section, a male joint near-inner shoulder thread pitch enlargement section, a male joint small end elongation section, and a male joint inner shoulder surface from left to right; the female threaded joint is sequentially provided with a female joint outer shoulder surface, a wall thickness reduction part of the female joint large end elongation section, a step of the female joint large end elongation section, a wall thickness increase part of the female joint large end elongation section, a female joint near-outer shoulder thread pitch enlargement section, a female joint middle thread standard pitch section, a female joint near-inner shoulder enlarged thread pitch section, and a female joint inner shoulder surface from left to right; both the male joint outer shoulder surface and the female joint outer shoulder surface are irregular sealing surfaces, and the cross-sectional line segments thereof are sequentially composed of an arc segment, a large ellipse segment, a small ellipse segment, an arc segment, and a straight line segment from the outer wall to the inner wall, and all line segments are tangent in sequence.

[0012] The advantages of this high anti-torsion drill pipe joint for rapid make-up in ultra-deep wells are as follows:

[0013] 1. By adding an inclined straight segment to the thread root of the drill pipe thread joint, the maximum stress value in the stress concentration area will be reduced, and the maximum thread stress will appear on the thread bearing surface with stronger bearing capacity, preventing cracks from occurring at the arc of the thread root and causing the thread joint to break, thus extending the service life of the drill pipe; the length of the thread bearing surface is also reasonably reduced, thereby reducing the make-up and break-out friction force on the drill pipe thread joint, accelerating the make-up and break-out speed, and increasing the drilling construction efficiency.

[0014] 2. The special-shaped contact surface designed for the inner and outer step surfaces, which is composed of an arc segment, an elliptical segment and a straight segment, increases the leakage path length on the shoulder surface, thus increasing the sealing strength of the thread joint designed in the present invention. Secondly, during the processing, the circumferential path of the shoulder surface cutting is optimized and designed as a closed curve composed of a clockwise half-turn helix and a counterclockwise half-turn helix, which can prevent the phenomenon of secondary make-up caused by the torque applied by the top drive or downhole motor drill during the drilling process. The principle is that after the step surfaces are mated, the axial thickness distribution is not uniform. When the torque value received by the thread joint exceeds the maximum value that the frictional force of the step surface can bear and there is a tendency to rotate, the inclined surface of the joint step will provide a normal force to prevent secondary make-up;

[0015] 3. By increasing the distance L10 from the last complete thread at the large end of the female joint to the outer shoulder surface and designing a step in the extended section. The reason for designing this step surface is that during the finite element mechanical analysis of the API standard thread joint, it is found that there is a high stress area near the thread, and there may be a huge extrusion force on the outer shoulder surface during the ultra-deep well drilling process, which may cause a crushing phenomenon. Therefore, a step is designed in the extended section at the large end of the female joint to increase the thickness near the thread section to achieve the purpose of eliminating the high stress area, and the thickness near the outer shoulder surface is reduced. In addition, a stress relief groove is designed at the root of the large end of the male thread joint, and the top 3-5 threads at the root of the large end of the male thread are trimmed, all of which achieve the purpose of reducing the wall thickness, making the stiffness of the male and female joints match at this point, preventing the large end of the female thread joint from being crushed during the make-up process and the drill pipe being compressed, and eliminating the risk of crack initiation in the high stress area;

[0016] 4. By optimizing the inner shoulder clearance ΔL1 of the drill pipe joint, after the drill pipe thread joint is made up, there is an appropriate extrusion force between the outer shoulders without being crushed, and the generated contact pressure maintains the outer shoulder seal, forming a seal for the drill string thread joint. At the same time, there is a reasonable extrusion force on the inner shoulder, generating an inner shoulder seal, forming a seal for the drill string thread joint.

[0017] 5. After the top of the thread is cut, a clearance ΔL2 is set between the top surface of the thread and the corresponding surface of the female thread joint, and it is preferably 0.5 to 1.5 mm. The specific principle is that after the external shoulder of the thread joint is tightened, the Poisson effect is generated under the extrusion pressure, increasing the wall thickness of the large end of the female joint. The clearance ΔL2 will be compressed, and the sealing rubber strip in the thread groove after the top is cut is compressed and deformed, completely sealing the clearance ΔL2, achieving an additional sealing surface at this position of the thread joint and improving the sealing performance of the thread joint.

[0018] 6. The thread surface is treated with a surface nitriding process to form a nitrided layer on the thread surface, increasing the strength of the thread surface and preventing damage to the thread surface caused by multiple make-up and break-out operations. Secondly, surface ultrasonic nanocrystalline rolling processing is carried out to reduce the surface roughness of the thread, reduce the friction force, and form a compressive stress layer on the thread surface, achieving a reduction in the make-up and break-out resistance and an increase in the drilling efficiency. Also, due to the presence of the compressive stress layer on the surface, the phenomenon of crack initiation on the thread surface is reduced.

[0019] 7. Pitch-increased sections are provided on both sides of the thread engagement section. By using different pitches in different parts of the thread, vibrations of certain frequencies are disrupted, reducing the risk of resonance. Through finite element analysis, it is found that high-stress areas appear on both sides of the thread engagement. By increasing the pitch, the linear density of the thread is reduced, and within the same length, the cross-sectional area of the thread material is larger, thereby improving the strength and the area of the high-stress distribution region, enabling the thread connection to have better performance in places where greater strength is required. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are used to provide a further understanding of the present application and form a part of the present application. The same reference numerals are used to represent the same or similar parts in these drawings. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0021] Figure 1 is an assembly schematic diagram of the high-torque-resistant drill pipe thread joint for rapid make-up in the ultra-deep well described in the embodiment of the present invention;

[0022] Figure 2 is a three-dimensional sectional view of the female thread joint of the high-torque-resistant drill pipe for rapid make-up in the ultra-deep well described in the embodiment of the present invention;

[0023] Figure 3 is a three-dimensional sectional view of the male thread joint of the high-torque-resistant drill pipe for rapid make-up in the ultra-deep well described in the embodiment of the present invention;

[0024] Figure 4 is a stress distribution nephogram after the make-up of the drill pipe thread joint recommended by the API standard;

[0025] Figure 5Schematic cross-sectional plan view of a high torsional resistance drill pipe thread joint for quick make-up in the ultra-deep well of the present invention embodiment;

[0026] Figure 6 Schematic cross-sectional structure view of a female drill pipe thread joint of the present invention embodiment;

[0027] Figure 7 Schematic cross-sectional structure view of a male drill pipe thread joint of the present invention embodiment;

[0028] Figure 8 Schematic view of the local thread structure dimensions when the female thread member and the male thread member of the present invention embodiment are engaged;

[0029] Figure 9 Schematic cross-sectional dimension view of a female drill pipe thread joint of the present invention embodiment;

[0030] Figure 10 Schematic cross-sectional dimension view of a male drill pipe thread joint of the present invention embodiment;

[0031] Figure 11 Schematic enlarged structure dimension view at the inner shoulder of the drill pipe joint of the present invention embodiment;

[0032] Figure 12 Schematic enlarged structure dimension view at the outer shoulder of the drill pipe joint of the present invention embodiment;

[0033] Figure 13 Schematic enlarged structure dimension view of the step and stress relief groove at the outer shoulder of the drill pipe joint of the present invention embodiment;

[0034] Figure 14 Schematic cross-sectional structure view at the outer shoulder of the drill pipe joint of the present invention embodiment;

[0035] Figure 15 Schematic cutting path view at the outer shoulder of the drill pipe joint of the present invention embodiment;

[0036] Figure 16 Schematic structure views before and after the operation of the irregular shoulder surface designed in the present invention.

[0037] Wherein: 1. Male threaded joint; 11. Female joint outer shoulder surface; 12. Wall thickness thinning part of the large end elongation section of the female joint; 13. Step of the large end elongation section of the female joint; 14. Wall thickness increasing part of the large end elongation section of the female joint; 15. Thread pitch increasing section of the female joint near the outer shoulder; 16. Standard thread pitch section of the middle part of the female joint; 17. Thread pitch increasing section of the female joint near the inner shoulder; 18. Inner shoulder surface of the female joint; 2. Female threaded joint; 21. Male joint outer shoulder surface; 22. Stress relief groove at the large end of the male joint; 23. Thread crest cutting section of the large end of the male joint; 24. Thread pitch increasing section of the male joint near the outer shoulder; 25. Standard thread pitch section of the middle part of the male joint; 26. Thread pitch increasing section of the male joint near the inner shoulder; 27. Small end elongation section of the male joint; 28. Inner shoulder surface of the male joint; 3. Thread meshing relaxation surface; 4. Thread meshing bearing surface; 5. Inner shoulder clearance of the threaded joint; 6. Sealing rubber strip. Detailed implementation mode

[0038] To make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0039] In the following description, references to "an embodiment", "embodiments", "an example", "examples", etc. indicate that the described embodiments or examples may include specific features, structures, characteristics, properties, elements or limitations, but not every embodiment or example necessarily includes specific features, structures, characteristics, properties, elements or limitations. Additionally, repeated use of the phrase "according to an embodiment of the present application" although possibly referring to the same embodiment does not necessarily refer to the same embodiment.

[0040] For simplicity, certain technical features well-known to those skilled in the art are omitted in the following description.

[0041] Please refer to Figures 1 to 3 , in this embodiment, the drill pipe threaded joint structure includes a female threaded joint 1 and a male threaded joint 2. Specifically, the drill pipe joints are fixed by welding at both ends of the drill pipe. During actual drilling, the male threaded joint at the upper part of the drill bit is connected to the female threaded joint 2 at one end of the drill pipe to fix the drill bit. When the footage reaches one length, the male threaded joint 1 of another drill pipe is connected to the female threaded joint 2 of the previous drill bit to lengthen the drill string. The drilling operation is completed by sequentially connecting multiple drill pipes through the threaded joints of the drill pipe joints. At the same time, as Figures 1 to 3 shown, both the male threaded joint and the female threaded joint are hollow structures, and a drill pipe inner annulus is provided inside both of them.

[0042] Refer to Figure 4, This figure shows the stress distribution diagram of the drill pipe thread joint recommended by the API standard after make-up. It can be found from the figure that there are dark high-stress areas at the ends of the last threads of both ends of the thread joint, and there is a large area of high-stress area in the elongation section of the female joint, even extending to the outer wall of the drill pipe, which may cause crack initiation and even lead to fracture failure and other accidents during the use of ultra-deep wells. Therefore, this structure is not the optimal structure.

[0043] Refer to Figures 5 to 7 and Figure 11 , In this embodiment, the key parts of the drill pipe thread joint include the outer shoulder surface 11 of the female joint, the wall thickness thinning part 12 of the large end elongation section of the female joint, the step 13 of the large end elongation section of the female joint, the wall thickness increasing part 14 of the large end elongation section of the female joint, the pitch increasing section 15 of the thread near the outer shoulder of the female joint, the standard pitch section 16 of the thread in the middle of the female joint, the pitch increasing section 17 of the thread near the inner shoulder of the female joint, the inner shoulder surface 18 of the female joint, the outer shoulder surface 21 of the male joint, the stress relief groove 22 at the large end of the male joint, the thread topping section 23 at the large end of the male joint, the pitch increasing section 24 of the thread near the outer shoulder of the male joint, the standard pitch section 25 of the thread in the middle of the male joint, the pitch increasing section 26 of the thread near the inner shoulder of the male joint, the small end elongation section 27 of the male joint, the inner shoulder surface 28 of the male joint, and the inner shoulder gap 5 of the thread joint. When the make-up torque T is applied to both ends of the drill pipe, the male and female joints will contact and generate extrusion pressure at the outer shoulder surface, realizing the sealing of the outer shoulder of the joint and forming a seal of the drill string joint. The drill pipe thread continues to rotate. When the make-up torque reaches a certain value T1, the gap distance ΔL1 between the male joint 2 and the female joint 1 at the inner shoulder will disappear. At this time, the inner shoulder surface 28 of the male joint will contact the inner shoulder surface 18 of the female joint. When the make-up torque is further increased to the rated torque T2, the inner shoulders contact and generate extrusion pressure, and the male and female threads mesh to form a seal of the drill string joint. At the same time, the thread topping section 23 at the large end of the male joint and the wall thickness increasing part 14 of the large end elongation section of the female joint also contact and generate extrusion pressure to form a seal of the drill string joint.

[0044] Specifically, during the process of screwing the drill string joint, as the male joint 2 and the female joint 1 come into contact at the outer shoulder and start to generate extrusion pressure, the gap ΔL1 at the inner shoulder also decreases accordingly until the inner shoulder surfaces 28 of the male threaded joint and 18 of the female threaded joint come into contact and generate extrusion pressure. Since the outer shoulder surface of the drill string joint comes into contact earlier than the inner shoulder surface, and when the make-up torque reaches the range of T1 to T2, the extrusion pressure on the outer shoulder surface of the drill string joint is greater than that on the inner shoulder surface. To ensure that the contact strength generated by the extrusion pressure between the inner shoulder surfaces meets the design requirements, and the extrusion pressure on the outer shoulder does not crush the structures of the outer shoulder surface 21 of the male threaded joint and the outer shoulder surface 11 of the female threaded joint, the gap ΔL1 of the inner shoulder needs to be designed appropriately. Therefore, the optimized drill string inner shoulder gap ΔL1 is fitted as ΔL1 ∝ 1 / 2·η·κ·ξ·(R8 - R7)·tan(γ), where η is the coefficient of material mechanical properties, κ is the correction coefficient for downhole working temperature, ξ is the correction coefficient for sealing performance level, and γ is the thread taper angle.

[0045] Refer to Figure 8 , in this embodiment, the key structural parameters at the thread engagement part include the flank angle α between the load-bearing surface 4 and the tube radial direction, the flank angle β between the relief surface 3 and the tube radial direction, the tube thread taper γ, the angle δ between the load-bearing surface 4 of the thread and the tangent line of the root fillet, the pitch p of the male and female threads, the theoretical thread crest height H1, the thread profile height H2 before truncation, the crest trimming height H3, the root trimming height H4, the root fillet radius R1 of the load-bearing surface, the root fillet radius R2 of the guiding surface, and the crest fillet radius R3;

[0046] Specifically, the main improvement points of the thread sealing surface are: setting the angle δ between the load-bearing surface 4 of the thread and the tangent line of the root fillet, reducing the load-bearing surface area and the root wall thickness of the male thread;

[0047] Specifically, increasing the flank angle of the load-bearing surface 4 and the flank angle of the relief surface 3 of the thread increases the average thickness of the load-bearing surface 4 of the thread, achieving an increase in the torque-bearing capacity and the axial compression load-bearing capacity of the drill pipe during drilling;

[0048] Specifically, the thread pitch is increased on both sides of the thread engagement section, while the middle section has a standard pitch;

[0049] Specifically, setting the angle δ between the load-bearing surface 4 of the thread and the tangent line of the root fillet reduces the friction contact area of the load-bearing surface 4 of the thread, achieving a reduction in the make-up time of the drill pipe thread joint and realizing rapid make-up;

[0050] Specifically, increase the tangent angle δ between the threaded bearing surface 4 and the tooth root fillet, and reduce the wall thickness of the male thread tooth root, so as to reduce the stiffness of the male thread tooth root, thereby reducing the maximum stress in the stress concentration area at the tooth root. After a large number of finite element calculations, after setting the δ angle, the position of the maximum stress in the threaded engagement part is transferred from the stress concentration area at the tooth root to the threaded bearing surface 4 with better load-bearing capacity, and the maximum stress is reduced, achieving the purpose of increasing the service life of the drill pipe threaded joint.

[0051] Refer to Figure 9 and Figure 12 In this embodiment, the key dimensions of the male joint 2 of the drill pipe thread include the length L1 of the male threaded joint, the distance L2 from the intersection of the stress relief groove and the thread cresting section to the outer shoulder surface, the distance L3 from the intersection of the thread cresting section and the last complete thread to the outer shoulder surface, the distance L4 from the male thread base surface to the outer shoulder surface, the distance L5 from the small end of the male joint thread to the inner shoulder, the outer diameter R4 of the drill pipe joint, the inner diameter R5 of the male joint, the pitch diameter R6 of the male joint thread base surface, the small end radius R7 of the male joint, and the cutting angle θ1 of the small end of the male joint thread.

[0052] Specifically, 3 to 5 threads of the male thread are selected for cresting treatment at the cresting of the large end of the male thread of the male joint. By reducing the wall thickness of this part of the male threaded joint, the stiffness of the male and female joints is matched at this point, preventing the large end of the female thread from being crushed during the make-up process and the working condition of the drill pipe under pressure.

[0053] Specifically, a sealing rubber strip is filled in the thread groove left after cresting, which constitutes a sealing structure of the threaded joint.

[0054] Refer to Figure 10 In this embodiment, the key dimensions of the female joint 1 of the drill pipe thread include the length L6 of the female threaded joint, the distance L7 from the intersection of the small end of the female threaded joint and the thread to the outer shoulder, the distance L8 from the female thread base surface to the outer shoulder, the distance L9 from the intersection of the large end of the female thread and the thread to the outer shoulder, the length L10 of the reduced wall thickness section at the large end of the female joint thread, the distance L10 from the large end of the female joint thread to the increased wall thickness section, the outer diameter R8 of the female joint, the inner diameter R9 of the reduced wall thickness section at the large end of the female joint, the inner diameter R10 of the increased wall thickness section at the large end of the female joint, the pitch diameter R11 of the female joint thread base surface, the outer diameter R12 of the small end of the female joint, the inner diameter R13 of the female joint, the chamfer angle θ2 of the large end of the female joint thread, the inner shoulder clearance ΔL1 of the drill pipe joint, and the clearance ΔL2 between the cresting section of the male joint of the drill pipe and the thickened section at the large end of the female joint.

[0055] Specifically, the elongation part at the large end of the female joint is lengthened compared with the regulations in the API standard, and a step 13 is added, so that the wall thickness of the lengthened section is different, and the wall thickness near the outer shoulder stage is smaller, reducing the stiffness of this part of the female threaded joint, making the stiffness of the male and female joints match at this point, preventing the large end of the female threaded joint from being crushed during the make-up process and the working condition of the drill pipe under pressure, and increasing the stiffness near the elongated section of the thread to reduce the high-stress area and reduce the risk of crack initiation.

[0056] Specifically, a gap ΔL2 is added between the cut-off section of the male drill pipe joint and the thickened section at the large end of the female joint. After the make-up is completed, the female joint is pressurized, and due to the Poisson effect, the radial wall thickness of the extended section at the large end of the female joint increases, causing the gap ΔL2 to be closed. A sealing rubber strip 6 is also embedded in the incomplete thread groove of the male thread after cutting, that is, a sealing surface is added in the threaded joint to improve the sealing performance of the threaded joint.

[0057] Refer to Figure 11 , a threaded joint inner shoulder gap 5 is formed between the increased pitch section 26 of the thread near the inner shoulder of the male joint and the standard pitch section 16 of the thread in the middle of the female joint.

[0058] Refer to Figure 13 , in this embodiment, at the stress relief groove at the large end of the male joint and the step at the extended section of the large end of the female joint, the stress relief groove is designed as an elliptical surface, where the major axis dimension is a1, the minor axis radius is b2, the step angle is θ2, and the inclination angle of the major axis of the ellipse is the same as the taper angle of the thread.

[0059] Specifically, the inclination angle of the major axis of the ellipse is designed to be the same as the taper angle of the thread. After a large number of finite element calculations, it is found that the stress distributions of the traditional circular groove type or flat bottom type relief grooves do not fit the cross-sectional distribution of the taper angle of the thread as evenly. Therefore, it is preferred that the inclination angle of the major axis of the ellipse is the same as the taper angle of the thread.

[0060] Refer to Figures 14 to 16 , in this embodiment, the shoulder surface is designed to consist of a rounded corner section, a large ellipse section, a small ellipse section, a rounded corner section, and a straight line section from the outer wall to the inner wall, and all the line segments are tangent in sequence. The structural parameters include the rounded corner radius R14 near the outer wall of the joint, the rounded corner radius R15 near the inner wall of the joint, the major axis dimension a2 of the large ellipse, the minor axis dimension b2 of the large ellipse, the major axis dimension a3 of the small ellipse, the minor axis dimension b3 of the small ellipse, the distance L12 from the tangent point of the large and small ellipses to the outer wall, the distance L13 from the tangent point of the large and small ellipses to the inner wall, and the length L14 of the straight line section.

[0061] Specifically, the large ellipse of the outer shoulder is designed near the outer wall of the drill string. The reason for this design is that after Figure 4 analysis, it is found that there are high stress regions on the contact surface of the outer shoulder, and during the process of bearing torque and internal and external pressures, the shear stress near the outer wall is greater, resulting in a stress concentration region near the outer wall of the outer shoulder. To reduce the stress concentration phenomenon caused by the irregular shape of the structure, the large ellipse of the outer shoulder is designed near the outer wall of the drill string.

[0062] Specifically, after optimization, the ratio of the distances from the tangent points of the elliptical segments to the outer wall and the inner wall is designed to be 1.5 to 2, the ratio range of the major axis length of the large elliptical segment to the major axis length of the small elliptical segment is designed to be 1.5 to 3, and the ratio range of the minor axis length of the large elliptical segment to the minor axis length of the small elliptical segment is designed to be 1 to 1.8.

[0063] Specifically, for the sealing surface of the outer shoulder surface of the threaded joint, the circumferential path during its processing consists of a clockwise half-turn spiral line and a counterclockwise half-turn spiral line, such that the outer shoulder surface after processing is a curved surface with an inclination. And the pitch of the spiral line is preferably 2 to 8 mm. After such a design, when the make-up torque reaches the specified torque, if the downhole torque is further increased, it will cause Figure 16 the originally completely aligned contact surfaces shown in [reference], after turning, to generate an axial length difference ΔL3. And to generate the axial length difference, it is necessary to overcome the frictional force and the normal force on the shoulder surface. Compared with the shoulder surface without inclination, it will have better anti-re-make-up performance. And due to the Poisson effect after deformation, the radial wall thickness of the elongation section at the large end of the outer shoulder continues to increase, which will make the contact performance of the sealing contact surface formed by the cut-off section of the male joint and the thickened section at the large end of the female joint better.

[0064] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the claims described.

Claims

1. A high torsional resistance drill pipe joint for rapid make-up in ultra-deep wells, comprising a male threaded joint and a female threaded joint threadedly connected thereto, and optimizing the tooth profile structures of the male and female threads and the drill pipe joint structure; The male threaded joint is sequentially provided with a male joint outer shoulder surface, a male joint large end stress relief groove, a male joint large end thread topping section, a male joint thread pitch increasing section near the outer shoulder, a male joint middle thread pitch standard section, a male joint thread pitch increasing section near the inner shoulder, a male joint small end extension section and a male joint inner shoulder surface from left to right; The female threaded joint is sequentially provided with a female joint outer shoulder surface, a wall thickness thinning part of the female joint large end extension section, a step of the female joint large end extension section, a wall thickness increasing part of the female joint large end extension section, a female joint thread pitch increasing section near the outer shoulder, a female joint middle thread standard pitch section, a female joint increased thread pitch section near the inner shoulder and a female joint inner shoulder surface from left to right; Both the male joint outer shoulder surface and the female joint outer shoulder surface are irregular sealing surfaces, and the cross-sectional line segments thereof are sequentially composed of an arc segment, a large ellipse segment, a small ellipse segment, an arc segment and a straight line segment from the outer wall to the inner wall, and all the line segments are sequentially tangent; 2. The high-torsion-resistant drill pipe joint for rapid make-up in an extra-deep well according to claim 1, wherein: There is a gap ΔL1 between the small end of the male threaded joint thread and the male joint inner shoulder surface, and the size of the inner shoulder gap ΔL1 is optimized and fitted as: ； Where η is the material mechanical property coefficient, κ is the downhole working temperature correction coefficient, ξ is the sealing performance level correction coefficient, γ is the thread taper angle, R7 is the radius of the small end of the male joint, and R8 is the outer diameter of the female joint.

3. The high anti-torsion drill pipe joint for rapid make-up in ultra-deep wells according to claim 1, wherein: After the last 3 to 5 threads at the large end of the male threaded joint are topped, there is a gap ΔL2 between the thread top surface and the corresponding surface of the female threaded joint. This gap ΔL2 is 0.5 to 1.5 mm, and a sealing rubber strip is filled in the thread groove left after topping; 4. The high-torsion-resistant drill pipe joint for rapid make-up in an extra-deep well according to claim 1, characterized in that: The large end of the female thread contains a step surface, and the ratio range of the length of the step from the nearest thread to the length of the step from the nearest outer shoulder surface is 0.5 to 1.5; 5. The high-torsion-resistant drill pipe joint for rapid make-up in ultra-deep wells according to claim 1, wherein: The cross-section of the two elliptical segments of the outer shoulder surface of the threaded joint of the male threaded joint and the female threaded joint is divided into a large ellipse segment and a small ellipse segment. The ratio of the vertical distance from the tangent point of the large and small ellipse segments to the outer wall and the inner wall is 1.5 to 2. The ratio range of the major axis length of the large ellipse segment to the major axis length of the small ellipse segment is 1.5 to 3, and the ratio range of the minor axis length of the large ellipse segment to the minor axis length of the small ellipse segment is 1 to 1.8; 6. The high-torsion-resistant drill pipe joint for rapid make-up in ultra-deep wells according to claim 1, characterized in that: The sealing surface of the outer shoulder surface of the threaded joint of the male threaded joint and the female threaded joint is composed of a clockwise half-turn spiral line and a counterclockwise half-turn spiral line in the circumferential path during the processing, so that the outer shoulder surface is a curved surface with an inclination after processing, and the spiral pitch is 2 to 8 mm; 7. The high anti-torsion drill pipe joint for rapid make-up in ultra-deep wells according to claim 1, characterized in that: The cross-section shape of the male joint large end stress relief groove is an elliptical line, the major axis of the ellipse is in the axial direction of the threaded joint, the minor axis is in the radial direction of the threaded joint, the elliptical segment near the outer shoulder side is tangent to the straight line segment of the outer shoulder surface, and the included angle between the major axis of the ellipse and the axis of the threaded joint is the same as the thread taper angle.

8. The high-torsion-resistant drill pipe joint for rapid make-up in an extra-deep well according to claim 1, wherein: The male thread increases the angle δ between the thread bearing surface and the tangent line of the tooth root fillet. The tooth profile of the standard section in the middle of the male thread and the female thread has a pitch of 3.5 threads per inch, while the pitch of the thread engagement section on both sides is increased. In addition, the top 3 to 5 threads of the male thread near the outer shoulder are subjected to crown shaving treatment.

9. The high-torsion-resistant drill pipe joint for rapid make-up in an extra-deep well according to claim 8, characterized in that: The angle value of the angle δ between the thread bearing surface and the tangent line of the tooth root fillet is 20 to 30 degrees.

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