High-torsion-resistance drill rod joint for quick screwing-on of ultra-deep well

Abstract

The invention provides a high-torsion-resistance drill rod joint for quick screwing-on of an ultra-deep well. The high-torsion-resistance drill rod joint comprises a male thread joint and a female thread joint in threaded connection with the male thread joint. A gap between a small end of a male thread and an inner shoulder surface is delta L1, a tangent angle delta between a bearing surface and a tooth bottom fillet is increased, the section of an inner shoulder and the section of the outer shoulder are optimally designed to be composed of a fillet section, a large elliptical section, a small elliptical section, a fillet section and a linear section, the inner shoulder surface and the outer shoulder surface are designed to be inclined, step surfaces of a male joint and a female joint are optimally designed, and the male joint is provided with an elliptical stress load-reducing groove. The thread pitch of the two sides of the thread meshing section is increased. According to the scheme, the purposes of eliminating a high-stress area and achieving sealing enhancement are achieved while rigidity matching is achieved, the problems of stress distribution on thread teeth and stress concentration at threads of inner and outer shoulders when male and female threads are meshed are solved, bearing force distribution of meshed threads is optimized, the screwing-on and screwing-off speed of the threaded connector is increased, and the service life of the threaded connector is prolonged. The torsional strength and the sealing performance of the threaded connector of the drill string are improved, and secondary screwing-on accidents are prevented.

Description

Technical Field

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

[0002] In recent years, with the continuous development of a large number of deep wells, ultra-deep wells and even ultra-deep wells of 10,000 meters in the oil and gas extraction 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 the performance of drill pipe materials mainly depends on the progress of material science. Only structural design optimization can improve the performance of drill pipes in a short time. Since the length of a single conventional drill pipe is only 9 to 13 meters, and the drilling depth needs to reach 10,000 meters or even deeper, it is necessary to connect hundreds of drill pipes end to end through threaded joints to form a whole pipe string that can transmit torque. When the drill pipe is working, it must not only withstand huge torque and alternating stress, but also withstand huge drilling fluid pressure in the rod. At the same time, the weight of the entire well section drill pipe can reach 1,000 tons, which puts forward higher requirements for the rapid make-up and make-up of the drill pipe, the rationality of the force distribution of the thread, and the sealing of the joint, so as to avoid the drill pipe threaded joint structure becoming an obstacle to the breakthrough of drilling depth. According to the existing API (American Institute of Petroleum Engineers) standards, oil and gas wells with a depth of 4,500 to 6,000 meters are called deep wells, oil and gas wells with a depth of 6,000 to 9,000 meters are called ultra-deep wells, and oil and gas wells with a depth of more than 9,000 meters are called super-deep wells. At present, the development of ultra-deep wells of 10,000 meters is being carried out in China. Since the designed well depth exceeds 11,000 meters, the service life of devices such as drill bits decreases sharply with the increase in depth, and it is necessary to frequently replace downhole devices such as drill bits. The time required to remove the drill pipe during the replacement process is as long as several days. During this period, the drill pipe needs to be continuously removed from the wellhead, resulting in a weak seal at the wellhead, which is not conducive to wellhead pressure control. In severe cases, even severe accidents such as blowouts may occur. In addition, during the drilling process, the wellhead top drive drilling system or downhole power drilling tools continuously apply torque to the drill pipe, causing the drill pipe joint to be too tight, making it inconvenient to remove 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 Society of Petroleum Engineers. This type of drill pipe joint includes a male thread joint and a female thread joint that can be threadedly connected to each other. The joint body is composed of a tapered pipe thread base, a tapered pipe male thread and a tapered pipe thread front end from the outer shoulder to its end; the female thread joint body that is threadedly engaged with it includes a female thread joint main end face, and on the joint body, from the main end face of the female thread joint along the axial direction from the outside to the inside, there are a female thread base, a tapered pipe female thread and a female thread end hole. The tapered pipe male thread and the tapered hole female thread that are used to engage with each other have the same thread pitch, as well as corresponding thread profiles and thread tapers. When the joint is connected, the outer shoulder surface of the male threaded joint and the main end surface of the female threaded joint are in interference fit with each other, bearing and transmitting the drill pipe torque and acting as a seal. Studies have shown 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 threads of the threaded part. The stress borne by these three threads can reach more than 50% of the total stress, and gradually decreases from the matching shoulder to the front thread, and the front thread bears almost no stress. Therefore, the stress on the thread teeth is extremely uneven, which directly affects the fatigue strength and service life of the joint, making the mechanical strength of the joint cannot be fully utilized. When used in ultra-deep wells or complex wells, due to excessive and concentrated torque, it is very easy to cause failure accidents such as male thread breakage or female thread expansion.

[0004] In response to the above technical problems, the existing Chinese patent proposes a high-torsion-resistant fully sealed drill pipe threaded joint (patent announcement number CN104131788B), which increases the pitch or length of the male and female threads of the rear section of the joint to 1.0 to 1.1 times the pitch of the male and female threads of the front section. When the male and female threaded joint is tightened a certain number of times, the combined threads of the front section produce different elastic deformations than the threads of the rear section. The elastic deformation of the front section is greater than that of the rear section, forcing the force of the rear section threads to be transferred to the front section threads, thereby effectively solving the problem of serious unevenness of the joint connection threads along the length direction. However, the load-bearing side area of ​​the thread is too large, which easily causes increased friction, making it difficult to make and break out the thread, thereby reducing drilling efficiency.

[0005] A Chinese patent discloses a high-torsion-resistant drill threaded joint (application publication number CN105909183A), wherein the preferred thread segment taper range is 1:6 to 1:16, and an interference fit is set between the cylindrical small end of the male threaded joint and the cylindrical large end of the female threaded joint to achieve the purpose of increasing the make-up torque. However, the use of interference contact on the end faces of the male and female joints will lead to difficulties in make-up and make-up, reducing the drilling efficiency. In order to achieve a precise interference size, it will lead to processing difficulties. In the actual drilling process, the torque provided by the wellhead or downhole power drill will inevitably cause secondary make-up to the drill pipe joint, but the severity is different. 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. Once the stress at this point reaches a certain level, it will cause rotational fatigue and even crack initiation 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-sticking function (application publication number CN114320175A) adopts 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 adopts 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 spiral line, and the two spiral lines are arranged in parallel and equidistantly without affecting each other. Therefore, the lead of the double-thread on the same workpiece is doubled than the lead of the single-thread of the same specification. Under the same thread length, the thread tightening stroke is halved, while the tightening speed is increased. However, the double-start thread has its own unique disadvantages such as high manufacturing cost, difficult installation, easy to be affected by the environment, difficult to control the tightening torque, and any damage to the 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 tooth side angle of the thread taper thread is 30°, the second tooth side 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 tooth side angle to 45°, which can increase the radial average thickness of the thread, reduce the fatigue sensitivity of the thread root, and reduce the fatigue or brittle fracture of the thread. However, by increasing the second tooth side angle, the length of the guide thread bearing surface 4 will increase, which increases the friction of the thread contact to a certain extent, resulting in a decrease in the efficiency of threading and unthreading. However, the simple extension section provided at the end of the thread does not alleviate the high stress area near the thread. Even when subjected to a huge axial load, the high stress area expands, which leads to a crack initiation accident in the threaded joint.

[0008] A Chinese patent for a variable tooth width threaded joint (authorization announcement number CN110410024B) preferably has variable tooth width male threaded joints with tooth width enlarged sections on both sides of the meshing section, and an API standard tooth width section in the middle, and the pitches of the male threaded joint and the female threaded joint are equal to the pitches of the API standard threads, thereby solving the problem of large stress concentration at the large end of the male threaded joint when the male and female threads are meshed, optimizing the bearing capacity distribution of the meshing threads, and improving the bearing capacity of the threaded joint. However, on both sides of the male and female threads of the threaded meshing section, variable pitch threads are used respectively to increase the material cross-sectional area of ​​the thread within the same length, thereby improving the strength and improving the high stress distribution. The bearing surface angle is set to 45 degrees, which will increase the bearing surface area, increase the friction, and thus reduce the shackle speed.

[0009] In summary, the present application proposes a high-torsion resistance drill pipe joint for quick 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-torsion resistance drill pipe joint for quick make-up in ultra-deep wells in view of the deficiencies in the prior art, and the high-torsion resistance drill pipe joint for quick make-up in ultra-deep wells can well solve the above problems.

[0011] In order to achieve the above requirements, the technical solution adopted by the present invention is: to provide a high-torsion resistance drill pipe joint for quick make-up in ultra-deep wells, the high-torsion resistance drill pipe joint for quick make-up in ultra-deep wells comprises

[0012] The advantages of this ultra-deep well quick-make-up high-torsion drill pipe joint are as follows:

[0013] 1. By adding an oblique straight line segment to the thread root of the drill pipe threaded 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 a strong bearing capacity, preventing cracks from appearing at the arc of the thread root and causing the threaded joint to break, thereby extending the service life of the drill pipe; the length of the thread bearing surface is also reasonably reduced, thereby reducing the friction force of the drill pipe threaded joint when making and breaking the thread, accelerating the speed of making and breaking the thread, and increasing the efficiency of drilling construction.

[0014] 2. The special contact surface of the inner and outer step surfaces is composed of arc segments, elliptical segments and straight segments, which increases the leakage path length on the shoulder surface, thereby increasing the sealing strength of the threaded joint designed by the present invention. Secondly, during the processing, the circumferential path of the shoulder surface cutting is optimized to be a closed curve composed of a clockwise half-circle spiral line and a counterclockwise half-circle spiral line, which can prevent the secondary buckling phenomenon caused by the torque applied to the threaded joint by the top drive or downhole power drill during the drilling process. The implementation principle is that after the step surface is matched, the axial thickness distribution is not uniform. When the torque value of the threaded joint exceeds the maximum value of the friction force of the step surface and there is a rotation trend, the step slope of the joint will provide a normal force to prevent secondary buckling;

[0015] 3. By increasing the distance L10 from the end of the female connector to the outer shoulder surface, and designing a step in the growth section, the reason for the design of the step surface is that when conducting finite element mechanical analysis on API standard threaded joints, it was found that there was a high stress area near the thread, and there was a huge extrusion pressure on the outer step surface during ultra-deep well drilling, which may cause crushing. Therefore, a step was designed in the growth section of the female connector, so that the thickness of the section near the thread was increased to achieve the purpose of eliminating the high stress area, and the thickness of the part near the outer step surface was reduced. In addition, a stress relief groove was designed at the root of the big end of the male threaded joint, and the root of the big end of the male thread was top-cut for 3 to 5 turns, all of which achieved the purpose of reducing the wall thickness, so that the stiffness of the male and female joints at this location was matched, preventing the big end of the female threaded joint from being crushed during the buckling process and the drill pipe pressure condition, and eliminating the risk of crack initiation in the high stress area;

[0016] 4. By optimizing the inner shoulder gap ΔL1 of the drill pipe joint, after the drill pipe threaded joint is made up, there is an appropriate extrusion pressure between the outer shoulders so that it will not be crushed. The generated contact pressure keeps the outer shoulder sealed, forming a seal of the drill pipe threaded joint. It also allows the inner shoulder to have a reasonable extrusion pressure, generating an inner shoulder seal, forming a seal of the drill pipe threaded joint.

[0017] 5. After chopping, a gap ΔL2 is set between the top surface of the thread and the corresponding surface of the female threaded joint, and the gap is preferably 0.5 to 1.5 mm. The specific working principle is that after the threaded joint is buckled, the outer shoulder is subjected to extrusion force, resulting in Poisson effect, which increases the wall thickness of the large end of the female joint, and the gap ΔL2 will be compressed. After chopping, the sealing rubber strip in the thread groove is compressed and deformed, completely sealing the gap ΔL2, thereby adding a sealing surface to the threaded joint at this location, thereby improving the sealing performance of the threaded joint.

[0018] 6. The surface of the thread is treated with surface nitriding process to form a nitride layer on the surface of the thread to increase the strength of the thread surface and prevent the surface damage of the thread caused by multiple make-up and make-down operations. Secondly, the surface is treated with ultrasonic nano-rolling process to reduce the roughness of the thread surface, reduce friction, and form a compressive stress layer on the thread surface to reduce the resistance to make-up and make-down operations and increase drilling efficiency. The presence of the compressive stress layer on the surface also reduces the initiation of cracks on the thread surface.

[0019] 7. Set up pitch enlargement sections on both sides of the thread engagement section. By using different pitches in different parts of the thread, vibrations of certain frequencies are destroyed and the risk of resonance is reduced. Finite element analysis shows that high stress areas appear on both sides of the thread engagement. By increasing the pitch, the thread line density is reduced. Within the same length, the material cross-sectional area of ​​the thread is larger, thereby improving the strength and the area of ​​high stress distribution, so that the threaded connection has better performance 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 constitute a part of the present application. The same reference numerals are used in these drawings to represent the same or similar parts. The exemplary embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0021] Figure 1 It is a schematic diagram of the assembly of a high-torsion drill pipe threaded joint for quick make-up in ultra-deep wells according to an embodiment of the present invention;

[0022] Figure 2 A three-dimensional cross-sectional schematic diagram of a high-torsion-resistant drill pipe female threaded joint for quick make-up in ultra-deep wells according to an embodiment of the present invention;

[0023] Figure 3 A three-dimensional cross-sectional schematic diagram of a high-torsion-resistant drill pipe male threaded joint for quick make-up in ultra-deep wells according to an embodiment of the present invention;

[0024] Figure 4 This is the stress distribution cloud diagram of the drill pipe threaded joint after the make-up is completed as recommended by the API standard;

[0025] Figure 5 It is a schematic cross-sectional plan view of a high-torsion drill pipe threaded joint for quick make-up in ultra-deep wells according to an embodiment of the present invention;

[0026] Figure 6 It is a schematic diagram of the cross-sectional structure of a drill pipe threaded female joint according to an embodiment of the present invention;

[0027] Figure 7 It is a schematic cross-sectional structure diagram of a drill pipe threaded male joint according to an embodiment of the present invention;

[0028] Figure 8 It is a schematic diagram of the local thread structure dimensions when the female thread member and the male thread member according to an embodiment of the present invention are engaged;

[0029] Fig. 9 It is a schematic diagram of the cross-sectional dimensions of the drill pipe threaded female joint according to an embodiment of the present invention;

[0030] Fig.10 It is a schematic diagram of the cross-sectional dimensions of a drill pipe threaded male joint according to an embodiment of the present invention;

[0031] Fig.11 It is a schematic diagram of the enlarged structural dimensions of the inner shoulder of the drill pipe joint according to an embodiment of the present invention;

[0032] Fig.12 It is a schematic diagram of the enlarged structural dimensions of the outer shoulder of the drill pipe joint according to an embodiment of the present invention;

[0033] Fig.13 It is a schematic diagram of the enlarged structural dimensions of the step and stress relief groove at the outer shoulder of the drill pipe joint according to an embodiment of the present invention;

[0034] Fig.14 It is a schematic diagram of the cross-sectional structure of the outer shoulder of the drill pipe joint according to an embodiment of the present invention;

[0035] Fig.15 A schematic diagram of a cutting process path at an outer shoulder of a drill pipe joint according to an embodiment of the present invention;

[0036] Fig.16 The figure is a schematic diagram of the structure of the irregular shoulder surface designed by the present invention before and after working.

[0037] Among them: 1. Male threaded joint; 11. External shoulder surface of female joint; 12. Thinning wall thickness of the extended section of the large end of the female joint; 13. Step of the extended section of the large end of the female joint; 14. Increased wall thickness of the extended section of the large end of the female joint; 15. The increased thread pitch section of the female joint near the external shoulder; 16. The standard thread pitch section in the middle of the female joint; 17. The increased thread pitch section of the female joint near the internal shoulder; 18. The internal shoulder surface of the female joint; 2. Female threaded joint; 21. Male joint 1. External shoulder surface of the head; 22. Stress relief groove at the big end of the male connector; 23. Chamfered thread section at the big end of the male connector; 24. Thread pitch increased section near the external shoulder of the male connector; 25. Standard thread pitch section in the middle of the male connector; 26. Thread pitch increased section near the internal shoulder of the male connector; 27. Extension section at the small end of the male connector; 28. Internal shoulder surface of the male connector; 3. Thread engagement relaxation surface; 4. Thread engagement bearing surface; 5. Internal shoulder clearance of the threaded connector; 6. Sealing rubber strip. DETAILED DESCRIPTION

[0038] In order to make the objectives, technical solutions and advantages of the present application more clear, the present application is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

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

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

[0041] See also 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. The specific drill pipe joint is fixed by welding at both ends of the drill pipe. In the actual drilling process, the male threaded joint on 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 length 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. Multiple drill pipes are connected in sequence through the threaded connection of the drill pipe joint to complete the drilling operation. At the same time, Figures 1 to 3 As shown, both the male threaded joint and the female threaded joint are hollow structures, and drill pipe inner annuli are provided inside the structures.

[0042] See also Figure 4 This figure shows the stress distribution diagram of the drill pipe threaded joint recommended by the API standard after the finite element mechanical analysis is completed. From the figure, it can be found that there are dark high-stress areas at the last threads at both ends of the threaded joint, and there is a large area of ​​high-stress area in the extension section of the female joint, which even extends to the outer wall of the drill pipe, causing crack initiation and subsequent fracture failure during use in ultra-deep wells. Therefore, this structure is not the optimal structure.

[0043] See also Figures 5 to 7 and Fig.11In this embodiment, the key parts of the drill pipe threaded joint include the outer shoulder surface 11 of the female joint, the wall thickness thinning part 12 of the extension section of the large end of the female joint, the step 13 of the extension section of the large end of the female joint, the wall thickness increased part 14 of the extension section of the large end of the female joint, the increased thread pitch section 15 of the female joint near the outer shoulder, the standard thread pitch section 16 of the middle part of the female joint, the increased thread pitch section 17 of the female joint near the inner shoulder, the inner shoulder surface 18 of the female joint, the outer shoulder surface 21 of the male joint, the stress relief groove 22 of the large end of the male joint, the top cutting section 23 of the large end of the male joint, the increased thread pitch section 24 of the male joint near the outer shoulder, the standard thread pitch section 25 of the middle part of the male joint, the increased thread pitch section 26 of the male joint near the inner shoulder, the extension section 27 of the small end of the male joint, the inner shoulder surface 28 of the male joint, The inner shoulder gap 5 of the threaded 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, forming a seal of the drill string joint, and the drill pipe thread continues to be screwed in. 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 reach the rated torque T2, the inner shoulders will contact and generate extrusion pressure, and the male thread and the female thread will mesh to form a seal of the drill string joint, and the male joint large end thread top cutting section 23 and the female joint large end extension section with increased wall thickness 14 will also contact and generate extrusion pressure to form a seal of the drill string joint.

[0044] Specifically, during the process of making up the drill string joint, as the male joint 2 and the female joint 1 contact at the outer shoulder and begin to generate extrusion pressure, the gap ΔL1 of the inner shoulder also decreases accordingly, until the inner shoulder surface 28 of the male threaded joint and the inner shoulder surface 18 of the female threaded joint come into contact and generate extrusion pressure. Since the outer shoulder surface of the drill string joint contacts before the inner shoulder surface, and when the make-up torque reaches the interval from 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, in order to ensure that the contact strength generated by the extrusion pressure between the inner shoulder surfaces meets the design requirements, and the extrusion pressure of the outer shoulder cannot crush the structure 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 to be just right. For this purpose, the drill string inner shoulder gap ΔL1 is optimized to fit as ΔL1∝1 / 2·η·κ·ξ·(R8-R7)·tan(γ), where η is the material mechanical property coefficient, κ is the downhole working temperature correction coefficient, ξ is the sealing performance level correction coefficient, and γ is the thread taper angle.

[0045] Reference Figure 8In this embodiment, the key structural parameters of the thread meshing part include the tooth side angle α between the load-bearing surface 4 and the radial direction of the tube body, the tooth side angle β between the relaxation surface 3 and the radial direction of the tube body, the pipe thread taper γ, the tangent angle δ between the thread load-bearing surface 4 and the tooth bottom fillet, the male and female thread pitch p, the theoretical thread crest height H1, the thread profile height before truncation H2, the crest flattening height H3, the tooth bottom truncation height H4, the load-bearing surface buckle root fillet radius R1, the guide surface buckle root fillet radius R2, and the crest fillet radius R3;

[0046] The main improvements of the specific thread sealing surface are: setting the angle δ between the thread bearing surface 4 and the tangent line of the tooth bottom fillet to reduce the bearing surface area and the wall thickness of the male thread tooth root;

[0047] Specifically, the tooth side angle of the thread bearing surface 4 and the tooth side angle of the relaxation surface 3 are increased, and the average thickness of the thread bearing surface 4 is increased, so as to increase the torque bearing capacity and the bearing capacity of the axial compression load to which the drill pipe is subjected during the drilling process;

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

[0049] Specifically, the angle δ between the thread bearing surface 4 and the tooth bottom fillet tangent is set to reduce the friction contact area of ​​the thread bearing surface 4, thereby reducing the make-up time of the drill pipe threaded joint and achieving rapid make-up;

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

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

[0052] Specifically, 3 to 5 threads of male thread are selected for top cutting at the male thread big end top cutting 23 of the male joint, and the wall thickness of the male thread joint at this part is reduced so that the stiffness of the male and female joints at this part is matched, thereby preventing the big end of the female thread from being crushed during the make-up process and the drill pipe pressure condition;

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

[0054] Reference Fig.10 In this embodiment, the key dimensions of the drill pipe threaded female joint 1 include the length of the female threaded joint L6, the distance from the intersection of the small end of the female threaded joint and the thread to the outer shoulder L7, the distance from the base surface of the female joint thread to the outer shoulder L8, the distance from the intersection of the large end of the female joint thread and the thread to the outer shoulder L9, the length of the reduced wall thickness section of the large end of the female joint thread L10, the distance from the large end of the female joint thread to the increased wall thickness section L10, the outer diameter of the female joint R8, the inner diameter of the reduced wall thickness section of the large end of the female joint R9, the inner diameter of the increased wall thickness section of the large end of the female joint R10, the middle diameter of the base surface of the female joint thread R11, the outer diameter of the small end of the female joint R12, the inner diameter of the female joint R13, 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 cut top section of the drill pipe male joint and the thickened section of the large end of the female joint.

[0055] Specifically, the extension part of the big end of the female joint is lengthened compared with the provisions of the API standard, and a step 13 is added to make the wall thickness of the extended section different. The wall thickness near the outer platform is smaller, and the stiffness of the female threaded joint in this part is reduced, so that the stiffness of the male and female joints at this location matches, preventing the big end of the female threaded joint from being crushed during the make-up process and under pressure conditions of the drill pipe, and increasing the stiffness near the thread extension section 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 joint of the drill pipe and the thickened section at the large end of the female joint, so that after the make-up is completed, the female joint is subjected to pressure, and the radial wall thickness of the extended section at the large end of the female joint increases due to the Poisson effect, so that the gap ΔL2 can be closed, and a sealing rubber strip 6 is embedded in the incomplete thread groove of the male thread after the cut-off section, that is, a sealing surface is added to the threaded joint, so as to improve the sealing performance of the threaded joint.

[0057] Reference Fig.11 A threaded joint inner shoulder gap 5 is formed between the male joint's thread pitch enlarged section 26 near the inner shoulder and the female joint's middle thread standard pitch section 16.

[0058] Reference Fig.13 In this embodiment, the stress relief groove at the big end of the male connector and the step at the extended section of the big end of the female connector are designed as elliptical surfaces, in which the major axis size 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] The specific design of the inclination angle of the major axis of the ellipse being the same as the taper angle of the thread is based on a large number of finite element calculations, after which it was found that the stress distribution of traditional circular groove type or flat-bottomed load-reducing grooves does not have a uniform cross-sectional distribution that fits the taper angle inclination angle of the thread. Therefore, it is preferred that the inclination angle of the major axis of the ellipse be the same as the taper angle of the thread.

[0060] Reference Figures 14 to 16 In this embodiment, the shoulder surface is designed to consist of a fillet segment, a large ellipse segment, a small ellipse segment, a fillet segment, and a straight line segment from the outer wall to the inner wall, and all the line segments are sequentially tangent, wherein the structural parameters include the fillet radius R14 close to the outer wall of the joint, the fillet radius R15 close to the inner wall of the joint, the major axis size a2 of the large ellipse, the minor axis size b2 of the large ellipse, the major axis size a3 of the small ellipse, the minor axis size 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 of the straight line segment L14.

[0061] The specific design is to design the outer shoulder large ellipse close to the outer wall of the drill string. The design reason is that Figure 4 The analysis found that there is a high stress area on the contact surface of the outer shoulder. In the process of bearing torque and internal and external pressure, the shear stress close to the outer wall is greater, resulting in a stress concentration area near the outer wall of the outer shoulder. In order to reduce the stress concentration caused by the irregular shape of the structure, the large ellipse of the outer shoulder is designed close to the outer wall of the drill string.

[0062] Specifically, after optimization, the distance ratio between the tangent point of the ellipse segment and the outer wall and the inner wall is designed to be 1.5 to 2, the ratio of the major axis length of the large ellipse segment to the major axis length of the small ellipse segment is designed to be 1.5 to 3, and the ratio of the minor axis length of the large ellipse segment to the minor axis length of the small ellipse segment is designed to be 1 to 1.8.

[0063] The sealing surface of the outer shoulder surface of the threaded joint has a circumferential path during the processing, which consists of a clockwise half-circle spiral line and a counterclockwise half-circle spiral line, so that the outer shoulder surface is a curved surface with an inclination after processing, and the helical pitch is preferably 2 to 8 mm. After the make-up torque reaches the specified torque, the downhole torque is further increased, which will lead to Fig.16 The contact surfaces that were originally completely aligned as shown in the figure result in an axial length difference of ΔL3 after turning. The axial length difference requires overcoming the friction force of the shoulder surface and the normal force on the shoulder surface. Compared with the shoulder surface without an inclination, it will have better anti-secondary buckling performance. Moreover, after deformation, due to the Poisson effect, the radial wall thickness of the extended 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 chamfered section of the male joint and the thickened section at the large end of the female joint better.

[0064] The above-mentioned embodiments only represent several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the claims.

Claims

1. A high-torsion drill pipe joint for quick make-up in ultra-deep wells, comprising a male threaded joint and a female threaded joint threadedly connected thereto, and optimizing the male and female thread tooth structures and the drill pipe joint structure; The male threaded joint is provided with a male joint outer shoulder surface 21, a stress relief groove 22 at the male joint large end, a male joint large end thread top cutting section 23, a male joint thread pitch enlarged section 24 near the outer shoulder, a male joint middle thread pitch standard section 25, a male joint thread pitch enlarged section 26 near the inner shoulder, a male joint small end extension section 27 and a male joint inner shoulder surface 28 in sequence from left to right; The female threaded joint is provided with a female joint outer shoulder surface 11, a female joint large end extension section wall thickness thinning portion 12, a female joint large end extension section step 13, a female joint large end extension section wall thickness increased portion 14, a female joint thread pitch enlarged section 15 near the outer shoulder, a female joint middle thread standard pitch section 16, a female joint thread pitch enlarged section 17 near the inner shoulder and a female joint inner shoulder surface 18 in sequence from left to right; The male joint outer shoulder surface 21 and the female joint outer shoulder surface 11 are both irregular sealing surfaces, and their cross-sectional line segments from the outer wall to the inner wall are composed of an arc segment, a large ellipse segment, a small ellipse segment, an arc segment, and a straight line segment in sequence, and all the line segments are sequentially tangent.

2. According to claim 1, a high-torsion resistance drill pipe joint for quick make-up in ultra-deep wells, characterized in that: There is a gap ΔL1 between the small end of the male threaded joint thread and the inner shoulder surface 28 of the male joint, and the size of the inner shoulder gap ΔL1 is optimized and fitted as follows: △L1∝1 / 2·η·κ·ξ·(R8-R7)·tan(γ); Where η is the material mechanical property coefficient, κ is the downhole working temperature correction coefficient, ξ is the sealing performance level correction coefficient, and γ is the thread taper angle.

3. According to claim 1, a high-torsion resistance drill pipe joint for quick make-up in ultra-deep wells, characterized in that: After the last 3 to 5 threads of the male threaded joint are chamfered, there is a gap ΔL2 between the top surface of the thread and the corresponding surface of the female threaded joint. The gap ΔL2 is preferably 0.5 to 1.5 mm, and a sealing rubber strip is filled in the thread groove left after chamfering.

4. According to claim 1, a high-torsion resistance drill pipe joint for quick make-up in ultra-deep wells, characterized in that: The large end of the female thread includes a step surface, and the ratio of the length of the step to the nearest thread to the length of the step to the nearest outer shoulder surface is in the range of 0.5 to 1.

5.

5. According to claim 1, a high-torsion resistance drill pipe joint for quick make-up in ultra-deep wells, characterized in that: The two elliptical segments of the cross-section of the outer shoulder surface of the threaded joint are divided into a large elliptical segment and a small elliptical segment, wherein the ratio of the vertical distances between the tangent points of the large and small elliptical segments and the outer and inner walls is 1.5 to 2, the ratio of the major axis length of the large elliptical segment to the major axis length of the small elliptical segment ranges from 1.5 to 3, and the ratio of the minor axis length of the large elliptical segment to the minor axis length of the small elliptical segment ranges from 1 to 1.

8.

6. The high-torsion resistance drill pipe joint for quick 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 has a circumferential path during the processing consisting of a clockwise half-circle spiral line and a counterclockwise half-circle spiral line, so that the outer shoulder surface is a curved surface with an inclination after processing, and the helical pitch is preferably 2 to 8 mm.

7. The high-torsion resistance drill pipe joint for quick make-up in ultra-deep wells according to claim 1, characterized in that: The cross-sectional shape of the stress relief groove 22 at the large end of the male joint is an elliptical line, with the major axis of the ellipse in the axial direction of the threaded joint and the minor axis in the radial direction of the threaded joint. The elliptical line segment close to the outer shoulder side is tangent to the straight line segment of the outer shoulder surface, and the angle between the major axis of the ellipse and the axis of the threaded joint is the same as the taper angle of the thread.

8. The high-torsion resistance drill pipe joint for quick make-up in ultra-deep wells according to claim 1, characterized in that: The male thread increases the tangent angle δ between the thread bearing surface 4 and the tooth bottom fillet. The standard pitch of the middle section of the male and female threads is 3.5 teeth per inch, while the pitch of the thread engagement sections on both sides is increased, and the male thread is top-cut 3 to 5 turns near the external shoulder.

9. The high-torsion resistance drill pipe joint for quick make-up in ultra-deep wells according to claim 8, characterized in that: The angle value of the tangent angle δ between the groove bearing surface 4 and the tooth bottom fillet is preferably 20 to 30 degrees.

Images