Drill rod thread structure with stress reducing groove and machining method

Abstract

The invention belongs to the technical field of oil drilling, and particularly relates to a drill rod thread structure with a stress reducing groove and a machining method. An external thread joint main shoulder surface, an external thread joint stress reducing groove, an external thread joint auxiliary shoulder surface and an external thread joint taper pipe thread are arranged on the external thread connection main body; one end of the internal thread connector body is connected with a drill rod, the other end of the internal thread connector body is a threaded connecting section, and an internal thread connector main shoulder face, an internal thread connector stress reducing groove, an internal thread connector auxiliary shoulder face and internal thread of an internal thread connector taper pipe are arranged on the internal thread connector body. The external thread of the external thread connector taper pipe and the internal thread of the internal thread connector taper pipe are connected in a matched mode to bear axial loads, and the main shoulder face of the external thread connector makes contact with the main shoulder face of the internal thread connector to bear torque during connection. The maximum stress of the drill rod thread during working can be reduced, and the service life of the drill rod thread is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of petroleum drilling technology, specifically relating to a drill pipe thread structure with stress-reducing grooves and its processing method. Background Technology

[0002] As oil drilling and exploration activities extend to deeper, more complex, and more challenging geological conditions, higher demands are placed on the technical performance and reliability of drill pipe threads. Due to stress concentration at the thread root, torque, and working load, the threaded connection of the drill pipe becomes a weak point. Furthermore, during operation, the drill pipe is subject to geological corrosion, frequently leading to drill pipe failures such as thread breakage and sticking, causing significant economic losses to drilling production.

[0003] Against this backdrop, many researchers both domestically and internationally have conducted extensive studies on this issue. Chinese patent CN201821991784.9 describes a double-shoulder stress-relieving threaded component, and Grant's XT and HT series products from the United States have made progress in improving stress distribution through the double-shoulder structure. This can increase the connection strength of the thread and is beneficial for use in deep wells. However, it cannot reduce the stress value at the root of the thread connection, and the possibility of root failure at the thread connection still exists. Furthermore, it is difficult to guarantee the installation and fitting accuracy of the drill pipe under actual working conditions, and it cannot be guaranteed that the thread will always work under the double shoulders, affecting the sealing performance.

[0004] Chinese patent CN214660001U designs a high-torque drill pipe thread structure that improves the torque resistance of the drill pipe thread by changing the taper of the tapered pipe thread. This solution can improve the load-bearing capacity of the thread to a certain extent, but it cannot reduce the stress value at the threaded connection.

[0005] Chinese patent CN205858205U designs a trapezoidal threaded joint, which can increase the contact area of ​​the drill rod, making the stress on the drill rod thread more uniform. At the same time, the interference between the external thread crest and the internal thread root is relatively small, which can further increase the strength of the drill rod thread and improve its service life. Although this solution can improve the connection strength of the drill rod thread, it cannot reduce the stress value at the connection of the drill rod thread. Furthermore, the trapezoidal thread is more difficult to process, and the sealing performance of the drill rod thread during operation cannot be guaranteed, which increases the manufacturing cost. Summary of the Invention

[0006] The purpose of this invention is to provide a drill pipe thread structure with stress-reducing grooves and a processing method to solve the technical problem of low service life caused by stress and large load on the main shoulder in the prior art.

[0007] To achieve the above objectives, the present invention employs the following technical solution: The first invention is a drill pipe thread structure with an attached stress-reducing groove, comprising: An external threaded connector includes an external threaded connector body, on which an axially extending external threaded connector tapered pipe thread is provided. An external threaded connector stress-reducing groove is provided at the root of the external threaded connector tapered pipe thread. An external threaded connector main shoulder is provided at the other end of the external threaded connector stress-reducing groove, and an external threaded connector secondary shoulder is provided at the end of the external threaded connector tapered pipe thread, which is radially inward. An internal threaded connector includes an internal threaded connector body, on which an axially extending internal thread of a tapered tube is provided. An internal threaded connector stress-reducing groove is formed at the root of the internal thread of the tapered tube. A radially outward-facing secondary shoulder is provided on the other side of the stress-reducing groove. A radially inward-facing primary shoulder is provided at the end of the internal thread of the tapered tube. An internal and external threaded connector cavity is formed axially inside the internal threaded connector body. The external threaded connector tapered tube thread meshes with the internal thread of the tapered tube.

[0008] Preferably, the main shoulder of the internal threaded connector is in contact with the main shoulder surface of the external threaded connector; the main shoulder surface of the external threaded connector is connected to the stress-reducing groove of the external threaded connector through the fillet of the external threaded connector, and the other end of the main shoulder of the external threaded connector is connected to the outer edge of the external threaded connector.

[0009] Preferably, the radius of the fillet of the external threaded connector is not greater than the outer diameter of the external thread chamfer.

[0010] Preferably, a transition section is provided between the tapered pipe thread of the external threaded connector and the shoulder of the external threaded connector.

[0011] Preferably, the external threaded connector shoulder and the internal threaded connector shoulder are arranged opposite to each other, and their opposite surfaces are the external threaded connector shoulder surface and the internal threaded connector shoulder surface, respectively, with a gap between the external threaded connector shoulder surface and the internal threaded connector shoulder surface.

[0012] Preferably, the shoulder surface of the internal threaded connector and the stress-reducing groove of the internal threaded connector are connected by a chamfer of the internal threaded connector.

[0013] Preferably, the stress-reducing groove of the external threaded joint has a length of 15~26mm, and the stress-reducing groove of the external threaded joint and the tapered pipe thread of the external threaded joint are rounded.

[0014] Preferably, the stress-reducing groove of the internal threaded joint has a length of 15~26mm.

[0015] Preferably, the taper of both the external threaded connector tapered pipe thread and the internal threaded body tapered pipe thread is 1:6.

[0016] The second invention provides a method for machining a drill pipe thread structure with an attached stress-reducing groove, comprising: After cutting the first thread at the root of the tapered pipe thread on the main body of the external threaded connector, a stress-reducing groove for the external threaded connector is set between the main shoulder of the external thread and the root of the tapered pipe thread of the external threaded connector. After the first thread of the internal thread tapered tube on the internal thread connector body is cut, a stress-reducing groove for the internal thread connector is set between the secondary shoulder of the internal thread connector and the root of the internal thread tapered tube; and the internal and external thread connector cavity is machined axially inside the internal thread connector body.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This application discloses a drill pipe thread structure with stress-reducing grooves. The drill pipe is fastened by corresponding mating of the external threaded connector tapered tube thread and the internal threaded body tapered tube thread. The drill pipe body structure adopts a double-shoulder structure, with external threaded connector secondary shoulders and internal threaded connector secondary shoulders respectively provided on the original single-shoulder structure. The purpose is to distribute the torque borne by the main shoulder and reduce the load on the main shoulder. In order to reduce the maximum stress value of the drill pipe thread during operation and reduce the stress of the first three threads of the drill pipe thread during operation, this application adopts the API standard to set stress-reducing grooves for both the external threaded connector and the internal threaded connector of the double-shoulder drill pipe thread. This application reduces the maximum stress value of the internal and external threads of the drill pipe thread itself during operation through structural improvements, reduces the stress of the first three threads of the drill pipe thread during operation, and improves the service life of the drill pipe thread; it also reduces the contact pressure of the first three threads of the drill pipe thread connection and the main shoulder surface, and increases the contact pressure of the last three threads of the drill pipe connection and the secondary shoulder surface, thereby improving the sealing performance of the drill pipe thread. The root stress value at the fillet of the shoulder of the external thread is reduced, thus reducing the load on the shoulder of the external thread.

[0018] Furthermore, this application provides a transition section between the tapered pipe thread of the external threaded connector and the secondary shoulder of the external threaded connector, thereby reducing the gap between the secondary shoulder surface of the external threaded connector and the secondary shoulder surface of the internal threaded connector, reducing the equivalent stress at the large end during connection, improving the distribution of equivalent stress and contact pressure in the direction of the thread generatrix, and enhancing the sealing performance of the threaded connection. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the internal threaded connector of the present invention; Figure 3 This is a schematic diagram of the external threaded connector of the present invention; Figure 4 This is a partially enlarged view of the present invention.

[0021] Wherein: 1-Main body of external threaded connector; 2-Outer edge of external threaded connector; 3-Main shoulder surface of external threaded connector; 4-Round corner of external threaded connector; 5-Stress-reducing groove of external threaded connector; 6-Tapered pipe thread of external threaded connector; 7-Transition section; 8-Secondary shoulder surface of external threaded connector; 9-Main shoulder surface of internal threaded connector; 10-Outer edge of internal threaded connector; 11-Internal thread tapered pipe internal thread of internal threaded connector; 12-Stress-reducing groove of internal threaded connector; 13-Chamfer of internal threaded connector; 14-Secondary shoulder surface of internal threaded connector; 15-Cavity of internal and external threaded connector; 16-Main body of internal threaded connector; 17-Secondary shoulder gap. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0024] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0025] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0026] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0027] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0028] The present invention will now be described in further detail with reference to the accompanying drawings: This application discloses a drill pipe thread structure with stress-reducing grooves, including: External threaded connector, see Figure 3 The external threaded connector includes an external threaded connector body 1, on which an axially extending external threaded connector tapered pipe thread 6 is provided. An external threaded connector stress-reducing groove 5 is provided at the root of the external threaded connector tapered pipe thread 6. An external threaded connector main shoulder is provided at the other end of the external threaded connector stress-reducing groove 5, and an external threaded connector secondary shoulder is provided at the end of the external threaded connector tapered pipe thread 6, which is radially inward. Internal threaded connector, see Figure 2 The internal threaded connector includes an internal threaded connector body 16, on which an axially extending internal thread 11 is provided. An internal threaded connector stress-reducing groove 12 is formed at the root of the internal threaded connector tapered tube internal thread 11. A radially outward-facing internal threaded connector secondary shoulder is provided on the other side of the internal threaded connector stress-reducing groove 12. A radially inward-facing internal threaded connector main shoulder is provided at the end of the internal threaded connector tapered tube internal thread 11. An internal and external threaded connector cavity 15 is formed axially inside the internal threaded connector body 16. The external threaded connector tapered tube thread 6 meshes with the internal threaded connector tapered tube internal thread 11. (See also...) Figure 1This application discloses a drill pipe thread structure with stress-reducing grooves. The drill pipe is fastened by corresponding mating of the external threaded connector tapered tube thread and the internal threaded body tapered tube thread. The drill pipe body structure adopts a double-shoulder structure. External threaded connector secondary shoulders and internal threaded connector secondary shoulders are respectively provided on the external and internal threads of the original single-shoulder structure. The purpose is to distribute the torque borne by the main shoulder and reduce the load on the main shoulder. To reduce the maximum stress value of the drill pipe thread during operation and the stress of the first three threads, this application adopts the API standard to provide external threaded connector stress-reducing grooves and internal threaded connector stress-reducing grooves for the double-shoulder drill pipe thread. This application reduces the maximum stress value of the internal and external threads themselves during operation through structural improvements, reduces the stress of the first three threads of the drill pipe thread during operation, and improves the service life of the drill pipe thread. It also reduces the contact pressure of the first three threads and the main shoulder surface at the drill pipe thread connection, increases the contact pressure of the last three threads and the secondary shoulder surface at the drill pipe connection, and improves the sealing performance of the drill pipe thread. The root stress value at the fillet of the shoulder of the external thread is reduced, thus reducing the load on the shoulder of the external thread.

[0029] In some embodiments, see Figure 1 , Figure 2 and Figure 3 A drill pipe thread structure with stress-reducing grooves, comprising: An external threaded connector, comprising an external threaded connector body 1, an axially extending external threaded connector tapered pipe thread 6 provided on the external threaded connector body 1, an external threaded connector stress-reducing groove 5 provided at the root of the external threaded connector tapered pipe thread 6, an external threaded connector main shoulder provided at the other end of the external threaded connector stress-reducing groove 5, and an external threaded connector secondary shoulder provided at the end of the external threaded connector tapered pipe thread 6, which is radially inward. An internal threaded connector includes an internal threaded connector body 16, on which an axially extending internal thread 11 is provided. An internal threaded connector stress-reducing groove 12 is formed at the root of the internal threaded connector tapered tube internal thread 11. A radially outward-facing internal threaded connector secondary shoulder is provided on the other side of the internal threaded connector stress-reducing groove 12. A radially inward-facing internal threaded connector main shoulder is provided at the end of the internal threaded connector tapered tube internal thread 11. An internal and external threaded connector cavity 15 is formed axially inside the internal threaded connector body 16. An external threaded connector tapered tube thread 6 engages with the internal threaded connector tapered tube internal thread 11. The internal threaded connector main shoulder contacts the external threaded connector main shoulder surface 3 of the external threaded connector main shoulder. The external threaded connector main shoulder surface 3 connects to the external threaded connector stress-reducing groove 5 through an external threaded connector fillet 4. The other end of the external threaded connector main shoulder connects to the outer edge 2 of the external threaded connector.

[0030] More preferably, the radius of the fillet 4 of the external thread connector is not greater than the outer diameter of the external thread chamfer. That is, the radius of the fillet of the external thread connector is between the design size and the outer diameter of the external thread main shoulder chamfer. This reduces the root stress value at the fillet of the external thread main shoulder of the drill pipe thread.

[0031] In some embodiments, a transition section 7 is provided between the tapered pipe thread 6 of the external threaded connector and the shoulder of the external threaded connector.

[0032] In some embodiments, a drill pipe thread structure with stress-reducing grooves includes: An external threaded connector, comprising an external threaded connector body 1, an axially extending external threaded connector tapered pipe thread 6 provided on the external threaded connector body 1, an external threaded connector stress-reducing groove 5 provided at the root of the external threaded connector tapered pipe thread 6, an external threaded connector main shoulder provided at the other end of the external threaded connector stress-reducing groove 5, and an external threaded connector secondary shoulder provided at the end of the external threaded connector tapered pipe thread 6, which is radially inward. An internal threaded connector includes an internal threaded connector body 16, on which an axially extending internal thread 11 is provided. An internal threaded connector stress-reducing groove 12 is formed at the root of the internal threaded connector tapered tube internal thread 11. A radially outward-facing internal threaded connector secondary shoulder is provided on the other side of the internal threaded connector stress-reducing groove 12. A radially inward-facing internal threaded connector main shoulder is provided at the end of the internal threaded connector tapered tube internal thread 11. An internal and external threaded connector cavity 15 is formed axially inside the internal threaded connector body 16. An external threaded connector tapered tube thread 6 engages with the internal threaded connector tapered tube internal thread 11. The internal threaded connector main shoulder contacts the external threaded connector main shoulder surface 3 of the external threaded connector main shoulder. The external threaded connector main shoulder surface 3 connects to the external threaded connector stress-reducing groove 5 through an external threaded connector fillet 4. The other end of the external threaded connector main shoulder connects to the outer edge 2 of the external threaded connector.

[0033] The auxiliary shoulder of the external threaded connector is arranged opposite to the auxiliary shoulder of the internal threaded connector, with their opposing surfaces being the auxiliary shoulder surface 8 of the external threaded connector and the auxiliary shoulder surface 14 of the internal threaded connector, respectively. The gap between the auxiliary shoulder surface 8 of the external threaded connector and the auxiliary shoulder surface 14 of the internal threaded connector is no greater than 0.16mm. This reduces the contact pressure of the first three threads and the main shoulder surface of the drill pipe thread connection, increases the contact pressure of the last three threads and the auxiliary shoulder surface at the drill pipe connection, and improves the sealing performance of the drill pipe thread during operation.

[0034] In some embodiments, the internal threaded connector sub-shoulder surface 14 and the internal threaded connector stress-reducing groove 12 are connected by an internal threaded connector chamfer 13.

[0035] In some embodiments, the stress-reducing groove 5 of the external threaded connector has a length of 15~26mm, and the stress-reducing groove 5 of the external threaded connector and the tapered pipe thread 6 of the external threaded connector are rounded.

[0036] In some embodiments, the length of the stress-reducing groove 12 of the internal threaded joint is 15~26mm.

[0037] In some embodiments, this application provides a drill pipe thread structure with stress-reducing grooves, which can reduce the stress value at the drill pipe thread connection. The drill pipe is fastened after being engaged with the internal thread of the internal thread body tapered tube 11 through the external threaded connector tapered tube thread 6. The body structure of the drill pipe adopts a double shoulder structure. On the original single shoulder structure, an external threaded connector secondary shoulder and an internal threaded connector secondary shoulder are respectively provided for the external threaded connector tapered tube thread 6 and the internal thread body tapered tube thread 11. The purpose is to distribute the torque borne by the main shoulder and reduce the load on the main shoulder.

[0038] In order to reduce the maximum stress value of the drill pipe thread during operation and reduce the stress of the first three threads of the drill pipe thread during operation, this application adopts the API standard to set stress-reducing grooves for double-shoulder drill pipe threads. This includes an external thread joint stress-reducing groove 5 set between the main shoulder of the external thread and the root of the external thread joint tapered pipe thread 6, and an internal thread joint stress-reducing groove 12 opened at the root of the secondary shoulder of the internal thread joint and the internal thread body tapered pipe internal thread 11.

[0039] In order to reduce the contact pressure of the first three threads and the main shoulder of the drill pipe threaded connection, increase the contact pressure of the last three threads and the secondary shoulder of the drill pipe connection, and improve the sealing performance of the drill pipe thread during operation, this application reduces the gap between the secondary shoulder 8 of the external threaded joint and the secondary shoulder 14 of the internal threaded joint during the design and processing.

[0040] In order to reduce the root stress value at the fillet of the main shoulder of the external thread of the drill pipe, the fillet between the stress-reducing groove of the external thread and the main shoulder is optimized based on the above two measures.

[0041] This application also discloses a method for machining a drill pipe thread structure with stress-reducing grooves, including: After the first thread of the external thread tapered pipe thread 6 at the root of the external thread connector body 1 is cut, an external thread connector stress-reducing groove 5 is set between the external thread main shoulder and the root of the external thread tapered pipe thread 6. After the first thread of the internal thread tapered tube internal thread 11 on the internal thread connector body 16 is cut, an internal thread connector stress-reducing groove 12 is provided between the internal thread connector secondary shoulder and the root of the internal thread tapered tube internal thread 11; and the internal and external thread connector cavity 15 is machined axially inside the internal thread connector body 16.

[0042] The threads of the double-shoulder drill pipe are machined according to the above method, such as... Figure 1 , Figure 2 and Figure 3 As shown, one end of the external threaded connector body 1 is connected to the drill pipe, and the other end is a threaded connection section. The external threaded connector body 1 is provided with an external threaded connector main shoulder surface 3, an external threaded connector stress-reducing groove 5, and an external threaded connector secondary shoulder surface 8. External threaded connector tapered pipe threads 6 are sequentially arranged axially between the external threaded connector stress-reducing groove 5 and the transition section 7 between the external threaded connector tapered pipe thread and the external threaded connector secondary shoulder surface. One end of the internal threaded connector body 16 is connected to the drill pipe, and the other end is a threaded connection section. The internal threaded connector body 16 is provided with an internal thread... The internal threaded connector main shoulder surface 9, the internal threaded connector stress-reducing groove 12, and the internal threaded connector auxiliary shoulder surface 14 are sequentially provided with internal threaded main tapered tube internal threads 11 along the axial direction between the internal threaded connector stress-reducing groove 12 and the transition section between the internal threaded connector tapered tube thread and the internal threaded connector main shoulder surface 9; the external threaded connector tapered tube external thread 6 and the internal threaded connector tapered tube internal thread 11 are mated and connected to bear axial loads. During connection, the external threaded connector main shoulder surface 3 contacts the internal threaded connector main shoulder surface 8 to bear torque; in the initial assembly state, see Figure 4 There is a gap between the shoulder surface 8 of the external threaded connector and the shoulder surface 14 of the internal threaded connector.

[0043] Example 1: This embodiment takes the DS40 double-shoulder drill pipe thread as an example. The outer diameter of the drill pipe is Φ139.7mm, the initial secondary shoulder clearance is 0.16mm, the initial external thread main shoulder root fillet radius is 1.6mm, the double-shoulder drill pipe thread adopts a coarse thread with high connection efficiency, the pitch P is 6.5mm, and the taper of the thread adopts a small taper of 1:6, which improves the tensile strength of the threaded joint. The improvements made in this application involve cutting the first thread at the root of the external thread and then setting an external thread joint stress-reducing groove 5 between the main shoulder surface of the external thread and the root of the external thread. After cutting the first thread at the top of the internal thread, an internal thread joint stress-reducing groove 12 is set between the secondary shoulder surface of the internal thread and the top of the internal thread. By setting the stress-reducing groove, the stress of the drill pipe thread during operation is reduced, thereby improving its service life. In the design of this application, the length of the transition section 7 between the tapered pipe thread of the external thread joint and the secondary shoulder surface of the external thread joint is increased, and the initial secondary shoulder gap is reduced by 50%. The purpose of this is to reduce the gap between the secondary shoulders, reduce the contact pressure of the first three threads and the main shoulder surface during the connection of the drill pipe thread, increase the contact pressure of the last three threads and the secondary shoulder surface at the connection, and improve the sealing performance. In the design of this application, the radius of the root of the main shoulder of the external thread is increased by 150%, and the radius of the root of the main shoulder surface of the external thread is optimized to reduce the stress value at the root of the main shoulder surface of the external thread.

[0044] Example 2: This embodiment takes the DS40 double-shoulder drill pipe thread as an example. The outer diameter of the drill pipe is Φ139.7mm, the initial secondary shoulder clearance is 0.16mm, the initial external thread main shoulder root fillet radius is 1.6mm, the double-shoulder drill pipe thread adopts a coarse thread with high connection efficiency, the pitch P is 6.5mm, and the taper of the thread adopts a small taper of 1:6, which improves the tensile strength of the threaded joint. The improvements made in this application involve cutting the first thread at the root of the external thread and then setting an external thread joint stress-reducing groove 5 between the main shoulder surface of the external thread and the root of the external thread. After cutting the first thread at the top of the internal thread, an internal thread joint stress-reducing groove 12 is set between the secondary shoulder surface of the internal thread and the top of the internal thread. By setting the stress-reducing groove, the stress of the drill pipe thread during operation is reduced, thereby improving its service life. In the design of this application, the length of the transition section 7 between the tapered pipe thread of the external thread joint and the secondary shoulder surface of the external thread joint is increased, and the initial secondary shoulder gap is reduced by 75%. The purpose of this application is to reduce the gap between the secondary shoulders, reduce the contact pressure of the first three threads and the main shoulder surface during the connection of the drill pipe thread, increase the contact pressure of the last three threads and the secondary shoulder surface at the connection, and improve the sealing performance. In the design of this application, the radius of the root of the main shoulder of the external thread is increased by 297%, and the radius of the root of the main shoulder surface of the external thread is optimized to reduce the stress value at the root of the main shoulder surface of the external thread.

[0045] In summary, the drill pipe thread structure and processing method with stress-reducing groove disclosed in this application have the following advantages: 1. This application provides stress-reducing grooves on internal and external threaded joints, which can reduce the maximum stress of the drill pipe thread during operation, reduce the stress of the first three threads at the threaded connection, and improve the service life of the drill pipe thread.

[0046] 2. By reducing the clearance of the secondary shoulder, this application can effectively reduce the average contact pressure of the first three threads at the main shoulder surface and threaded connection, and increase the average contact pressure of the last three threads at the secondary shoulder surface and threaded connection, thereby improving the sealing performance.

[0047] 3. This application optimizes the fillet at the root of the main shoulder of the external thread, which can reduce the load on the main shoulder and improve its service life.

[0048] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A drill pipe thread structure with an attached stress-reducing groove, characterized in that, include: An external threaded connector, the external threaded connector includes an external threaded connector body (1), an axially extending external threaded connector tapered pipe thread (6) is provided on the external threaded connector body (1), an external threaded connector stress-reducing groove (5) is provided at the root of the external threaded connector tapered pipe thread (6), an external threaded connector main shoulder is provided at the other end of the external threaded connector stress-reducing groove (5) along the radial outward, and an external threaded connector secondary shoulder is provided at the end of the external threaded connector tapered pipe thread (6) along the radial inward; An internal threaded connector, comprising an internal threaded connector body (16), an axially extending internal threaded body tapered tube internal thread (11) is provided on the internal threaded connector body (16), an internal threaded connector stress-reducing groove (12) is provided at the root of the internal threaded body tapered tube internal thread (11), an internal threaded connector secondary shoulder is provided on the other side of the internal threaded connector stress-reducing groove (12) along the radial outward, an internal threaded connector main shoulder is provided at the end of the internal threaded body tapered tube internal thread (11) along the radial inward, and an internal and external threaded connector cavity (15) is provided inside the internal threaded connector body (16) along the axial direction; the external threaded connector tapered tube thread (6) meshes with the internal threaded body tapered tube internal thread (11).

2. The drill pipe thread structure with stress-reducing groove according to claim 1, characterized in that, The main shoulder of the internal threaded connector is in contact with the main shoulder surface (3) of the external threaded connector; the main shoulder surface (3) of the external threaded connector is connected to the stress-reducing groove (5) of the external threaded connector through the fillet (4) of the external threaded connector, and the other end of the main shoulder of the external threaded connector is connected to the outer edge (2) of the external threaded connector.

3. The drill pipe thread structure with stress-reducing groove according to claim 2, characterized in that, The radius of the fillet (4) of the external thread connector is not greater than the outer diameter of the external thread chamfer.

4. The drill pipe thread structure with stress-reducing groove according to claim 1, characterized in that, A transition section (7) is also provided between the tapered pipe thread (6) of the external threaded connector and the secondary shoulder of the external threaded connector.

5. The drill pipe thread structure with stress-reducing groove according to claim 1, characterized in that, The external threaded connector sub-shoulder and the internal threaded connector sub-shoulder are arranged opposite to each other, and their opposite surfaces are the external threaded connector sub-shoulder surface (8) and the internal threaded connector sub-shoulder surface (14), respectively. There is a gap between the external threaded connector sub-shoulder surface (8) and the internal threaded connector sub-shoulder surface (14).

6. The drill pipe thread structure with stress-reducing groove according to claim 5, characterized in that, The internal threaded connector sub-shoulder surface (14) and the internal threaded connector stress-reducing groove (12) are connected by the internal threaded connector chamfer (13).

7. The drill pipe thread structure with stress-reducing groove according to claim 1, characterized in that, The stress-reducing groove (5) of the external threaded joint has a length of 15~26mm, and the stress-reducing groove (5) of the external threaded joint and the tapered pipe thread (6) of the external threaded joint are rounded.

8. The drill pipe thread structure with stress-reducing groove according to claim 1, characterized in that, The stress-reducing groove (12) of the internal threaded joint has a length of 15~26mm.

9. A drill pipe thread structure with stress-reducing grooves according to claim 1, characterized in that, The taper of both the external threaded connector tapered pipe thread (6) and the internal threaded body tapered pipe internal thread (11) is 1:

6.

10. A method for processing a drill pipe thread structure with stress-reducing grooves as described in any one of claims 1 to 9, characterized in that, include: After the first thread of the external thread tapered pipe thread (6) at the root of the external thread connector body (1) is cut, an external thread connector stress-reducing groove (5) is provided between the external thread main shoulder and the root of the external thread tapered pipe thread (6). After the first thread of the tapered internal thread (11) on the internal thread connector body (16) is cut, an internal thread connector stress-reducing groove (12) is provided between the internal thread connector sub-shoulder and the root of the tapered internal thread (11); and the internal and external thread connector cavity (15) is machined axially inside the internal thread connector body (16).

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