Drill rod thread capable of reducing stress of root fillet on side of main shoulder of external thread and drill rod

Abstract

The utility model provides a drill rod thread and a drill rod capable of reducing stress of a root fillet on the side of a main shoulder of an external thread, which comprise an external thread joint main body and an internal thread joint main body which are respectively connected with the drill rod through a thread connecting section. The size of a root fillet of an external thread connector main circular bead on the external thread connector body is larger than the design size, and the size increasing range is limited by the structural size of the drill rod thread. The maximum stress value of the internal thread and the external thread during working of the drill rod thread is reduced, and the service life of the drill rod thread is prolonged.

Description

Technical Field

[0001] The utility model belongs to the technical field of petroleum drilling, in particular to a drill rod thread and a drill rod capable of reducing the fillet stress at the root of a main shoulder side of an external thread. Background Art

[0002] As exploration continues to deepen, facing increasingly complex and demanding geological conditions, the technological advancement and reliability of drill pipe threads have become critical factors in ensuring operational safety and efficiency. Drill pipe threaded connections, subjected to long-term high stress concentrations, enormous torque, and complex workloads, coupled with the corrosive effects of the geological environment, can easily become vulnerable points in the drill pipe, leading to frequent failures such as breakage and galling, resulting in significant economic losses and safety hazards to drilling operations.

[0003] To address this challenge, existing technologies, such as the double-shouldered stress-relieving threaded components proposed in patent CN201821991784.9 and the double-shouldered design of Grant's XT and HT series products, have achieved some success in optimizing stress distribution and enhancing connection strength, particularly in deep-well operations. However, these technologies unfortunately fail to fundamentally reduce stress levels at the thread root, and the risk of failure persists. Furthermore, the difficulty in ensuring installation precision in actual operations can prevent the double-shouldered effect from being fully realized, thereby compromising sealing performance.

[0004] Patent CN214660001U takes a different approach, enhancing the drill pipe's torque resistance by adjusting the taper of the tapered pipe thread. This solution improves the thread's load-bearing capacity to a certain extent. Unfortunately, it also fails to effectively reduce the stress concentration problem at the connection.

[0005] Patent CN205858205U proposes a trapezoidal thread joint design that aims to achieve uniform force distribution by increasing the contact area and reducing interference between the internal and external threads to improve strength and life. While this innovation effectively enhances connection strength, it also fails to address the core issue of stress reduction. Furthermore, the increased difficulty and cost of trapezoidal thread processing, as well as the potential challenges in sealing performance, have limited its widespread application.

[0006] In summary, although current technology has made certain progress in improving the performance of drill pipe threads, how to more effectively reduce stress concentration at threaded connections while ensuring good sealing performance and processing economy remains a key technical problem that needs to be solved urgently. Utility Model Content

[0007] In order to solve the problems existing in the prior art, the utility model provides a drill pipe thread and a drill pipe that reduce the stress of the root fillet on the main shoulder side of the external thread, which can reduce the stress value of the root fillet on the main shoulder side of the external thread, reduce the maximum stress value of the internal and external threads of the drill pipe thread itself during operation, and increase the service life of the drill pipe thread.

[0008] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a drill pipe thread that reduces the stress of the root fillet on the main shoulder side of the external thread, comprising an external thread joint body and an internal thread joint body, the external thread joint body and the internal thread joint body being connected to the drill pipe through threaded connection sections respectively, the size of the root fillet of the main shoulder of the external thread joint on the external thread joint body being greater than 1.6 mm, and the range of the size increase is limited by the structural size of the drill pipe thread itself.

[0009] Furthermore, the external threaded joint body is provided with an external threaded joint main shoulder surface, and the internal threaded joint body is provided with an internal threaded joint main shoulder surface. When the external threaded joint body and the internal threaded joint body are connected, the external threaded joint main shoulder surface is in close contact with the internal threaded joint main shoulder surface.

[0010] Furthermore, the size of the fillet at the root of the main shoulder of the external threaded joint on the main body of the external threaded joint is greater than 1.6 mm and less than or equal to the chamfered outer diameter of the main shoulder surface of the external threaded joint.

[0011] Furthermore, a tapered tube external thread is provided on the threaded connection section of the external threaded joint body, and a tapered tube internal thread is provided on the threaded connection section of the internal threaded joint body. The connection between the tapered tube external thread and the tapered tube internal thread can realize the connection between the external threaded joint body and the internal threaded joint body.

[0012] Furthermore, an external threaded joint auxiliary shoulder surface is provided on the external threaded joint body, and an internal threaded joint auxiliary shoulder surface is provided on the internal threaded joint body. The lengths of the external threaded joint auxiliary shoulder surface and the internal threaded joint auxiliary shoulder surface increase between 11mm and 11.16mm.

[0013] Furthermore, a first transition section is provided between the external threaded joint auxiliary shoulder surface and the tapered tube external thread on the external threaded joint body.

[0014] Furthermore, the tapered tube external thread is arranged along the axial direction between the fillet of the root of the main shoulder of the external threaded joint and the first transition section.

[0015] Furthermore, a second transition section is provided between the tapered internal thread of the internal thread joint body and the auxiliary shoulder surface of the internal thread joint.

[0016] Furthermore, the internal thread of the tapered tube is arranged between the main shoulder surface of the internal thread joint and the second transition section along the axial direction.

[0017] The utility model also provides a drill rod, on which the drill rod thread for reducing the fillet stress at the root of the main shoulder side of the external thread is arranged.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects:

[0019] The utility model provides a drill pipe thread which reduces the stress of the fillet at the root of the main shoulder side of the external thread. By increasing the size of the fillet at the root of the main shoulder of the external thread joint, the stress in this area is effectively dispersed, the stress concentration phenomenon is reduced, thereby extending the service life of the drill pipe thread and further improving the durability of the drill pipe.

[0020] By increasing the length of the auxiliary shoulder, the stress distribution of the drill pipe thread is optimized, making the stress more evenly distributed in various areas and reducing the risk of damage caused by uneven stress distribution.

[0021] The internal and external threaded joint bodies are connected by precisely matched tapered pipe threads, which ensures the tightness and stability of the connection between the two, reduces the stress fluctuation caused by the gap, and improves the overall performance of the drill pipe thread. As a result, the drill pipe can be used for a long time under more severe working conditions, reducing the frequency and cost of replacing the drill pipe.

[0022] The utility model designs the size of the fillet at the root of the main shoulder of the external threaded joint on the main body of the external threaded joint to be larger than the design size by 1.6mm, but less than or equal to the chamfered outer diameter of the main shoulder surface of the external threaded joint. This design aims to disperse stress and reduce stress concentration by increasing the fillet size, thereby reducing the stress value in this area. The external threaded joint body and the internal threaded joint body are respectively provided with an external threaded joint auxiliary shoulder surface and an internal threaded joint auxiliary shoulder surface, and the length of the auxiliary shoulder is appropriately increased to reduce the gap. At the same time, a first transition section and a second transition section are respectively provided between the auxiliary shoulder surface of the external threaded joint and the external thread of the tapered tube, and between the internal thread of the tapered tube and the auxiliary shoulder surface of the internal threaded joint, so as to achieve a smooth transition and reduce stress mutations.

[0023] In summary, the structure and improvement of the drill pipe thread for reducing the root fillet stress on the main shoulder side of the external thread not only improves the service life and stability of the drill pipe thread, but also optimizes the stress distribution, reduces the risk of damage, and provides more reliable protection for drilling operations in complex environments such as deep wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the overall structure of the drill rod thread of the utility model.

[0025] Markings in the figure: 1. External thread connector body; 2. External thread connector outer edge; 3. External thread connector main shoulder surface; 4. Root fillet of external thread connector main shoulder; 5. External thread of tapered tube; 6. First transition section; 7. External thread connector auxiliary shoulder surface; 8. Internal thread connector main shoulder surface; 9. External edge of internal thread connector; 10. Internal thread of tapered tube; 11. Second transition section; 12. Internal thread connector auxiliary shoulder surface; 13. Internal thread connector body; 14. Male and female thread connector lumens. DETAILED DESCRIPTION

[0026] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be regarded as illustrative in nature and not restrictive.

[0027] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and 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, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation to the present invention.

[0028] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of this utility model, "plurality" means two or more, unless otherwise specifically defined.

[0029] In this utility model, unless otherwise expressly specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. For those skilled in the art, the specific meanings of the above terms in this utility model can be understood according to specific circumstances.

[0030] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0032] like Figure 1 As shown, the utility model provides a drill pipe thread that reduces the stress of the root fillet on the side of the main shoulder of the external thread. The core of the utility model is to significantly reduce the stress value in this area by optimizing the size of the root fillet on the side of the main shoulder of the external thread and adjusting the length of the auxiliary shoulder, thereby improving the overall durability and service life of the drill pipe thread. Specifically, it includes: an external thread joint body 1, an external thread joint outer edge 2, an external thread joint main shoulder surface 3, an external thread joint main shoulder root fillet 4, a tapered pipe external thread 5, a first transition section 6, an external thread joint auxiliary shoulder surface 7, an internal thread joint main shoulder surface 8, an internal thread joint outer edge 9, a tapered pipe internal thread 10, a second transition section 11, an internal thread joint auxiliary shoulder surface 12, an internal thread joint body 13, and a male and female thread joint lumen 14;

[0033] Specifically: one end of the external threaded joint body 1 is connected to the drill pipe, and the other end is a threaded connection section. The external threaded joint main shoulder surface 3 and the external threaded joint secondary shoulder surface 7 are provided on the external threaded joint body 1. A tapered tube external thread 5 is provided along the axial direction between the fillet 4 at the root of the main shoulder of the external threaded joint and the first transition section 6; the first transition section 6 is provided between the external threaded joint secondary shoulder surface 7 and the tapered tube external thread 5.

[0034] Preferably, the size of the fillet 4 at the root of the main shoulder of the external threaded joint of the present invention is increased, and the range of the size increase of the fillet 4 at the root of the main shoulder of the external threaded joint is limited by the structural size of the drill pipe thread itself.

[0035] Specifically, the size of the fillet 4 at the root of the main shoulder of the external threaded joint of the present invention is larger than the design size of 1.6 mm and less than or equal to the chamfered outer diameter of the main shoulder surface 3 of the external threaded joint. Increasing the size of the fillet 4 at the root of the main shoulder of the external threaded joint can disperse stress concentration and reduce the stress value in this area. The range of increase in the fillet size needs to be reasonably limited according to the structural dimensions of the drill pipe thread itself to ensure that the stress can be effectively reduced without affecting the overall strength and connection stability of the thread.

[0036] One end of the internal threaded joint body 13 is connected to the drill pipe, and the other end is a threaded connection section. The internal threaded joint body 13 is provided with an internal threaded joint main shoulder surface 8 and an internal threaded joint auxiliary shoulder surface 12. The tapered pipe internal thread 10 is sequentially arranged along the axial direction between the internal threaded joint main shoulder surface 8 and the second transition section 11; the second transition section 11 is arranged between the tapered pipe internal thread 10 and the internal threaded joint auxiliary shoulder surface 12;

[0037] Preferably, the external thread 5 of the tapered tube is matched with the internal thread 10 of the tapered tube to bear axial loads, and the external thread 5 of the tapered tube is precisely matched with the internal thread 10 to ensure that it can bear axial loads; when connected, the main shoulder surface 3 of the external threaded joint is in close contact with the main shoulder surface 8 of the internal threaded joint to bear torque and ensure the stability and reliability of the connection.

[0038] Furthermore, in the initial assembly state, there is a gap between the auxiliary shoulder surface 7 of the external threaded joint and the auxiliary shoulder surface 12 of the internal threaded joint. The initial gap is 0.16 mm. In order to reduce the equivalent stress when the internal and external threads are working, the length of the auxiliary shoulder surface 7 of the external threaded joint and the auxiliary shoulder surface 12 of the internal threaded joint is increased to between 11 mm and 11.16 mm, thereby reducing the initial gap between the auxiliary shoulders.

[0039] Furthermore, the increase in the length of the secondary shoulder needs to be controlled within a certain range to avoid affecting the fitting connection and load-bearing capacity of the tapered tube external thread and the tapered tube internal thread. Preferably, the length increase range of the secondary shoulder surface cannot exceed the length difference between the tapered sections of the tapered tube external thread 5 and the tapered tube internal thread 10.

[0040] Preferably, high-strength, corrosion-resistant alloy steel material is selected as the base material of the drill rod thread, and precision processing technology and heat treatment technology are adopted to ensure that the accuracy and strength of the thread meet the design requirements.

[0041] Example

[0042] Take the DS40 drill pipe, for example. It features a double-shouldered drill pipe thread with an outer diameter of Φ139.7mm, designed specifically for extreme operating environments such as deep wells and high pressure. Its initial secondary shoulder clearance is set at 0.16mm, ensuring a balance between connection flexibility and stability. The initial primary shoulder root fillet radius is 0.8mm, a design that meets basic strength and stress distribution requirements under conventional conditions. This double-shouldered drill pipe thread utilizes a coarse thread for high connection efficiency, with a pitch of 6.5mm and a small 1:6 taper, enhancing the tensile strength of the threaded joint.

[0043] However, with the continuous advancement of drilling technology and the increasing demand for drill pipe performance, the optimized design of the DS40 drill pipe thread has become particularly important. This optimization focuses on adjusting the fillet size at the root of the external thread main shoulder, aiming to further reduce stress in this area, thereby improving the overall durability and service life of the drill pipe.

[0044] First, we increased the fillet size at the root of the external thread main shoulder of the DS40 drill pipe by two different amounts: 100% (increased to 1.6mm) and 144% (increased to 2.3mm). This adjustment aims to more effectively disperse stress and reduce stress concentration by increasing the fillet radius.

[0045] To verify the effectiveness of the optimization solution, we used finite element analysis software to conduct a detailed stress analysis of the adjusted drill pipe threads. The results showed that when the root fillet size was increased to 1.6 mm, the stress at the root of the main shoulder surface 3 of the external threaded joint was significantly reduced. When the size was further increased to 2.3 mm, the stress reduction was even more significant. Specifically, the stress dropped from the original 635 MPa to 476 MPa, a decrease of approximately 25.04%. This result fully demonstrates the effectiveness of increasing the root fillet size in reducing stress.

[0046] By optimizing the size of the root fillet 4 on the main shoulder side of the external thread and adjusting the length of the secondary shoulder, the drill pipe thread of this utility model effectively reduces stress in this area, thereby improving the durability of the drill pipe thread. By reducing the equivalent stress of the internal and external threads during operation, the service life of the drill pipe thread is extended, reducing replacement frequency and maintenance costs. The precise connection between the external and internal threads of the tapered pipe and the close contact between the main shoulder surface improves the stability and reliability of the connection. This utility model is suitable for drill pipe connection needs in complex environments such as deep wells, providing strong technical support for drilling operations.

[0047] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended that all changes that fall within the meaning and range of equivalents of the claims are included in the present invention. Any reference signs in the claims should not be construed as limiting the claim to which they relate.

[0048] In addition, it should be understood that although this specification describes the embodiments, not every embodiment contains only one independent technical solution. This description is for clarity only. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for the purpose of illustrating the technical concept of the present utility model and cannot be used to limit the scope of protection of the present utility model. Any changes made based on the technical solution in accordance with the technical concept proposed by the present utility model shall fall within the scope of protection of the claims of the present utility model.

Claims

1. A drill pipe thread for reducing the fillet stress at the root of the main shoulder side of the external thread, characterized in that: The invention comprises an external threaded joint body (1) and an internal threaded joint body (13), wherein the external threaded joint body (1) and the internal threaded joint body (13) are respectively connected to the drill pipe via a threaded connection section, and the size of the external threaded joint main shoulder root fillet (4) on the external threaded joint body (1) is greater than 1.6 mm.

2. A drill pipe thread for reducing the fillet stress at the root of the main shoulder side of the external thread according to claim 1, characterized in that: The external threaded joint body (1) is provided with an external threaded joint main shoulder surface (3), and the internal threaded joint body (13) is provided with an internal threaded joint main shoulder surface (8). When the external threaded joint body (1) and the internal threaded joint body (13) are connected, the external threaded joint main shoulder surface (3) and the internal threaded joint main shoulder surface (8) are in close contact.

3. A drill pipe thread for reducing the fillet stress at the root of the main shoulder side of the external thread according to claim 2, characterized in that: The size of the fillet (4) at the root of the external threaded joint main shoulder on the external threaded joint body (1) is greater than 1.6 mm and less than or equal to the chamfered outer diameter of the external threaded joint main shoulder surface (3).

4. A drill pipe thread for reducing the fillet stress at the root of the main shoulder side of the external thread according to claim 1, characterized in that: The threaded connection section of the external threaded joint body (1) is provided with a tapered tube external thread (5), and the threaded connection section of the internal threaded joint body (13) is provided with a tapered tube internal thread (10). The tapered tube external thread (5) and the tapered tube internal thread (10) are connected to realize the connection between the external threaded joint body (1) and the internal threaded joint body (13).

5. A drill pipe thread for reducing the fillet stress at the root of the main shoulder side of the external thread according to claim 4, characterized in that: The external threaded joint body (1) is provided with an external threaded joint auxiliary shoulder surface (7), and the internal threaded joint body (13) is provided with an internal threaded joint auxiliary shoulder surface (12). The length of the external threaded joint auxiliary shoulder surface (7) and the internal threaded joint auxiliary shoulder surface (12) is between 11 mm and 11.16 mm.

6. A drill pipe thread for reducing the fillet stress at the root of the main shoulder side of the external thread according to claim 5, characterized in that: A first transition section (6) is provided between the external threaded joint auxiliary shoulder surface (7) on the external threaded joint body (1) and the tapered tube external thread (5).

7. A drill pipe thread for reducing the fillet stress at the root of the main shoulder side of the external thread according to claim 6, characterized in that: The tapered tube external thread (5) is arranged along the axial direction between the fillet (4) at the root of the main shoulder of the external threaded joint and the first transition section (6).

8. A drill pipe thread for reducing the fillet stress at the root of the main shoulder side of the external thread according to claim 5, characterized in that: A second transition section (11) is provided between the tapered internal thread (10) on the internal thread joint body (13) and the internal thread joint auxiliary shoulder surface (12).

9. A drill pipe thread for reducing the fillet stress at the root of the main shoulder side of the external thread according to claim 8, characterized in that: The tapered tube internal thread (10) is arranged along the axial direction between the main shoulder surface (8) of the internal thread joint and the second transition section (11).

10. A drill pipe, characterized in that: The drill rod is provided with a drill rod thread for reducing the fillet stress at the root of the main shoulder side of the external thread according to any one of claims 1 to 9.

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