Torsion-resistant drill pipe connection (embodiments) and method of connecting drill pipe

Abstract

FIELD: drilling equipment.SUBSTANCE: group of inventions relates to threaded drilling connections between pipes used in drilling vertical, directional and horizontal oil and gas wells. A torsion-resistant drill pipe connection comprises a pin and a box installed at both ends of the pipe and arranged coaxially. The outer surface of the pin and the inner surface of the box form, respectively, a first conical connecting surface and a second conical connecting surface with the same angle of inclination. On the first and second conical surfaces, external and internal threads are made, respectively. The external thread is intended for threaded connection with the corresponding second conical surface of the internal part of the first drill pipe. The internal thread is intended for threaded connection with the corresponding first conical surface of the outer part of the second drill pipe. The connection of the pin and the box forms a certain type of connection. Each connection type is characterized by the parameters of the external and internal threads and has a specified range of the number of tightening turns of 5-13 turns and a specified torque resistance limit of at least 10,000 ft-lbs. The number of tightening turns and the thread parameters satisfy the given mathematical expression. A variant of a torsion-resistant connection of drill pipes and a method for connecting drill pipes are declared.EFFECT: reduction in non-production time, an increase in the efficiency of the drilling platform while simultaneously ensuring high torsional stability of the connection.23 cl, 7 dwg, 3 tbl

Description

[0001] Technical field

[0002] The present invention relates to the field of drilling equipment, in particular to threaded drilling connections of pipes to each other, used in drilling vertical, directional and horizontal oil and gas wells.

[0003] Technology Level

[0004] In the exploration and production of natural resources such as oil and natural gas, drill pipe is a key component of the drilling rig, performing a number of important functions: transmitting torque, transporting drilling fluid, and supporting the weight of the drilling tool. The reliability of the drill joint directly impacts the safety, efficiency, and economics of the entire drilling process.

[0005] Traditional drill pipe connection designs, primarily based on simple conical threaded surfaces, exhibit clear shortcomings when operating in challenging conditions. On the one hand, earlier designs often used a simple conical threaded connection, which exhibits significant stress concentration under high loads.

[0006] As drilling into deeper and more complex geological structures has progressed, the demands on the stability of pipe connections have increased. Challenging conditions, such as high-resistance hard rock or irregular stresses caused by formation creep, place severe strain on connections. Modern standard connections often fail to meet these increasing demands, and many fail before reaching the intended drilling depth, leading not only to equipment wear but also to significant time and costly replacements.

[0007] Furthermore, the process of tightening threaded connections accounts for a significant portion of non-production time during tripping operations on a drilling platform. Therefore, studying the relationship between threaded design parameters and tightening speed is crucial for improving overall drilling rig productivity and reducing non-production downtime.

[0008] An insufficient number of tightening turns in a connection can result in incomplete engagement between the connecting elements, which can lead to loosening of the connection and its spontaneous unscrewing under the influence of torque, resulting in an emergency. At the same time, an excessive number of tightening turns increases the duration of screwing operations, thereby increasing non-production time and reducing the overall efficiency of drilling operations.

[0009] Furthermore, during prolonged rotation and vibration exposure of the drill string, even minor design defects or performance deficiencies in connections will eventually worsen and become critical. The lack of a standardized and consistent range for the number of tightening turns and torque resistance limits of tool joints leads to accelerated wear of the connecting assemblies, loss of seal, and other operational issues.

[0010] As a result, drilling fluid may leak out, which disrupts the functioning of the circulation system and poses a threat to the stability and safety of underground drilling operations.

[0011] Disclosure of the essence of the invention

[0012] The object of the present invention is to provide a reliable, torsion-resistant drill pipe connection and a design method thereof by studying the relationship between various parameters of the threaded structure and the tightening speed, so as to reduce non-production time, improve the operating efficiency of the drilling rig, while ensuring high torsion resistance of the connection.

[0013] The technical result of this invention is to reduce non-production time, increase the efficiency of the drilling platform, while simultaneously ensuring high torsional stability of the connection.

[0014] The technical result achieved is that the torsion-resistant connection of drill pipes comprises a nipple and a coupling mounted on both ends of the pipe and located coaxially, wherein the outer surface of the nipple and the inner surface of the coupling form, respectively, a first conical connecting surface and a second conical connecting surface with the same angle of inclination, wherein on the first and second conical surfaces, respectively, an external and internal thread is made, wherein the external thread is intended for a threaded connection with the corresponding second conical surface of the inner part of the first drill pipe, and the internal thread is intended for a threaded connection with the corresponding first conical surface of the outer part of the second drill pipe, wherein the connection of the nipple and the coupling form a certain type of connection,and each type of connection is characterized by the parameters of the threads of the external and internal parts and has a specified range of the number of tightening turns of 5-13 turns and a specified torque resistance limit of at least 10,000 ft-lbs, while the number of tightening turns and the thread parameters satisfy the following relationship:,

[0015]

[0016] where N is the number of tightening turns; - half the thread profile angle; tpr - thread taper; P - thread pitch; R - arc radius at the base of the thread.

[0017] It is preferable that the thread parameter of the nipple and coupling be the root radius of the thread, the size of which for any type of connection is 0.038-0.08 inches.

[0018] It is advisable that the parameter of the nipple and coupling thread be half the angle of the thread profile, the size of which for any type of connection is 27.5°-44.5°.

[0019] It is desirable that the parameter of the nipple and coupling thread be the thread taper, which for any type of connection is in the range from 1 / 16 to 1 / 6.

[0020] It is preferable that the design type of connection between the thread taper and the arc radius at the root of the thread be established in the following relationship: when the taper is 1 / 16, the arc radius is 0.05-0.065 inches; when the taper is 1 / 12, the arc radius is 0.04-0.06 inches; when the taper is 1 / 10, the arc radius is 0.045-0.055 inches.

[0021] It is advisable that the thread parameter be the thread pitch, the size of which for any type of connection is 0.250-0.364 inches.

[0022] It is desirable that the derivative of the number of tightening turns to the taper of the thread satisfies the following relationship:

[0023]

[0024] where N is the number of tightening turns; - half the thread profile angle; tpr - thread taper; P - thread pitch; R - arc radius at the base of the thread.

[0025] It is preferable that the derivative of the number of tightening turns to the arc radius satisfies the following relationship:

[0026]

[0027] where N is the number of tightening turns; - half the thread profile angle; tpr - thread taper; P - thread pitch; R - arc radius at the base of the thread.

[0028] It is advisable that the derivative of the number of tightening turns to the thread pitch satisfies the following relationship:

[0029]

[0030] where N is the number of tightening turns; - half the thread profile angle; tpr - thread taper; P - thread pitch; R - arc radius at the base of the thread.

[0031] It is desirable that the arc radius, thread pitch, thread half angle and thread taper satisfy the following relationship:

[0032]

[0033] where θ is half the thread profile angle; tpr is the thread taper; P is the thread pitch; Rmax is the maximum value of the arc radius at the root of the thread.

[0034] Also, the technical result is achieved due to the fact that the connection of drill pipes, resistant to torsion, contains a nipple and a coupling installed on both ends of the pipe and located coaxially, wherein the outer surface of the nipple and the inner surface of the coupling form, respectively, a first conical connecting surface and a second conical connecting surface with the same angle of inclination, wherein on the first and second conical surfaces, respectively, an external and internal thread is made, wherein the external thread is made with the possibility of a threaded connection with the corresponding second conical surface of the inner part of the first drill pipe, and the internal thread is made with the possibility of a threaded connection with the corresponding first conical surface of the outer part of the second drill pipe, wherein the connection of the nipple and the coupling form a certain type of connection,and each type of connection is characterized by a given range of the number of tightening turns, as well as the parameters of the nipple and coupling thread: the radius of the arc at the base of the thread, half the angle of the thread profile, the taper of the thread and the thread pitch, while the number of tightening turns and the specified thread parameters satisfy the following relationship:,

[0035]

[0036] where N is the number of tightening turns; - half the thread profile angle; tpr - thread taper; P - thread pitch; R - arc radius at the base of the thread.

[0037] It is preferable that the derivative of the number of tightening turns to the taper satisfies the following relationship:

[0038]

[0039] where N is the number of tightening turns; - half the thread profile angle; tpr - thread taper; P - thread pitch; R - arc radius at the base of the thread.

[0040] It is advisable that the derivative of the number of tightening turns to the arc radius satisfy the following relationship:

[0041]

[0042] where N is the number of tightening turns; - half the thread profile angle; tpr - thread taper; P - thread pitch; R - arc radius at the base of the thread.

[0043] It is desirable that the derivative of the number of tightening turns to the thread pitch satisfies the following relationship:

[0044]

[0045] where N is the number of tightening turns; - half the thread profile angle; tpr - thread taper; P - thread pitch; R - arc radius at the base of the thread.

[0046] It is preferable that the arc radius, thread pitch, thread taper and thread half angle satisfy the following relationship:

[0047]

[0048] where θ is half the thread profile angle; tpr is the thread taper; P is the thread pitch; Rmax is the maximum value of the arc radius at the root of the thread.

[0049] It is advisable that each type of connection has a specified tightening range of 5-13 turns, and the specified torque resistance limit is 10,000 ft-lbs.

[0050] It is desirable that for any type of connection, the arc radius at the root of the thread should be in the range of 0.038-0.08 inches.

[0051] It is preferable that the half angle of the thread profile be in the range of 27.5°-44.5° for any type of connection.

[0052] It is advisable that for any type of connection, the thread taper should be in the range of 1 / 16 to 1 / 6.

[0053] It is desirable that the design type of connection between the thread taper and the arc radius be as follows: with a thread taper of 1 / 16, the arc radius is in the range of 0.05-0.065 inches, with a thread taper of 1 / 12, the arc radius is in the range of 0.04-0.06 inches, with a taper of 1 / 10, the arc radius is in the range of 0.045-0.055 inches.

[0054] It is preferable that the thread pitch be in the range of 0.25-0.364 inch for any type of connection.

[0055] The technical result achieved is that the method for designing a torsion-resistant drill pipe connection includes determining the range of the number of tightening turns and the torque resistance limit for the design type of connection based on standard and special types of connections, wherein the range of the number of tightening turns for the design type is 5-13 turns, and the minimum torque resistance limit is not less than 10,000 foot-pounds, also includes establishing the thread parameters of the design type of connection, taking into account the arc radius at the root of the thread, the taper of the thread, the half angle of the thread profile and the thread pitch, wherein the selection of the values ​​of the arc radius and the thread pitch is made on the basis of the established range of the number of tightening turns and the torque resistance limit,the selection of the thread taper range is made on the basis of the established range of the number of turns and the torque resistance limit, and the determination of the range of the arc radius at the base of the thread is made on the basis of the selected range of thread taper, based on the relationship between the thread parameters and the number of tightening turns.

[0056] It is advisable that in the design method, the number of tightening turns, the arc radius at the root of the thread, the half angle of the thread profile and the thread pitch satisfy the following relationship:

[0057]

[0058] where N is the number of tightening turns; - half the thread profile angle; tpr - thread taper; P - thread pitch; R - arc radius at the base of the thread.

[0059] In the design method, it is preferable that the taper of the thread and the arc radius at the root of the thread satisfy the following relationships: when the taper is 1 / 16, the arc radius is in the range of 0.05-0.065 inches; when the taper is 1 / 12, the arc radius is in the range of 0.04-0.06 inches; when the taper is 1 / 10, the arc radius is in the range of 0.045-0.055 inches.

[0060] The unique design of the conical coaxial connecting surfaces, combined with a precisely specified tightening range (5-13 turns) and torque resistance limit (at least 10,000 ft-lbs), optimizes the connection structure and mechanical performance. This ensures efficient, stable, and safe torque transmission in complex and adverse drilling conditions, reduces failure rates, and improves overall drilling efficiency.

[0061] Brief description of drawings

[0062] To further illustrate the invention, a brief description of the drawings used in various embodiments is provided below. These drawings illustrate only a few embodiments of the invention and do not limit its scope. Those skilled in the art can develop similar drawings based on these without departing from the scope of the invention.

[0063] Fig. 1 - longitudinal section of a nipple of a threaded connection of a drill pipe with increased resistance to torsion according to an embodiment of the invention.

[0064] Fig. 2 - longitudinal section of the coupling of the threaded connection of the drill pipe.

[0065] Where 3 is the center line of the nipple, 4 is the center line of the coupling, - half the angle of the thread profile of the nipple and coupling, - angle of the thread profile of the nipple and coupling.

[0066] Fig. 3 - graph of the dependence of the number of tightening turns on the half angle of the thread profile.

[0067] Fig. 4 - graph of the dependence of the number of tightening turns on the thread taper.

[0068] Fig. 5 - graph of the dependence of the number of tightening turns on the radius of the arc at the base of the thread.

[0069] Fig. 6 - graph of the dependence of the number of tightening turns on the thread pitch.

[0070] Fig. 7 - graph of the dependence of the number of tightening turns on the taper and radius of the arc at the base of the thread.

[0071] Implementation of the invention

[0072] To clearly understand the objective, technical results, and advantageous embodiments of the invention, the following is a detailed description of the technical solutions with reference to the accompanying drawings. It is obvious that the described embodiments represent only a portion, and not all, of the possible embodiments of the present invention. The components of the embodiments shown in the drawings may be arranged and implemented in various configurations.

[0073] Therefore, the description of the embodiments of the present invention shown in the drawings does not limit the scope of the invention, but merely illustrates selected embodiments. All other embodiments obtained by those skilled in the art based on the presented examples without creative effort fall within the scope of protection of the present invention.

[0074] It should be noted that the same reference designations and letter symbols in the drawings represent similar elements. Therefore, if an element is defined in one drawing, it does not need to be redefined and explained in subsequent drawings.

[0075] An advantageous embodiment of a threaded joint for a drill pipe with increased torsional resistance according to the present invention includes a pin 1 and a coupling 2, respectively installed at both ends of a drill pipe, wherein the pin 1 and the coupling 2 are located coaxially. The outer surface of the pin 1 and the inner surface of the coupling 2 form a first conical connecting surface and a second conical connecting surface, respectively, wherein the inclination angle of the first and second conical connecting surfaces is the same. On the first and second conical connecting surfaces, respectively, an external and an internal thread are formed, wherein the external thread is intended for a threaded connection with the corresponding second conical connecting surface of the coupling 2 of the first drill pipe, and the internal thread is intended for a threaded connection with the corresponding first conical connecting surface of the pin 1 of the second drill pipe.Nipple 1 and the corresponding coupling 2, as well as coupling 2 and the corresponding nipple 1, belong to a certain type of connection, wherein each type of connection has a specified range of the number of tightening turns N, which is from 5 to 13 turns, and a specified torque resistance limit, which is not less than 10,000 foot-pounds (Fig. 1-2).

[0076] The number of tightening turns (N) determines the tightening speed of the mating drill pipes. Generally, a higher number of tightening turns (N) results in a lower tightening speed. Conversely, a lower number of tightening turns (N) results in a higher tightening speed. The tightening speed directly affects the proportion of non-productive time during tripping operations on a drilling rig. A higher tightening speed reduces non-productive time, which equates to an increase in the actual working time of the drill string and an improvement in the overall efficiency of drilling operations. However, an increased tightening speed achieved by reducing the number of tightening turns (N) may result in insufficiently tight coupling between pin 1 and coupling 2, which negatively impacts the stability of the entire connection.

[0077] Furthermore, the torsional resistance of a drill pipe threaded connection determines the maximum stress that the connection between nipple 1 and coupling 2 can withstand when subjected to torque, which directly affects the stability and durability of the connection under load. The higher the torque resistance, the better the material's resistance to torsional deformation, resulting in a stronger and more durable connection between nipple 1 and coupling 2. At the same time, the higher the torque resistance, the higher the drilling speed, as the drilling tool can withstand greater torque. This allows for faster penetration of formations, increased drilling speed and efficiency, and reduced risk of drill pipe sticking, improving work efficiency.The design of coaxial conical connecting surfaces, combined with a precisely specified number of tightening turns (N) (5-13 turns) and a specified torque resistance limit of at least 10,000 ft-lbs, optimizes the connection structure and its mechanical characteristics. This ensures efficient, stable, and safe torque transmission in challenging and unfavorable drilling conditions, reduces failure rates, and improves overall drilling efficiency.

[0078] In some embodiments, each connection type is defined by the thread parameters of the pin 1 and the corresponding coupling 2. The thread parameters of the pin 1 and coupling 2 include the arc radius at the root of the thread R, wherein for any connection type, the arc radius R of both the pin 1 and coupling 2 is in the same range from 0.038 to 0.08 inches. This ensures a more uniform distribution of contact stresses along the axis and circumference of the thread. This design is capable of withstanding complex variable loads arising from both the marine environment and the drilling process, effectively reduces stress concentration at the root of the thread, reduces the formation and propagation of fatigue failures, ensuring the long-term reliability of the drill pipe connection under severe operating conditions.

[0079] In some embodiments, the thread parameters of the pin 1 and the coupling 2 further include a half thread profile angle , while for any type of connection, half the angle of the thread profile both nipple 1 and coupling 2 are in the same range from 27.5° to 44.5°. This range of half profile angle Ensures uniform load distribution between threads under internal pressure, preventing stress concentration and damage to individual threads. This significantly improves the overall reliability of the connection and its tightness, effectively preventing leaks of the transported medium and guaranteeing safe, stable operation of the system.

[0080] In some embodiments, the thread parameters of the nipple 1 and coupling 2 additionally include a thread taper tpr, wherein for any connection type, the thread taper tpr of both the nipple 1 and coupling 2 is in the same range from 1 / 16 to 1 / 6. This thread taper range ensures a tight fit between the nipple 1 and coupling 2 during tightening, particularly by forming a reliable sealing contact in the area of ​​the sealing surfaces. As tightening progresses, the contact pressure between the threaded threads and the sealing surfaces increases uniformly, which maximizes the speed and efficiency of mating the nipple 1 with the coupling 2.

[0081] In some embodiments, when the connection type is a design type, the following relationship exists between the thread taper tpr and the arc radius at the root of the thread R: with a thread taper of 1 / 16, the arc radius at the root of the thread is 0.05-0.065 inches, with a taper of 1 / 12, the arc radius is 0.04-0.060 inches, and with a taper of 1 / 10, the arc radius is 0.045-0.055 inches. This relationship ensures a more uniform and rational stress distribution in the threaded connection, effectively reduces stress concentration, enhances the load-bearing capacity of the connection and its fatigue strength, which can withstand various complex loads.

[0082] In some embodiments, the thread parameters of pin 1 and coupling 2 additionally include a thread pitch P, wherein for any connection type, the thread pitch P of both pin 1 and coupling 2 is within the same range of 0.250 to 0.364 inches. This range ensures a more uniform load distribution when significant tensile forces are applied to the connection. Compared to a thread pitch P that is too dense or too sparse, this range allows each thread to effectively support the load, reducing stress concentration pressure and preventing thread deformation or damage due to localized overloads.

[0083]

[0084] Where N is the number of tightening turns; θ is half the thread profile angle; tpr is the thread taper; P is the thread pitch; R is the radius of the arc at the root of the thread.

[0085] By selecting thread parameters, the number of tightening turns N can be accurately calculated, optimizing the mechanical performance of the threaded connection. For example, when the thread profile half angle θ, thread taper tpr, thread pitch P, and thread root radius R are determined according to the design, using this ratio to determine the number of tightening turns N ensures uniform stress distribution when transmitting significant torques and axial forces, preventing local stress concentration and fatigue failure, significantly improving the durability and reliability of the pipe connection.

[0086] In some embodiments, the derivative of the number of tightening turns N to the thread taper tpr satisfies the following relationship:

[0087]

[0088] where N is the number of tightening turns; θ is half the thread profile angle; tpr is the thread taper; P is the thread pitch; R is the radius of the arc at the root of the thread.

[0089] Figure 4 shows the relationship between the number of tightening turns N and the thread taper tpr for a threaded connection of drill pipes with increased torsional resistance according to the present invention. In this graph, the abscissa axis represents the thread taper tpr, and the ordinate axis represents the number of tightening turns N. As can be seen from the graph, with the other thread parameters fixed, there is a negative correlation between the number of tightening turns N and the thread taper tpr, which makes it possible to accurately control the change in the number of tightening turns N by finely adjusting the thread taper tpr, thereby determining the change trend of the relationship between the number of tightening turns N and the thread taper tpr and providing a theoretical basis for designing the threads of the pin 1 and the coupling 2.

[0090] In some embodiments, with a taper of 1 / 10, the corresponding number of tightening turns is 7.01 turns. Compared with a taper of 1 / 16, where the corresponding number of tightening turns is 11.8 turns, this can significantly reduce the number of tightening turns and reduce non-production time, thereby improving work efficiency. Compared with a taper of 1 / 6, where the corresponding number of tightening turns is 4.2 turns, a tighter connection of the nipple 1 and the coupling 2 is ensured, which improves the sealing of the pipe connection (Fig. 4).

[0091] In some embodiments, the derivative of the number of tightening turns N to the radius of the arc at the root of the thread R satisfies the following relationship:

[0092]

[0093] Where N is the number of tightening turns; θ is half the thread profile angle; tpr is the thread taper; P is the thread pitch; R is the radius of the arc at the root of the thread.

[0094] Figure 5 shows the relationship between the number of tightening turns N and the arc radius at the root of the thread R for a drill pipe threaded joint with increased torsional resistance according to the invention. In this graph, the abscissa axis represents the arc radius at the root of the thread R, and the ordinate axis represents the number of tightening turns N. As can be seen from the graph, with the other thread parameters fixed, there is a negative correlation between the number of tightening turns N and the arc radius at the root of the thread R, which makes it possible to accurately control the change in the number of tightening turns N by finely adjusting the arc radius at the root of the thread R, thereby determining the change trend of the relationship between the number of tightening turns N and the arc radius at the root of the thread R and providing a theoretical basis for designing the thread of the pin 1 and the coupling 2.

[0095] In some embodiments, when the arc radius at the root of the thread is 1.27 inches, the corresponding number of tightening turns is 7.01 turns, or when the taper is 0.10, the corresponding number of tightening turns is 8.9 turns. Compared with the arc radius of 2.1 inches, where the corresponding number of tightening turns is 1.6 turns, a tighter connection of the pin 1 and the coupling 2 is ensured, which improves the sealing of the connection (Fig. 5).

[0096] In some embodiments, the derivative of the number of tightening turns N to the thread pitch P satisfies the following relationship:

[0097]

[0098] where N is the number of tightening turns; - half the thread profile angle; tpr - thread taper; P - thread pitch; R - arc radius at the base of the thread.

[0099] Figure 6 shows the relationship between the number of tightening turns N and the thread pitch P for a threaded connection of drill pipes with increased torsional resistance according to the invention. In this graph, the abscissa axis represents the thread pitch P, and the ordinate axis represents the number of tightening turns N. As can be seen from the graph, with the other thread parameters fixed, a positive correlation is observed between the number of tightening turns N and the thread pitch P, which makes it possible to accurately control the change in the number of tightening turns N by finely adjusting the thread pitch P, thereby determining the change trend of the relationship between the number of tightening turns N and the thread pitch P and providing a theoretical basis for designing the threads of the pin 1 and the coupling 2.

[0100] In some embodiments, when the thread pitch is 7.257 inches, the corresponding number of tightening turns is 7.01 turns, or when the thread pitch is 6.35 inches, the corresponding number of tightening turns is 6.06 turns, or when the thread pitch is 10.16 inches, the corresponding number of tightening turns is 8.92 turns, which can significantly reduce the number of tightening turns and reduce non-production time, thereby improving work efficiency (Fig. 6).

[0101] Fig. 3 shows the dependence of the number of tightening turns N on the half angle of the thread profile For a drill pipe threaded connection with increased torsional resistance according to the present invention, the abscissa axis represents the half-angle of the thread profile, and the ordinate axis represents the number of tightening turns. It can be established that there is a negative correlation between the number of tightening turns and the half-angle of the thread profile, i.e., as the half-angle of the thread profile increases, the number of tightening turns decreases (Fig. 3).

[0102] In some embodiments, at a thread half angle of 30°, the corresponding number of tightening turns is 8.0 turns; at a thread half angle of 35°, the corresponding number of tightening turns is 7.0 turns; at a thread half angle of 45°, the corresponding number of tightening turns is 5.6 turns. This can significantly reduce the number of tightening turns, reduce non-production time, and improve the operating efficiency of the equipment.

[0103] Fig. 7 is a graph showing the relationship between the number of tightening turns N and the thread taper tpr and the arc radius at the thread root R for a threaded connection of drill pipes with increased torsional resistance, where the coordinates along the X axis are the arc radius at the thread root R, the coordinates along the Y axis are the thread taper tpr, and the coordinates along the vertical axis are the number of tightening turns N. The graph shows that the tendency of the influence of two parameters - taper and arc radius - on the number of tightening turns shows that, compared with the thread taper, the arc radius at the thread root has a greater influence on the number of tightening turns. When adjusting the thread parameters to obtain the appropriate number of tightening turns, according to the requirements, it is possible to control the degree of adjustment of the arc radius at the thread root and the thread taper (while maintaining the other parameters unchanged) to obtain a different number of tightening turns.For example, if there is a need to quickly reduce the number of tightening turns, one can consider increasing the degree of adjustment of the arc radius within reasonable limits, which allows for rapid adjustment of the number of tightening turns.

[0104] In some embodiments, the radius of the arc at the root of the thread R, the thread pitch P, the half angle of the thread profile and the thread taper tpr satisfy the following relationship:

[0105]

[0106] where θ is half the thread profile angle; tpr is the thread taper; P is the thread pitch; Rmax is the maximum value of the arc radius at the root of the thread.

[0107] After determining the thread pitch P, half the thread profile angle and the taper of the thread tpr in accordance with the design requirements, the calculation of the arc radius at the base of the thread using this ratio allows us to predict the distribution of stresses and deformations of the connection under complex loads, increasing the stability of the connection of nipple 1 and coupling 2.

[0108] In some embodiments, both ends of the drill pipe are connected to two other corresponding drill pipes (first and second drill pipes). For example, nipple 1 of this drill pipe is connected to coupling 2 of the first drill pipe, forming a type 01 connection, and coupling 2 of this drill pipe is connected to nipple 1 of the second drill pipe, forming a type 02 connection. Type 01 and type 02 connections may be either the same or different, depending on the specific working conditions.For example, when developing offshore oil and gas fields in the deepwater and ultra-deepwater areas of the Gulf of Mexico, as well as when drilling deep and ultra-deep wells (6,000 meters deep) and highly deviated wells onshore in North America, where the primary performance requirements for drill pipe connections include good fatigue strength, operational efficiency, and low repair rates, a connection type with a lower number of tightening turns (N) and a corresponding torque-resistance limit should be selected. For example, a connection with approximately 9 tightening turns and a torque-resistance limit of approximately 35,000 ft-lbs could be selected. Such a connection ensures high tightening speeds and simultaneously exhibits good torsional stability, meeting the requirements of ultra-deep drilling.

[0109] In some embodiments, the drill pipe has a plurality of design connection types (type 01, type 02, type 03, type 04, type 05, type 06, type 07, type 08, type 09, type 10, type 11, type 12, type 13, etc.), and all these connection types have a common range of the number of tightening turns N from 5 to 13 turns for each type. Each of these connection types has a corresponding minimum value of the torque resistance limit, and this minimum value for each connection type is less than the set torque resistance limit (10,000 ft-lbs).

[0110] In some embodiments, for a type 01 connection, the parameter ranges are: an outer diameter OD from 3 1 / 9 to 3 1 / 7 inches, an inner diameter ID from 1 1 / 3 to 1 2 / 3 inches, a thread taper from 1:9 to 1:7, an arc radius at the root of the thread from 0.04 to 0.06 inches, a number of tightening turns from 5 to 6 turns, a torque resistance limit from 11,000 to 13,000 ft-lbs.

[0111] Alternatively, the parameters of type 01 connection can be as follows: outside diameter OD - 3 1 / 8", inside diameter ID - 1 1 / 2", thread taper - 1:8, arc radius at the root of the thread - 0.05", the number of tightening turns - 5 turns, the torque limit is 12000 ft-lbs.

[0112] In some embodiments, for a type 02 connection, the parameter ranges are: an outer diameter OD from 3 1 / 3 to 3 3 / 7 inches, an inner diameter ID from 1 3 / 8 to 1 7 / 8 inches, a thread taper from 1:9 to 1:7, an arc radius at the root of the thread from 0.04 to 0.06 inches, a number of tightening turns from 5 to 6 turns, a torque resistance limit from 14,000 to 16,000 ft-lbs.

[0113] As an alternative embodiment, the parameters of the 02 type connection may have the following values: outside diameter OD - 3 3 / 8 inches, inside diameter ID - 1 5 / 8 inches, thread taper - 1:8, arc radius at the root of the thread - 0.05 inches, the number of tightening turns - 5 turns, the torque limit is 15,000 ft-lbs.

[0114] In some embodiments, for a type 03 connection, the parameter ranges are: an outer diameter OD from 3 2 / 3 to 4 1 / 4 inches, an inner diameter ID from 1 2 / 3 to 2 1 / 3 inches, a thread taper from 1:11 to 1:9, an arc radius at the root of the thread from 0.04 to 0.06 inches, a number of tightening turns from 7 to 9 turns, a torque resistance limit from 20,000 to 24,000 ft-lbs.

[0115] As an alternative embodiment, the parameters of the 03 type connection may be as follows: outside diameter OD - 4 inches, inside diameter ID - 2 inches, thread taper - 1:10, arc radius at the root of the thread - 0.05 inches, the number of tightening turns - 8 turns, the torque limit is 23,000 ft-lbs.

[0116] In some embodiments, for a type 04 connection, the parameter ranges are: an outer diameter OD from 4 1 / 9 to 4 3 / 8 inches, an inner diameter ID from 2 1 / 7 to 2 3 / 8 inches, a thread taper from 1:11 to 1:9, an arc radius at the root of the thread from 0.04 to 0.06 inches, a number of tightening turns from 7 to 9 turns, a torque resistance limit from 23,000 to 27,000 ft-lbs.

[0117] As an alternative embodiment, the parameters of the type 04 connection may have the following values: outside diameter OD - 4 1 / 8 inches, inside diameter ID - 2 1 / 8 inches, thread taper - 1:10, arc radius at the root of the thread - 0.05 inches, the number of tightening turns - 8 turns, the torque limit is 25,000 ft-lbs.

[0118] In some embodiments, for a type 05 connection, the parameter ranges are: an outer diameter OD from 4 5 / 8 to 5 inches, an inner diameter ID from 2 9 / 16 to 2 15 / 16 inches, a thread taper from 1:14 to 1:11, an arc radius at the root of the thread from 0.05 to 0.07 inches, a number of tightening turns from 6 to 8 turns, a torque resistance limit from 34,000 to 36,000 ft-lbs.

[0119] As an alternative embodiment, the parameters of the type 05 connection may have the following values: outside diameter OD - 4 7 / 8 inches, inside diameter ID - 2 11 / 16 inches, thread taper - 1:12, arc radius at the root of the thread - 0.06 inches, the number of tightening turns - 7 turns, the torque limit is 35,000 ft-lbs.

[0120] In some embodiments, for a type 06 connection, the parameter ranges are: an outer diameter OD from 5 1 / 5 to 5 3 / 4 inches, an inner diameter ID from 2 3 / 4 to 3 1 / 3 inches, a thread taper from 1:13 to 1:10, an arc radius at the root of the thread from 0.05 to 0.07 inches, a number of tightening turns from 6 to 8 turns, a torque resistance limit from 49,000 to 61,000 ft-lbs.

[0121] As an alternative embodiment, the parameters of the 06 type connection may be as follows: outside diameter OD - 5 1 / 4 inches, inside diameter ID - 3 inches, thread taper - 1:12, arc radius at the root of the thread - 0.06 inches, the number of tightening turns - 7 turns, the torque limit is 50,000 ft-lbs.

[0122] Drill pipe with connections of types 01, 02, 03, 04, 05, or 06 have moderate torque resistance and are suitable for applications requiring standard torque transmission. For example, in drill pipe connections on small oil rigs, they effectively transmit torque during rotary drilling, ensuring normal operation of the drill bit. At the same time, these connection types exhibit significant tensile strength, allowing them to withstand axial loads from the drill string's own weight and the bit's lifting force, preventing pipe rupture and ensuring equipment safety and reliability. Furthermore, the moderate outer and inner diameters of these connections do not take up excessive space in the confined spaces of small drilling rigs.

[0123] In some embodiments, for a type 07 connection, the parameter ranges are: an outer diameter OD from 6 1 / 2 to 6 7 / 8 inches, an inner diameter ID from 3 3 / 4 to 4 1 / 3 inches, a taper from 1:13 to 1:10, an arc radius at the root of the thread from 0.05 to 0.07 inches, a number of tightening turns from 6 to 8 turns, a torque resistance limit from 89,000 to 91,000 ft-lbs.

[0124] As an alternative embodiment, the parameters of the 07 type connection may be as follows: outside diameter OD - 6 5 / 8 inches, inside diameter ID - 4 inches, taper - 1:12, arc radius at the root of the thread - 0.06 inches, the number of tightening turns - 7 turns, the torque limit is 90,000 ft-lbs.

[0125] In some embodiments, for a type 08 connection, the parameter ranges are: an outer diameter OD from 6 4 / 5 to 7 2 / 7 inches, an inner diameter ID from 3 3 / 4 to 4 1 / 2 inches, a taper from 1:15 to 1:12, an arc radius at the root of the thread from 0.06 to 0.08 inches, a number of tightening turns from 5 to 8 turns, a torque resistance limit from 100,000 to 120,000 ft-lbs.

[0126] As an alternative embodiment, the parameters of the 08 type connection may be as follows: outside diameter OD - 7 inches, inside diameter ID - 4 1 / 4 inches, taper - 1:14, arc radius at the root of the thread - 0.07 inches, the number of tightening turns - 6 turns, the torque limit is 110,000 ft-lbs.

[0127] In some embodiments, for a type 09 connection, the parameter ranges are: an outer diameter OD from 7 7 / 8 to 8 1 / 8 inches, an inner diameter ID from 4 3 / 4 to 5 1 / 5 inches, a taper from 1:15 to 1:13, an arc radius at the root of the thread from 0.06 to 0.08 inches, a number of tightening turns from 5 to 8 turns, a torque resistance limit from 130,000 to 170,000 ft-lbs.

[0128] As an alternative embodiment, the parameters of the type 09 connection may be as follows: outside diameter OD - 8 inches, inside diameter ID - 5 inches, taper - 1:14, arc radius at the root of the thread - 0.07 inches, the number of tightening turns - 6 turns, the torque limit is 150,000 ft-lbs.

[0129] In some embodiments, for a type 10 connection, the parameter ranges are: an outer diameter OD from 8 1 / 3 to 8 3 / 4 inches, an inner diameter ID from 4 3 / 4 to 5 3 / 4 inches, a taper from 1:18 to 1:15, an arc radius at the root of the thread from 0.06 to 0.08 inches, a number of tightening turns from 5 to 8 turns, a torque resistance limit from 180,000 to 200,000 ft-lbs.

[0130] As an alternative embodiment, the parameters of the Type 10 connection may be as follows: outside diameter OD - 8 1 / 2 inches, inside diameter ID - 5 1 / 4 inches, taper - 1:16, arc radius at the root of the thread - 0.07 inches, the number of tightening turns - 6 turns, the torque limit is 190,000 ft-lbs.

[0131] In some embodiments, for a type 11 connection, the parameter ranges are: an outer diameter OD from 8 3 / 8 to 8 7 / 8 inches, an inner diameter ID from 5 1 / 4 to 5 3 / 4 inches, a taper from 1:18 to 1:15, an arc radius at the root of the thread from 0.06 to 0.08 inches, a number of tightening turns from 5 to 8 turns, a torque resistance limit from 180,000 to 190,000 ft-lbs.

[0132] As an alternative embodiment, the parameters of the Type 11 connection may be as follows: outside diameter OD - 8 5 / 8 inches, inside diameter ID - 5 1 / 2 inches, taper - 1:16, arc radius at the root of the thread - 0.07 inches, the number of tightening turns - 6 turns, the torque limit is 185,000 ft-lbs.

[0133] In some embodiments, for a type 12 connection, the parameter ranges are: an outside diameter OD from 9 1 / 2 to 10 inches, an inside diameter ID from 5 7 / 8 to 6 1 / 4 inches, a taper from 1:18 to 1:15, an arc radius at the root of the thread from 0.06 to 0.08 inches, a number of tightening turns from 5 to 8 turns, a torque resistance limit from 300,000 to 330,000 ft-lbs.

[0134] As an alternative embodiment, the parameters of the Type 12 connection may be as follows: outside diameter OD - 9 7 / 8 inches, inside diameter ID - 6 inches, taper - 1:16, arc radius at the root of the thread - 0.07 inches, the number of tightening turns - 6 turns, the torque limit is 310,000 ft-lbs.

[0135] In some embodiments, for a type 13 connection, the parameter ranges are: an outside diameter OD from 10 1 / 2 to 11 inches, an inside diameter ID from 6 1 / 8 to 7 inches, a taper from 1:18 to 1:15, an arc radius at the root of the thread from 0.06 to 0.08 inches, a number of tightening turns from 5 to 8 turns, a torque resistance limit from 340,000 to 370,000 ft-lbs.

[0136] As an alternative embodiment, the parameters of the type 13 connection may be as follows: outside diameter OD - 10 5 / 8 inches, inside diameter ID - 6 5 / 8 inches, taper - 1:16, arc radius at the root of the thread - 0.07 inches, the number of tightening turns - 6 turns, the torque limit is 350,000 ft-lbs.

[0137] Drill pipe with type 08, 09, 10, 11, 12, or 13 connections feature high torque resistance, meeting the requirements of high-torque connections. They effectively transmit the required torque and resist torque fluctuations during drilling, preventing connection damage due to overload. These connection types also exhibit high tensile strength, providing excellent axial load-bearing properties. Furthermore, the larger outside diameter of these connections reduces hydraulic resistance and improves drilling fluid flow.

[0138] All parameters of the above-described alternative embodiments are shown in Table 1.

[0139] Table 1

[0140] Connection type External diameter OD Inner diameter ID Thread taper Arc radius at thread root (inches) Number of tightening turns (turns) Torque Limit (ft-lbs) Type 01 3 1 / 8 1 1 / 2 1 / 8 0,05 5 12000 Type 02 3 3 / 8 1 5 / 8 1 / 8 0,05 5 15000 Type 03 4 2 1 / 10 0,05 8 23000 Type 04 4 1 / 8 2 1 / 8 1 / 10 0,05 8 25000 Type 05 4 7 / 8 2 11 / 16 1 / 12 0,06 7 35000 Type 06 5 1 / 4 3 1 / 12 0,06 7 50000 Type 07 6 5 / 8 4 1 / 12 0,06 7 90000 Type 08 7 4 1 / 4 1 / 14 0,07 6 110000 Type 09 8 5 1 / 14 0,07 6 150000 Type 10 8 1 / 2 5 1 / 4 1 / 16 0,07 6 190000 Type 11 8 5 / 8 5 1 / 2 1 / 16 0,07 6 185000 Type 12 9 7 / 8 6 1 / 16 0,07 6 310000 Type 13 10 5 / 8 6 5 / 8 1 / 16 0,07 6 350000

[0141] An additional embodiment of a threaded connection of drill pipes with increased torsional resistance includes a nipple 1 and a coupling 2, respectively located at both ends of a drill pipe, wherein the nipple 1 and the coupling 2 are installed coaxially. The outer surface of the nipple 1 forms a first conical connecting surface, and the inner surface of the coupling 2 forms a second conical connecting surface, wherein the inclination angle of the first and second conical connecting surfaces is the same. On the first and second conical connecting surfaces, respectively, external and internal threads are formed, wherein the external thread is intended for a threaded connection with the corresponding second conical connecting surface of the coupling 2 of the first drill pipe, and the internal thread is intended for a threaded connection with the corresponding first conical connecting surface of the nipple 1 of the second drill pipe.Nipple 1 and the coupling 2 corresponding to it, as well as coupling 2 and the nipple 1 corresponding to it, belong to a certain type of connection, wherein each type of connection has a given range of the number of tightening turns N, each type of connection is determined by the thread parameters of nipple 1 and coupling 2, the thread parameters of nipple 1 and coupling 2 include the radius of the arc at the base of the thread R, half the angle of the thread profile θ, the taper of the thread tpr and the thread pitch P, wherein the number of tightening turns N and the specified thread parameters satisfy the following relationship:.

[0142]

[0143] where N is the number of tightening turns; - half the thread profile angle; tpr - thread taper; P - thread pitch; R - arc radius at the base of the thread.

[0144] By selecting thread parameters, the number of tightening turns N can be accurately calculated, which allows for optimizing the mechanical characteristics of the threaded connection. For example, when the half-angle of the thread profile , the thread taper tpr, the thread pitch P and the arc radius at the base of the thread R are determined in accordance with the design, the use of this ratio to determine the number of tightening turns N ensures uniform distribution of stresses when transmitting significant torques and axial forces, preventing the concentration of local stresses and the formation of fatigue cracks, which significantly increases the fatigue life and reliability of the drill pipe connection.

[0145] In some embodiments, the derivative of the number of tightening turns N to the thread taper tpr satisfies the following relationship:

[0146]

[0147] where N is the number of tightening turns; - half the thread profile angle; tpr - thread taper; P - thread pitch; R - arc radius at the base of the thread.

[0148] The graph shown (Fig. 4) shows the thread taper tpr along the abscissa axis, and the number of tightening turns N along the ordinate axis. This graph demonstrates the inverse relationship between the number of tightening turns N and the thread taper tpr, with all other thread parameters held constant. This allows for precise adjustment of the number of tightening turns N by minor adjustments to the thread taper tpr, identifying trends in this relationship and providing a theoretical basis for designing the threads of nipple 1 and coupling 2.

[0149] In some embodiments (Fig. 4), with a thread taper of 1 / 10, the corresponding number of tightening turns is 7.01 turns, which, compared with a taper of 1 / 16 (11.8 turns), significantly reduces the number of tightening turns and reduces the non-production time (NPT), improving work efficiency. In turn, with a thread taper of 1 / 6 (4.2 turns), a tighter connection between the nipple 1 and the coupling 2 is ensured, thereby increasing the speed and efficiency of pipe tightening.

[0150] In some embodiments, the derivative of the number of tightening turns N to the radius of the arc at the root of the thread R satisfies the following relationship:

[0151]

[0152] where N is the number of tightening turns; - half the thread profile angle; tpr - thread taper; P - thread pitch; R - arc radius at the base of the thread.

[0153] In the graph shown (Fig. 5), the abscissa axis indicates the arc radius at the root of the thread R, and the ordinate axis indicates the number of tightening turns N. This graph demonstrates the inverse relationship between the number of tightening turns N and the arc radius at the root of the thread R, while holding all other thread parameters fixed. This allows for precise adjustment of the number of tightening turns N by minor adjustments to the arc radius, determining the change trends in this relationship and providing a theoretical basis for the design of the threads of nipple 1 and coupling 2.

[0154] In some embodiments (Fig. 5), with an arc radius at the root of the thread of 1.27 mm, the corresponding number of tightening turns is 7.01 turns, or with an arc radius at the root of the thread of 0.97 mm - 8.9 turns. Compared with an arc radius at the root of the thread of 2.1 mm (1.6 turns), a tighter connection of the pin 1 and the coupling 2 is ensured, improving the fatigue characteristics of the connection.

[0155] In some embodiments, the derivative of the number of tightening turns N to the thread pitch P satisfies the following relationship:

[0156]

[0157] where N is the number of tightening turns; - half the thread profile angle; tpr - thread taper; P - thread pitch; R - arc radius at the base of the thread.

[0158] In the graph shown (Fig. 6), the abscissa axis indicates the thread pitch P, and the ordinate axis indicates the number of tightening turns N. It can be seen from the graph that, with other thread parameters fixed, there is a positive correlation between the number of tightening turns N and the thread pitch P. This makes it possible to accurately control the change in the number of tightening turns by finely adjusting the thread pitch, determining the change trend of the relationship between the number of tightening turns and the thread pitch, providing a theoretical basis for the design of the thread of the nipple 1 and the coupling 2.

[0159] In some embodiments (Fig. 6), with a thread pitch of 7.257 mm, the number of tightening turns is 7.01 turns, with a thread pitch of 6.35 mm - 6.06 turns, with a thread pitch of 10.16 mm - 8.92 turns. This can significantly reduce the number of tightening turns, reduce non-production time and improve the efficiency of the installation.

[0160] In some embodiments (Fig. 3), where the abscissa axis indicates the half-angle values ​​of the thread profile , and along the ordinate axis is the number of tightening turns N, it was found that there is a negative correlation between the number of tightening turns and the half-angle of the thread profile: with an increase in the half-angle of the thread profile, the number of tightening turns decreases.

[0161] In some embodiments, the number of tightening turns at a thread half angle of 30° is 8.0 turns, at a thread half angle of 35° it is 7.0 turns, and at a thread half angle of 45° it is 5.6 turns. This significantly reduces the number of tightening turns, reduces non-production time, and improves work efficiency.

[0162] In some embodiments (Fig. 7), where the X-axis coordinates are the arc radius at the root of the thread R, the Y-axis coordinates are the thread taper tpr, and the vertical axis coordinates are the number of tightening turns N, it can be seen that the tendency of the influence of the taper and the arc radius at the root of the thread on the number of tightening turns shows that the arc radius has a greater influence on the number of tightening turns than the taper. When adjusting the thread parameters to obtain an appropriate number of tightening turns, it is possible to control the degree of adjustment of the arc radius and taper (with other parameters fixed) in accordance with the design requirements to obtain a different number of tightening turns. For example, when it is necessary to quickly reduce the number of tightening turns, it is possible to consider increasing the degree of adjustment of the arc radius within a reasonable range, which makes it possible to achieve rapid adjustment of the number of tightening turns.

[0163] In some embodiments, the arc radius at the root of the thread R, the thread pitch P, the half angle of the thread profile θ and the taper of the thread tpr satisfy the following relationship:

[0164]

[0165] where θ is half the thread profile angle; tpr is the thread taper; P is the thread pitch; Rmax is the maximum value of the arc radius at the root of the thread.

[0166] After determining the thread pitch P, thread half angle θ and thread taper tpr according to the design requirements, calculating the arc radius at the root of the thread R according to this ratio can predict the distribution of stress and strain of the connection under complex loads, improving the stability of the connection of nipple 1 and coupling 2.

[0167] In some embodiments, each connection type has a specified range of tightening turns (N) and torque resistance limit: the tightening turns range from 5 to 13 turns, and the torque resistance limit is at least 10,000 ft-lbs. The tightening turns determine the tightening speed of the mating drill pipes: the more turns, the lower the tightening speed, and vice versa. The tightening speed directly affects the proportion of non-production time during tripping operations: a higher speed reduces tightening time, increasing the efficiency of working time. However, an excessively high speed (with a small number of turns) can degrade the quality of the connection between pin 1 and coupling 2, reducing its stability.

[0168] The torsional resistance of a drill pipe threaded connection determines the maximum stress that nipple 1 and coupling 2 can withstand when subjected to torque, directly reflecting the stability and durability of the connection under torsional loads. The higher the torque resistance limit, the better the material's resistance to torsional deformation, resulting in a stronger and more durable connection between nipple 1 and coupling 2. A higher torque resistance limit also allows for increased drilling speed due to the ability to withstand higher torques, penetrate geological formations faster, improve drilling speed and efficiency, and reduce the incidence of drill pipe sticking, improving overall productivity.The conical coupling surface design, coupled with a precisely specified tightening thread count (5-13 threads) and a minimum torque resistance limit of 10,000 ft-lbs, optimizes the connection structure and mechanical performance, provides efficient torque transmission in challenging drilling conditions, reduces failure rates and improves overall drilling efficiency.

[0169] In some embodiments, the radius of the arc at the root of the thread R for each pin 1 and coupling 2 of any type of connection is in the range of 0.038-0.08 inches, which ensures a more uniform distribution of contact stresses along the axis and circumference of the thread, the ability to withstand complex variable loads from the marine environment and the drilling process, an effective reduction in stress concentration at the root of the thread, a reduction in the formation and propagation of fatigue cracks and long-term reliability of the connection of drill pipes under severe operating conditions.

[0170] In some embodiments, the half-angle of the thread profile θ for each nipple 1 and coupling 2 of any type of connection is in the range of 27.5° to 44.5°. This half-angle range ensures uniform load distribution between the threads under the influence of internal pressure during the connection of drill pipes, preventing stress concentration and damage to individual threads, which significantly improves the overall reliability of the connection and its tightness, effectively preventing leakage of the transported medium and ensuring the safe and stable operation of the pipeline system.

[0171] In some embodiments, the thread taper (tpr) of each nipple 1 and coupling 2 of any connection type ranges from 1 / 16 to 1 / 6. This taper ensures a gradual, tight fit between nipple 1 and coupling 2 during tightening, particularly creating a reliable sealing contact in the area of ​​the sealing surfaces. As tightening progresses, the contact pressure between the threads and the sealing surfaces increases uniformly, maximizing the speed and efficiency of tightening the nipple and coupling.

[0172] In some embodiments, when the connection type is a design type, the following relationship exists between the thread taper tpr and the arc radius at the root of the thread R: when the taper is 1 / 16, the arc radius is 0.05-0.065 inches; when the taper is 1 / 12, the arc radius is 0.04-0.060 inches; when the taper is 1 / 10, the arc radius is 0.045-0.055 inches. This ensures a more uniform and rational stress distribution in the threaded connection, effectively reduces stress concentration, improves the bearing capacity of the connection and fatigue strength, which can withstand various complex loads.

[0173] In some embodiments, the thread pitch P for each nipple 1 and coupling 2 of any connection type ranges from 0.250 to 0.364 inches. This ensures a more uniform load distribution when significant tensile forces are applied to the pipe connection. Compared to a thread pitch P that is too close or too sparse, this range allows each thread to effectively support the load, reducing stress concentration and preventing thread deformation or damage due to localized overloads.

[0174] The present invention also discloses a method for designing a torsion-resistant drill pipe connection, including: a first step of determining ranges of the number of tightening turns N and a minimum torque resistance limit for a design connection type based on standard and special connection types, wherein the number of tightening turns N of the design type is 5-13 turns, and the torque resistance limit is not less than 10,000 ft-lbs; a second step of setting thread parameters of the design connection type, including the arc radius at the root of the thread R, the thread taper tpr, the half angle of the thread profile θ and the thread pitch P, and then selecting the profile radius and the thread pitch based on the set ranges; a third step of selecting a range of the thread taper tpr based on the set ranges of the number of tightening turns N and the torque resistance limit;the fourth step is to determine a series of values ​​of the arc radius at the base of the thread R, corresponding to the selected range of thread taper tpr, based on the relationship between the thread parameters and the number of tightening turns N.

[0175] This design method enables the determination of key design connection parameters based on empirical data for standard and special types, providing the necessary flexibility. For example, in oil production, where connection requirements vary significantly depending on well depth, geological conditions, and production technology, this method enables the development of optimal designs for various applications, such as shallow, deep, and ultra-deep wells, as well as various rock formations.For shallow wells with relatively simple geological conditions, a lower torque resistance limit can be selected without considering the influence of the tightening turns number, such as 10 tightening turns and a corresponding lower torque resistance limit (e.g., 20,000 ft-lbs); for production in deep, ultra-deep or horizontal wells, a higher torque resistance limit (110,000 ft-lbs) and a smaller number of tightening turns (e.g., 6 turns) should be selected to meet the requirements of complex operating conditions.

[0176] In some embodiments, the number of tightening turns N, the radius of the arc at the root of the thread R, the half angle of the thread profile , the thread taper tpr and the thread pitch P satisfy the following relationship:

[0177]

[0178] where N is the number of tightening turns; - half the thread profile angle; tpr - thread taper; P - thread pitch; R - arc radius at the base of the thread.

[0179] By selecting thread parameters, the number of tightening turns can be precisely calculated, optimizing the mechanical properties of the threaded connection. For example, when the thread half-angle, taper, thread pitch, and arc radius are determined according to the design, using this ratio allows for a number of tightening turns that ensures uniform stress distribution in the thread when transmitting significant torque and axial force, avoiding stress concentrations that lead to fatigue cracks, thereby significantly increasing the fatigue life and reliability of the pipe connection.

[0180] In some embodiments, it is necessary to select an appropriate number of tightening turns N and a torque resistance limit within a reasonable range (between the theoretical minimum and maximum number of tightening turns) and a reasonable range of torque resistance limit (theoretical minimum limit) in order to best satisfy the requirements for tightening speed and torsional strength.

[0181] Table 2 below shows examples of different types of tool joints available on the market, such as the API NC38 (standard tool joint) and the HLIST39 special tool joint. The API NC38 is the basic tool joint with the lowest torque resistance limit, while the HLIST39 is a special tool joint with an improved torque resistance limit. The tightening thread number ranges from 5 to 13 threads, and the torque resistance limit is no less than 32,300 ft-lbs. This ensures the optimal tightening thread number for the coupling and nipple, reduces downtime, and provides sufficient torque resistance to meet the operational requirements of drill pipe.

[0182] Table 2

[0183] Lock type Limit of resistance External diameter OD Inner diameter ID Limit of resistance to cr. moment Number of tightening turns Inches Inches Foot-pounds Coils API NC38° Base 5 2 9 / 16 20300 5. 0 HLIST39 Optimal 4 7 / 8 2 11 / 16 35900 13. 1 Construction of the lock 4 7 / 8 2 11 / 16 5. 0-13. 1

[0184] Although the tightening range of 5-13 turns already meets the requirements for screwing speed, the number of tightening turns can be further divided into three ranges according to the screwing speed requirements of drill pipes at the drilling site: high-efficiency range (5.0~7.3 turns), medium range (7.4~10.5) and normal range (10.6~13.0). The high-efficiency range (5.0~7.3) is suitable for short-term occasions that require significant reduction in non-production time, while the medium range (7.4~10.5) and normal range (10.6~13.0) are applied to occasions that require the best connection between the coupling and the nipple.

[0185] In some embodiments (Table 3), the thread taper tpr and the arc radius at the root of the thread R also correspond to the following ratios: with a taper of 1 / 16, the corresponding arc radius is 0.05-0.065 inches, with a taper of 1 / 12, the corresponding arc radius is 0.04-0.060 inches, with a taper of 1 / 10, the corresponding arc radius is 0.045-0.055 inches. This ratio ensures a more uniform and rational stress distribution in the threaded pipe joint, effectively reduces stress concentration, improves the bearing capacity of the joint and its fatigue strength, which can withstand various complex loads.

[0186] Table 3

[0187] Number of tightening turns Torque resistance Thread taper Half angle of the thread profile 11. 6 36504 1 / 16 0.05 9. 9 36925 0.055 8. 2 37349 0.06 6. 4 37773 0.065 11. 2 33879 1 / 12 0.04 9. 9 34291 0.045 8. 6 34703 0.05 7. 3 35117 0.055 6. 0 35531 0.06 7. 9 32562 1 / 10 0.045 6. 9 32966 0.05 5. 8 33372 0.055

[0188] In some embodiments, the torque resistance limit of the coupling and nipple is calculated using the following formula:

[0189]

[0190] where A1 is the cross-sectional area of ​​the main end; A2 is the cross-sectional area of ​​the additional end; R s1 - average radius of the contact ring of the main end; Rs2 - average radius of the contact ring of the additional end; T - ultimate torque; S - minimum yield strength of the material; P - thread pitch; - coefficient of friction; - half the angle of the thread profile.

[0191]

[0192] Where is R t - average radius of the threaded part; L pc - nipple length;

[0193] R s1 = 1 / 4 (OD + Qc); the maximum value is limited by OD when A p = A b ;

[0194] R s2 = ¼ (ID + D n );

[0195] A1 - section of the main end, taken as the smaller of the values ​​A b and A p ;

[0196] , in the absence of a relief groove;

[0197] , if there is a relief groove;

[0198] Where is D RG - relief groove diameter; C - average thread diameter at the control point; ID - inner diameter; OD - outer diameter;

[0199] B = 2(H / 2 - S_rs) + tpr * 1 / 8 * 1 / 12, in;

[0200] Where H is the height of the original thread triangle; S_rs is the cut height at the base of the thread; tpr is the taper of the thread;

[0201]

[0202] Q c - coupling bore diameter;

[0203] A_2 = 4 (D_n^2 - ID^2);

[0204] D n - diameter of the nipple nose;

[0205] E = tpr * 3 / 8 * 1 / 12;

[0206] According to Table 1 and the above formulas, the torque-resisting capacity of each type of tool joint also depends on the corresponding inner diameter, outer diameter, taper, thread pitch, and half-angle of the coupling and pin. When the other parameters in the torsional resistance formula remain unchanged, a torque-resisting capacity that meets design requirements can be obtained by adjusting various connection geometric parameters (inner diameter, outer diameter, taper, thread pitch, and half-angle) to meet the torque-resisting capacity requirements of the tool joint under actual working conditions.

[0207] For example, when designing a deep drilling connection, since it needs to withstand higher torque, the outer diameter, inner diameter, or pitch diameter of the thread and other parameters can be increased, and the torque resistance limit of the connection can be calculated and optimized according to the formula, so as to ensure that it can meet the drilling requirements of complex geological conditions in deep wells.

[0208] Furthermore, this formula helps accurately predict the torque resistance of drill pipe connections. By entering various combinations of geometric parameters, a fairly accurate estimate of the connection's torque resistance limit can be obtained in advance. For example, when developing a high-strength connection, using the torque resistance limit formula and comparing it with the output torque of existing drilling equipment can determine the suitability of the new connection, avoiding problems such as connection failure or equipment damage caused by insufficient or excessive torque resistance.

[0209] In the description of the invention, it should be explained that terms denoting orientation or relative position, such as "center," "top," "bottom," "left," "right," "vertical," "horizontal," "inner," "outer," and the like, refer to the orientation or arrangement shown in the accompanying drawings or to the usual position of the drill pipe connection when used. These terms are used solely for convenience of description and to simplify the presentation, and are not used to indicate or imply that the described devices or elements must have a specific orientation, configuration, or mode of operation. Therefore, they should not be understood as limiting the protection of the invention. In addition, the terms "first," "second," "third," and the like are used only to distinguish between descriptions and should not be interpreted as indicating relative importance.

[0210] Furthermore, the terms "horizontal," "vertical," and similar terms do not imply that components must be strictly horizontal or vertical. For example, "horizontal" merely indicates a direction more horizontal than "vertical," not that the structure must be perfectly horizontal—a slight tilt is permitted.

[0211] The description of the invention should further clarify that, unless otherwise specified, the terms "installation," "assembly," "connection," and "connection" should be interpreted broadly. For example, a connection may be: fixed, detachable, or permanent; mechanical or electrical; direct or indirect through an intermediate element, and also represent an internal connection of two components. A person skilled in the art will be able to understand the specific meaning of these terms in the context of the invention depending on the specific circumstances.

[0212] The above description relates only to preferred embodiments of the invention and does not limit its scope. Those skilled in the art can make various changes and modifications within the spirit and principles of the invention. All such changes, equivalent substitutions, and improvements fall within the scope of the present invention.

[0213] Thus, the presented torsion-resistant drill pipe connection and its design method have succeeded in reducing non-production time and improving the working efficiency of the drilling platform, while ensuring high torsion resistance of the connection.

Claims

1. A torsion-resistant drill pipe connection comprising a nipple and a coupling mounted at both ends of the pipe and arranged coaxially, wherein the outer surface of the nipple and the inner surface of the coupling form a first conical connecting surface and a second conical connecting surface, respectively, with the same angle of inclination, wherein the first and second conical surfaces are provided with an external and an internal thread, respectively, wherein the external thread is intended for a threaded connection with a corresponding second conical surface of the inner part of the first drill pipe, and the internal thread is intended for a threaded connection with a corresponding first conical surface of the outer part of the second drill pipe, wherein the connection of the nipple and the coupling forms a certain type of connection,and each type of connection is characterized by the parameters of the threads of the external and internal parts and has a specified range of the number of tightening turns of 5-13 turns and a specified torque resistance limit of at least 10,000 ft-lbs, while the number of tightening turns and the thread parameters satisfy the following relationship:, where N is the number of tightening turns; - half the angle of the thread profile; tpr - thread taper; P - thread pitch; R is the radius of the arc at the base of the thread.

2. A torsion-resistant drill pipe connection according to paragraph 1, characterized in that the parameter of the nipple and coupling thread is the radius of curvature along the root of the thread, the size of which for any type of connection is 0.038-0.08 inches.

3. A torsion-resistant connection of drill pipes according to paragraph 2, characterized in that the parameter of the thread of the nipple and coupling is half the angle of the thread profile, the size of which for any type of connection is 27.5-44.5°.

4. A torsion-resistant connection of drill pipes according to paragraph 3, characterized in that the parameter of the thread of the nipple and coupling is the taper of the thread, which for any type of connection is in the range from 1 / 16 to 1 / 6.

5. A torsion-resistant drill pipe connection according to claim 4, characterized in that, for the design type of connection, the following relationships are established between the taper of the thread and the radius of the arc at the root of the thread: with a taper of 1 / 16, the radius of the arc is 0.05-0.065 inches; with a taper of 1 / 12, the radius of the arc is 0.04-0.06 inches; with a taper of 1 / 10, the radius of the arc is 0.045-0.055 inches.

6. A torsion-resistant drill pipe connection according to paragraph 5, characterized in that the thread parameter is the thread pitch, the size of which for any type of connection is 0.250-0.364 inches.

7. A torsion-resistant drill pipe connection according to paragraph 6, characterized in that the derivative of the number of tightening turns to the taper of the thread satisfies the following relationship: where N is the number of tightening turns; - half the angle of the thread profile; tpr - thread taper; P - thread pitch; R is the radius of the arc at the base of the thread.

8. A torsion-resistant drill pipe connection according to claim 7, characterized in that the derivative of the number of tightening turns to the arc radius satisfies the following relationship: where N is the number of tightening turns; - half the angle of the thread profile; tpr - thread taper; P - thread pitch; R is the radius of the arc at the base of the thread.

9. A torsion-resistant drill pipe connection according to paragraph 8, characterized in that the derivative of the number of tightening turns to the thread pitch satisfies the following relationship: where N is the number of tightening turns; - half the angle of the thread profile; tpr - thread taper; P - thread pitch; R is the radius of the arc at the base of the thread.

10. A torsion-resistant drill pipe connection according to claim 9, characterized in that the arc radius, thread pitch, half-angle of the thread profile, and taper of the thread satisfy the following relationship: where θ is half the angle of the thread profile; tpr - thread taper; P - thread pitch; Rmax - maximum value of the arc radius at the base of the thread.

11. A torsion-resistant drill pipe connection comprising a nipple and a coupling mounted at both ends of the pipe and arranged coaxially, wherein the outer surface of the nipple and the inner surface of the coupling form a first conical connecting surface and a second conical connecting surface, respectively, with the same angle of inclination, wherein the first and second conical surfaces are provided with an external and an internal thread, respectively, wherein the external thread is configured to be threadedly connected to a corresponding second conical surface of the inner part of the first drill pipe, and the internal thread is configured to be threadedly connected to a corresponding first conical surface of the outer part of the second drill pipe, wherein the connection of the nipple and the coupling form a specific type of connection, and each type of connection is characterized by a given range of the number of tightening turns,and also the parameters of the nipple and coupling thread: the radius of the arc at the base of the thread, half the angle of the thread profile, the taper of the thread and the thread pitch, while the number of tightening turns and the specified thread parameters satisfy the following relationship:, where N is the number of tightening turns; - half the angle of the thread profile; tpr - thread taper; P - thread pitch; R is the radius of the arc at the base of the thread.

12. A torsion-resistant drill pipe connection according to paragraph 11, characterized in that the derivative of the number of tightening turns to the taper of the thread satisfies the following relationship: where N is the number of tightening turns; - half the angle of the thread profile; tpr - thread taper; P - thread pitch; R is the radius of the arc at the base of the thread.

13. A torsion-resistant drill pipe connection according to claim 11, characterized in that the derivative of the number of tightening turns to the radius of the arc at the base of the thread satisfies the following relationship: where N is the number of tightening turns; - half the angle of the thread profile; tpr - thread taper; P - thread pitch; R is the radius of the arc at the base of the thread.

14. A torsion-resistant drill pipe connection according to claim 11, characterized in that the derivative of the number of tightening turns to the thread pitch satisfies the following relationship: where N is the number of tightening turns; - half the angle of the thread profile; tpr - thread taper; P - thread pitch; R is the radius of the arc at the base of the thread.

15. A torsion-resistant drill pipe connection according to claim 11, characterized in that the arc radius, thread pitch, thread taper, and half-angle of the thread profile satisfy the following relationship: where θ is half the angle of the thread profile; tpr - thread taper; P - thread pitch; R max - maximum value of the arc radius at the base of the thread.

16. A torsion-resistant drill pipe connection according to claim 11, wherein each type of connection has a specified tightening range of 5-13 turns and a specified torque resistance limit of 10,000 ft-lbs.

17. A torsion-resistant drill pipe connection according to claim 11, characterized in that for any type of connection, the radius of the arc at the base of the thread is in the range of 0.038-0.08 inches.

18. A torsion-resistant drill pipe connection according to claim 11, characterized in that for any type of connection, the half angle of the thread profile is in the range of 27.5-44.5°.

19. A torsion-resistant drill pipe connection according to claim 11, characterized in that for any type of connection the taper of the thread is in the range from 1 / 16 to 1 / 6.

20. A torsion-resistant drill pipe connection according to claim 11, characterized in that, for the design type of connection, the following relationships must exist between the thread taper and the arc radius: for a thread taper of 1 / 16, the arc radius is in the range of 0.05-0.065 inches, for a thread taper of 1 / 12, the arc radius is in the range of 0.04-0.06 inches, and for a taper of 1 / 10, the arc radius is in the range of 0.045-0.055 inches.

21. A torsion-resistant drill pipe connection according to claim 11, characterized in that for any type of connection the thread pitch is in the range of 0.25-0.364 inches.

22. A method for connecting drill pipes that is torsion-resistant includes connecting both ends of a drill pipe to two other corresponding drill pipes in such a way that the nipple of this drill pipe is connected to the coupling of the first drill pipe, forming a first connection, and the coupling of this drill pipe is connected to the nipple of the second drill pipe, forming a second connection, also includes determining a range of the number of tightening turns and a torque resistance limit for the first and second connections, also includes establishing the thread parameters of the design type of connection - the first and second connections, taking into account the radius of the arc at the root of the thread, the taper of the thread, the half angle of the thread profile and the thread pitch, wherein the selection of the values ​​of the arc radius and the thread pitch is made on the basis of the established range of the number of tightening turns and the torque resistance limit,the selection of the thread taper range is made on the basis of the established range of the number of turns and the torque resistance limit, and the determination of the range of the arc radius at the root of the thread is made on the basis of the selected range of thread taper, on the basis of the relationship between the thread parameters and the number of tightening turns, while the number of tightening turns, the arc radius at the root of the thread, the half angle of the thread profile and the thread pitch must satisfy the following relationship:, where N is the number of tightening turns; - half the angle of the thread profile; tpr - thread taper; P - thread pitch; R is the radius of the arc at the base of the thread.

23. A torsion-resistant connection method for drill pipes according to claim 22, characterized in that the taper of the thread and the radius of the arc at the base of the thread must satisfy the following ratios: with a taper of 1 / 16, the radius of the arc is in the range of 0.05-0.065 inches; with a taper of 1 / 12, the radius of the arc is in the range of 0.04-0.06 inches; with a taper of 1 / 10, the radius of the arc is in the range of 0.045-0.055 inches.

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