A high fatigue resistant drill tool joint and method of machining the same

Abstract

The application discloses a high fatigue resistance drill tool joint and a processing method thereof. The high fatigue resistance drill tool joint comprises male and female joints with the same inner and outer diameters, the female joint is provided with a female joint main shoulder, a female joint thread and a female joint auxiliary shoulder, the female joint thread comprises normal female thread teeth and the first three special female thread teeth close to the female joint main shoulder, the normal female thread tooth bearing surface tooth type angle β is 25-45°, and the angle difference α between the special female thread bearing surface and the normal female thread tooth bearing surface is 0.1-5°; the male joint is provided with a male joint main shoulder, a male joint thread and a male joint auxiliary shoulder, the male joint thread comprises normal male thread teeth and the first three special male thread teeth close to the male joint auxiliary shoulder, the normal male thread tooth bearing surface tooth type angle β is 25-45°, and the angle difference α between the special male thread bearing surface and the normal male thread tooth bearing surface is 0.1-5°. After the male and female joints of the application are combined by applying torque and screwing, the joint thread tooth bottom stress extreme value can be remarkably reduced, and the stress distribution of the whole joint thread section is relatively uniform.

Description

TECHNICAL FIELD

[0001] The present application relates to an oil well pipe string tool used in the process of oil and gas exploration and development, and particularly relates to a high fatigue resistance drill tool joint suitable for oil and gas exploration of ultra-deep wells, curved wells and extended reach wells and a processing method thereof. BACKGROUND

[0002] The oil well pipe string tool mentioned herein includes oil casing, tubing and drill string components (kelly, drill pipe, heavy wall drill pipe, drill collar, swivel joint and the like).

[0003] The oil and gas drilling industry has been breaking through the existing drilling limit, and the number and depth record of drilling under special working conditions are constantly being refreshed. The breakthrough of the drilling limit requires higher and higher technical quality of oil drilling tools. In order to meet the drilling technical requirements, in the development of drill string joint thread technology, the designer reasonably increases an inner shoulder structure on the basis of the API drill tool joint single shoulder structure, optimizes the thread taper, pitch and the like, and develops a high torsion resistance, ultra-high torsion resistance drill tool joint, the torsion resistance of which is increased by more than 70% than that of the API drill tool joint.

[0004] With a substantial increase in the applied torque, the corresponding local stress concentration of the thread teeth is more and more obvious. In use, early fatigue cracks often occur at the local thread teeth of the joint, and even fatigue cracks lead to rapid leakage and fracture, which brings huge economic losses to the oil field. The stress on each thread tooth of the existing drill tool joint under complex load conditions presents the characteristics that the stress of the thread teeth at both ends is large and the stress of the thread teeth in the middle section is small. This unreasonable stress distribution makes the potential of the thread teeth in the middle section not fully developed, and the thread teeth at both ends are prematurely fatigued. SUMMARY

[0005] The purpose of the present application is to provide a high fatigue resistance drill tool joint and a processing method thereof, which mainly solves the defects of the prior art. Compared with the thread structure of the existing oil drilling tool joint, a special thread tooth structure is designed in the high stress area at both ends of the thread, and after the male joint and the female joint are applied with torque and are coupled, the stress extreme value of the thread tooth bottom of the joint can be significantly reduced, the stress distribution of the entire joint thread section is relatively uniform, the joint has very good fatigue resistance in the process of rotary drilling in harsh well conditions such as ultra-deep wells, curved well sections or extended reach wells, and the service life of the drill string can be greatly improved.

[0006] To achieve the above purpose, the technical scheme of the present application is as follows:

[0007] A high fatigue resistance drilling tool joint, comprising a box and a pin, characterized in that the box is provided with a box main shoulder, a box thread and a box sub shoulder, the box thread comprises normal box thread teeth and the first three special box thread teeth close to the box main shoulder, the normal box thread tooth bearing surface has a tooth angle β of 25-45°, the special box thread tooth bearing surface has an angle difference α of 0.1-5° with the normal box thread tooth bearing surface, and the special box thread tooth bearing surface has a tooth angle of β-α.

[0008] The pin is provided with a pin main shoulder, a pin thread and a pin sub shoulder, the pin thread comprises normal pin thread teeth and the first three special pin thread teeth close to the pin sub shoulder, the normal pin thread tooth bearing surface has a tooth angle β of 25-45°, the special pin thread tooth bearing surface has an angle difference α of 0.1-5° with the normal pin thread tooth bearing surface, and the special pin thread tooth bearing surface has a tooth angle of β-α.

[0009] The high fatigue resistance drilling tool joint is characterized in that the box thread taper and the pin thread taper range from 1:3 to 1:32.

[0010] The high fatigue resistance drilling tool joint is characterized in that the box thread lead and the pin thread lead range from 4.23 mm to 12.7 mm.

[0011] The high fatigue resistance drilling tool joint is characterized in that the box and the pin are made of steel or titanium alloy or aluminum alloy.

[0012] A machining method of the high fatigue resistance drilling tool joint, characterized in that during machining of the box thread, normal box thread cutters are used to machine all the thread teeth, and special box thread cutters are used to machine the first three special box thread teeth close to the box main shoulder.

[0013] During machining of the pin thread, normal pin thread cutters are used to machine all the thread teeth, and special pin thread cutters are used to machine the first three special pin thread teeth close to the pin sub shoulder.

[0014] Compared with the prior art, the present application has the following outstanding advantages: in the box thread section of the present application, the first three thread teeth close to the main shoulder of the box are special box thread teeth, in the pin thread section, the first three thread teeth close to the secondary shoulder of the pin are special pin thread teeth, when the pin and the box are applied with torque to make up, there is a certain gap between the special box thread tooth area and the corresponding pin regular thread tooth, and there is a certain gap between the special pin thread tooth area and the corresponding box regular thread, the gaps in the two places relieve the high stress in the corresponding area due to large deformation, can significantly reduce the stress extreme value of the thread tooth bottom of the two ends of the joint, increase the stress in the middle section of the thread, make the stress distribution of the whole joint thread section more uniform, and further ensure that the petroleum drilling tool has very good fatigue resistance in the rotary drilling process in harsh well conditions such as ultra-deep well, curved well section or large displacement well. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is a schematic diagram of the pin and the box of the present application being made up.

[0016] Figure 2 It is a local area A in the schematic diagram of the pin and the box of the present application being made up.

[0017] Figure 3 It is a local area B in the schematic diagram of the pin and the box of the present application being made up.

[0018] Figure 4 It is a schematic diagram of a regular box thread tooth structure.

[0019] Figure 5 It is a schematic diagram of a regular pin thread tooth structure.

[0020] Figure 6 It is a schematic diagram of a special box thread tooth structure of the present application.

[0021] Figure 7 It is a schematic diagram of a special pin thread tooth structure of the present application.

[0022] Figure 8 It is a schematic diagram of the superposition of the regular box thread tooth and the special box thread tooth.

[0023] Figure 9 It is a schematic diagram of the superposition of the regular pin thread tooth and the special pin thread tooth.

[0024] Figure 10 It is a stress distribution trend chart of each thread of the box of the joint in the finite element numerical simulation analysis of the example and the comparative example.

[0025] Figure 11 It is a stress distribution trend chart of each thread of the pin of the joint in the finite element numerical simulation analysis of the example and the comparative example.

[0026] Figure: 1-female joint; 11-main shoulder of female joint; 12-female joint thread; 121-regular female thread; 1211-regular female thread load bearing surface; 1212-regular female thread crest; 1213-regular female thread guide surface; 1214-regular female thread root; 122-special female thread; 1221-special female thread load bearing surface; 1222-special female thread crest; 1223-special female thread guide surface; 1224-special female thread root; 13-secondary shoulder of female joint; 2-male joint; 21-main shoulder of male joint; 22-male joint thread; 221-regular male thread; 2211-regular male thread guide surface; 2212-regular male thread root; 2213-regular male thread load bearing surface; 2214-regular male thread crest; 222-special male thread; 2221-special male thread guide surface; 2222-special male thread root; 2223-special male thread load bearing surface; 2224-special male thread crest; 23-secondary shoulder of male joint; a~k-male joint thread; l~u-female joint thread; wherein a, b and c are the first three special male threads close to the secondary shoulder of male joint; l, m and n are the first three special female threads close to the main shoulder of female joint. DETAILED DESCRIPTION

[0027] Reference Figures 1-9 The present application discloses a high fatigue resistance drill joint. As shown in the figure: including the female joint 1 and the male joint 2 with the same inner and outer diameter, the female joint 1 is provided with the main shoulder 11 of female joint, the female joint thread 12 and the secondary shoulder 13 of female joint, the female joint thread includes the regular female thread 121 and the first three special female threads 122 close to the main shoulder 13 of female joint, the thread angle β of the regular female thread load bearing surface 1211 is 25°~45°, the angle difference α between the special female thread load bearing surface 1221 and the regular female thread load bearing surface 1211 is 0.1°~5°, and the thread angle of the special female thread load bearing surface 1221 is β-α; the male joint 2 is provided with the main shoulder 21 of male joint, the male joint thread 22 and the secondary shoulder 23 of male joint, the male joint thread includes the regular male thread 221 and the first three special male threads 222 close to the secondary shoulder 23 of male joint, the thread angle β of the regular male thread load bearing surface 2213 is 25°~45°, the angle difference α between the special male thread load bearing surface 2223 and the regular male thread load bearing surface 2213 is 0.1°~5°, and the thread angle of the special male thread load bearing surface 2223 is β-α.

[0028] In the present application, the taper of the female joint thread 12 and the taper of the male joint thread 22 range from 1:3 to 1:32.

[0029] In the present application, the lead of the female joint thread 12 and the lead of the male joint thread 22 range from 4.23mm to 12.7mm.

[0030] In the present application, the material of the box 12 and pin 22 is steel or titanium alloy or aluminum alloy.

[0031] A method for machining the high fatigue resistance drill tool joint as described above, during machining of the box thread 12, first machining all thread teeth with a conventional box thread tool, and then machining the first three special box thread teeth 122 close to the box shoulder 13 with a special box thread tool.

[0032] During machining of the pin thread 22, first machining all thread teeth with a conventional pin thread tool, and then machining the first three special pin thread teeth 222 close to the pin shoulder 23 with a special pin thread tool. Embodiment

[0033] A double shoulder steel drill pipe joint with a steel grade of 120 ksi, an outer diameter of 127.0 mm, and an inner diameter of 65.09 mm is selected, as shown in Figures 1-9 The high fatigue resistance oil drill tool joint and the machining method thereof include a box 1 and a pin 2 with the same inner and outer diameters.

[0034] The box 1 is provided with a box shoulder 11, a box thread 12, and a box shoulder 13. The box thread includes conventional box thread teeth 121 and the first three special box thread teeth 122 close to the box shoulder 13. The thread angle β of the conventional box thread tooth bearing surface 1211 is 30°, and the angle difference α between the special box thread bearing surface 1221 and the conventional box thread tooth bearing surface 1211 is 2°.

[0035] The pin 2 is provided with a pin shoulder 21, a pin thread 22, and a pin shoulder 23. The pin thread includes conventional pin thread teeth 221 and the first three special pin thread teeth 222 close to the pin shoulder 23. The thread angle β of the conventional pin thread tooth bearing surface 2213 is 30°, and the angle difference α between the special pin thread bearing surface 2223 and the conventional pin thread tooth bearing surface 2213 is 2°.

[0036] During machining of the box thread 12, first machining all thread teeth with a conventional box thread tool, and then machining the first three special box thread teeth 122 close to the box shoulder 13 with a special box thread tool.

[0037] During machining of the pin thread 22, first machining all thread teeth with a conventional pin thread tool, and then machining the first three special pin thread teeth 222 close to the pin shoulder 23 with a special pin thread tool.

[0038] The taper of the box thread 12 and the taper of the pin thread 22 are 1:16.

[0039] The pitch of the box thread 12 and the pin thread 22 ranges from 7.26 mm;

[0040] A torque of 30600 N•m is applied to the joint, and the stress values of the threads of the box and pin are analyzed by finite element numerical simulation.

[0041] Comparative Example

[0042] A double shoulder steel drill pipe joint with a steel grade of 120 ksi, an outer diameter of 127.0 mm, and an inner diameter of 65.09 mm is selected, which includes a box 1 and a pin 2 with the same inner and outer diameters.

[0043] The box 1 is provided with a box main shoulder 11, a box thread 12, and a box secondary shoulder 13, and the box thread is a conventional box thread 121;

[0044] The pin 2 is provided with a pin main shoulder 21, a pin thread 22, and a pin secondary shoulder 23, and the pin thread includes a conventional pin thread 221;

[0045] The taper of the box thread 12 and the pin thread 22 is 1:16;

[0046] The pitch of the box thread 12 and the pin thread 22 ranges from 7.26 mm;

[0047] A torque of 30600 N•m is applied to the joint, and the stress values of the threads of the box and pin are analyzed by finite element numerical simulation.

[0048] The results of the finite element numerical simulation analysis of the joint of the example and the joint of the comparative example are compared, as shown in Figure 10 As shown, the stress values at both ends of the box are significantly reduced, the stress values of the middle thread segment are slightly increased, and the overall stress distribution is more optimal by using the joint thread structure technology of the present application; as shown in Figure 11 As shown, the stress values of the jth and kth threads of the pin are higher than the yield strength of the joint material, and local plastic deformation occurs, which has a hidden danger, while the stress values at both ends of the pin are reduced, the stress values of the middle thread segment are increased, and the overall stress distribution is more optimal by using the joint thread structure technology of the present application.

[0049] The above only describes preferred embodiments of the present application and is not intended to limit the scope of the present application. Any equivalent changes and modifications made within the scope of the present application should be within the technical scope of the present application.

Claims

1. A method for machining a high fatigue resistant drill tool joint comprising a box (1) and a pin (2) having the same inner and outer diameters, characterized in that: The female connector (1) is provided with a female connector main shoulder (11), a female connector thread (12) and a female connector secondary shoulder (13). The female connector thread includes a conventional female thread tooth (121) and three special female thread teeth (122) near the female connector main shoulder (11). The tooth profile angle β of the conventional female thread tooth bearing surface (1211) is 25° to 45°. The angle difference α between the special female thread tooth bearing surface (1221) and the conventional female thread tooth bearing surface (1211) is 0.1° to 5°. The tooth profile angle of the special female thread tooth bearing surface (1221) is β-α. The male connector (2) is provided with a male connector main shoulder (21), a male connector thread (22) and a male connector secondary shoulder (23). The male connector thread includes a conventional male thread (221) and three special male thread (222) near the male connector secondary shoulder (23). The tooth profile angle β of the conventional male thread bearing surface (2213) is 25° to 45°. The angle difference α between the special male thread bearing surface (2223) and the conventional male thread bearing surface (2213) is 0.1° to 5°. The tooth profile angle of the special male thread bearing surface (2223) is β-α. During the machining process of the female connector thread (12), all the thread teeth are first machined with a conventional female thread cutting tool, and then the first three special female thread teeth (122) near the main shoulder (11) of the female connector are machined with a special female thread cutting tool. During the machining process of the male connector thread (22), all the thread teeth are first machined with a conventional male thread cutting tool, and then the first three special male thread teeth (222) near the male connector secondary shoulder (23) are machined with a special male thread cutting tool.

2. The method of claim 1, wherein: The taper range of the female connector thread (12) and the male connector thread (22) is 1:3 to 1:

32.

3. The method of claim 1 wherein: The lead of the female connector thread (12) and the lead of the male connector thread (22) range from 4.23 mm to 12.7 mm.

4. The method of claim 1 wherein: The materials of the female connector (1) and the male connector (2) are steel, titanium alloy, or aluminum alloy.

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