Pipe string slip sleeve casing and drill pipe tensile test connecting device and test method

Abstract

The present application discloses a pipe string slip type casing and drill pipe tensile test connecting device, which comprises a load-down frame fixed on the ground, a plurality of hydraulic cylinders arranged on the load-down frame, the piston rod extension ends of the plurality of hydraulic cylinders being jointly connected with a load-up frame, the load-up frame and the load-down frame being respectively provided with an upper slip seat and a lower slip seat, the upper slip seat and the lower slip seat being the same structure and being arranged symmetrically, each of the upper slip seat and the lower slip seat being provided with a slip block, the slip block being provided with a slip block through hole in the center, and the hydraulic cylinders being further connected with a hydraulic system through hydraulic pipelines. The present application solves the problem that when the limit load is greater than the maximum load that the weld can bear, the weld connection will be broken, and the limit tensile load of the product cannot be tested. The present application also discloses a method for casing and drill pipe tensile test by the pipe string slip type casing and drill pipe tensile test connecting device.

Description

Technical Field

[0001] This invention belongs to the technical field of tensile testing equipment, and relates to a tensile testing connection device for tubing, casing, and drill pipe using a slip-type clamp. This invention also relates to a tensile testing method for tubing, casing, and drill pipe. Background Technology

[0002] In the oil and gas development field, casing and drill pipe inevitably bear significant axial tensile loads during use. To ensure their safety, it is necessary to test their ultimate tensile properties. With the deepening of oil and gas resource development and the continuous advancement towards deep and ultra-deep wells, the requirements for the tensile properties of casing and drill pipe are constantly increasing. Tensile performance testing of casing and drill pipe typically requires mounting them onto a corresponding load frame and welding them to the connecting plugs before conducting the tensile test. For high-strength casing and drill pipe, during ultimate load testing, when the ultimate load exceeds the maximum load that the weld can withstand, weld joint fracture may occur, making it impossible to test the product's ultimate tensile load. Therefore, a weld-free, full-size tensile testing device for casing and drill pipe is needed to ensure accurate and reliable acquisition of the ultimate tensile load during ultimate tensile testing. Summary of the Invention

[0003] The purpose of this invention is to provide a tubing slip type oil casing and drill pipe tensile test connection device, which solves the problem in the prior art that when the ultimate load is greater than the maximum load that the weld can withstand, the weld joint will break, and the ultimate tensile load of the product cannot be tested.

[0004] Another object of the present invention is to provide a method for performing tensile tests on oil casing and drill pipe using the above-mentioned tubing slip type oil casing and drill pipe tensile test connection device.

[0005] The technical solution adopted in this invention is a tubing slip type oil casing and drill pipe tensile test connection device, including a lower load frame fixed on the ground, multiple hydraulic cylinders are arranged on the lower load frame, the piston rod extension ends of the multiple hydraulic cylinders are connected to an upper load frame, an upper slip seat and a lower slip seat are respectively arranged on the upper load frame and the lower load frame, the upper slip seat and the lower slip seat have the same structure and are arranged symmetrically, a slip block is arranged in both the upper slip seat and the lower slip seat, and a slip block through hole is arranged in the center of the slip block, and the hydraulic cylinders are also connected to a hydraulic system through hydraulic pipelines.

[0006] The invention is further characterized in that: The upper load frame and the lower load frame are respectively provided with an upper platform and a lower platform integrated with the corresponding upper load frame and lower load frame. Multiple hydraulic cylinders are provided on the upper surface of the lower platform. The piston rods of the multiple hydraulic cylinders are connected to the lower surface of the upper platform. The upper slip seat and the lower slip seat are respectively fixed on the upper surface of the upper platform and the lower surface of the lower platform. The central axes of the upper platform, the lower platform, the upper slip seat, and the lower slip seat coincide.

[0007] Both the upper and lower clamping bases include clamping bases. The clamping bases of the upper and lower clamping bases are fixed to the upper surface of the upper platform and the lower surface of the lower platform, respectively. A clamping base body is fixedly connected to the side of the clamping base away from the upper or lower platform on which it is installed. The clamping base body and the clamping base are both aligned with the central axis of the upper and lower platforms. A frustum-shaped through hole is opened at the center of the clamping base body along its central axis. The diameter of the through hole gradually increases from the direction away from the clamping base. A frustum-shaped clamping block is provided at the end of the through hole away from the clamping base. The outer surface of the clamping block is parallel to the generatrix of the frustum on the inner surface of the clamping base body. The through hole of the clamping block at the center of the clamping block is coaxial with the through hole of the base body. The ends of the clamping block and the clamping base body away from the clamping base are located on the same horizontal plane and are connected to the upper clamping cap. The clamping base is also connected to the upper clamping cap by a long double-ended screw.

[0008] The slip block consists of multiple slip segments of the same size and structure, which are assembled into a hollow frustum-shaped slip block. The inner surface of each slip segment is set with a threaded surface, and each slip segment has a slip block screw hole at the end near the slip upper cover. The slip upper cover also has upper cover inner ring screw holes that correspond one-to-one with the slip block screw holes. The slip upper cover and the slip segments are fixedly connected by a pre-tightening auxiliary screw passing through the slip block screw holes and the upper cover inner ring screw holes. At this time, the diameter of the slip block through hole is 2mm larger than the smallest end of the base body through hole diameter. The smallest end of the base body through hole diameter is adapted to the outer diameter of the sample to be tested. The slip clamping bolt is also installed in the upper cover inner ring screw hole of the slip upper cover. The center of the slip upper cover also has an upper cover through hole, and the diameter of the smallest end of the upper cover through hole and the base body through hole is the same.

[0009] The clasp base has side holes at both ends. Positioning holes are provided on the upper surface of the upper platform and the lower surface of the lower platform at positions corresponding to the side holes. The clasp base is fixed to the corresponding upper and lower platforms by passing through the side holes and positioning holes with double-ended screws. The clasp base also has a through hole at its center. The through hole has the same minimum diameter as the through hole of the base body and is coaxial. The clasp base also has multiple ring-shaped screw holes around its center. The upper cover of the clasp has an outer ring screw hole at the position corresponding to the screw holes of the base. The clasp base and the upper cover of the clasp are fixedly connected by a long double-ended screw connecting the screw holes of the base and the outer ring screw hole of the upper cover. The center of the clasp base is set with an arc surface that protrudes from the side opposite to the upper cover of the clasp. The mating surface between the clasp base and the clasp body is set as an arc surface that mates with the arc surface of the clasp base.

[0010] The slip body is cylindrical. The inner inclined surface of the slip body through hole forms a 10° angle with the vertical direction. Multiple slip body screw holes are evenly arranged on one end face of the slip body near the slip upper cover. The slip upper cover is provided with a middle ring screw hole at the position corresponding to the slip body screw holes. The slip upper cover and the slip body are fixed by passing a short double-ended screw through the slip body screw hole and the middle ring screw hole of the upper cover, and then locked and fixed by the upper cover clamping bolt.

[0011] After inserting both ends of the test specimen into the corresponding through holes of the slip block, insert a liner core rod into the inner hole of both ends of the specimen. The length of the liner core rod is the same as the height of the slip block, and the outer diameter of the liner core rod is the outer diameter of the specimen minus the inner diameter. The end of the liner core rod away from the slip base is also connected to an extension section. The length of the extension section is at least 5 mm, and the outer diameter of the extension section is at least 2 mm larger than the inner diameter of the specimen.

[0012] The hydraulic cylinders are symmetrically arranged on opposite sides of the lower platform, and each hydraulic cylinder is equipped with a hydraulic valve on its connected hydraulic pipe.

[0013] The second technical solution adopted in this invention is a tensile testing method for oil casing and drill pipe, which uses the above-mentioned tubing slip-type oil casing and drill pipe tensile testing connection device, specifically as follows: In the initial state, each jaw segment is pre-tightened using a pre-tightening auxiliary screw on the jaw cap. Then, the sample is passed through the center of the upper and lower jaw seats from top to bottom, so that the lower end of the sample is flush with the bottom of the jaw block of the lower jaw seat. Then, the pre-tightening auxiliary screw of the lower jaw seat is removed, and the jaw clamping bolt is used to clamp the lower end of the sample with the jaw segment. Then, the hydraulic system is controlled to make the upper end of the sample flush with the top of the jaw block of the upper jaw seat. Then, the pre-tightening auxiliary screw of the upper jaw seat is removed, and the jaw clamping bolt is used to clamp the lower end of the sample with the jaw segment. Finally, the hydraulic system is controlled to extend the hydraulic cylinder to perform a tensile test.

[0014] After all the structures of the upper and lower clamping seats are securely fixed, insert the padding mandrel into both ends of the sample.

[0015] The beneficial effects of this invention are: This invention, through its mechanical structure and hydraulic system design, increases the tensile force, resulting in tighter and more reliable clamping. This effectively and stably clamps straight pipe sections, eliminating the need for welding and preventing the inability to test the tensile limits of high-strength oil casing and drill pipe due to welding quality issues. It also solves the problem of previous tensile limit limitations imposed by weld strength, enabling accurate and effective high-load ultimate tensile tests on large-size, high-strength steel-grade oil casing and drill pipe. Furthermore, this invention reduces welding processes, significantly improving testing efficiency, success rate, and data reliability. It provides strong support for the tensile performance testing of high-strength oil casing and drill pipe, laying an experimental foundation for the development of ultra-deep wells in my country. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the tubing slip type oil casing and drill pipe tensile test connection device of the present invention; Figure 2 This is a schematic diagram of the upper slip seat in the tubing slip type oil casing and drill pipe tensile test connection device of the present invention; Figure 3 This is a schematic diagram of the lower slip seat in the tubing string slip-type oil casing and drill pipe tensile test connection device of the present invention; Figure 4 This is a schematic diagram of the slip base in the tubing slip type oil casing and drill pipe tensile test connection device of the present invention; Figure 5 This is a schematic diagram of the slip block structure in the tubing slip type oil casing and drill pipe tensile test connection device of the present invention; Figure 6 This is a longitudinal cross-sectional view of the slip block in the tubing slip type oil casing and drill pipe tensile test connection device of the present invention; Figure 7 yes Figure 6 The left view; Figure 8 This is a schematic diagram of the structure of the pressure cap on the slip in the tubing slip type oil casing and drill pipe tensile test connection device of the present invention; Figure 9 This is a schematic diagram of the slip seat body in the tubing slip type oil casing and drill pipe tensile test connection device of the present invention; Figure 10 yes Figure 9 Top view.

[0017] In the diagram: 1. Upper load frame, 2. Hydraulic system, 3. Upper slip seat, 4. Lower slip seat, 5. Slip block, 5-1. Slip segment, 6. Pad mandrel, 7. Sample, 8. Slip seat body, 9. Slip base, 10. Upper pressure cap of slip, 11. Through hole of slip block, 12. Long double-ended screw, 13. Short double-ended screw, 14. Slip clamping bolt, 15. Upper pressure cap clamping bolt, 16. Screw hole of seat body, 17. Through hole of seat body, 18. Outer ring screw hole of upper pressure cap, 19. Middle ring screw hole of upper pressure cap, 20. Inner ring screw hole of upper pressure cap, 21. Through hole of upper pressure cap, 22. Screw hole of base, 23. Side hole of base, 24. Through hole of base, 25. Threaded surface, 26. Screw hole of slip block, 27. Hydraulic cylinder, 28. Positioning hole, 29. Upper platform, 30. Lower platform. Detailed Implementation

[0018] The following detailed description is provided in conjunction with specific implementation methods.

[0019] Example 1 The present invention relates to a slip-type oil casing and drill pipe tensile testing connection device, the structure of which is as follows: Figure 1 As shown, the system includes a lower load frame fixed on the ground, on which multiple hydraulic cylinders 27 are mounted. The piston rods of the multiple hydraulic cylinders 27 are connected to an upper load frame 1. The upper load frame 1 and the lower load frame are respectively provided with an upper slip seat 3 and a lower slip seat 4. The upper slip seat 3 and the lower slip seat 4 have the same structure and are arranged symmetrically. Both the upper slip seat 3 and the lower slip seat 4 are provided with slip blocks 5. The center of the slip block 5 is provided with a slip block through hole 11. The hydraulic cylinders 27 are also connected to a hydraulic system 2 through hydraulic pipes.

[0020] The working principle of this embodiment is as follows: The sample 7 is clamped by the upper and lower jaw blocks 5, and then the hydraulic cylinder 27 is extended by the hydraulic system 2 to carry out the tensile test.

[0021] Example 2 The present invention relates to a slip-type oil casing and drill pipe tensile testing connection device, the structure of which is as follows: Figure 1 As shown, the system includes a lower load frame fixed on the ground, on which multiple hydraulic cylinders 27 are mounted. The piston rods of the multiple hydraulic cylinders 27 are connected to an upper load frame 1. The upper load frame 1 and the lower load frame are respectively provided with an upper slip seat 3 and a lower slip seat 4. The upper slip seat 3 and the lower slip seat 4 have the same structure and are arranged symmetrically. Both the upper slip seat 3 and the lower slip seat 4 are provided with slip blocks 5. The center of the slip block 5 is provided with a slip block through hole 11. The hydraulic cylinders 27 are also connected to a hydraulic system 2 through hydraulic pipes.

[0022] The upper load frame and the lower load frame are respectively provided with an upper platform 29 and a lower platform 30 integrated with the corresponding upper load frame and lower load frame. The upper surface of the lower platform 30 is provided with multiple hydraulic cylinders 27. The piston rod extension ends of the multiple hydraulic cylinders 27 are connected to the lower surface of the upper platform 29. The upper slip seat 3 and the lower slip seat 4 are respectively fixed to the upper surface of the upper platform and the lower surface of the lower platform. The central axes of the upper platform 29, the lower platform 30, the upper slip seat 3, and the lower slip seat 4 coincide.

[0023] The working principle of this embodiment is as follows: The sample 7 is clamped by the upper and lower jaw blocks 5, and then the hydraulic cylinder 27 is extended by the hydraulic system 2 to carry out the tensile test.

[0024] Example 3 The present invention relates to a slip-type oil casing and drill pipe tensile testing connection device, the structure of which is as follows: Figure 1 As shown, the system includes a lower load frame fixed on the ground, on which multiple hydraulic cylinders 27 are mounted. The piston rods of the multiple hydraulic cylinders 27 are connected to an upper load frame 1. The upper load frame 1 and the lower load frame are respectively provided with an upper slip seat 3 and a lower slip seat 4. The upper slip seat 3 and the lower slip seat 4 have the same structure and are arranged symmetrically. Both the upper slip seat 3 and the lower slip seat 4 are provided with slip blocks 5. The center of the slip block 5 is provided with a slip block through hole 11. The hydraulic cylinders 27 are also connected to a hydraulic system 2 through hydraulic pipes.

[0025] The upper load frame and the lower load frame are respectively provided with an upper platform 29 and a lower platform 30 integrated with the corresponding upper load frame and lower load frame. The upper surface of the lower platform 30 is provided with multiple hydraulic cylinders 27. The piston rod extension ends of the multiple hydraulic cylinders 27 are connected to the lower surface of the upper platform 29. The upper slip seat 3 and the lower slip seat 4 are respectively fixed to the upper surface of the upper platform and the lower surface of the lower platform. The central axes of the upper platform 29, the lower platform 30, the upper slip seat 3, and the lower slip seat 4 coincide.

[0026] like Figure 2 and Figure 3As shown, both the upper locking seat 3 and the lower locking seat 4 include locking seat bases 9. The locking seat bases 9 of the upper locking seat 3 and the lower locking seat 4 are fixed to the upper surface of the upper platform 29 and the lower surface of the lower platform 30, respectively. A locking seat body 8 is fixedly connected to the side of the locking seat base 9 away from the upper platform 29 or the lower platform 30 on which it is installed. The locking seat body 8 and the locking seat base 9 are both coincident with the central axis of the upper platform 29 and the lower platform 30. A frustum-shaped seat through hole 17 is opened at the center of the locking seat body 8 along its central axis. The diameter of the seat through hole 17 is from near the center of the upper platform 29 to the lower platform 30. The direction away from the base 9 of the slip gradually increases. A frustum-shaped slip block 5 is provided at one end of the seat body through hole 17 away from the base 9. The outer surface of the slip block 5 is parallel to the generatrix of the frustum on the inner surface of the slip body 8. The slip block through hole 11 at the center of the slip block 5 is coaxial with the seat body through hole 17. The slip block 5 and the end of the slip body 8 away from the base 9 are located on the same horizontal plane and are connected together to the slip upper cover 10. The slip base 9 is also connected to the slip upper cover 10 by a long double-ended screw 12.

[0027] like Figure 5-7 As shown, the locking block 5 includes multiple locking segments 5-1 of the same size and structure. The locking segments 5-1 are assembled into a hollow frustum-shaped locking block 5. The inner surface of each locking segment 5-1 is set with a threaded surface 25, and each locking segment 5-1 is provided with a locking block screw hole 26 at one end near the locking cover 10; as Figure 8 As shown, the upper pressure cap 10 of the slip is cylindrical. The upper pressure cap 10 is also provided with an inner ring screw hole 20 that corresponds one-to-one with the screw hole 26 of the slip block. The upper pressure cap 10 and the slip block 5-1 are fixedly connected by a pre-tightening auxiliary screw passing through the screw hole 26 of the slip block and the inner ring screw hole 20 of the upper pressure cap. At this time, the diameter of the through hole 11 of the slip block is 2mm larger than the smallest end of the diameter of the through hole 17 of the seat body. The smallest end of the diameter of the through hole 17 of the seat body is adapted to the outer diameter of the sample 7 to be tested. The slip clamping bolt 14 is also installed in the inner ring screw hole 20 of the upper pressure cap of the slip 10. The upper pressure cap through hole 21 is also provided in the center of the upper pressure cap 10. The diameter of the upper pressure cap through hole 21 and the smallest end of the through hole 17 of the seat body are the same.

[0028] The working principle of this embodiment is as follows: The sample 7 is clamped by the upper and lower jaw blocks 5, and then the hydraulic cylinder 27 is extended by the hydraulic system 2 to carry out the tensile test.

[0029] When the slip block 5 is pre-tightened using the pre-tightening auxiliary screw, the diameter of the through hole 11 of the slip block is the outer diameter of the test sample 7 plus 2mm, and the inner surface is a threaded surface, which facilitates increasing friction to clamp the sample.

[0030] After the sample is placed below, remove the pre-tightening auxiliary screw, and then pass the clamping bolt 14 through the inner ring screw hole 20 of the upper pressure cover. Under the action of the clamping bolt 14, the clamping block 5-1 moves towards the small end of the through hole 17 of the seat body until the sample 7 can no longer be tightened by clamping the clamping bolt 14, thus completing the clamping of the sample 7 by the clamping block 5-1.

[0031] Example 4 Based on Example 3, such as Figure 4 As shown, the slip base 9 has base side holes 23 at both ends. Positioning holes 28 are provided on the upper surface of the upper platform 29 and the lower surface of the lower platform 30 at positions corresponding to the base side holes 23. The slip base 9 is fixed to the corresponding upper platform 29 and lower platform 30 by double-ended screws passing through the base side holes 23 and positioning holes 28. A base through hole 24 is also provided in the center of the slip base 9. The base through hole 24 has the same diameter as the smallest end of the base through hole 17 and is coaxial. Multiple bases arranged in a ring around the center of the slip base 9 are also provided. The screw hole 22 and the upper pressure cap 10 of the slip are provided with an outer ring screw hole 18 at the position corresponding to the screw hole 22 of the base. The slip base 9 and the upper pressure cap 10 are fixedly connected by a long double-ended screw. The center position of the slip base 9 is set with an arc surface that protrudes from the side opposite to the upper pressure cap 10. The mating surface of the slip body 8 and the slip base 9 is set as an arc surface that matches the arc surface of the slip base 9. The two mating arc surfaces facilitate the fit of the slip body 8 and the slip base 9.

[0032] like Figures 9-10 As shown, the slip seat 8 is cylindrical. The inner inclined surface of the slip seat through hole 17 is at a 10° angle to the vertical direction. Multiple slip screw holes 16 are evenly arranged on one end face of the slip seat 8 near the slip upper cover 10. The slip upper cover 10 is provided with an upper cover middle ring screw hole 19 at the position corresponding to the slip screw hole 16. The slip upper cover 10 and the slip seat 8 are locked and fixed by a short double-ended screw 13 passing through the slip screw hole 16 and the upper cover middle ring screw hole 19, and then by the upper cover clamping bolt 15.

[0033] Example 5 Based on Example 4, after inserting both ends of the test specimen 7 into the corresponding through holes 11 of the slip block, a padding core rod 6 is inserted into the inner holes of both ends of the specimen 7. The length of the padding core rod 6 is the same as the height of the slip block 5, and the outer diameter of the padding core rod 6 is the outer diameter of the specimen 7 minus the inner diameter, just enough to fit inside the test specimen. This prevents the specimen from being flattened and slipping off due to excessive holding force during the stretching process. The end of the padding core rod 6 away from the slip base 9 is also connected to an extension section. The length of the extension section is at least 5 mm, and the outer diameter of the extension section is at least 2 mm larger than the inner diameter of the specimen 7, ensuring that it does not fall into the specimen after being inserted from the top. The padding core rod of this invention is made of aluminum alloy. The padding core rod can effectively prevent the specimen 7 from being flattened and slipping off due to excessive holding force during the stretching process. The addition of the padding core rod will not cause excessive deformation of the test specimen and slippage. The padding core rod only needs to be inserted into the specimen 7 without falling out. The main purpose is to prevent the clamping force from causing excessive deformation of the specimen.

[0034] The hydraulic cylinders 27 are symmetrically arranged on the corresponding sides of the lower platform 30. Each hydraulic cylinder 27 is connected to a hydraulic pipe and is equipped with a hydraulic valve. Four hydraulic cylinders 27 are fixed on each side. By controlling the opening and closing of the hydraulic valves, the switching between eight cylinders and four cylinders can be achieved. When a small load is required, the four inner cylinders are closed to improve the control accuracy under small load. When a large load is required, the four inner cylinders are opened to achieve eight-cylinder operation and increase the maximum load of the entire system.

[0035] Example 6 Based on Example 5, the slip seat 8 is forged from 42CrMo material and then tempered by HB217~235. The upper cover 10 of the slip, the slip base 9, the double-ended screw and the bolt are all forged from 42CrMo material and then tempered by HB235~275. The slip blocks are forged from 34CrNi3MoV material, and the quenching and tempering treatment is HB260-290. After machining, they are nitrided or carburized to ensure that the hardness of the toothed surface of the slip block is HRc58.

[0036] Example 7 The tensile testing method for oil casing and drill pipe of the present invention adopts the tubing slip type oil casing and drill pipe tensile testing connection device in Example 5, specifically as follows: In the initial state, each clamping block 5-1 is pre-tightened on the clamping cover 10 using a pre-tightening auxiliary screw. Then, the sample 7 is passed through the center of the upper clamping block 3 and the lower clamping block 4 from top to bottom, so that the lower end of the sample 7 is flush with the bottom of the clamping block 5 of the lower clamping block 4. Then, the pre-tightening auxiliary screw of the lower clamping block 4 is removed, and the clamping block 14 is used to clamp the lower end of the sample 7 with the clamping block 5-1. Then, the hydraulic system 2 is controlled to make the upper end of the sample 7 flush with the top of the clamping block 5 of the upper clamping block 3. Then, the pre-tightening auxiliary screw of the upper clamping block 3 is removed, and the clamping block 14 is used to clamp the lower end of the sample 7 with the clamping block 5-1. Finally, the hydraulic system 2 is controlled to extend the hydraulic cylinder 27 to perform a tensile test.

[0037] After all the structures of the upper and lower clamping seats 3 and 4 are securely fixed, insert the padding core rod 6 into both ends of the sample 7.

[0038] Example 8 Based on Example 7, each slip block 5 in this example includes four slip blocks 5-1; the outer ring screw hole 18, the middle ring screw hole 19, and the inner ring screw hole 20 of the upper cover are all arranged around the center of the upper cover 10 of the slip block, and the base screw hole 22 is distributed around the center of the slip block base 9.

[0039] Based on this, the tensile test shall be conducted according to the following steps: Step 1: Place the clasp base 9 on a horizontal surface, and fit the curved surface of the clasp body 8 and the curved surface of the clasp base 9 tightly together, placing it on the clasp base 9; Step 2: Place the four jaw blocks 5-1 with the jaw block screw holes 26 on one side, and press them against the corresponding side of the upper jaw cover 10 of the upper jaw seat 3 or lower jaw seat 4. At the same time, ensure that the jaw block screw holes 26 are aligned with the inner ring screw holes 20 of the upper cover. Use the pre-tightening auxiliary screw to pre-tighten and fix each jaw block 5-1 to ensure that the jaw block 5-1 does not fall off. At this time, the diameter of the through hole 11 of the jaw block is 2mm larger than the smallest end of the diameter of the through hole 17 of the seat body. Step 3: Place the upper pressure cap 10 of the slip on top of the slip base 8, ensuring that the geometric center lines of the slip base 9, the slip base 8, and the upper pressure cap 10 of the slip coincide. Step 3: Rotate the upper pressure cap 10 of the slip to align the screw hole 19 in the middle ring of the upper pressure cap with the screw hole 16 on the slip body 8. Then insert 8 short double-ended screws 13 and tighten them. Then, put 8 upper pressure cap clamping bolts 15 on top and tighten them to ensure that the upper pressure cap 10 of the slip is tightly fixed to the slip body 8. Step 4: Rotate the upper pressure cap 10 of the clamping plate and the clamping plate body 8 together to ensure that the screw holes 18 on the outer ring of the upper pressure cap correspond one-to-one with the screw holes 22 on the base. Then, insert 8 long double-ended screws 12 and tighten them. Then, put 8 bolts on top and tighten them to ensure that the upper pressure cap 10 of the clamping plate is firmly fixed to the clamping plate body 8 and the clamping plate base 9, thus completing the installation of the upper clamping plate body 3 and the lower clamping plate body 4. Step 5: Use an auxiliary tool to place the lower clamping seat 4 at the lower end of the lower load frame, while ensuring that the base side hole 23 of the clamping seat base 9 of the lower clamping seat corresponds one-to-one with the positioning hole 28 on the lower surface of the lower platform 30, and use a double-ended screw to fix the clamping seat base 9 to the lower platform 30. Step 6: Hoist the pre-assembled upper clamping seat 3 to the upper load frame, while ensuring that the base side hole 23 of the corresponding lower clamping seat's clamping base 9 corresponds one-to-one with the positioning hole 28 on the lower surface of the lower platform 30, and use double-ended screws to fix the clamping base 9 to the lower platform 30. Step 7: Insert the sample 7 through each central through hole from top to bottom until the lower end of the sample is flush with the bottom of the slip block 5 of the lower slip seat 4. Then, remove the pre-tightening auxiliary screws on the lower slip seat 4 one by one. Then, insert the slip clamping bolt 14 through the screw hole 20 of the inner ring of the upper pressure cover. Each slip clamping bolt 14 clamps the corresponding slip block 5-1 and slides it upward along the inclined surface of the frustum until the four slip blocks 5-1 clamp the sample 7 and the slip blocks 5-1 can no longer move. Tighten the slip clamping bolt 14 to complete the clamping of the lower end of the sample 7. Then, insert the prepared pad mandrel into the inner hole of the oil casing or drill rod at the lower end of the sample and fix it to ensure that it does not fall off. Step 8: Adjust the extension height of the piston rod of the hydraulic cylinder 27 by controlling the hydraulic system so that the adjustment is completed when the upper end of the sample 7 is flush with the upper end of the slip block 5 of the upper slip seat 3. Then, turn off the hydraulic system. Step 9: Loosen the pre-tightening auxiliary screw on the upper slip seat 3, then the slip block 5-1 in the upper slip seat 3 is inclined downwards, and then the slip clamping bolt 14 is inserted through the screw hole 20 of the inner ring of the upper pressure cover until the slip clamping bolt 14 is tightened to complete the clamping of the upper end of the sample 7. Then, insert the pre-prepared pad core rod with increased wall thickness at one end into the oil sleeve or drill rod inner hole at the upper end of the sample. Step 10: Then, the upper load frame is raised by the hydraulic system, thereby increasing the tensile load. During the stretching process, the friction between the clamping blocks and the sample causes the clamping blocks to tend to move towards the center (the upper clamping block tends to move downwards, and the lower clamping block tends to move upwards). Meanwhile, the inner diameter of the clamping block 8 decreases towards the center (the inner diameter of the upper clamping block decreases downwards, and the inner diameter of the lower clamping block decreases upwards). Therefore, it will become tighter and tighter, preventing slippage. Thus, after stretching, the space between the clamping block 5 and the clamping block 8 becomes smaller and smaller, tightly clamping the sample 7 to ensure that it does not slip during the test. When removing the clamping block, the upper load frame is lowered, and the space between the clamping block and the clamping block 8 becomes larger and larger (the opposite of the stretching process). After relaxation, it can be disassembled.

Claims

1. A slip-type oil casing and drill pipe tensile test connection device, characterized in that, The system includes a lower load frame fixed on the ground, on which multiple hydraulic cylinders (27) are installed. The piston rods of the multiple hydraulic cylinders (27) are connected to an upper load frame (1). The upper load frame (1) and the lower load frame are respectively provided with an upper slip seat (3) and a lower slip seat (4). The upper slip seat (3) and the lower slip seat (4) have the same structure and are arranged symmetrically. Slip blocks (5) are provided in both the upper slip seat (3) and the lower slip seat (4). A slip block through hole (11) is provided in the center of the slip block (5). The hydraulic cylinders (27) are also connected to a hydraulic system (2) through hydraulic pipes.

2. The tubing slip type oil casing and drill pipe tensile test connection device according to claim 1, characterized in that, The upper load frame and the lower load frame are respectively provided with an upper platform (29) and a lower platform (30) integrally formed with the corresponding upper load frame and lower load frame. The upper surface of the lower platform (30) is provided with multiple hydraulic cylinders (27). The piston rods of the multiple hydraulic cylinders (27) are connected to the lower surface of the upper platform (29). The upper slip seat (3) and the lower slip seat (4) are respectively fixed on the upper surface of the upper platform and the lower surface of the lower platform. The central axes of the upper platform (29), the lower platform (30), the upper slip seat (3), and the lower slip seat (4) coincide.

3. The tubing string slip-type oil casing and drill pipe tensile test connection device according to claim 2, characterized in that, Both the upper and lower locking plates include locking bases (9). The locking bases (9) of the upper and lower locking plates (3 and 4) are fixed to the upper surface of the upper platform (29) and the lower surface of the lower platform (30), respectively. A locking plate body (8) is fixedly connected to the side of the locking base (9) away from the upper platform (29) or lower platform (30) to which it is installed. The locking plate body (8) and the locking base (9) are both aligned with the central axis of the upper platform (29) and the lower platform (30). A frustum-shaped seat through hole (17) is opened at the center of the locking plate body (8) along its central axis. The diameter of the seat through hole (17) is from near the center of the upper platform (29) to the lower platform (30). The direction away from the base (9) of the slip base gradually increases. A frustum-shaped slip block (5) is provided at one end of the seat body through hole (17) away from the slip base (9). The outer surface of the slip block (5) is parallel to the generatrix of the frustum on the inner surface of the slip body (8). The slip block through hole (11) at the center of the slip block (5) is coaxial with the seat body through hole (17). The slip block (5) and the slip body (8) at one end away from the slip base (9) are located on the same horizontal plane and are connected together to the slip upper cover (10). The slip base (9) is also connected to the slip upper cover (10) by a long double-ended screw (12).

4. The tubing slip type oil casing and drill pipe tensile test connection device according to claim 3, characterized in that, The slip block (5) includes multiple slip segments (5-1) of the same size and structure. The slip segments (5-1) are assembled into a hollow frustum-shaped slip block (5). The inner surface of each slip segment (5-1) is set with a threaded surface (25). Each slip segment (5-1) has a slip block screw hole (26) at one end near the slip upper cover (10). The slip upper cover (10) is also provided with an inner ring screw hole (20) that corresponds one-to-one with the slip block screw hole (26). The slip upper cover (10) and the slip segments (5-1) are pre-connected. The auxiliary screw is fixedly connected through the screw hole (26) of the slip block and the screw hole (20) of the inner ring of the upper pressure cover. At this time, the diameter of the through hole (11) of the slip block is 2mm larger than the smallest end of the diameter of the through hole (17) of the seat body. The smallest end of the diameter of the through hole (17) of the seat body is adapted to the outer diameter of the sample (7) to be tested. The slip clamping bolt (14) is also installed in the screw hole (20) of the inner ring of the upper pressure cover (10) of the slip block. The upper pressure cover (10) is also provided with an upper pressure cover through hole (21) in the center. The diameter of the smallest end of the upper pressure cover through hole (21) and the through hole (17) of the seat body is the same.

5. The tubing string slip-type oil casing and drill pipe tensile test connection device according to claim 4, characterized in that, The locking base (9) has base side holes (23) at both ends. The upper surface of the upper platform (29) and the lower surface of the lower platform (30) are provided with positioning holes (28) at the positions corresponding to the base side holes (23). The locking base (9) is fixed to the corresponding upper platform (29) and lower platform (30) by passing through the base side holes (23) and positioning holes (28) with double-ended screws. The locking base (9) also has a base through hole (24) at its center. The base through hole (24) has the same diameter as the smallest end of the seat through hole (17) and is coaxial. The locking base (9) is centered around the base through hole (24). The center is also provided with a number of base screw holes (22) arranged in a ring. The upper cover (10) of the slip is provided with an outer ring screw hole (18) corresponding to the base screw hole (22). The slip base (9) and the slip upper cover (10) are fixedly connected by a long double-headed screw connecting the base screw hole (22) and the upper cover outer ring screw hole (18). The center of the slip base (9) is provided with an arc surface that protrudes from the side opposite to the slip upper cover (10). The mating surface of the slip body (8) and the slip base (9) is provided with an arc surface that mates with the arc surface of the slip base (9).

6. The tubing string slip-type oil casing and drill pipe tensile test connection device according to claim 5, characterized in that, The slip seat (8) is cylindrical. The inner inclined surface of the slip seat through hole (17) is at a 10° angle to the vertical direction. The slip seat (8) has a plurality of seat screw holes (16) evenly arranged on one end face near the slip upper cover (10). The slip upper cover (10) has an upper cover middle ring screw hole (19) at the position corresponding to the seat screw hole (16). The slip upper cover (10) and the slip seat (8) are locked and fixed by the upper cover clamping bolt (15) after the short double-ended screw (13) passes through the seat screw hole (16) and the upper cover middle ring screw hole (19).

7. The tubing string slip-type oil casing and drill pipe tensile test connection device according to claim 6, characterized in that, After inserting both ends of the test specimen (7) into the corresponding through hole (11) of the slip block, insert a pad core rod (6) into the inner hole of both ends of the test specimen (7). The length of the pad core rod (6) is the same as the height of the slip block (5). The outer diameter of the pad core rod (6) is the outer diameter of the test specimen (7) minus the inner diameter. The end of the pad core rod (6) away from the slip base (9) is also connected to an extension section. The length of the extension section is at least 5 mm. The outer diameter of the extension section is at least 2 mm larger than the inner diameter of the test specimen (7).

8. The tubing slip type oil casing and drill pipe tensile test connection device according to claim 7, characterized in that, The hydraulic cylinders (27) are symmetrically arranged on the corresponding sides of the lower platform (30), and each hydraulic cylinder (27) is equipped with a hydraulic valve on the hydraulic pipe connected to it.

9. A tensile test method for oil casing and drill pipe, characterized in that, The tubing slip type oil casing and drill pipe tensile test connection device as described in claim 8 is specifically as follows: In the initial state, each clamping block (5-1) is pre-tightened on the clamping cover (10) using a pre-tightening auxiliary screw. Then, the sample (7) passes through the center of the upper clamping seat (3) and the lower clamping seat (4) from top to bottom, so that the lower end of the sample (7) is flush with the bottom of the clamping block (5) of the lower clamping seat (4). Then, the pre-tightening auxiliary screw of the lower clamping seat (4) is removed, and the clamping bolt (14) is used to clamp the lower end of the sample (7) with the clamping block (5-1). Then, the hydraulic system (2) is controlled to make the upper end of the sample (7) flush with the top of the clamping block (5) of the upper clamping seat (3). Then, the pre-tightening auxiliary screw of the upper clamping seat (3) is removed, and the clamping bolt (14) is used to clamp the lower end of the sample (7) with the clamping block (5-1). Then, the hydraulic system (2) is controlled to make the hydraulic cylinder (27) extend to perform a tensile test.

10. The tensile test method for oil casing and drill pipe according to claim 9, characterized in that, After all the structures of the upper clamp seat (3) and the lower clamp seat (4) are fixed tightly, the pad core rod (6) is inserted into both ends of the sample (7).

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