A torsional fatigue testing apparatus simulating downhole combined load conditions of an oil string

Abstract

The present application relates to the technical field of oil exploitation, and more particularly to a kind of torsional fatigue test equipment for simulating downhole composite load conditions of oil string, comprising connecting block one;Bottom plate and slide plate are all fixedly connected with a connecting block one;Each connecting block one is fixedly connected with a circular ring one;Each circular ring one is rotatably connected with a cylinder one;Each cylinder one is rotatably connected with a cylinder two;Each circular ring one is fixedly connected with a circular ring two;All circular ring ones are jointly inserted with composite pipe;Drilling fluid is intercepted by composite pipe, to prevent it from being sprayed onto electromagnetic heater to cause damage, also to prevent it from being sprayed onto ground to pollute environment, at the same time, composite pipe is also used to cooperate with circular ring one and cylinder one, to form cavity on the outside of drill rod piece, during testing, high-pressure gas can be injected into the cavity, to simulate the outside pressure condition in actual use process of drill rod piece, so that test result is more in line with actual situation.

Description

Technical Field

[0001] This invention relates to the technical field of oil extraction. More specifically, this invention relates to a torsional fatigue testing device for simulating combined downhole load conditions in oil tubing. Background Technology

[0002] When operating downhole, oil drill strings primarily bear the complex loads generated by drilling and grinding rocks. They need to transmit significant torque and withstand the effects of high-pressure drilling fluid inside the drill string. Simultaneously, the high temperatures at depths of thousands of meters in oil and gas wells make the operating conditions for drill strings extremely harsh. In actual operations, drill strings often develop cracks due to torsional fatigue, leading to fracture failure and severely impacting the safety and efficiency of oil and gas drilling and production. Therefore, it is necessary to conduct torsional fatigue testing on drill strings to assess their reliability under extreme conditions.

[0003] During testing, electromagnetic induction heaters are often installed on the outside of the drill string to apply thermal loads simulating the high-temperature environment downhole through non-contact heating. However, under extreme torsional load conditions, the drill string may crack, causing a sudden ejection of high-pressure drilling fluid. Although the drilling fluid has a high temperature downhole, its temperature is usually significantly lower than the operating temperature of the electromagnetic induction heater. Therefore, the relatively low-temperature liquid ejected will cause a sudden drop in the local temperature of the heater, resulting in severe thermal shock and damage to the heating element. Summary of the Invention

[0004] To overcome the drawback of drill pipe cracking during torsion testing, which causes internal fluid to spray onto the heater and damage the heating element, this invention provides a torsion fatigue testing device that simulates combined downhole load conditions in oil tubing.

[0005] The technical implementation scheme of the present invention is as follows: a torsional fatigue testing device simulating combined load conditions in downhole oil tubing, comprising a base plate; a sliding plate slidably connected to the base plate; a plurality of pins inserted and detached on the sliding plate; a plurality of circular holes I opened on the base plate, the ends of the pins being inserted into the corresponding circular holes I; a plurality of circular holes II opened on the base plate; further comprising a connecting block I; a connecting block I fixedly connected to both the base plate and the sliding plate; a circular ring I fixedly connected to each connecting block I; a cylindrical cylinder I rotatably connected to each circular ring I; a cylindrical cylinder II rotatably connected to each cylindrical cylinder I; a circular ring II fixedly connected to each circular ring I; a composite pipe inserted into all the circular rings I; a pipe I connected to the composite pipe, the pipe I being fixedly connected to the composite pipe; a cavity formed between the circular rings I, the cylindrical cylinder I, the composite pipe, and the drill pipe; a driving assembly connected to the base plate, the driving assembly being used to drive the cylindrical cylinder I to rotate; a waste discharge assembly connected to the base plate, the waste discharge assembly being used to discharge the liquid in the composite pipe; and a heating assembly connected to the base plate, the heating assembly being used to heat the drill pipe.

[0006] Furthermore, the end of the pin is chamfered.

[0007] By adopting the above structure, the present invention enables convenient insertion.

[0008] Furthermore, the drive assembly includes connecting block two, a hydraulic cylinder, and connecting block three; several connecting blocks two are fixedly connected to the base plate; several connecting blocks two are also fixedly connected to the slide plate; a hydraulic cylinder is rotatably connected to each connecting block two; a connecting block three is fixedly connected to each cylinder one; the telescopic end of each hydraulic cylinder is fixedly connected to the end of the corresponding connecting block three.

[0009] Furthermore, the waste discharge assembly includes a second pipe and a plug; the second pipe is connected to the composite pipe and is fixedly connected to the composite pipe; a plug is inserted into and removed from the second pipe.

[0010] By adopting the above-described structure, the present invention achieves waste liquid discharge.

[0011] Furthermore, the heating assembly includes a connecting block four and an electromagnetic heater; several connecting blocks four are fixedly connected to the base plate; an electromagnetic heater is fixedly connected to all connecting blocks four, and the electromagnetic heater is located outside the composite tube.

[0012] Furthermore, it also includes a flow guide; the flow guide is provided on the base plate; the flow guide, the corresponding cylinder II and the composite pipe cooperate to allow the air in the composite pipe to flow smoothly into the corresponding cylinder II, and then be discharged from the corresponding cylinder II.

[0013] By employing the above-described structure, this invention achieves an airflow guiding effect.

[0014] Furthermore, there are several pipes arranged in a ring array; an annular groove is formed between the end of the composite pipe closest to pipe one and the corresponding cylinder one.

[0015] Furthermore, it also includes a braided sleeve; the composite pipe is fitted with a braided sleeve on the outside.

[0016] Furthermore, the contact surfaces of both the base plate and the skateboard are designed to be smooth.

[0017] By employing the above-described structure, the present invention achieves the effect of reducing friction.

[0018] Furthermore, a sealing ring is provided between cylinder one and cylinder two; each cylinder one has a connecting cavity near the drill pipe end for connecting to the drill pipe end, the connecting cavity being threaded to the drill pipe end; an end sealing ring is provided inside the connecting cavity, and after the drill pipe end is screwed into cylinder one, the end sealing ring is pressed, thereby sealing the connection gap between the drill pipe end and cylinder one; each cylinder two has a drilling fluid channel, and the end of cylinder two near the drill pipe is in sealed communication with the inner hole of the drill pipe; an inner flow channel sealing ring is provided between cylinder two and the inner hole of the drill pipe, so that the drilling fluid channel and the inner hole of the drill pipe form a closed flow channel; an annular sealing ring is provided between cylinder one and cylinder two, the annular sealing ring being used to isolate the drill fluid inside cylinder two. The annular cavity between the well fluid channel and the outside of the drill pipe prevents drilling fluid from entering the annular cavity and also prevents high-pressure gas in the annular cavity from entering the drilling fluid channel. A first static sealing ring is provided on the outer circumference of the first annular ring. After the end of the composite pipe is fitted onto the outer circumference of the first annular ring, the inner wall of the composite pipe presses against the first static sealing ring, thereby sealing the radial insertion gap between the composite pipe and the first annular ring. An annular sealing groove is provided on the side of the second annular ring facing the end face of the composite pipe, and a second static sealing ring is installed in the annular sealing groove. When the end face of the composite pipe abuts against the second annular ring, it presses against the second static sealing ring, thereby sealing the axial gap between the end face of the composite pipe and the second annular ring. A rotary seal is provided between the first annular ring and the first cylinder. The rotary seal is dynamically sealed with the outer circumferential surface of the first cylinder and the inner circumferential surface of the first annular ring.

[0019] The present invention has the following advantages: First, the composite pipe intercepts the ejected drilling fluid, preventing it from spraying onto the electromagnetic heater and causing damage, and also preventing it from spraying onto the ground and polluting the environment. At the same time, the composite pipe is also used in conjunction with the first ring and the first cylinder to form a cavity on the outside of the drill pipe. During the test, high-pressure gas can be injected into the cavity to simulate the external pressure of the drill pipe during actual use, making the test results more consistent with reality. Second, Pipeline 1 is used to pressurize the cavity to improve the authenticity of test results, and also to blow away the drilling fluid remaining inside the composite pipe to prevent the residual drilling fluid from forming solid impurities inside the composite pipe after drying, thereby avoiding affecting the heating uniformity of the drill pipe. Third, the air is guided to the right-hand cylinder two by the flow guide shroud to prevent the air from hitting the right-hand cylinder one and cylinder two and then turning back, which would cause poor flow. This is conducive to improving the drilling fluid blowing effect. At the same time, cylinder one is also used to cooperate with multiple pipes one. The high-pressure gas flows to the right in a ring shape against the inner wall of the composite pipe, while the drilling fluid adheres to the inner wall of the composite pipe, which can improve the blowing effect. Fourth, a braided sleeve is installed on the outside of the composite pipe. Even if the composite pipe is broken, the fragments will adhere to the braided sleeve, which helps to improve safety. Attached Figure Description

[0020] Figure 1This invention illustrates a first-view structural schematic of the torsional fatigue testing device for simulating combined downhole load conditions in oil tubing. Figure 2 This invention illustrates a second perspective structural schematic of the torsional fatigue testing device for simulating combined downhole load conditions in oil tubing. Figure 3 A schematic diagram of the structure of the driving component of the present invention is shown; Figure 4 A schematic diagram of the composite tube of the present invention is shown; Figure 5 A schematic diagram of the structure of the second ring of the present invention is shown; Figure 6 A schematic diagram of the waste discharge component of the present invention is shown; Figure 7 A schematic diagram of the annular groove of the present invention is shown; Figure 8 A schematic diagram of the structure of the air guide shield of the present invention is shown; Figure 9 A schematic diagram of the structure of the braided sleeve of the present invention is shown.

[0021] The meanings of the reference numerals in the diagram are as follows: 1-Base plate, 2-Slide plate, 3-Pin, 4-Connecting block one, 5-Ring one, 6-Cylinder one, 7-Cylinder two, 8-Ring two, 9-Composite pipe, 10-Pipe one, 11-Drill rod, 201-Connecting block two, 202-Hydraulic cylinder, 203-Connecting block three, 204-Pipe two, 205-Plug, 206-Connecting block four, 207-Electromagnetic heater, 208-Guide shroud, 209-Braided sleeve, 1091-Cavity, 1092-Round hole one, 1093-Round hole two, 1094-Annular groove. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1: A torsional fatigue testing device simulating combined downhole load conditions in oil tubing, such as... Figures 1-9As shown, it includes a base plate 1; a sliding plate 2 is slidably mounted on the base plate 1; several pins 3 are pluggably connected to the sliding plate 2; several circular holes 1092 are opened on the base plate 1, and the ends of the pins 3 are inserted into the corresponding circular holes 1092; several circular holes 1093 are also opened on the base plate 1; it also includes a connecting block 4; a connecting block 4 is fixedly connected to the base plate 1 and the sliding plate 2 respectively; a ring 5 is fixedly connected to each connecting block 4; a cylinder 6 is rotatably installed in each ring 5; a cylinder 7 is rotatably installed in each cylinder 6. Each ring 5 is also fixedly connected to a ring 8; all rings 5 ​​are connected to a composite pipe 9; the composite pipe 9 is connected to a pipe 10, and the pipe 10 is fixedly connected to the composite pipe 9; the rings 5, cylinder 6, composite pipe 9 and drill rod 11 form a cavity 1091; a drive assembly is connected to the base plate 1, which is used to drive the cylinder 6 to rotate; a waste discharge assembly is also connected to the base plate 1, which is used to discharge the liquid in the composite pipe 9; a heating assembly is also connected to the base plate 1, which is used to heat the drill rod 11.

[0024] The end of the pin 3 is chamfered, making it easier to insert the pin 3 into the round hole 1092.

[0025] The drive assembly includes a second connecting block 201, a hydraulic cylinder 202, and a third connecting block 203; two second connecting blocks 201 are bolted to the base plate 1; two second connecting blocks 201 are also bolted to the slide plate 2; a hydraulic cylinder 202 is rotatably connected to each second connecting block 201; a third connecting block 203 is fixedly connected to each cylinder 6; the telescopic end of each hydraulic cylinder 202 is fixedly connected to the end of the corresponding third connecting block 203.

[0026] The waste discharge assembly includes a second pipe 204 and a plug 205; the second pipe 204 is connected to and fixed to the composite pipe 9; the plug 205 is inserted and removed from the second pipe 204.

[0027] The heating assembly includes a connecting block 206 and an electromagnetic heater 207; two connecting blocks 206 are bolted to the base plate 1, and the connecting blocks 206 are made of alloy material; the electromagnetic heater 207 is fixedly connected to all connecting blocks 206, and the electromagnetic heater 207 is located outside the composite tube 9.

[0028] Working principle: First, manually pull the pin 3 out of the round hole 1092, then push the slide plate 2 and its parts to the right to create installation distance. Then, screw the left end of the drill rod 11 into the left cylinder 6. Next, fit the composite tube 9 onto the outside of the drill rod 11, inserting the left end of the composite tube 9 into the outside of the left ring 5, and making the left end of the composite tube 9 contact the left ring 8. Then, push the slide plate 2 and its parts to the left, making the right cylinder 6 contact the right end of the drill rod 11. Then, manually rotate the right cylinder 6, thereby opening the right side of the drill rod 11. The cylinder 6 is screwed into the right end of the drill rod 11. During this process, the parts on the right cylinder 6 move to the left, so that the right ring 5 is inserted into the right end of the composite pipe 9, and the right ring 8 contacts the right end of the composite pipe 9. At this time, the pin 3 is aligned with the round hole 1092. The pin 3 is manually moved downward to insert into the round hole 1092, fixing the slide plate 2 and its parts. Then, the external drilling fluid circulation system is connected to the two cylinders 7, and the external air pump is connected to the pipeline 10, completing the installation operation.

[0029] During testing, drilling fluid is supplied to the left cylinder 7 via an external drilling fluid circulation system. The drilling fluid flows into the inside of the drill pipe 11 through the left cylinder 7, then flows from the drill pipe 11 into the right cylinder 7, and then flows back into the external drilling fluid circulation system from the right drill pipe 11. This creates a flowing drilling fluid inside the drill pipe 11, simulating the internal liquid flow state during actual use. Simultaneously, the electromagnetic heater 207 is activated, heating the drill pipe 11 via the composite pipe 9 (such as an alumina ceramic pipe), simulating the heating conditions of the drill pipe 11 during actual use. Then, hydraulic cylinder 202 is activated, which drives connecting block 3 203 to rotate. At this time, hydraulic cylinder 202 rotates adaptively on connecting block 201, and connecting block 3 203 drives cylinder 6 to rotate within ring 5, so that cylinder 6 applies torque to the end of drill rod 11. When the torque reaches the limit that drill rod 11 can withstand, drill rod 11 will crack, causing the internal high-pressure drilling fluid to suddenly spray out. The external drilling fluid circulation system detects the change in liquid pressure and immediately stops delivering drilling fluid. At this time, the sprayed drilling fluid is intercepted by composite pipe 9 to prevent it from spraying onto the electromagnetic heater. To prevent damage to the drill fluid and to prevent it from spraying onto the ground and polluting the environment, an external collection bucket was manually placed below pipe 204, and then the plug 205 was removed, allowing the drilling fluid trapped inside the composite pipe 9 to flow from pipe 204 into the external collection bucket. During the test, inert gas was supplied to pipe 10 via an external air pump. The inert gas flowed into cavity 1091 through pipe 10, causing the air pressure inside cavity 1091 to rise. Since cavity 1091 is located outside drill pipe 11, this puts the outside of drill pipe 11 under high pressure. In actual use, the outside of drill pipe 11 is subjected to... The reflux fluid is squeezed under high pressure, which simulates the external pressure of the drill pipe 11 during actual use, making the test results more realistic. During use, the drilling fluid is intercepted by the composite pipe 9 to prevent it from spraying onto the electromagnetic heater 207 and causing damage, and to prevent it from spraying onto the ground and polluting the environment. At the same time, the composite pipe 9 is also used in conjunction with the annulus 5 and the cylinder 6 to form a cavity 1091 on the outside of the drill pipe 11. During the test, high-pressure gas can be injected into the cavity 1091 to simulate the external pressure of the drill pipe 11 during actual use, making the test results more realistic.

[0030] The drilling fluid contains various media. After the drilling fluid in the composite pipe 9 is discharged, the remaining fluid, once dried, will form solid impurities on the inside of the composite pipe 9, affecting the heating uniformity of the drill rod 11 by the electromagnetic heater 207. Therefore, after the test, the right-hand cylinder 6 is manually unscrewed from the right end of the drill rod 11, and then the cylinder 6 and its parts are moved to the right. The left end of the drill rod 11 is then unscrewed from the left-hand cylinder 6, and the drill rod 11 is removed. Then, the right-hand slide plate 2 and its parts are moved to the left, causing the right-hand ring 5 to be inserted into the inside of the left end of the composite pipe 9. At this point, the positional relationship between the ring 5, cylinder 6, cylinder 7, ring 8, and the composite pipe 9 is as follows: Figure 4 As shown, the external drilling fluid circulation system is removed, and the left cylinder 2 7 is blocked. Then, high-pressure air is supplied to the pipe 10 through an external air pump. The air flows from the left end to the right end of the composite pipe 9 and is then sprayed out from the right cylinder 2 7. This blows away the drilling fluid remaining inside the composite pipe 9, preventing residue. In use, the pipe 10 is used to pressurize the cavity 1091 to improve the authenticity of the test results. It is also used to blow away the drilling fluid remaining inside the composite pipe 9, preventing the residual drilling fluid droplets from drying and forming solid impurities inside the composite pipe 9, thereby avoiding affecting the heating uniformity of the drill rod 11.

[0031] It also includes a flow guide 208; the flow guide 208 is provided on the base plate 1, and the flow guide 208, the corresponding cylinder 2 7 and the composite pipe 9 cooperate to allow the air in the composite pipe 9 to flow smoothly into the corresponding cylinder 2 7 and then be discharged from the corresponding cylinder 2 7.

[0032] During the cleaning of composite pipe 9, such as Figure 4 As shown, when air flows to the right side of the composite pipe 9, it impacts the right-side cylinder 6 and cylinder 7 and deflects back, causing poor airflow and resulting in poor drilling fluid cleaning. Therefore, after removing the drill rod 11, the guide shield 208 is manually screwed into the right-side cylinder 6, and then the slide plate 2 and its parts move to the left, so that the guide shield 208 is inserted into the outer side of the right end of the composite pipe 9. At this time, the pin 3 is just aligned with the second round hole 1093. Then, the pin 3 is manually inserted into the second round hole 1093 to fix the slide plate 2 and its parts. At this time, the state of the composite pipe 9 and the guide shield 208 is as follows. Figure 8 As shown, during the cleaning process, after the air flows to the right end of the composite pipe 9, it is guided into the right cylinder 7 by the guide shroud 208, thus avoiding the problem of air backflow and ensuring smooth airflow to guarantee the drilling fluid cleaning effect. In use, the air is guided into the right cylinder 7 by the guide shroud 208 to prevent the air from hitting the right cylinder 6 and cylinder 7 and backflowing, which would cause poor flow and improve the drilling fluid blowing effect.

[0033] Eight pipes 10 are arranged in a ring array; an annular groove 1094 is formed between the end of the composite pipe 9 near the pipe 10 and the corresponding cylinder 6.

[0034] like Figure 7 As shown, multiple pipes 10 are arranged in a ring array. During the cleaning of the composite pipe 9, high-pressure gas is delivered into multiple pipes 10 through an external air pump. The high-pressure gas flows evenly into the annular groove 1094 through multiple pipes 10. Under the limiting action of the cylinder 6 on the left, the high-pressure gas can flow to the right in a ring shape and adhere to the inner wall of the composite pipe 9, while the drilling fluid adheres to the inner wall of the composite pipe 9, thus improving the drilling fluid blowing effect. In use, the cylinder 6 is also used to cooperate with multiple pipes 10, so that the high-pressure gas can flow to the right in a ring shape and adhere to the inner wall of the composite pipe 9, while the drilling fluid adheres to the inner wall of the composite pipe 9, thus improving the drilling fluid blowing effect.

[0035] Example 2, based on Example 1, such as Figure 9 As shown, it also includes a braided sleeve 209; the composite pipe 9 is fitted with a braided sleeve 209 on the outside.

[0036] The contact surfaces of both the base plate 1 and the slide plate 2 are designed to be smooth to reduce friction.

[0037] A sealing ring is provided between cylinder 6 and cylinder 7 to improve sealing performance. Each cylinder 6 has a connecting cavity near the drill pipe 11 for connection to the end of the drill pipe 11, the connecting cavity being threaded to the end of the drill pipe 11. An end sealing ring is provided inside the connecting cavity; after the end of the drill pipe 11 is screwed into cylinder 6, the end sealing ring is pressed, thereby sealing the connection gap between the end of the drill pipe 11 and cylinder 6. Each cylinder 7 has a drilling fluid channel, and the end of cylinder 7 near the drill pipe 11 is in sealed communication with the inner hole of the drill pipe 11. An inner flow channel sealing ring is provided between cylinder 7 and the inner hole of the drill pipe 11, forming a closed flow channel between the drilling fluid channel and the inner hole of the drill pipe 11. An annular sealing ring is provided between cylinder 6 and cylinder 7, the annular sealing ring being used to isolate the contents of cylinder 7. The drilling fluid channel and the annular cavity 1091 outside the drill pipe 11 prevent drilling fluid from entering the annular cavity 1091 and also prevent high-pressure gas in the annular cavity 1091 from entering the drilling fluid channel. A first static sealing ring is provided on the outer circumference of the first ring 5. After the end of the composite pipe 9 is fitted onto the outer circumference of the first ring 5, the inner wall of the composite pipe 9 presses against the first static sealing ring, thereby sealing the radial insertion gap between the composite pipe 9 and the first ring 5. An annular sealing groove is provided on the side of the second ring 8 facing the end face of the composite pipe 9, and a second static sealing ring is installed in the annular sealing groove. When the end face of the composite pipe 9 abuts against the second ring 8, it presses against the second static sealing ring, thereby sealing the axial gap between the end face of the composite pipe 9 and the second ring 8. A rotary seal is provided between the first ring 5 and the first cylinder 6. The rotary seal is dynamically sealed with the outer circumferential surface of the first cylinder 6 and the inner circumferential surface of the first ring 5.

[0038] The rotary seal can be a pressure-resistant rotary seal ring, a combination seal ring, a skeleton seal ring, or a mechanical seal; the rotary seal allows the cylinder-6 to rotate relative to the annular ring-5, while preventing the high-pressure gas in the annular cavity 1091 from leaking along the rotational fit gap between the annular ring-5 and the cylinder-6.

[0039] A sealing ring is provided between cylinder 6 and cylinder 7 at their rotating mating surfaces to maintain a seal when cylinder 6 rotates relative to cylinder 7. This sealing ring prevents drilling fluid in the drilling fluid channel inside cylinder 7 from leaking into the gap between cylinder 6 and cylinder 7, and also prevents high-pressure gas in the annular cavity 1091 from entering the drilling fluid channel through the gap between cylinder 6 and cylinder 7.

[0040] Working principle: Under special circumstances, when the drill pipe 11 cracks, there is a probability of generating metal fragments. The high-pressure jet of drilling fluid drives the metal fragments to move at high speed, causing them to break the composite pipe 9 and create a safety hazard. Therefore, a braided sleeve 209 is installed on the outside of the composite pipe 9. Even if the composite pipe 9 is broken, its fragments will adhere to the braided sleeve 209, which helps to improve safety.

[0041] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A torsional fatigue testing device for simulating combined load conditions in downhole oil tubing, comprising a base plate (1); a sliding plate (2) slidably connected to the base plate (1); a plurality of pins (3) inserted and removed from the sliding plate (2); a plurality of first circular holes (1092) opened on the base plate (1), the ends of the pins (3) being inserted into the corresponding first circular holes (1092); a plurality of second circular holes (1093) opened on the base plate (1); characterized in that, It also includes a connecting block 1 (4); a connecting block 1 (4) is fixedly connected to both the base plate (1) and the slide plate (2); a ring 1 (5) is fixedly connected to each connecting block 1 (4); a cylinder 1 (6) is rotatably connected inside each ring 1 (5); a cylinder 2 (7) is rotatably connected inside each cylinder 1 (6); a ring 2 (8) is fixedly connected to each ring 1 (5); a composite pipe (9) is inserted between all the rings 1 (5); and a pipe is connected to the composite pipe (9). Pipeline 1 (10) is fixedly connected to composite pipe (9); a cavity (1091) is formed between ring 1 (5), cylinder 1 (6), composite pipe (9) and drill rod (11); a drive assembly is connected to the base plate (1), which is used to drive cylinder 1 (6) to rotate; a waste discharge assembly is connected to the base plate (1), which is used to discharge the liquid in composite pipe (9); a heating assembly is connected to the base plate (1), which is used to heat drill rod (11).

2. The torsional fatigue testing equipment for simulating combined downhole load conditions of oil tubing as described in claim 1, characterized in that, The end of the pin (3) is chamfered.

3. The torsional fatigue testing equipment for simulating combined downhole load conditions of oil tubing as described in claim 1, characterized in that, The drive assembly includes a second connecting block (201), a hydraulic cylinder (202), and a third connecting block (203); several second connecting blocks (201) are fixedly connected to the base plate (1); several second connecting blocks (201) are also fixedly connected to the slide plate (2); a hydraulic cylinder (202) is rotatably connected to each second connecting block (201); a third connecting block (203) is fixedly connected to each cylinder (6); the telescopic end of each hydraulic cylinder (202) is fixedly connected to the end of the corresponding third connecting block (203).

4. A torsional fatigue testing device for simulating combined downhole load conditions of oil tubing as described in claim 3, characterized in that, The waste discharge assembly includes a second pipe (204) and a plug (205); the second pipe (204) is connected to the composite pipe (9), and the second pipe (204) is fixedly connected to the composite pipe (9); the plug (205) is inserted and removed from the second pipe (204).

5. A torsional fatigue testing device for simulating combined downhole load conditions of oil tubing as described in claim 4, characterized in that, The heating assembly includes a connecting block four (206) and an electromagnetic heater (207); several connecting blocks four (206) are fixedly connected to the base plate (1); an electromagnetic heater (207) is fixedly connected to all connecting blocks four (206), and the electromagnetic heater (207) is located outside the composite tube (9).

6. A torsional fatigue testing device for simulating combined downhole load conditions of oil tubing as described in claim 5, characterized in that, It also includes a flow guide (208); the flow guide (208) is provided on the base plate (1); the flow guide (208), the corresponding cylinder two (7) and the composite pipe (9) cooperate to allow the air in the composite pipe (9) to flow smoothly into the corresponding cylinder two (7) and then be discharged from the corresponding cylinder two (7).

7. A torsional fatigue testing device for simulating combined downhole load conditions of oil tubing as described in claim 6, characterized in that, There are several pipes (10) arranged in a ring array; the end of the composite pipe (9) near the pipe (10) forms an annular groove (1094) with the corresponding cylinder (6).

8. A torsional fatigue testing device for simulating combined downhole load conditions of oil tubing as described in claim 7, characterized in that, It also includes a braided sleeve (209); the composite pipe (9) is fitted with a braided sleeve (209) on the outside.

9. A torsional fatigue testing device for simulating combined downhole load conditions of oil tubing as described in any one of claims 1-8, characterized in that, The contact surfaces of the base plate (1) and the slide plate (2) are both set to smooth surfaces.

10. A torsional fatigue testing device for simulating combined downhole load conditions of oil tubing as described in claim 9, characterized in that, A sealing ring is provided between cylinder one (6) and cylinder two (7); each cylinder one (6) has a connecting cavity for connecting with the end of the drill rod (11) at one end near the drill rod (11), the connecting cavity can be threaded to the end of the drill rod (11); an end sealing ring is provided in the connecting cavity, and the end sealing ring is pressed after the end of the drill rod (11) is screwed into cylinder one (6), thereby sealing the connection between the end of the drill rod (11) and cylinder one (6). The cylinder 2 (7) is provided with a drilling fluid channel. The end of the cylinder 2 (7) near the drill pipe (11) is sealed and connected to the inner hole of the drill pipe (11). An inner flow channel sealing ring is provided between the cylinder 2 (7) and the inner hole of the drill pipe (11) to form a closed flow channel between the drilling fluid channel and the inner hole of the drill pipe (11). An annular sealing ring is provided between the cylinder 1 (6) and the cylinder 2 (7). The annular sealing ring is used to isolate the drilling fluid channel in the cylinder 2 (7). The annular cavity (1091) outside the drill pipe (11) prevents drilling fluid from entering the annular cavity (1091) and also prevents high-pressure gas in the annular cavity (1091) from entering the drilling fluid channel; a first static sealing ring is provided on the outer circumference of the first ring (5). After the end of the composite pipe (9) is fitted onto the outer circumference of the first ring (5), the inner wall of the composite pipe (9) presses against the first static sealing ring, thereby sealing the radial insertion gap between the composite pipe (9) and the first ring (5). A ring-shaped sealing groove is provided on the side of the second ring (8) facing the end face of the composite pipe (9), and a second static sealing ring is installed in the ring-shaped sealing groove. When the end face of the composite pipe (9) abuts against the second ring (8), the second static sealing ring is pressed, thereby sealing the axial gap between the end of the composite pipe (9) and the second ring (8). A rotary seal is provided between the first ring (5) and the first cylinder (6). The rotary seal is dynamically sealed with the outer circumferential surface of the first cylinder (6) and the inner circumferential surface of the first ring (5).

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