A drill pipe backoff and method of use

Abstract

This invention proposes a drill pipe reverser and its usage method, belonging to the field of downhole tool technology. It includes a fixedly connected cycloidal gear housing and anchoring assembly, as well as a threadedly connected input shaft and eccentric shaft. An eccentric section is provided at the end of the eccentric shaft away from the input shaft, and a cycloidal gear is fitted onto the eccentric section. The end of the cycloidal gear away from the eccentric section is connected to an output shaft via a coupling. The cycloidal gear housing and anchoring assembly are fitted onto the outer surfaces of the eccentric shaft, coupling, and output shaft. An inner cycloidal gear is provided inside the cycloidal gear housing, and the inner cycloidal gear meshes with the cycloidal gear. This invention solves the problem of involute gears easily breaking under high torque by designing an inner cycloidal gear meshing with the cycloidal gear. Furthermore, in oil and gas wells, commonly used involute gear structures suffer from insufficient strength and few contact teeth.

Description

Technical Field

[0001] This invention belongs to the field of downhole tool technology, and specifically relates to a drill pipe reverser and its usage method. Background Technology

[0002] During drilling operations, stuck drill pipe and broken drill string accidents are common. For complex faults that are difficult to unstick quickly or cannot be successfully retrieved directly, a segmented reverse threading method is often adopted. This method involves connecting the lower reverse threading drill pipe to the corresponding retrieval tool and reversing the threading to transfer the reverse torque at the wellhead to the retrieval tool. This applies a reverse torque greater than the rated upper threading torque value to the drill pipe thread, thus unscrewing the stuck drill pipe. This method requires a large number of reverse threading drill pipes, resulting in high operating costs.

[0003] Existing rotary lever reversers all use involute gears. When involute gears use planetary gear transmission mode, there are fewer teeth in contact transmission, and the force on a single tooth is high. Due to the small diameter of wellbore in oil and gas wells, the overall strength of involute gear transmission is insufficient, and the probability of gear tooth breakage is relatively high. It is impossible to guarantee structural strength when transmitting large torque.

[0004] Therefore, the existing reverse threading tools have the following shortcomings: First, the existing reverse threading tools are mostly applicable to sucker rods, and the counter torque provided is less than the threading torque of the drill pipe; Second, under high torque, due to the limitation of wellbore size, the commonly used involute gear structure has insufficient strength; Third, the existing reverse threading tools do not have internal fluid channels, and cannot flush away fish or establish circulation; Fourth, the anchoring part cannot be adapted to the process flow during reverse threading operations. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a drill pipe reverser, comprising a fixedly connected cycloidal gear housing and an anchoring assembly, as well as a threadedly connected input shaft and eccentric shaft. The eccentric shaft has an eccentric section at its end away from the input shaft, and a cycloidal gear is fitted onto the eccentric section. The end of the cycloidal gear away from the eccentric section is connected to the output shaft via a coupling.

[0006] The cycloidal gear housing and anchoring assembly are mounted on the outer surfaces of the eccentric shaft, coupling and output shaft. An inner cycloidal gear is provided inside the cycloidal gear housing, and the inner cycloidal gear meshes with the cycloidal gear.

[0007] Furthermore, the drill pipe reverser also includes a guide pipe, which is sequentially installed in the central circular hole of the eccentric shaft, the through hole one of the cycloidal gear, and the through hole two of the coupling; the two ends of the guide pipe are respectively connected to the input shaft and the output shaft.

[0008] Furthermore, the diameters of the first through hole and the second through hole are greater than or equal to the sum of the outer diameter of the guide tube and twice the eccentricity of the eccentric segment.

[0009] Furthermore, the drill pipe reverser also includes a suspension housing, which is fitted onto the outer surface of the input shaft and the eccentric shaft, and the suspension housing is threadedly connected to the end of the cycloidal gear housing away from the coupling.

[0010] Furthermore, a clamp is provided between the input shaft and the suspension housing, and the clamp is rotatably installed in a groove on the outer surface of the input shaft.

[0011] Furthermore, a balance sealing piston and a spacer are slidably installed between the suspension housing and the eccentric shaft.

[0012] Furthermore, the spacer is located between the balance sealing piston and the three-piece clamp.

[0013] Furthermore, the coupling includes a cross slider and a slider output shaft; a convex plate is provided at each end of the cross slider, and the two convex plates are perpendicular to each other. One convex plate is slidably installed in the slide rail one of the cycloidal gear, and the other is slidably installed in the slide rail two of the slider output shaft. The end of the slider output shaft away from the cross slider is threadedly connected to the output shaft.

[0014] Furthermore, the anchoring assembly is connected to the output shaft via a pin.

[0015] Furthermore, the anchoring assembly includes an anchoring housing, which is threaded to one end of the cycloidal gear housing. The outer surface of the anchoring housing is provided with a plurality of sequentially connected sloping slides along the circumferential direction. An anchoring block is slidably installed on the outer surface of the sloping slide. A groove is provided in the recess of the sloping slide, and a pin passes through the groove and is threadedly connected to a threaded hole on the outer surface of the output shaft.

[0016] A method for using a drill pipe reverser, comprising the following steps:

[0017] The input shaft is connected to a standard drill pipe via a connector, and the output shaft is connected to a special tool.

[0018] The ordinary drill rod drives the input shaft to rotate in the forward direction. When the special tool comes into contact with the fish, the output shaft is resisted. The cycloidal gear and the inner cycloidal gear form an inner cycloidal gear meshing transmission. The cycloidal gear drives the anchoring component and the output shaft to rotate clockwise at a certain reduction ratio.

[0019] Once the required positive clamping torque for the fish to fall is reached, the pin is sheared, and the anchoring block on the anchoring assembly contacts the well wall, thus anchoring the anchoring assembly to the well wall.

[0020] The cycloidal gear housing is fixed by an anchoring assembly. The cycloidal gear revolves clockwise around the inner cycloidal gear through the rotation of the eccentric shaft, but rotates counterclockwise. This, in turn, drives the output shaft and a special tool to rotate counterclockwise through a coupling, causing the multi-section fish trap to separate.

[0021] Beneficial effects:

[0022] 1. This invention solves the danger of involute gears easily breaking under high torque by designing an internal cycloidal gear to mesh with a cycloidal gear. It also solves the technical problems of insufficient strength and few contact teeth in commonly used involute gear structures in oil and gas wells.

[0023] 2. By setting up a guide tube that is connected to the input shaft and the output shaft, the present invention can achieve the rinsing of the fallen fish. The special tool can be rinsed before fastening, which facilitates the subsequent fastening connection.

[0024] 3. The present invention connects the anchoring component and the output shaft via a pin, thereby enabling the anchoring component and the output shaft to rotate synchronously or the pin to be sheared off, and then the output shaft drives a special tool to reverse, preventing premature reversal of the output shaft and the technical problem of loose fastening.

[0025] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A schematic diagram of the overall structure of the drill pipe reverser in an embodiment of the present invention is shown.

[0028] Figure 2 It shows Figure 1 A cross-sectional schematic diagram.

[0029] Figure 3 It shows Figure 2 A magnified schematic diagram of a partial cross-section.

[0030] Figure 4 A schematic diagram of the clamp structure of the drill pipe reverse clamp in an embodiment of the present invention is shown.

[0031] Figure 5 A schematic diagram of the eccentric shaft structure of the drill pipe undercut device in an embodiment of the present invention is shown.

[0032] Figure 6A schematic diagram of the cycloidal gear structure of the drill pipe backing device in an embodiment of the present invention is shown.

[0033] Figure 7 A schematic diagram of the cross slider structure of the drill pipe undercut device in an embodiment of the present invention is shown.

[0034] Figure 8 A schematic diagram of the slider output shaft structure of the drill pipe undercut device in an embodiment of the present invention is shown.

[0035] Figure 9 A schematic diagram of the cycloidal gear housing of the drill pipe reverser in an embodiment of the present invention is shown.

[0036] Figure 10 A schematic diagram of the anchoring assembly of the drill pipe undercut device in an embodiment of the present invention is shown.

[0037] Figure 11 It shows Figure 10 A cross-sectional schematic diagram.

[0038] Figure 12 A flowchart illustrating the method of using the drill pipe reverser in an embodiment of the present invention is shown.

[0039] In the diagram, 1. Connector; 2. Input shaft; 3. Suspension housing; 4. Cycloidal gear housing; 5. Cycloidal gear; 6. Coupling; 7. Slider output shaft; 8. Anchor housing; 9. Anchor block; 10. Output shaft; 11. Sliding bearing one; 12. Clamp; 13. Spacer; 14. Balance sealing piston; 15. Eccentric shaft; 16. Guide tube; 17. Sliding bearing two; 18. Eccentric section; 19. Protruding shaft; 20. Slide one; 21. Through hole one; 22. Cross slider; 23. Through hole two; 24. Slide two; 25. Oil injection hole; 26. Internal cycloidal gear; 27. Anchoring assembly; 28. Limit screw; 29. ​​Pin; 30. Inclined groove. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0041] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0042] In the description of this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this invention, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, those skilled in the art can combine different embodiments or examples and features of different embodiments or examples described in this invention without contradiction.

[0043] like Figure 1 As shown, Figure 1 A schematic diagram of the overall structure of the drill pipe undercut device in an embodiment of the present invention is shown. (Reference) Figure 1 A drill pipe reverser includes a threaded input shaft 2 and an eccentric shaft 15. An eccentric section 18 is provided at the end of the eccentric shaft 15 away from the input shaft 2, and a cycloidal gear 5 is fitted onto the eccentric section 18 (see reference). Figure 6 The end of the cycloidal gear 5 away from the eccentric section 18 is connected to the output shaft 10 via a coupling 6;

[0044] The cycloidal gear housing 4 and the anchoring assembly 27 are fixedly connected, and the cycloidal gear housing 4 and the anchoring assembly 27 are fitted onto the outer surfaces of the eccentric shaft 15, the coupling 6, and the output shaft 10. An inner cycloidal gear 26 is provided inside the cycloidal gear housing 4 (see reference). Figure 9 The internal cycloidal gear 26 meshes with the cycloidal gear 5; the anchoring assembly 27 is connected to the output shaft 10 via a pin 29.

[0045] Specifically, the cycloidal gear 5 and the inner cycloidal gear 26 of the cycloidal gear housing 4 form a gear transmission. Existing rotary rod reversers all use involute gears. However, due to the small diameter of oil and gas wellbores, cycloidal gear teeth are stronger than involute gear teeth for the same diameter, and can withstand greater torque. Simultaneously, in planetary gear transmission mode, fewer teeth of the involute gear are in contact at the same time, resulting in greater stress on each tooth and increasing the probability of tooth breakage. The meshing of the cycloidal gear 5 and the inner cycloidal gear 26 provides a counter-torque greater than the torque applied to the drill pipe thread, ensuring sufficient strength for the reduction and torque-increasing structure. This effectively replaces reverse-threaded drill pipes, allowing for the completion of retrieval and unblocking operations using conventional forward-threaded drill pipes, improving on-site work efficiency and reducing the cost of unblocking complex downhole operations. The lower end of the connector 1 is threadedly connected to the input shaft 2. The other end of the connector 1 is connected to the surface drive mechanism via ordinary drill pipe. A needle roller bearing is installed between the eccentric section 18 and the cycloidal gear 5 to reduce friction. (Reference) Figure 6 One end of the cycloidal gear 5 is provided with a protruding shaft 19, and a slide 20 is provided at the outer end of the protruding shaft 19. A through hole 21 is provided on the cycloidal gear 5, and the through hole 21 passes through the cycloidal gear 5 and the protruding shaft 19.

[0046] refer to Figure 2 The drill pipe reversing device also includes a guide pipe 16, which is installed in the central circular hole of the eccentric shaft 15, the through hole 21 of the cycloidal gear 5, and the through hole 23 of the coupling 6. Both ends of the guide pipe 16 are connected to the input shaft 2 and the output shaft 10, respectively. Specifically, the guide pipe 16 is used to circulate drilling fluid, allowing for flushing of the drill fluid before the special tool reversing, thus facilitating subsequent reversing connection. Simultaneously, by setting up the guide pipe 16 and corresponding seals, drilling fluid is prevented from entering the cycloidal gear 5 and the coupling 6, which could cause corrosion over time and reduce the service life of the parts.

[0047] In this invention, the diameters of through hole 1 21 and through hole 23 are both greater than or equal to the sum of the outer diameter of the guide tube 16 and twice the eccentricity of the eccentric section 18; the two ends of the guide tube 16 are respectively connected to the central circular holes of the eccentric shaft 15 and the slider output shaft 7.

[0048] Specifically, it facilitates the use of eccentric shaft 15 (reference) Figure 5When rotating, it drives the eccentric section 18 to rotate, thereby preventing interference and wear between parts. The guide tube 16 passes through the interior of the eccentric shaft 15, cycloidal gear 5, coupling 6, and slider output shaft 7. The upper end of the guide tube 16 is fixed in the central hole of the eccentric shaft 15 by a snap ring, and the lower end is fixed in the circular hole inside the slider output shaft 7. The through hole 21 on the cycloidal gear 5 and the through hole 23 on the coupling 6 are at least twice the outer diameter of the guide tube 16 plus more than twice the eccentricity (the eccentricity is the distance from the center of the eccentric shaft 15 to the center of the eccentric section 18), so that the cycloidal gear 5 and the coupling 6 can rotate smoothly without interference.

[0049] In this invention, the drill pipe reverser also includes a suspension housing 3, which is fitted onto the outer surfaces of the input shaft 2 and the eccentric shaft 15, and the suspension housing 3 is connected to the cycloidal gear housing 4 (see reference). Figure 10 The end away from the coupling 6 is threaded. A clamp 12 is provided between the input shaft 2 and the suspension housing 3, and the clamp 12 is rotatably installed in a groove on the outer surface of the input shaft 2.

[0050] Specifically, the suspension housing 3 is used to protect the input shaft 2 and to connect the cycloidal gear housing 4. By limiting the suspension housing 3, the suspension housing 3, the cycloidal gear housing 4 and the anchoring assembly 27 can rotate outside the input shaft 2 and the output shaft 10.

[0051] Specifically, three clamps 12 arranged in a circular array are provided between the input shaft 2 and the suspension housing 3 (see reference). Figure 4 The clamp 12 is inserted into the groove on the surface of the input shaft 2. At the same time, the clamp 12 also serves to limit the suspension housing 3. The upper end of the suspension housing 3 has an inwardly recessed step. The clamp 12 serves to limit the step and thus limit the suspension housing 3. The friction between the clamp 12 and the suspension housing 3 can be eliminated by setting a copper ring.

[0052] In the above embodiments, another optional implementation is that a balance sealing piston 14 and a spacer 13 are slidably installed between the suspension housing 3 and the eccentric shaft 15.

[0053] Specifically, a spacer 13 is provided between the balance sealing piston 14 and the three-piece clamp 12. The spacer 13 is used to limit the balance sealing piston 14, thereby preventing the balance sealing piston 14 from contacting the clamp 12 and causing wear on the balance sealing piston 14. An oil injection hole 25 is provided on the cycloidal gear housing 4 (see reference). Figure 1Solid lubricating oil or grease is injected into the gap between the cycloidal gear housing 4 and the eccentric shaft 15 through the oil injection hole 25. The lubricating oil pushes the balance sealing piston 14, which in turn moves towards the clamp 12. After filling, the oil injection hole 25 is blocked by the sealing bolt. Since the fish is usually located at a depth of more than 2,000 meters underground, the pressure at the bottom of the well is greater than the surface pressure. At this time, the balance sealing piston 14 moves away from the spacer 13, so that there is sufficient lubricating oil between the cycloidal gear 5 and the inner cycloidal gear 26, between the cycloidal gear 5 and the coupling 6, and between the coupling 6 and the slider output shaft 7, thereby achieving lubrication.

[0054] In the above embodiments, another optional implementation is that a sliding bearing 11 is provided between the input shaft 2 and the suspension housing 3.

[0055] Specifically, sliding bearing 11 generates a small frictional force between the input shaft 2 and the suspension housing 3, and sliding bearing 17 generates a small frictional force between the anchor housing 8 and the output shaft 10, thereby reducing friction and lowering frictional losses.

[0056] refer to Figure 7 The coupling 6 includes a cross slider 22 and a slider output shaft 7 (see reference). Figure 8 The cross slider 22 has a convex plate at each end, and the two convex plates are perpendicular to each other. One convex plate is slidably installed in the slide rail 20 of the cycloidal gear 5, and the other is slidably installed in the slide rail 24 of the slider output shaft 7. The end of the slider output shaft 7 away from the cross slider 22 is threadedly connected to the output shaft 10.

[0057] Specifically, a horizontal plate is provided at each end of the cross slider 22, and the two horizontal plates are perpendicular to each other. The two horizontal plates are slidably installed in slide rail 1 20 and slide rail 24 respectively, and a through hole 23 is provided at the center of the cross slider 22; at the same time, the slider output shaft 7 sits on the anchor housing 8, and a thrust bearing can be provided between the two. The lower end of the slider output shaft 7 is connected to the output shaft 10 by a thread, and the lower end of the output shaft 10 can be connected to various special tools, such as expansion threading tools, tapping tools, etc.

[0058] refer to Figure 10 The anchoring assembly 27 includes an anchoring housing 8, which is threaded to one end of the cycloidal gear housing 4. The outer surface of the anchoring housing 8 has a plurality of sequentially connected sloping tracks arranged circumferentially. Anchor blocks 9 are slidably mounted on the outer surface of the sloping tracks. A groove 30 is provided on the outer surface of the recessed portion of the sloping track, and a pin 29 passes through the groove 30 and is threadedly connected to a threaded hole on the outer surface of the output shaft 10 (see reference). Figure 11 ).

[0059] Specifically, the anchoring assembly 27 consists of an anchoring housing 8, an anchoring block 9, a limiting screw 28, and a pin 29. The anchoring housing 8 has a sloping slide in the middle, on which the anchoring block 9 can slide and is limited by the limiting screw 28. The anchoring housing 8 has a sloping groove 30, which limits the circumferential movement of the anchoring block 9 before the pin 29 is sheared. The bottom of the pin 29 is threaded into the output shaft 10, and the upper part passes through the sloping groove 30 and contacts the side of the anchoring block 9.

[0060] Working principle:

[0061] When assembly is complete, the tool is in its initial state, such as... Figure 1 and Figure 2 As shown. When reverse threading is required, connect the connector 1 at the top of this tool to the ordinary drill pipe, and connect the ordinary drill pipe to the ground drive equipment. Connect the lower end of the output shaft 10 to a special tool, such as an expansion threading tool or a tapping tool. Lower this device and the special tool into the oil and gas well.

[0062] When reversed, the ground drive mechanism drives the ordinary drill rod and input shaft 2 clockwise, causing the input shaft 2 to rotate. At this time, the entire tool rotates forward along with the input shaft 2.

[0063] Before the special tool comes into contact with the fish, drilling fluid is injected into the ordinary drill pipe through the ground. The drilling fluid then flows through the ordinary drill pipe to the input shaft 2, then through the guide pipe 16 to the output shaft 10, and then flows out from the special tool, thus washing away the fish and increasing the probability of hooking.

[0064] When the special tool comes into contact with the fish, connector 1, input shaft 2, and eccentric shaft 15 continue to rotate clockwise along with the ordinary drill rod. The expansion hook retrieval tool at the lower end of output shaft 10 requires a certain upward hooking torque to hook, and therefore encounters a certain resistance. After the resistance increases to a certain extent, the cycloidal gear 5 and the inner cycloidal gear 26 of the cycloidal gear housing 4 form an inner cycloidal gear meshing transmission (that is, the eccentric shaft 15 drives the cycloidal gear 5 to revolve and rotate clockwise around the inner cycloidal gear 26). The rotation of the cycloidal gear 5 drives the cycloidal gear housing 4 and the anchoring housing 8 to rotate clockwise at a certain reduction ratio (the rotation speed of the cycloidal gear 5 and the rotation speed of the input shaft 2 are at a certain reduction ratio). The anchoring housing 8 drives the output shaft 10 to rotate clockwise through the pin 29. The anchoring block 9 does not move under the circumferential limit of the pin 29. At this time, the expansion hook retrieval tool hooks with the fish with a certain positive upward hooking torque.

[0065] Once the required positive clamping torque for the unblocking tool (fish dropper) is reached (fish droppers are generally made of multiple sections connected by threads), the tool is lifted to clamp the fish dropper, thus locking the tool and the fish dropper together.

[0066] Then, pin 29 is sheared by force, and output shaft 10 stops rotating (due to the large resistance generated by the falling fish). Anchor housing 8 continues to rotate forward. In the horizontal well, under the action of gravity, anchor block 9 begins to slide counterclockwise circumferentially along the sloped slide of anchor housing 8 under the action of friction from the well wall (i.e., the speed of anchor block 9 is less than the speed of anchor housing 8). At this time, input shaft 2 drives eccentric shaft 15, which in turn drives cycloidal gear housing 4 and anchor housing 8 to rotate. Since output shaft 10 is connected to the falling fish, it does not rotate. When the speed of anchor block 9 is less than the speed of anchor housing 8, anchor block 9 rotates counterclockwise relative to anchor housing 8. Anchor block 9 moves along the sloped slide towards the highest protruding direction of the sloped slide, thereby increasing the outer diameter. Anchor block 9 contacts the well wall, thus achieving the purpose of anchoring. Since pin 29 has been sheared, when anchor block 9 slides, it can push part of pin 29 into the inclined groove 30. It no longer has the function of circumferential limiting; after anchoring, the anchoring housing 8 and the cycloidal gear housing 4 are fixed (because the anchoring block 9 contacts the well wall, thus fixing the anchoring housing 8). The connector 1, input shaft 2 and eccentric shaft 15 still follow the ground drive to rotate clockwise, but the cycloidal gear 5 meshes with the inner cycloidal gear 26 of the cycloidal gear housing 4 to form a small tooth difference gear transmission. Through the clockwise rotation of the eccentric shaft 15, the cycloidal gear 5 starts to rotate counterclockwise with a certain reduction ratio (because the cycloidal gear housing 4 is stationary, the cycloidal gear 5 revolves clockwise around the inner cycloidal gear 26 of the cycloidal gear housing 4, but rotates counterclockwise), which in turn drives the coupling 6, the slider output shaft 7 and the output shaft 10 to rotate counterclockwise, thereby driving the expansion buckle fishing tool to rotate the fallen fish counterclockwise. The multiple sections of the fallen fish can be unscrewed by rotating counterclockwise, so that the multiple sections of the fallen fish are separated by reverse buckling, thus facilitating the multiple segmented fishing of the fallen fish.

[0067] refer to Figure 12 A method for using a drill pipe reverser, comprising the following steps:

[0068] The input shaft 2 is connected to a standard drill rod via connector 1, and the output shaft 10 is connected to a special tool.

[0069] When the ordinary drill rod drives the input shaft 2 to rotate in the forward direction, the output shaft 10 is resisted when the special tool comes into contact with the fish. The cycloidal gear 5 and the inner cycloidal gear 26 form an inner cycloidal gear meshing transmission. The cycloidal gear 5 drives the anchoring component 27 and the output shaft 10 to rotate clockwise at a certain reduction ratio.

[0070] When the positive clamping torque required for the fish to fall is reached, the pin 29 is sheared, and the anchoring block 9 on the anchoring assembly 27 contacts the well wall, so that the anchoring assembly 27 is anchored to the well wall.

[0071] The cycloidal gear housing 4 is fixed by the anchoring assembly 27. The cycloidal gear 5 revolves clockwise around the anchoring assembly 27 by the rotation of the eccentric shaft 15, but rotates counterclockwise. This, in turn, drives the output shaft 10 and the special tool to rotate counterclockwise through the coupling 6, causing the multi-section fish trap to separate.

[0072] Specifically, when the assembly is complete, the tool is in its initial state. Connect the connector 1 on the upper part of the tool to the ordinary drill pipe, and connect the ordinary drill pipe to the ground drive equipment. Connect the lower end of the output shaft 10 to a special tool, such as an expansion thread fishing tool or a tapping tool. Lower the device and the special tool into the oil and gas well.

[0073] When reversed, the ground drive mechanism drives the ordinary drill rod and input shaft 2 clockwise, causing the input shaft 2 to rotate. At this time, the entire tool rotates forward along with the input shaft 2.

[0074] When the special tool comes into contact with the fish, connector 1, input shaft 2, and eccentric shaft 15 continue to rotate clockwise along with the ordinary drill rod. The expansion hook retrieval tool at the lower end of output shaft 10 requires a certain upward hooking torque to hook, and therefore encounters a certain resistance. After the resistance increases to a certain extent, the cycloidal gear 5 and the inner cycloidal gear 26 of the cycloidal gear housing 4 form an inner cycloidal gear meshing transmission (that is, the eccentric shaft 15 drives the cycloidal gear 5 to revolve and rotate clockwise around the inner cycloidal gear 26). The rotation of the cycloidal gear 5 drives the cycloidal gear housing 4 and the anchoring housing 8 to rotate clockwise at a certain reduction ratio (the rotation speed of the cycloidal gear 5 and the rotation speed of the input shaft 2 are at a certain reduction ratio). The anchoring housing 8 drives the output shaft 10 to rotate clockwise through the pin 29. The anchoring block 9 does not move under the circumferential limit of the pin 29. At this time, the expansion hook retrieval tool hooks with the fish with a certain positive upward hooking torque.

[0075] Once the required positive clamping torque for the unblocking tool (fish dropper) is reached (fish droppers are generally made of multiple sections connected by threads), the tool is lifted to clamp the fish dropper, thus locking the tool and the fish dropper together.

[0076] Then, pin 29 is sheared by force, and output shaft 10 stops rotating (due to the large resistance generated by the falling fish). Anchor housing 8 continues to rotate forward. In the horizontal well, under the action of gravity, anchor block 9 begins to slide counterclockwise circumferentially along the sloped slide of anchor housing 8 under the action of friction from the well wall (i.e., the speed of anchor block 9 is less than the speed of anchor housing 8). At this time, input shaft 2 drives eccentric shaft 15, which in turn drives cycloidal gear housing 4 and anchor housing 8 to rotate. Since output shaft 10 is connected to the falling fish, it does not rotate. When the speed of anchor block 9 is less than the speed of anchor housing 8, anchor block 9 rotates counterclockwise relative to anchor housing 8. Anchor block 9 moves along the sloped slide towards the highest protruding direction of the sloped slide, thereby increasing the outer diameter. Anchor block 9 contacts the well wall, thus achieving the purpose of anchoring. Since pin 29 has been sheared, when anchor block 9 slides, it can push part of pin 29 into the inclined groove 30. It no longer has the function of circumferential limiting; after anchoring, the anchoring housing 8 and the cycloidal gear housing 4 are fixed (because the anchoring block 9 contacts the well wall, thus fixing the anchoring housing 8). The connector 1, input shaft 2 and eccentric shaft 15 still follow the ground drive to rotate clockwise, but the cycloidal gear 5 meshes with the inner cycloidal gear 26 of the cycloidal gear housing 4 to form a small tooth difference gear transmission. Through the clockwise rotation of the eccentric shaft 15, the cycloidal gear 5 starts to rotate counterclockwise with a certain reduction ratio (because the cycloidal gear housing 4 is stationary, the cycloidal gear 5 revolves clockwise around the inner cycloidal gear 26 of the cycloidal gear housing 4, but rotates counterclockwise), which in turn drives the coupling 6, the slider output shaft 7 and the output shaft 10 to rotate counterclockwise, thereby driving the expansion buckle fishing tool to rotate the fallen fish counterclockwise. The multiple sections of the fallen fish can be unscrewed by rotating counterclockwise, so that the multiple sections of the fallen fish are separated by reverse buckling, thus facilitating the multiple segmented fishing of the fallen fish.

[0077] This allows the upper drill rod of the tool to rotate clockwise, thereby causing the lower drill bit of the tool to rotate counterclockwise.

[0078] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0079] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0080] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0081] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

Claims

1. A drill pipe backoff, characterized by, It includes a fixedly connected cycloidal gear housing (4) and anchoring assembly (27), as well as a threadedly connected input shaft (2) and eccentric shaft (15). An eccentric section (18) is provided at the end of the eccentric shaft (15) away from the input shaft (2). A cycloidal gear (5) is fitted on the eccentric section (18). The end of the cycloidal gear (5) away from the eccentric section (18) is connected to the output shaft (10) through a coupling (6). The cycloidal gear housing (4) and the anchoring assembly (27) are fitted on the outer surfaces of the eccentric shaft (15), the coupling (6) and the output shaft (10). An inner cycloidal gear (26) is provided inside the cycloidal gear housing (4), and the inner cycloidal gear (26) meshes with the cycloidal gear (5).

2. A pipe backoff as defined in claim 1 wherein, The drill pipe reverser also includes a guide pipe (16), which is installed in the central hole of the eccentric shaft (15), the through hole one (21) of the cycloidal gear (5) and the through hole two (23) of the coupling (6); the two ends of the guide pipe (16) are connected to the input shaft (2) and the output shaft (10) respectively.

3. A pipe backoff as defined in claim 2 wherein, The diameters of the first through hole (21) and the second through hole (23) are both greater than or equal to the sum of the outer diameter of the guide tube (16) and twice the eccentricity of the eccentric segment (18).

4. A pipe backoff as defined in claim 1 wherein, The drill pipe reverser also includes a suspension housing (3), which is fitted on the outer surface of the input shaft (2) and the eccentric shaft (15), and the suspension housing (3) is threadedly connected to the end of the cycloidal gear housing (4) away from the coupling (6).

5. A drill pipe reversing device according to claim 4, characterized in that, A clamp (12) is provided between the input shaft (2) and the suspension housing (3), and the clamp (12) is rotatably installed in a groove on the outer surface of the input shaft (2).

6. A pipe backoff as defined in claim 4 wherein, A balance sealing piston (14) and a spacer (13) are slidably installed between the suspension housing (3) and the eccentric shaft (15).

7. A pipe backoff as defined in claim 6 wherein, The spacer (13) is located between the balance sealing piston (14) and the three-piece clamp (12).

8. A pipe backoff as defined in claim 1 wherein, The coupling (6) includes a cross slider (22) and a slider output shaft (7); the cross slider (22) has a convex plate at each end, and the two convex plates are perpendicular to each other. One convex plate is slidably installed in the slide rail one (20) of the cycloidal gear (5), and the other is slidably installed in the slide rail two (24) of the slider output shaft (7). The end of the slider output shaft (7) away from the cross slider (22) is threadedly connected to the output shaft (10).

9. A pipe backoff as defined in claim 1 wherein, The anchoring assembly (27) is connected to the output shaft (10) via a pin (29).

10. A pipe backoff as defined in claim 9 wherein, The anchoring assembly (27) includes an anchoring housing (8), which is threaded to one end of the cycloidal gear housing (4). The outer surface of the anchoring housing (8) is provided with a plurality of sequentially connected sloping slides along the circumferential direction. An anchoring block (9) is slidably installed on the outer surface of the sloping slide. A groove (30) is provided in the recess of the sloping slide. A pin (29) passes through the groove (30) and is threaded to a threaded hole on the outer surface of the output shaft (10).

11. A method of using a drill pipe backoff, comprising: The drill pipe reversing device according to any one of claims 1-10 includes the following steps: The input shaft (2) is connected to the ordinary drill pipe through the connector (1), and the output shaft (10) is connected to the special tool; When the ordinary drill rod drives the input shaft (2) to rotate in the forward direction, the output shaft (10) is resisted when the special tool comes into contact with the fish. The cycloidal gear (5) and the inner cycloidal gear (26) form an inner cycloidal gear meshing transmission. The cycloidal gear (5) drives the anchoring assembly (27) and the output shaft (10) to rotate clockwise with a certain reduction ratio. When the positive clamping torque required for the fish to fall is reached, the pin (29) is sheared, and the anchoring block (9) on the anchoring assembly (27) contacts the well wall, so that the anchoring assembly (27) is anchored to the well wall. The cycloidal gear housing (4) is fixed by the anchoring assembly (27). The cycloidal gear (5) revolves clockwise around the inner cycloidal gear (26) by the rotation of the eccentric shaft (15), but rotates counterclockwise. Then, through the coupling (6), it drives the output shaft (10) and the special tool to rotate counterclockwise, causing the multi-section fish to be separated.

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