Axial constraint-unlocked abandoned casing backoff plasma cutting device and method

Abstract

The application discloses a kind of abandoned casing back pulling plasma cutting device and method based on axial constraint unlocking, belong to oil drilling technology field, including the cutting mechanism of vertical cutting and annular cutting to casing, the upper portion of cutting mechanism is provided with rotating mechanism, the upper portion of rotating mechanism is provided with centralizing mechanism;Cutting mechanism includes cutting shell and the several plasma cutting torch in the inside of cutting shell;During the falling process of cutting mechanism along casing, each plasma cutting torch is vertically cut to casing and forms a vertical slit, when rotating mechanism controls the rotation of cutting mechanism, plasma cutting torch is annularly cut to casing and forms annular slit.The application is cut to casing by implementing several vertical cutting and annular cutting along circumference, effectively destroys the complete cementing surface between casing and cement sheath, significantly weakens cementing force, realizes axial unlocking, so that the force required for pulling casing is greatly reduced, and then the requirement for pulling equipment power is reduced.

Description

Technical Field

[0001] This invention belongs to the field of oil drilling and production technology, specifically relating to a plasma cutting device and method for pulling back abandoned casing based on axial constraint unlocking. Background Technology

[0002] Oil and gas wells in the later stages of development are abandoned because they are no longer usable or have no value for further use, involving numerous well workover and sealing operations. Some oil and water wells require the removal of shallow surface casing for subsequent operations. For the removal of surface casing, hydraulic piling machines and other pulling equipment are mostly used. Before pulling, the casing to be removed needs to be separated from its lower portion. Current methods primarily involve using cutting tools to circumferentially cut the casing, separating it from the lower portion.

[0003] However, the existing cutting method, which only involves circumferential cutting of the casing, leaves the outer wall of the casing above the cut intact and bonded to the cement ring. This generates enormous bonding force and creates a significant axial locking effect. This not only requires extremely high pulling force for the casing pull-out operation and places stringent demands on equipment power, but also increases the overall difficulty and cost of the operation. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a plasma cutting device for the pullback of discarded sleeves based on axial constraint unlocking.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A plasma cutting device for pulling back discarded sleeves based on axial constraint unlocking includes a cutting mechanism for vertical and circumferential cutting of the sleeve, a rotating mechanism at the upper part of the cutting mechanism to control the rotation of the cutting mechanism, and a straightening mechanism at the upper part of the rotating mechanism.

[0007] The cutting mechanism includes a cutting shell and a plurality of plasma cutting guns located inside the cutting shell and evenly distributed along the circumference. The cutting shell is provided with a plurality of working windows corresponding one-to-one with the plasma cutting guns.

[0008] As the cutting mechanism descends along the sleeve, each plasma cutting torch makes a vertical cut on the sleeve, forming a vertical slit. When the rotating mechanism controls the cutting mechanism to rotate, the plasma cutting torch makes a circumferential cut on the sleeve, forming a circumferential slit.

[0009] Preferably, the plasma cutting torch includes a plasma nozzle and a distance control assembly for controlling the distance between the plasma nozzle and the inner wall of the casing.

[0010] The plasma nozzle includes an anode nozzle, the central axis of which intersects perpendicularly with the central axis of the cutting shell, and a discharge chamber extending through the anode nozzle along its axial direction is provided inside the anode nozzle; an anode base is coaxially fixed at one end of the anode nozzle near the central axis of the cutting shell, a distribution ring is coaxially fixed at the radial inner side of the anode base, a cathode base is coaxially fixed at the radial inner side of the distribution ring, and a cathode electrode extending into the discharge chamber is provided at one end of the cathode base near the anode nozzle;

[0011] The gun body rear seat is fixedly installed at the end of the anode base away from the anode nozzle, and the gun body rear seat is sealed to the distribution ring and the cathode base.

[0012] The anode base and the distribution ring are provided with an inlet air passage that extends to the discharge chamber;

[0013] The cathode electrode is provided with a cooling chamber, and the gun body is provided with a cooling water pipe and a return water pipe that connect to the cooling chamber.

[0014] Preferably, the radial outer wall of the distribution ring is provided with a plurality of annular grooves along the axial direction, and the axial end face of the distribution ring near the anode nozzle is provided with a plurality of vent holes that extend axially to each annular groove along the circumferential direction.

[0015] The anode base is provided with a vent pipe that extends into one of the annular grooves;

[0016] The interconnected vent pipe, annular groove, and vent hole form the air intake channel.

[0017] Preferably, a gun mount is provided inside the cutting shell;

[0018] The distance control assembly includes a distance control spring, one end of which is located on the rear seat of the gun body and the other end is located on the gun base. The compression direction of the distance control spring is parallel to the central axis of the anode nozzle.

[0019] A distance control ring is coaxially fixed at one end of the anode base near the anode nozzle. Two symmetrical distance control rods are provided on the distance control ring. The central axis of the distance control rods is parallel to the central axis of the anode nozzle. The ends of the distance control rods are provided with balls that can roll and cooperate with the inner wall of the sleeve.

[0020] A sliding sleeve is coaxially slidably fitted on the outer wall of the anode base, and the bottom end of the sliding sleeve is fixedly connected to the cutting shell through a bracket.

[0021] Preferably, the rotating mechanism includes a rotating housing and a chassis coaxially fixed to the bottom of the rotating housing. A rotating motor is provided on the upper part of the chassis. The output shaft of the rotating motor is coaxially fixedly connected to the rotating shaft. The rotating shaft passes downward through the chassis and is fixedly connected to the cutting mechanism.

[0022] Preferably, the straightening mechanism includes two straightening components arranged symmetrically above and below each other;

[0023] The straightening component includes a first connecting plate and a second connecting plate arranged coaxially. The first connecting plate of the upper straightening component is located above the second connecting plate, and the first connecting plate of the lower straightening component is located below the second connecting plate. The second connecting plate of the upper straightening component and the second connecting plate of the lower straightening component are coaxially attached and fixedly connected. The first connecting plate of the lower straightening component is fixedly connected to the rotating mechanism.

[0024] A plurality of upper conduits are evenly arranged along the circumferential direction between the two first connecting discs, and the upper conduits pass through the two second connecting discs in the vertical direction.

[0025] A sliding disk is coaxially arranged between adjacent first connecting disks and second connecting disks. Several connecting rod assemblies are evenly distributed along the circumferential direction between adjacent first connecting disks and sliding disks. The two ends of the connecting rod assembly are respectively hinged to the first connecting disk and the sliding disk. The connecting rod assembly includes two hinged straightening rods. A roller is provided on the hinge shaft between the two straightening rods.

[0026] A centering drive is provided between adjacent second connecting discs and sliding discs to push the rollers against the inner wall of the sleeve.

[0027] Preferably, the straightening drive includes a sliding shaft coaxially fixed between the centers of adjacent first connecting discs and second connecting discs, the sliding discs and the sliding shaft are slidably engaged, and a straightening compression spring is sleeved on the sliding shaft between adjacent sliding discs and second connecting discs.

[0028] Preferably, a straightening housing is coaxially fixed between the first connecting plate and the adjacent second connecting plate, and a straightening notch is provided at the position of the straightening housing facing the connecting rod assembly.

[0029] Preferably, a lifting ring plate is fixedly provided at the top of the straightening mechanism, and a lifting ring is provided on the lifting ring plate.

[0030] The present invention also provides a plasma cutting method for pulling back abandoned sleeves based on axial constraint unlocking.

[0031] The method for plasma cutting of discarded casing based on axial constraint unlocking is implemented using a plasma cutting device for pulling back discarded casing, and includes the following steps:

[0032] Step 1: Insertion of the waste sleeve pull-back plasma cutting device based on axial constraint unlocking;

[0033] The axial constraint unlocking-based abandoned casing pullback plasma cutting device is lifted by a winch and lowered to the abandoned wellhead. Then, external force is used to fully insert the straightening mechanism of the axial constraint unlocking-based abandoned casing pullback plasma cutting device into the wellhead. Then, it moves down from the wellhead position along the outer wall of the casing to the cutting start position by its own weight.

[0034] Step 2: Make a vertical cut on the inner wall of the casing to form a vertical slit;

[0035] Starting from the cutting start position, the waste casing pullback plasma cutting device based on axial constraint unlocking is lowered, and each plasma cutting torch is started at the same time. The plasma cutting torch makes vertical cuts on the inner wall of the casing to form multiple vertical cuts.

[0036] Step 3: Make a circumferential cut on the inner wall of the casing to form a circumferential slit;

[0037] After the waste sleeve pull-back plasma cutting device, which is unlocked based on axial constraint, is lowered to the designated circumferential cutting position, the rotating mechanism is started, and the plasma cutting torch rotates to perform circumferential cutting on the sleeve to form a circumferential slit.

[0038] Step 4: Device recovery process;

[0039] After the circumferential cutting is completed, the rotating mechanism and plasma cutting torch are turned off, and a winch is used to pull the waste sleeve pull-back plasma cutting device, which is unlocked based on axial constraints, out of the sleeve to complete the cutting work.

[0040] The beneficial effects of this invention are:

[0041] (1) This invention performs several vertical and circular cuts along the circumference of the sleeve. The increase in vertical cuts releases a large amount of heat during the cutting process. Due to the difference in heat transfer coefficient and thermal expansion coefficient between the sleeve and the cement ring, the heat released during the cutting process will cause different deformations between the sleeve and the cement ring. This leads to shearing and extrusion on the bonding surface of the sleeve and the cement ring, causing the interfacial bonding to fail and the bonding force to decrease, thereby reducing the pulling force required to pull the sleeve. On the other hand, the vertical cutting process can effectively destroy the stress coupling relationship between the sleeve and the cement layer, further reducing the bonding force between the sleeve and the cement ring, thereby further reducing the pulling force required to pull the sleeve. In other words, this invention effectively destroys the complete bonding surface between the sleeve and the cement ring by performing several vertical and circular cuts along the circumference of the sleeve, thereby significantly weakening the bonding force and achieving axial unlocking. This greatly reduces the force required to pull the sleeve, thereby reducing the power requirements of the pulling equipment.

[0042] (2) In this invention, the centering mechanism uses a centering spring as the core adjustment component, and the adaptive adjustment function of the centering mechanism is realized through the elastic deformation characteristics of the centering spring. This design can ensure that the centering mechanism always maintains dynamic centering inside the sleeve, providing stable posture guarantee for the plasma cutting process; even if there are irregular structures such as obstruction nodules on the inner wall of the sleeve, the buffering compensation effect of the centering spring can effectively avoid the problem of jamming failure of the centering mechanism, and significantly improve the reliability and adaptability of the cutting operation.

[0043] (3) In this invention, the distance between the anode nozzle and the inner wall of the sleeve along the central axis of the anode nozzle is the cutting distance between the anode nozzle and the sleeve. By pressing the ball on the inner wall of the sleeve and reasonably setting the distance between the central axis of the anode nozzle and the central axis of the control rod, and the distance between the ball and the anode nozzle along the central axis of the anode nozzle, the distance between the anode nozzle and the inner wall of the sleeve along the central axis of the anode nozzle can reach the optimal cutting distance, so as to cut a perfect kerf and successfully complete the cutting work. Attached Figure Description

[0044] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application.

[0045] Figure 1 This is a schematic perspective view of the structure of the waste sleeve pull-back plasma cutting device based on axial constraint unlocking of the present invention;

[0046] Figure 2 This is a schematic front view of the waste sleeve pull-back plasma cutting device based on axial constraint unlocking according to the present invention;

[0047] Figure 3 yes Figure 2 Sectional view along axis AA;

[0048] Figure 4 This is a schematic diagram of the cooperation between the rotary motor and the cutting mechanism in this invention;

[0049] Figure 5 This is a schematic perspective view of the plasma cutting torch structure inside the cutting mechanism of this invention;

[0050] Figure 6 This is a schematic front view of the plasma cutting torch within the cutting mechanism of the present invention;

[0051] Figure 7 yes Figure 6 BB-direction sectional view;

[0052] Figure 8 This is a schematic cross-sectional view of the structure of the plasma cutting torch of the present invention;

[0053] Figure 9 This is a schematic diagram of the distribution ring structure in this invention;

[0054] Figure 10 This is a schematic diagram of the straightening mechanism in this invention;

[0055] Figure 11 This is a schematic diagram of the straightening mechanism in this invention after removing the straightening outer shell;

[0056] Figure 12 This is a schematic diagram of the slit cut on the sleeve after cutting using the method of this invention;

[0057] in:

[0058] 1. Cutting mechanism; 11. Cutting housing; 111. Working window; 112. Wire hole; 12. Plasma cutting torch; 121. Anode nozzle; 122. Discharge chamber; 123. Anode base; 124. Distribution ring; 125. Cathode base; 126. Cathode electrode; 127. Torch body backrest; 128. Cooling water pipe; 129. Return water pipe; 1210. Annular groove; 1211. Vent hole; 1212. Vent pipe; 1213. Distance control spring; 1214. Distance control ring; 1215. Distance control rod; 1216. Ball bearing; 1217. Sliding sleeve; 1218. Support; 13. Torch base;

[0059] 2. Rotating mechanism; 21. Rotating housing; 22. Chassis; 23. Rotating motor; 24. Rotating shaft; 25. Lower conduit;

[0060] 3. Straightening mechanism; 31. First connecting plate; 32. Second connecting plate; 33. Upper conduit; 34. Linkage assembly; 341. Straightening link; 342. Roller; 35. Sliding plate; 36. Sliding shaft; 37. Straightening compression spring; 38. Straightening housing; 381. Straightening notch; 39. Lifting ring plate; 391. Lifting ring;

[0061] 4. Vertical cut; 5. Circumferential cut. Detailed Implementation

[0062] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0063] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0064] In this invention, terms such as "upper," "lower," "bottom," and "top" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are merely relational terms determined for the convenience of describing the structural relationship of the various components or elements of this invention, and do not specifically refer to any component or element in this invention, and should not be construed as limiting this invention.

[0065] In this invention, terms such as "connected" and "linked" should be interpreted broadly, indicating a fixed connection, an integral connection, or a detachable connection; a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can determine the specific meaning of these terms in this invention based on the specific circumstances, and they should not be construed as limitations on the invention.

[0066] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0067] Example 1:

[0068] like Figures 1-11 As shown, the waste sleeve pull-back plasma cutting device based on axial constraint unlocking includes a cutting mechanism 1 for vertical and circumferential cutting of the sleeve, a rotating mechanism 2 is provided on the upper part of the cutting mechanism 1, the rotating mechanism 2 controls the cutting mechanism 1 to rotate, and a straightening mechanism 3 is provided on the upper part of the rotating mechanism 2.

[0069] The cutting mechanism 1 includes a cutting shell 11 and a plurality of plasma cutting guns 12 located inside the cutting shell 11 and evenly distributed along the circumference. The cutting shell 11 is provided with a plurality of working windows 111 corresponding one-to-one with the plasma cutting guns 12.

[0070] During the process of the cutting mechanism 1 falling along the sleeve, each plasma cutting torch 12 makes a vertical cut on the sleeve to form a vertical slit 4. When the rotating mechanism 2 controls the cutting mechanism 1 to rotate, the plasma cutting torch 12 makes a circumferential cut on the sleeve to form a circumferential slit 5.

[0071] Preferably, the plasma cutting torch 12 includes a plasma nozzle and a distance control assembly for controlling the distance between the plasma nozzle and the inner wall of the sleeve.

[0072] The plasma nozzle includes an anode nozzle 121, the central axis of which intersects perpendicularly with the central axis of the cutting housing 11. A discharge chamber 122 is provided inside the anode nozzle 121 and extends through it along its axial direction. An anode base 123 is coaxially fixed at one end of the anode nozzle 121 near the central axis of the cutting housing 11. A distribution ring 124 is coaxially fixed at the radial inner side of the anode base 123. A cathode base 125 is coaxially fixed at the radial inner side of the distribution ring 124. A cathode electrode 126 extending into the discharge chamber 122 is provided at one end of the cathode base 125 near the anode nozzle 121.

[0073] The end of the anode base 123 away from the anode nozzle 121 is fixedly provided with the gun body rear seat 127, and the gun body rear seat 127 is sealed to the distribution ring 124 and the cathode base 125.

[0074] The anode base 123 and the distribution ring 124 are provided with an air inlet channel that extends to the discharge chamber 122;

[0075] The cathode electrode 126 is provided with a cooling chamber inside, and the gun body rear seat 127 is provided with a cooling water pipe 128 and a return water pipe 129 that are connected to the cooling chamber.

[0076] The plasma cutting process:

[0077] First, working gas is introduced into the discharge chamber 122 through the inlet gas channel, and cooling water is injected into the cooling chamber of the cathode electrode 126 through the cooling water pipe 128 and returned through the return water pipe 129 to achieve cooling of the cooling chamber by the cooling water.

[0078] Then, the positive terminal of the plasma power supply is connected to the anode nozzle 121 and the negative terminal is connected to the cathode electrode 126. The plasma power supply releases a high-frequency high-voltage pulse to break down the gas in the discharge chamber 122 between the cathode electrode 126 and the anode nozzle 121, forming a plasma discharge. Under the carrying of the compressed gas, the ion arc between the cathode electrode 126 and the anode nozzle 121 is blown out of the torch, forming a high-temperature and high-pressure plasma beam, which achieves ignition.

[0079] Then, the positive terminal of the plasma power supply is connected to the sleeve. After successful ignition, the high-temperature plasma arc continues to act on the surface of the sleeve, rapidly eroding and removing the non-conductive layer on its surface. At this time, the current between the cathode electrode 126 and the anode nozzle 121 is cut off, and the sleeve is connected to the current circuit. The plasma arc is transferred to the discharge between the cathode electrode 126 and the sleeve, completing the transfer of the anode arc root. After the anode arc root transfer is completed, the sleeve material is rapidly removed until the sleeve is penetrated, and then the cutting operation is performed.

[0080] Therefore, in this application, the arc ignition operation is achieved by connecting the positive electrode of the plasma power supply to the anode nozzle 121 and the negative electrode to the cathode electrode 126; after successful ignition, the positive electrode of the plasma power supply is connected to the sleeve, and high-speed cutting is performed by using the transfer arc method, thereby improving cutting efficiency and reducing anode loss.

[0081] Preferably, the radial outer side wall of the distribution ring 124 is provided with a plurality of annular grooves 1210 along the axial direction, and the axial end face of the distribution ring 124 near the anode nozzle 121 is provided with a plurality of vent holes 1211 that extend axially to each annular groove 1210.

[0082] The anode base 123 is provided with a vent pipe 1212 that extends into one of the annular grooves 1210;

[0083] The interconnected vent pipe 1212, annular groove 1210, and vent hole 1211 form an air intake channel.

[0084] Specifically, two annular grooves 1210 are axially arranged on the radially outer side wall of the distribution ring 124. The two annular grooves 1210 divide the distribution ring 124 into a first annular portion near the anode nozzle 121, a second annular portion between the two annular grooves 1210, and a third annular portion away from the anode nozzle 121. The annular groove 1210 away from the anode nozzle 121 is connected to the vent pipe 1212. The number of vent holes 1211 on the first annular portion is greater than the number of vent holes 1211 on the second annular portion. In order to facilitate the processing of the vent holes 1211 on the second annular portion, the axial end face of the third annular portion away from the anode nozzle 121 passes through the second annular portion axially to form the vent holes 1211 on the second annular portion. Therefore, a corresponding channel is also formed on the third annular portion. However, since the end of the third annular portion away from the anode nozzle 121 is sealed with the gun body rear seat 127, gas will not leak from the channel on the third annular portion.

[0085] Preferably, a gun mount 13 is provided inside the cutting shell 11;

[0086] The distance control assembly includes a distance control spring 1213, one end of which is located on the gun body rear seat 127 and the other end is located on the gun base 13. The compression direction of the distance control spring 1213 is parallel to the central axis of the anode nozzle 121.

[0087] A distance control ring 1214 is coaxially fixed at one end of the anode base 123 near the anode nozzle 121. Two symmetrical distance control rods 1215 are provided on the distance control ring 1214. The central axis of the distance control rods 1215 is parallel to the central axis of the anode nozzle 121. The ends of the distance control rods 1215 are provided with ball bearings 1216 that can roll with the inner wall of the sleeve.

[0088] A sliding sleeve 1217 is coaxially slidably fitted on the outer wall of the anode base 123, and the bottom end of the sliding sleeve 1217 is fixedly connected to the cutting shell 11 through a bracket 1218. The bracket 1218 is a telescopic frame.

[0089] In this application, the distance control spring 1213 causes the ball 1216 to press against the inner wall of the sleeve. When the distance between the central axis of the anode nozzle 121 and the central axis of the distance control rod 1215 is... The distance between the farthest end of the ball bearing 1216 and the anode nozzle 121 along the central axis of the anode nozzle 121 is... The inner radius of the casing is At that time, the distance between the anode nozzle 121 and the inner wall of the casing along the central axis of the anode nozzle 121 for The distance between the anode nozzle 121 and the inner wall of the casing along the central axis of the anode nozzle 121. The cutting distance between the anode nozzle 121 and the sleeve is determined by pressing the ball bearing 1216 against the inner wall of the sleeve and setting it appropriately. , Value, can make The value reaches the optimal cutting distance to cut a perfect kerf and successfully complete the cutting work.

[0090] Preferably, the rotating mechanism 2 includes a rotating housing 21 and a chassis 22 coaxially fixed to the bottom of the rotating housing 21. A rotating motor 23 is provided on the upper part of the chassis 22. The output shaft of the rotating motor 23 is coaxially fixedly connected to a rotating shaft 24. The rotating shaft 24 passes downward through the chassis 22 and is fixedly connected to the cutting mechanism 1. Specifically, the rotating shaft 24 is fixedly connected to the cutting housing 11, and the rotating shaft 24 and the chassis 22 rotate together.

[0091] Preferably, the straightening mechanism 3 includes two straightening components arranged symmetrically at different heights;

[0092] The straightening assembly includes a first connecting plate 31 and a second connecting plate 32 arranged coaxially. The first connecting plate 31 of the upper straightening assembly is located above the second connecting plate 32, and the first connecting plate 31 of the lower straightening assembly is located below the second connecting plate 32. The second connecting plate 32 of the upper straightening assembly and the second connecting plate 32 of the lower straightening assembly are coaxially attached and fixedly connected. The first connecting plate 31 of the lower straightening assembly is fixedly connected to the rotating mechanism 2. Specifically, the first connecting plate 31 of the lower straightening assembly is coaxially fixedly connected to the rotating housing 21.

[0093] A plurality of upper conduits 33 are evenly arranged between the two first connecting discs 31 along the circumferential direction, and the upper conduits 33 pass through the two second connecting discs 32 in the vertical direction.

[0094] A sliding disk 35 is coaxially arranged between adjacent first connecting disks 31 and second connecting disks 32. Several connecting rod assemblies 34 are evenly distributed along the circumferential direction between adjacent first connecting disks 31 and sliding disks 35. The two ends of the connecting rod assembly 34 are respectively hinged to the first connecting disk 31 and the sliding disk 35. The connecting rod assembly 34 includes two hinged straightening rods 341. A roller 342 is arranged on the hinge shaft between the two straightening rods 341.

[0095] A centering drive is provided between the adjacent second connecting disc 32 and sliding disc 35 to press the roller 342 against the inner wall of the sleeve.

[0096] Preferably, the straightening drive component includes a sliding shaft 36 coaxially fixed between the centers of adjacent first connecting discs 31 and second connecting discs 32. The sliding discs 35 are in sliding engagement with the sliding shaft 36, and a straightening compression spring 37 is sleeved on the sliding shaft 36 between adjacent sliding discs 35 and second connecting discs 32. The sliding discs 35 are in sliding engagement with both the upper conduit 33 and the sliding shaft 36.

[0097] The straightening spring 37 causes the sliding disc 35 to approach the corresponding first connecting disc 31, thereby causing the hinge of the connecting rod assembly 34 to bend outward, which in turn causes the roller 342 to press against the inner wall of the sleeve. In this application, the straightening mechanism 3 achieves non-powered straightening through the connecting rod assembly 34 and the straightening spring 37, and can adapt to the inner diameter of the sleeve.

[0098] In this application, the centering mechanism 3 uses a centering spring 37 as the core adjustment component, and the adaptive adjustment function of the centering mechanism 3 is realized through the elastic deformation characteristics of the centering spring 37. This design can ensure that the centering mechanism 3 always maintains dynamic centering inside the casing, providing stable posture guarantee for the plasma cutting process; even if there are irregular structures such as obstructions on the inner wall of the casing, the buffering compensation effect of the centering spring 37 can effectively avoid the problem of jamming failure of the centering mechanism 3, significantly improving the reliability and adaptability of the cutting operation.

[0099] Preferably, a straightening housing 38 is coaxially fixed between the first connecting plate 31 and the adjacent second connecting plate 32, and a straightening notch 381 is provided on the straightening housing 38 at the position opposite to the connecting rod assembly 34.

[0100] Preferably, a lifting ring plate 39 is fixedly provided at the top of the straightening mechanism 3, and a lifting ring 391 is provided on the lifting ring plate 39.

[0101] In this application, the upper conduit 33 extends upward through the lifting ring plate 39. Several lower conduits 25, aligned vertically with the upper conduit 33, are evenly arranged along the circumference of the chassis 22. The aligned upper conduits 33 and lower conduits 25 are connected by a flexible tube (not shown in the attached drawings). Several wire-passing holes 112, corresponding one-to-one with the lower conduits 25, are provided on the top of the cutting shell 11. The number of wire-passing holes 112 is the same as the number of plasma cutting torches 12. The interconnected upper conduit 33, flexible tube, lower conduit 25, and one of the wire-passing holes 112 combine to form a wire-passing channel. Each wire-passing channel corresponds one-to-one with a corresponding plasma cutting torch 12. The electrical wires, gas lines, and water lines required for the plasma cutting torch 12 are all arranged within the corresponding wire-passing channels. In addition, in this application, the cutting mechanism 1 includes three plasma cutting torches 12. During circumferential cutting, each plasma cutting torch 12 needs to rotate 120°. Therefore, the wires, gas lines, and water lines required for the plasma cutting torches 12 have a certain amount of redundancy to accommodate the rotation of the cutting mechanism 1.

[0102] Example 2:

[0103] The waste sleeve pullback plasma cutting method based on axial constraint unlocking is implemented using the waste sleeve pullback plasma cutting device based on axial constraint unlocking in Example 1, and includes the following steps:

[0104] Step 1: Insertion of the waste sleeve pull-back plasma cutting device based on axial constraint unlocking;

[0105] The axial constraint-unlocked abandoned casing pullback plasma cutting device is lifted by a winch and lowered to the abandoned wellhead. Then, external force is used to fully insert the straightening mechanism 3 of the axial constraint-unlocked abandoned casing pullback plasma cutting device into the wellhead. Then, it moves down from the wellhead position along the outer wall of the casing to the cutting start position by its own weight. The height of the cutting start position from the top of the casing to be cut is 10-15 mm.

[0106] Step 2: Make a vertical cut on the inner wall of the casing to form a vertical slit 4;

[0107] Starting from the cutting start position, the waste casing pullback plasma cutting device based on axial constraint unlocking is lowered, and each plasma cutting torch 12 is started at the same time. The plasma cutting torch 12 vertically cuts the inner wall of the casing to form multiple vertical cuts 4.

[0108] The startup process of plasma cutting torch 12 is as follows:

[0109] Working gas is introduced into the discharge chamber 122 through the inlet gas channel, and cooling water is injected into the cooling chamber of the cathode electrode 126 through the cooling water pipe 128 and returned through the return water pipe 129, so as to achieve cooling of the cooling chamber by the cooling water.

[0110] The positive terminal of the plasma power supply is connected to the anode nozzle 121, and the negative terminal is connected to the cathode electrode 126 for ignition.

[0111] After ignition, connect the positive terminal of the plasma power supply to the sleeve to start the plasma cutting torch 12.

[0112] Step 3: Make a circumferential cut on the inner wall of the casing to form a circumferential slit 5;

[0113] After the waste sleeve pull-back plasma cutting device based on axial constraint unlocking is lowered to the designated circumferential cutting position, the rotating mechanism 2 is started, and the plasma cutting torch 12 rotates to perform circumferential cutting on the sleeve to form a circumferential cut 5.

[0114] Step 4: Device recovery process;

[0115] After the circumferential cutting is completed, the rotating mechanism 2 and the plasma cutting torch 12 are turned off. A winch is used to pull the discarded casing back up from the casing using the axially constrained unlocking plasma cutting device, completing the cutting operation. After cutting, the cut on the casing is as follows: Figure 12 As shown.

[0116] The closing process of the plasma cutting torch 12 is as follows:

[0117] Turn off the plasma power supply, then stop supplying the working gas into the discharge chamber 122, and finally stop injecting cooling water into the cooling chamber of the cathode electrode 126.

[0118] This invention involves making several vertical and circular cuts along the circumference of the sleeve. The increased vertical cuts release a significant amount of heat during the cutting process. Due to the difference in heat transfer and thermal expansion coefficients between the sleeve and the cement ring, the heat released during cutting causes different deformations in the sleeve and cement ring. This leads to shearing and compression at the bonding surface of the sleeve and cement ring, causing interfacial bonding failure and reducing the bonding force, thus lowering the pull-out force required to pull the sleeve. Furthermore, the vertical cuts effectively disrupt the stress coupling relationship between the sleeve and the cement layer, further reducing the bonding force between the sleeve and the cement ring, thereby further reducing the pull-out force required to pull the sleeve. In short, this invention, by performing several vertical and circular cuts along the circumference of the sleeve, effectively disrupts the intact bonding surface between the sleeve and the cement ring, significantly weakening the bonding force and achieving axial unlocking. This greatly reduces the force required to pull the sleeve, thereby reducing the power requirements of the pulling equipment.

[0119] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, they are not intended to limit the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A plasma cutting device for pulling back discarded sleeves based on axial constraint unlocking, characterized in that, The device includes a cutting mechanism for vertical and circumferential cutting of the sleeve, a rotating mechanism at the upper part of the cutting mechanism, the rotating mechanism controlling the cutting mechanism to rotate, and a straightening mechanism at the upper part of the rotating mechanism. The cutting mechanism includes a cutting shell and a plurality of plasma cutting guns located inside the cutting shell and evenly distributed along the circumference. The cutting shell is provided with a plurality of working windows corresponding one-to-one with the plasma cutting guns. During the process of the cutting mechanism falling along the sleeve, each plasma cutting torch makes a vertical cut on the sleeve to form a vertical slit. When the rotating mechanism controls the cutting mechanism to rotate, the plasma cutting torch makes a circumferential cut on the sleeve to form a circumferential slit. The plasma cutting torch includes a plasma nozzle and a distance control assembly for controlling the distance between the plasma nozzle and the inner wall of the casing. The plasma nozzle includes an anode nozzle, the central axis of which intersects perpendicularly with the central axis of the cutting shell, and a discharge chamber extending through the anode nozzle along its axial direction is provided inside the anode nozzle; an anode base is coaxially fixed at one end of the anode nozzle near the central axis of the cutting shell, a distribution ring is coaxially fixed at the radial inner side of the anode base, a cathode base is coaxially fixed at the radial inner side of the distribution ring, and a cathode electrode extending into the discharge chamber is provided at one end of the cathode base near the anode nozzle; The gun body rear seat is fixedly installed at the end of the anode base away from the anode nozzle, and the gun body rear seat is sealed to the distribution ring and the cathode base. The anode base and the distribution ring are provided with an inlet air passage that extends to the discharge chamber; The cathode electrode is provided with a cooling chamber, and the gun body rear seat is provided with a cooling water pipe and a return water pipe that connect to the cooling chamber. A gun mount is provided inside the cutting shell; The distance control assembly includes a distance control spring, one end of which is located on the rear seat of the gun body and the other end is located on the gun base. The compression direction of the distance control spring is parallel to the central axis of the anode nozzle. A distance control ring is coaxially fixed at one end of the anode base near the anode nozzle. Two symmetrical distance control rods are provided on the distance control ring. The central axis of the distance control rods is parallel to the central axis of the anode nozzle. The ends of the distance control rods are provided with balls that can roll and cooperate with the inner wall of the sleeve. A sliding sleeve is coaxially slidably fitted on the outer wall of the anode base, and the bottom end of the sliding sleeve is fixedly connected to the cutting shell through a bracket.

2. The plasma cutting device for pulling back discarded sleeves based on axial constraint unlocking as described in claim 1, characterized in that, The radial outer wall of the distribution ring is provided with several annular grooves along the axial direction, and the axial end face of the distribution ring near the anode nozzle is provided with several vent holes that extend axially to each annular groove. The anode base is provided with a vent pipe that extends into one of the annular grooves; The interconnected vent pipe, annular groove, and vent hole form the air intake channel.

3. The plasma cutting device for pulling back discarded sleeves based on axial constraint unlocking as described in claim 1, characterized in that, The rotating mechanism includes a rotating housing and a chassis coaxially fixed to the bottom of the rotating housing. A rotating motor is provided on the upper part of the chassis. The output shaft of the rotating motor is coaxially fixedly connected to the rotating shaft. The rotating shaft passes downward through the chassis and is fixedly connected to the cutting mechanism.

4. The plasma cutting device for pulling back discarded sleeves based on axial constraint unlocking as described in claim 1, characterized in that, The straightening mechanism includes two straightening components arranged symmetrically at different heights; The straightening component includes a first connecting plate and a second connecting plate arranged coaxially. The first connecting plate of the upper straightening component is located above the second connecting plate, and the first connecting plate of the lower straightening component is located below the second connecting plate. The second connecting plate of the upper straightening component and the second connecting plate of the lower straightening component are coaxially attached and fixedly connected. The first connecting plate of the lower straightening component is fixedly connected to the rotating mechanism. A plurality of upper conduits are evenly arranged along the circumferential direction between the two first connecting discs, and the upper conduits pass through the two second connecting discs in the vertical direction. A sliding disk is coaxially arranged between adjacent first connecting disks and second connecting disks. Several connecting rod assemblies are evenly distributed along the circumferential direction between adjacent first connecting disks and sliding disks. The two ends of the connecting rod assembly are respectively hinged to the first connecting disk and the sliding disk. The connecting rod assembly includes two hinged straightening rods. A roller is provided on the hinge shaft between the two straightening rods. A centering drive is provided between adjacent second connecting discs and sliding discs to push the rollers against the inner wall of the sleeve.

5. The plasma cutting device for pulling back discarded sleeves based on axial constraint unlocking as described in claim 4, characterized in that, The straightening drive includes a sliding shaft coaxially fixed between the centers of adjacent first connecting discs and second connecting discs. The sliding discs and the sliding shaft are in sliding engagement. A straightening compression spring is sleeved on the sliding shaft between adjacent sliding discs and second connecting discs.

6. The plasma cutting device for pulling back discarded sleeves based on axial constraint unlocking as described in claim 4, characterized in that, A straightening housing is coaxially fixed between the first connecting plate and the adjacent second connecting plate, and a straightening notch is provided at the position of the straightening housing facing the connecting rod assembly.

7. The plasma cutting device for pulling back discarded sleeves based on axial constraint unlocking as described in claim 1, characterized in that, The top of the straightening mechanism is fixedly equipped with a lifting ring plate, and the lifting ring plate is provided with lifting rings.

8. A method for plasma cutting of discarded sleeves based on axial constraint unlocking, implemented using the plasma cutting apparatus for discarded sleeves based on axial constraint unlocking as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Step 1: Insertion of the waste sleeve pull-back plasma cutting device based on axial constraint unlocking; The axial constraint unlocking-based abandoned casing pullback plasma cutting device is lifted by a winch and lowered to the abandoned wellhead. Then, external force is used to fully insert the straightening mechanism of the axial constraint unlocking-based abandoned casing pullback plasma cutting device into the wellhead. Then, it moves down from the wellhead position along the outer wall of the casing to the cutting start position by its own weight. Step 2: Make a vertical cut on the inner wall of the casing to form a vertical slit; Starting from the cutting start position, the waste casing pullback plasma cutting device based on axial constraint unlocking is lowered, and each plasma cutting torch is started at the same time. The plasma cutting torch makes vertical cuts on the inner wall of the casing to form multiple vertical cuts. Step 3: Make a circumferential cut on the inner wall of the casing to form a circumferential slit; After the waste sleeve pull-back plasma cutting device, which is unlocked based on axial constraint, is lowered to the designated circumferential cutting position, the rotating mechanism is started, and the plasma cutting torch rotates to perform circumferential cutting on the sleeve to form a circumferential slit. Step 4: Device recovery process; After the circumferential cutting is completed, the rotating mechanism and plasma cutting torch are turned off, and a winch is used to pull the waste sleeve pull-back plasma cutting device, which is unlocked based on axial constraints, out of the sleeve to complete the cutting work.

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