CN211258545U

CN211258545U - Plasma cutting device for underground oil casing

Info

Publication number: CN211258545U
Application number: CN201921460085.6U
Authority: CN
Inventors: 张瑞霞; 刘永顺; 张化强; 周景彩; 田浩然
Original assignee: China Petroleum and Chemical Corp; Sinopec Research Institute of Petroleum Engineering Shengli Co
Current assignee: China Petroleum and Chemical Corp; Sinopec Research Institute of Petroleum Engineering Shengli Co
Priority date: 2019-09-04
Filing date: 2019-09-04
Publication date: 2020-08-14
Anticipated expiration: 2029-09-04

Abstract

The utility model discloses an oil casing plasma cutting device in pit, including electrode, electrode feed mechanism, guide shoe, the electrode is fixed on electrode feed mechanism to the electrode radially sets up outwards, the axial lower extreme at electrode feed mechanism is connected to the guide shoe, electrode, the equal connecting cable of electrode feed mechanism. The upper end of the electrode feeding mechanism is connected with the rotating mechanism. The upper end of the rotating mechanism is connected with an upper righting mechanism. And a lower righting mechanism is also connected between the guide shoe and the electrode feeding mechanism. The utility model discloses the realization is to the cutting of tubular column, and cutting efficiency is high, the success rate is high.

Description

Plasma cutting device for underground oil casing

Technical Field

The utility model belongs to the technical field of the device cutting technique in the pit and specifically relates to an oil casing pipe plasma cutting device in pit.

Background

The blocking of the underground pipe column is one of the important reasons for the major repair of the oil well, and the recovery of the casing passage is mainly realized by adopting a salvaging mode aiming at the blocked pipe column. To the circumstances such as the tubular column sand is buried seriously, the unable deblocking of packer, can cause fishing power too big, surpasss workover rig, fishing tool or tubular column and holds and draw the limit, to this kind of circumstances, generally takes the mode of cutting salvage to realize the segmentation salvage, reduces fishing power. Currently, the main cutting modes of oil fields include mechanical cutting, sand blasting cutting and the like. The mechanical cutting is the most traditional cutting mode, and has the problems of serious cutter abrasion, larger cutting force, low cutting efficiency and the like; the sand blasting cutting has the defects of high cost, complex ground equipment, huge sand mixing system and the like.

Application No.: 201710844232.9 discloses an automatic rotary sand blasting cutting device and method for coiled tubing, the tubing string comprises coiled tubing, an anchor, a rotary sand blasting cutter connected in turn from top to bottom, the rotary sand blasting cutter comprises a cutting head, a nozzle, a rotary mechanism, the lower end of the rotary mechanism is connected with the cutting head, the cutting head is provided with a radial spray hole, the nozzle is arranged in the radial spray hole, and the axis of the nozzle has an eccentric distance with the central axis of the central hole of the cutting head. The discharge capacity of the cutter is not limited by underground tools such as a screw drill and the like during cutting operation, the jet flow cutting range of the cutter is large, and the cutter is suitable for simultaneous cutting of multiple layers of pipe columns and cutting of thick-wall pipe columns.

Application No.: 201420850662.3 is a downhole pipe column cutting device, which is suitable for downhole pipe column salvaging, especially for sectional cutting salvaging of sand-blocking sand screen, and can realize the next time of completing two operations of cutting and salvaging, shortening the construction time, improving the operation efficiency and reducing the production cost. The tool comprises a cutting mechanism, a centering mechanism and a central rod, wherein the cutting mechanism and the centering mechanism are both installed on the central rod, a setting and unsealing reversing track is arranged on the central rod, a setting mechanism is further installed between the cutting mechanism and the centering mechanism, and the setting mechanism is connected with the cutting mechanism through slips. The device is connected to the bottom of a downhole tubular column, the upper part of the device is connected with a ground driving device through a drill string or a common oil pipe, and then the downhole tubular column is lowered to a designed position. The utility model discloses accessible location oil pipe with drag for the lance and be connected, realize that the operation of cutting and salvaging just can be accomplished to next tubular column, reduced the number of times of playing the tubular column, fundamentally has shortened construction cycle for the recovery of old well is put into operation.

Application No.: 201410834622.4 is an integrated tool for cutting and salvaging underground pipe column and its construction method, which is suitable for salvaging underground pipe column, especially for sectional cutting and salvaging of sand-blocking sand screen pipe, and can realize the next time of completing two operations of cutting and salvaging, shortening construction time, improving operation efficiency and reducing production cost. This instrument includes cutting device and drags for the lance, and cutting device is equipped with cutting mechanism, rights mechanism and well core rod, and cutting mechanism all installs on well core rod with right the mechanism, drags for the lance and is equipped with salvages the pole. The cutting device is connected with the fishing spear through a positioning oil pipe, a setting and unsealing reversing track is arranged on a center rod of the cutting device, a setting mechanism is further installed between the cutting mechanism and the righting mechanism, and the setting mechanism is connected with the cutting mechanism through slips. The fishing spear, the positioning oil pipe and the cutting device are connected to the bottom of the downhole tubular column, the upper part of the cutting spear is connected with the ground driving device through the drill rod column or the common oil pipe, and then the downhole tubular column is lowered to a designed position.

Technical scheme and the technical problem that will solve and the beneficial effect who produces of above disclosure technique all with the utility model discloses inequality, to the utility model discloses more technical characteristics and the technical problem and the beneficial effect that will solve all do not have the technological inspiration in the above technical document that discloses.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide an oil casing pipe plasma cutting device in pit, for solving the mechanical cutting that tubular column is used always in the pit and the problem that the sandblast cutting mode exists, use the plasma processing means among the machining in the tubular column cutting in the pit, carry out tubular column plasma cutting in the pit. The plasma cutting process of the underground pipe column utilizes a tool and the underground pipe column to respectively form a tool electrode and a pipe column electrode, high-temperature plasma is generated by discharging between a positive electrode and a negative electrode, the temperature of an instant high-temperature heat source can reach thousands of degrees or even tens of thousands of degrees, the temperature of the pipe column is sharply increased to the melting point or even the boiling point of a material, the metal material is melted and vaporized, and the cutting of the pipe column is realized. The plasma cutting efficiency of the underground pipe column is high, and the success rate is high.

In order to achieve the above object, the utility model provides a following technical scheme, a well oil casing plasma cutting device, including electrode, electrode feed mechanism, guide shoe, the electrode is fixed on electrode feed mechanism to the electrode radially sets up outwards, the axial lower extreme at electrode feed mechanism is connected to the guide shoe, electrode feed mechanism all connecting cable.

The upper end of the electrode feeding mechanism is connected with the rotating mechanism.

The upper end of the rotating mechanism is connected with an upper righting mechanism.

And a lower righting mechanism is also connected between the guide shoe and the electrode feeding mechanism.

The electrode feeding mechanism comprises an upper fixed disc, a stepping motor, a driven shaft, a motor fixing plate, a driving gear, a shell, a driven synchronous wheel, a belt, a lower fixed disc, an electrode push block, a driving synchronous wheel, a driven gear and a driving shaft, wherein the upper fixed disc is fixed on the inner wall of the shell, the stepping motor is fixed on the motor fixing plate, the motor fixing plate is fixed on the upper fixed disc, the driving gear is arranged on an output shaft of the stepping motor, the driven gear and the driving synchronous wheel are arranged on the driving shaft, the driving gear is meshed with the driven gear, the driving shaft and the driven shaft are arranged between the upper fixed disc and the lower fixed disc, the driven synchronous wheel is arranged on the driven shaft, the belt is arranged on the driving synchronous wheel and the driven synchronous wheel, the electrode push block is fixed on the belt, and the electrode, the electrode fixing device is characterized in that the shell is provided with radial holes for extending electrodes, the lower fixing disc is fixed on the shell through screws, the upper end cover is connected to the upper end of the shell, and the flange plate is fixed on the upper end cover.

The electrode feeding mechanism further comprises a long stud bolt, the upper end of the long stud bolt is mounted on the upper fixed disk through a nut, and the lower end of the long stud bolt is connected with the lower fixed disk.

The rotating mechanism comprises an adapter, a rotating motor, a rotating mechanism shell, a motor supporting plate, a coupler, a conduit, a bearing and a lower end cover; the upper part of the shell of the rotating mechanism is in threaded connection with the adapter, and the lower part of the shell of the rotating mechanism is in threaded connection with the lower end cover; the rotating motor, the rotating mechanism shell, the motor supporting plate, the coupler and the conduit are arranged inside the rotating mechanism shell; the motor supporting plate is fixed with the shell of the rotating mechanism, the rotating motor is fixed on the motor supporting plate, an output shaft of the rotating motor is connected with the hollow conduit through a coupler, the bearing is fixed in an inner hole of the lower end cover and sleeved on the outer wall of the hollow conduit, and the whole rotating mechanism is connected with a flange plate of the feeding mechanism through the tail end of the hollow conduit.

The upper centering mechanism or the lower centering mechanism comprises a middle screw rod, an upper compression nut, an upper compression spring, a movable block, a support rod, a connecting sheet, a centering roller, a lower compression spring, a lower compression nut, a fixed block, a base, an upper top cover and a centering mechanism shell; the upper port of the shell of the righting mechanism is connected with a top cover of the righting mechanism, the lower port of the shell of the righting mechanism is connected with a base, an upper compression nut, a lower compression nut, an upper compression spring and a lower compression spring are all sleeved outside a middle screw rod, the upper compression nut is fixed above the upper compression spring, the lower compression nut is positioned below the lower compression spring, the lower compression nut is fixed above a fixed block, the fixed block is fixed on the base, a bearing is arranged in an inner hole of a movable block, the bearing is sleeved on the middle screw rod, the movable block is positioned between the upper compression spring and the lower compression spring, the support rod comprises an upper support rod and a lower support rod, the upper end of the connection piece is hinged with the lower end of the upper support rod, the upper end of the upper support rod is hinged with the movable block, the lower end of the lower support rod is hinged with the fixed block, the righting roller is arranged on the connection piece, the movable block, the supporting rod, the connecting sheet, the righting roller and the fixed block are connected with each other to form a connecting rod mechanism.

The centralizing rollers are at least provided with one group.

The upper righting mechanism is connected with the rotating mechanism through a conversion joint; and a conversion joint is additionally arranged between the electrode feeding mechanism and the lower righting mechanism to realize connection.

Compared with the prior art, the utility model following beneficial effect has:

in the first preferred embodiment, the downhole cutting string mainly comprises a cable, an electrode feeding mechanism, a guide shoe and the like. The plasma cutting process is that after the cable carrying tool string enters the specified position inside the oil/casing pipe, positive and negative voltages are applied between the underground oil/casing pipe and the tool electrode, the electrode in the electrode feeding mechanism is controlled by the servo system to move towards the inner wall of the pipe column continuously, when the electrode and the inner wall of the pipe column reach a certain gap, violent plasma discharge occurs, and under the action of the high temperature and high pressure of the plasma discharge, the pipe column material is removed. The annular cutting of the underground oil/casing pipe is realized by rotating the electrode feeding mechanism through equipment such as a ground turntable and the like.

In order to improve the cutting performance of the oil/casing string in the downhole, a second preferred embodiment is provided, the downhole cutting string mainly comprises a cable, a rotating mechanism, an electrode feeding mechanism, a guide shoe and the like, and the rotating mechanism is added on the basis of the first preferred embodiment. The rotating mechanism is internally provided with a rotating motor, the rotating motor is driven to rotate after the cable provides power, the electrode feeding mechanism is driven to do circumferential rotating motion, the electrode rotates for a circle around the inner wall of the pipe column to perform circumferential cutting, and the pipe column is cut off.

In order to improve the neutrality of downhole oil/casing string cutting, a third preferred embodiment and a fourth preferred embodiment are provided, the downhole cutting string mainly comprises a cable, a centering mechanism, a rotating mechanism, an electrode feeding mechanism, a guide shoe and the like, the third preferred embodiment and the fourth preferred embodiment are additionally provided with the centering mechanism on the basis of the second preferred embodiment, and the centering mechanisms of the third preferred embodiment and the fourth preferred embodiment are respectively arranged at the upper end of the rotating mechanism and the lower end of the electrode feeding mechanism. The centering mechanism ensures the centering state of the plasma cutting device, ensures that the cut pipe column realizes synchronous cutting in thickness, and the cutting is more uniform.

In order to further improve the centering performance of cutting in the case of oil/casing string blocking in the underground, a fifth preferred embodiment is provided, the underground cutting pipe column mainly comprises a cable, an upper centering mechanism, a rotating mechanism, an electrode feeding mechanism, a lower centering mechanism guide shoe and the like, one centering mechanism is additionally arranged on the basis of a third preferred embodiment and a fourth preferred embodiment, and the upper centering mechanism and the lower centering mechanism enable the cutting pipe column to be better in centering performance and better in cutting effect.

In the preferred embodiments, the guide shoe ensures the running-in property of the pipe column when running; the electrode feeding mechanism realizes the annular feeding and retreating of the electrode, and ensures the cutting of the electrode on the pipe column and the cutting of the whole thickness; the rotating mechanism drives the feeding mechanism to do circumferential rotating motion, so that circumferential cutting is realized; the centering mechanism ensures the centering state of the plasma cutting device. The ground control system can realize the monitoring and control of the underground cutting state, and realize accurate cutting. The plasma cutting device has the advantages that cutting force is not generated between the electrode and the tubular column during plasma cutting, the problem of mechanical cutter abrasion is solved, meanwhile, the plasma cutting time is short, the efficiency is high, and the plasma cutting device has great tubular column cutting advantages.

The utility model has the advantages that the cutting efficiency is far higher than the conventional mechanical cutting, and the cutting success rate is high; secondly, compared with the sand blasting cutting, the cutting system has simple equipment; and thirdly, the ground control system can realize real-time monitoring and adjustment of the cutting state of the underground cutting system, and the cutting is more accurate.

Drawings

Fig. 1, 2, 3, 4 and 5 are schematic diagrams of five preferred embodiments of the downhole oil/casing plasma cutting device respectively.

Figure 6 is a schematic view of a preferred embodiment of the electrode feed mechanism (feed mechanism housing half section).

Figure 7 is a schematic view of a preferred embodiment of the rotary mechanism (rotary mechanism housing and lower end cap half-section).

Figure 8 is a schematic view of a preferred embodiment of the centralizer (upper centralizer top cover and upper centralizer housing half section).

The labels in the figure are: 1-a cable; 2-a downhole tubular string to be cut; 3-an electrode feeding mechanism; 4-guide shoe; 5-a rotating mechanism; 6-installing a righting mechanism; 7-lower righting mechanism.

31-upper fixed disc; 32-a stepper motor; 33-a driven shaft; 34-a motor fixing plate; 35-a drive gear; 36-a housing; 37-driven synchronizing wheel; 38-a belt; 39-electrodes; 310-lower fixed disc; 311-stud long bolt; 312-a bearing; 313-an electrode push block; 314-a driving synchronizing wheel; 315-driven gear; 316-drive shaft; 317-flange plate; 318-upper end cap.

51-a crossover joint; 52-a rotating electrical machine; 53-a rotary mechanism housing; 54-motor support plate; 55-a coupler; 56-conduit; 57-a bearing; 58-lower end cap.

61-middle screw; 62-upper compression nut; 63-upper hold down spring; 64-a moving block; 65-support bars; 66-a bearing; 67-connecting piece; 68-righting rollers; 69-lower hold down spring; 610-pressing down the nut; 611-fixing the block; 612-a base; 613-righting mechanism top cover; 614-centralizing mechanism housing.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

In the description of the present specification, the above-mentioned upper and lower positional relationships are the same as the positional relationships illustrated in the drawings, and this is also the positional relationship between the members when the tool of the present invention is applied to a vertical well. For horizontal wells, upper refers to the heel of the horizontal section of the oil and water well, and lower refers to the toe of the horizontal section of the oil and water well.

The detailed implementation of each mechanism is illustrated by taking the fifth preferred embodiment in which the process column is the most complex and includes the most complex mechanisms.

As shown in fig. 5, 6, 7 and 8, the downhole oil/casing plasma cutting device comprises a cable 1, an electrode feeding mechanism 3, a guide shoe 4, a rotating mechanism 5, an upper righting mechanism 6, a lower righting mechanism 7 and the like.

The cable 1 mainly provides power for the electrode feeding mechanism 3 and the rotating mechanism 5. When the process is applied to a horizontal well, the cable 1 needs to be carried by a coiled tubing or a special tool such as a crawler and the like to bring the cable 1 into a horizontal section so as to provide power for a cutting tool.

The electrode feeding mechanism 3 is a core structure of a cutting pipe column, and cutting of the underground oil/casing string is realized through transverse feeding, retraction and rotary motion of the electrode. The electrode feeding mechanism 3 mainly comprises an upper fixed disk 31, a stepping motor 32, a driven shaft 33, a motor fixing plate 34, a driving gear 35, a shell 36, a driven synchronizing wheel 37, a belt 38, an electrode 39, a lower fixed disk 310, a long stud bolt 311, a bearing 312, an electrode push block 313, a driving synchronizing wheel 314, a driven gear 315, a driving shaft 316, a flange 317, an upper end cover 318 and the like. The upper fixed disk 31 is fixed on the shell 36 through screws, the stepping motor 32 is fixed on the motor fixing plate 34, the motor fixing plate 34 is fixed on the upper fixed disk 31 through bolts, the driving gear 35 is mounted on the output shaft of the stepping motor 32, the driven gear 315 and the driving synchronizing wheel 314 are mounted on the driving shaft 316, the driving shaft 316 and the driven shaft 33 are installed between the upper fixed disk 31 and the lower fixed disk 310, the driven synchronizing wheel 37 is mounted on the driven shaft 33, the belt 38 is mounted on the driving synchronizing wheel 314 and the driven synchronizing wheel 37, the electrode pushing block 313 is fixed on the belt 38 through bolts, the electrode 39 and the bearing 312 are fixed on the electrode pushing block 313 through bolts, the long stud 311 is installed between the upper fixed disk 31 and the lower fixed disk 310 by nuts, and the lower fixed disk 310 is fixed to the housing 36 by screws. When the stepping motor 32 works, the driving gear 35 is driven to transmit torque to the driven gear 315, the driven gear 315 drives the driving shaft 316 to rotate, the driving shaft 316 drives the driving synchronous wheel 314 to rotate, the driving synchronous wheel 314 drives the driven synchronous wheel 37 to move through the synchronous belt 38, so that the rotary motion of the stepping motor 32 is converted into the linear motion of the synchronous belt 38, the electrode push block 313 is driven to move through the motion of the synchronous belt 38, and the electrode 39 is driven to realize the feeding and withdrawing functions. The flange 317 is fixedly connected with the upper end cover 318.

Remarking: fig. 6 is only one preferred embodiment of the electrode feeding mechanism, and other different mechanisms for achieving electrode feeding may be equally applied to the downhole cutting device.

The rotating mechanism 5 is a component of the cutting device that provides the rotating power.

The rotation mechanism 5 mainly includes components such as an adapter 51, a rotation motor 52, a rotation mechanism housing 53, a motor support plate 54, a coupling 55, a conduit 56, a bearing 57, and a lower end cap 58. The upper part of the rotating mechanism shell 53 is in threaded connection with the adapter 51, and the lower part is in threaded connection with the lower end cover 48. The remaining components are disposed inside the rotary mechanism housing 53. The motor support plate 54 is fixed to the rotation mechanism housing 53. The rotating motor 52 is fixed to a motor support plate 54. The rotating electrical machine output shaft is connected to a hollow conduit 56 by a coupling 55. The bearing 57 is fixed on the lower end cover 58 and bears the weight of the whole rotating mechanism. The hollow conduit 56 is connected with a flange 318 in the electrode feeding mechanism 3, so as to realize the connection between the rotating mechanism 5 and the electrode feeding mechanism 3. The rotating motor 52 drives the wire conduit 56 to rotate, and drives the electrode feeding mechanism 3 to rotate circumferentially to realize circumferential cutting.

Remarking: fig. 7 is only a preferred embodiment of the rotating mechanism, and other transmission mechanisms capable of realizing the rotating function can be applied to the downhole cutting device.

The upper righting mechanism 6 and the lower righting mechanism 7 are righting mechanisms of the cutting device, and the centering degree of the cutting device is guaranteed, so that the symmetry of underground oil/casing cutting is realized. The upper righting mechanism 6 and the lower righting mechanism 7 have the same structure, and the structure and the implementation of the righting mechanism are described by taking the upper righting mechanism 6 as an example.

The upper centering mechanism 6 mainly comprises a middle screw 61, an upper compression nut 62, an upper compression spring 63, a movable block 64, a support rod 65, a bearing 66, a connecting sheet 67, a centering roller 68, a lower compression spring 69, a lower compression nut 610, a fixed block 611, a base 612, a centering mechanism top cover 613, a centering mechanism shell 614 and the like. The upper compression nut 62 is sleeved outside the middle screw rod 61, the upper compression nut 62 is fixed above the upper compression spring 63, the lower compression nut 610 is fixed above the fixed block 611, and the adjusting of the positions of the upper compression nut 62 and the lower compression nut 610 can realize the adjustment of the pre-tightening force of the upper compression spring 63 and the lower compression spring 69, so that the centering force can be adjusted. The upper port thread buckle type of the shell of the righting mechanism is connected with the top cover of the righting mechanism, the lower port thread buckle type of the shell of the righting mechanism is connected with the base, the upper compression nut, the lower compression nut, the upper compression spring and the lower compression spring are all sleeved outside the middle screw rod, the upper compression nut is fixed above the upper compression spring, the lower compression nut is positioned below the lower compression spring, the lower compression nut is fixed above the fixed block, the fixed block is fixed on the base, a bearing is installed in an inner hole of the movable block, the bearing is sleeved on the middle screw rod, the movable block is positioned between the upper compression spring and the lower compression spring, the support rod comprises an upper support rod and a lower support rod, the upper end of the connection piece is hinged with the lower end of the upper support rod, the lower end of the connection piece is hinged with the upper end of the lower support rod, the lower end of the lower support rod is hinged with the fixed block, the righting roller, the movable block 64, the support rod 65, the connecting piece 67, the centering roller 68 and the fixed block 611 are connected with each other to form a link mechanism. The number of the centering rollers 68 may be 1, 2 or more, and in the preferred embodiment, the number of the centering rollers 68 is 3. The upper righting mechanism 6 is connected with the rotating mechanism 5 through a conversion joint 51; and a conversion joint 51 is additionally arranged between the electrode feeding mechanism 3 and the lower righting mechanism 7 to realize connection.

Remarking: the centralizing mechanism shown in fig. 8 is only one preferred embodiment of the centralizing mechanism, and other mechanisms which can realize a centralizing function, such as a spring plate centralizer, a hydraulic centralizer and the like, can be applied to the downhole cutting device.

The utility model discloses a plasma cutting technology implementation scheme of oil/sleeve pipe in pit is (with the technology tubular column most complicated, including the most complicated preferred embodiment five of mechanism as the example and explain):

1. a plasma cutting device is put in, and a guide shoe, a lower righting mechanism, an electrode feeding mechanism, a rotating mechanism, an upper righting mechanism and a cable are arranged from bottom to top to a wellhead (if the horizontal well is adopted, the cable needs to be preset in a coiled tubing or a pipe column is carried by a crawler to be put in series);

2. under the action of the upper righting mechanism and the lower righting mechanism, the plasma cutting device keeps a centered state;

3. electrifying the ground, driving an electrode to feed to the inner wall of the cutting pipe column by a stepping motor in the electrode feeding mechanism, and generating plasma discharge when a certain gap is reached to generate high temperature to start cutting; the electrode is fixed on the electrode feeding mechanism and is connected with a ground electric control cabinet through a cable.

4. The rotary motor in the rotary mechanism rotates to drive the electrode in the electrode feeding mechanism to rotate, so that annular cutting of the underground oil/casing pipe is realized, meanwhile, the electrode feeding mechanism continuously compensates consumption of the electrode, and annular uniform cutting of the underground oil/casing pipe is realized.

The connections referred to in the above embodiments are conventional in the art, such as threaded connections for various components, and may be replaced by welds or other equivalent connections. But internal threaded connections are common in the art.

In the description of the present invention, it should be understood that the orientation indication or positional relationship is based on the orientation or positional relationship shown in the drawings, and is only for convenience of description of the present invention, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. The plasma cutting device for the underground oil casing is characterized by comprising an electrode, an electrode feeding mechanism and a guide shoe, wherein the electrode is fixed on the electrode feeding mechanism and is arranged outwards in the radial direction, the guide shoe is connected to the lower axial end of the electrode feeding mechanism, and the electrode feeding mechanism are both connected with a cable.

2. The plasma cutting device for downhole oil casings of claim 1, wherein the upper end of the electrode feeding mechanism is connected with the rotating mechanism.

3. A downhole oil casing plasma cutting device according to claim 2, wherein a centralizing mechanism is connected to the upper end of the rotating mechanism.

4. A downhole oil casing plasma cutting device according to claim 3, wherein a lower centering mechanism is further connected between the guide shoe and the electrode feeding mechanism.

5. The plasma cutting apparatus for downhole oil casings of claim 1, 2 or 3, wherein the electrode feeding mechanism comprises an upper fixed disk, a stepping motor, a driven shaft, a motor fixing plate, a driving gear, a housing, a driven synchronizing wheel, a belt, a lower fixed disk, an electrode pushing block, a driving synchronizing wheel, a driven gear, a driving shaft, a flange plate, and an upper end cap, the upper fixed disk is fixed on the inner wall of the housing, the stepping motor is fixed on the motor fixing plate, the motor fixing plate is fixed on the upper fixed disk, the driving gear is mounted on an output shaft of the stepping motor, the driven gear and the driving synchronizing wheel are mounted on the driving shaft, the driving gear is engaged with the driven gear, the driving shaft and the driven shaft are mounted between the upper fixed disk and the lower fixed disk, the driven synchronizing wheel is mounted on the driven shaft, the belt is installed on the driving synchronizing wheel and the driven synchronizing wheel, the electrode push block is fixed on the belt, the electrode is fixed on the electrode push block, the shell is provided with radial holes for the electrode to extend out, the lower fixing disc is fixed on the shell, the upper end cover is connected to the upper end of the shell, and the flange plate is fixed on the upper end cover.

6. The plasma cutting apparatus for downhole oil casings of claim 5, wherein the electrode feeding mechanism further comprises a long stud bolt, the upper end of the long stud bolt is mounted on the upper fixing disc through a nut, and the lower end of the long stud bolt is connected with the lower fixing disc.

7. The plasma cutting device for the downhole oil casing according to claim 2 or 3, wherein the rotating mechanism comprises a conversion joint, a rotating motor, a rotating mechanism shell, a motor supporting plate, a coupler, a conduit, a bearing and a lower end cover; the upper part of the shell of the rotating mechanism is connected with the adapter, and the lower part of the shell of the rotating mechanism is connected with the lower end cover; the rotating motor, the rotating mechanism shell, the motor supporting plate, the coupler and the conduit are arranged inside the rotating mechanism shell; the motor supporting plate is fixed with the shell of the rotating mechanism, the rotating motor is fixed on the motor supporting plate, an output shaft of the rotating motor is connected with the hollow conduit through a coupler, the bearing is fixed in an inner hole of the lower end cover and sleeved on the outer wall of the hollow conduit, and the whole rotating mechanism is connected with a flange plate of the feeding mechanism through the tail end of the hollow conduit.

8. The plasma cutting device for the downhole oil casing according to claim 4, wherein the upper centering mechanism or the lower centering mechanism comprises a middle screw rod, an upper compression nut, an upper compression spring, a movable block, a supporting rod, a connecting sheet, a centering roller, a lower compression spring, a lower compression nut, a fixed block, a base, an upper top cover and a centering mechanism shell; the upper port of the shell of the righting mechanism is connected with a top cover of the righting mechanism, the lower port of the shell of the righting mechanism is connected with a base, an upper compression nut, a lower compression nut, an upper compression spring and a lower compression spring are all sleeved outside a middle screw rod, the upper compression nut is fixed above the upper compression spring, the lower compression nut is positioned below the lower compression spring, the lower compression nut is fixed above a fixed block, the fixed block is fixed on the base, a bearing is arranged in an inner hole of a movable block, the bearing is sleeved on the middle screw rod, the movable block is positioned between the upper compression spring and the lower compression spring, the support rod comprises an upper support rod and a lower support rod, the upper end of the connection piece is hinged with the lower end of the upper support rod, the upper end of the upper support rod is hinged with the movable block, the lower end of the lower support rod is hinged with the fixed block, the righting roller is arranged on the connection piece, the movable block, the supporting rod, the connecting sheet, the righting roller and the fixed block are connected with each other to form a connecting rod mechanism.

9. A downhole oil casing plasma cutting device according to claim 8, wherein at least one set of the centralizing rollers is provided.

10. The plasma cutting device for downhole oil casings according to claim 4, wherein the upper centering mechanism is connected with the rotating mechanism through a conversion joint; and a conversion joint is additionally arranged between the electrode feeding mechanism and the lower righting mechanism to realize connection.