Positioning device for underground hydraulic cutting tubular column

Abstract

The utility model provides a positioning device for an underground hydraulic cutting pipe column, and belongs to the technical field of oil and gas well underground internal cutting tool fixing equipment. The positioning device for the underground hydraulic cutting pipe column comprises a hydraulic anchor, the hydraulic anchor comprises a central pipe and an anchor tile installed on the central pipe, the anchor tile is installed in a piston hole formed in the pipe wall of the central pipe, an adapter pipe is rotationally assembled in the central pipe, and pipe column connectors are arranged at the two ends of the adapter pipe respectively. A closed annular cavity is defined between the adapter pipe and the central pipe, and a communicating opening communicated with the annular cavity is formed in the wall of the adapter pipe. When in use, the device is mounted on an assembly (such as a drill rod or an oil pipe) which drives the cutting knife to rotate, the adapter tube rotates along with the cutting knife to realize cutting, and meanwhile, hydraulic pressure enters the piston hole from the communication port to push the anchor tile to extend out, so that the cutting knife is anchored. Compared with the prior art, the cutter can be better prevented from jumping, and the cutting efficiency is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of downhole internal cutting tool fixing equipment in oil and gas wells, and particularly relates to a positioning device for downhole hydraulic cutting of a pipe column. Background Art

[0002] During the oil production process in the oil field, there will be problems such as the oil pipe being broken and stuck in the casing and being unable to be salvaged by conventional salvage tools, and the bending and deformation of the oil pipe or casing affecting the oil production efficiency. At this time, it is necessary to use a downhole internal cutting tool to cut the stuck or bent and deformed oil pipe or casing, and then use conventional salvage tools to salvage it. The downhole internal cutting tool needs to be used in conjunction with a mud pump and a downhole tool string (oil pipes, drill pipes, continuous tubing and other tools) during operation. Conventional hydraulic cutting tools include a body and a cutter. The hydraulic cutting tool is installed at the lower end of the drill pipe and lowered to the part to be cut. The mud pump on the ground is used to inject high-pressure liquid into the hydraulic cutting tool body to make the cutter open outward and contact the inner wall of the casing or oil pipe. The cutter rotates with the drill pipe to cut the oil pipe or casing, thereby achieving the purpose of cutting the casing or oil pipe. During the operation of hydraulic cutting tools, especially tool strings in inclined wells and downhole hydraulic cutting tools, they cannot be centered under the action of gravity. When cutting the pipe body, the cutter will jump in different directions under the action of the transmitted cutting reaction force, affecting the cutting efficiency and accelerating the wear of the cutter.

[0003] The Chinese utility model patent with the authorization announcement number CN205089265U and the authorization announcement date March 16, 2016 discloses a disposable hydraulic cutter for cutting multi-layer casing. The disposable hydraulic cutter for cutting multi-layer casing includes an upper joint, a center hole is provided in the upper joint, the lower end of the upper joint is connected to a body, a guide hole is provided in the body, a T-type piston rod is provided in the body, a reduced portion of the T-type piston rod slides through the guide hole, and a stop edge for stopping the expanded portion of the T-type piston rod is provided above the guide hole on the body. The expanded portion of the T-type piston rod and the lower end of the upper joint form an inverted cone cavity, an axially penetrating liquid flow channel is provided in the T-type piston rod, an upper nozzle is provided in the fluid channel at the upper end of the T-type piston rod, and a spring is sleeved between the expanded portion and the guide hole at the reduced portion of the T-type piston rod, and the spring is used to support the T-type piston rod and realize the automatic retraction of the blade after cutting. A lower nozzle is provided at the lower end of the reduced portion of the T-shaped piston rod, and a through slot is provided on the circumference of the body below the guide hole. A blade is connected to the through slot through a pin shaft, and the upper end of the blade extends upward to the guide hole for the T-shaped piston rod to push forward. When in use, the hydraulic cutter is connected to the drill bit, and high-pressure liquid is pumped into the hydraulic cutter through a mud pump. The high-pressure liquid generates a pressure drop through the upper and lower nozzles in the piston to push the piston to move and open the blade. The blade rotates with the cutting drill bit to cut the casing.

[0004] The hydraulic cutter used for cutting multi-layer casing at one time is a typical downhole internal cutting tool. It is connected to the drill bit during use, and the drill bit drives the hydraulic cutter to rotate. Due to the weight of the drill bit and the hydraulic cutter and the cutting reaction force, the blade of the hydraulic cutter will jump in different directions during operation. Especially in inclined wells, the weight of the drill bit and the hydraulic cutter makes it impossible to center the blade, resulting in the inability to completely cut the casing. Utility Model Content

[0005] The utility model aims to provide a positioning device for downhole hydraulic cutting pipe string, so as to solve the problem in the prior art that the cutting knife jumps in different directions during the process of cutting oil pipe or casing with downhole hydraulic cutting tool, thus affecting the cutting efficiency.

[0006] In order to achieve the above-mentioned purpose, the positioning device for downhole hydraulic cutting pipe string provided by the utility model adopts the following technical solutions:

[0007] A positioning device for downhole hydraulic cutting pipe string, including a hydraulic anchor, the hydraulic anchor including a center pipe and an anchor shoe installed on the center pipe, the anchor shoe is installed in a piston hole provided on the pipe wall of the center pipe, a transfer tube is rotatably mounted in the center pipe, pipe string joints are respectively provided at both ends of the transfer tube, and a closed annular cavity is formed between the transfer tube and the center pipe, and a connecting port connected to the annular cavity is provided on the pipe wall of the transfer tube.

[0008] Beneficial effect: The positioning device for downhole hydraulic cutting pipe string of the utility model is a pioneering invention. The positioning device for downhole hydraulic cutting pipe string of the utility model includes a hydraulic anchor. By installing a rotatable transfer tube in the center tube of the hydraulic anchor, and the two ends of the center tube are respectively provided with pipe column joints that can be connected with drill pipes or oil pipes, etc., so that the positioning device for downhole hydraulic cutting pipe string of the utility model can be used in conjunction with downhole hydraulic cutting tools. A connecting port is opened on the wall of the transfer tube, and a closed annular cavity is formed between the transfer tube and the center tube. The hydraulic pressure is pumped into the drill pipe or oil pipe from the mud pump to open the blade of the downhole hydraulic cutting tool connected to the lower end of the drill pipe or oil pipe. At the same time, the hydraulic pressure enters the closed annular cavity through the transfer tube and then enters the piston hole to extend the anchor claw of the hydraulic anchor against the inner wall of the oil pipe or casing, thereby anchoring the downhole hydraulic cutting tool, and preventing the cutting knife of the downhole hydraulic cutting tool from jumping in different directions when rotating, which affects the cutting efficiency.

[0009] Furthermore, the transfer tube is rotatably assembled on the central tube via a thrust bearing.

[0010] Furthermore, the thrust bearing between the central tube and the transfer tube comprises an upper thrust bearing and a lower thrust bearing, which are respectively used to bear the axial force when the transfer tube moves upward / downward relative to the central tube.

[0011] Furthermore, the upper thrust bearing is installed on the upper part of the central tube, and the lower thrust bearing is installed on the lower part of the central tube.

[0012] Furthermore, bearing pressure caps for stopping the upper and lower thrust bearings are provided at both ends of the central tube.

[0013] Furthermore, the communication port is formed by a slit provided on the transfer tube.

[0014] Furthermore, the gap extends along the axial direction of the transfer tube.

[0015] Furthermore, the slit is arranged on the circumference of the central tube corresponding to the piston hole.

[0016] Furthermore, the central tube is provided with a limiting strip on the piston hole, and an elastic member for automatically resetting the anchor shoe is provided between the limiting strip and the hydraulic anchor shoe.

[0017] Furthermore, a swirl groove is provided on the surface of the central tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A quarter cross-sectional view of the overall structure of an embodiment of the positioning device for downhole hydraulic cutting pipe string of the utility model along the axial direction;

[0019] Figure 2 for Figure 1 Schematic diagram of the central tube junction in;

[0020] Figure 3 for Figure 1 Schematic diagram of the transfer tube structure in FIG.

[0021] Figure 4 for Figure 1 Schematic diagram of thrust bearing structure in FIG.

[0022] Figure 5 for Figure 4 Schematic diagram of the cage structure in FIG.

[0023] Figure 6 It is a schematic diagram of the pressure cap structure.

[0024] In the figure: 1. positioning groove; 2. O-ring; 3. anti-rotation pin; 4. spring; 5. anchor claw; 6. center tube; 7. adapter tube; 8. upper thrust bearing; 9. bearing cap; 10. countersunk screw; 11. rubber spacer; 12. limit plate; 13. swirl groove; 14. piston hole; 15. first positioning hole; 16. convex spline; 17. connecting port; 18. dynamic seal groove; 19. concave spline groove; 20. retaining frame; 21. retaining ring; 22. second positioning hole; 23. base; 24 lower thrust bearing. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the utility model and are not used to limit the utility model, that is, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. The components of the embodiments of the utility model described and shown in the drawings here can be arranged and designed in various different configurations.

[0026] The positioning device for downhole hydraulic cutting pipe string of the utility model is further described in detail below in conjunction with the embodiments.

[0027] During the oil production process, the oil pipe may get stuck in the casing and cannot be salvaged by conventional salvage methods. At this time, it is necessary to use a downhole hydraulic cutting tool to cut the oil pipe or casing and then salvage it. When the cutter of the downhole hydraulic cutting tool rotates, due to the gravity of the downhole hydraulic cutting tool itself and the upper end of the pipe string and the cutting reaction force, the cutter will jump in different directions on the cutting surface, affecting the cutting efficiency.

[0028] In order to solve the above problems, the concept of the utility model is:

[0029] In order to keep the blade stable and not bounce during cutting, it is necessary to use an anchoring tool to anchor the downhole hydraulic cutting tool. The commonly used cutting tool in the well repair process is a hydraulic cutter. The hydraulic cutter uses hydraulic pressure to drive the blade to open when cutting the downhole tubular. The commonly used method for anchoring the tubular downhole is to connect the anchoring tool to the tubular and use the anchor tile of the anchoring tool to clamp the pipe wall for anchoring. The hydraulic cutter is anchored by a hydraulic anchor, but the hydraulic anchor cannot rotate during the anchoring process, and the hydraulic cutter needs to rotate quickly to complete the cutting of the tubing or casing. Therefore, the hydraulic anchor cannot directly anchor the hydraulic cutter. Therefore, a rotatable transfer tube is set in the center tube of the hydraulic anchor, and tubular joints connected to the tubular are set at both ends of the transfer tube. The anchoring tool is installed on the drill pipe or tubing through the tubular joint. The transfer tube can rotate together with the drill pipe or tubing that drives the hydraulic cutter to rotate.

[0030] In order to extend the anchor shoe of the hydraulic anchor and realize the anchoring work, hydraulic energy needs to enter the piston hole of the hydraulic anchor to push the anchor shoe installed in the piston hole to extend, and a connecting port is opened on the wall of the transfer tube. The hydraulic pressure enters the closed annular cavity formed between the center pipe and the transfer tube through the connecting port in the transfer tube, and then enters the piston hole on the center pipe to push the anchor shoe against the inner wall of the oil pipe or casing, thereby realizing the anchoring of the downhole hydraulic cutting tool.

[0031] To summarize, when in use, the positioning device for the downhole hydraulic cutting pipe string is installed on the component that drives the blade to rotate of the downhole hydraulic cutting tool, such as the drill pipe or the oil pipe, and the hydraulic pressure enters the hydraulic cutting tool body to open the blade. At the same time, the hydraulic pressure enters the annular cavity between the transfer pipe and the center pipe from the connecting port on the transfer pipe, and then enters the piston hole to push the anchor shoe in the piston hole to extend, thereby anchoring the hydraulic cutter and preventing the blade of the hydraulic cutter from jumping on the cutting surface when rotating. When cutting, the transfer pipe rotates together with the components that drive the blade to rotate, such as the oil pipe or casing. After the cutting is completed, the hydraulic pressure is removed, the blade stops working, and the anchor shoe is released from the anchoring in the absence of hydraulic pressure, and the downhole hydraulic cutting tool and the positioning and rotating device for the downhole hydraulic cutting pipe string are taken out together.

[0032] exist Figure 1 and Figure 2 In the illustrated embodiment, the piston holes 14 on the hydraulic anchor center pipe 6 are divided into four rows, and three in each row are arranged in a straight line and evenly distributed around the center pipe 6. Anchor shoes are arranged in the piston holes 14. The more piston holes 14 there are, the more anchor shoes there are. The more anchor shoes there are, the better the anchoring effect is. In other embodiments, the number and arrangement of the piston holes 14 can be flexibly set as needed, such as 3 or 5. The center pipe 6 is provided with a swirl groove 13, which is located between two rows of piston holes 14, so that the drilling fluid, mud liquid and other liquids can flow out along the swirl groove 13 during cutting, and then return along the annulus between the oil pipe or drill pipe and the casing for recycling.

[0033] Specifically, the anchor shoe is composed of a base 23 and two anchor claws 5. The two anchor claws 5 are symmetrically distributed on the base. The base 23 is used to install the anchor claws 5 and drive the anchor claws 5 to slide in the piston hole 14. A first sealing groove is provided on the periphery of the base 23. A first sealing member is installed in the first sealing groove. Figure 1 In the embodiment shown, the first sealing member is a rubber packing sleeve 11, which ensures that when the hydraulic pressure pushes the anchor shoe to move, the hydraulic pressure will not leak from the gap between the anchor shoe and the piston hole 14, so that the hydraulic pressure can push the anchor shoe out and stably clamp it on the inner wall of the casing or oil pipe without loosening. In other embodiments, the first sealing member can also be a sealing ring or sealing filler or other sealing members that can achieve sliding sealing between the base 23 and the inner wall of the piston hole 14.

[0034] exist Figure 1 In the embodiment shown, the center tube 6 is provided with a limit strip 12 above the piston hole 14. Both ends of the limit strip 12 are connected to the center tube 6 by countersunk screws 10. An elastic member is installed between the limit strip 12 and the base. Figure 1In the illustrated embodiment, the elastic member is a spring 4, one end of which is connected to the limiting strip 12, and the other end is connected to the base. During operation, hydraulic pressure enters the piston hole 14 to push the base 23 to move, and the base 23 drives the anchor claw 5 to extend outward, so that the anchor claw 5 is stuck on the inner wall of the oil pipe or casing, and the spring 4 is compressed at the same time. When it is necessary to release the anchor, the hydraulic pressure is removed, the spring 4 rebounds, the anchor shoe is reset, and the anchor is released. In other embodiments, the elastic member can also be a spring sheet, etc. The limiting strip 12 is used to ensure the compression state of the spring 4 when the spring 4 is compressed, and to fix one end of the spring 4 when the spring 4 rebounds. Each row of anchor shoes and the piston hole 14 are arranged in a straight line, which is convenient for the limiting strip 12 to fix multiple springs 4 in the same row at the same time.

[0035] A connecting port 17 is provided on the transfer tube 7, and a sealed chamber is formed between the connecting port 17 and the piston hole 14, which is used for hydraulic pressure to enter the piston hole 14 to open the anchor shoe. Figure 3 In the illustrated embodiment, the communication port 17 is formed by a slit on the transfer tube 7. In other embodiments, the communication port 17 may also be formed by other shapes, such as a round hole or a square hole opened in the circumference of the transfer tube 7, so as to ensure that the hydraulic pressure can enter the closed annular cavity formed between the central pipe 6 and the transfer tube 7 from the transfer tube 7. The slit extends axially along the transfer tube 7 and is arranged at a position corresponding to the piston hole 14 in the circumference, so that the hydraulic pressure can face the anchor shoe and push the anchor shoe to extend, so that it can be more stably stuck on the inner wall of the oil pipe or casing.

[0036] exist Figure 1 In the illustrated embodiment, both ends of the transfer tube 7 are provided with pipe column joints, specifically, the pipe column joints are provided with threads, and when in use, the transfer tube 7 is threadedly connected to a rotating assembly that drives the cutter to rotate, such as an oil pipe or a drill pipe, through the threads on the pipe column joints, and the threads at both ends have the same rotation direction, and when the oil pipe or the drill pipe drives the hydraulic cutter to rotate, the rotation direction of the hydraulic cutter is the same as the tightening direction of the transfer tube 7, so as to ensure that the transfer tube 7 will not fall off when the hydraulic cutter rotates. In other embodiments, the pipe column joint can also be connected to the drill pipe or the oil pipe through other connection methods, such as pin connection, clamp connection, etc.

[0037] The transfer tube 7 is rotatably assembled to the center tube 6 through a thrust bearing. Specifically, there are two thrust bearings, namely an upper thrust bearing 8 and a lower thrust bearing 24. The upper thrust bearing 8 is installed on the upper part of the transfer tube 7, and the lower thrust bearing 24 is installed on the lower part of the transfer tube 7. When the hydraulic cutter blade cuts the oil pipe or casing, the blade will jump due to the cutting reaction force, etc., so that the drill pipe or oil pipe that drives the blade to rotate is repeatedly subjected to axial thrust, and the axial thrust is then transmitted to the transfer tube 7 connected to the drill pipe or oil pipe. In order to prevent the transfer tube 7 from moving under the action of the axial thrust, the upper thrust bearing 8 bears the axial thrust of the transfer tube 7 when it moves downward relative to the center tube 6, and the lower thrust bearing 24 bears the axial thrust of the transfer tube 7 when it moves upward relative to the center tube 6, and both the upper and lower thrust bearings transmit the axial force to the center tube 6.

[0038] In order to ensure that the upper and lower thrust bearings do not move axially, Figure 1 In the embodiment shown, bearing caps 9 are installed at both ends of the center tube 6. Specifically, first positioning grooves 1 are provided at both ends of the center tube 6. The upper and lower thrust bearings are respectively provided in the two first positioning grooves 1. The function of the bearing caps 9 is to stop the thrust bearing in the first positioning groove 1 to prevent the thrust bearing from exiting the first positioning groove 1 due to axial thrust during operation, thereby improving the stability of the positioning device for downhole hydraulic cutting pipe strings. In other embodiments, the thrust bearing can also be stopped in the first positioning groove 1 by other means such as a pressure plate to prevent it from escaping. At this time, it is necessary to respectively open positioning pin holes for the positioning pin to enter on the pressure plate and the end face of the center tube 6. The pressure plate passes through the transfer tube 7, and the positioning pin passes through the positioning pin holes on the pressure plate and the end face of the center tube 6 in turn to fix the pressure plate on the end face of the center tube 6.

[0039] exist Figure 1 In the embodiment shown, the bearing cap 9 passes through the two ends of the transfer tube 7 and is connected to the center tube 6 by threads, which facilitates the installation and disassembly of the thrust bearing. In other embodiments, the connection method between the bearing cap 9 and the center tube 6 can also be a pin hole connection. When connected by a pin hole, it is necessary to respectively open pin holes for the pin to enter on the bearing cap 9 and the center tube 6, and the pin is driven into the pin holes on the bearing cap 9 and the center tube 6 to realize the connection between the bearing cap 9 and the center tube 6.

[0040] exist Figure 2 and Figure 6 In the embodiment shown, in order to prevent the bearing cap 9 from loosening when the transfer tube 7 rotates, a first positioning hole 15 for the anti-rotation pin 3 to pass through is opened on the side of the bearing cap 9, and corresponding second positioning holes 22 are provided at the positions corresponding to the first positioning holes 15 at both ends of the center tube 6. The anti-rotation pin 3 passes through the first positioning hole 15 and the second positioning hole 22 in sequence to fix the bearing cap 9 and prevent it from rotating. Figure 2 and Figure 6In the illustrated embodiment, there are at least four first positioning holes 15, which are evenly distributed on the bearing cap 9. The more the first positioning holes 15 are, the smaller the load on a single anti-rotation pin 3 is, and when the force transmitted to the anti-rotation pin 3 by the bearing cap 9 is too large, the anti-rotation pin 3 is not easily damaged, thereby improving the stability of the positioning device for the entire downhole hydraulic cutting pipe string.

[0041] Specifically, Figure 1 and Figure 3 As shown, a dynamic seal groove 18 is installed on the transfer tube 7, and a dynamic seal is installed in the dynamic seal groove 18 to ensure the seal between the central tube 6 and the transfer tube 7 to prevent hydraulic leakage from the annular space between the transfer tube 7 and the central tube 6. Figure 1 and Figure 3 In the embodiment shown, the dynamic seal is an O-type dynamic seal ring 2, and the communication port 17 is located between two groups of O-type dynamic seal rings 2. Figure 1 and Figure 3 In the illustrated embodiment, there are at least four dynamic sealing grooves 18, and they are arranged in groups of two. The more dynamic sealing grooves 18 there are, the more O-rings 2 can be installed, and the better the sealing effect. In other embodiments, the number of dynamic sealing grooves 18 can also be six, and each group of three can be formed. The dynamic seal can also be other dynamic sealing components such as sealing fillers, as long as a seal can be formed between the transfer tube 7 and the center tube 6 to avoid hydraulic leakage.

[0042] exist Figure 1 , Figure 3 , Figure 4 and Figure 5 In the illustrated embodiment, a convex spline 16 is provided on the transfer tube 7 at a position corresponding to the first positioning groove 1, and a concave spline groove 19 is provided on the thrust bearing to match the convex spline 16. Specifically, the thrust bearing includes a retaining ring 21, a retaining frame 20, and a rolling element. The rolling element is installed in the retaining frame 20. The retaining ring 21 includes an upper retaining ring and a lower retaining ring. The retaining frame 20 is located between the upper and lower retaining rings. The concave spline groove 19 is located inside the retaining frame 20, and the convex spline 16 is arranged in the concave spline groove 19.

[0043] When the rotating assembly of the downhole hydraulic cutter rotates, the rotational force is transmitted to the adapter tube 7, and the convex spline 16 transmits the rotational force transmitted by the adapter tube 7 to the concave spline groove 19, thereby driving the retainer 20 to rotate, and finally realizing the rotation of the adapter tube 7. The number of convex splines 16 is at least 2, and the convex spline 16 is used to cooperate with the concave spline groove 19 to transmit the rotational force on the adapter tube 7 to the retainer 20. The more the number of convex splines 16, the smaller the force on a single convex spline 16, and the less likely it is to be damaged.

[0044] The convex splines 16 are evenly distributed around the transfer tube 7, so that the rotational force on the transfer tube 7 can be evenly transmitted to the retaining frame 20 through the convex splines 16. Figure 5 In the illustrated embodiment, the number of the convex splines 16 is 3, while in other embodiments, the number of the convex splines 16 may be 1, 2, 4 or other numbers, as long as the convex splines 16 can stably transmit the rotational force.

[0045] The use process of the positioning device for downhole hydraulic cutting pipe string of the utility model is as follows:

[0046] First, install the pipe column joints at both ends of the transfer tube 7 on the rotating assembly (such as oil pipe or drill pipe, etc.) that drives the cutting blade to rotate on the downhole hydraulic cutting tool, and then lower the downhole hydraulic cutting tool and the positioning device for downhole hydraulic cutting pipe column of the utility model to the part to be cut. Pump hydraulic pressure into the oil pipe or drill pipe, and the hydraulic pressure enters the sealed annular cavity between the transfer tube 7 and the center pipe 6 along the connecting port of the transfer tube, and then enters the piston hole 14 from the annular cavity between the transfer tube 7 and the center pipe 6, pushing the anchor shoe to extend from the piston hole 14, so as to realize the anchoring of the downhole hydraulic cutting tool. At this time, the elastic member installed between the anchor shoe base 23 and the limiting strip 12 is compressed. When the cutting is completed, the hydraulic pressure is removed, the downhole hydraulic cutting tool stops rotating, the anchor shoe loses the hydraulic thrust, the elastic member is reset to pull the anchor shoe to release the anchoring, and then the downhole hydraulic cutting tool and the positioning device for downhole hydraulic cutting pipe column of the utility model are taken out together.

Claims

1. A positioning device for downhole hydraulic cutting pipe string, characterized in that: The hydraulic anchor comprises a center pipe and an anchor shoe installed on the center pipe, the anchor shoe is installed in a piston hole provided on the pipe wall of the center pipe, a transition tube is rotatably mounted in the center pipe, pipe column joints are respectively provided at both ends of the transition tube, and a closed annular cavity is formed between the transition tube and the center pipe, and a connecting port connected to the annular cavity is provided on the pipe wall of the transition tube.

2. The positioning device for downhole hydraulic cutting pipe string according to claim 1, characterized in that: The transfer tube is rotatably assembled on the central tube via a thrust bearing.

3. The positioning device for downhole hydraulic cutting pipe string according to claim 2, characterized in that: The thrust bearing between the central tube and the transfer tube comprises an upper thrust bearing and a lower thrust bearing, which are respectively used to bear the axial force when the transfer tube moves upward / downward relative to the central tube.

4. The positioning device for downhole hydraulic cutting pipe string according to claim 3, characterized in that: The upper thrust bearing is installed on the upper part of the central tube, and the lower thrust bearing is installed on the lower part of the central tube.

5. The positioning device for downhole hydraulic cutting pipe string according to claim 4, characterized in that: Both ends of the central tube are provided with bearing pressure caps for stopping the upper and lower thrust bearings.

6. The positioning device for downhole hydraulic cutting pipe string according to claim 1, characterized in that: The communication port is formed by a slit arranged on the transfer tube.

7. The positioning device for downhole hydraulic cutting pipe string according to claim 6, characterized in that: The slit extends along the axial direction of the transfer tube.

8. The positioning device for downhole hydraulic cutting pipe string according to claim 7, characterized in that: The slits are arranged on the circumference of the central tube corresponding to the piston holes.

9. The positioning device for downhole hydraulic cutting pipe string according to any one of claims 1 to 8, characterized in that: The central tube is provided with a limiting strip on the piston hole, and an elastic member for automatically resetting the anchor shoe is provided between the limiting strip and the hydraulic anchor shoe.

10. The positioning device for downhole hydraulic cutting pipe string according to claim 1, characterized in that: The surface of the central tube is provided with a swirl groove.

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