Underground sleeve cutting nipple

Abstract

The utility model discloses an underground sleeve cutting nipple. The tool is provided with a sleeve cutting mechanism, a turbine driving mechanism and an anchoring mechanism, wherein the turbine driving mechanism mainly comprises a turbine and an upper transmission shaft; the anchoring mechanism is provided with an anchoring piston, a piston guide rod and an anchoring plate; two ends of the upper shell are respectively connected with the connector and the end cover, and an upper baffle ring is also arranged between the connector and the upper shell; liquid flow channels are formed in the upper baffle ring, the end cover, the upper transmission shaft and the lower transmission shaft, and a pressure relief hole is further formed in the lower transmission shaft; the upper transmission shaft is sequentially connected with a lower transmission shaft provided with a cutting control piston and a cutter outer shell, and a cutter meshing shaft fixed to the lower end of the cutting control piston is meshed with a cutter. And a cutter reset spring is arranged between the cutter meshing shaft and the cutter outer shell. And the cutting completion condition of the casing pipe can be conveniently and accurately judged according to the observed pressure reduction of the drilling fluid on the ground. Power needed by the tool is provided by hydraulic pressure of drilling fluid, and the cutting operation of the casing pipe is safer, more efficient and more economical.

Description

Technical Field

[0001] The utility model relates to a downhole casing cutting and recovery tool for the petroleum industry, in particular to a downhole casing cutting pup joint. Background Art

[0002] With the exploitation of underground energy, the exploitation time of oil and gas fields has increased year by year. The casing in some oil, gas and water wells has reached its service life or has been damaged. For some oil and water wells that have low reserves and recovery rates and are no longer necessary to use, they need to be abandoned and sealed and the casing in the wells needs to be cut. Cutting the casing in the well is an important operation project for abandoned wells. However, for those oil, gas and water wells with shallow casing damage and still useful, the casing replacement process is generally used to restore the casing function. Casing cutting is also a well repair operation project to remove the damaged casing from below the casing damage site.

[0003] At present, the cutting technologies for downhole casing mainly include chemical cutting, sand jet cutting, mechanical cutting knife cutting, etc. Among them, mechanical hydraulic cutting has the advantages of safety, high efficiency and economy and is widely used. However, most hydraulic cutting tools are easily damaged during the cutting process of casing, the service life of the tools is not long enough, and the structure and operation of the tools are complex. Most importantly, it is impossible to visually determine whether the casing in the well is completely cut during the construction process.

[0004] After searching, the commonly used casing cutting tools are as follows: Patent application number CN201710651559.4 discloses a variable diameter hydraulic cutter for well abandonment operation that uses multi-head spiral transmission to cut casing of different diameters, and its technical solution is: the upper joint and the shell are connected by threads; the nozzle is located in the mandrel and connected to the mandrel by threads; the piston is installed at the upper end of the mandrel by threaded connection, and then the piston, mandrel and spring are installed inside the shell; the mandrel is provided with a spiral groove, and the mandrel and the shell cooperate to form a multi-head spiral pair; the worm is located at the lower part of the mandrel and cooperates with the mandrel through a spline; the cutter is evenly distributed circumferentially and connected to the shell through a hinge pin, and the worm gear structure on the upper part of the cutter body is meshed with the worm to realize the transmission of the worm and the worm gear structure. The above invention converts the linear motion into rotational motion and transmits it to the worm through the mandrel, driving the worm gear structure to rotate, thereby controlling the opening angle of the cutter, which can realize continuous cutting of casing of different diameters, reduce the number of drilling times, and greatly improve the casing cutting efficiency during well abandonment operation.

[0005] However, during the cutting operation, the drill pipe needs to rotate to transmit torque to drive the cutter to cut the casing, and the cutting work stability still needs to be improved.

[0006] Patent application number CN201810280686.2 discloses a deepwater turbine hydraulic internal cutting tool, which belongs to the technical field of oil and gas drilling tools. It consists of a turbine torque device, a torque transmission device, a booster device and a casing cutting mechanism. A torque transmission device is installed at one end of the turbine torque device; a casing cutting mechanism is installed on the torque transmission device through a booster device. The above invention can effectively reduce the large moment of inertia generated by existing tools during deepwater operations; it solves the problem that the traditional method generates a large moment of inertia during deepwater casing cutting, resulting in a large amount of energy loss. The above invention improves the cutting stability and extends the working life of the tool through the cooperation of the shell and the slip. During the casing cutting process, as the valve port flow area formed by the push rod and the limit valve stem becomes smaller, the pressure drop at the valve port increases. It can be judged whether the cutting is completed based on the change in drilling fluid pressure observed on the ground, which is convenient and reliable and can avoid misjudgment.

[0007] However, the tool has a relatively complex structure, and the construction process has high requirements on the operating level of the construction personnel and the solid phase particle standards of the drilling fluid.

[0008] Downhole casing cutting tools still need to be improved. Summary of the invention

[0009] The utility model aims to provide a downhole casing cutting short section, simplify the structure of the existing tool, and improve the working stability during the cutting operation; at the same time, it can more quickly judge whether the downhole casing is completely cut off, thereby improving the working efficiency of the downhole casing cutting.

[0010] The technical solution of the utility model is: a downhole casing cutting short section, provided with a casing cutting mechanism, a cutting knife in the casing cutting mechanism is fixed in the tool outer shell through a pin shaft and meshed with the cutting knife meshing shaft, wherein: a turbine driving mechanism mainly composed of a turbine and an upper transmission shaft is installed in the upper inner cavity of the upper shell, the turbine is installed outside the upper transmission shaft, and an upper centering bearing and a lower centering bearing are respectively installed at the upper and lower ends of the turbine; an anchoring mechanism provided with an anchoring piston, a piston guide rod and an anchoring plate is installed in the clamping wall cavity of the upper shell, the piston guide rod is fixed in the upper shell through a base, the anchoring piston is installed outside the piston guide rod, a piston reset spring is installed between the anchoring piston and the base, and the anchoring piston and the base are respectively connected to the anchoring plate at the side opening of the clamping wall cavity of the upper shell through a connecting rod;

[0011] The two ends of the upper shell are respectively connected to the connecting head and the end cover, and an upper retaining ring is also installed between the connecting head and the upper shell; the upper retaining ring, the end cover, the upper transmission shaft and the lower transmission shaft are all provided with liquid flow channels, and the lower transmission shaft is also provided with a pressure relief hole; the upper transmission shaft is sequentially connected with the lower transmission shaft equipped with a cutting control piston and the tool outer shell, and the cutter engagement shaft fixed at the lower end of the cutting control piston is engaged with the cutter; a cutter reset spring is installed between the cutter engagement shaft and the tool outer shell.

[0012] Preferably, a thrust bearing 2 and an upper gasket are mounted outside the upper transmission shaft between the upper retaining ring and the upper straightening bearing, and the diameter of the center hole of the upper gasket is larger than the outer diameter of the upper transmission shaft to form a liquid flow channel.

[0013] Preferably, the upper retaining ring is a flange-shaped body and the outer diameter of the small diameter section is equal to or smaller than the inner diameter of the upper inner cavity of the upper shell body, and the center hole of the upper retaining ring is larger than the upper outer diameter of the upper transmission shaft; a liquid flow channel is provided in the large diameter section body of the outer periphery of the small diameter section of the upper retaining ring, and the liquid flow channel is composed of more than three liquid flow holes and corresponds to the clamping wall cavity of the upper shell body.

[0014] Preferably, the outer circle of the upper transmission shaft is a non-equal diameter outer circle and the lower part is provided with an external thread which is threadedly connected to the lower transmission shaft; the liquid flow channel in the upper transmission shaft is arranged in the small diameter section at the upper part of the upper transmission shaft, and the liquid flow channels are arranged in more than two; the inlet of the liquid flow channel in the upper transmission shaft is connected with the liquid flow channel in the upper retaining ring and the outlet of the liquid flow channel is connected with the liquid flow channel in the upper gasket ring; the thrust bearing 2 is also arranged outside the small diameter section at the upper part of the upper transmission shaft.

[0015] Preferably, a limit platform is provided on the top of the piston guide rod, the outer diameter of the limit platform is larger than the diameter of the center hole of the anchor piston, and the anchor piston is sleeved on the outside of the piston guide rod below the limit platform.

[0016] Preferably, the two ends of the lower transmission shaft are respectively provided with internal threads and external threads and can be threadedly connected to the upper transmission shaft and the tool outer shell respectively; the upper and lower ends of the cutter reset spring are respectively installed in the spring mounting seats provided at the lower end of the cutter engagement shaft and the bottom of the tool outer shell; the lower part of the cutter engagement shaft is provided with a rack and can mesh with the gear at the cutter engagement end.

[0017] Preferably, the lower transmission shaft has a non-uniform outer circle and the outer diameter of the upper outer circle is larger than the outer diameter of the lower outer circle, forming a thrust bearing retaining step; a thrust bearing and a lower gasket are installed between the end cover and the lower portion of the thrust bearing retaining step.

[0018] Preferably, the diameter of the center hole of the lower gasket ring is larger than the maximum outer diameter formed by the liquid flow channel in the end cover; the inner cavity of the connector is trumpet-shaped and the upper inner cavity is provided with an internal thread to connect with the drill rod.

[0019] Preferably, there are at least two liquid flow channels in the lower transmission shaft, and the inlet of the liquid flow channel is arranged in the main body above the thrust bearing clamping step, and the outlet of the liquid flow channel is arranged in the main body below the thrust bearing; the outlet and the pressure relief hole of the liquid flow channel in the lower transmission shaft both correspond to the center hole of the lower gasket.

[0020] Preferably, the number of pressure relief holes in the lower transmission shaft is more than two and they are downward inclined holes; the manufacturing material of the cutter head is cemented carbide; the initial installation position of the cutting control piston in the lower transmission shaft is determined according to the distance between the outer circle of the tool outer shell and the outer circle of the cut casing.

[0021] The beneficial effects of the utility model are as follows: the power of the turbine drive mechanism, the anchoring mechanism and the casing cutting mechanism, and the extension power of the cutter in the utility model are all provided by the hydraulic pressure of the drilling fluid, and there is no need to rotate the drill pipe to transmit torque. The power loss in the transmission process is relatively small, making the casing cutting safer, more efficient and more economical.

[0022] When the tool is lowered into the casing to the set cutting depth, the drilling fluid from the ground enters the wall cavity between the upper transmission shaft and the upper shell through the connector, and the anchor mechanism is first supported on the casing wall to ensure that the tool works stably during the cutting process. During the anchoring support process, when the hydraulic pressure of the drilling fluid increases, the hydraulic pressure presses the anchor piston downward, and the connecting rod connected to the anchor piston and the base pushes the anchor plate outward and anchors it on the inner wall of the casing, ensuring the stability of the tool.

[0023] As the pressure of the drilling fluid continues to increase, the drilling fluid enters the upper cavity of the upper shell through the liquid flow channel in the upper transmission shaft and the upper retaining ring, drives the turbine to rotate and drives the lower transmission shaft and the tool outer shell to rotate together through the upper transmission shaft; at the same time, the continuously rising drilling fluid pushes the cutting control piston installed in the lower transmission shaft downward, and the cutter engagement shaft drives the cutter to rotate and gradually rotate outward to extend and cut the casing.

[0024] During the casing cutting process, the drilling fluid from the ground can flow along the upper retaining ring, the upper transmission shaft, the lower transmission shaft and the liquid flow channel provided in the end cover to the annulus between the tool and the casing, thereby reducing the temperature of the cutting knife and cooling it, thereby extending the service life of the cutting knife.

[0025] A gear is arranged at the meshing end of the cutting knife, and a rack is arranged at the lower part of the cutting knife meshing shaft. The cutting knife is driven by the downward cutting knife meshing shaft to rotate and extend outward. Compared with the horizontal extension and rotational extension of the existing cutting knife, the rotational extension of the cutting knife driven by the meshing of the rack and the gear is safer, more reliable and more accurate.

[0026] When the cutter completes the cutting, the cutting control piston just moves down to the lower pressure relief hole in the lower transmission shaft, and the drilling fluid in the lower transmission shaft flows out from the pressure relief hole, reducing the pressure of the drilling fluid on the cutting control piston. At the same time, under the action of the cutter return spring, the cutting control piston no longer moves down. The casing cutting completion can be easily and accurately judged based on the observed reduction in drilling fluid pressure on the ground.

[0027] The utility model has a simple structure and fully uses hydraulic pressure to work. The ground staff can conveniently operate and control the cutting process of the downhole casing through the pressure pump. The operation is simple and can avoid the occurrence of misjudgment of casing cutting. The tool has high cutting efficiency for downhole casing and has a good use effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 It is a schematic diagram of the overall structure of the utility model in the initial state.

[0030] Figure 2 for Figure 1 Schematic diagram of the initial state of the anchoring mechanism.

[0031] Figure 3 for Figure 1 Schematic diagram of the working status of the anchoring mechanism.

[0032] Figure 4 for Figure 1 Schematic diagram of the appearance structure of the middle and lower drive shaft.

[0033] Figure 5 for Figure 1 Cross-sectional view of the middle and lower drive shaft.

[0034] Figure 6 for Figure 1 Schematic diagram of the structure of the middle cutter shell.

[0035] Figure 7 yes Figure 1 Top view and front view of the schematic diagram of the middle and upper retaining ring structure.

[0036] Figure 8 It is a schematic diagram of the state of the utility model during pressure relief.

[0037] In the figure: tool outer shell 1, cutting knife 2, end cover 3, lower gasket 4, thrust bearing 1 5, lower straightening bearing 6, base 7, connecting rod 8, anchor plate 9, upper straightening bearing 10, thrust bearing 2 11, upper transmission shaft 12, connector 13, upper retaining ring 14, upper gasket 15, anchor piston 16, piston guide rod 17, piston return spring 18, turbine 19, upper shell 20, cutting control piston 21, lower transmission shaft 22, pressure relief hole 22-1, cutting knife engagement shaft 23, pin shaft 24, cutting knife return spring 25. DETAILED DESCRIPTION

[0038] The accompanying drawings are for reference and illustration only and are not intended to limit the scope of protection of the present utility model. The technical solutions in the embodiments of the present utility model will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only part of the embodiments of the present utility model, not all of them. Based on the embodiments of the present utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present utility model.

[0039] In order to make the purpose, technical solution and advantages of the utility model more clear, 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 here are only used to explain the utility model and are not used to limit the utility model.

[0040] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, in the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0041] See also Figure 1-Figure 8A downhole casing cutting short section is provided with a casing cutting mechanism, wherein a cutter 2 in the casing cutting mechanism is fixed in a tool outer shell 1 through a pin shaft 24 and meshed with a cutter meshing shaft 23, wherein: a turbine drive mechanism mainly composed of a turbine 19 and an upper transmission shaft 12 is installed in an upper inner cavity of an upper shell 20, the turbine 19 is installed outside the upper transmission shaft 12, and an upper centering bearing 10 and a lower centering bearing 6 are respectively installed at the upper and lower ends of the turbine 19; an anchoring mechanism provided with an anchoring piston 16, a piston guide rod 17 and an anchoring plate 9 is installed in a sandwich wall cavity of the upper shell 20, the piston guide rod 17 is fixed in the upper shell 20 through a base 7, the anchoring piston 16 is installed outside the piston guide rod 17, and between the anchoring piston 16 and the base 7 A piston return spring 18 is installed, and the anchor piston 16 and the base 7 are connected to the anchor plate 9 at the opening of the wall cavity side of the upper shell 20 through the connecting rod 8 respectively; the two ends of the upper shell 20 are respectively connected to the connecting head 13 and the end cover 3, and an upper retaining ring 14 is also installed between the connecting head 13 and the upper shell 20; the upper retaining ring 14, the end cover 3, the upper transmission shaft 12 and the lower transmission shaft 22 are all provided with liquid flow channels, and the lower transmission shaft 22 is also provided with a pressure relief hole 22-1; the upper transmission shaft 12 is sequentially connected with the lower transmission shaft 22 equipped with the cutting control piston 21 and the tool outer shell 1, and the cutter engagement shaft 23 fixed at the lower end of the cutting control piston 21 is engaged with the cutter 2; a cutter return spring 25 is installed between the cutter engagement shaft 23 and the tool outer shell 1.

[0042] In the utility model, a casing cutting mechanism, a turbine driving mechanism and an anchoring mechanism are provided, and liquid flow channels are provided in the upper retaining ring 14 , the end cover 3 , the upper transmission shaft 12 and the lower transmission shaft 22 .

[0043] When the tool is lowered into the casing to the set cutting depth, the drilling fluid from the ground enters the upper transmission shaft 12 and the wall cavity of the upper shell 20 through the connector 13, and the anchor mechanism is first supported on the casing wall to ensure that the tool works stably during the cutting process. During the anchoring support process, when the hydraulic pressure of the drilling fluid increases, the hydraulic pressure presses the anchor piston 16 downward, and the connecting rod 8 connected to the anchor piston 16 and the base 7 pushes the anchor plate 19 outward and anchors it on the inner wall of the casing, ensuring the stability of the tool.

[0044] As the pressure of the drilling fluid continues to increase, the drilling fluid enters the upper cavity of the upper shell 20 through the upper transmission shaft 12 and the liquid flow channel in the upper retaining ring 4, drives the turbine 19 to rotate, and drives the lower transmission shaft 22 and the tool outer shell 1 to rotate together through the upper transmission shaft 12; at the same time, the continuously rising drilling fluid pushes the cutting control piston 21 installed in the lower transmission shaft 22 downward, and the cutter engagement shaft 23 drives the cutter 2 to rotate and gradually extend outward to cut the casing.

[0045] During the casing cutting process, the drilling fluid from the ground can flow along the upper retaining ring 14, the upper transmission shaft 12, the lower transmission shaft 22 and the liquid flow channel set in the end cover 3 to the annulus between the tool and the casing, thereby reducing the temperature and cooling the cutting knife 2 during cutting, thereby extending the service life of the cutting knife 2.

[0046] When the cutter 2 is extended to complete the cutting, the cutting control piston 21 just moves down to below the pressure relief hole 22-1 in the lower transmission shaft 22, and the drilling fluid in the lower transmission shaft 22 flows out from the pressure relief hole 22-1. The pressure of the drilling fluid on the cutting control piston 21 is reduced, and at the same time, under the action of the cutter return spring 25, the cutting control piston 21 no longer moves down.

[0047] The casing cutting completion can be conveniently and accurately judged on the ground by observing the pressure reduction of the drilling fluid. After the casing cutting is completed, the anchoring piston 16 in the anchoring mechanism and the cutter 2 in the casing cutting mechanism are reset respectively under the action of the piston reset spring 18 and the cutter reset spring 25.

[0048] The utility model has a simple structure and fully utilizes hydraulic pressure to work. Ground staff can conveniently manipulate and control the cutting process of the downhole casing through a pressure pump. It is easy to operate, has high cutting efficiency for the downhole casing, and has a good use effect.

[0049] On the basis of the above-mentioned embodiment 1, the utility model also has the following embodiments: A preferred embodiment: a thrust bearing 2 11 and an upper gasket 15 are further installed outside the upper transmission shaft 12 between the upper retaining ring 14 and the upper straightening bearing 10, and the diameter of the center hole of the upper gasket 15 is larger than the outer diameter of the upper transmission shaft 12 to form a liquid flow channel. After the thrust bearing 2 11 and the upper gasket 15 are installed, the assembly firmness of the upper transmission shaft 12 can be further increased and its working stability can be improved.

[0050] A preferred embodiment: the upper retaining ring 14 is a flange-shaped body and the outer diameter of the small diameter section is equal to or smaller than the inner diameter of the upper inner cavity of the upper shell 20. The center hole of the upper retaining ring 14 is larger than the upper outer diameter of the upper transmission shaft 12. A liquid flow channel is provided in the large diameter section body of the small diameter section of the upper retaining ring 14. The liquid flow channel is composed of more than three liquid flow holes and corresponds to the sandwich wall cavity of the upper shell 20. The drilling fluid from the ground can flow into the liquid flow channel of the upper transmission shaft 12 through the center hole of the upper retaining ring 14, and can also flow into the sandwich wall cavity of the upper shell 20 through the liquid flow channel in the upper retaining ring 14, and apply pressure to the anchor piston 16 installed therein, so that the anchor plate 19 in the anchor mechanism is anchored in the inner wall of the casing.

[0051] A preferred embodiment: the outer circle of the upper transmission shaft 12 is a non-equal diameter outer circle and the lower part is provided with an external thread to be threadedly connected with the lower transmission shaft 22; the liquid flow channel in the upper transmission shaft 12 is arranged in the small diameter section at the upper part of the upper transmission shaft 12, and the liquid flow channel is arranged in more than two; the inlet of the liquid flow channel in the upper transmission shaft 12 is connected with the liquid flow channel in the upper retaining ring 14 and the outlet of the liquid flow channel is connected with the liquid flow channel in the upper gasket 15; the thrust bearing 2 11 is also arranged outside the small diameter section at the upper part of the upper transmission shaft 12. In this way, the liquid flow channel in the upper transmission shaft 12 can bypass the thrust bearing 2 11 and be connected with the liquid flow channel in the upper gasket 15 below, which not only ensures the stable installation of the upper transmission shaft 12, but also ensures the transmission of hydraulic power to the turbine 19 installed in the upper inner cavity of the upper shell 20.

[0052] A preferred embodiment: a limit platform is provided on the top of the piston guide rod 17, the outer diameter of the limit platform is larger than the diameter of the center hole of the anchor piston 16, and the anchor piston 16 is sleeved outside the piston guide rod 17 below the limit platform.

[0053] A preferred embodiment: the two ends of the lower transmission shaft 22 are respectively provided with internal threads and external threads and can be respectively threadedly connected with the upper transmission shaft 12 and the tool outer shell 1; the upper and lower ends of the cutter reset spring 25 are respectively installed in the spring mounting seats provided at the lower end of the cutter engagement shaft 23 and the bottom of the tool outer shell 1; the lower part of the cutter engagement shaft 23 is provided with a rack and can mesh with the gear at the meshing end of the cutter 2. When the cutter engagement shaft 23 moves downward under the drive of the cutting control piston 21, the cutter 2 meshed therewith gradually extends outward and rotates the cutting sleeve under the drive of the tool outer shell 1.

[0054] A preferred embodiment: the lower transmission shaft 22 is a non-uniform outer circle and the outer diameter of the upper outer circle is larger than the outer diameter of the lower outer circle, forming a thrust bearing holding step; a thrust bearing 5 and a lower gasket 4 are installed between the lower part of the thrust bearing holding step and the end cover 3 to improve the assembly firmness and working stability of the lower transmission shaft 22.

[0055] A preferred embodiment: the aperture of the center hole of the lower gasket 4 is larger than the maximum outer diameter formed by the liquid flow channel in the end cover 3, which can ensure that the drilling fluid passes smoothly through the lower gasket 4 and the end cover 3; the inner cavity of the connector 13 is trumpet-shaped and the upper inner cavity is provided with an internal thread connected to the drill pipe, so that the tool can be lowered into the casing along with the drill string.

[0056] A preferred embodiment: at least two liquid flow channels are provided in the lower transmission shaft 22, and the inlet of the liquid flow channel is arranged in the main body above the thrust bearing clamping step, and the outlet of the liquid flow channel is arranged in the main body below the thrust bearing 5; the outlet of the liquid flow channel in the lower transmission shaft 22 and the pressure relief hole 22-1 both correspond to the center hole of the lower gasket 4, ensuring smooth liquid flow and timely pressure relief.

[0057] A preferred embodiment: the pressure relief holes 22-1 in the lower transmission shaft 22 are arranged in two or more and are downward inclined holes; the manufacturing material of the cutter head 2 is cemented carbide; the initial installation position of the cutting control piston 21 in the lower transmission shaft 22 is determined according to the distance between the outer circle of the tool outer shell 1 and the outer circle of the cut casing.

[0058] After the booster pump is turned on the ground, the drilling fluid enters the cutting sub through the connector 13. Under the continuous pressure of the drilling fluid, the anchor piston 16 is pushed downward along the piston guide rod 17. With the movement of the anchor piston 16, the connecting rod 8 rotates, and the anchor plate 9 moves outward, so that the entire cutting sub is fixed on the inner wall of the casing to prevent the cutter 2 from deflecting when it starts cutting.

[0059] At this time, the turbine 19 also starts to rotate under the hydraulic pressure of the drilling fluid, driving the upper transmission shaft 12, the lower transmission shaft 22 and the cutter housing 1 to rotate together, and the cutter housing 1 drives the cutter 2 to rotate. Under the action of the drilling fluid, the cutter engagement shaft 23 and the cutting control piston 21 move axially downward along the center hole of the lower transmission shaft 22, and the rack at the lower part of the cutter engagement shaft 23 drives the cutter 2 to rotate outward. When the cutter 2 extends to a certain length, the cutter 2 begins to contact the casing and starts to cut the casing.

[0060] When the casing cutting is completed, the cutting control piston 21 just moves downward to the lower part of the pressure relief hole 22-1 in the lower transmission shaft 22, and the drilling fluid in the lower transmission shaft 22 flows out from the pressure relief hole 22-1. When the pressure of the drilling fluid on the cutting control piston 21 is reduced, the cutting control piston 21 no longer moves downward under the action of the cutter return spring 25. The pressure reduction of the drilling fluid can be observed on the ground to determine whether the casing cutting is completed. After the casing cutting is completed, under the action of the cutting return spring 25 and the piston return spring 18, the cutter 2 and the anchoring piston 16 in the anchoring mechanism are all reset.

[0061] The embodiments described above are only typical embodiments, but the utility model is not limited to these embodiments, and those skilled in the art can make modifications without departing from the spirit and enlightenment of the utility model. Although the utility model is described in detail with reference to the aforementioned embodiments, for those skilled in the art, it is still possible to modify the technical solutions recorded in the aforementioned embodiments, or to replace some of the technical features therein by equivalents. Any modifications, equivalent replacements, improvements, etc. made within the creative spirit and creative concept of the utility model should be included in the protection scope of the utility model. Therefore, the protection scope is not limited to the above description.

Claims

1. A downhole casing cutting sub, provided with a casing cutting mechanism, wherein a cutter in the casing cutting mechanism is fixed in a tool housing through a pin and meshed with a cutter meshing shaft, wherein the cutter is characterized by: The turbine drive mechanism mainly composed of a turbine and an upper transmission shaft is installed in the upper inner cavity of the upper shell, the turbine is installed outside the upper transmission shaft, and an upper stabilizing bearing and a lower stabilizing bearing are respectively installed at the upper and lower ends of the turbine; an anchoring mechanism provided with an anchoring piston, a piston guide rod and an anchoring plate is installed in the sandwich wall cavity of the upper shell, the piston guide rod is fixed in the upper shell through a base, the anchoring piston is installed outside the piston guide rod, a piston reset spring is installed between the anchoring piston and the base, and the anchoring piston and the base are respectively connected to the anchoring plate at the side opening of the sandwich wall cavity of the upper shell through a connecting rod; the two ends of the upper shell are respectively connected to the connecting head and the end cover, and an upper retaining ring is also installed between the connecting head and the upper shell; liquid flow channels are all provided in the upper retaining ring, the end cover, the upper transmission shaft and the lower transmission shaft, and a pressure relief hole is also provided in the lower transmission shaft; the upper transmission shaft is sequentially connected with the lower transmission shaft equipped with a cutting control piston and a tool outer shell, and the cutter engagement shaft fixed at the lower end of the cutting control piston is engaged with the cutter; a cutter reset spring is installed between the cutter engagement shaft and the tool outer shell.

2. A downhole casing cutting sub as claimed in claim 1, characterized in that: A thrust bearing 2 and an upper gasket are also arranged outside the upper transmission shaft between the upper retaining ring and the upper straightening bearing. The diameter of the center hole of the upper gasket is larger than the outer diameter of the upper transmission shaft to form a liquid flow channel.

3. A downhole casing cutting sub as claimed in claim 2, characterized in that: The upper retaining ring is a flange-shaped body and the outer diameter of the small diameter section is equal to or smaller than the inner diameter of the upper inner cavity of the upper shell body. The center hole of the upper retaining ring is larger than the upper outer diameter of the upper transmission shaft. A liquid flow channel is provided in the large diameter section body on the outer periphery of the small diameter section of the upper retaining ring. The liquid flow channel is composed of more than three liquid flow holes and corresponds to the clamping wall cavity of the upper shell body.

4. A downhole casing cutting sub as claimed in claim 3, characterized in that: The outer circle of the upper transmission shaft is a non-uniform outer circle and the lower part is provided with an external thread which is threadedly connected to the lower transmission shaft; the liquid flow channel in the upper transmission shaft is arranged in the small diameter section at the upper part of the upper transmission shaft, and the liquid flow channels are arranged in more than two; the inlet of the liquid flow channel in the upper transmission shaft is connected with the liquid flow channel in the upper retaining ring and the outlet of the liquid flow channel is connected with the liquid flow channel in the upper gasket ring; the thrust bearing 2 is also arranged outside the small diameter section at the upper part of the upper transmission shaft.

5. The downhole casing cutting sub as claimed in claim 1, characterized in that: A limit platform is arranged on the top of the piston guide rod, the outer diameter of which is larger than the diameter of the center hole of the anchor piston, and the anchor piston is sleeved outside the piston guide rod below the limit platform.

6. A downhole casing cutting sub as claimed in claim 4, characterized in that: The two ends of the lower transmission shaft are respectively provided with internal threads and external threads and can be threadedly connected with the upper transmission shaft and the tool outer shell respectively; the upper and lower ends of the cutter reset spring are respectively installed in the spring mounting seats arranged at the lower end of the cutter engagement shaft and the bottom of the tool outer shell; the lower part of the cutter engagement shaft is provided with a rack and can mesh with the gear at the cutter engagement end.

7. A downhole casing cutting sub as claimed in claim 6, characterized in that: The lower transmission shaft has a non-uniform outer circle, and the outer diameter of the upper outer circle is larger than the outer diameter of the lower outer circle, forming a thrust bearing holding step; a thrust bearing and a lower gasket are installed between the lower part of the thrust bearing holding step and the end cover.

8. A downhole casing cutting sub as claimed in claim 7, characterized in that: The diameter of the center hole of the lower gasket ring is larger than the maximum outer diameter formed by the liquid flow channel in the end cover; the inner cavity of the connector is trumpet-shaped and the upper inner cavity is provided with internal threads to connect with the drill rod.

9. A downhole casing cutting sub as claimed in claim 8, characterized in that: There are at least two liquid flow channels in the lower transmission shaft, and the inlet of the liquid flow channel is arranged in the main body above the thrust bearing holding step, and the outlet of the liquid flow channel is arranged in the main body below the thrust bearing; the outlet and the pressure relief hole of the liquid flow channel in the lower transmission shaft correspond to the center hole of the lower gasket.

10. A downhole casing cutting sub as claimed in claim 9, characterized in that: The pressure relief holes in the lower transmission shaft are arranged in more than two and are downward inclined holes; the manufacturing material of the cutter head is cemented carbide; the initial installation position of the cutting control piston in the lower transmission shaft is determined according to the distance between the outer circle of the tool outer shell and the outer circle of the cut casing.

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