One-trip milling plug sweeping pipe column for tie-back well cementation

Abstract

The invention provides a one-trip type milling plug sweeping pipe column for tie-back well cementation, which comprises a feeding drilling tool and a plug sweeping drill bit arranged at the lower end of the feeding drilling tool, and the plug sweeping drill bit is configured to be capable of drilling and removing a cement plug in a casing pipe; the tie-back barrel grinding and milling tool is arranged above the plug sweeping drill bit, and the tie-back barrel grinding and milling tool can grind and mill a tie-back barrel; when the composite structure moves downwards to the position of the composite tail pipe rubber plug main body, the conventional tail pipe rubber plug enters the guide head to form a secondary composite structure; and under the action of pressure in the pipe, the shear pin is broken, and the secondary composite structure reaches the position of the ball seat to complete bump pressure. According to the method, the purposes of plug sweeping and tie-back barrel grinding and milling are achieved by tripping the drilling tool in one time, the tripping frequency is reduced, the tie-back well cementation construction time is shortened, the construction period is shortened, and cost reduction and efficiency improvement in the oil and gas development process are achieved.

Description

Technical Field

[0001] The present invention relates to a one-trip milling and plug cleaning string for tie-back cementing, belonging to the technical fields of cementing and well completion in oil and gas development. Background Art

[0002] Tie-back of liner means a process of running a casing with a tie-back tool connected to the bottom after the liner cementing is completed, and retrieving the casing from the liner hanger position back to the wellhead. Usually, it is necessary to remove the residual cement stone on the top of the tie-back cylinder of the liner hanger and mill and polish the tie-back cylinder before running the tie-back casing to ensure good sealing between the tie-back tool and the tie-back cylinder.

[0003] In engineering, the "three-trip drilling" process is often adopted before running the tie-back casing, that is, in the first trip, a bit suitable for the inner diameter of the upper casing is run to remove the residual cement stone above the bell mouth of the tie-back cylinder; in the second trip, a bit suitable for the inner diameter of the liner is run to remove the residual cement stone inside the tie-back cylinder and inside the liner hanger; in the third trip, a mill shoe adapted to the inner diameter of the tie-back cylinder is run to scrape and polish the inner wall of the tie-back cylinder. In this process, it is difficult to judge whether the first trip has drilled to the bell mouth of the tie-back cylinder or has damaged the bell mouth. If there is a cement ring left or the bell mouth is deformed, it will affect the running of the milling shoe or tie-back plug of the tie-back cylinder, and also increase the risk of seal failure of the tie-back plug. Often, it is necessary to run tools again to repair the tie-back cylinder, seriously affecting the engineering efficiency and causing serious losses to the petroleum engineering. Summary of the Invention

[0004] In view of the above technical problems existing in the prior art, the present invention provides a one-trip milling and plug cleaning string for tie-back cementing, which realizes the purposes of plug cleaning and milling the tie-back cylinder by running one trip of drill string, reduces the number of trips of tripping in and out of the well, shortens the construction time of tie-back cementing, shortens the construction period, and realizes cost reduction and efficiency increase in the process of oil and gas development.

[0005] The present invention provides a one-trip milling and plug cleaning string for tie-back cementing, comprising: A running-in drill string, A plug cleaning bit disposed at the lower end of the running-in drill string, the plug cleaning bit being configured to drill out the cement plug in the casing; and A tie-back cylinder milling tool disposed above the plug cleaning bit, the tie-back cylinder milling tool being capable of milling the tie-back cylinder.

[0006] A back connection cylinder milling tool is arranged above the plug removal bit. The entire pipe string is lowered into the wellbore by feeding the drill string. The plug removal bit at the front end drills out the cement plug in the casing. The back connection cylinder milling tool above the plug removal bit can mill the back connection cylinder at the upper end of the casing, realizing the construction of plug removal and milling in one trip of the pipe string. Compared with the conventional construction, it reduces the construction process of milling the back connection cylinder and tripping in and out of the well once, saving at least 2 - 3 days of the entire construction time and greatly improving the construction efficiency.

[0007] A further improvement of the present invention lies in that the back connection cylinder milling tool includes a milling tool body, and a back connection cylinder milling unit is arranged on the milling tool body.

[0008] A further improvement of the present invention lies in that the milling tool body includes an upper sub connecting the feed drill string and a lower sub connecting the plug removal bit; the back connection cylinder milling unit is arranged on the lower sub.

[0009] The back connection cylinder milling unit is used for milling the inside of the back connection cylinder to remove the cement ring adhering to the inner wall of the back connection cylinder, and its outer diameter matches the inner diameter of the back connection cylinder.

[0010] A further improvement of the present invention lies in that a back connection cylinder bellmouth repair unit is arranged on the milling tool body, and the back connection cylinder bellmouth repair unit is configured to be able to modify the bellmouth at the upper end of the back connection cylinder.

[0011] A further improvement of the present invention lies in that the milling tool body includes an upper sub and a lower sub. The upper sub is used to connect the feed drill string above, and the lower sub is used to connect the plug removal bit below; the back connection cylinder milling unit is arranged on the lower sub.

[0012] A further improvement of the present invention lies in that the milling tool body further includes a matching length joint, and the matching length joint is arranged between the back connection cylinder bellmouth repair unit and the back connection cylinder milling unit.

[0013] A further improvement of the present invention lies in that the matching length joint is preset in a variety of different length models, and different models of matching length joints are selected according to the type of back connection cylinder or multiple matching length joints are selected to be connected.

[0014] A further improvement of the present invention lies in that the matching length joint is drill pipes of different lengths, and their heads and tails can be connected. The upper end of the matching length joint is a female joint, and the lower end is a male joint; The matching length joint can be prefabricated in a variety of different length models, and different models or combinations of different models can be selected according to the type of back connection cylinder.

[0015] A further improvement of the present invention lies in that the back connection cylinder milling unit includes a mill shoe sub, and a number of milling ribs are arranged on the circumference of the mill shoe sub.

[0016] A further improvement of the present invention lies in that the back connection cylinder bell mouth repair unit includes a convex structure, the lower side of the convex structure is conical, and a plurality of wear-resistant blocks are arranged on the lower side of the convex structure.

[0017] A further improvement of the present invention lies in that the wear-resistant block is a cemented carbide block.

[0018] A further improvement of the present invention lies in that the wear-resistant block is in a strip structure, one end is arranged on the convex structure, the other end extends to the outside of the convex structure, and the middle part of the wear-resistant block is in fit with the cone.

[0019] A further improvement of the present invention lies in that the upper side of the convex structure is also conical, and the upper and lower ends are symmetrically arranged.

[0020] Compared with the prior art, the advantages of the present invention are as follows: According to the one-trip milling and plug sweeping string for back connection and cementing of the present invention, by lowering a drill string once, the plug sweeping bit and the back connection cylinder milling tool are lowered at one time to realize two functions of sweeping the cement plug and milling the back connection cylinder. After pulling out the drill string, the procedure of lowering the back connection string can be carried out. Compared with the conventional construction, the construction process of milling the back connection cylinder and tripping in and out of the well is reduced once, saving at least 2 to 3 days of time and greatly improving the construction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the drawings: Figure 1 Shown is a schematic structural view of a one-trip milling and plug sweeping string for back connection and cementing according to an embodiment of the present invention; Figure 2 Shown is a schematic structural view of a back connection cylinder milling tool according to an embodiment of the present invention; The drawings are not drawn to actual scale.

[0022] The meanings of the reference numerals in the drawings are as follows: 100, feeding drill string; 200, back connection cylinder milling tool; 300, plug sweeping bit; 201, upper sub; 202, back connection cylinder bell mouth repair unit; 203, matching length joint; 204, lower sub; 205, back connection cylinder milling unit. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] In order to make the technical solutions and advantages of the present invention clearer, the exemplary embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than an exhaustive list of all embodiments. And without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0024] The liner tie-back is a technique where, after the liner cementing is completed, a casing with a tie-back tool connected to its bottom end is run in, and the casing is tied back from the liner hanger position to the wellhead. Usually, before running in the tie-back casing, it is necessary to remove the residual cement stone at the top of the tie-back cylinder of the liner hanger and mill and polish the tie-back cylinder to ensure good sealing between the tie-back tool and the tie-back cylinder.

[0025] In engineering, the "three-trip drilling" technique is often adopted before running in the tie-back casing. That is, in the first trip, a bit suitable for the inner diameter of the upper casing is run in to remove the residual cement stone above the bell mouth of the tie-back cylinder; in the second trip, a bit suitable for the inner diameter of the liner is run in to remove the residual cement stone inside the tie-back cylinder and the liner hanger; in the third trip, a mill shoe suitable for the inner diameter of the tie-back cylinder is run in to scrape and polish the inner wall of the tie-back cylinder. In this technique, it is difficult to judge whether the first trip has drilled to the bell mouth of the tie-back cylinder or has damaged the bell mouth. If there is a cement ring left or the bell mouth is deformed, it will affect the running in of the mill shoe for milling the tie-back cylinder or the tie-back plug, and also increase the risk of seal failure of the tie-back plug. Often, it is necessary to run in tools again to repair the tie-back cylinder, seriously affecting the engineering efficiency and causing serious losses to the petroleum engineering.

[0026] To solve the above problems, the present invention proposes a one-trip milling and plug removal string for tie-back cementing, which realizes the purpose of plug removal and milling of the tie-back cylinder by running in one trip of drill string, reduces the number of trips of tripping in and out of the well, shortens the construction time of tie-back cementing, shortens the construction period, and realizes cost reduction and efficiency increase in the process of oil and gas development.

[0027] In the embodiment as Figure 1 shown, a one-trip milling and plug removal string for tie-back cementing includes: a running-in drill string 100.

[0028] A plug removal bit 300 disposed at the lower end of the running-in drill string 100, the plug removal bit 300 being configured to drill out the cement plug in the casing; and A tie-back cylinder milling tool 200 disposed at the upper end of the plug removal bit 300, the tie-back cylinder milling tool 200 being capable of milling the tie-back cylinder.

[0029] In the one-trip milling and plug removal string according to this embodiment, the tie-back cylinder milling tool 200 is disposed above the plug removal bit 300. The entire string is run into the well through the running-in drill string 100. The front plug removal bit 300 drills out the cement plug in the casing, and the tie-back cylinder milling tool 200 above the plug removal bit 300 can mill the tie-back cylinder at the upper end of the casing, realizing plug removal and milling construction in one trip of the string. Compared with the conventional construction, it reduces the construction process of milling the tie-back cylinder and tripping in and out of the well once, saving at least 2 - 3 days of the entire construction time and greatly improving the construction efficiency.

[0030] In one embodiment, the back connection cylinder milling tool 200 includes a milling tool body, and a back connection cylinder milling unit 205 is provided on the milling tool body.

[0031] The back connection cylinder milling unit 205 is used for milling the inside of the back connection cylinder to remove the cement ring attached to the inner wall of the back connection cylinder, and its outer diameter matches the inner diameter of the back connection cylinder.

[0032] In this embodiment, the milling tool body includes an upper sub 201 and a lower sub 204. The upper sub 201 is used to connect the feeding drill string 100 above, and the lower sub 204 is used to connect the plug removal bit 300 below. Preferably, the back connection cylinder milling unit 205 is provided on the lower sub 204.

[0033] In this embodiment, the back connection cylinder milling unit 205 includes a plurality of milling ribs arranged circumferentially. The milling ribs are strip-shaped structures and are arranged in a circle circumferentially. The milling ribs are arranged axially or have a certain angle in the oblique direction.

[0034] In the one-trip milling and plug removal string according to this embodiment, the back connection cylinder milling tool 200 is provided with milling ribs, which are arranged in a circle circumferentially to form a milling structure protruding in the circumferential direction, and can mill the back connection cylinder at the upper end of the casing, realizing the construction of plug removal and milling simultaneously in one trip of the pipe string.

[0035] In one embodiment, the milling tool body further includes a plurality of drill pipes, and the drill pipes are arranged between the upper sub 201 and the lower sub 204. A back connection cylinder bellmouth repair unit 202 is provided on the drill pipe or the upper sub 201, and the back connection cylinder bellmouth repair unit 202 can modify the bellmouth at the upper end of the back connection cylinder.

[0036] In the one-trip milling and plug removal string according to this embodiment, the back connection cylinder bellmouth repair unit 202 is provided on the milling tool body, which can repair the damaged back connection cylinder bellmouth and avoid the difficulty of inserting the back connection plug caused by the bellmouth curling.

[0037] In a preferred embodiment, the milling tool body further includes a length matching sub 203, and the length matching sub 203 is arranged between the back connection cylinder bellmouth repair unit 202 and the milling ribs, and is used to adjust the distance between the back connection cylinder bellmouth repair unit 202 and the milling ribs to adapt to different types of back connection cylinders.

[0038] In this embodiment, the length matching sub 203 is drill pipes of different lengths, and their heads and tails can be connected. Preferably, the upper end of the length matching sub 203 is a female joint and the lower end is a male joint.

[0039] The matching short and long joints 203 can be prefabricated in various models with different lengths, and different models or combinations of different models can be selected according to the type of the tie-back cylinder.

[0040] In one embodiment, the tie-back cylinder milling unit 205 includes a mill shoe sub, and a plurality of milling ribs are arranged on the circumference of the mill shoe sub. The lower end of the mill shoe sub is connected to a plug cleaning bit 300 through a section of running drill string 100. The milling ribs are strip-shaped structures and are arranged in a circle along the circumference. The milling ribs are arranged axially or have a certain angle in the oblique direction.

[0041] In one embodiment, the tie-back cylinder bellmouth repair unit 202 includes a convex structure, the lower side of the convex structure is conical, and a plurality of wear-resistant blocks are arranged on the lower side of the convex structure. In one embodiment, the upper side of the convex structure is also conical, and the upper and lower ends are symmetrically arranged.

[0042] Preferably, the wear-resistant blocks are cemented carbide blocks.

[0043] The wear-resistant blocks are strip-shaped structures, one end is arranged on the convex structure, the other end extends to the outside of the convex structure, and the middle part of the wear-resistant block fits with the cone.

[0044] The following is described in conjunction with specific embodiments.

[0045] Embodiment 1 A one-trip milling and plug cleaning string for tie-back cementing, which includes: a running drill string 100.

[0046] A plug cleaning bit 300 arranged at the lower end of the running drill string 100, the plug cleaning bit 300 is configured to drill out the cement plug in the casing; and A tie-back cylinder milling tool 200 arranged at the upper end of the plug cleaning bit 300, the tie-back cylinder milling tool 200 can mill the tie-back cylinder.

[0047] The tie-back cylinder milling tool 200 includes a milling tool body, and a tie-back cylinder milling unit 205 is arranged on the milling tool body.

[0048] The tie-back cylinder milling unit 205 is used to mill the inside of the tie-back cylinder to remove the cement ring attached to the inner wall of the milled tie-back cylinder, and its outer diameter matches the inner diameter of the tie-back cylinder.

[0049] The milling tool body includes an upper sub 201 and a lower sub 204. The upper sub 201 is used to connect the upper running drill string 100, and the lower sub 204 is used to connect the lower plug cleaning bit 300. Preferably, the tie-back cylinder milling unit 205 is arranged on the lower sub 204.

[0050] The back connection cylinder milling unit 205 includes a number of milling ribs arranged circumferentially. The milling ribs are strip-shaped structures and are arranged in a circle circumferentially. The milling ribs are arranged axially or have a certain angle in the oblique direction. The back connection cylinder milling tool 200 is provided with milling ribs, which are arranged in a circle circumferentially, forming a milling structure protruding in the circumferential direction, capable of milling the back connection cylinder at the upper end of the casing, realizing the construction of plug cleaning and milling in one trip of the pipe string.

[0051] The milling tool body further includes a number of drill pipes, which are arranged between the upper sub 201 and the lower sub 204. The drill pipe or the upper sub 201 is provided with a back connection cylinder bellmouth repair unit 202, which can modify the bellmouth at the upper end of the back connection cylinder. The back connection cylinder bellmouth repair unit 202 is provided on the milling tool body, which can repair the damaged back connection cylinder bellmouth and avoid the difficulty of inserting the back connection plug caused by the bellmouth curling.

[0052] The milling tool body further includes a matching length joint 203, which is arranged between the back connection cylinder bellmouth repair unit 202 and the milling ribs, and is used to adjust the distance between the back connection cylinder bellmouth repair unit 202 and the milling ribs to adapt to different types of back connection cylinders.

[0053] The matching length joint 203 is drill pipes of different lengths, and their heads and tails can be connected. The matching length joint 203 can be prefabricated in a variety of different length models, and different models can be selected according to the type of back connection cylinder.

[0054] The back connection cylinder milling unit 205 includes a mill shoe sub, and a number of milling ribs are arranged on the circumference of the mill shoe sub. The lower end of the mill shoe sub is connected to the plug cleaning bit 300 through a section of running drill string 100. The milling ribs are strip-shaped structures and are arranged in a circle circumferentially. The milling ribs are arranged axially or have a certain angle in the oblique direction.

[0055] The back connection cylinder bellmouth repair unit 202 includes a convex structure, the lower side of the convex structure is conical, and a number of wear-resistant blocks are arranged on the lower side of the convex structure. In one embodiment, the upper side of the convex structure is also conical, and the upper and lower ends are symmetrically arranged.

[0056] The wear-resistant block is a strip-shaped structure, one end is arranged on the convex structure, and the other end extends to the outside of the convex structure, and the middle part of the wear-resistant block fits with the cone.

[0057] Embodiment 2 A one-trip milling and plug cleaning pipe string for back connection cementing, which includes: a running drill string 100.

[0058] A milling bit 300 disposed at the lower end of the drill string 100 for feeding, the milling bit 300 being configured to drill out the cement plug in the casing; and A back connection cylinder milling tool 200 disposed at the upper end of the milling bit 300, the back connection cylinder milling tool 200 being capable of milling the back connection cylinder.

[0059] The back connection cylinder milling tool 200 includes a milling tool body, and a back connection cylinder milling unit 205 is disposed on the milling tool body.

[0060] The back connection cylinder milling unit 205 is used to mill the inside of the back connection cylinder to remove the cement ring adhering to the inner wall of the milled back connection cylinder, and its outer diameter matches the inner diameter of the back connection cylinder.

[0061] The milling tool body includes an upper sub 201 and a lower sub 204. The upper sub 201 is used to connect the drill string 100 above, and the lower sub 204 is used to connect the milling bit 300 below. Preferably, the back connection cylinder milling unit 205 is disposed on the lower sub 204.

[0062] The back connection cylinder milling unit 205 includes a plurality of milling ribs arranged circumferentially. The milling ribs are strip-shaped structures and are arranged in a circle circumferentially. The milling ribs are arranged axially or have a certain angle in the oblique direction. The back connection cylinder milling tool 200 is provided with milling ribs, which are arranged in a circle circumferentially to form a milling structure protruding in the circumferential direction, capable of milling the back connection cylinder at the upper end of the casing, realizing the construction of plug cleaning and milling in one trip of the pipe.

[0063] The milling tool body further includes a plurality of drill pipes, and the drill pipes are disposed between the upper sub 201 and the lower sub 204. A back connection cylinder bellmouth repair unit 202 is disposed on the drill pipe or the upper sub 201, and the back connection cylinder bellmouth repair unit 202 can modify the bellmouth at the upper end of the back connection cylinder. The back connection cylinder bellmouth repair unit 202 is disposed on the milling tool body, which can repair the damaged back connection cylinder bellmouth and avoid the difficulty of inserting the back connection plug caused by the bellmouth curling.

[0064] The milling tool body further includes a matching length joint 203, and the matching length joint 203 is disposed between the back connection cylinder bellmouth repair unit 202 and the milling ribs, and is used to adjust the distance between the back connection cylinder bellmouth repair unit 202 and the milling ribs to adapt to different types of back connection cylinders.

[0065] The matching length joint 203 is a drill pipe with different lengths, and its head and tail can be connected. Multiple matching length joints 203 can be provided, and multiple matching length joints 203 are connected according to needs to adapt to different length requirements.

[0066] The back connection cylinder milling unit 205 includes a milling shoe joint, and a plurality of milling ribs are arranged on the circumference of the milling shoe joint. The lower end of the milling shoe joint is connected to a milling plug bit 300 through a section of running drill pipe 100. The milling ribs are in a strip structure and are arranged in a circle along the circumference. The milling ribs are arranged axially or have a certain angle in the oblique direction.

[0067] The back connection cylinder bell mouth repair unit includes a convex structure. The lower side of the convex structure is conical, and a plurality of wear-resistant blocks are arranged on the lower side of the convex structure. In one embodiment, the upper side of the convex structure is also conical, and the upper and lower ends are symmetrically arranged.

[0068] The wear-resistant block is in a strip structure. One end is arranged on the convex structure, and the other end extends to the outside of the convex structure. The middle part of the wear-resistant block fits with the cone.

[0069] In the one-trip milling and plug milling string according to this embodiment, a back connection cylinder milling tool is arranged above the plug milling bit. The whole string is lowered into the well through the running drill pipe. The front plug milling bit drills out the cement plug in the casing. The back connection cylinder milling tool above the plug milling bit can mill the back connection cylinder at the upper end of the casing, realizing the construction of plug milling and milling at the same time in one trip. Compared with the conventional construction, it reduces the construction process of milling the back connection cylinder and tripping once, saving at least 2 - 3 days of the whole construction time and greatly improving the construction efficiency.

[0070] Embodiment 3 A one-trip milling and plug milling string for back connection cementing, which includes: a running drill pipe 100.

[0071] A plug milling bit 300 arranged at the lower end of the running drill pipe 100, and the plug milling bit 300 is configured to drill out the cement plug in the casing; and A back connection cylinder milling tool 200 arranged at the upper end of the plug milling bit 300, and the back connection cylinder milling tool 200 can mill the back connection cylinder.

[0072] The back connection cylinder milling tool 200 includes a milling tool body, and a back connection cylinder milling unit 205 is arranged on the milling tool body.

[0073] The back connection cylinder milling unit 205 is used to mill the inside of the back connection cylinder to remove the cement ring attached to the inner wall of the milled back connection cylinder, and its outer diameter matches the inner diameter of the back connection cylinder.

[0074] The milling tool body includes an upper sub 201 and a lower sub 204. The upper sub 201 is used to connect the upper running drill pipe 100, and the lower sub 204 is used to connect the lower plug milling bit 300. Preferably, the back connection cylinder milling unit 205 is arranged on the lower sub 204.

[0075] The back connection cylinder milling unit 205 includes a plurality of milling ribs arranged circumferentially. The milling ribs are strip-shaped structures arranged in a circle circumferentially. The milling ribs are arranged axially or at a certain angle in the oblique direction. The back connection cylinder milling tool 200 is provided with milling ribs arranged in a circle circumferentially, forming a milling structure protruding in the circumferential direction, which can mill the back connection cylinder at the upper end of the casing, realizing the construction of plug cleaning and milling in one trip of the pipe.

[0076] The milling tool body further includes a plurality of drill pipes, and the drill pipes are arranged between the upper sub 201 and the lower sub 204. The back connection cylinder bellmouth repair unit 202 is provided on the drill pipe or the upper sub 201, and the back connection cylinder bellmouth repair unit 202 can modify the bellmouth at the upper end of the back connection cylinder. The back connection cylinder bellmouth repair unit 202 is provided on the milling tool body, which can repair the damaged back connection cylinder bellmouth and avoid the difficulty of inserting the back connection plug caused by the bellmouth curling.

[0077] The milling tool body further includes a matching length joint 203, and the matching length joint 203 is arranged between the back connection cylinder bellmouth repair unit 202 and the milling ribs, and is used to adjust the distance between the back connection cylinder bellmouth repair unit 202 and the milling ribs to adapt to different types of back connection cylinders.

[0078] The matching length joint 203 is a drill pipe with different lengths, and its head and tail can be connected. The matching length joint 203 can be prefabricated in a variety of different length models, and different models can be selected according to the type of back connection cylinder.

[0079] The back connection cylinder milling unit 205 includes a mill shoe sub, and a plurality of milling ribs are arranged on the circumference of the mill shoe sub. The lower end of the mill shoe sub is connected to the plug cleaning bit 300 through a section of running drill string 100. The milling ribs are strip-shaped structures arranged in a circle circumferentially. The milling ribs are arranged axially or at a certain angle in the oblique direction.

[0080] The back connection cylinder bellmouth repair unit 202 includes a convex structure, the lower side of the convex structure is conical, and a plurality of wear-resistant blocks are arranged on the lower side of the convex structure. In one embodiment, the upper side of the convex structure is also conical, and the upper and lower ends are symmetrically arranged.

[0081] The wear-resistant blocks are strip-shaped structures, and the wear-resistant blocks are inclined axially.

[0082] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should extend to equivalent alternatives of these features understood by those of ordinary skill in the relevant art. It should also be understood that the terms used herein are for the purpose of describing specific embodiments only and do not mean to limit.

[0083] In the description of the present invention, unless otherwise specified, "a plurality of" means two or more; the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. is based on the orientation or positional relationship shown in the drawings, and is 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 thus cannot be construed as a limitation on the present invention. In addition, terms such as "first", "second", "third", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0084] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0085] Certain terms are used throughout this application to refer to particular system components. As those skilled in the art will recognize, the same components may generally be referred to by different names, and thus this application is not intended to distinguish components that differ only in name and not in function. The phrase "an embodiment" or "embodiment" as used in the specification means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the phrase "an embodiment" or "embodiment" that appears throughout the specification does not necessarily refer to the same embodiment.

[0086] The embodiments of the present invention are given for purposes of illustration and description, and are not exhaustive or limit the present invention to the disclosed form. Many modifications and variations are obvious to those of ordinary skill in the art. The embodiments are chosen and described in order to better explain the principles of the present invention and its practical application, and to enable those of ordinary skill in the art to understand the present invention and design various embodiments with various modifications suitable for a particular purpose.

[0087] Although the preferred embodiments of the present invention have been described, additional changes and modifications can be made by those skilled in the art once they learn of the basic inventive concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and / or modifications that fall within the scope of the present invention. All changes and / or modifications made in accordance with the embodiments of the present invention should be covered within the protection scope of the present invention.

Claims

1. A one-trip milling and plug cleaning string for tie-back cementing, characterized in that, Comprising: A drill string feeder (100), A plug milling bit (300) provided at the lower end of the drill string feeder (100), the plug milling bit (300) being configured to drill out a cement plug in the casing; and A tie-back cylinder milling tool (200) provided above the plug milling bit (300), the tie-back cylinder milling tool (200) being capable of milling the tie-back cylinder.

2. The one-trip milling and plug-cleaning string for tie-back cementing according to claim 1, wherein The tie-back cylinder milling tool (200) includes a milling tool body, and a tie-back cylinder milling unit (205) is provided on the milling tool body.

3. The one-trip milling and plug cleaning string for tie-back cementing according to claim 2, wherein, The milling tool body includes an upper sub (201) connecting the drill string feeder (100), and a lower sub (204) connecting the plug milling bit (300); the tie-back cylinder milling unit (205) is provided on the lower sub (204).

4. The one-trip milling and plug sweeping string for tie-back cementing according to claim 3, wherein A tie-back cylinder bellmouth repair unit (202) is provided on the milling tool body, and the tie-back cylinder bellmouth repair unit (202) is configured to modify the bellmouth at the upper end of the tie-back cylinder.

5. The one-trip milling and plug-cleaning string for tie-back cementing according to claim 4, wherein The milling tool body further includes a length matching sub (203), and the length matching sub (203) is provided between the tie-back cylinder bellmouth repair unit (202) and the tie-back cylinder milling unit (205).

6. The one-trip milling and plug cleaning string for tie-back cementing according to claim 5, wherein The length matching sub (203) is preset with multiple models of different lengths, and different models of the length matching sub (203) are selected according to the type of the tie-back cylinder, or multiple length matching subs (203) are selected to be connected.

7. The one-trip milling and plug-cleaning string for tie-back cementing according to claim 6, characterized in that, The tie-back cylinder milling unit (205) includes a mill shoe sub, and a plurality of milling ribs are provided on the circumference of the mill shoe sub.

8. The one-trip milling and plug sweeping string for tie-back cementing according to claim 7, characterized in that, The tie-back cylinder bellmouth repair unit (202) includes a convex structure, the lower side of the convex structure is conical, and a plurality of wear-resistant blocks are provided on the lower side of the convex structure.

9. The one-trip milling and plug cleaning string for tie-back cementing according to claim 8, wherein The wear-resistant block is a cemented carbide block.

10. The one-trip milling and plug-cleaning string for tie-back cementing according to claim 8, wherein, The wear-resistant block is in a strip structure, one end is provided on the convex structure, the other end extends to the outside of the convex structure, and the middle of the wear-resistant block is in contact with the cone.

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