Self-sealing plug for casing

Abstract

The present invention belongs to the technical field of downhole tools for oil and gas field development and application, and specifically relates to a self-sealing plug for casing, which aims to solve the problem of leakage of the switch gate of the main gate of the wellhead in the prior art. The present application provides a self-sealing plug for casing, including an upper joint, a hydraulically controlled one-way valve, a self-sealing piston cylinder, a self-sealing bridge plug and a hollow guide cone connected in sequence. The fluid enters the self-sealing bridge plug from the bottom to the top from the hollow guide cone, and then pushes the self-sealing piston in the self-sealing piston cylinder to move upward, thereby causing the hollow guide cone to squeeze and compress the sealing assembly of the self-sealing bridge plug, so that the sealing assembly expands radially. The self-sealing plug for casing of the present application has a reasonable structure, is safe and reliable, is easy to operate, and has a low cost. It can win precious time for replacing the main gate of the wellhead and solve the wellhead safety problem in a timely manner.

Description

Technical Field

[0001] The invention belongs to the technical field of downhole tools for oil and gas field development and application, and in particular relates to a self-sealing plugger for casing. Background Art

[0002] Usually, when the switch gate of the main gate of a casing fracturing well leaks, it is necessary to put a continuous tubing under pressure to insert the casing plug. After the seal is qualified, the construction process of replacing the main gate of the wellhead is carried out. As an important equipment for downhole operations, the continuous tubing is limited in number, and more important construction processes need to be given priority in production operations. Other processes that require pressure operations can only be carried out on a chosen day. In addition, the freezing temporary plugging and wellhead replacement technology can also be used to solve the above problems. This technical process requires injecting a temporary plugging agent into the pressure isolation area, and generating a freezing temporary plugging bridge plug through freezing to achieve the effect of isolating the pressure. The above two construction processes have a long construction period and high cost. Summary of the invention

[0003] In order to solve the above-mentioned problems in the prior art, that is, to solve the problem of leakage of the switch gate of the wellhead main gate in the prior art, the present application provides a self-sealing plug for casing, including an upper joint, a hydraulically controlled one-way valve, a self-sealing piston cylinder, a self-sealing bridge plug and a hollow guide cone connected in sequence;

[0004] The hydraulically controlled one-way valve only allows the fluid to flow in a one-way manner from top to bottom;

[0005] A self-sealing piston with a closed upper end is movably arranged in the self-sealing piston cylinder, and the self-sealing piston divides the inner cavity of the self-sealing piston cylinder into an upper piston cavity and a lower piston cavity;

[0006] The self-sealing bridge plug comprises a first tubular structure and a setting assembly sleeved on the first tubular structure; the upper end of the first tubular structure is coaxially connected to the lower end of the self-sealing piston, and a through hole is provided on the side wall of the first tubular structure to enable the inner cavity of the first tubular structure to communicate with the lower piston cavity;

[0007] The lower end of the first tubular structure is fixed to the hollow guide cone and the inner cavity is connected, and the setting assembly is limited between the self-sealing piston cylinder and the hollow guide cone;

[0008] When the self-sealing piston moves upward, the first tubular structure can drive the hollow guide cone to squeeze and compress the setting assembly, so that the setting assembly expands radially.

[0009] In some preferred technical schemes, the sealing assembly includes a cava seat, an upper cava, a second tubular structure, a rubber cylinder, a third tubular structure and a lower cava arranged in sequence from top to bottom, the second tubular structure and the third tubular structure are connected by a pin, and the rubber cylinder is limited between the second tubular structure and the third tubular structure. After the pin is sheared, the second tubular structure and the third tubular structure can move toward each other to squeeze and compress the rubber cylinder.

[0010] In some preferred technical schemes, the hydraulically controlled one-way valve includes a shell, a hydraulically controlled piston, a valve core and an elastic element. An upper fluid channel and a lower fluid channel are formed inside the shell. The upper fluid channel and the lower fluid channel are connected through a flow hole. The upper fluid channel is also connected to the inner cavity of the upper joint, and the lower fluid channel is also connected to the upper piston cavity. The hydraulically controlled piston can be slidably installed in a first U-shaped groove inside the shell, and the first U-shaped groove is located below the lower port of the inner cavity of the upper joint. The upper end of the valve core passes through the flow hole and the first U-shaped groove and is fixedly connected to the hydraulically controlled piston. The lower end of the valve core can be slidably arranged in a second U-shaped groove inside the shell. A spring groove is arranged at the bottom of the valve core. The elastic element is placed in the spring groove and is restricted between the top surface of the spring groove and the bottom surface of the second U-shaped groove. Driven by the elastic element, the valve core moves up and blocks the flow hole.

[0011] In some preferred technical solutions, the flow hole includes a first hole segment and a second hole segment, the first hole segment is arranged above the second hole segment, and the inner diameter of the first hole segment is smaller than the second hole diameter.

[0012] In some preferred technical solutions, the valve core includes a connecting rod and a sealing part connected in sequence from top to bottom, and the upper end of the sealing part is provided with a sealing surface that can match the inner diameter of the flow hole, and the sealing surface is inclined.

[0013] In some preferred technical solutions, the opening directions of the first U-shaped groove and the second U-shaped groove are arranged in opposite directions, the upper fluid channel is arranged at the opening end of the first U-shaped groove, and the lower fluid channel is arranged at the opening end of the second U-shaped groove.

[0014] In some preferred technical solutions, the first tubular structure and the hollow guide cone are integrally formed.

[0015] In some preferred technical solutions, the first tubular structure is detachably connected to the self-sealing piston.

[0016] In some preferred technical solutions, the second tubular structure and the third tubular structure are both cones, that is, the second tubular structure includes an upper cone, and the third tubular structure includes a lower cone. The inner diameter of the bottom end of the upper cone matches the outer diameter of the top end of the lower cone, and the top of the lower cone is connected to the upper cone by a pin. Specifically, the pin is arranged to penetrate the upper cone horizontally, and partially penetrates the lower cone. The upper cone and the lower cone are arranged oppositely, that is, the outer diameter of the bottom end of the upper cone is greater than the outer diameter of the top end of the upper cone, and the outer diameter of the bottom end of the lower cone is smaller than the outer diameter of the top end of the lower cone. In addition, the upper slip is sleeved on the outside of the upper cone, and the bottom end of the lower cone is sleeved in the lower slip and is smaller than the bottom end of the hollow guide cone, and the outer diameter of the top end of the lower cone is greater than the outer diameter of the rubber cylinder, so that the hollow guide cone moves upward to make the lower slip expand radially, and the lower cone compresses the rubber cylinder upward under the drive of the hollow guide cone, and the rubber cylinder then drives the upper cone to make the upper slip expand radially.

[0017] In some preferred technical solutions, there are multiple through holes on the side wall of the first tubular structure, and the multiple through holes are evenly arranged along the circumference of the first tubular structure.

[0018] In some preferred technical solutions, shoulder rings are respectively provided at the upper and lower ends of the rubber cylinder.

[0019] The self-sealing plug for casing of the present invention utilizes the high-pressure fluid pressure in the wellbore to flow into the first tubular structure through the hollow guide cone, and then acts on the self-sealing piston through the through hole, pushing the self-sealing piston upward and driving the first tubular structure and the hollow guide cone to move upward together, so that the second tubular structure and the third tubular structure squeeze the rubber cylinder to achieve automatic sealing under the action of the pressure fluid in the well. The present invention has a reasonable structure, is safe and reliable, is easy to operate, and has a low cost. It can save precious time for replacing the main gate of the wellhead and solve the wellhead safety problem in a timely manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0021] Figure 1 This is a schematic diagram of the overall structure of a self-sealing plug for a casing according to an embodiment of the present invention;

[0022] Figure 2 It is a structural schematic diagram of a hydraulically controlled one-way valve in an embodiment of the present invention;

[0023] List of reference numerals:

[0024] 1-upper joint, 2-hydraulic one-way valve, 201-housing, 202-hydraulic piston, 203-valve core, 2031-connecting rod, 2032-sealing part, 204-elastic element, 205-upper fluid channel, 206-lower fluid channel, 207-flow hole, 208-first U-shaped groove, 209-second U-shaped groove, 210-spring groove, 3-self-sealing piston cylinder, 301-upper piston chamber, 302-lower piston chamber, 4-self-sealing piston, 5-self-sealing bridge plug, 501-first tubular structure, 5011-connecting hole, 502-slip seat, 503-upper slip, 504-second tubular structure, 505-rubber cylinder, 506-third tubular structure, 507-lower slip, 508-pin, 509-upper shoulder ring, 510-lower shoulder ring, 6-hollow guide cone. DETAILED DESCRIPTION

[0025] In order to make the embodiments, technical solutions and advantages of the present invention more obvious, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are part of the embodiments of the present invention, rather than all the embodiments. It should be understood by those skilled in the art that these implementation modes are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0026] The self-sealing plug for casing of the present invention comprises an upper joint, a hydraulically controlled one-way valve, a self-sealing piston cylinder, a self-sealing bridge plug and a hollow guide cone which are connected in sequence;

[0027] The hydraulically controlled one-way valve only allows the fluid to flow in one direction from top to bottom;

[0028] A self-sealing piston with a closed upper end is movably arranged in the self-sealing piston cylinder, and the self-sealing piston divides the inner cavity of the self-sealing piston cylinder into an upper piston cavity and a lower piston cavity;

[0029] The self-sealing bridge plug comprises a first tubular structure and a setting assembly sleeved on the first tubular structure; the upper end of the first tubular structure is coaxially connected to the lower end of the self-sealing piston, and a through hole is provided on the side wall of the first tubular structure to achieve communication between the inner cavity of the first tubular structure and the lower piston cavity;

[0030] The lower end of the first tubular structure is fixed to the hollow guide cone and the inner cavity is connected, and the setting assembly is limited between the self-sealing piston cylinder and the hollow guide cone;

[0031] When the self-sealing piston moves upward, the first tubular structure can drive the hollow guide cone to squeeze and compress the setting assembly, so that the setting assembly expands in the radial direction.

[0032] In order to more clearly illustrate the self-sealing plug for cannula of the present invention, a preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

[0033] As a preferred embodiment of the present invention, the self-sealing plugging device for cannula of the present invention is as follows Figure 1 As shown, it includes an upper joint 1, a hydraulically controlled one-way valve 2, a self-sealing piston cylinder 3, a self-sealing bridge plug 5 and a hollow guide cone 6 which are connected in sequence;

[0034] The hydraulically controlled one-way valve 2 only allows the fluid to flow in one direction from top to bottom;

[0035] A self-sealing piston 4 with a sealed upper end is movably disposed in the self-sealing piston cylinder 3, and the self-sealing piston 4 divides the inner cavity of the self-sealing piston cylinder 3 into an upper piston cavity 301 and a lower piston cavity 302;

[0036] The self-sealing bridge plug 5 includes a first tubular structure 501 and a sealing assembly sleeved on the outside of the first tubular structure 501; the upper end of the first tubular structure 501 is coaxially connected to the lower end of the self-sealing piston 4, and the side wall of the first tubular structure 501 is provided with a through hole to achieve communication between the inner cavity of the first tubular structure 501 and the lower piston cavity 302; preferably, there are multiple through holes on the side wall of the first tubular structure 501, and the multiple through holes are evenly arranged along the circumference of the first tubular structure 501.

[0037] The lower end of the first tubular structure 501 is fixed to the hollow guide cone 6 and the inner cavity is coaxially connected, and the sealing assembly is limited between the self-sealing piston cylinder 3 and the hollow guide cone 6; it can be understood that a through hole is set in the center of the hollow guide cone 6 of the present application.

[0038] When the self-sealing piston 4 moves upward, the first tubular structure 501 can drive the hollow guide cone 6 to squeeze and compress the setting assembly, so that the setting assembly expands in the radial direction.

[0039] Furthermore, the sealing assembly includes a cava seat 502, an upper cava 503, a second tubular structure 504, a rubber cylinder 505, a third tubular structure 506 and a lower cava 507 which are arranged in sequence from top to bottom. The second tubular structure 504 and the third tubular structure 506 are connected by a pin 508, and the rubber cylinder 505 is limited between the second tubular structure 504 and the third tubular structure 506. After the pin 508 is sheared, the second tubular structure 504 and the third tubular structure 506 can move toward each other to squeeze and compress the rubber cylinder 505.

[0040] In some preferred embodiments, the hydraulically controlled one-way valve includes a shell 201, a hydraulically controlled piston 202, a valve core 203 and an elastic element 204, the upper part of the shell 201 is threadedly sealed and connected to the upper joint 1, the lower part of the shell 201 is threadedly sealed and connected to the self-sealing piston cylinder 3, a plurality of upper fluid channels 205 are evenly distributed circumferentially in the upper half of the interior of the shell 201, and the plurality of upper fluid channels 205 are all connected to the inner cavity of the upper joint 1, a plurality of lower fluid channels 206 are evenly distributed circumferentially in the lower half of the interior of the shell 201, and the plurality of lower fluid channels 206 are all connected to the upper piston cavity 301 of the self-sealing piston cylinder 3, and a flow hole 207 is also opened in the middle position of the interior of the shell 201, and the flow hole 207 can realize the connection between the upper fluid channel 205 and the lower fluid channel 206; the upper fluid channel 205 is also connected to the inner cavity of the upper joint 1, and the lower fluid channel 206 is also connected to the upper piston cavity 302.

[0041] A first U-shaped groove 208 and a second U-shaped groove 209 are also provided inside the housing 201. The opening directions of the first U-shaped groove 208 and the second U-shaped groove 209 are arranged in opposite directions. The upper fluid channel 205 is arranged at the opening end of the first U-shaped groove 208, and the lower fluid channel 206 is arranged at the opening end of the second U-shaped groove 209. Specifically, a first U-shaped groove 208 with an upper end opening is also provided in the upper half of the housing 201. The hydraulic control piston 202 can be slidably installed in the first U-shaped groove 208 up and down, and the first U-shaped groove 208 is located below the lower port of the upper joint inner cavity. The fluid flowing out of the upper joint 1 can act on the upper end surface of the hydraulic control piston 202 and drive the hydraulic control piston 202 to move downward.

[0042] The upper end of the valve core 203 passes through the flow hole 207 and the first U-shaped groove 208 and is fixedly connected to the hydraulic control piston 202. The lower end of the valve core 203 is slidably arranged in the second U-shaped groove 209 inside the shell 201. A spring groove 210 is arranged at the bottom of the valve core. The elastic element 204 is placed in the spring groove 210 and is restricted between the top surface of the spring groove 210 and the bottom surface of the second U-shaped groove 209. Driven by the elastic element 204, the valve core 203 moves up and blocks the flow hole 207.

[0043] Specifically, the valve core 203 includes a connecting rod 2031 and a sealing portion 2032 connected in sequence from top to bottom. The upper end of the connecting rod 2031 passes through the flow hole 207 and the piston groove 208 and is fixedly connected to the hydraulic control piston 202. The lower end of the connecting rod 2031 is fixedly connected to the upper end of the sealing portion 2032 and the two can be made in one piece. A second U-shaped groove 209 with an upper end opening is also opened in the lower half of the interior of the outer shell 201. The lower part of the sealing portion 2032 can be slidably installed in the second U-shaped groove 209 up and down. The bottom of the sealing portion 2032 is also recessed upward to form a spring groove 210. The elastic element 204 is placed in the spring groove 210 and is confined between the top surface of the spring groove 210 and the bottom surface of the second U-shaped groove 209. Driven by the elastic element 204, the blocking portion 2032 of the valve core 203 moves upward and blocks the flow hole 207 to cut off the connection between the upper fluid channel 205 and the lower fluid channel 206, thereby preventing the fluid moving from bottom to top from passing through; when the hydraulic control piston 202 is thrusted by the fluid moving from top to bottom, the hydraulic control piston 202 moves downward and drives the valve core 203 to overcome the force of the elastic element 204 and move downward together. At this time, the flow hole 207 is opened, and the connection between the upper fluid channel 205 and the lower fluid channel 206 can be achieved, so that the fluid moving from top to bottom can pass through and enter the interior of the self-sealing piston cylinder 3.

[0044] Furthermore, the flow hole 207 is a stepped hole, which includes a first hole segment and a second hole segment, wherein the first hole segment is arranged above the second hole segment, and the inner diameter of the first hole segment is smaller than the second hole diameter. The upper end of the blocking portion 2032 is provided with a blocking surface that can match the inner diameter of the flow hole 207, and the blocking surface is inclined, that is, the blocking surface is a conical surface, and its upper end cross section is smaller than the lower end cross section.

[0045] The self-sealing piston 4 is slidably installed in the inner cavity of the self-sealing piston cylinder 3, and the self-sealing piston 4 also divides the inner cavity of the self-sealing piston cylinder 3 into an upper piston cavity 301 and a lower piston cavity 302, and the upper piston cavity 301 is evacuated.

[0046] Further, the first tubular structure 501 is integrally formed with the hollow guide cone 6. The first tubular structure 501 is detachably connected to the self-sealing piston 4. The first tubular structure 501 is detachably connected to the self-sealing piston 4, and preferably, the two are threadedly connected.

[0047] The upper and lower ends of the rubber cylinder 505 are respectively provided with shoulder guard rings, referring to the accompanying drawings, which are an upper shoulder guard ring 509 and a lower shoulder guard ring 510 respectively.

[0048] The self-sealing bridge plug 5 includes a center tube 501 and a sealing assembly. The upper end of the center tube 501 is closed and extends into the lower piston cavity 302 to be coaxially fixed with the self-sealing piston 4. Specifically, the center tube 501 and the self-sealing piston 4 are detachably threaded and sealed together; a connecting hole 5011 is also opened on the side wall of the center tube 501, and the connecting hole 5011 is used to achieve the connection between the inner cavity of the center tube 501 and the lower piston cavity 302. There are multiple connecting holes 5011 and they are evenly distributed in the circumferential direction; the lower end of the center tube 501 is coaxially fixed with a hollow guide cone 6 and the inner cavities of the two are connected. The center tube 501 and the hollow guide cone 6 are made of one piece. The fluid in the wellbore enters the inner cavity of the hollow guide cone 6 from the bottom to the top and can enter the lower piston cavity 302 through the connecting hole 5011, thereby pushing the self-sealing piston 4 to move up and driving the center tube 501 and the hollow guide cone 6 to move up together. The sealing assembly is sleeved on the center tube 501 and limited between the self-sealing piston cylinder 3 and the hollow guide cone 6. When the self-sealing piston 4 moves upward, the center tube 501 can drive the hollow guide cone 6 to squeeze and compress the sealing assembly; specifically, the sealing assembly includes a cava seat 502, an upper cava 503, a second tubular structure 504, a rubber cylinder 505, a third tubular structure 506 and a lower cava 507 arranged in sequence from top to bottom, wherein the upper and lower ends of the rubber cylinder 505 are also respectively provided with a shoulder guard and the two shoulder guards are an upper shoulder guard 509 and a lower shoulder guard 510, the second tubular structure 504 and the third tubular structure 506 are connected by a pin 508, and the rubber cylinder 505 is limited between the second tubular structure 504 and the third tubular structure 506. After the pin 508 is sheared, the second tubular structure 504 and the third tubular structure 506 can slide up and down relatively and can squeeze and compress the rubber cylinder 505 to achieve sealing.

[0049] The second tubular structure 504 includes an upper cone, and the third tubular structure 506 includes a lower cone. The inner diameter of the bottom end of the upper cone matches the outer diameter of the top end of the lower cone, and the top of the lower cone is connected to the upper cone by a pin. Specifically, the pin 508 is arranged to penetrate the upper cone horizontally, and partially penetrates the lower cone. The upper cone and the lower cone are arranged oppositely, that is, the outer diameter of the bottom end of the upper cone is greater than the outer diameter of the top end of the upper cone, and the outer diameter of the bottom end of the lower cone is smaller than the outer diameter of the top end of the lower cone. In addition, the upper slip 503 is sleeved on the outside of the upper cone, and the bottom end of the lower cone is sleeved in the lower slip 507 and is smaller than the bottom end of the hollow guide cone, and the outer diameter of the top end of the lower cone is greater than the outer diameter of the rubber cylinder 505, so that the hollow guide cone 6 moves upward to make the lower slip 507 expand radially, and the third tubular structure 506 compresses the rubber cylinder 505 upward under the drive of the hollow guide cone 6, and the rubber cylinder 505 then drives the upper cone to make the upper slip 503 expand radially.

[0050] Embodiment 1:

[0051] In a 4000m deep well with a wellhead pressure of 20MPa, the casing self-sealing plug of the present invention is released from the wellhead and falls freely into the wellbore at a position of 200m. The formation pressure overcomes the hydrostatic column pressure in the wellbore, so that the casing self-sealing plug withstands a lower pressure difference of 22MPa and an upper pressure difference of 2MPa.

[0052] The pressure fluid of the lower pressure difference of 22MPa in the wellbore can flow into the inner cavity of the center pipe 501 through the inner cavity of the hollow guide cone 6 in turn, and enter into the lower piston cavity 302 through the connecting hole 5011, act on the lower end of the self-sealing piston 4 and push the self-sealing piston 4 to move upward, thereby driving the center pipe 501 and the hollow guide cone 6 to move upward, and the hollow guide cone 6 squeezes the lower slip 507 to move along the inclined surface of the third tubular structure 506, and after opening the lower slip 507, it abuts against the inner wall of the casing, and continues to squeeze the lower slip 507 and the third tubular structure 506 to move upward, and after shearing the pin 508, squeezes and compresses the rubber cylinder 505, and continues to move upward under the action of fluid pressure, and the second tubular structure 504 squeezes and opens the upper slip 503, so that the upper slip 503 and the lower slip 507 finally bite the inner wall of the casing, and at the same time the rubber cylinder 505 completes the sealing, which can realize the automatic sealing of the casing self-sealing plug under the action of the well pressure.

[0053] On the one hand, after the rubber cylinder 505 is sealed, the wellbore pressure below the rubber cylinder 505 is continuously held up by the formation pressure, and the pressure will become higher and higher, and will continuously act on the self-sealing piston 4, so that the self-sealing piston 4 will always keep moving upward, which actually plays a sealing role for the self-sealing plug for casing; on the other hand, the hydraulically controlled one-way valve 2 will not be opened without external high-pressure fluid pressure on the upper end of the self-sealing plug for casing, and the upper pressure difference of 2MPa that the self-sealing plug for casing is borne by is not enough to push the self-sealing piston 4 in the self-sealing piston cylinder 3 to move downward and unseal the rubber cylinder, which can eventually keep the self-sealing plug for casing in the wellbore in a long-term sealed state.

[0054] When it is necessary to unseal and salvage the casing using the self-sealing plug of the present application, lower the continuous oil tubing bottom with a fishing spear down to the position where the self-sealing plug of the casing in the wellbore encounters resistance, pressurize 0.5T to explore the self-sealing plug of the casing, pressurize 1.5T to lift and salvage the upper joint 1 of the self-sealing plug of the casing, and then pressurize 25MPa into the wellbore to make the self-sealing plug of the casing overcome the downward pressure difference of 22MPa, and then the self-sealing piston 4 moves downward and drives the center pipe 501 and the hollow guide cone 6 to move downward, so that the rubber cylinder 505, the upper slip 503 and the lower slip 507 are not squeezed, restored to their original state, and the unsealing is completed. After that, the continuous oil tubing can be lifted to salvage the self-sealing plug of the casing.

[0055] The technical solutions in the above embodiments of the present application have at least the following technical effects and advantages:

[0056] The self-sealing plug for casing of the present invention utilizes the high-pressure fluid pressure in the wellbore to flow into the first tubular structure through the hollow guide cone, and then acts on the self-sealing piston through the through hole, pushing the self-sealing piston upward and driving the first tubular structure and the hollow guide cone to move upward together, so that the second tubular structure and the third tubular structure squeeze the rubber cylinder to achieve automatic sealing under the action of the pressure fluid in the well. The present invention has a reasonable structure, is safe and reliable, is easy to operate, and has a low cost. It can save precious time for replacing the main gate of the wellhead and solve the wellhead safety problem in a timely manner.

[0057] It should be noted that in the description of the present invention, the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings, which are only for the convenience of description, and do not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0058] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0059] The term "comprise" or any other similar term is intended to cover a non-exclusive inclusion, such that a process, article, or apparatus / device that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, article, or apparatus / device.

[0060] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A self-sealing plug for casing, characterized in that: It includes an upper joint, a hydraulically controlled one-way valve, a self-sealing piston cylinder, a self-sealing bridge plug and a hollow guide cone which are connected in sequence; The hydraulically controlled one-way valve only allows the fluid to flow in a one-way manner from top to bottom; A self-sealing piston with a closed upper end is movably arranged in the self-sealing piston cylinder, and the self-sealing piston divides the inner cavity of the self-sealing piston cylinder into an upper piston cavity and a lower piston cavity; The self-sealing bridge plug comprises a first tubular structure and a setting assembly sleeved on the first tubular structure; the upper end of the first tubular structure is coaxially connected to the lower end of the self-sealing piston, and the side wall of the first tubular structure is provided with a through hole to connect the inner cavity of the first tubular structure with the lower piston cavity; The lower end of the first tubular structure is fixed to the hollow guide cone and the inner cavity is connected, and the setting assembly is limited between the self-sealing piston cylinder and the hollow guide cone; When the self-sealing piston moves upward, the first tubular structure can drive the hollow guide cone to squeeze and compress the setting assembly, so that the setting assembly expands radially; The hydraulically controlled one-way valve comprises a shell, a hydraulically controlled piston, a valve core and an elastic element. An upper fluid channel and a lower fluid channel are formed inside the shell. The upper fluid channel and the lower fluid channel are connected through a flow hole. The upper fluid channel is also connected to the inner cavity of the upper joint, and the lower fluid channel is also connected to the upper piston cavity. The hydraulically controlled piston can be slidably installed in a first U-shaped groove inside the shell, and the first U-shaped groove is located below the lower port of the inner cavity of the upper joint. The upper end of the valve core passes through the flow hole and the first U-shaped groove and is fixedly connected to the hydraulically controlled piston. The lower end of the valve core can be slidably arranged in a second U-shaped groove inside the shell. A spring groove is arranged at the bottom of the valve core. The elastic element is placed in the spring groove and is restricted between the top surface of the spring groove and the bottom surface of the second U-shaped groove. Driven by the elastic element, the valve core moves up and blocks the flow hole.

2. The self-sealing plug for cannula according to claim 1, characterized in that: The sealing assembly includes a cava seat, an upper cava, a second tubular structure, a rubber cylinder, a third tubular structure and a lower cava, which are arranged in sequence from top to bottom. The second tubular structure and the third tubular structure are connected by a pin, and the rubber cylinder is limited between the second tubular structure and the third tubular structure. After the pin is sheared, the second tubular structure and the third tubular structure can move toward each other to squeeze and compress the rubber cylinder.

3. The self-sealing plug for cannula according to claim 1, characterized in that: The flow hole includes a first hole segment and a second hole segment, the first hole segment is arranged above the second hole segment, and the inner diameter of the first hole segment is smaller than the inner diameter of the second hole segment.

4. The self-sealing plug for cannula according to claim 3, characterized in that: The valve core comprises a connecting rod and a blocking portion which are sequentially connected from top to bottom. The upper end of the blocking portion is provided with a blocking surface which can match the inner diameter of the flow hole, and the blocking surface is arranged obliquely.

5. The self-sealing plug for cannula according to claim 3, characterized in that: The opening directions of the first U-shaped groove and the second U-shaped groove are arranged in opposite directions, the upper fluid channel is arranged at the opening end of the first U-shaped groove, and the lower fluid channel is arranged at the opening end of the second U-shaped groove.

6. The self-sealing plug for cannula according to claim 1, characterized in that: The first tubular structure and the hollow guide cone are integrally formed.

7. The self-sealing plug for cannula according to claim 1, characterized in that: The first tubular structure is detachably connected to the self-sealing piston.

8. The self-sealing plug for cannula according to claim 1, characterized in that: There are multiple through holes on the side wall of the first tubular structure, and the multiple through holes are evenly arranged along the circumference of the first tubular structure.

9. The self-sealing plug for cannula according to claim 2, characterized in that: The upper and lower ends of the rubber cylinder are respectively provided with shoulder protection rings.

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