Balanced anchor shoe packer

Abstract

The balanced anchor packer has a balanced piston positioned between the outer wall of the central tube and the inner wall of the valve body. The upper end face of the balanced piston has a larger area than the lower end face, and both ends are connected to the lower hydraulic pressure. When the balanced piston completes the connection to the lower hydraulic pressure and moves downward, its lower end face abuts against the annular step on the outer wall of the central tube. This invention sets the upper and lower end faces of the balanced piston to different areas, and then utilizes the Pascal's principle of liquid to create different pressures at the upper and lower ends, pushing the balanced piston downward to abut against the central tube, preventing it from prematurely lifting and releasing the seal due to downward pressure.

Description

Technical Field

[0001] This invention relates to a downhole tool for oil and gas field development, specifically a balanced anchor packer that can prevent the center tube from surging upwards. Background Technology

[0002] During downhole operations in oil and gas field development, packers seal off the annular space between tubing of various sizes and the wellbore, as well as between tubing strings, to isolate the producing formation and protect the casing.

[0003] There are two types of anchor-type packers. One type has a fixed structure between the packer's central tube and the hydraulic anchor, preventing relative movement. This type of packer requires the annulus to apply equal pressure to retract the anchor claws into the anchor body during release. If a void exists in the upper part of the packer, pressure cannot be established in the annulus when release is needed, potentially leading to a packer that cannot be released. The other type has a non-fixed structure between the packer's central tube and the hydraulic anchor, allowing relative movement. This type of packer does not have release difficulties. However, for upward-release packers, when the pressure at the bottom of the packer is much higher than the pressure at the top, the central tube generates an upward force under hydraulic pressure. When this upward force exceeds the set release load, the packer will prematurely release and fail, affecting normal production and potentially causing major accidents or losses. Summary of the Invention

[0004] This invention aims to provide a balanced anchor pad packer to solve the problems existing in current anchor pad packers. To achieve the above objective, the technical solution adopted by this invention includes an anchor body with an anchor claw assembly on its outer wall; a central tube passing through the anchor body, which, when descending, can achieve setting by reversing the opening and expansion of the slips and rubber sleeve sealing assembly; and an axially sliding balance piston located between the outer wall of the central tube and the inner wall of the hydraulic cylinder; the upper end face of the balance piston has a larger area than its lower end face, and both its upper and lower end faces are connected to the lower hydraulic pressure; after the packer sets, under the action of the lower hydraulic pressure, the lower end face of the balance piston presses against the annular step on the outer wall of the central tube, preventing it from moving upwards.

[0005] The downhole hydraulic pressure refers to the downhole hydraulic pressure transmitted from the lower end of the self-sealing packer to the upper and lower end faces of the balance piston via liquid (through the annulus).

[0006] The steps are circular.

[0007] The central tube has an annular space between its outer wall and the inner wall of the anchor body. The lower hydraulic pressure passes through the annular space to connect the lower end face, inner wall, and upper end face of the balance piston in sequence.

[0008] It also includes a liquid cylinder, the lower end of which is connected to the upper end of the anchor body. The balance piston can slide axially within the liquid cylinder. The inner wall of the liquid cylinder and the outer wall of the balance piston are sealed. The upper end face, inner wall, and lower end face of the balance piston, together with the outer wall of the central tube, form a liquid space with an upper opening and a lower connection annular space.

[0009] The outer walls of the upper and lower ends of the balance piston are sealed to the inner wall of the hydraulic cylinder by sealing rings.

[0010] The upper end of the balance piston is provided with a convex ring, and the area of ​​the upper end surface of the convex ring is larger than that of the lower end surface of the balance piston.

[0011] The outer wall of the convex ring is equipped with a sealing ring.

[0012] The upper end of the central tube is provided with an upper connector, and the lower end of the upper connector and the upper end of the liquid cylinder are respectively provided with corresponding embedded sealing structures; when the upper connector moves downward with the central tube, the embedded sealing structures fit together and seal the upper end of the liquid space.

[0013] The upper connector is provided with a washer ring, and the lower end of the washer ring is provided with an annular female buckle; the upper end of the hydraulic cylinder is provided with a corresponding annular male buckle.

[0014] The washer ring is fixed to the outer wall of the upper connector by a retaining ring.

[0015] It also includes a connecting sleeve, the upper end of which is fixed to the inner wall of the anchor body, and the lower end extends radially inward and is fastened into the annular groove on the outer wall of the central tube; under low pressure, it can ensure that the central tube will not move downward.

[0016] The outer wall of the central tube is also equipped with a reversing sleeve, and the outer wall of the reversing sleeve is connected to the friction block through a leaf spring.

[0017] The lower end of the central tube is connected to a lower connector, which is equipped with a straightening ring.

[0018] Compared with existing technologies, this invention sets the upper and lower end faces of the balance piston to have different areas. Then, utilizing the Pascal's principle, the different pressures at the upper and lower ends push the balance piston downwards to press down on the central tube, preventing it from moving upwards due to downward pressure and thus causing unsealing. The annular step of the central tube is used to withstand the downward pressure of the balance piston. The annular space is used to transmit the downhole pressure at the lower part of the packer and, during unsealing, serves as a fluid channel to allow fluid from the lower part of the packer to flow to the upper part, thereby balancing the pressure difference and allowing the central tube to be lifted. The convex ring increases the area of ​​the upper end face of the balance piston, and the balance piston and the hydraulic cylinder are sealed to reduce interference from external pressure. The sealing structure can close the connection between the upper end of the liquid space and the outside when the central tube moves downwards, acting as a seal to prevent liquid from the lower part of the packer from flowing to the upper part and causing packer failure. The connecting sleeve prevents the central tube from moving downwards arbitrarily. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a structure according to an embodiment of the present invention;

[0020] Figure 2 for Figure 1 A magnified view of a portion of the image;

[0021] Referring to the attached diagram, the components are: upper connector 1, O-ring seal 2, fastening screw 3, fixing ring 4, washer ring 5, center tube 6, balance piston 8, hydraulic cylinder 9, upper gauge ring 11, anchor body 12, anchor claw 13, spring 15, pressure plate 16, screw 17, lower gauge ring 19, end rubber sleeve 20, spacer ring 21, middle rubber sleeve 22, outer tube 23, rubber sleeve liner 24, connecting sleeve 25, lower cone 26, release cone 27, slip 28, slip spring 29, reversing sleeve 30, friction block 31, leaf spring 32, pressure plate 33, guide pin 34, straightening ring 36, and lower connector 37. Detailed Implementation

[0022] The present invention will now be further described with reference to the accompanying drawings.

[0023] See Figures 1 to 2 , Figure 1 , Figure 2 The illustration shows an embodiment of the present invention, including an anchor body and a sealing assembly. The outer wall of the anchor body is provided with an anchor claw assembly, and the lower end of the anchor body is connected to an outer tube. A rubber sleeve sealing assembly is provided on the outer wall of the outer tube. The anchor claw assembly consists of an upper gauge ring, an anchor body, anchor claws, a spring, a pressure plate, and screws. The rubber sleeve sealing assembly consists of a lower gauge ring, an end rubber sleeve, a spacer ring, a middle rubber sleeve, an outer tube, a rubber sleeve liner, a connecting sleeve, and a lower cone. A release cone, slips, and slip springs are also provided. When the central tube descends, the anchor claw assembly and the rubber sleeve sealing assembly can be opened and expanded respectively by reversing the direction of movement to achieve sealing.

[0024] The central tube passes through the anchor body, and a balance piston that can slide axially is provided between the outer wall of the central tube and the inner wall of the hydraulic cylinder.

[0025] In this embodiment, the balance piston preferably has a convex ring on its upper outer wall. The area of ​​the upper end face of the convex ring is larger than that of the lower end face of the balance piston, thus the area of ​​the upper end face is larger than that of the lower end face. When the upper and lower end faces are respectively connected to the downward hydraulic pressure, that is, under the same hydraulic pressure, the pressure of the liquid pushing the balance piston at both ends is greater at the top and less at the bottom, causing the balance piston to move downward or have a downward tendency. The lower end face of the balance piston will press against the annular step on the outer wall of the central tube, and the annular step of the central tube is used to withstand the downward pressure of the balance piston.

[0026] Preferably, the step is annular; the annular shape can ensure accurate positioning of the balance piston and also improve the strength of the central tube.

[0027] In this embodiment, an annular space is provided between the outer wall of the central tube and the inner wall of the anchor body; the annular space can transmit the downhole hydraulic pressure. The downhole hydraulic pressure is transmitted upward from the lower part (i.e., downhole) of this embodiment through the annular space, and then flows and is transmitted to the upper and lower end faces of the balance piston; since the downhole hydraulic pressure is transmitted from downhole, its pressure is usually greater than the pressure at the upper part of this embodiment.

[0028] See Figure 2 When the anchor claw assembly and the rubber sleeve sealing assembly of this embodiment are set due to the downward movement of the central tube, the lower hydraulic pressure flows from the well into the annular space and sequentially connects to the lower end face, inner wall, and upper end face of the balance piston. Since the upper and lower end faces of the balance piston have different areas, based on the liquid Pascal principle, the greater pressure on the upper end face pushes the balance piston downward and presses against the central tube (applying force to the upper end of the annular step), preventing it from being prematurely lifted and unsealed only due to the pressure from below, thus ensuring that this embodiment can be used normally.

[0029] When the packer needs to be truly unsealed, simply lift the tube string. Overcoming only a small amount of balancing pressure will connect the upper and lower channels of the packer, balance the pressure, and cause the anchor claw assembly and rubber sleeve sealing assembly to contract on their own. The pressure on the lower end face, inner wall, and upper end face of the annulus and balancing piston will be the same as the pressure outside the anchor body (balanced), allowing the central tube to continue to be lifted.

[0030] Preferably, the system also includes a hydraulic cylinder for transmitting downward hydraulic pressure and allowing the balance piston to slide axially. The lower end of the hydraulic cylinder is connected to the upper end of the anchor body, and the inner wall of the hydraulic cylinder is sealed to the outer wall of the balance piston. The upper end face, inner wall, and lower end face of the balance piston, together with the outer wall of the central tube, form a liquid space with an upper opening and a lower connection annular space, which is used to drive the balance piston downward.

[0031] Preferably, the outer walls of the upper and lower ends of the balance piston are sealed to the inner wall of the hydraulic cylinder by O-rings.

[0032] The outer wall of the convex ring and the lower outer wall of the balance piston are respectively provided with annular grooves to accommodate O-ring seals. The purpose of this sealing is to reduce interference from external pressure.

[0033] Further, see Figure 1 and Figure 2 The upper end of the central tube is provided with an upper connector, and the lower end of the upper connector and the upper end of the liquid cylinder are respectively provided with corresponding surface sealing structures; when the upper connector moves down with the central tube, the surface sealing structures are engaged and seal the upper end of the liquid space.

[0034] Preferably, the upper connector is provided with a gasket, which is preferably fixed to the outer wall of the upper connector by a retaining ring. The lower end of the gasket is provided with an annular female buckle; the upper end of the liquid cylinder is provided with a corresponding annular male buckle. When they are engaged, they form a surface seal, which can close the connection between the upper end of the liquid space and the outside world when the central tube moves down, preventing the liquid from flowing out and causing an imbalance of internal and external pressure.

[0035] In addition, a reversing sleeve is provided on the outer wall of the central tube. The outer wall of the reversing sleeve is connected to a friction block via a leaf spring. A fixing plate is provided on the outer side of the friction block. A guide pin is provided at the lower end of the reversing sleeve. The lower end of the central tube is connected to a lower connector, which is equipped with a straightening ring. These are used for changing direction and correcting posture, respectively.

[0036] This system also includes a connecting sleeve. The upper end of the connecting sleeve is fixed to the inner wall of the cone, and its lower end extends radially inward and snaps into the annular groove on the outer wall of the central tube. The lower end of the connecting sleeve and the annular groove form a snap-fit ​​structure, ensuring that the central tube and the friction block do not experience axial relative movement before the central tube and the reversing sleeve reverse direction. After the central tube and the reversing sleeve reverse direction, the lower end of the connecting sleeve is radially outward by the release cone, releasing the axial relative movement restriction between the central tube and the friction block, thus achieving a set seal.

[0037] In this embodiment, the upper and lower end faces of the balance piston are set to have different areas. Then, the Pascal principle of liquid is used to make the upper and lower ends have different pressures, which push the balance piston downward to block the central tube, preventing it from being lifted prematurely due to the pressure below and thus releasing the seal. The annular step of the central tube is used to bear the resistance of the balance piston. The annular space is used to transmit the downhole pressure at the lower end of the packer, and to transmit the pressure of the external oil casing during unsealing to push open the balance piston and allow the central tube to be lifted. The convex ring increases the area of ​​the upper end face of the balance piston, and the balance piston and the hydraulic cylinder are set to be sealed to reduce the interference of the external pressure. The embedded sealing structure can close the connection between the upper end of the liquid space and the outside when the central tube moves downward, which plays a sealing role and prevents the liquid in the lower part of the packer from flowing to the upper part, causing the packer to fail. The connecting sleeve can prevent the central tube from moving downward at will.

[0038] The embodiments of the present invention have been described above with reference to the accompanying drawings and examples. The structures given in the embodiments do not constitute a limitation of the present invention. Those skilled in the art can make adjustments as needed, and various modifications or variations within the scope of the appended claims are all within the scope of protection.

Claims

1. A balanced anchor pad packer, comprising an anchor body, an anchor claw assembly provided on the outer wall of the anchor body; a central tube passing through the anchor body, wherein the central tube, when descending, drives the anchor claw assembly and the rubber sleeve sealing assembly to open and expand respectively to achieve setting and sealing, characterized in that: It also includes an axially sliding balance piston, which is located between the outer wall of the central tube and the inner wall of the hydraulic cylinder; an annular space is provided between the outer wall of the central tube and the inner wall of the anchor body, and the lower hydraulic pressure passes through the annular space to sequentially connect the lower end face, the inner wall and the upper end face of the balance piston; It also includes a liquid cylinder, in which the balance piston can slide axially; the inner wall of the liquid cylinder and the outer wall of the balance piston are sealed, and the upper end face, inner wall, and lower end face of the balance piston and the outer wall of the central tube form a liquid space with an upper opening and a lower connection annular space. The upper end of the central tube is provided with an upper connector, and the lower end of the upper connector and the upper end of the liquid cylinder are respectively provided with corresponding embedded sealing structures; when the upper connector moves downward with the central tube, the embedded sealing structures engage and seal the upper end of the liquid space. The area of ​​the upper end face of the balance piston is larger than that of the lower end face, and the upper and lower end faces are respectively connected to the lower hydraulic pressure; when the balance piston moves downward, its lower end face presses against the step on the outer wall of the central tube.

2. The balanced anchor tile packer according to claim 1, characterized in that: The outer walls of the upper and lower ends of the balance piston are sealed to the inner wall of the hydraulic cylinder by sealing rings.

3. The balanced anchor tile packer according to claim 1, characterized in that: The upper end of the balance piston is provided with a convex ring, and the area of ​​the upper end surface of the convex ring is larger than that of the lower end surface of the balance piston.

4. The balanced anchor tile packer according to claim 1, characterized in that: The upper connector is provided with a washer, and the lower end of the washer is provided with an annular female thread; the upper end of the hydraulic cylinder is provided with a corresponding annular male thread.

5. The balanced anchor tile packer according to claim 1, characterized in that: It also includes a connecting sleeve, the upper end of which is fixed to the inner wall of the cone, and the lower end of which extends radially inward and is snapped into the annular groove on the outer wall of the central tube.

6. The balanced anchor tile packer according to claim 1, characterized in that: The outer wall of the central tube is also equipped with a reversing sleeve, and the outer wall of the reversing sleeve is connected to the friction block through a leaf spring.

7. The balanced anchor tile packer according to claim 1, characterized in that: The lower end of the central tube is connected to a lower connector, which is equipped with a straightening ring.

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