Cannula Sealer and its Installation Method

Abstract

This invention belongs to the field of well completion tool technology, and particularly relates to a pipe sealing device and its installation method. The pipe sealing device of this invention includes: a sealing cylinder and a pipe assembly. The pipe assembly includes: a central cylinder, a force transmission cylinder, a limiting cylinder, and a cylindrical sealing element. The limiting cylinder is disposed on the outer wall of the central cylinder, and its upper end can abut against the upper end of the sealing cylinder. The force transmission cylinder and the sealing element are sequentially disposed on the outer wall of the limiting cylinder from top to bottom. When the upper end of the limiting cylinder abuts against the upper end of the sealing cylinder, there is a radial gap between the outer wall of the limiting cylinder and the outer wall of the sealing cylinder. When the central cylinder moves downward relative to the limiting cylinder and the sealing cylinder, the force transmission cylinder can compress the upper end face of the sealing element downward, thereby causing the sealing element to expand radially and seal against the inner wall of the sealing cylinder. In this invention, there is a large gap between the sealing cylinder and the pipe assembly, and the sealing is achieved through the radial expansion of the sealing element, improving the adaptability and sealing reliability of the pipe sealing device.

Description

Technical Field

[0001] This invention belongs to the field of well completion tool technology, and particularly relates to a pipe sealing device and its installation method. Background Technology

[0002] The tubing sealer is a commonly used completion tool in oil and gas wells, offering advantages such as the ability to replace the upper tubing string. For example... Figure 1 As shown, the existing insertion sealing device mainly consists of two parts: an insertion tube 13 and a sealing cylinder 1. The sealing cylinder 1 is usually placed downhole beforehand, and then the insertion tube 13 is inserted into its inner cavity. Multiple sealing components are provided on the outer wall of the insertion tube 13, usually O-rings 8. The insertion tube 13 forms a seal with the inner wall of the sealing cylinder 1 by relying on the interference fit of the sealing components themselves. However, this sealing method requires a small gap between the insertion tube 13 and the sealing cylinder 1. Usually, the radial gap between the two cannot exceed 0.15 mm. However, the sealing cylinder 1 is pre-placed thousands of meters deep downhole, and the insertion tube 1 is lowered into the well from the surface. If the gap between the two is too small, the insertion tube 13 may not be able to be inserted into the sealing cylinder 1. Meanwhile, in this sealing method, the sealing surfaces of the sealing cylinder 1 and the insertion tube 13 are required to be smooth to ensure sealing performance. However, the sealing surface of the sealing cylinder 1 is easily rough and uneven due to collisions, corrosion, and scaling when tools pass through it in the well. The elasticity of the sealing component itself cannot fill the unevenness on the sealing surface well, which will result in poor sealing performance or failure to achieve sealing between the sealing cylinder 1 and the insertion tube 13. Summary of the Invention

[0003] This invention provides a cannula sealer and its installation method, which solves the technical problems in the prior art where the small gap between the cannula and the sealing cylinder leads to difficulties in cannula installation and poor sealing reliability between the two.

[0004] A first aspect of the present invention provides a cannula sealer, comprising: a sealing cylinder pre-placed downhole and a cannula assembly that seals with the sealing cylinder.

[0005] The cannulation assembly includes: a central cylinder, a force transmission cylinder, a limiting cylinder, and a cylindrical sealing element.

[0006] The limiting cylinder is disposed on the outer wall of the central cylinder, and the inner wall of the limiting cylinder is slidably sealed to the outer wall of the central cylinder. The upper end of the limiting cylinder can abut against the upper end of the sealing cylinder.

[0007] The force transmission cylinder and the sealing element are sequentially arranged on the outer wall of the limiting cylinder from top to bottom. The upper end of the force transmission cylinder is fixedly connected to the outer wall of the central cylinder, and the lower end face of the sealing element is fixed relative to the limiting cylinder.

[0008] When the upper end of the limiting cylinder abuts against the upper end of the sealing cylinder, there is a radial gap between the outer wall of the limiting cylinder and the outer wall of the sealing cylinder.

[0009] Furthermore, when the central cylinder moves downward relative to the limiting cylinder and the sealing cylinder, the force transmission cylinder can compress the upper end face of the seal downward, thereby causing the seal to expand radially and seal against the inner wall of the sealing cylinder. In one embodiment, the force transmission cylinder is fixedly connected to the outer wall of the central cylinder via an elastic cylinder.

[0010] The elastic cylinder is disposed on the outer wall of the central cylinder, and the upper end of the elastic cylinder is threadedly connected to the outer wall of the central cylinder.

[0011] The lower part of the elastic cylinder is provided with an elastic claw, and the inner wall of the upper part of the limiting cylinder is provided with a sliding groove for cooperating with the elastic claw. The elastic claw is slidably connected in the sliding groove, and the force transmission cylinder is connected to the outer wall of the elastic claw.

[0012] In one embodiment, the elastic claw has a locking portion on its wall, the locking portion protruding radially outward from the outer side of the sliding groove.

[0013] The force transmission cylinder is provided with a snap-fit ​​hole that mates with the snap-fit ​​part.

[0014] The force transmission cylinder and the elastic claw are detachably connected to the locking part through the locking hole.

[0015] In one embodiment, a locking component is also included.

[0016] The locking assembly is disposed between the force transmission cylinder and the seal to limit the position of the upper end face of the compressed seal.

[0017] In one embodiment, the locking assembly includes: a locking slip and a locking retaining ring.

[0018] The locking slip and the locking retaining ring are arranged sequentially from top to bottom on the outer wall of the limiting cylinder.

[0019] The lower end of the locking collet is provided with a first inclined surface, and the upper end of the locking retaining ring is provided with a second inclined surface that cooperates with the first inclined surface;

[0020] When the first inclined surface abuts against the second inclined surface, the locking retaining ring presses the locking slip inward, so that the inner wall of the locking slip is pressed and fixed against the outer wall of the limiting cylinder, thereby limiting the position of the upper end face of the compressed seal by the lower end face of the locking retaining ring.

[0021] In one embodiment, the inner wall of the locking latch is provided with reverse teeth, the tips of which face upwards.

[0022] In one embodiment, the locking assembly further includes a locking slip.

[0023] The inner wall of the locking clip is provided with a guide groove that cooperates with the locking clip and extends in the vertical direction.

[0024] In one embodiment, a guide tube is provided at the lower end of the central cylinder.

[0025] The lower end of the guide cylinder tapers radially inward, and the upper end face of the guide cylinder abuts against the lower end face of the seal to define the position of the lower end face of the seal.

[0026] In one embodiment, the upper end of the limiting cylinder is provided with a limiting boss for abutting against the upper end of the sealing cylinder.

[0027] A second aspect of the present invention provides a method for installing the above-described cannula seal, comprising the following steps:

[0028] The sealing cylinder is pre-placed inside the well;

[0029] The upper end of the central cylinder of the insertion assembly is connected to the tubing string, and the tubing string drives the insertion assembly downward into the sealing cylinder;

[0030] When the upper end of the limiting cylinder abuts against the upper end of the sealing cylinder, the oil pipe column drives the central cylinder to move downward relative to the limiting cylinder by a preset distance, causing the force transmission cylinder to compress the upper end face of the sealing element downward, thereby causing the sealing element to expand radially and seal against the inner wall of the sealing cylinder.

[0031] Compared with the prior art, the advantages of the present invention are as follows:

[0032] In this invention, when the insertion tube assembly is inserted into the sealing cylinder, there is a gap between the outer wall of the outermost limiting cylinder and the inner wall of the sealing cylinder. The oil pipe string drives the central cylinder to move downwards relative to the limiting cylinder, thereby compressing the sealing element in the force transmission cylinder. This causes the sealing element to expand radially and adhere tightly to the inner wall of the sealing cylinder, forming a seal. Compared to existing methods that rely on the interference fit of the sealing element to achieve a seal, the sealing cylinder and the insertion tube assembly in this invention have a larger gap. This avoids the technical problem of difficult insertion tube installation due to a small gap between the insertion tube and the sealing cylinder, improving the adaptability of the insertion tube seal. Simultaneously, the radial expansion of the sealing element after compression can densely fill the gap between the sealing cylinder and the insertion tube assembly, reducing the requirement for the smoothness of the inner wall of the sealing cylinder. Even if the inner wall of the sealing cylinder is rough or has scratches, a reliable seal between the two can still be guaranteed. Attached Figure Description

[0033] The invention will now be described in more detail with reference to embodiments and the accompanying drawings.

[0034] Figure 1 This is a schematic diagram of the structure of a cannula sealer in the prior art;

[0035] Figure 2 This is a schematic diagram of the cannula sealer in Embodiment 1 of the present invention. Figure 1 (The seal is in an uncompressed state);

[0036] Figure 3 This is a schematic diagram of the cannula sealer in Embodiment 1 of the present invention. Figure 2 (The seal is in a compressed state);

[0037] Figure 4 This is a schematic diagram of the cannula sealer in Embodiment 2 of the present invention. Figure 1 (The seal is in an uncompressed state);

[0038] Figure 5 This is a schematic diagram of the cannula sealer in Embodiment 2 of the present invention. Figure 2 (The seal is in a compressed state);

[0039] Figure 6 This is a schematic diagram of the structure of the central cylinder of the present invention;

[0040] Figure 7 This is a schematic diagram of the force transmission sleeve of the present invention;

[0041] Figure 8 This is a schematic diagram of the structure of the limiting cylinder of the present invention;

[0042] Figure 9 This is a schematic diagram of the structure of the elastic cylinder of the present invention;

[0043] Figure 10 This is a schematic diagram of the locking clip structure of the present invention;

[0044] Figure 11 yes Figure 10 Schematic diagram of section AA;

[0045] Figure 12 This is a schematic diagram of the locking retaining ring of the present invention;

[0046] Figure 13 This is a schematic diagram of the structure of the slip sleeve of the present invention;

[0047] Figure 14 This is a schematic diagram of the structure of the guide cylinder of the present invention.

[0048] Figure label:

[0049] 1. Sealing cylinder; 2. Limiting cylinder; 3. Force transmission cylinder;

[0050] 4. Center cylinder; 5. Sealing element; 6. Elastic cylinder;

[0051] 7. Guide cylinder; 8. Sealing ring; 9. Locking retaining ring;

[0052] 10. Locking slip; 11. Locking slip;

[0053] 21. Limiting boss; 22. Sliding groove; 23. Mounting groove;

[0054] 31. Snap-fit ​​hole; 41. Oil pipe thread;

[0055] 61. Flexible claw; 611. Snap-fit ​​part;

[0056] 101. Guide groove; 111. Reverse teeth;

[0057] 13. Intubation. Detailed Implementation

[0058] The invention will now be further described with reference to the accompanying drawings.

[0059] like Figure 2-14 As shown, a first aspect of the present invention provides a cannulation seal. The cannulation seal includes: a sealing cylinder 1 pre-placed downhole and a cannulation assembly that seals with the sealing cylinder 1. The cannulation assembly includes: a central cylinder 4, a force transmission cylinder 3, a limiting cylinder 2, and a cylindrical sealing element 5. The limiting cylinder 2 is disposed on the outer wall of the central cylinder 4, and the inner wall of the limiting cylinder 2 is slidably sealed to the outer wall of the central cylinder 4. The upper end of the limiting cylinder 2 can abut against the upper end of the sealing cylinder 1. The force transmission cylinder 3 and the sealing element 5 are disposed sequentially from top to bottom on the outer wall of the limiting cylinder 2. The lower end face of the sealing element 5 is fixed relative to the limiting cylinder 2. The upper end of the force transmission cylinder 3 is fixedly connected to the outer wall of the central cylinder 4, so that when the central cylinder 4 moves downward relative to the limiting cylinder 2 and the sealing cylinder 1, the force transmission cylinder 3 can compress the upper end face of the sealing element 5 downward, thereby causing the sealing element 5 to expand radially and seal against the inner wall of the sealing cylinder 1.

[0060] In this invention, when the cannula assembly is inserted into the sealing cylinder 1, there is a preset gap between the outer wall of the outermost limiting cylinder 2 and the inner wall of the sealing cylinder 1. The oil pipe column drives the central cylinder 4 to move downward relative to the limiting cylinder 2, thereby causing the force transmission cylinder 3 to compress the sealing element 5. The sealing element 5 expands radially and adheres tightly to the inner wall of the sealing cylinder 1 to form a seal. The sealing element 5 is made of rubber material.

[0061] Compared with the existing method of achieving sealing by the interference fit of the sealing element 5, the sealing cylinder 1 and the insertion tube assembly in this invention have a larger gap, thereby avoiding the technical problem of difficult insertion tube installation caused by the small gap between the insertion tube and the sealing cylinder 1.

[0062] Specifically, the radial gap between the outer wall of the cannulation assembly (i.e., the outer wall of the limiting cylinder 2) and the inner wall of the sealing cylinder 1 can be set to about 1 mm, for example, 0.5 mm to 1.5 mm.

[0063] At the same time, the seal 5 expands radially after being compressed, which can tightly fill the gap between the sealing cylinder 1 and the insertion tube assembly, reducing the requirements for the smoothness of the inner wall of the sealing cylinder. Even if the inner wall of the sealing cylinder 1 is rough or has scratches, it can still ensure a reliable seal between the two.

[0064] Example 1

[0065] like Figure 2-3 As shown in the diagram, in this embodiment, the force transmission cylinder 3 is fixedly connected to the outer wall of the central cylinder 4 via an elastic cylinder 6. The elastic cylinder 6 is disposed on the outer wall of the central cylinder 4, with its upper end threadedly connected to the outer wall of the central cylinder 4. The lower part of the elastic cylinder 6 is provided with an elastic claw 61, and the inner wall of the upper part of the limiting cylinder 2 is provided with a sliding groove 22 for engaging with the elastic claw 61. The elastic claw 61 is slidably connected in the sliding groove 22, and the force transmission cylinder 3 is connected to the outer wall of the elastic claw 61.

[0066] In this embodiment, the connection between the force transmission cylinder 3 and the central cylinder 4 is achieved through the elastic cylinder 6, and both the central cylinder 4 and the force transmission cylinder 3 can slide downward relative to the limiting cylinder 2.

[0067] Specifically, the elastic claw 61 is provided with a snap-fit ​​part 611 on its wall. The snap-fit ​​part 611 protrudes radially out of the outer side of the sliding groove 22. The force transmission cylinder 3 is provided with a snap-fit ​​hole 31 that cooperates with the snap-fit ​​part 611. The force transmission cylinder 3 and the elastic claw 61 are detachably connected to the snap-fit ​​part 611 through the snap-fit ​​hole 31.

[0068] More specifically, such as Figure 9 As shown, the lower part of the elastic cylinder 6 is provided with a plurality of elastic claws 61, which are evenly spaced along the circumference.

[0069] In this embodiment, the lower end face of the force transmission cylinder 3 is set as a plane, and its lower end face directly presses the sealing ring 8 to compress and expand it, thereby achieving a seal with the inner wall of the sealing cylinder 1.

[0070] like Figure 2 As shown, the upper end of the limiting cylinder 2 abuts against the upper end of the sealing cylinder 1. At this time, the force transmission cylinder 3 is located at the uppermost end of the limiting cylinder 2, and the sealing element 5 is in an uncompressed state. Therefore, the insertion tube assembly and the sealing cylinder 1 are not sealed. Figure 3 As shown, the central cylinder 4 drives the force transmission cylinder 3 to move downward relative to the limiting cylinder 2 through the elastic cylinder 6, thereby compressing the sealing element 5 along its axial direction (vertical direction) and expanding the sealing element 5 radially, thus tightly fitting it to the inner wall of the sealing cylinder 1 to form a seal.

[0071] It should be noted that, in this embodiment, after the cannula assembly and the sealing cylinder 1 are sealed by the radially expanding sealing element 5, the sealing element 5 is kept in a compressed state by the gravity of the tubing string.

[0072] Example 2

[0073] This embodiment describes the differences from the previous embodiments, while the similarities will not be repeated.

[0074] like Figure 4-5 As shown, the cannula sealer also includes a locking assembly disposed between the force transmission cylinder 3 and the seal 5 to limit the position of the upper end face of the compressed seal 5.

[0075] In other words, by setting a locking component in this embodiment to prevent the seal 5 from springing back, the sealing reliability of the cannula seal is further improved.

[0076] Specifically, the locking assembly includes a locking slip 11 and a locking retaining ring 9. The locking slip 11 and the locking retaining ring 9 are arranged sequentially from top to bottom on the outer wall of the limiting cylinder 2. The lower end of the locking slip 11 is provided with a first inclined surface, and the upper end of the locking retaining ring 9 is provided with a second inclined surface that cooperates with the first inclined surface.

[0077] When the first inclined surface abuts against the second inclined surface, the locking retaining ring 9 (radially) presses the locking slip 11 inward, so that the inner wall of the locking slip 11 is locked and fixed to the outer wall of the limiting cylinder 2, thereby limiting the position of the upper end face of the compressed sealing element 5 by the lower end face of the locking retaining ring 9.

[0078] Specifically, the number of locking slips 11 is set to multiple (at least two), and the multiple locking slips 11 are evenly spaced along the circumference of the limiting cylinder 2 to provide sufficient locking force to prevent the seal 5 from rebounding.

[0079] Preferably, the inner wall of the locking slip 11 is provided with reverse teeth 111, with the tips of the reverse teeth 111 facing upwards. Under the radial pressure provided by the locking retaining ring 9 via the inclined surface, the reverse teeth 111 on the inner wall of the locking slip 11 lock the outer wall of the limiting cylinder 2, thus allowing the locking slip 11 to move downwards relative to the limiting cylinder 2 but not upwards, thereby preventing the seal 5 from rebounding.

[0080] Preferably, the locking assembly further includes a locking sleeve 10, the inner wall of which is provided with a guide groove 101 that mates with the locking locking slip 11 and extends vertically. The locking sleeve 10 is used to limit the extension direction of the locking slip 11 and prevent it from tilting.

[0081] Preferably, the upper end face of the locking slip 11 is provided with a third inclined surface, and the lower end face of the force transmission cylinder 3 is provided with a fourth inclined surface that cooperates with the third inclined surface. This allows the force transmission cylinder 3 to also provide a certain radial pressure to the locking slip 11.

[0082] It should be noted that the angle between the fourth inclined plane and the horizontal direction should not be too large, so that the force transmission cylinder 3 can apply a sufficient downward force to the seal 5 so that the seal 5 is compressed.

[0083] Preferably, the first inclined plane makes an acute angle with the horizontal direction, and the second inclined plane is parallel to the first inclined plane. The third inclined plane makes an obtuse angle with the horizontal direction, and the fourth inclined plane is parallel to the third inclined plane.

[0084] like Figure 4 As shown, the upper end of the limiting cylinder 2 abuts against the upper end of the sealing cylinder 1. At this time, the force transmission cylinder 3 is located at the uppermost end of the limiting cylinder 2, and the sealing element 5 is in an uncompressed state. Therefore, the insertion tube assembly and the sealing cylinder 1 are not sealed. Figure 5 As shown, the central cylinder 4 drives the force transmission cylinder 3 and the locking assembly to move downward relative to the limiting cylinder 2 through the elastic cylinder 6, thereby compressing the sealing element 5 along its axial (vertical) direction and expanding the sealing element 5 radially, thus tightly fitting it to the inner wall of the sealing cylinder 1 to form a seal. At the same time, the locking slip 11 locks the outer wall of the limiting cylinder 2 under the radial pressure provided by the locking retaining ring 9 through the inclined surface, thereby effectively preventing the sealing element 5 from rebounding.

[0085] It should be noted that, in this embodiment, after the insertion tube assembly and the sealing cylinder 1 are sealed by the radially expanding sealing element 5, the sealing element 5 is kept in a compressed state by the gravity of the tubing string and the locking force between the locking slip 11 and the outer wall of the limiting cylinder 2.

[0086] Example 3

[0087] This embodiment describes the differences from the previous embodiments, while the similarities will not be repeated.

[0088] In the cannula sealer of this embodiment, a guide cylinder 7 is provided at the lower end of the central cylinder 4. The lower end of the guide cylinder 7 contracts radially inward, and the upper end face of the guide cylinder 7 abuts against the lower end face of the seal 5 to limit the position of the lower end face of the seal 5.

[0089] The guide cylinder 7, which tapers radially inward at its lower end, allows the insertion assembly to be smoothly inserted into the sealing cylinder 1.

[0090] Specifically, the lower end of the central cylinder 4 is provided with an external thread, the inner wall of the guide cylinder 7 is provided with an internal thread, and the guide cylinder 7 is threadedly connected to the lower end of the central cylinder 4.

[0091] In addition, the upper end of the central cylinder 4 is provided with an oil pipe buckle 41 to achieve connection with the oil pipe column.

[0092] The upper end of the limiting cylinder 2 is provided with a limiting boss 21 for abutting against the upper end of the sealing cylinder 1, so that the limiting cylinder 2 can stably abut against the sealing cylinder 1 to limit the sealing cylinder 1 in the vertical direction.

[0093] Preferably, the lower end face of the limiting boss 21 is provided with a first limiting inclined surface, and correspondingly, the inner wall of the upper end of the sealing cylinder 1 is provided with a second limiting inclined surface that cooperates with the first limiting inclined surface. This allows the sealing cylinder 1 to radially limit the position of the limiting cylinder 2.

[0094] Specifically, at least one mounting groove 23 for mounting the sealing ring 8 is provided on the inner wall of the lower part of the limiting cylinder 2, preferably two mounting grooves 23, to achieve a sliding sealing connection with the outer wall of the central cylinder 4. Further, the sealing ring 8 is an O-ring.

[0095] A second aspect of the present invention also provides a method for installing the above-described cannula seal, comprising the following steps:

[0096] Step 1: Place the sealing cylinder 1 inside the well;

[0097] Step 2: Connect the upper end of the central cylinder 4 of the insertion assembly to the tubing string, and use the tubing string to drive the insertion assembly downward into the sealing cylinder 1;

[0098] Step 3: When the upper end of the limiting cylinder 2 abuts against the upper end of the sealing cylinder 1, the central cylinder 4 is driven to move downward relative to the limiting cylinder 2 by a preset distance through the oil pipe column, so that the force transmission cylinder 3 compresses the upper end face of the sealing element 5 downward, thereby causing the sealing element 5 to expand radially and seal against the inner wall of the sealing cylinder 1.

[0099] In this invention, the central cylinder 4 is moved downward relative to the limiting cylinder 2 by the oil pipe column, thereby causing the force transmission cylinder 3 to compress the sealing element 5. The sealing element 5 expands radially and adheres tightly to the inner wall of the sealing cylinder 1 to form a seal.

[0100] Compared with the existing method of achieving sealing by the interference fit of the sealing component, the method of achieving sealing by the expansion of the sealing element 5 in this invention allows for a larger gap between the sealing cylinder 1 and the insertion tube assembly, thereby avoiding the technical problem of difficulty in inserting the tube due to the small gap between the insertion tube and the sealing cylinder 1.

[0101] Specifically, the radial gap between the outer wall of the cannulation assembly (the outer wall of the limiting cylinder 2) and the inner wall of the sealing cylinder 1 can be set to 0.5 mm to 1.5 mm, preferably 1 mm.

[0102] At the same time, the seal 5 is compressed, which can tightly fill the gap between the sealing cylinder 1 and the insertion tube assembly, ensuring the sealing between the two even if the inner wall of the sealing cylinder 1 is rough or has scratches.

[0103] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0104] The terms "upper" and "lower" used in this invention are defined in their usual sense. For example, referring to the direction of gravity, the direction of gravity is downward, and the opposite direction is upward. Similarly, "upper" refers to the top end, and "lower" refers to the bottom. These terms are used only for clarity of description and are not intended to limit the scope of the invention. Changes or adjustments to these relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0105] Although the invention has been described with reference to preferred embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner as long as there is no structural conflict. The invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A cannula sealer, characterized in that, The application relates to a downhole sealing device. The downhole sealing device comprises a sealing cylinder and a cannula assembly in sealing cooperation with the sealing cylinder. The cannula assembly comprises a center cylinder, a force transmission cylinder, a limiting cylinder and a cylindrical sealing element. The limiting cylinder is arranged on the outer wall of the center cylinder, the inner wall of the limiting cylinder is in sliding sealing cooperation with the outer wall of the center cylinder, and the upper end of the limiting cylinder can abut against the upper end of the sealing cylinder. The force transmission cylinder and the sealing element are sequentially arranged on the outer wall of the limiting cylinder from top to bottom, the upper end of the force transmission cylinder is fixedly connected with the outer wall of the center cylinder, and the lower end surface of the sealing element is fixedly arranged relative to the limiting cylinder. When the upper end of the limiting cylinder abuts against the upper end of the sealing cylinder, the outer wall of the limiting cylinder has a radial gap with the outer wall of the sealing cylinder. When the center cylinder moves downward relative to the limiting cylinder and the sealing cylinder, the force transmission cylinder can compress the upper end surface of the sealing element downward, so that the sealing element expands radially to seal with the inner wall of the sealing cylinder.

2. The cannula sealer of claim 1, wherein, The force transmission cylinder is fixedly connected with the outer wall of the center cylinder through an elastic cylinder. The elastic cylinder is arranged on the outer wall of the center cylinder, and the upper end of the elastic cylinder is threadedly connected with the outer wall of the center cylinder. The lower part of the elastic cylinder is provided with an elastic claw, the inner wall of the upper part of the limiting cylinder is provided with a sliding groove for cooperating with the elastic claw, the elastic claw is slidingly connected in the sliding groove, and the outer wall of the force transmission cylinder is connected with the elastic claw.

3. The cannula sealer of claim 2, wherein, The wall of the elastic claw is provided with a clamping part which protrudes outward of the sliding groove in the radial direction. The force transmission cylinder is provided with a clamping hole matched with the clamping part. The force transmission cylinder and the elastic claw are detachably connected through the clamping hole and the clamping part.

4. The cannula sealer of any of claims 1-3, wherein, The downhole sealing device further comprises a locking assembly. The locking assembly is arranged between the force transmission cylinder and the sealing element to limit the position of the upper end surface of the compressed sealing element.

5. The cannula sealer of claim 4, wherein, The locking assembly comprises a locking slip and a locking stop ring. The locking slip and the locking stop ring are sequentially arranged on the outer wall of the limiting cylinder from top to bottom. The lower end of the locking slip is provided with a first inclined surface, and the upper end of the locking stop ring is provided with a second inclined surface matched with the first inclined surface. When the first inclined surface abuts against the second inclined surface, the locking stop ring extrudes the locking slip inward, so that the inner wall of the locking slip is tightly fixed with the outer wall of the limiting cylinder, and the lower end surface of the locking stop ring limits the position of the upper end surface of the compressed sealing element.

6. The cannula sealer of claim 5, wherein, The inner wall of the locking slip is provided with a reverse tooth, and the tooth tip of the reverse tooth faces upward.

7. The cannula sealer of claim 5 or 6, wherein, The locking assembly further comprises a slip sleeve. The inner wall of the slip sleeve is provided with a guide groove matched with the locking slip and extending in the vertical direction.

8. The cannula sealer of claim 1 or 2, wherein, The lower end of the center cylinder is provided with a guide cylinder. The lower end of the guide cylinder is inwardly contracted in the radial direction, and the upper end surface of the guide cylinder abuts against the lower end surface of the sealing element to limit the position of the lower end surface of the sealing element.

9. The cannula sealer of claim 1 or 2, wherein, The upper end of the limiting cylinder is provided with a limiting boss for abutting against the upper end of the sealing cylinder.

10. A method of installing a cannula sealer as claimed in any one of claims 1 to 9, characterised in that, The downhole sealing device comprises the following steps. The sealing cylinder is prearranged in the well. The upper end of the center cylinder of the intubating assembly is connected to the tubing string, and the intubating assembly is driven downward into the seal cylinder by the tubing string; When the upper end of the limiting cylinder abuts against the upper end of the seal cylinder, the center cylinder is moved downward relative to the limiting cylinder by a preset distance by the tubing string, the force transmission cylinder compresses the upper end surface of the sealing element downward, so that the sealing element expands radially to seal with the inner wall of the seal cylinder.

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