A downhole centralizing device and method for casing a well

Abstract

The application provides a downhole centralizing device and method for casing deformation well, and relates to the technical field of oil exploitation equipment, which comprises a coiled tubing, at least two sleeves, a connecting rod mechanism and a contact area increasing mechanism. The outer wall of the coiled tubing is provided with a convex ring, the sleeves are slidably sleeved on the coiled tubing, and the convex ring is located in the sleeve to form a pressure cavity. The connecting rod mechanism is connected to the sleeve and is used for expanding outward when the sleeve moves relatively. The sleeve is made close to each other by pressing into the coiled tubing, the connecting rod mechanism is driven to expand in the direction of the well wall to realize centralization. The contact area increasing mechanism increases the contact area with the well wall through the linkage cooperation of the gear, the rack and the top plate, and prevents the connecting rod from sinking into the well wall. The application replaces the traditional air bag type centralizer with a mechanical connecting rod structure, effectively avoids the influence of gravity on the centralizing effect, and ensures that the coiled tubing is accurately kept at the center position of the wellbore.

Description

Technical Field

[0001] This invention relates to the field of oil extraction equipment technology, specifically to a downhole centralization device and method for casing wells. Background Technology

[0002] Coiled tubing technology is widely used in oil and gas exploration and development due to its high efficiency, flexibility, and low cost. Ensuring that the coiled tubing remains centered within the wellbore during its deployment is a critical technical issue affecting operational efficiency and safety. Misalignment not only increases tubing wear and shortens its lifespan but can also cause downhole tools to malfunction, and in severe cases, lead to stuck pipe accidents, hindering exploration or development operations.

[0003] To address the downhole centering problem of coiled tubing, existing technologies typically employ expandable centralizers to ensure tubing string centering. These centralizers primarily address the challenges of centering horizontal well casing and achieving poor cementing quality. Their working principle is mainly based on the compression and release of gas. Specifically, existing expandable centralizers usually consist of two rows of connected balls, which expand and contract by compressing and releasing internal air. When the centralizer reaches the bottom of the well, the balls expand due to the bottomhole reaction force, centering the drill pipe and ensuring close contact with the well wall, thus achieving tubing string centering. When the centralizer needs to be lifted, air flows out of the balls, causing them to contract and deform, allowing the drill pipe to move freely. This structural design aims to prevent severe drill pipe deviation or jamming in complex well conditions and confined spaces.

[0004] However, existing pneumatic expander centralizers have significant technical drawbacks in practical applications. Because the centralizer uses an airbag structure, under gravity, the lower airbag is compressed by the weight of the upper device and the coiled tubing, causing uneven deformation. This deformation causes the actual position of the coiled tubing to shift downwards, making it impossible to achieve precise centering of the tubing string in the wellbore. This gravity-induced shift is particularly pronounced in highly deviated and horizontal wells, severely impacting the centralizing effect. Furthermore, the airbag structure suffers from insufficient reliability and durability, making it prone to damage or failure in the high-temperature, high-pressure downhole environment, posing safety hazards to downhole operations. Summary of the Invention

[0005] The purpose of this invention is to provide a downhole centralization device and method for casing-type wells, which can effectively avoid the influence of gravity on the centralization effect, ensure that the coiled tubing can be stably maintained in the center position of the wellbore under various well conditions, and improve the safety and reliability of downhole operations.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A downhole centralizing device for casing wells, comprising:

[0008] A continuous tubing has a raised ring on its outer wall; at least two sleeves are slidably fitted onto the continuous tubing, the raised ring is located inside the sleeve, and a pressure chamber is formed between the continuous tubing and the sleeve;

[0009] A linkage mechanism, connected to the sleeve, is used to expand outward when the sleeve moves relative to the sleeve;

[0010] In this process, by applying pressure into the coiled tubing, the sleeves are brought closer together, driving the connecting rod mechanism to expand towards the well wall, thereby straightening the coiled tubing.

[0011] Further: the linkage mechanism includes: at least two linkages, one end of each linkage is hinged to different sleeves, and the other end of each linkage is hinged to each other; wherein, when the sleeves approach each other, the hinged parts of the linkages move towards the well wall.

[0012] Furthermore, it also includes:

[0013] The contact area increasing mechanism, which is linked to the linkage mechanism, is used to increase the contact area between the linkage and the well wall;

[0014] The contact area increasing mechanism includes:

[0015] A gear is disposed at the hinge of the connecting rod;

[0016] A rack that meshes with the gear;

[0017] The top plate is slidably connected to the rack;

[0018] When the gear rotates, it causes the rack and the top plate to slide relative to each other, increasing the contact area with the well wall.

[0019] Furthermore, it also includes:

[0020] A support is connected to the continuous tubing;

[0021] The sliding rods are respectively connected to the rack and the top plate;

[0022] Hollow strip, connected to the slide rod;

[0023] When the rack slides, the top plate slides in the opposite direction to the rack through the transmission of the slide rod and the hollow bar.

[0024] Furthermore: it also includes an unlocking mechanism, the unlocking mechanism comprising:

[0025] A retainer is connected to the sleeve via a shear pin, and the retainer is slidably connected to the continuous tubing key; a first pressure relief hole is provided in the retainer.

[0026] A second pressure relief hole is provided in the sleeve;

[0027] When the shear pin is not disconnected, the first pressure relief hole and the second pressure relief hole are not connected; when the continuous tubing is rotated to disconnect the shear pin, the first pressure relief hole and the second pressure relief hole are connected to achieve pressure relief.

[0028] Furthermore, the convex ring and the sleeve are provided with mutually cooperating anti-reverse teeth to maintain the upright state when the pressure decreases; when the coiled tubing is rotated, the anti-reverse teeth separate, allowing the sleeve to slide relative to the coiled tubing.

[0029] Furthermore, it also includes a tension spring connected between the coiled tubing and the linkage mechanism, used to retract the linkage mechanism when the centering is released.

[0030] Furthermore, the connecting rods are arranged in a ring array around the outer wall of the continuous tubing in multiple sets.

[0031] Furthermore, a pressure punch hole is provided on the side wall of the continuous tubing, and the pressure punch hole is connected to the pressure chamber.

[0032] The present invention also provides a downhole centralization method, which uses the above-mentioned downhole centralization device and includes the following steps:

[0033] S1: Lower the coiled tubing to the predetermined position in the well and seal the coiled tubing port;

[0034] S2: Pressurize the coiled tubing, and the pressure is transmitted to the pressure chamber between the sleeves through the pressurization hole;

[0035] S3: The sleeves approach each other under pressure, driving the linkage mechanism to expand towards the well wall;

[0036] S4: The linkage mechanism abuts against the well wall, keeping the coiled tubing in the center of the wellbore and completing the alignment.

[0037] Furthermore, it also includes the step of revoking the original position:

[0038] S5: Rotate the coiled tubing to disconnect the shear pins;

[0039] S6: The first pressure relief hole is connected to the second pressure relief hole, and the pressure chamber is depressurized;

[0040] S7: The linkage mechanism retracts under the action of the tension spring, releasing the upright state.

[0041] Compared with the prior art, the present invention has the following advantages:

[0042] I. Effectively Avoiding Gravity Influences and Achieving Precise Centralization: This invention employs a mechanical linkage centralization structure to replace the traditional pneumatic centralizer. Centralization is achieved through a rigid sleeve-linkage mechanism, fundamentally avoiding deformation caused by the device's gravity. Under pressure, the linkage mechanism expands towards the wellbore, with multiple sets of linkages arranged in a ring array and evenly contacting the wellbore wall, ensuring that the coiled tubing is precisely maintained in the center of the wellbore. This completely solves the technical defect of existing pneumatic centralizers where the tubing position shifts downward due to the deformation of the lower pneumatic bladder.

[0043] II. Preventing Connecting Rod from Getting Stuck in the Wellbore and Improving Centralization Stability: This invention innovatively incorporates a contact area-enhancing mechanism. Through the coordinated operation of gears, racks, and top plates, the rack and top plate can slide synchronously in opposite directions during connecting rod expansion and centralization, significantly increasing the contact area with the wellbore. This design effectively reduces the contact pressure between the connecting rod end and the wellbore, preventing the connecting rod from getting stuck in the wellbore under centralization pressure. This avoids coiled tubing axis misalignment caused by connecting rod getting stuck, greatly improving the stability and reliability of centralization.

[0044] III. Rapid and Controllable Unlocking and Reset Function: This invention achieves rapid release from the uprighting state through the ingenious combination of the shear pin and the pressure relief hole. Simply rotating the continuous tubing disconnects the shear pin, allowing the first and second pressure relief holes to connect and release pressure. The return action of the tension spring ensures reliable retraction of the linkage mechanism. The entire unlocking process is simple to operate, responsive, safe, and controllable, effectively improving operational efficiency.

[0045] IV. Stable and reliable alignment: The present invention has an anti-retraction tooth structure between the convex ring and the sleeve. Even when the pressure in the coiled tubing decreases, the alignment can be maintained by mechanical locking, avoiding the risk of accidental retraction and ensuring the safety and continuity of downhole operations. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the overall structure of the downhole centralization device for casing wells according to the present invention;

[0047] Figure 2 for Figure 1 Enlarged view of part A in the middle.

[0048] In the diagram: 1. Coiled tubing; 11. Convex ring; 12. Pressure test hole; 2. Sleeve; 21. Socket; 22. Shear pin; 23. First pressure relief hole; 24. Second pressure relief hole; 25. Hinge seat; 3. Connecting rod; 31. Gear; 32. Rack; 33. Top plate; 34. Slide rod; 35. Hollow bar; 36. Bracket; 37. Telescopic rod; 38. Tension spring; 4. Bracket; 41. Cylindrical rod. Detailed Implementation

[0049] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0051] Reference Figure 1 and Figure 2 The downhole centralization device for casing-type wells provided by the present invention mainly includes coiled tubing 1, sleeve 2, connecting rod mechanism, contact area enlargement mechanism, unlocking mechanism, and reset mechanism.

[0052] A convex ring 11 is fixedly installed on the outer wall of the coiled tubing 1. The convex ring 11 has a ring structure and is firmly connected to the outer wall of the coiled tubing 1. There are two sleeves 2, which are symmetrically slidably sleeved on the coiled tubing 1, with the convex ring 11 located in the internal space of the sleeve 2. A pressure punching hole 12 is opened on the side wall of the coiled tubing 1. The pressure punching hole 12 connects to the internal space of the sleeve 2, so that the inside of the coiled tubing 1 is connected to the pressure chamber formed between the convex ring 11 and the sleeve 2. This structural design allows the pressure to be transmitted to the pressure chamber through the pressure punching hole 12 when pressure is applied to the coiled tubing 1, generating a thrust on the sleeves 2 on both sides of the convex ring 11.

[0053] The linkage mechanism includes multiple sets of links 3, arranged in a ring array around the outer wall of the coiled tubing 1. Each set of links includes two links 3. One end of one link 3 is hinged to a sleeve 2 via a hinge seat 25, and one end of the other link 3 is hinged to another sleeve 2 via a hinge seat 25. The other ends of the two links 3 are hinged together to form a movable hinge point. When the two sleeves 2 approach each other under pressure, the hinge point of the links 3 moves radially outward, that is, expands towards the well wall. The arrangement of multiple sets of links 3 ensures a uniform distribution of the centralizing force in the circumferential direction, enabling the coiled tubing 1 to be stably maintained at the center of the wellbore.

[0054] To prevent the end of connecting rod 3 from sinking into the wellbore under normalizing pressure, this invention features a contact area enlargement mechanism. A gear 31 is installed at the hinge of the two connecting rods 3, and is fixedly connected to one of the connecting rods 3. A telescopic rod 37 is connected to the coiled tubing 1 at the midpoint between the two sleeves 2, and the end of the telescopic rod 37 is connected to a bracket 36. A rack 32 and a top plate 33 are slidably connected to the bracket 36. The rack 32 meshes with the gear 31, and the top plate 33 is in contact with the rack 32 and can slide relative to it. The rack 32 and the top plate 33 can remain parallel to the axis of the coiled tubing 1.

[0055] Both the rack 32 and the top plate 33 are connected to sliding rods 34, and hollow bars 35 are connected to both sliding rods 34. Specifically, two clamps are fitted onto the coiled tubing 1, and the two clamps are connected to an n-shaped support 4. A cylindrical rod 41 is located in the middle of the upper horizontal section of the n-shaped support 4, and the middle part of the hollow bar 35 is rotatably connected to this cylindrical rod 41 through a bearing. When the gear 31 rotates, it drives the rack 32 to slide, and the sliding rods 34 connected to the rack 32 slide inside the hollow bar 35, thereby driving the hollow bar 35 to swing. Since the middle part of the hollow bar 35 is constrained, the upper and lower parts swing in opposite directions. The upper hollow bar 35 pushes the sliding rods 34 on the top plate 33, causing the top plate 33 and the rack 32 to slide synchronously and in opposite directions. The rack 32 has a certain width, and when the top plate 33 and the rack 32 slide against each other, the surface area of ​​contact between the two and the well wall increases significantly, thereby reducing the pressure between the end of the connecting rod 3 and the well wall.

[0056] The unlocking mechanism is designed to allow the centering device to quickly and reliably release from centering. The retainer 21 is connected to the sleeve 2 via a shear pin 22. The retainer 21 and the coiled tubing 1 are connected by a keyed sliding connection, ensuring that the retainer 21 can slide axially relative to the coiled tubing 1 but cannot rotate relative to it. The retainer 21 has a first pressure relief hole 23, and the sleeve 2 has a second pressure relief hole 24. Under normal centering conditions, the shear pin 22 remains intact, and the first and second pressure relief holes 23 and 24 are offset and not connected, keeping the pressure chamber sealed. When centering needs to be released, the coiled tubing 1 is rotated. Because the sleeve 2 is fixed to the wellbore via the connecting rod 3 and is not easily rotated, the coiled tubing 1 drives the retainer 21, which is keyed to it, to rotate. The resulting torque causes the shear pin 22 to disengage. After the shear pin 22 disengages, the retainer 21 can rotate relative to the sleeve 2, aligning and connecting the first and second pressure relief holes 23 and 24, releasing the pressure in the pressure chamber.

[0057] A mutually engaging anti-retraction tooth structure is provided between the convex ring 11 and the sleeve 2. The anti-retraction tooth design ensures that the sleeve 2 remains in the upright position when the pressure inside the coiled tubing 1 decreases, preventing accidental retraction. When the coiled tubing 1 rotates, the convex ring 11 rotates synchronously, causing the anti-retraction teeth between the convex ring 11 and the inner wall of the sleeve 2 to separate, at which point the sleeve 2 can slide freely relative to the coiled tubing 1.

[0058] The reset mechanism includes a tension spring 38, which is connected between the support 36 and the coiled tubing 1. Under normal uprighting conditions, the tension spring 38 is in a stretched state. When the pressure chamber is depressurized and the anti-retraction teeth separate, the restoring force of the tension spring 38 pulls the support 36 closer to the coiled tubing 1, thereby causing the end of the connecting rod 3 to move away from the wellbore, and causing the connecting rod mechanism to return to its initial state.

[0059] The normalization method of the present invention is implemented as follows: First, the coiled tubing 1 is lowered into the well. After the coiled tubing 1 is lowered to a predetermined depth, the end of the coiled tubing 1 is sealed. Then, pressure is applied to the coiled tubing 1, and the pressure is transmitted through the pressure hole 12 to the pressure chamber between the convex ring 11 and the sleeve 2. Under the action of pressure, the two sleeves 2 overcome the tension of the tension spring 38 and move closer to each other, driving the hinged part of the connecting rod 3 to move towards the well wall. The hinged parts of multiple sets of connecting rods 3 abut against the well wall, stably supporting the coiled tubing 1 at the center position of the wellbore, completing the normalization operation.

[0060] During the straightening process, as the connecting rod 3 expands outward, the gear 31 rotates synchronously and drives the rack 32 to slide. Through the transmission mechanism of the slide rod 34 and the hollow bar 35, the top plate 33 and the rack 32 slide in opposite directions, increasing the contact area with the well wall and effectively preventing the connecting rod 3 from sinking into the well wall.

[0061] When it is necessary to release the straightening state, the operator rotates the coiled tubing 1, and the shear pin 22 disconnects under torque, connecting the first pressure relief hole 23 and the second pressure relief hole 24 to relieve pressure. Simultaneously, the rotation of the coiled tubing 1 causes the anti-retraction teeth to separate, and the sleeve 2 returns to its free-sliding state. Under the restoring force of the tension spring 38, the support 36 drives the linkage mechanism to retract, and the end of the linkage 3 detaches from the wellbore, at which point the coiled tubing 1 can be pulled out of the well.

[0062] Taking a casing deformation well in an oilfield as an example, the well experienced casing deformation at a depth of 2500 meters, requiring well workover operations using coiled tubing. Using the straightening device of this invention, the straightening procedure was initiated when the coiled tubing was lowered to a depth of 2480 meters. Pressure was applied to the coiled tubing to 8 MPa, causing the casings to move closer together by approximately 150 mm under pressure. The six connecting rods simultaneously expanded outwards, with their ends stably abutting against the well wall. Through the contact area increasing mechanism, the contact area between each connecting rod end and the well wall reached approximately 120 square centimeters, with the contact pressure controlled within a reasonable range, preventing the connecting rods from sinking into the formation. The eccentricity of the straightened coiled tubing was less than 5 mm, fully meeting the requirements for well workover operations. After the operation was completed, the coiled tubing was rotated 15 turns, the shear pins disengaged, the system was depressurized, and the connecting rod mechanism retracted completely within 2 seconds, successfully pulling the coiled tubing out of the wellbore. The entire straightening and release process was simple to operate, safe, and reliable, significantly improving operational efficiency.

[0063] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A downhole centralizing device for casing wells, characterized in that, include: A continuous tubing has a raised ring on its outer wall; two sleeves are slidably fitted onto the continuous tubing, the raised ring is located inside the sleeve, and a pressure chamber is formed between the continuous tubing and the sleeve; A linkage mechanism includes two links, one end of which is respectively hinged to different sleeves, and the other ends of the two links are hinged to each other to form a hinge point. In this process, by applying pressure into the coiled tubing, the sleeves are brought closer together, causing the hinge point of the connecting rod to move radially outward, driving the connecting rod mechanism to expand towards the well wall, thereby achieving the straightening of the coiled tubing; The linkage mechanism includes at least two links, one end of each link being hinged to different sleeves, and the other ends of each link being hinged to each other; wherein, when the sleeves approach each other, the hinged portions of the links move toward the well wall. It also includes: a contact area increasing mechanism, which is linked to the linkage mechanism to increase the contact area between the linkage and the well wall; The contact area increasing mechanism includes: A gear is disposed at the hinge of the connecting rod; A rack that meshes with the gear; The top plate is slidably connected to the rack; A support is connected to the continuous tubing; The sliding rods are respectively connected to the rack and the top plate; Hollow strip, connected to the slide rod; When the gear rotates, it causes the rack and the top plate to slide relative to each other, increasing the contact area with the well wall; when the rack slides, the top plate slides in the opposite direction to the rack through the transmission of the slide rod and the hollow bar.

2. The downhole centralization device according to claim 1, characterized in that, It also includes an unlocking mechanism, which comprises: A retainer is connected to the sleeve via a shear pin, and the retainer is slidably connected to the continuous tubing key; a first pressure relief hole is provided in the retainer. A second pressure relief hole is provided in the sleeve; When the shear pin is not disconnected, the first pressure relief hole and the second pressure relief hole are not connected; when the continuous tubing is rotated to disconnect the shear pin, the first pressure relief hole and the second pressure relief hole are connected to achieve pressure relief.

3. The downhole centralization device according to claim 2, characterized in that, The convex ring and the sleeve are provided with mutually cooperating anti-retraction teeth to maintain the upright state when the pressure decreases; when the coiled tubing is rotated, the anti-retraction teeth separate, allowing the sleeve to slide relative to the coiled tubing.

4. The downhole centralization device according to claim 1, characterized in that, It also includes a tension spring connected between the coiled tubing and the linkage mechanism, used to retract the linkage mechanism when the centering is released.

5. The downhole centralization device according to claim 1, characterized in that, The connecting rods are arranged in a ring array around the outer wall of the continuous tubing in multiple sets.

6. The downhole centralization device according to claim 1, characterized in that, A pressure punch hole is provided on the side wall of the continuous tubing, and the pressure punch hole is connected to the pressure chamber.

7. A downhole centralization method, employing the downhole centralization device according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1: Lower the coiled tubing to the predetermined position in the well and seal the coiled tubing port; S2: Pressurize the coiled tubing, and the pressure is transmitted to the pressure chamber between the sleeves through the pressurization hole; S3: The sleeves approach each other under pressure, driving the linkage mechanism to expand towards the well wall; S4: The linkage mechanism abuts against the well wall, keeping the coiled tubing in the center of the wellbore and completing the alignment.

8. The downhole centralization method according to claim 7, characterized in that, It also includes the steps to remove the corrective action: S5: Rotate the coiled tubing to disconnect the shear pins; S6: The first pressure relief hole is connected to the second pressure relief hole, and the pressure chamber is depressurized; S7: The linkage mechanism retracts under the action of the tension spring, releasing the upright state.

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