Single piston eccentric extrusion type cement sheath fracturing tool

Abstract

The application discloses a single-piston eccentric extrusion type cement sheath breaking tool, which comprises a main shaft, one end of the main shaft is internally formed with a piston groove, and an eccentric angle is formed between the central axis of the piston groove and the central axis of the main shaft; a piston is embedded in the piston groove, the tail end of the piston penetrates through the piston groove and is connected with a pressing head, and a crushing zone is arranged on the circumference of the pressing head. Under the rotation of a drilling machine, the eccentric distance between the pressing head and a drill rod is increased, the eccentric extrusion force on the casing is increased, the cement sheath is crushed and damaged, the cement sheath at the circumferential position of the pressing head is also damaged, under the pulling action of the drilling machine, the damage width of the tool on the cement sheath is gradually increased, and finally the whole downhole cementing cement is damaged. The tool adopts a single-piston eccentric rolling extrusion operation mode to crush the cementing cement layer, damages the cementing effect between the casing and the cement sheath, greatly reduces the casing pulling force, reduces the abandoned well operation cycle, and improves the casing recovery operation efficiency.

Description

Technical Field

[0001] This invention relates to the field of abandoned well casing recovery technology, and in particular to a single-piston eccentric extrusion cement ring crusher. Background Technology

[0002] With the long-term development and utilization of oil fields, oil and gas resources are gradually depleted, and a large number of oil and gas wells are permanently abandoned. When using subsea wellhead equipment, in order to achieve oil and gas isolation and avoid environmental pollution and ecological damage caused by residual oil and gas leakage, permanent well abandonment operations should be carried out in accordance with industry requirements. Temporary well abandonment and exploratory wells should be permanently abandoned. The number of oil and gas wells requiring abandonment operations is increasing year by year. The "GB2019 Oil and Gas Drilling Marine Well Abandonment Operation Regulations" requires that well abandonment operations should select an appropriate well depth to cut and retrieve the casing layer by layer from the inside to the outside, and then permanently seal it with cement. After the cementing operation is completed, the inner casing, cement sheath, outer casing and formation are bonded together due to the solidification of cement slurry, which greatly increases the resistance to pulling out the casing, making it difficult or even impossible to pull out the casing from the wellbore. Cutting a small section of casing first and then pulling it out step by step will increase the well abandonment operation cycle and cost. In short, the traditional casing recovery method for well abandonment operations is far from meeting the market demand for well abandonment operations, and it is necessary to develop new technologies based on innovative methods to improve it. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a single-piston eccentric compression cement sheath crushing tool to improve casing recovery efficiency in well abandonment operations. This invention innovatively uses a single-piston eccentric compression method to indirectly crush the cement sheath, reducing the bonding effect between the casing and the cement sheath. This ensures efficient well abandonment operations while lowering operating costs.

[0004] The present invention is achieved by the following technical solution.

[0005] A single-piston eccentric compression crushing tool for cement rings includes a main shaft, one end of which forms an inward piston groove, and the central axis of the piston groove forms an eccentric angle with the central axis of the main shaft; a piston is embedded in the piston groove, and the end of the piston extends out of the piston groove and connects to a crushing head, and the crushing head is provided with a crushing band in the circumferential direction.

[0006] Furthermore, a stabilizer is provided on the side of the main shaft away from the pressure head.

[0007] Furthermore, the centralizer includes a carbide shell, and radial bearings arranged in parallel are provided between the carbide shell and the main shaft; thrust bearings are installed on both sides of the radial bearings, and limit blocks and limit rings are respectively provided on the outer sides of the two thrust bearings.

[0008] Furthermore, a hard alloy sleeve is provided on the inner wall of the piston groove, and the piston is placed inside the hard alloy sleeve.

[0009] Furthermore, a sealing ring is provided between the piston and the hard alloy sleeve.

[0010] Furthermore, the end of the main shaft with the piston groove is provided with an end cap.

[0011] This application has the following beneficial effects.

[0012] (1) The cement ring crushing tool of the present invention has a simple structure, is easy to process and manufacture, and has good practicality. The bearings used are all standard parts, which are easy to purchase, inspect and replace. During the casing recycling operation, the piston obtains eccentric thrust from the pressurized high-pressure fluid. Then the main shaft rotates to drive the piston and the pressure head, squeezing the casing to produce elastic deformation, which indirectly causes the cement ring to break. A gap is formed between the casing and the cement ring, which achieves the effect of destroying the bonding force between the casing and the cement ring, reducing the resistance to pulling the casing, making the process of pulling out the casing easier, reducing the casing recycling operation cycle, improving the success rate of casing recycling, and reducing the operating cost. It has positive reference significance and promotion value for improving the casing recycling operation mode.

[0013] (2) The pressure head in the cement ring crushing tool of the present invention increases the squeezing effect on the sleeve under the action of eccentric force, so that the sleeve material only produces elastic deformation and does not produce any plastic deformation, thus avoiding the situation where the sleeve is stuck due to permanent deformation caused by excessive squeezing of the sleeve. Once the cement ring is stuck, the pulling force of the sleeve will increase.

[0014] (3) The cement sheath breaking tool of the present invention has a wide range of application conditions. It fully considers the eccentricity between the casing and the cement sheath during actual cementing operations. Even under the most extreme eccentricity conditions between the casing and the cement sheath, the tool of the present invention can still achieve the expected results and will not damage the outer casing of the cement sheath. It can effectively prevent toxic and harmful substances from leaking into the formation. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the present invention;

[0016] Figure 2 This is a schematic diagram of the main shaft of the present invention;

[0017] Figure 3 This is a schematic diagram of the pressure head of the present invention;

[0018] Figure 4 This is a schematic diagram illustrating the working principle of the present invention.

[0019] Among them, 1. main shaft; 101. piston groove; 102. hydraulic channel; 103. connection port; 104. stepped surface; 2. limit block; 3. thrust bearing; 4. radial bearing; 5. limit ring; 6. centralizer; 7. carbide shell; 8. piston; 9. sealing ring; 10. carbide sleeve; 11. end cap; 12. crushing band; 13. pressure head; 14. formation; 15. outer casing; 16. cement ring; 17. casing. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] like Figure 1-3 As shown, a single-piston eccentric compression type cement ring crusher includes a main shaft 1, which is a stepped structure composed of two cylindrical sections of unequal diameter. The main shaft 1 contains an interconnected cylindrical hydraulic channel 102 and a cuboid piston groove 101. The end of the hydraulic channel 102 away from the piston groove 101 is enlarged to form a frustum-shaped connection port 103, located at the end of the smaller diameter section of the main shaft 1. The connection port 103 is used to connect to a drill bit, thereby allowing high-pressure fluid to act on the piston 8. The piston groove 101 is inclined within the larger diameter section of the main shaft 1, and an eccentric angle is formed between the central axis of the piston groove 101 and the central axis of the main shaft 1. The eccentric angle is 5–10°, and needs to be calculated and adjusted according to the actual pipe diameter and tool size.

[0022] An end cap 11 is installed at the end of the spindle 1 (the end with the piston groove 101), and a through hole is formed on the end cap 11, the position of which corresponds to the piston groove 101.

[0023] The piston groove 101 of this application has a cemented carbide sleeve 10 on its inner wall, and a piston 8 is inserted inside the cemented carbide sleeve 10. A sealing ring 9 is provided between the cemented carbide sleeve 10 and the piston 8 for sealing. Specifically, the two ends of the piston 8 are different in size and structure. The larger end is rectangular and the smaller end is cylindrical. The larger end is placed inside the cemented carbide sleeve 10, and the smaller end protrudes through the through hole of the end cap 11. The diameter of the through hole on the end cap 11 is larger than the outer diameter of the cylindrical part of the smaller end of the piston 8 and smaller than the length of the diagonal of the rectangular part of the larger end of the piston 8. By limiting the larger end of the piston 8, the overall extension length of the piston 8 is restricted.

[0024] The small end of the piston 8 passes through the through hole of the end cap 11 and connects to the pressure head 13. Specifically, the pressure head 13 is spherical, with the bottom surface of the spherical crown recessed inward to form a groove. A thread is formed on the side wall of the groove to connect with the small end of the piston 8. The surface of the pressure head 13 is provided with a crushing band 12 to increase the compressive force. The crushing band 12 is arranged circumferentially around the pressure head 13 and is fixed to the pressure head 13 by welding. Under hydraulic pressure, the piston 8 can move within the hard alloy sleeve 10, causing the pressure head 13 to extend, increasing the eccentricity with the main shaft 1, and generating eccentric motion under the drive of the main shaft 1.

[0025] The tool in this application also includes a centralizer 6, which is mounted on the small-diameter section of the main shaft 1 via two sets of bearings and a limiting block 2. Specifically, the centralizer 6 includes a carbide shell 7, radial bearings 4, and thrust bearings 3. Two radial bearings 4 are installed on the inner ring of the carbide shell 7, and thrust bearings 3 are provided on both sides of the radial bearings 4. The thrust bearings 3 and radial bearings 4 are mounted side by side on the small-diameter section of the main shaft 1. A limiting ring 5 and a limiting block 2 are respectively provided on the outer side of the two thrust bearings 3. The limiting ring 5 abuts against the stepped surface 104 of the main shaft 1, and the limiting block 2 has screw holes that mate with screw holes on the main shaft 1. The limiting block 2 is fixed to the main shaft 1 by screw connection. The limiting ring 5 and the limiting block 2 provide axial limiting for the centralizer 6, and integrate the carbide shell 7, thrust bearings 3, and radial bearings 4 into a whole.

[0026] The working principle of this invention is as follows:

[0027] Figure 4 (a) shows the initial state of the tool as it is lowered into the well with the drill pipe. When it is necessary to crush and destroy the cement sheath 16, high-pressure fluid is injected into the tool to push the piston 8, causing the pressure head 13 to extend and contact the casing 17, maintaining its working state. At this time, the position of the pressure head is as shown in the image. Figure 4 As shown in (b), the pressure head 13 compresses the casing 17. Under the rotation of the drilling rig, the tool rotates, and the tool applies an eccentric compressive force to the casing 17. There is a crushing zone 12 on the pressure head 13. During the compression operation, the contact force can be significantly increased to form initial damage, which in turn causes the cement sheath 16 to crush. At the same time, under multiple rotations, the cement sheath 16 at the circumferential position of the pressure head 13 will be destroyed. Under the upward pull of the drilling rig, the axial damage width of the cement sheath 16 gradually increases until the entire expected downhole cementing sheath is completely destroyed. When the tool rotates, the reaction force of the sleeve 17 on the pressure head 13 is transmitted to the spindle 1 by the piston 8, causing the tool to become eccentric. At this time, one side of the stabilizer 6 contacts the surface of the sleeve 17, and the reaction force of the sleeve 17 on the stabilizer 6 is transmitted to the radial bearing 4 and the spindle 1 in sequence. The stabilizer 6 increases the eccentric force while protecting the drill pipe and the tool as a whole, avoiding excessive wear on the tool and ensuring the safety of the operation.

[0028] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A single piston eccentric extruding cement sheath breaking tool comprising a main shaft (1), characterized in that: One end of the main shaft (1) forms a piston groove (101) inward, and the end of the main shaft (1) with the piston groove (101) is provided with an end cap (11); the central axis of the piston groove (101) and the central axis of the main shaft (1) form an eccentric angle, the angle of which is 5~10°; the piston (8) is embedded in the piston groove (101), the end of the piston (8) passes through the piston groove (101) and is connected to the pressure head (13), the pressure head (13) is spherical, and the pressure head (13) is provided with a crushing band (12) on its circumference; the large end of the piston (8) is rectangular, and the small end is cylindrical, the large end is placed in the piston groove (101), and the small end passes through the through hole of the end cap (11), the diameter of the through hole on the end cap (11) is larger than the outer diameter of the small end of the piston (8) cylinder, and smaller than the diagonal length of the side of the large end of the piston (8) near the end cap.

2. A single piston eccentric extruding cement sheath fracturing tool according to claim 1, characterized in that: A stabilizer (6) is provided on the side of the main shaft (1) away from the pressure head (13).

3. A single piston eccentric extruding cement sheath fracturing tool according to claim 2, characterized in that: The centralizer (6) includes a carbide shell (7), and radial bearings (4) arranged in parallel are provided between the carbide shell (7) and the main shaft (1); thrust bearings (3) are installed on both sides of the radial bearings (4), and limit blocks (2) and limit rings (5) are respectively provided on the outer side of the two thrust bearings (3).

4. A single piston eccentric extruding cement sheath fracturing tool according to claim 1, characterized in that: The piston groove (101) is provided with a hard alloy sleeve (10) on its inner wall, and the piston (8) is placed inside the hard alloy sleeve (10).

5. A single piston eccentric extruding cement sheath fracturing tool according to claim 4, characterized in that: A sealing ring (9) is provided between the piston (8) and the hard alloy sleeve (10).

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