A cement retainer

Abstract

The present invention discloses a cement retainer, comprising a central tube and a lower joint fixedly connected to one end of the central tube, a sealing anchoring structure is sleeved on the circumference of the central tube, one end of the sealing anchoring structure is in contact with the lower joint, and a push ring is arranged between the other end of the sealing anchoring structure and the other end of the central tube; one-way valves are arranged at both ends of the central tube, and when the one-way valve is in a conducting state, an insertion tube for sealing slurry injection passes through the one-way valve and the lower joint. When the sealing is performed, the adapter in the sealing tool is adapted to be connected to one end of the central tube, and the insertion tube for sealing slurry injection is simultaneously inserted into the central tube and extends out of the lower joint. When the cement retainer reaches the set position, the sealing slurry injection operation is directly performed through the insertion tube. After the sealing slurry injection operation is completed, the insertion tube is recovered. After the insertion tube leaves the cement retainer, all the one-way valves become closed, and a blind blockage is formed inside, and the two-way pressure is borne.

Description

Technical Field

[0001] The invention relates to the field of petroleum underground construction, and in particular to a cement retainer. Background Art

[0002] In the middle and late stages of oilfield development, due to the corrosion and perforation of the casing above the cement return height of the oil well, the cement cementing section leaks, causing formation water adjacent to the high-pressure water layer of the oil layer to flow into the wellbore, or the energy of the oil layer drops, the adjacent high-pressure water layer and the oil layer collide with each other, causing water in the oil well or flooding of the oil layer, which brings serious difficulties to the development of the oilfield. At present, some old oil wells that have been in production for many years have long-term high water content and are in a shut-in state. Analysis and judgment: First, after long-term exploitation, the oil layer casing may be corroded and perforated, and the casing leakage may cause flooding of the oil layer; second, the high-pressure water injection well may have long-term high-pressure water injection, forming a water head cone with the oil layer of the well, thereby causing flooding of the oil layer. Third, there may be a high-pressure water layer near the oil layer that collided with the oil layer, causing flooding of the oil layer. The possibility of casing corrosion, perforation and leakage was ruled out for these wells by using packers for leak detection. Using isotope logging, it was found that there was an adjacent high-pressure water layer in the lower part of the oil layer that collided with the oil layer, causing the well to produce water.

[0003] For this situation, the conventional treatment method is to first drill an engineering hole in the high-pressure water layer, and then chemically plug the high-pressure water layer - mainly cement slurry plugging. After plugging, drill the cement plug and resume the production of the oil layer. However, the production oil layer of this well is above the high-pressure water layer and is very close to it. Using conventional plugging methods not only carries a great risk in engineering construction, but also makes it difficult to ensure that the oil layer is not blocked by cement slurry, especially for the high-pressure water layer. It is possible that the high-pressure water layer spits out cement slurry, causing the plugging to fail. Therefore, only the lowering tool can be used to separate the oil layer from the adjacent high-pressure water layer, and then the high-pressure water layer can be plugged.

[0004] Cement retainers have been used for many years. Traditional cement retainers are made of metal and are lowered into the well through drill pipes or oil pipes. Although conventional cement retainers have good sealing properties, high pressure difference resistance, long sealing time, and can also be milled, they are prone to cause liquid backflow during operation, thereby damaging the equipment. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a cement retainer to ensure that after plugging, the wellbore is automatically fully plugged again and bears pressure in both directions.

[0006] The technical solution of the present invention for solving the above-mentioned technical problems is as follows: a cement retainer, comprising a center tube and a lower joint fixedly connected to one end of the center tube, a sealing anchoring structure is circumferentially sleeved on the center tube, one end of the sealing anchoring structure is abutted against the lower joint, and a push ring is arranged between the other end of the sealing anchoring structure and the other end of the center tube; one-way valves are respectively arranged at both ends of the center tube, and the cut-off directions of the two one-way valves are both toward the middle of the center tube; when the one-way valve is in a conducting state, an insertion tube for sealing slurry perfusion passes through the one-way valve and the lower joint.

[0007] The working principle and beneficial effects of the present invention are as follows: the adapter in the sealing tool is connected with one end of the central tube, and the insertion tube for sealing slurry injection is inserted into the central tube at the same time and extends out of the lower joint; at this time, the two one-way valves are in a one-way conduction state, that is, they are in an open state. The cement retainer and its components are lowered to the designated position of the wellbore, and the sealing tool is triggered to generate a certain thrust, which pushes the push ring downward, and the sealing anchoring structure is tightly anchored to the inner wall of the casing; when the thrust provided by the sealing tool continues to increase until it is greater than the limit force of the connecting pin between the sealing adapter and the central tube, the pin is broken and damaged, the sealing and releasing actions are completed, and the cement retainer and the insertion tube remain at the designed sealing depth. At this time, the sealing slurry injection operation is directly carried out through the insertion tube. After the sealing slurry injection operation is completed, the insertion tube is recovered. Since the one-way valve of the cement retainer is in contact with the insertion tube, after the insertion tube leaves the cement retainer, all the one-way valves become closed, forming a blind blockage inside; since the cut-off directions of the two one-way valves are both toward the middle of the central tube; the cement retainer can bear the pressure in the direction of the lower joint because the one-way valve is in a closed cut-off state in the direction of the lower joint; at the same time, since the one-way valve at the other end of the central tube is in a closed cut-off state, it can bear the pressure in the direction of the other end of the central tube.

[0008] Based on the above technical solution, the present invention can also be improved as follows.

[0009] Furthermore, the one-way valve includes a valve body and a valve core, the valve core and the valve body are elastically hingedly connected, the valve body is fixedly connected to the inner wall of the center tube, and the insertion tube passes through the valve body; when the insertion tube leaves the valve body, the valve core is automatically closed by the elastic hinge.

[0010] The beneficial effect of adopting the above further solution is that the valve core is automatically closed by the elastic hinge, no external driving force is required, and it is very reliable, thereby improving the application range of the cement retainer.

[0011] Based on the above technical solution, the present invention can also be improved as follows.

[0012] Furthermore, the valve body at one end of the central tube is connected to the central tube via a fastener to prevent relative position displacement.

[0013] The beneficial effect of adopting the above further scheme is: if the one-way valve and the center tube are connected by threads, when the cement retainer is drilled and ground, the direction of rotation of the drill bit is opposite to the direction of screwing of the threads, so the one-way valve may fall off from the center tube, causing the one-way valve to remain in the well. The center tube and the one-way valve are mutually displaced by means of fasteners, and the relative positions of the center tube and the one-way valve will not change during drilling and grinding. Since the center tube is fixed to the wellbore by a rivet sealing assembly, the one-way valve will not move during drilling and grinding, ensuring that the one-way valve is completely drilled and ground without residue.

[0014] Based on the above technical solution, the present invention can also be improved as follows.

[0015] Furthermore, the valve body at the other end of the central tube is also connected to the central tube via a fastener to prevent relative position displacement.

[0016] The beneficial effect of adopting the above further solution is that the two one-way valves are completely fixed, and the relative position displacement of the central pipe and the one-way valve is avoided, thereby further ensuring the complete drilling and grinding of the cement retainer.

[0017] Based on the above technical solution, the present invention can also be improved as follows.

[0018] Furthermore, the one-way valve is connected to the central tube by threaded engagement.

[0019] The beneficial effect of adopting the above further solution is that the threaded screw connection is a reliable connection and fixing method, which is convenient for assembly and disassembly during assembly and testing.

[0020] Based on the above technical solution, the present invention can also be improved as follows.

[0021] Furthermore, an abutment portion is provided at one end of the lower joint, and the abutment portion abuts against an end of one end of the central pipe.

[0022] The beneficial effect of adopting the above further scheme is that by providing the abutment portion, when the cement retainer is seated, most of the force on the central tube and the lower joint is located at the abutment portion, thereby avoiding the lower joint and the central tube from falling off during the sealing process and improving the sealing reliability of the cement retainer.

[0023] Based on the above technical solution, the present invention can also be improved as follows.

[0024] Furthermore, the sealing anchoring structure includes a cava assembly, a cone and a rubber sleeve, and the rubber sleeve is sleeved in the middle part of the center tube; there are two cones, which are respectively located at both ends of the rubber sleeve and abut against it; there are two cava assemblies, one of which is located between the push ring and one of the cones, and the other cava assembly is located between one of the cones and the lower joint.

[0025] The beneficial effect of adopting the above further solution is that the reliability of anchoring is improved by providing a double slip structure.

[0026] Based on the above technical solution, the present invention can also be improved as follows.

[0027] Furthermore, the slip assembly includes a slip seat and a slip piece, and the slip piece is nested on the slip seat.

[0028] The beneficial effect of adopting the above further solution is that through the anchoring of the slip sheet, the material of the slip seat can be flexibly selected.

[0029] Based on the above technical solution, the present invention can also be improved as follows.

[0030] Furthermore, the central tube, the push ring, the cone, the rubber cylinder, the lower joint and the one-way valve are all made of soluble materials.

[0031] The beneficial effect of adopting the above further scheme is that the materials of the cement retainer of the present invention except the slips are all soluble materials, and the soluble materials are completely dissolved in the formation liquid without any residue, thereby eliminating the drilling and grinding process. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a cross-sectional view of a one-way valve in an open state according to an embodiment of the present invention;

[0033] Figure 2 is a cross-sectional view of an insertion tube inserted into a central tube according to a first embodiment of the present invention;

[0034] Figure 3 is a cross-sectional view of a one-way valve in a closed state according to an embodiment of the present invention;

[0035] Figure 4 It is a partial view of the slip assembly of embodiment 1.

[0036] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0037] 1. Center tube, 2. Push ring, 3. Slip assembly, 4. Cone, 5. Rubber cylinder, 6. Lower joint, 7. Check valve, 71. Valve body, 72. Valve core, 8. Insert tube. DETAILED DESCRIPTION

[0038] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0039] The cross-sectional view of the one-way valve in the open state of the embodiment of the present invention is shown in FIG. Figure 1 , Figure 2 and Figure 3 .

[0040] A cement retainer, comprising a central tube 1 and a lower joint 6 fixedly connected to one end of the central tube 1, a sealing anchoring structure sleeved on the circumference of the central tube 1, one end of the sealing anchoring structure abutting against the lower joint 6, a push ring 2 is arranged between the other end of the sealing anchoring structure and the other end of the central tube 1; one-way valves 7 are arranged at both ends of the central tube 1, and the cut-off directions of the two one-way valves 7 are both toward the middle of the central tube 1; when the one-way valve 7 is in the conducting state, an insertion tube 8 for sealing grout injection passes through the one-way valve 7 and the lower joint 6. Figure 2 shown.

[0041] The working principle of the present invention is as follows: the adapter in the sealing tool is connected to one end of the central tube 1, that is, the adapter is connected to one end of the central tube 11 through a connecting pin, and the insertion tube 8 for sealing slurry injection is inserted into the central tube 1 at the same time, and extends out of the lower joint 6; at this time, the two one-way valves 7 are in a one-way conduction state, that is, they are in an open state. The cement retainer and its components are lowered to the specified position of the wellbore, and a certain thrust is generated by triggering the sealing tool to push the push ring 2 downward. Since the central tube 1 and one end of the central tube 1 are fixedly connected with the lower joint 6, the push ring 2 and the lower joint 6 will squeeze the sealing anchor structure, so that the sealing anchor structure expands and seals with the wellbore, and is tightly anchored with the inner wall of the casing; when the thrust provided by the sealing tool continues to increase until it is greater than the limit force of the connecting pin of the sealing adapter and the central tube 1, the pin is broken and damaged, the sealing and releasing actions are completed, and the cement retainer and the insertion tube 8 remain at the designed sealing depth. At this time, the sealing slurry injection operation is directly carried out through the insertion tube 8. After the sealing slurry injection operation is completed, the insertion tube 8 is recovered. Since the one-way valve 7 of the cement retainer is in contact with the insertion tube 8, after the insertion tube 8 leaves the cement retainer, all the one-way valves 7 are in a closed state, and a blind blockage is formed inside; as shown in Figure 3. Since the cut-off directions of the two one-way valves 7 are both toward the middle of the central tube 1; the cement retainer can bear the pressure in the direction of the lower joint 6 because the one-way valve 7 is in a closed cut-off state in the direction of the lower joint 6; at the same time, since the one-way valve 7 at the other end of the central tube 1 is in a closed cut-off state, it can bear the pressure in the direction of the other end of the central tube 1.

[0042] In this embodiment, the one-way valve 7 includes a valve body 71 and a valve core 72, the valve core 72 and the valve body 71 are connected by an elastic hinge, the valve body 71 is fixedly connected to the inner wall of the central tube 1, and the insertion tube 8 passes through the valve body 71; when the insertion tube 8 leaves the valve body 71, the valve core 72 is automatically closed by the elastic hinge. The elastic hinge can be a torsion spring or the like.

[0043] The valve core 72 is automatically closed by an elastic hinge, does not require external driving force, and is very reliable, thereby improving the application range of the cement retainer.

[0044] In this embodiment, the one-way valve 7 is connected to the central tube 1 by screwing.

[0045] The screw-on connection is a reliable connection and fixing method, which is easy to disassemble and assemble during assembly and testing.

[0046] In this embodiment, the valve body 71 at one end of the central tube 1 is connected to the central tube 1 by a fastener to prevent mutual position displacement; the valve body 71 at the other end of the central tube 1 is also connected to the central tube 1 by a fastener to prevent mutual position displacement. The fastener in this embodiment is a pin, which is not shown in the figure. A through hole is provided in the radial direction of the central tube 1 and the valve body 71, and the pin passes through the through hole, so that the central tube 1 and the valve body 71 will not be displaced.

[0047] Since the one-way valve 7 and the central tube 1 are connected by threads, when the cement retainer is drilled, the direction of rotation of the drill bit is opposite to the direction of screwing of the threads, so the one-way valve 7 may fall off from the central tube 1, causing the one-way valve 7 to remain in the well. The central tube 1 and the one-way valve 7 are mutually displaced by means of fasteners, and the relative positions of the central tube 1 and the one-way valve 7 will not change during drilling and grinding. Since the central tube 1 is fixed to the wellbore by a rivet sealing assembly, the one-way valve 7 will not move during drilling and grinding, ensuring that the one-way valve 7 is completely drilled and ground away without any residue.

[0048] Regarding the fixed connection between the one-way valve 7 and the central tube 1 , other connection methods may be selected, such as directly embedding the one-way valve 7 into the central tube 1 through interference fit.

[0049] The two one-way valves 7 are arranged at the two ends of the central tube. In practical application, the two one-way valves can be arranged at different positions for the convenience of assembly and construction, as long as the left and right sealing is ensured.

[0050] The sealing anchoring structure includes a slip assembly 3, a cone 4 and a rubber tube 5, wherein the rubber tube 5 is sleeved in the middle of the central tube 1; there are two cones 4, which are respectively located at both ends of the rubber tube 5 and abut against it; there are two slip assemblies 3, wherein one slip assembly 3 is located between the push ring 2 and one of the cones 4, and the other slip assembly 3 is located between one cone 4 and the lower joint 6. The slip assembly 3 includes a slip seat 31 and a slip sheet 32, wherein the slip sheet 32 ​​is nested on the slip seat 31.

[0051] The reliability of anchoring is improved by setting up a double slip structure.

[0052] The central tube 1, the push ring 2, the cone 4, the rubber cylinder 5, the lower joint 6 and the one-way valve 7 are all made of soluble materials.

[0053] The cement retainer of the present invention, except for the slips, is made of soluble materials. The soluble materials are completely dissolved in the formation liquid without any residue, thus eliminating the drilling and grinding process.

[0054] Figure 4 A partial view of the slip assembly 3 of the first embodiment. The slip assembly 3 includes a slip seat 31 and a slip piece 32 . The slip piece 32 is nested on the slip seat 31 .

[0055] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A cement retainer, comprising a central tube (1) and a lower joint (6) fixedly connected to one end of the central tube (1), a sealing anchoring structure being sleeved on the circumference of the central tube (1), one end of the sealing anchoring structure being in contact with the lower joint (6), and a push ring (2) being arranged between the other end of the sealing anchoring structure and the other end of the central tube (1); characterized in that: One-way valves (7) are respectively arranged at both ends of the center tube (1), and the cut-off directions of the two one-way valves (7) are both toward the middle of the center tube (1); when the one-way valves (7) are in a conducting state, an insertion tube for sealing slurry injection passes through the one-way valves (7) and the lower joint (6); the one-way valve (7) is connected to the center tube (1) by screwing; and an abutment portion is arranged at one end of the lower joint (6), and the abutment portion abuts against an end of one end of the center tube (1).

2. A cement retainer according to claim 1, characterized in that: The one-way valve (7) comprises a valve body (71) and a valve core (72); the valve core (72) and the valve body (71) are connected by an elastic hinge; the valve body (71) is fixedly connected to the inner wall of the central tube (1); the insertion tube passes through the valve body (71); when the insertion tube leaves the valve body (71), the valve core (72) is automatically closed by the elastic hinge.

3. A cement retainer according to claim 2, characterized in that: The valve body (71) at one end of the central tube (1) is connected to the central tube (1) via a fastener to prevent relative positional displacement.

4. A cement retainer according to claim 3, characterized in that: The valve body (71) at the other end of the central tube (1) is also connected to the central tube (1) via a fastener to prevent relative positional displacement.

5. A cement retainer according to any one of claims 1 to 4, characterized in that: The sealing anchoring structure comprises a slip assembly (3), a cone (4) and a rubber sleeve (5), wherein the rubber sleeve (5) is sleeved on the middle part of the central tube (1); there are two cones (4), which are respectively located at two ends of the rubber sleeve (5) and abut against it; there are two slip assemblies (3), wherein one slip assembly (3) is located between the push ring (2) and one of the cones (4), and the other slip assembly (3) is located between one of the cones (4) and the lower joint (6).

6. A cement retainer according to claim 5, characterized in that: The slip assembly (3) comprises a slip seat (31) and a slip piece (32), wherein the slip piece (32) is nested on the slip seat (31).

7. A cement retainer according to claim 6, characterized in that: The central tube (1), the push ring (2), the cone (4), the rubber cylinder (5), the lower joint (6) and the one-way valve (7) are all made of soluble materials.

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