Integral casing elastic centralizer and processing method thereof

Abstract

A seamless steel pipe is obtained through hot rolling of spring steel, the seamless steel pipe is placed in a mold cavity, ultrahigh-pressure liquid is injected into the closed seamless steel pipe, meanwhile, axial thrust is applied to the two ends of a pipe blank, the middle of the seamless steel pipe is made to expand outwards, and the integral casing pipe elastic centralizer is obtained. An arc-shaped contour is formed by attaching the arc-shaped contour to a die, a plurality of hollowed-out parts are formed at the arc-shaped contour through methods such as laser cutting or stamping, elastic centralizing spokes are formed between the adjacent hollowed-out parts, and finally heat treatment and surface treatment are conducted on the whole. An internal high-pressure integral forming method is adopted, so that the integral casing elastic centralizer is not provided with a welding seam or a connecting mechanism, the problem of excessive stress concentration does not exist in the manufacturing process, the size precision and the profile tolerance of a generated arc profile are higher, the fatigue resistance is higher, the service life is longer, and the production cost is lower. The integral casing elastic centralizer manufactured by the method can smoothly pass through a narrowed and bent part under a well.

Description

Technical Field

[0001] The invention relates to an integral casing elastic centralizer and a processing method thereof. Background Art

[0002] Centralizers include elastic centralizers, rigid centralizers, blade centralizers and spiral centralizers.

[0003] At present, the depth of domestic wells is getting deeper and deeper. In order to ensure that the downhole tools can work in the center when going down the well, they need to use the casing and the inner wall of the well. At the same time, due to the existence of angles and inclinations, in order to prevent the casing from contacting the inner wall of the well and causing wear, a centralizer with a larger outer diameter is usually connected in series to ensure that the casing is as centered as possible during operation. Commonly used casing centralizers mainly include elastic centralizers and rigid centralizers, both of which have certain disadvantages. The problem that the commonly used centralizers are prone to is that the outer diameter of the tubing is small, the distance between it and the inner wall of the well is large, and the tubing itself has low rigidity, so it is not easy to center.

[0004] At present, there are also so-called "integrated" elastic stabilizers, which are usually formed by welding a steel plate into a cylinder, or dividing the steel plate into multiple parts such as a coupling and a straightening bar and then welding them together. Although this type of stabilizer can be said to be integrated, there must be multiple welds in its structure. These welds will form stress concentration areas or stress weak areas. When the straightening bar spokes are subjected to a large load, it is easy to cause welding failure, resulting in permanent deformation, insufficient reset force of the stabilizer, and insufficient centering of the oil pipe or casing in the wellbore. Moreover, the deformed stabilizer cannot be reused, and the cost is relatively high. Therefore, this integrated elastic stabilizer can only be used as a casing stabilizer, not as a tubing stabilizer.

[0005] Centralizers used for tubing are usually the blade centralizers or spiral centralizers mentioned above. They are usually welded to the tubing and therefore have no elasticity. They are usually large in size and supported between the tubing and the inner wall of the well. However, when the inner wall of the well is uneven and there are narrowed or curved parts, the passage of such centralizers will become very difficult, causing the tubing to get stuck in the well. Currently, when encountering such a situation, the operator can only press down the tubing harder, which may cause the packer on the tubing to be set prematurely or other unexpected situations to occur. This operation is very dangerous in weak formations.

[0006] The Chinese invention patent with announcement number CN113802997A and announcement date December 17, 2021, discloses an integral casing elastic straightener and a method for manufacturing the same. A hollow portion is formed on the elastic cylinder obtained by casting, and the middle part of the hollowed-out cylinder is deformed to bulge outward to form an arc-shaped contour as a straightening spoke. The integral casing elastic straightener manufactured by this method does not have welds or connection structures, can produce a certain reset deformation and has a large reset force, and can be used as an oil pipe straightener. However, the straightening strip formed by this method is prone to concentrated stress at the coupling during processing, and the curvature and thickness formed are uneven, and the precision is not high enough, resulting in the straightening strip not being able to fit well with the inner wall of the well, resulting in poor centering between the oil pipe and the inner wall of the well.

[0007] Therefore, a new method for manufacturing an integral elastic casing centralizer is needed, and the centralizer manufactured by this method can smoothly pass through the narrowed part or curved part of the oil well without stress concentration, uneven curvature, and large profile deviation, so as to avoid the occurrence of the above-mentioned situations. Summary of the invention

[0008] In order to overcome the above-mentioned deficiencies, the present invention provides an integral elastic centralizer and a processing method thereof, which can improve the problems of low size and contour accuracy of the elastic centralizer, stress concentration during deformation and uneven curvature.

[0009] To achieve this purpose, the method adopted by the present invention is: an integral casing elastic straightener, including an upper coupling and a lower coupling, the upper coupling and the lower coupling are symmetrically arranged up and down, and are connected to each other through a plurality of elastic straightening strips in the middle, the two ends of the elastic straightening strips are respectively connected to the upper coupling and the lower coupling, and the middle protrudes outward in an arc shape.

[0010] It comprises at least four elastic straightening spokes which are evenly arranged in a ring shape.

[0011] The processing method of the integral casing elastic centralizer includes the following steps:

[0012] S1: hot-rolled seamless steel tube made of spring steel;

[0013] S2: Place the seamless steel pipe in a specific mold cavity, inject ultra-high pressure liquid into the sealed seamless steel pipe through special equipment, and apply axial thrust at both ends of the tube blank to make the middle part of the seamless steel pipe bulge outward radially and fit with the mold cavity, forming an arc profile in the middle part of the seamless steel pipe;

[0014] S3: forming a plurality of hollow portions at the arc-shaped contour, wherein the plurality of hollow portions are spaced apart from each other to form elastic straightening spoke portions between adjacent hollow portions;

[0015] S4: heat treatment and surface treatment are performed on the integral casing elastic centralizer after the shaping treatment.

[0016] After hot rolling, the end face of the seamless steel pipe is processed to ensure the flatness of the end face.

[0017] The spring steel is 65Mn, 60Si2Mn or 55CrMnA.

[0018] The ultra-high pressure liquid pressure is 80MPa ~ 200MPa, the axial thrust applied at both ends of the seamless steel pipe is 200 tons ~ 400 tons, and the nominal clamping force is 2000 tons ~ 4000 tons.

[0019] The heat treatment is quenching treatment, and the quenching temperature is 800-900°C; annealing treatment can be appropriately added, and the annealing temperature is 600-750°C, and the temperature is kept for 1-3 hours and slowly cooled to room temperature in the annealing furnace.

[0020] The surface treatment includes surface shot peening, surface electrophoresis, surface painting, surface spraying and the like.

[0021] The beneficial effects are as follows: the present invention adopts an internal high-pressure integral forming method, so that the integral casing elastic centralizer has no welds or connecting mechanisms, there is no problem of excessive stress concentration in the manufacturing process, and the resulting arc profile has higher dimensional accuracy and outer contour, and has higher fatigue resistance and service life. The integral casing elastic centralizer manufactured by this method can smoothly pass through the narrowing and bending parts under drilling, so that the drill pipe equipment and the like downhole can be kept centered in the wellbore and delivered into place. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0023] Figure 1 It is a front view of the present invention;

[0024] Figure 2 It is a perspective view of the present invention. DETAILED DESCRIPTION

[0025] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0026] In the description of the invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0027] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components; the fixed connection can be welding or gluing. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] like Figure 1 , Figure 2 As shown, the integral casing elastic centralizer A comprises an upper coupling 1 and a lower coupling 4. The upper coupling 1 and the lower coupling 4 are annular structures, which are sleeved on the oil pipe and are symmetrically arranged from top to bottom. The upper coupling 1 and the lower coupling 4 are connected to each other through a plurality of elastic centralizing spokes 2. The two ends of the elastic centralizing spokes 2 are respectively connected to the upper coupling 1 and the lower coupling 4. The middle part protrudes outward in an arc shape. A hollow part 3 is formed between adjacent elastic centralizing spokes 2. The hollow part 3 ensures the telescopic space. Preferably, four elastic centralizing spokes 2 are arranged evenly in an annular shape. The adjacent elastic centralizing spokes 2 are spaced 90° apart. The elastic centralizing spokes 2 arranged in this way can provide the maximum lateral force for support on the inner wall of the well.

[0029] The processing steps of the above-mentioned integral casing elastic centralizer A are as follows:

[0030] S1: A seamless steel pipe is obtained by hot rolling, preferably 65Mn steel, which contains chromium, molybdenum, vanadium and nickel, and the end face of the seamless steel pipe is processed to ensure the flatness of the end face.

[0031] S2: Place the processed seamless steel pipe into the lower mold of the internal high pressure forming machine. After the upper mold is closed, the clamps at both ends of the seamless steel pipe are also moved longitudinally to seal the seamless steel pipe and inject high-pressure liquid. As the internal pressure increases, the clamps at both ends also increase the pressure to continuously feed the material until the middle of the seamless steel pipe protrudes radially outward to form an arc profile and matches the profile of the upper and lower molds. The ultra-high pressure liquid pressure applied in this step is between 80MPa-200MPa, the axial thrust applied at both ends of the seamless steel pipe is between 200 tons and 400 tons, and the nominal clamping force is 2000 tons-4000 tons.

[0032] In the above-mentioned internal high pressure forming process, the seamless steel pipe does not need to be heated, and the deformation can be completed at room temperature. The material properties will not be changed due to heating. High-precision dimensional control can be performed during forming, and uniform deformation can be achieved, avoiding the thermal expansion and contraction problems that may occur during heat treatment. In addition, the heating process is simplified during large-scale production, and production efficiency is improved.

[0033] S3: A plurality of hollow parts spaced apart from each other are formed at the arc-shaped contour in the middle of the seamless steel pipe by means of wire sawing or laser cutting, so as to form elastic straightening spokes 2 between adjacent hollow parts 3, so that the integral casing elastic straightening device has a uniform thickness as a whole, and the width of the elastic straightening spokes 2 is uniform, thereby enhancing the overall strength.

[0034] S4: Finally, the integral casing elastic straightener is subjected to heat treatment and surface treatment. The heat treatment is quenching treatment, and the shaped elastic straightener is placed in a heat treatment furnace. Preferably, the quenching temperature is set to 800-900°C. Annealing treatment can be added as needed, and the annealing temperature is 600-750°C. Keep warm for 1-3 hours and slowly cool to room temperature in the annealing furnace. Finally, according to the needs of different customers, the inside and outside of the straightener are treated by surface shot peening, surface electrophoresis, surface painting, surface spraying, etc., which can not only improve its fatigue resistance and service life, but also form a dense compressive stress layer and protective layer on its surface to improve the corrosion resistance of the product.

[0035] The integral casing elastic centralizer that can be used for drilling equipment manufactured by the above-mentioned internal high pressure forming method is integrally formed, and there are no welds or other independent connecting hooks on the entire integral casing elastic centralizer A, which allows the elastic centralizer spokes 2 to have stronger elasticity and achieve greater deformation without being damaged. The overall structure has high strength and strong elastic recovery force, so it can smoothly pass through the narrowing and bending parts under the drilling, so that the lowered oil pipe can be kept centered in the wellbore and delivered into place.

[0036] The above is based on the present invention as an inspiration. Through the above description, relevant staff can make various changes and modifications without departing from the technical idea of ​​this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. Integral casing elastic centralizer, characterized in that: The invention comprises an upper connecting hoop (1) and a lower connecting hoop (4), wherein the upper connecting hoop (1) and the lower connecting hoop (4) are symmetrically arranged in the upper and lower parts and are connected to each other in the middle through a plurality of elastic straightening spokes (2), wherein the two ends of the elastic straightening spokes (2) are respectively connected to the upper connecting hoop (1) and the lower connecting hoop (4), and the middle part protrudes outwards in an arc shape.

2. The integrated elastic casing centralizer according to claim 1, characterized in that: It comprises at least four elastic straightening spokes (2) which are evenly arranged in a ring shape.

3. A method for processing an integral elastic casing centralizer according to any one of claims 1 to 2, characterized in that: Here are the steps: S1: hot rolled spring steel to obtain seamless steel pipe; S2: Place the seamless steel pipe in a specific mold cavity, inject ultra-high pressure liquid into the sealed seamless steel pipe through special equipment, and apply axial thrust at both ends of the tube blank to make the middle part of the seamless steel pipe bulge outward radially and fit with the mold cavity, forming an arc profile in the middle part of the seamless steel pipe; S3: forming a plurality of hollow portions at the arc-shaped contour, wherein the plurality of hollow portions are spaced apart from each other to form elastic straightening spoke portions between adjacent hollow portions; S4: heat treatment and surface treatment are performed on the integral casing elastic centralizer after the shaping treatment.

4. The processing method of the integral elastic casing centralizer according to claim 3 is characterized in that: After hot rolling, the end surface of the seamless steel pipe is processed to ensure that the end surface of the pipe is flat.

5. The processing method of the integral elastic casing centralizer according to claim 3, characterized in that: The spring steel is 65Mn, 60Si2Mn or 55CrMnA.

6. The processing method of the integral elastic casing centralizer according to claim 3, characterized in that: The ultra-high pressure liquid pressure is 80MPa ~ 200MPa, the axial thrust applied at both ends of the seamless steel pipe is 200 tons ~ 400 tons, and the nominal clamping force is 2000 tons ~ 4000 tons.

7. The processing method of the integral elastic casing centralizer according to claim 3, characterized in that: The heat treatment is quenching treatment, and the quenching temperature is 800-900°C. Annealing treatment can be added as needed, and the annealing temperature is 600-750°C. The heat is kept for 1-3 hours and slowly cooled to room temperature in the annealing furnace.

8. The method for processing an integral elastic casing centralizer according to claim 3, characterized in that: The surface treatment includes surface shot peening, surface electrophoresis, surface painting or surface spraying.

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