Integral rigid centralizer and manufacturing method thereof

Abstract

The manufacturing method of the integrated rigid centralizer comprises the steps that S1, steel is subjected to hot rolling to obtain a seamless steel pipe; s2, the seamless steel pipe locally protrudes outwards in the radial direction to deform through internal high-pressure forming, a plurality of spiral centralizing edges are formed on the surface of the seamless steel pipe, and the multiple centralizing edges are arranged on the outer surface of the seamless steel pipe in a surrounding mode; s3, carburizing, quenching and tempering the seamless steel tube with the centralizing edges obtained in the step S2; according to the integrated rigid centralizer, centralizing edges are spiral, the multiple centralizing edges are attached to the outer surface of a cylinder in a surrounding mode and are integrally connected with the cylinder, and smooth arc-shaped transition sections are integrally connected between the cylinder and the centralizing edges. According to the manufacturing method, the integral rigid centralizer without a welding seam or other connecting structures can be manufactured in an internal high-pressure forming mode, and the integral rigid centralizer can smoothly pass through a narrowed part and a bent part of an oil well; the centralizer has the advantages of being high in rigidity, uniform in thickness, high in precision, free of excessive stress concentration, excellent in structural performance, not prone to damage, long in service life and the like.

Description

Technical Field

[0001] The invention relates to the technical field of well cementing in oil and gas fields during drilling, and in particular to an integral rigid centralizer and a manufacturing method thereof. Background Art

[0002] At present, the depth of domestic drilling is getting deeper and deeper. In order to ensure that the downhole tools can work in the center when going down the well, casing is needed. 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 oil pipe is as centered as possible during operation.

[0003] The existing centralizers for oil pipes, which are used to support the centralizer structure between the oil pipe and the inner wall of the well, are usually directly welded to the oil pipe, which has a large volume and poor structural performance. When the inner wall of the well is uneven and has narrowed or curved parts, it will be very difficult for the centralizer to pass, often causing the oil pipe to get stuck in the well. At present, when encountering such a situation, the operator can only press down the oil pipe more forcefully, which may cause stress concentration, premature detachment and damage of the welded centralizer on the oil pipe, or other unexpected dangerous situations.

[0004] The Chinese invention patent with the announcement number CN220487519U and the announcement date of February 13, 2024, discloses a hinged rigid centralizer. The rigid centralizer is divided into two parts, and multiple centralizing ribs are installed on the outer surface. A hinge is installed at the joint on one side of the separated rigid centralizer body, and the other side is fixed with bolts to be sleeved on the oil pipe. This design facilitates the installation of the rigid centralizer, but in actual use, it may cause the hinge to break, thereby losing the function of maintaining the oil pipe in the center.

[0005] The Chinese invention patent with the announcement number CN215761550U and the announcement date of February 8, 2022 discloses a casing rigid centralizer. The casing rigid centralizer is provided with a plurality of straight straightening edges and rotating straightening edges on the cylinder, and a roller assembly is also provided on the straightening edges. This design converts sliding friction into rolling friction when working in the well, reducing the resistance to entering the well. However, the use of the casing rigid centralizer has high requirements on the inner wall of the well and the use conditions are relatively harsh.

[0006] The Chinese invention patent with announcement number CN215761550U and announcement date October 22, 2021, discloses a spiral rigid centralizer. The spiral rigid centralizer consists of a centralizer body and two anti-collision mechanisms connected by upper and lower threads, and is equipped with two welding blocks and two fixing bolts to lock the position of the casing. This design can well solve the problem of insufficient casing centering and inability to adjust, but there are too many parts for connection, and the stress is relatively concentrated, resulting in a decrease in overall rigidity, which is easy to be damaged and fail in harsh or complex environments. Summary of the invention

[0007] In view of the shortcomings of the existing centralizers described in the background technology, the present invention provides an integral rigid centralizer and a method for manufacturing the same. The integral rigid centralizer can smoothly pass through the narrowed part and the curved part of the oil well, and has the advantages of strong rigidity, uniform thickness, high precision, no excessive stress concentration, excellent structural performance, the centralizing structure is not prone to damage and has a long service life.

[0008] A method for manufacturing an integral rigid centralizer is disclosed, comprising the following steps:

[0009] S1. hot rolling the steel to obtain a seamless steel pipe;

[0010] S2. The seamless steel tube is partially deformed by convexly protruding radially outwardly through internal high pressure forming to form a plurality of spiral straightening edges on its surface, and a plurality of straightening edges of the same width are arranged around the outer surface of the seamless steel tube;

[0011] S3. The seamless steel pipe with the straightening edge obtained in step S2 is subjected to carburizing, quenching and tempering after being shaped.

[0012] Preferably, in step S1, the steel material is 42CrMo steel or 30CrNi2MoV steel to improve the structural strength and wear resistance of the integral rigid centralizer. In this embodiment, 42CrMo steel is specifically used, and its minimum tensile strength is about 850MPa and the minimum impact absorption energy is about 63J. The integral rigid centralizer made of this material can have good wear resistance and mechanical properties.

[0013] Preferably, in step S2, the internal high pressure forming includes the following steps: after finishing the flatness of the seamless steel pipe, put it into the lower contour limiting mold of the internal high pressure forming machine, and after the upper contour limiting mold is also closed, inject high pressure liquid into the seamless steel pipe and seal both ends, clamp the two ends of the seamless steel pipe with a clamp, and gradually increase the pressure of the high pressure liquid inside the seamless steel pipe, while applying inward pressure to both ends of the seamless steel pipe through the clamp until the seamless steel pipe partially protrudes radially outward to match the shape of the lower contour limiting mold and the upper contour limiting mold, so as to form a spiral straightening edge on the surface of the seamless steel pipe, so that an integral rigid straightener can be formed in one piece, which has strong rigidity and good structure. The structural performance is excellent, there is no weld or other connection structure, the thickness is uniform everywhere, there is no excessive stress concentration, and the straightening structure is not easy to be damaged; and there is no problem of excessive stress concentration in the manufacturing process, which can allow the straightening edge to expand further outward to achieve adaptation to larger well diameters; the use of internal high pressure forming saves more materials and has higher production efficiency than casting. During the forming process, there is no need to preheat the seamless steel pipe, and the forming can be completed at room temperature. The material properties will not change due to heating, so that high-precision dimensional control can be achieved during forming, avoiding the thermal expansion and contraction problems caused by preheating treatment, and making the obtained integral rigid straightening device higher in precision.

[0014] Preferably, in step S3, the seamless steel pipe with the straightening edge is placed in a carburizing furnace heated to 900-950 degrees Celsius, and a carbon-containing gas is introduced into the carburizing furnace and maintained for 3-5 hours to form a high-carbon surface layer. In this embodiment, a mixed carbon-containing gas of one or more of methane, ethane, propane and carbon monoxide can be used; the seamless steel pipe with the straightening edge is cooled to 800-850 degrees Celsius in the carburizing furnace, taken out of the furnace and placed in oil for quenching, then heated to 180-220 degrees Celsius and slowly cooled to room temperature for tempering; through the carburizing, quenching and tempering treatment, the hardness and wear resistance of the surface of the integral rigid straightener can be significantly improved, while maintaining the internal toughness and strength.

[0015] An integral rigid centralizer is disclosed, which is manufactured by the above method and comprises a cylinder and a righting edge, wherein the righting edge is spiral, and a plurality of righting edges are attached around the outer surface of the cylinder and are respectively connected to the cylinder as a whole; the spiral righting edges enable the integral rigid centralizer to smoothly pass through narrow and curved parts in the well, thereby preventing the centralizer from getting stuck in the well and ensuring that the oil pipe can remain centered and smoothly move into place when being lowered into the well; and the plurality of spiral righting edges arranged in this way can provide the integral rigid centralizer with a maximum lateral force for supporting it on the inner wall of the well; in this embodiment, four spiral righting edges of the same size and uniformly arranged around a circle are formed on the cylinder formed by a single seamless steel pipe, and the four righting edges are spaced apart from each other in the circumferential direction of the outer surface of the cylinder, and the difference between adjacent righting edges is 90°.

[0016] Furthermore, a smooth arc-shaped transition section is integrally connected between the surface of the cylinder and the edge of the straightening edge. The structural design of the arc-shaped transition section can not only improve the formability of internal high-pressure forming, but also further avoid the generation of large stress concentration in the integral rigid straightening device during operation.

[0017] Through the above technical solution, the present invention at least includes the following beneficial effects:

[0018] The manufacturing method described in the present application can produce an integral rigid stabilizer without welds or other connecting structures through internal high pressure forming, and there is no problem of excessive stress concentration in the manufacturing process, allowing the straightening edge to expand further outward to achieve adaptation to larger wellbore diameters; the internal high pressure forming method saves more materials and has higher production efficiency than casting. During the forming process, there is no need to preheat the seamless steel pipe, and the forming can be completed at room temperature. The material properties will not change due to heating, so that high-precision dimensional control can be achieved during forming, avoiding the thermal expansion and contraction problems caused by preheating treatment.

[0019] The integral rigid centralizer thus obtained by means of internal high pressure forming has an integral structure with strong overall rigidity, a more uniform curvature of the connection between the cylinder surface and the edge of the centralizer, a higher precision, and no excessive stress concentration. The structural performance is excellent, and the centralizing structure is not easily damaged. After surface carburizing and heat treatment, the mechanical properties and wear resistance are good, and the service life is long. Since it has a spiral centralizing edge, it can smoothly pass through the narrow and curved parts in the well, avoiding the centralizer from getting stuck in the well, and ensuring that the oil pipe can remain centered and move smoothly into place when lowering into the well. A plurality of surrounding centralizing edges can provide the integral rigid centralizer with the maximum lateral force for its support on the inner wall of the well. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be described in more detail below with reference to the accompanying drawings, in which:

[0021] Figure 1 A three-dimensional view of the integral rigid centralizer described in the embodiment of the present application;

[0022] Figure 2 It is a front view of the integral rigid centralizer described in the embodiment of the present application;

[0023] Figure 3 It is a cross-sectional view of the integral rigid centralizer described in the embodiment of the present application. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. These drawings are all simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the structures related to the present invention.

[0025] In the description of this application, it should be understood that if the terms "upper", "lower", "left", "right", "front", "back", etc. indicate directions or positional relationships, they are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship are only used for illustrative purposes and cannot be understood as limitations on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0026] 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 an indirect connection through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] A method for manufacturing an integral rigid centralizer comprises the following steps:

[0028] S1. Hot-rolling a steel material to obtain a seamless steel pipe, wherein the steel material is selected from 42CrMo steel or 30CrNi2MoV steel to improve the structural strength and wear resistance of the integral rigid centralizer. In this embodiment, 42CrMo steel is specifically used, and its minimum tensile strength is 850MPa and the minimum impact absorption energy is 63J. The integral rigid centralizer made of this material can have good wear resistance and mechanical properties.

[0029] S2. The seamless steel tube is partially deformed by convexly protruding radially outward through internal high pressure forming to form a plurality of spiral straightening edges 2 on its surface, and a plurality of straightening edges 2 of the same width are arranged around the outer surface of the seamless steel tube;

[0030] The internal high-pressure forming of the straightening edge 2 is specifically achieved in the following manner: after the flatness of the seamless steel pipe is finely processed, it is placed in the lower contour limiting mold of the internal high-pressure forming machine; after the upper contour limiting mold is also closed, high-pressure liquid is injected into the seamless steel pipe and both ends are sealed; the two ends of the seamless steel pipe are clamped with a clamp, and the pressure of the high-pressure liquid inside the seamless steel pipe is gradually increased; at the same time, inward pressure is applied to both ends of the seamless steel pipe through the clamp until the seamless steel pipe partially protrudes radially outward and matches the shape of the lower contour limiting mold and the upper contour limiting mold, so as to form a spiral straightening edge 2 on the surface of the seamless steel pipe, so that an integral rigid straightener can be formed in one piece, which has strong rigidity and structure. It has excellent performance, no welds or other connecting structures, uniform thickness everywhere, no excessive stress concentration, and the straightening structure is not easily damaged; and there is no problem of excessive stress concentration in the manufacturing process, which can allow the straightening edge 2 to expand further outward to achieve adaptation to larger wellbore diameters; the use of internal high-pressure forming saves materials and has higher production efficiency than casting. During the forming process, there is no need to preheat the seamless steel pipe, and the forming can be completed at room temperature. The material properties will not change due to heating, so that high-precision dimensional control can be achieved during forming, avoiding the thermal expansion and contraction problems caused by preheating treatment, and making the obtained integral rigid straightener more accurate.

[0031] S3. After the seamless steel pipe with the straightening edge 2 obtained in step S2 is shaped, it is carburized, quenched and tempered; specifically, the seamless steel pipe with the straightening edge 2 is placed in a carburizing furnace heated to 900-950 degrees Celsius, and a carbon-containing gas is introduced into the carburizing furnace and maintained for 3-5 hours to form a high-carbon surface layer. In this embodiment, a mixed carbon-containing gas of one or more of methane, ethane, propane and carbon monoxide can be used; the seamless steel pipe with the straightening edge 2 is cooled to 800-850 degrees Celsius in the carburizing furnace, taken out of the furnace and placed in oil for quenching, then heated to 180-220 degrees Celsius and slowly cooled to room temperature for tempering; through the carburizing, quenching and tempering treatment, the hardness and wear resistance of the surface of the integral rigid straightener can be significantly improved, while maintaining the toughness and strength of the interior.

[0032] A feasible carburizing furnace temperature is 900 degrees Celsius, carbon-containing gas is introduced and maintained for 5 hours, the quenching temperature is 850 degrees Celsius, and the tempering temperature is 220 degrees Celsius; another feasible carburizing furnace temperature is 950 degrees Celsius, carbon-containing gas is introduced and maintained for 3 hours, the quenching temperature is 800 degrees Celsius, and the tempering temperature is 180 degrees Celsius; the optimal carburizing furnace temperature is 925 degrees Celsius, carbon-containing gas is introduced and maintained for 4 hours, the quenching temperature is 825 degrees Celsius, and the tempering temperature is 200 degrees Celsius.

[0033] The integral rigid centralizer prepared by the above method is referred to Figures 1 to 3, which comprises a barrel 1, a straightening edge 2 and an arc-shaped transition section 3, wherein the straightening edge 2 is spiral, and a plurality of straightening edges 2 are attached around the outer surface of the barrel 1 and are respectively connected to the barrel 1 as a whole; the spiral straightening edges 2 enable the integral rigid centralizer to smoothly pass through the narrow part and the curved part in the well, avoid the centralizer from being stuck in the well, and ensure that the oil pipe can remain centered and smoothly move into place when it is lowered into the well; and the plurality of spiral straightening edges 2 arranged in this way can provide the integral rigid centralizer with the maximum lateral force for supporting it on the inner wall of the well; in this embodiment, four spiral straightening edges 2 of the same size and uniformly arranged around a circle are formed on the barrel 1 formed by a single seamless steel pipe, and the four straightening edges 2 are spaced apart from each other in the circumferential direction of the outer surface of the barrel 1, and the difference between adjacent straightening edges 2 is 90°.

[0034] A smooth arc-shaped transition section 3 is integrally connected between the surface of the cylinder 1 and the edge of the straightening edge 2. The structural design of the arc-shaped transition section 3 can not only improve the formability of internal high-pressure forming, but also further avoid the generation of large stress concentration in the integral rigid straightening device during operation.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Based on the present invention and the above description, relevant personnel can make various changes and modifications without departing from the technical idea of ​​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 method for manufacturing an integral rigid centralizer, characterized in that: The following steps are involved: S1. hot rolling the steel to obtain a seamless steel pipe; S2. The seamless steel tube is partially deformed by convexly convexly outwardly from the radial direction by means of internal high pressure forming, and a plurality of spiral straightening edges (2) are formed on its surface, and the plurality of straightening edges (2) are arranged around the outer surface of the seamless steel tube; S3. Carburizing, quenching and tempering the seamless steel pipe with the straightening edge (2) obtained in step S2.

2. The method for manufacturing an integral rigid centralizer according to claim 1, characterized in that: In step S1, the steel material is 42CrMo steel or 30CrNi2MoV steel.

3. The method for manufacturing an integral rigid centralizer according to claim 1, characterized in that: In step S2, the internal high pressure forming includes the following steps: placing the seamless steel pipe into the lower contour limiting mold of the internal high pressure forming machine, and after the upper contour limiting mold is also closed, injecting high pressure liquid into the seamless steel pipe and sealing both ends, clamping the two ends of the seamless steel pipe with a clamp, gradually increasing the pressure of the high pressure liquid inside the seamless steel pipe, and applying inward pressure to both ends of the seamless steel pipe through the clamp until the seamless steel pipe partially protrudes radially outward to match the shape of the lower contour limiting mold and the upper contour limiting mold.

4. The method for manufacturing an integral rigid centralizer according to claim 1, characterized in that: In step S3, the seamless steel pipe with the straightening edge (2) is placed in a carburizing furnace heated to 900-950 degrees Celsius, and a carbon-containing gas is introduced into the carburizing furnace and maintained for 3-5 hours to form a high-carbon surface layer; the seamless steel pipe with the straightening edge (2) is cooled to 800-850 degrees Celsius in the carburizing furnace, taken out of the furnace and placed in oil to complete quenching, then heated to 180-220 degrees Celsius and slowly cooled to room temperature to complete tempering.

5. An integral rigid centralizer, characterized in that: It is manufactured by the method of any one of claims 1 to 4, comprising a cylinder (1) and a righting edge (2), wherein the righting edge (2) is spiral-shaped, and a plurality of righting edges (2) are attached around the outer surface of the cylinder (1) and are respectively connected to the cylinder (1) as a whole.

6. An integral rigid centralizer according to claim 5, characterized in that: A smooth arc-shaped transition section (3) is integrally connected between the surface of the cylinder (1) and the edge of the straightening edge (2).

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