High-strength carbon fiber composite heat insulation drill rod applied to corrosive well conditions

Abstract

The invention belongs to the field of petroleum drilling tools, particularly relates to a high-strength carbon fiber composite heat insulation drill rod applied to corrosive well conditions, and aims to solve the problems that a composite drill rod in the prior art is easy to break and not resistant to impact. The inner surface and the outer surface of the base body are each sequentially provided with a heat insulation coating, a carbon fiber material layer and a wear-resistant coating. The production process of the heat insulation coating specifically comprises the steps that the surface of a base body is cleaned and cleaned through a sand blasting process, at least one heat insulation coating is coated, heat preservation is carried out for 80 minutes in the environment of 90 DEG C, and curing is carried out, so that the problems that in the prior art, a composite drill rod is prone to breaking and not resistant to impact are solved; the carbon fiber is applied to production and manufacturing of the petroleum drill rod, under the condition that the overall bearing capacity of the drill rod is not changed, light weight of the drill rod is achieved, meanwhile, corrosion resistance is achieved, and the heat conductivity of a stratum to drilling fluid in the drill rod is reduced.

Description

Technical Field

[0001] The invention belongs to the field of petroleum drilling tools, and in particular relates to a high-strength carbon fiber composite heat-insulating drill pipe used in corrosive well conditions. Background Art

[0002] Oil drill pipe is a key component of oil drilling and production. With the development of deep and ultra-deep wells in recent years, the difficulty of domestic drilling has gradually increased. Manufacturers have developed different types of drill pipe to meet different operating conditions. High-end oil drill pipe, such as sulfur-resistant drill pipe, ultra-high-strength steel-grade drill pipe, and special threaded drill pipe, has been promoted. New non-steel products, such as aluminum alloy drill pipe and titanium alloy drill pipe, have also been tested in drilling. Some oil wells reach depths of approximately 8,000 meters, with some designed for depths of up to 11,100 meters. Bottom-hole temperatures in deep wells can reach 150°C. Commonly used steel drill pipe heat transfer blocks can cause the drilling fluid circulating within the drill pipe to heat up and become ineffective. Furthermore, the weight of the extra-long drill string increases, forcing the upgrading of drilling platforms for ultra-deep well drilling.

[0003] To address the challenges of deep well drilling and reduce drilling platform investment, composite drill pipe has emerged on the market. Some products feature basalt fiber on the outer surface, while others are fully coated with basalt fiber. These products add a layer of basalt fiber to the outer surface of existing steel drill pipe, but the overall weight and thermal conductivity of the steel remain unchanged. Other products utilize a fully carbon fiber body mixed with various fiber types. These new fiber bodies present issues such as breakage and impact resistance during unbundling, stacking at the well site, and handling with pipe grabbers. Summary of the Invention

[0004] In order to solve the problems of easy breakage and poor impact resistance of composite drill pipes in the prior art, the present invention provides a high-strength carbon fiber composite insulation drill pipe for use in corrosive well conditions. The invention comprises a substrate, wherein the inner surface and the outer surface of the substrate are sequentially provided with a heat insulation coating, a carbon fiber material layer and a wear-resistant coating; The production process of the thermal insulation coating specifically includes the following steps: S1. Cleaning and clearing the substrate surface in a predetermined manner; wherein the predetermined manner at least includes a sandblasting process; S2. Apply at least one layer of thermal insulation coating; S3, keeping warm for a set time under a set temperature environment for curing; The thermal insulation coating is an inorganic water-based coating, which includes a synthetic silicate solution, aluminum silicate fibers and hollow glass microspheres; The thermal insulation coating comprises an outer surface thermal insulation coating and an inner surface thermal insulation coating respectively provided on the substrate; the thickness of the outer surface thermal insulation coating and the inner surface thermal insulation coating is not less than 0.2 mm; The carbon fiber material layer includes an outer surface carbon fiber material layer and an inner surface carbon fiber material layer provided on the thermal insulation coating; the thickness of the outer surface carbon fiber material layer and the inner surface carbon fiber material layer is not less than 3 mm; The wear-resistant coating comprises an outer surface wear-resistant coating and an inner surface wear-resistant coating provided on the carbon fiber material layer; the thickness of the outer surface wear-resistant coating and the inner surface wear-resistant coating are both not less than 0.1 mm.

[0005] Furthermore, the base includes a joint and a drill pipe body, and the joint and the drill pipe body are coaxially fixedly connected.

[0006] Furthermore, an inner surface and an outer surface of the joint close to one end of the drill pipe body are provided with an inclined groove, and the inclined direction of the inclined groove is inclined at 45 degrees relative to the axial direction of the joint.

[0007] Furthermore, a rectangular opening groove is provided on the drill pipe body, and the rectangular opening groove is tilted, and the axial direction of the rectangular opening groove is tilted 45 degrees relative to the axial direction of the pipe body.

[0008] Furthermore, two adjacent rectangular opening slots are arranged at intervals.

[0009] Furthermore, it also includes a cylindrical structure, which is coaxially fixed on the outside of the tube body and has a diameter greater than the diameter of the tube body.

[0010] Furthermore, the thickness of the outer surface thermal insulation coating and the inner surface thermal insulation coating is 3mm-10mm.

[0011] Furthermore, the thickness of the outer surface wear-resistant coating and the inner surface wear-resistant coating is 0.2mm-0.3mm.

[0012] Beneficial effects of the present invention: This technology has enabled the application of carbon fiber in the production of oil drill pipes. While maintaining the overall load-bearing capacity of the drill pipe, the drill pipe is lightweight and corrosion-resistant, reducing the thermal conductivity of the formation to the drilling fluid within the drill pipe. The steel matrix can withstand bending caused by pipe grabber handling and pipe stacking at the drilling site, allowing the same drilling rig to achieve increased drilling depth. This provides a solution for small-tonnage drilling rigs drilling deep wells and also provides a solution for drilling tools used in high-temperature formations and corrosive environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Other features, objects and advantages of the present application will become more apparent upon reading the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 is a schematic diagram of the hierarchical structure of some embodiments of the present application; Figure 2 It is a schematic diagram of the external structure of some embodiments of the present application.

[0014] In the figure: 1. Carbon fiber material layer on the outer surface; 2. Inclined groove; 3. Wear-resistant coating on the outer surface; 4. Pipe body; 5. Thermal insulation coating on the outer surface; 6. Thermal insulation coating on the inner surface; 7. Carbon fiber material layer on the inner surface; 8. Wear-resistant coating on the inner surface; 9. Cylindrical structure; 10. Joint; 11. Drill pipe weld; 12. Rectangular open groove. DETAILED DESCRIPTION

[0015] The present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are intended only to illustrate the relevant invention and are not intended to limit the invention. It should also be noted that, for ease of description, only portions relevant to the relevant invention are shown in the accompanying drawings.

[0016] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0017] like Figure 1-2 As shown, the present invention provides a high-strength carbon fiber composite insulation drill pipe for use in corrosive well conditions, comprising a substrate, wherein the inner and outer surfaces of the substrate are sequentially provided with a heat insulation coating, a carbon fiber material layer, and a wear-resistant coating; The production process of the thermal insulation coating specifically includes the following steps: S1. Cleaning and clearing the substrate surface in a predetermined manner; wherein the predetermined manner at least includes a sandblasting process; S2. Apply at least one layer of thermal insulation coating; S3. Keep warm for a set time under a set temperature environment for curing, wherein the set temperature is 90° C. and the set time is 80 minutes.

[0018] In practice, the high strength of carbon fiber is utilized to achieve high overall load-bearing capacity while reducing the overall weight of the drill pipe. A thermal insulation coating applied to the inner and outer metal surfaces of the drill pipe reduces the pipe's thermal conductivity, slowing the temperature rise of the drilling fluid inside the pipe and preventing premature failure of the drilling fluid during deep well drilling. A wear-resistant coating applied to the inner and outer carbon fiber surfaces of the drill pipe slows wear of the carbon fiber, extending the service life of the drill pipe. This overall approach achieves a reduction in weight without reducing the drill pipe's load-bearing capacity, thereby extending the drilling depth of existing drilling rigs.

[0019] The thermal insulation coating is an inorganic water-based coating made from a synthetic silicate solution, aluminum silicate fibers, and hollow glass microspheres. Its primary function is to slow heat conduction. Its thickness ranges from 0.3 to 0.5 mm. The production process involves sandblasting the substrate surface, applying a layer of thermal insulation coating, and then curing it at 90°C for 80 minutes. This process produces a thermal insulation coating that meets the requirements.

[0020] In some embodiments, the base body includes a joint 10 and a drill pipe body 4, and the joint 10 and the drill pipe body 4 are coaxially fixedly connected.

[0021] In specific implementation, the joint 10 and the drill pipe body 4 are welded together by friction pressing as the base, and the drill pipe weld 11 is the boundary between the joint 10 and the drill pipe body 4. A layer of thermal insulation coating is applied starting from the slope of the outer surface of the joint (and the corresponding inner surface), and then a layer of carbon fiber material is processed and coated on the inner and outer surfaces, and finally a layer of wear-resistant coating is applied on the inner and outer surfaces.

[0022] In some embodiments, an inner surface and an outer surface of the joint 10 near one end of the drill pipe body 4 are provided with an inclined groove 2 , and the inclined direction of the inclined groove 2 is inclined at 45° relative to the axial direction of the joint 10 .

[0023] In specific implementation, the joint 10 is a steel joint, and the threaded connection end adopts a standard structure to facilitate interchangeability with existing products. The weld neck end at the other end adopts an extended and reduced diameter structure. The outer surface of the joint near the weld area is processed with a 45° distributed bevel groove for connecting carbon fiber. After the reduced diameter structure is coated with carbon fiber, the outer diameter of the joint at this point is consistent with the outer diameter of the final tube body.

[0024] In some embodiments, a rectangular opening slot 12 is provided on the drill pipe body 4 . The rectangular opening slot 12 is tilted, and the axial direction of the rectangular opening slot 12 is tilted 45° relative to the axial direction of the pipe body 4 .

[0025] In some embodiments, two adjacent rectangular opening slots 12 are spaced apart.

[0026] In specific implementation, the steel drill pipe body 4 adopts rectangular opening grooves 12 with a 45° direction in the wall thickness area of the pipe body 4. The size of a single opening groove is 40x20mm. The grooves are arranged in parallel, and their center points are also arranged at a spacing of 40x20mm.

[0027] In some embodiments, a cylindrical structure 9 is further included. The cylindrical structure 9 is coaxially fixed to the outside of the tube body 4 . The diameter of the cylindrical structure 9 is larger than the diameter of the tube body 4 .

[0028] In specific implementation, the drill pipe body 4 is a steel pipe body, and two cylindrical structures 9 are provided on the outer surface of the pipe body 4. The outer diameter of the structure is 10-20 mm larger than the diameter of the pipe body, and the length is about 300 mm. The position is 1 / 4 of the distance from each end. This structure plays a role in strengthening the connection strength between the carbon fiber and the drill pipe body.

[0029] In some embodiments, the thermal insulation coating comprises an outer surface thermal insulation coating 5 and an inner surface thermal insulation coating 6 respectively disposed on the substrate; The carbon fiber material layer includes an outer surface carbon fiber material layer 1 and an inner surface carbon fiber material layer 7 provided on the thermal insulation coating; The wear-resistant coating comprises an outer surface wear-resistant coating 3 and an inner surface wear-resistant coating 8 provided on the carbon fiber material layer.

[0030] In some embodiments, the thickness of the outer surface thermal insulation coating 5 and the inner surface thermal insulation coating 6 are both not less than 0.2 mm.

[0031] In specific implementation, the outer surface thermal insulation coating 5 and the inner surface thermal insulation coating 6 have the main function of slowing down heat conduction, and the thickness is 0.3-0.5 mm.

[0032] In some embodiments, the drill pipe body 4 can achieve strengths reaching S135 and V150 steel grades. It is manufactured from seamless steel pipes with chemical compositions such as 0.22-0.26% C, 0.45-0.52% Mn, 1.00-1.1% Cr, and 0.68-0.75% Mo. The pipes are end-thickened, quenched at 860-900°C for 50-55 minutes, and then quenched in an internal spray-and-external quenching machine using a water-based quenching fluid with a concentration of 15%-20%. The pipes are tempered at 600-620°C for 80-90 minutes. The yield strength reaches 1000 MPa, and the impact toughness (tested at -20°C, 7.5x10mm size) is 85-110 J.

[0033] In some embodiments, the carbon fiber used is an advanced composite material made of carbon fiber and resin, etc. Its specific strength and specific modulus are relatively high among existing engineering materials. It is selected from materials such as T700 and T800. Its two-dimensional plane weaving structure is twill and is arranged at a 45° angle. The thickness of the outer surface carbon fiber material layer 1 and the inner surface carbon fiber material layer 7 are both not less than 3mm. In specific implementation, the thickness of the inner and outer layers is both 5-10mm.

[0034] The outer surface carbon fiber material layer 1 and the inner surface carbon fiber material layer 7 are first prepared by a wet winding molding process on the outer surface of the drill pipe body 4, using fiber filaments impregnated with liquid resin, and then tightened and pressurized by a mold in the area of the weld bevel near the outer surface of the joints at both ends, and then cured together by an oven molding process.

[0035] After the outer surface is produced, the inner surface of the drill pipe is prepared by resin transfer molding process, and then the inner surface of the joints at both ends near the weld bevel area is tightened and pressurized by mold, and then the oven molding process is carried out together to cure.

[0036] In some embodiments, the wear-resistant coating used is an epoxy phenolic resin coating, which has a good molecular structure and can be wear-resistant and effectively resist corrosion of the drill pipe by corrosive ions.

[0037] The wear-resistant coating used in the present invention is model TK34P, developed by our company, and has been successfully applied to existing drill pipe products. The thickness of the outer surface wear-resistant coating 3 and the inner surface wear-resistant coating 8 are not less than 0.1mm. In specific implementation, the thickness of the inner and outer layers is 0.2-0.3mm.

[0038] The wear-resistant coating used in the present invention is produced by sandblasting the substrate surface, spraying a red primer (a mixture primarily composed of phenolic resin) and then curing the mixture by holding the mixture at 190°C for 100 minutes. Subsequently, the wear-resistant coating is sprayed on the surface and then cured by holding the mixture at 220°C for 120 minutes. This process produces a wear-resistant coating that meets the requirements.

[0039] In the description of the present invention, terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. These are intended solely for ease of description and are not intended to indicate or imply that the device or component described must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not intended to indicate or imply relative importance.

[0040] Furthermore, it should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0041] The term "comprise" or any other similar term is intended to cover non-exclusive inclusion such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0042] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

Claims

1. A high-strength carbon fiber composite insulated drill pipe for use in corrosive well conditions, characterized in that: The invention comprises a substrate, wherein the inner surface and the outer surface of the substrate are sequentially provided with a heat insulation coating, a carbon fiber material layer and a wear-resistant coating; The production process of the thermal insulation coating specifically includes the following steps: S1. Cleaning and clearing the substrate surface in a predetermined manner; wherein the predetermined manner at least includes a sandblasting process; S2. Apply at least one layer of thermal insulation coating; S3, keeping warm for a set time under a set temperature environment for curing; The thermal insulation coating is an inorganic water-based coating, which includes a synthetic silicate solution, aluminum silicate fibers and hollow glass microspheres; The thermal insulation coating comprises an outer surface thermal insulation coating and an inner surface thermal insulation coating respectively provided on the substrate; the thickness of the outer surface thermal insulation coating and the inner surface thermal insulation coating is not less than 0.2 mm; The carbon fiber material layer includes an outer surface carbon fiber material layer and an inner surface carbon fiber material layer provided on the thermal insulation coating; the thickness of the outer surface carbon fiber material layer and the inner surface carbon fiber material layer is not less than 3 mm; The wear-resistant coating includes an outer surface wear-resistant coating and an inner surface wear-resistant coating provided on the carbon fiber material layer; the thickness of the outer surface wear-resistant coating and the inner surface wear-resistant coating are both not less than 0.1 mm.

2. The high-strength carbon fiber composite insulated drill pipe for use in corrosive well conditions according to claim 1, characterized in that: The base comprises a joint and a drill pipe body, and the joint and the drill pipe body are coaxially fixedly connected.

3. The high-strength carbon fiber composite insulated drill pipe for use in corrosive well conditions according to claim 2, characterized in that: The inner surface and outer surface of the joint close to one end of the drill pipe body are provided with inclined grooves, and the inclined direction of the inclined grooves is inclined at 45 degrees relative to the axial direction of the joint.

4. The high-strength carbon fiber composite insulated drill pipe for use in corrosive well conditions according to claim 2, characterized in that: A rectangular opening slot is provided on the drill pipe body. The rectangular opening slot is tilted, and the axial direction of the rectangular opening slot is tilted 45 degrees relative to the axial direction of the pipe body.

5. The high-strength carbon fiber composite insulated drill pipe for use in corrosive well conditions according to claim 4, characterized in that: Two adjacent rectangular opening slots are arranged at intervals.

6. The high-strength carbon fiber composite insulated drill pipe for use in corrosive well conditions according to claim 2, characterized in that: It also includes a cylindrical structure, which is coaxially fixed on the outside of the tube body. The diameter of the cylindrical structure is larger than the diameter of the tube body.

7. The high-strength carbon fiber composite insulated drill pipe for use in corrosive well conditions according to claim 1, characterized in that: The thickness of the outer surface heat insulation coating and the inner surface heat insulation coating is 3mm-10mm.

8. The high-strength carbon fiber composite insulated drill pipe for use in corrosive well conditions according to claim 1, characterized in that: The thickness of the outer surface wear-resistant coating and the inner surface wear-resistant coating is 0.2mm-0.3mm.

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