High-strength carbon fiber composite heat-insulated drill pipe applied to corrosive well conditions

Abstract

This invention belongs to the field of oil drilling tools, specifically relating to a high-strength carbon fiber composite heat-insulating drill pipe for use in corrosive well conditions. It aims to solve the problems of easy breakage and poor impact resistance in existing composite material drill pipes. The invention includes a matrix, with a heat-insulating coating, a carbon fiber material layer, and a wear-resistant coating sequentially disposed on both the inner and outer surfaces of the matrix. The production process of the heat-insulating coating specifically includes cleaning the matrix surface using a sandblasting process, applying at least one layer of the heat-insulating coating, and curing it at 90°C for 80 minutes. This solves the problems of easy breakage and poor impact resistance in existing composite material drill pipes, enabling the application of carbon fiber in the manufacturing of oil drill pipes. While maintaining the overall load-bearing capacity of the drill pipe, it achieves lightweighting, corrosion resistance, and reduces the thermal conductivity of the formation to the drilling fluid inside the drill pipe.

Description

Technical Field

[0001] This invention belongs to the field of oil drilling tools, and specifically relates to a high-strength carbon fiber composite heat-insulating drill pipe for use in corrosive well conditions. Background Technology

[0002] Oil drill pipes belong to the oil drilling and production field. With the development of deep and ultra-deep wells in recent years, the difficulty of drilling and development in China has been gradually increasing. Manufacturers have developed different types of drill pipes for different working conditions. High-end oil drill pipes such as sulfur-resistant drill pipes, ultra-high strength steel-grade drill pipes, and special threaded drill pipes have been promoted, and new non-steel products such as aluminum alloy drill pipes and titanium alloy drill pipes have also undergone drilling tests. Some oil wells have reached depths of about 8,000 meters, and some wells have been designed to reach depths of 11,100 meters. The bottom temperature of deep wells can reach 150°C. The heat-conducting blocks of commonly used steel drill pipes cause the drilling fluid circulating inside the drill pipe to heat up and become ineffective. At the same time, the weight of ultra-long drill strings is also increasing, 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 pipes have emerged in the market. Some drill pipes have an outer surface made of basalt fiber, while others are smart drill pipes with an entire outer surface coated with basalt fiber. These products add a layer of basalt fiber to the outer surface of existing steel drill pipes, but the overall weight of the drill pipe remains largely unchanged, and the thermal conductivity of the steel drill pipe is also unaffected. Some drill pipes are made entirely of carbon fiber mixed with different types of fibers. However, these new fibers present problems such as easy breakage and poor impact resistance during uncoupling, well site stacking, and handling by pipe grippers. Summary of the Invention

[0004] To address the problems of easy breakage and poor impact resistance in existing composite material drill pipes, this invention provides a high-strength carbon fiber composite heat-insulating drill pipe suitable for corrosive well conditions. The substrate includes a heat-insulating coating, a carbon fiber material layer, and a wear-resistant coating, which are sequentially disposed on both the inner and outer surfaces of the substrate. The production process of the heat-insulating coating specifically includes the following steps: S1. The substrate surface is cleaned and treated using a pre-defined method; wherein the pre-defined method includes at least a sandblasting process. S2. Apply at least one layer of heat-insulating coating; S3. Incubate at a set temperature for a set time for curing; The heat-insulating coating is an inorganic water-based coating, which includes a synthetic silicate solution, aluminum silicate fiber, and hollow glass microspheres. The heat insulation coating includes an outer surface heat insulation coating and an inner surface heat insulation coating respectively disposed on the substrate; the thickness of both the outer surface heat insulation coating and the inner surface heat 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 disposed on the heat insulation coating; the thickness of both 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 disposed on the carbon fiber material layer; the thickness of both the outer surface wear-resistant coating and the inner surface wear-resistant coating is not less than 0.1 mm.

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

[0006] Furthermore, the inner and outer surfaces of the joint near one end of the drill pipe body are provided with inclined grooves, and the inclined grooves are inclined at 45° relative to the axial direction of the joint.

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

[0008] Furthermore, the two adjacent rectangular opening slots are spaced apart.

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

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

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

[0012] The beneficial effects of this invention are: This technology enables the application of carbon fiber in the manufacturing of oil drill pipes, achieving weight reduction without altering the overall load-bearing capacity. It also provides corrosion resistance, reduces the thermal conductivity of the formation to the drilling fluid inside the drill pipe, and the steel matrix can withstand bending during handling and stacking at the drilling site. This allows for increased drilling depth using the same drilling rig. It provides a solution for drilling deep wells with small-tonnage rigs and for drilling tools used in high-temperature formations and corrosive environments. Attached Figure Description

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

[0014] In the figure: 1. Outer surface carbon fiber material layer; 2. Inclined groove; 3. Outer surface wear-resistant coating; 4. Pipe body; 5. Outer surface heat insulation coating; 6. Inner surface heat insulation coating; 7. Inner surface carbon fiber material layer; 8. Inner surface wear-resistant coating; 9. Cylindrical structure; 10. Joint; 11. Drill rod weld; 12. Rectangular opening groove. Detailed Implementation

[0015] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0016] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0017] like Figure 1-2 As shown, the present invention provides a high-strength carbon fiber composite heat-insulating drill pipe for use in corrosive well conditions, comprising a matrix, wherein a heat-insulating coating, a carbon fiber material layer and a wear-resistant coating are sequentially disposed on the inner and outer surfaces of the matrix. The production process of the heat-insulating coating specifically includes the following steps: S1. The substrate surface is cleaned and treated using a pre-defined method; wherein the pre-defined method includes at least a sandblasting process. S2. Apply at least one layer of heat-insulating coating; S3. Incubate at a set temperature for a set time for curing, wherein the set temperature is 90℃ 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 of the drill pipe while reducing its overall weight. A heat-insulating coating on the inner and outer metal surfaces of the drill pipe reduces its thermal conductivity, slowing down the rate of temperature rise of the drilling fluid inside and preventing premature failure of the drilling fluid in deep wells. A wear-resistant coating on the inner and outer carbon fiber surfaces slows down carbon fiber wear, increasing the drill pipe's service life. This approach achieves a reduction in drill pipe weight without compromising load-bearing capacity, thereby extending the drilling depth of existing drilling rigs.

[0019] The heat-insulating coating is an inorganic water-based paint, made from a synthetic silicate solution, aluminum silicate fibers, and hollow glass microspheres. Its main function is to slow down heat conduction. The thickness is 0.3-0.5 mm. The production process involves cleaning the substrate surface using sandblasting, applying a layer of the heat-insulating coating, and then curing it at 90℃ for 80 minutes. This process yields a heat-insulating coating that meets the requirements.

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

[0021] In practice, the joint 10 and the drill pipe body 4 are welded together by friction pressing as the base. The drill pipe weld 11 is the boundary between the joint 10 and the drill pipe body 4. A heat insulation coating is applied starting from the slope of the outer surface of the joint (and the corresponding inner surface). Then, a layer of carbon fiber material is applied to the inner and outer surfaces. Finally, a wear-resistant coating is applied to the inner and outer surfaces.

[0022] In some embodiments, the inner and outer surfaces of the connector 10 near the drill pipe body 4 are provided with inclined grooves 2, and the inclined direction of the inclined grooves 2 is inclined at 45° relative to the axial direction of the connector 10.

[0023] In practice, joint 10 is a steel joint. The threaded connection end adopts a standard structure, which is convenient for interchange with existing products. The weld neck end of the other end adopts an extended and variable diameter structure. The inner and outer surfaces of the joint near the weld area are machined with inclined grooves distributed at 45° to connect carbon fibers. After the variable diameter structure is coated with carbon fiber, the outer diameter of the joint at that point is consistent with the outer diameter of the final tube body.

[0024] In some embodiments, a rectangular opening groove 12 is provided on the drill pipe body 4. The rectangular opening groove 12 is inclined and the axial direction of the rectangular opening groove 12 is inclined at 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 a rectangular opening groove 12 in the same wall thickness area of ​​the pipe body 4 at a 45° direction. The size of a single opening groove is 40x20mm. The grooves are arranged in parallel, and their center points are also arranged at a 40x20mm interval.

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

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

[0029] In some embodiments, the heat insulation coating includes an outer surface heat insulation coating 5 and an inner surface heat 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 disposed on the heat insulation coating; The wear-resistant coating includes an outer surface wear-resistant coating 3 and an inner surface wear-resistant coating 8 disposed on a carbon fiber material layer.

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

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

[0032] In some embodiments, the drill pipe body 4 used can achieve the strength of S135 and V150 steel grades. It is made of seamless steel with a chemical composition such as 0.22-0.26% C, 0.45-0.52% Mn, 1.00-1.1% Cr, and 0.68-0.75% Mo. After thickening the pipe ends, it is quenched at 860-900℃ for 50-55 minutes using an internal spray and external quenching machine with a 15%-20% water-based quenching solution. The tempering temperature is 600-620℃ for 80-90 minutes. The yield strength reaches 1000MPa, and the impact toughness (test temperature -20℃, 7.5x10mm size) is 85-110J.

[0033] In some embodiments, the carbon fiber used is an advanced composite material made of carbon fiber and resin, etc., with relatively high specific strength and specific modulus among existing engineering materials. It is selected from materials such as T700 and T800. Its two-dimensional planar braided structure is twill weave, 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 is not less than 3 mm. In specific implementations, the thickness of the inner and outer layers is 5-10 mm.

[0034] The outer surface carbon fiber material layer 1 and the inner surface carbon fiber material layer 7 are first prepared on the outer surface of the drill pipe body 4 using a wet winding molding process, using fiber filaments impregnated with liquid resin. Then, the outer surface of the two end joints near the weld groove area is clamped and pressurized using a mold, and then cured together using an oven molding process.

[0035] After the outer surface is produced, the inner surface of the drill pipe is prepared using a resin transfer molding process. Then, the inner surface of the two end joints is fastened and pressurized using a mold in the area near the weld groove. Finally, they are cured together using an oven molding process.

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

[0037] The wear-resistant coating used in this invention is model TK34P, which was 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 is 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 this invention is manufactured through a process that involves cleaning the substrate surface using sandblasting, followed by spraying a red primer (a mixture with phenolic resin as the main component), and then curing at 190°C for 100 minutes. Subsequently, the wear-resistant coating is sprayed onto the surface and cured at 220°C for 120 minutes. This process yields a wear-resistant coating that meets the required specifications.

[0039] In the description of this invention, terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," which indicate direction or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. These are used merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0040] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

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

[0042] The technical solution of the present invention has been described above with reference to 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 can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all 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 by, The substrate includes a heat-insulating coating, a carbon fiber material layer, and a wear-resistant coating, which are sequentially disposed on both the inner and outer surfaces of the substrate. The production process of the heat-insulating coating specifically includes the following steps: S1. The substrate surface is cleaned and treated using a pre-defined method; wherein the pre-defined method includes at least a sandblasting process. S2. Apply at least one layer of heat-insulating coating; S3. Incubate at a set temperature for a set time for curing; The heat-insulating coating is an inorganic water-based coating, which includes a synthetic silicate solution, aluminum silicate fiber, and hollow glass microspheres. The heat insulation coating includes an outer surface heat insulation coating and an inner surface heat insulation coating respectively disposed on the substrate; the thickness of both the outer surface heat insulation coating and the inner surface heat 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 disposed on the heat insulation coating; the thickness of both 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 disposed on the carbon fiber material layer; the thickness of both the outer surface wear-resistant coating and the inner surface wear-resistant coating is not less than 0.1 mm.

2. A high strength carbon fiber composite insulated drill pipe for use in corrosive well conditions according to claim 1, characterized in that, The base includes a connector and a drill pipe body, which are coaxially and fixedly connected.

3. The high-strength carbon fiber composite heat-insulating drill pipe for corrosive well conditions according to claim 2, characterized in that, The joint has inclined grooves on its inner and outer surfaces near one end of the drill pipe body, and the inclined grooves are inclined at 45° relative to the axis of the joint.

4. A high-strength carbon fiber composite heat-insulating drill pipe for corrosive well conditions according to claim 2, characterized in that, A rectangular opening groove is provided on the drill pipe body. The rectangular opening groove is inclined, and the axial direction of the rectangular opening groove is inclined at 45° relative to the axial direction of the pipe body.

5. A high-strength carbon fiber composite heat-insulating drill pipe for corrosive well conditions according to claim 4, characterized in that, The two adjacent rectangular opening slots are spaced apart.

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

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

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

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