Composite drill rod and integral forming preparation method thereof

Abstract

The composite drill rod comprises a composite pipe body, a first metal connector, a second metal connector and a lining pipe arranged between the composite pipe body and the first metal connector. The outer wall of the first pipe body connecting section of the first metal connector and the outer wall of the second pipe body connecting section of the second metal connector are each provided with a conical connecting face and a cylindrical connecting face, and thin nails are densely distributed on the cylindrical connecting faces. The inner wall of the connecting section of the composite material pipe body is matched with the outer wall of the connecting section of the pipe body in shape and is connected with the pipe body through a bonding layer; the thick end of the thin nail is located in the drill hole of the pipe body connecting section, an adhesive layer is arranged between the thick end of the thin nail and the inner wall of the drill hole, and the thin end of the thin nail is located in the composite pipe body and used for forming a mechanical and adhesive mixed connecting structure. According to the drill rod, stress concentration can be avoided, the consistency of bearing is enhanced, the tensile strength and the torsional strength of the drill rod are improved, and the drill rod is lighter, higher in bearing capacity and higher in reliability. The invention further discloses an integral forming preparation method of the composite drill rod.

Description

Technical Field

[0001] This invention belongs to the field of drilling equipment technology, and in particular relates to a composite material drill pipe and its integral molding preparation method. Background Technology

[0002] Drill pipe is an essential drilling tool. Inside the well, it must withstand complex loads including internal and external pressure, friction and wear, bending, torque, and vibration, as well as corrosion from drilling fluids, oil and gas, and seawater. Therefore, using lightweight, high-strength drill pipe is a key direction for further improving drilling capabilities under existing drilling equipment and processes. Compared to traditional metallic materials, continuous fiber-reinforced resin matrix composites (hereinafter referred to as composite materials) have advantages such as low density, high strength, corrosion resistance, fatigue resistance, strong material performance design flexibility, and simple molding. Composite materials are considered by many equipment fields as the optimal solution for material lightweighting.

[0003] The strength of the connection structure between the drill pipe body and the steel joint determines the reliability of the drill pipe. The friction welding connection process used in steel drill pipes is clearly unsuitable for connecting composite material pipe bodies and steel joints. The design and strength analysis of connections in composite material structures differ from those in metallic material structures, with some aspects being fundamentally different. Furthermore, the factors affecting the connection strength of composite materials are far more complex.

[0004] In existing technologies, the connection between composite material tubes and drill pipe steel joints is mostly achieved through adhesive bonding or a combination of adhesive bonding and pin reinforcement. Firstly, for adhesive bonding structures, their load-bearing capacity is significantly affected by process factors such as adhesive layer thickness and uniformity, making it difficult to guarantee consistent load-bearing capacity in large-area adhesive structures. Secondly, for pin-reinforced mechanical connections, drilling often disrupts the continuity of fibers in the composite material tube, leading to increased stress concentration around the hole under load and reducing the reliability of the connection structure. Thirdly, in the existing fabrication process of drill pipe composite material tube-to-steel joint connection structures, the molding of the composite material tube is independent of its assembly with the steel joint, resulting in low production efficiency. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a composite material drill pipe and its integral molding preparation method, which can avoid stress concentration, enhance load-bearing consistency, significantly improve the tensile and torsional strength of the drill pipe, and enable the drill pipe to have higher load-bearing capacity, higher reliability, and improved production efficiency while being lighter.

[0006] The present invention provides a composite material drill pipe, comprising a composite material tube body, a first metal joint, a second metal joint, and an inner liner tube disposed between the first metal joint and the second metal joint;

[0007] The outer wall of the first pipe body connecting section of the first metal connector and the outer wall of the second pipe body connecting section of the second metal connector are both provided with a tapered connecting surface and a cylindrical connecting surface, and the cylindrical connecting surface is densely covered with fine nails;

[0008] The shape of the inner wall of the connecting section of the composite material tube matches the shape of the outer wall of the first tube connecting section and the second tube connecting section, and they are connected by an adhesive layer.

[0009] The thick end of the fine nail is located inside a drilled hole in the first or second pipe body connecting section. There is an adhesive layer between the thick end of the fine nail and the inner wall of the drilled hole. The thin end of the fine nail is located inside the composite material pipe body to form a mechanical and adhesive hybrid connection structure.

[0010] Preferably, in the above-mentioned composite material drill pipe, the composite material tube body and the inner liner tube are prepared by winding continuous fiber composite thermosetting resin, wherein the continuous fiber includes continuous carbon fiber and / or glass fiber and / or aramid fiber and / or quartz fiber.

[0011] The continuous fibers are distributed around the thin end of the nail, and the continuity of the continuous fibers is not damaged by the thin end of the nail.

[0012] Preferably, in the above-mentioned composite material drill pipe, the adhesive layer is formed by thermosetting resin used in the winding and molding of the composite material tube body through thermosetting.

[0013] Preferably, in the above-mentioned composite material drill pipe, the inner diameters of the first metal joint and the second metal joint are equal to the inner diameter of the inner liner tube; and the maximum outer diameters of the first metal joint and the second metal joint are equal to the maximum outer diameter of the composite material tube body.

[0014] Preferably, in the above-mentioned composite material drill pipe, the outer diameter of the cylindrical connecting surface is equal to the outer diameter of the inner liner tube.

[0015] Preferably, in the above-mentioned composite material drill pipe, the taper of the tapered connecting surface is no greater than 1:5.

[0016] This invention provides a method for integrally molding a composite material drill pipe, used to prepare a composite material drill pipe as described in any of the above claims, comprising:

[0017] S1: Drill holes on the cylindrical connecting surfaces of the first metal joint and the second metal joint, apply adhesive to the fine nail, and insert its coarse end into the drill hole until the adhesive cures.

[0018] S2: Install the first metal connector and the second metal connector on the mandrel, and wind continuous fibers on the mandrel section between the first metal connector and the second metal connector to form an inner liner tube;

[0019] S3: Continuous fibers are wound onto the first metal joint, the second metal joint, and the inner liner tube to form a composite material tube body. During the preparation of the composite material tube body, the continuous fibers bypass the fine nails to avoid being damaged by them.

[0020] S4: Place the first metal connector, the second metal connector, the inner liner tube, and the composite material tube body in a high-temperature furnace and cure them together to form an integrated connection structure;

[0021] S5: The composite material tube is machined to ensure that the overall outer diameter of the composite material tube remains consistent.

[0022] Preferably, in the above-mentioned method for integrally molding a composite drill pipe, after the adhesive has cured, the method further includes:

[0023] The first pipe connection section of the first metal connector and the second pipe connection section of the second metal connector are sandblasted.

[0024] Preferably, in the above-mentioned integral molding preparation method of composite material drill pipe, S3 includes: using a wet winding process or a dry winding process, the composite material tube body and the inner liner tube are prepared by winding with continuous fiber composite thermosetting resin.

[0025] Preferably, in the above-mentioned integral molding preparation method of composite material drill pipe, the high temperature curing process in S4 is in the range of 60°C to 200°C, the holding time is 1 hour to 24 hours, and the cooling is carried out by furnace cooling.

[0026] As described above, the composite material drill pipe provided by the present invention includes a composite material tube body, a first metal joint, a second metal joint, and an inner liner tube disposed between the first metal joint and the second metal joint; the outer walls of the first tube body connecting section of the first metal joint and the second tube body connecting section of the second metal joint are both provided with a tapered connecting surface and a cylindrical connecting surface, and the cylindrical connecting surface is densely covered with fine nails; the shape of the inner wall of the connecting section of the composite material tube body matches the shape of the outer walls of the first tube body connecting section and the second tube body connecting section and is connected by an adhesive layer; the coarse end of the fine nails... Within the drill hole opened in the first or second pipe body connecting section, an adhesive layer exists between the coarse end of the fine nail and the inner wall of the drill hole, while the fine end of the fine nail is located inside the composite material pipe body. This forms a hybrid mechanical and adhesive connection structure, ensuring that the continuity of the continuous fibers in the composite material is not broken. The overall continuous fibers provide higher strength, thus preventing stress concentration in the composite material drill rod, enhancing load-bearing consistency, and significantly improving the tensile and torsional strength of the drill rod. This results in a lighter drill rod with higher load-bearing capacity, higher reliability, and improved production efficiency. The integral molding method for the composite material drill rod provided by this invention has the same advantages as the aforementioned composite material drill rod. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0028] Figure 1 An overall cross-sectional view of an embodiment of a composite material drill rod provided by the present invention;

[0029] Figure 2 for Figure 1 A magnified view of part A in the diagram;

[0030] Figure 3 This is a schematic diagram of an embodiment of a method for integrally molding a composite drill pipe provided by the present invention;

[0031] Figure 4 This is a cross-sectional view of the connection structure in Comparative Example 1;

[0032] Figure 5 This is a cross-sectional view of the connection structure in Comparative Example 2;

[0033] Figure 6The tensile property curve of the product obtained in the first example;

[0034] Figure 7 The torsional performance curve of the product obtained in the first example;

[0035] Figure 8 The tensile property curve of the product obtained in Comparative Example 1;

[0036] Figure 9 The torsional performance curve of the product obtained in Comparative Example 1;

[0037] Figure 10 The tensile property curve of the product obtained in the second example;

[0038] Figure 11 The torsional performance curve of the product obtained in the second example;

[0039] Figure 12 The tensile property curve of the product obtained in Comparative Example 2;

[0040] Figure 13 The torsional performance curve of the product obtained in Comparative Example 2 is shown.

[0041] The annotations in the attached figures are explained as follows:

[0042] Composite material tube body 1, first metal joint 2, second metal joint 3, inner liner tube 4, first tube body connecting section 201, second tube body connecting section 301, conical connecting surface 5, cylindrical connecting surface 6, fine nail 7, adhesive layer 8, coarse end 701, drill hole 9, fine end 702, adhesive layer 10, stainless steel pin 11. Detailed Implementation

[0043] The core of this invention is to provide a composite material drill pipe and its integral molding preparation method, which can avoid stress concentration, enhance load-bearing consistency, significantly improve the tensile strength and torsional strength of the drill pipe, and make the drill pipe lighter while having higher load-bearing capacity, higher reliability, and improved production efficiency.

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] An embodiment of a composite material drill pipe provided by the present invention is as follows: Figure 1 and Figure 2 As shown, Figure 1 This is an overall sectional view of an embodiment of a composite material drill pipe provided by the present invention. Figure 2 for Figure 1 The enlarged schematic diagram of part A in the diagram includes the composite material tube 1, the first metal joint 2, the second metal joint 3, and the inner liner tube 4 disposed between the first metal joint 2 and the second metal joint 3. It should be noted that the first metal joint 2 and the second metal joint 3 can be, but are not limited to, steel joints, so that they have sufficient strength and hardness and can effectively realize the connection function. Of course, other materials with similar properties can also be selected according to actual needs.

[0046] The outer wall of the first pipe body connecting section 201 of the first metal connector 2 and the outer wall of the second pipe body connecting section 301 of the second metal connector 3 are both provided with a conical connecting surface 5 and a cylindrical connecting surface 6. The cylindrical connecting surface 6 is densely covered with fine nails 7. It should be noted that... Figure 1 It can be seen that there are many fine nails 7, not only arranged in multiple rows along the axial direction of the pipe body connection section, but also arranged in multiple rows along the circumference of the pipe body connection section, so as to provide a stronger fastening force over a larger range of this pipe body connection section.

[0047] The shape of the inner wall of the connecting section of the composite material tube 1 matches the shape of the outer wall of the first tube connecting section and the second tube connecting section and is connected by the adhesive layer 8. It should be noted that the composite material tube 1 is tightly fixed together with the first tube connecting section and the second tube connecting section to form a solid whole.

[0048] The coarse end 701 of the fine nail 7 is located within a drilled hole 9 in the first pipe connecting section 201 or the second pipe connecting section 301. Specifically, these drilled holes 9 can be evenly distributed in 5 to 20 rows along the length of the cylindrical connecting surface 6 and in 10 to 20 rows along the circumference of the cylindrical connecting surface 6, for a total of 50 to 400 holes. The diameter of the drilled hole 9 is preferably 1.1 mm to 5.2 mm, which is 0.1 mm to 0.2 mm larger than the diameter of the corresponding fine nail 7. The depth of the drilled hole 9 is 3 mm to 5 mm. Its coarse end 701 is preferably cylindrical with a diameter of 1.0 mm to 5.0 mm, and its fine end 702 can be conical. The coarse end of the fine nail 7 and the drilled hole 9... An adhesive layer 10 is provided between the inner walls. This adhesive layer 10 can be formed by curing epoxy resin or acrylic acid. The fine end 702 of the fine nail 7 is located inside the composite material tube 1 to form a mechanical and adhesive hybrid connection structure. It can be seen that these fine nails 7 are located inside the composite material tube 1 and the first metal joint 2 or the second metal joint 3. They are firmly connected to the drilled holes 9 of the first metal joint 2 or the second metal joint 3 by means of adhesive. Moreover, the fine end is inserted into the composite material tube 1 to achieve a firm connection with the composite material tube 1, thereby effectively fixing the composite material tube 1 and the first metal joint 2 or the second metal joint 3 into a whole, effectively reducing the overall weight and increasing the degree of integration.

[0049] As described above, in the embodiments of the composite material drill pipe provided by the present invention, the drill pipe includes a composite material tube body, a first metal joint, a second metal joint, and an inner liner tube disposed between the first metal joint and the second metal joint; the outer wall of the first tube body connecting section of the first metal joint and the outer wall of the second tube body connecting section of the second metal joint are both provided with a tapered connecting surface and a cylindrical connecting surface, and the cylindrical connecting surface is densely covered with fine nails; the shape of the inner wall of the connecting section of the composite material tube body matches the shape of the outer wall of the first tube body connecting section and the second tube body connecting section and is connected by an adhesive layer; the thick end of the fine nail is located at... Inside the borehole opened in the first or second pipe body connecting section, there is an adhesive layer between the coarse end of the fine nail and the inner wall of the borehole, and the fine end of the fine nail is located inside the composite material pipe body to form a mechanical and adhesive hybrid connection structure. This ensures that the continuity of the continuous fibers in the composite material is not broken, and the overall continuous fibers can bring higher strength. Thus, the composite material drill rod can avoid stress concentration, enhance load-bearing consistency, and significantly improve the tensile and torsional strength of the drill rod. This makes the drill rod lighter, with higher load-bearing capacity, higher reliability, and improved production efficiency.

[0050] In a specific embodiment of the above-mentioned composite material drill pipe, the composite material tube body and the inner liner tube are prepared by winding continuous fiber composite thermosetting resin. The continuous fiber includes continuous carbon fiber and / or glass fiber and / or aramid fiber and / or quartz fiber, or a hybrid fiber composite thermosetting resin of the above fiber combination is prepared by winding process. When carbon fiber is used, T700 carbon fiber can be selected. The continuous fiber is distributed around the thin end of the nail and the continuity of the continuous fiber is not damaged by the thin end of the nail.

[0051] In another specific embodiment of the above-mentioned composite material drill pipe, the adhesive layer can be formed by thermosetting resin used in the winding molding of composite material tube through heat curing, which results in a better curing effect.

[0052] In another specific embodiment of the aforementioned composite material drill pipe, the inner diameters of the first and second metal joints are equal to the inner diameter of the liner tube, for example, 50 mm; the maximum outer diameters of the first and second metal joints are equal to the maximum outer diameter of the composite material tube body, for example, 74 mm. Furthermore, the outer diameter of the cylindrical connecting surface is equal to the outer diameter of the liner tube, for example, 60 mm. The taper of the tapered connecting surface is preferably no greater than 1:5, which can be selected according to actual needs, for example, 1:10, as long as it effectively allows the continuous fibers to pass around.

[0053] An embodiment of the integral molding method for manufacturing composite drill pipe provided by the present invention is as follows: Figure 3 As shown, Figure 3 This is a schematic diagram of an embodiment of a method for integrally molding a composite material drill pipe provided by the present invention. This method, used to prepare a composite material drill pipe as described above, may include the following steps:

[0054] S1: Drill holes on the cylindrical connecting surfaces of the first metal joint and the second metal joint, apply adhesive to the fine nail, and insert its coarse end into the drill hole until the adhesive cures.

[0055] It should be noted that the diameter of the drill hole can be 3.2 mm and the depth can be 3 mm. The diameter of the cylindrical root of the fine nail can be 3.0 mm. The adhesive can be epoxy resin or acrylic resin, etc., which can be cured at room temperature. The curing time of the adhesive can be 12 hours to 24 hours, and more preferably 16 hours. The curing of the adhesive means that the fine nail is tightly fixed to the drill hole. Moreover, after the adhesive has cured, the process may include: sandblasting the first pipe connection section of the first metal joint and the second pipe connection section of the second metal joint. This sandblasting process can use gravel with a particle size range of 5 mesh to 220 mesh, and more preferably 50 mesh.

[0056] S2: Install the first metal connector and the second metal connector on the mandrel, and wind continuous fibers on the mandrel section between the first metal connector and the second metal connector to form an inner liner tube;

[0057] It should be noted that one of the first and second metal connectors can have a male thread and the other a female thread, which is necessary to connect two adjacent drill pipes. That is, inserting the male-threaded metal connector of one drill pipe into the female-threaded metal connector of another drill pipe achieves a secure connection. Furthermore, this mandrel provides a preparation mold; its outer diameter is equal to the inner diameter of the first and second metal connectors, preferably 50mm. This mandrel allows the components to form a regular whole. After subsequent preparation, the mandrel is removed, leaving only the final composite drill pipe. During the mold assembly process before winding, the metal connector is fitted onto the outer surface of the mandrel. Due to the wall thickness of the metal connector, there is a step (height difference) between the outer surface of the metal connector and the outer surface of the mandrel. Therefore, circumferential winding is required in the area between the two metal connectors to level this step. This circumferential winding forms the inner liner tube. A wet winding process is preferred, with the winding angle close to 90° to the axial angle, and the winding range being the mandrel section between the two metal connectors. This inner liner can also serve to secure the two metal joints together.

[0058] S3: Continuous fibers are wound around the first metal joint, the second metal joint and the inner liner tube to form a composite material tube. During the preparation of the composite material tube, the continuous fibers bypass the fine nails to avoid being damaged by the fine nails.

[0059] It should be noted that the key difference in this embodiment compared to the prior art is that the thick end of the fine nail is fixed first, leaving the thin end exposed on the surface, and then continuous fibers are wound around it. The presence of the thin end of these fine nails allows the continuous fibers to bypass the thin end of the nails without being punctured during the winding process. This allows the composite material tube to be manufactured without interrupting the fiber continuity, and the overall strength of the continuous fibers is not affected. After the subsequent curing steps, no gaps will form around the fine nails, allowing the continuous fibers to better surround the nails. The resulting drill rod has higher strength, unlike the drill rods manufactured by the prior art where the continuous fibers are punctured, causing a reduction in strength.

[0060] S4: Place the first metal joint, the second metal joint, the inner liner tube, and the composite material tube body in a high-temperature furnace and cure them together to form an integrated connection structure.

[0061] It should be noted that this high-temperature furnace is used to cure the resin or colloid in the overall structure. After curing, it is solidified into a whole. This curing and molding process is simple, low-cost, and has higher reliability.

[0062] S5: Perform turning on the composite material tube to ensure that the overall outer diameter of the composite material tube remains consistent.

[0063] It should be noted that this turning process must ensure that the outer diameter of the composite material tube is equal to the outer diameter of the first and second metal joints at both ends, for example, 74mm. This way, from the appearance, the whole tube appears to have the same diameter, which is necessary for it to be used as a drill rod.

[0064] In a specific embodiment of the above-mentioned method for integrally molding composite drill pipe, S3 may specifically include: using a wet winding process or a dry winding process, the winding angle can be a circumferential winding at an angle of approximately 90° relative to the axial direction of the pipe body, and the composite pipe body and the inner liner tube are prepared by winding continuous fiber composite thermosetting resin. When using a wet winding process, the winding angle combination can be [(90°)(+45° / -45°)(0°)2(-45° / +45°)(90°)] n .

[0065] In addition, the above winding angle can be one or more combinations between 0° and 90°.

[0066] In another specific embodiment of the above-mentioned integral molding preparation method of composite material drill pipe, the high-temperature curing process temperature range in S4 can be 60°C to 200°C, more preferably 170°C, the holding time is 1 hour to 24 hours, more preferably 4 hours, and the cooling is carried out by furnace cooling.

[0067] The aforementioned scheme is the first example. Below is a second example, with the overall scheme being the same as the first, except for the size and the type of fiber used, as detailed below:

[0068] Both the first and second metal joints are steel joints, and their maximum outer diameter is the same as that of the composite material tube body, both being 89 mm. The inner diameters of the first and second metal joints are the same as those of the inner liner tube, both being 68 mm. The outer diameter of the cylindrical connecting surface is the same as that of the inner liner tube, both being 76 mm. The taper of the tapered connecting surface is 1:5. The composite material tube body and the inner liner tube are made of continuous E-glass fiber composite epoxy resin through a wet winding process.

[0069] The production method is as follows:

[0070] S01. Drill holes in the cylindrical connecting surface of the steel joint, apply adhesive to the fine nails and insert them into the drilled holes. After the adhesive has cured, sandblast the connecting section of the steel joint.

[0071] The drill holes are evenly distributed in 5 rows along the length of the cylindrical connection surface and in 10 columns along the circumference of the cylindrical connection surface, totaling 50 holes. The diameter of the drill hole 7 is 5.2 mm and the depth is 3 mm. The diameter of the cylindrical root of the fine nail 3 is 5.0 mm. The adhesive used is a room temperature curing epoxy adhesive, and the room temperature curing time is 16 hours after the fine nail is covered with adhesive and inserted into the drill hole. The sandblasting treatment uses 30 mesh gravel.

[0072] S02. Install two steel joints on the mandrel, and wind the inner liner tube on the mandrel section between the two steel joints; wherein, the outer diameter of the mandrel is the same as the inner diameter of the steel joints, which is 68mm; wherein, the winding of the inner liner tube adopts a wet winding process, the winding angle is nearly 90° circumferential winding, and the winding range is the mandrel section between the two steel joints.

[0073] S03. A composite material tube body is prepared by winding the composite material tube body onto the steel joint and the inner lining tube; wherein, the composite material tube body is wound using a wet winding process, and the winding angle combination is [(90°)(+30° / -30°)4(90°)]. n .

[0074] S04. The two steel joints, the inner lining pipe, and the composite material pipe are cured together in a high-temperature furnace to form a connection structure; the curing temperature is 120℃, the curing time is 4h, and the cooling method is furnace cooling.

[0075] S05. The composite material tube is machined to make its outer diameter 89mm.

[0076] Comparative Example 1:

[0077] refer to Figure 4 , Figure 4 This is a cross-sectional view of the connection structure in Comparative Example 1. Figure 4 The proposed solution is largely the same as the first example above, except that neither of the two steel joints contains drill holes or fine nails. Instead, an adhesive layer exists only between the conical and cylindrical connecting surfaces of the inner wall of the composite material tube and the outer wall of the steel joint, forming a bonded connection between the steel joint and the composite material tube. The corresponding method for integrally molding the composite drill pipe is identical to the first example, except for the absence of step S1.

[0078] Comparative Example 2:

[0079] The characteristics of the drill pipe connection structure can be referenced. Figure 5 , Figure 5The cross-sectional view of the connection structure in Comparative Example 2 is largely the same as the second example above, except that the steel joints do not contain drill holes or pins; the adhesive layer exists only between the conical and cylindrical connection surfaces of the inner wall of the composite material tube and the outer wall of the steel joint. Stainless steel pins 11 pass through the through holes in the composite material tube and the joint grooves in the steel joint, forming a mechanical-adhesive hybrid connection structure between the steel joint and the composite material tube. The stainless steel pins 11 have a diameter of 15 mm, are arranged in one row along the length of the cylindrical connection surface, and three rows evenly distributed around the circumference of the cylindrical connection surface, for a total of three pins. The corresponding integrated molding method for the composite material drill rod, except for the absence of preparation step S01, first prepares the composite material drill rod with an adhesive structure according to steps S02, S03, S04 and S05 in the second example; then, step S06 is added: drilling a hole in the drill rod connection section, inserting an adhesive-coated stainless steel pin, and curing at room temperature; wherein, the drilling diameter is 15.2 mm, the drilling depth is 9 mm; wherein, the adhesive is an epoxy adhesive that can cure at room temperature, and the curing time is 16 h.

[0080] The mechanical performance tests will be conducted below:

[0081] Tensile and torsional properties were tested on the two examples and two comparative products mentioned above. The results of the tensile strength and torsional strength tests are shown in Table 1 and... Figures 6 to 13 Table 1 shows the test results. Figure 6 The tensile property curve of the product obtained in the first example. Figure 7 The torsional performance curve of the product obtained in the first example. Figure 8 The tensile property curve of the product obtained in Comparative Example 1 is shown. Figure 9 The torsional performance curve of the product obtained in Comparative Example 1 is shown. Figure 10 The tensile property curve of the product obtained in the second example. Figure 11 The torsional performance curve of the product obtained in the second example. Figure 12 The tensile property curve of the product obtained in Comparative Example 2 is shown. Figure 13 The torsional performance curve of the product obtained in Comparative Example 2 is shown.

[0082] Table 1 Test Results

[0083]

[0084] The test results in the table above show that, compared with the first example and Comparative Example 1, when the drill rod size and the material and layup structure of the composite material tube are the same, the connection structure of the drill rod provided in this application can increase the tensile strength of the drill rod by 156% and the torsional strength of the drill rod by 254% compared with the existing adhesive connection structure; compared with the second example and Comparative Example 2, when the drill rod size and the material and layup structure of the composite material tube are the same, the connection structure of the drill rod provided in this application can increase the tensile strength of the drill rod by 88% and the torsional strength of the drill rod by 54% compared with the adhesive-pin hybrid connection structure.

[0085] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A composite material drill pipe, characterized in that, It includes a composite material tube body, a first metal joint, a second metal joint, and an inner liner tube disposed between the first metal joint and the second metal joint; The outer wall of the first pipe body connecting section of the first metal connector and the outer wall of the second pipe body connecting section of the second metal connector are both provided with a tapered connecting surface and a cylindrical connecting surface, and the cylindrical connecting surface is densely covered with fine nails; The shape of the inner wall of the connecting section of the composite material tube matches the shape of the outer wall of the first tube connecting section and the second tube connecting section, and they are connected by an adhesive layer. The thick end of the fine nail is located inside a drilled hole in the first or second pipe body connecting section. There is an adhesive layer between the thick end of the fine nail and the inner wall of the drilled hole. The thin end of the fine nail is located inside the composite material pipe body to form a mechanical and adhesive hybrid connection structure.

2. The composite material drill pipe according to claim 1, characterized in that, The composite material tube and the inner liner tube are prepared by winding continuous fiber composite thermosetting resin, wherein the continuous fiber includes continuous carbon fiber and / or glass fiber and / or aramid fiber and / or quartz fiber. The continuous fibers are distributed around the thin end of the nail, and the continuity of the continuous fibers is not damaged by the thin end of the nail.

3. The composite material drill pipe according to claim 2, characterized in that, The adhesive layer is formed by thermosetting resin used in the winding and molding of the composite material tube through heat curing.

4. The composite material drill pipe according to claim 1, characterized in that, The inner diameters of the first metal connector and the second metal connector are equal to the inner diameter of the inner liner tube; the maximum outer diameter of the first metal connector and the second metal connector is equal to the maximum outer diameter of the composite material tube.

5. The composite material drill pipe according to claim 1, characterized in that, The outer diameter of the cylindrical connecting surface is equal to the outer diameter of the inner lining tube.

6. The composite material drill pipe according to claim 1, characterized in that, The taper of the tapered connecting surface is no greater than 1:

5.

7. A method for integrally molding a composite material drill pipe, characterized in that, For preparing the composite material drill pipe as described in any one of claims 1-6, comprising: S1: Drill holes on the cylindrical connecting surfaces of the first metal joint and the second metal joint, apply adhesive to the fine nail, and insert its coarse end into the drill hole until the adhesive cures. S2: Install the first metal connector and the second metal connector on the mandrel, and wind continuous fibers on the mandrel section between the first metal connector and the second metal connector to form an inner liner tube; S3: Continuous fibers are wound onto the first metal joint, the second metal joint, and the inner liner tube to form a composite material tube body. During the preparation of the composite material tube body, the continuous fibers bypass the fine nails to avoid being damaged by them. S4: Place the first metal connector, the second metal connector, the inner liner tube, and the composite material tube body in a high-temperature furnace and cure them together to form an integrated connection structure; S5: The composite material tube is machined to ensure that the overall outer diameter of the composite material tube remains consistent.

8. The method for integrally molding a composite material drill pipe according to claim 7, characterized in that, After the adhesive has cured, it also includes: The first pipe connection section of the first metal connector and the second pipe connection section of the second metal connector are sandblasted.

9. The method for integrally molding a composite material drill pipe according to claim 7, characterized in that, The S3 includes: using a wet winding process or a dry winding process, the composite material tube body and the inner liner tube are prepared by winding continuous fiber composite thermosetting resin.

10. The method for integrally molding a composite material drill pipe according to claim 7, characterized in that, The high-temperature curing process in S4 has a temperature range of 60°C to 200°C and a holding time of 1 hour to 24 hours, and is cooled by furnace cooling.

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