Waste oil pipe green remanufacturing method and oil pipe screwed joint structure

Abstract

The invention discloses a waste oil pipe green remanufacturing method and an oil pipe screwed joint structure, and belongs to the technical field of oil pipes. Comprising an oil pipe body and a coupling fastened with the oil pipe body through threads, the pipe end of the oil pipe body is sequentially provided with external threads, an outer sealing face and an end face shoulder, and the end face shoulder is located on the end face of the end, provided with the external threads, of the oil pipe body; internal threads, internal sealing surfaces and torque shoulders are sequentially arranged on the inner surfaces of the two sides of the coupling; the external threads and the internal threads are trapezoidal threads; the outer sealing face and the inner sealing face are in interference fit to form a sealing structure used for preventing fluid in the oil pipe from leaking. The end face circular bead is matched with the torque circular bead in an abutting mode. The connection strength and the sealing performance can be improved by optimizing the design of the threads and the sealing structure, meanwhile, efficient remanufacturing of the waste oil pipe is achieved by combining intelligent detection and an environment-friendly process, resource waste and carbon emission are reduced, and the environment-friendly manufacturing concept is met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil pipes, and particularly relates to a green remanufacturing method for waste oil pipes and an oil pipe threaded joint structure. BACKGROUND

[0002] The oil pipe threaded connection structure is widely used in the process of oil and gas field exploitation to realize efficient connection and sealing between oil pipes and oil pipes, oil pipes and couplings, and is an important technical means to ensure the safety of wellbores and operation efficiency. However, the traditional oil pipe threaded structure is prone to problems such as sealing failure, connection loosening or fatigue fracture under high temperature and high pressure or in a corrosive medium environment, which seriously affects the safety and reliability of oil and gas exploitation.

[0003] In addition, as an important tool in oil and gas drilling and development, the oil pipe often suffers different degrees of damage, such as corrosion pits, wall thickness thinning or thread wear, during service due to complex working conditions and multiple downhole and uphole operations, resulting in a large number of idle waste oil pipes. These waste oil pipes not only occupy storage space, but also accelerate corrosion due to long-term stacking, further reducing the possibility of reuse. At present, there is no unified standard for waste oil pipe recycling at home and abroad, especially for old oil pipes with defects, and there is a lack of special repair and remanufacturing technical solutions. The existing threaded joint design is mainly based on the API Spec 5B standard and is mainly suitable for the geometric parameter performance of new oil pipes, and the special conditions of waste oil pipes are not considered, which is difficult to meet the needs of green remanufacturing.

[0004] With the rise of the concept of green manufacturing, how to efficiently repair waste oil pipes and put them into use again has become an important research direction in the field of petroleum equipment. However, in the traditional remanufacturing process, due to the difficulty in effectively sealing the damaged part of the thread, there is a high risk of leakage during repeated use, and a new threaded connection structure is needed to improve the sealing performance and connection strength, while adapting to the repair needs of oil pipes in the remanufacturing scene. In recent years, although some technologies have tried to improve the thread sealing method, there are still significant deficiencies. For example, Chinese invention patent CN116575869A discloses an oil pipe threaded connection structure and a waste oil pipe recycling remanufacturing method, which improves the sealing effect by optimizing the taper of the sealing surface and the interference amount, and proposes a complete remanufacturing process. However, in this technology, the inner and outer thread heights are both 1.1 mm, and the thread is prone to sticking during rotation; at the same time, the equal taper sealing structure used in this technology is prone to stress concentration at the two end points of the sealing surface due to the large interference amount, resulting in uneven stress distribution on the sealing surface, affecting the service life and reliability. Therefore, the existing technology still needs to be improved in terms of sealing performance, anti-sticking ability and stress distribution uniformity.

[0005] In summary, the current tubing thread connection structure and the remanufacturing technology of waste tubing have obvious deficiencies in sealing performance, connection strength, fatigue resistance and adaptability, which are difficult to meet the use requirements under complex working conditions and the requirements of green manufacturing. Developing a new type of tubing thread connection structure that can balance high-performance sealing, self-locking ability enhancement and stress distribution, and combining with intelligent and environmentally friendly remanufacturing process, has become a technical problem to be solved. SUMMARY

[0006] The present application provides a green remanufacturing method for waste tubing and a tubing thread joint structure, aiming to solve the technical defects of the sealing failure, connection loosening and fatigue fracture of the existing tubing thread connection structure in high pressure, high temperature or corrosive environment, and the difficulty in effectively sealing the damaged part of the thread during the remanufacturing process of the waste tubing.

[0007] The present application provides a tubing thread joint structure, which adopts the following technical solutions, including a tubing body and a coupling fastened with the tubing body through threads, characterized in that the tubing body pipe end is sequentially provided with an external thread, an external sealing surface and an end face shoulder, the end face shoulder is located at the end face of the end of the tubing body provided with the external thread; the inner surface of both sides of the coupling is sequentially provided with an internal thread, an internal sealing surface and a torque shoulder; the external thread and the internal thread are both trapezoidal threads; the external sealing surface and the internal sealing surface are in interference fit to form a sealing structure for preventing internal fluid leakage of the tubing; and the end face shoulder and the torque shoulder are in top-to-top fit.

[0008] Further, the taper of the external thread provided at the top end of the tubing body and the taper of the internal thread provided at both ends of the coupling are both 1:16, the pitch is both 8 teeth / inch, the load bearing surface angle is both -5°-0°, and the guide surface angle is both 10°-15°; wherein the groove width of the external thread is 1.5875mm, the tooth width is 1.5875mm, and the tooth height is 1mm; the groove width of the internal thread is 1.613mm, the tooth width is 1.5621mm, and the tooth height is 1.2mm.

[0009] Further, the load bearing surface angle of the external thread and the internal thread is a negative angle, forming a reverse hook type bias trapezoidal thread.

[0010] Further, the interference amount of the external sealing surface and the internal sealing surface is at least 0.2mm, the length of the external sealing surface is 5mm, and the length of the internal sealing surface is 5mm.

[0011] Further, the outer sealing surface is provided with a circular arc protrusion, which is an elliptical structure with a center position 3mm away from the reference line of the outer threaded end face, and the inner sealing surface is provided with a circular arc protrusion two, which is an elliptical structure with a center position 1mm away from the inner threaded end face, and the elliptical structure has a long axis size of 1mm and a short axis size of 0.1-0.2mm.

[0012] Further, the transition surface of the outer sealing surface and the end face shoulder is provided as a curved profile, which is a Bezier curve or a circular arc; the transition surface of the inner sealing surface and the torque shoulder is provided as a curved profile, which is a Bezier curve or a circular arc; the interference compression amount of the outer sealing surface and the inner sealing surface is 0.3±0.05mm.

[0013] Further, the outer threaded end face shoulder angle is 0° to -15°, and the inner threaded torque shoulder angle is 0° to -15°.

[0014] A green remanufacturing method of waste oil pipes, comprising the following steps:

[0015] S1, providing waste oil pipes, which are waste oil pipes recovered from different areas of oil and gas fields and oil and gas wells;

[0016] S2, waste oil pipe pretreatment and information collection: performing initial inspection on the appearance of the recovered waste oil pipes to remove obviously bent, broken or severely deformed oil pipes; performing surface cleaning on part of the oil pipes to remove attached matters such as oil stains and silt; using an industrial camera to perform high-definition image collection to obtain image information of pipe body damage and corrosion morphology;

[0017] S3, intelligent identification and grading of oil pipe state: inputting the image collected in step S2 into a pre-trained convolutional neural network model to automatically identify pipe body damage grade, corrosion pit depth and crack direction index; according to the identification result, the oil pipes are divided into class A, class B and class C; wherein class A is slightly worn and can be directly repaired, class B is moderately damaged and needs to be machined, and class C is severely damaged and cannot be remanufactured;

[0018] S4, environmentally friendly rust removal and surface treatment: for class A and class B oil pipes, using an environmentally friendly rust remover to perform chemical spray rust removal; using dry compressed air to dry or using a low-temperature drying device to realize drying; using a non-phosphorus environmentally friendly coating to perform rust-proof pre-coating on the surface;

[0019] S5, thread repair and structure remanufacturing: for class A oil pipes, using laser cladding technology to repair the worn parts of the oil pipes, cladding wear-resistant alloy powder to form a uniform and dense repair layer, and reprocessing the thread structure; for class B oil pipes, cutting off the end part of the oil pipe and reprocessing the thread structure, the thread structure being the outer thread and the inner thread in the oil pipe thread joint structure according to any one of claims 1-7.

[0020] S6. Mechanical and airtight performance testing: Conduct thread size consistency and coaxiality tests on remanufactured tubing samples; perform airtightness tests, hydrostatic strength tests, and fatigue life tests; unqualified tubing is returned for repair or rejection.

[0021] S7. Carbon Footprint Assessment and Digital Tracking: Record the remanufacturing process parameters and test data for each tubing; establish a carbon emission calculation model to comprehensively assess energy savings, material savings, and pollutant emission reduction; generate a unique tracking QR code to bind the identification data and carbon footprint record of each remanufactured tubing.

[0022] Furthermore, in step S5, for Class B tubing, the length of the tubing end to be cut is 80-120 mm.

[0023] Furthermore, after assembly, the sealing fit structure is monitored by an online monitoring system to detect the degree of interference sealing, assembly consistency, and thread preload status; the manufacturing process of the oil pipe thread connection structure adopts a carbon footprint monitoring and energy consumption assessment module.

[0024] The beneficial effects of this application are:

[0025] 1. This application designs a high-performance threaded joint, enabling the repaired oil pipe threaded joint to meet the technical performance requirements of the pipe body, which is in line with the concept of green manufacturing.

[0026] 2. This application adopts an environmentally friendly rust removal and surface treatment process, selects pipes that meet the performance requirements, and then repairs and remanufactures the threaded joints, which has good economic and social value.

[0027] 3. This application adopts a circular arc or Bezier curve sealing form to alleviate excessive stress concentration at both ends of the conical sealing surface, improve the stress balance of the conical sealing surface, and extend fatigue life.

[0028] 4. The threads in this application adopt a self-locking structure design to prevent loosening of the connection and improve connection safety.

[0029] 5. This application integrates intelligent detection and assembly status assessment to ensure consistency in the assembly process, achieve carbon emission monitoring, comply with energy conservation and environmental protection policy guidelines, and introduces a system for oil pipe status identification, material traceability, and remanufacturing adaptability analysis to improve the level of intelligent manufacturing. Attached Figure Description

[0030] For ease of explanation, this application is described in detail below with reference to specific embodiments and accompanying drawings.

[0031] Figure 1 This is a schematic diagram of the oil pipe threaded joint of this application;

[0032] Figure 2 This is a schematic diagram of the meshing of the internal and external threads in this application;

[0033] Figure 3 This is a schematic diagram of the external thread structure of this application;

[0034] Figure 4 This application Figure 3 Enlarged view of a portion at point A;

[0035] Figure 5 This is a schematic diagram of the internal thread structure of this application;

[0036] Figure 6 This application Figure 5 A magnified view of section B.

[0037] In the diagram: 1. Coupling; 1-1. Internal thread; 2. Oil pipe body; 2-1. External thread; 3. External sealing surface; 4. Internal sealing surface; 5. End face shoulder; 6. Torque shoulder; 7. Arc protrusion; 8. Arc protrusion II. Detailed Implementation

[0038] The following are specific embodiments of this application, described in conjunction with the accompanying drawings, to further illustrate the technical solutions of this application. However, this application is not limited to these embodiments. Specific details, such as particular configurations and components, are provided in the following description merely to aid in a comprehensive understanding of the embodiments of this application. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this application. Furthermore, for clarity and brevity, descriptions of known functions and structures have been omitted.

[0039] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0040] This invention relates to a green remanufacturing method for waste oil pipes and a structural design for an oil pipe threaded joint. The specific embodiments of the invention are described in detail below with reference to the accompanying drawings. The following example uses an oil pipe joint made of Φ73.02×5.51mm L80 steel. This oil pipe joint includes an oil pipe body 2 and a coupling 1. It achieves a highly efficient sealing connection through internal and external thread engagement and employs a double-seal structure design to improve sealing performance under high-pressure conditions.

[0041] like Figure 1A specific embodiment of a threaded joint structure for an oil pipe is shown, comprising an oil pipe body 2 and a coupling 1 fastened to the oil pipe body 2 by threads. The oil pipe body 2 is provided with an external thread 2-1, an external sealing surface 3, and an end face shoulder 5 in sequence at its pipe end. The end face shoulder 5 is located at the end face of the oil pipe body 2 where the external thread 2-1 is provided. The inner surfaces on both sides of the coupling 1 are provided with an internal thread 1-1, an internal sealing surface 4, and a torque shoulder 6 in sequence. Both the external thread 2-1 and the internal thread 1-1 are trapezoidal threads. The external sealing surface 3 and the internal sealing surface 4 are interference-fitted to form a sealing structure to prevent leakage of fluid inside the oil pipe. The end face shoulder 5 and the torque shoulder 6 are mating.

[0042] Specifically, the tubing body 2 has an external thread 2-1, and the coupling 1 has an internal thread 1-1. In the tightened state, the external thread 2-1 and the internal thread 1-1 mesh to form a high-strength connection. The end face shoulder 5 and the torque shoulder 6 effectively transmit axial preload during tightening, ensuring the connection has high tensile strength and fatigue resistance. The outer sealing surface 3 and the inner sealing surface 4 are interference-fitted to form a sealing structure, preventing internal fluid leakage and thus improving sealing performance. This design significantly reduces stress concentration while enhancing the overall stability of the connection structure.

[0043] Specifically, the tubing body 2 and the coupling 1 are mechanically connected by a trapezoidal thread. The symmetrical tooth design of the trapezoidal thread ensures that the load is evenly distributed on both sides of the thread teeth, avoiding the sticking phenomenon caused by stress concentration on one side.

[0044] In other preferred embodiments, such as Figures 3-6 As shown, the external thread 2-1 at the top of the tubing body 2 and the internal threads 1-1 symmetrically provided at both ends of the coupling 1 both have a taper of 1:16, a pitch of 8 threads / inch, a bearing surface angle of -5° to 0°, and a guide surface angle of 10° to 15°. Specifically, the external thread 2-1 has a groove width of 1.5875 mm, a thread width of 1.5875 mm, and a tooth height of 1 mm; the internal thread 1-1 has a groove width of 1.613 mm, a thread width of 1.5621 mm, and a tooth height of 1.2 mm. The bearing surface angles of the external thread 2-1 and the internal thread 1-1 are negative, forming a hook-shaped trapezoidal thread.

[0045] Specifically, the combination of taper and pitch creates a progressive contact pattern in the threaded pair, gradually building up contact stress during tightening. The combination of a negative angle on the bearing surface and a positive angle on the guide surface enables the thread to generate a self-locking effect under axial loads while maintaining smooth assembly. The fit between the symmetrical tooth profile of the external thread 2-1 and the asymmetrical tooth profile of the internal thread 1-1 compensates for machining errors through groove width differences, ensuring uniform contact on the thread meshing surfaces. The tooth height difference design allows the internal and external threads to undergo elastic deformation under overload, avoiding metal adhesion caused by traditional equal tooth height structures. These features give the thread excellent anti-sticking performance during repeated threading and unthreading operations, extending its service life.

[0046] In other preferred embodiments, the interference fit between the outer sealing surface 3 and the inner sealing surface 4 is at least 0.2 mm, the length of the outer sealing surface 3 is 5 mm, and the length of the inner sealing surface 4 is 5 mm.

[0047] Specifically, by setting the interference fit to at least 0.2 mm, sufficient elastic deformation is ensured after assembly of the inner and outer sealing surfaces to form the initial sealing pressure, while avoiding excessive interference fit that could lead to assembly difficulties or the risk of plastic deformation. The axial length of both the outer sealing surface 3 and the inner sealing surface 4 is limited to 5 mm. This ensures sufficient contact area to disperse stress while avoiding excessively long sealing surfaces that could increase frictional resistance or cause uneven stress distribution. The coordinated control of the interference fit and the length of the sealing surfaces ensures that the sealing contact pressure is evenly distributed within the axial range, preventing stress concentration at both ends of the sealing surfaces and maintaining the stability of the sealing structure.

[0048] In other preferred embodiments, such as Figure 4 and Figure 6 As shown, the outer sealing surface 3 is provided with an arc protrusion 7, which is an elliptical structure. The center of the arc protrusion 7 is 3mm away from the reference line of the end face of the external thread 2-1. The inner sealing surface 4 is provided with an arc protrusion 8, which is an elliptical structure. The center of the arc protrusion 8 is 1mm away from the end face of the internal thread. The major axis of the elliptical structure is 1mm and the minor axis is 0.1-0.2mm.

[0049] Specifically, through the above structure, the outer sealing surface arc protrusion 7 and the inner sealing surface arc protrusion 8 first form a primary seal at the contact point. This seal is an elliptical line contact, which generates a high contact specific pressure under the action of assembly pre-tightening force, effectively preventing high-pressure fluid leakage.

[0050] Furthermore, since both the inner and outer protrusions are elliptical structures, local interference fit occurs after radial pre-tightening, forming a second seal. This secondary seal not only enhances sealing redundancy but also compensates for dimensional defects that may exist in the remanufactured tubing, such as wall thinning, corrosion pits, and ellipticity errors. This ensures the sealing stability of the repaired tubing under complex conditions such as high pressure and corrosion.

[0051] Therefore, the double-arc protrusion structure of the present invention, on the basis of achieving primary sealing, forms secondary sealing through the interference of the double protrusions and elliptical geometric deformation, which significantly improves the sealing reliability and adaptability of remanufactured tubing.

[0052] Specifically, the design of the major axis (1mm) and minor axis (0.1-0.2mm) of the elliptical structure ensures the effective contact area of ​​the sealing surface and avoids sealing failure caused by defects such as thinning of the wall or corrosion pits that may exist in the old oil pipe. It is compatible with the dimensional deviation of the repaired oil pipe and improves the sealing stability of the remanufactured oil pipe.

[0053] Specifically, the transition surface between the outer sealing surface 3 and the end face shoulder 5 is set as a curved profile, which is a Bézier curve or a circular arc; the transition surface between the inner sealing surface 4 and the torque shoulder 6 is set as a curved profile, which is a Bézier curve or a circular arc; the interference compression of the outer sealing surface 3 and the inner sealing surface 4 is 0.3±0.05mm.

[0054] Specifically, the transition surfaces between the outer sealing surface 3 and the end face shoulder 5, and between the inner sealing surface 4 and the torque shoulder 6, adopt Bezier curves or circular arcs to replace the traditional right angle or acute angle transitions. This can disperse the stress load at both ends of the sealing surface, avoid cracking or fatigue damage of the sealing surface caused by stress concentration, and significantly improve the fatigue life of the sealing structure.

[0055] Specifically, the interference fit of 0.3 ± 0.05 mm ensures that the outer sealing surface 3 and the inner sealing surface 4 form a tight elastic contact after assembly. Even under the impact of high-pressure fluid, the elastic deformation of the material can compensate for minor gaps and prevent leakage. The interference fit range provides tolerance for possible slight dimensional deviations, achieving effective sealing without strict dimensional accuracy and reducing the difficulty of remanufacturing processes.

[0056] In other preferred embodiments, the angle of the shoulder 5 on the end face of the external thread 2-1 is 0° to -15°, and the angle of the torque shoulder 6 on the internal thread 1-1 is 0° to -15°.

[0057] Specifically, the shoulder 5 of the external thread 2-1 end face and the torque shoulder 6 of the internal thread 4 adopt a negative angle design of 0° to -15°, which can form a "barbed" axial constraint when mating. Combined with the self-locking structure of the thread (barbed trapezoidal thread), it further prevents the connection from loosening and improves the vibration resistance and fatigue resistance of the overall connection.

[0058] A green remanufacturing method for waste oil pipes includes the following steps:

[0059] S1. Provide waste oil pipes, which are waste oil pipes recovered from different areas of oil and gas fields and oil and gas wells;

[0060] S2. Pre-treatment and information collection of waste oil pipes: The waste oil pipes are initially inspected visually to remove those that are obviously bent, broken or severely deformed; the surface of the oil pipes is cleaned to remove oil, mud and other adhering substances; high-definition images are collected using an industrial camera to obtain image information on pipe damage and corrosion morphology.

[0061] S3. Intelligent identification and classification of oil pipe condition: Input the image collected in step S2 into the pre-trained convolutional neural network model to automatically identify the pipe damage level, corrosion pit depth, and crack orientation index; classify the oil pipe into three categories: A, B, and C according to the identification results; where category A is light wear and can be directly repaired, category B is moderate damage and requires machining, and category C is severe damage and cannot be remanufactured.

[0062] S4. Environmentally friendly rust removal and surface treatment: For Class A and Class B oil pipes, use environmentally friendly rust remover for chemical spraying; use dry compressed air to dry or use low-temperature drying equipment to achieve drying; apply a phosphorus-free environmentally friendly coating for rust prevention pre-coating;

[0063] S5. Thread Repair and Structural Remanufacturing: For Class A oil pipes, laser cladding technology is used to repair the worn parts of the oil pipe, cladding wear-resistant alloy powder to form a uniform and dense repair layer, and then reprocessing the thread structure; for Class B oil pipes, the oil pipe end is cut off, the length of the cut-off oil pipe end is preferably 80-120mm, and the thread structure is reprocessed, wherein the thread structure is the external thread 2-1 and internal thread 1-1 in the oil pipe threaded joint structure according to any one of claims 1-7;

[0064] S6. Mechanical and airtight performance testing: Conduct thread size consistency and coaxiality tests on remanufactured tubing samples; perform airtightness tests, hydrostatic strength tests, and fatigue life tests; unqualified tubing is returned for repair or rejection.

[0065] S7. Carbon Footprint Assessment and Digital Tracking: Record the remanufacturing process parameters and test data for each tubing; establish a carbon emission calculation model to comprehensively assess energy savings, material savings, and pollutant emission reduction; generate a unique tracking QR code to bind the identification data and carbon footprint record of each remanufactured tubing.

[0066] Specifically, after assembly, the sealing fit structure is monitored by an online monitoring system to detect the degree of interference sealing, assembly consistency, and thread preload status; the manufacturing process of the oil pipe thread connection structure adopts a carbon footprint monitoring and energy consumption assessment module.

[0067] Specifically, image acquisition and intelligent recognition are used to establish a digital characterization of tubing damage, replacing traditional manual visual inspection and achieving standardized grading. Environmentally friendly rust removal processes reduce harmful substance emissions during pretreatment, and phosphorus-free coatings avoid the risk of eutrophication in water bodies. Differentiated repair strategies select local cladding or end removal based on the degree of damage, preserving maximum usable tubing material. A multi-dimensional inspection system covers dimensional accuracy and service performance, ensuring that remanufactured tubing meets sealing and strength requirements. A carbon footprint model integrates process data to generate environmental benefit proof, providing a traceable technological path for the circular economy.

[0068] Specifically, during the manufacturing process, the carbon footprint monitoring module collects energy consumption data of the processing equipment through electricity meters and gas flow meters, and calculates the carbon emission intensity per unit product by combining the material cutting volume statistics. The energy consumption assessment module automatically adjusts the equipment operation mode to reduce energy consumption based on process parameter optimization suggestions.

[0069] In summary, this invention addresses the issues of corrosion and thin wall thickness in the recycling and reuse of used oil pipes by designing high-performance threaded joints. These joints ensure that the repaired pipe threaded joints meet the technical performance requirements of the pipe body, aligning with green manufacturing principles. The invention involves cleaning the used oil pipes of oil and rust, followed by flaw detection and hydrostatic testing. Only pipes meeting performance requirements are selected for threaded joint repair and remanufacturing. The recycled used oil pipes are then graded and evaluated before being applied to oil wells under different operating conditions. This technology will save oilfields a significant amount of money on the cost of purchasing new tubing, demonstrating good economic and social value. The use of circular arc or Bézier curve sealing effectively alleviates excessive stress concentration at both ends of the conical sealing surface, improving stress balance and fatigue life. The threads employ a self-locking design to prevent loosening and enhance connection safety. The integration of intelligent detection and assembly status assessment ensures consistency in the assembly process, enables carbon emission monitoring, aligns with energy conservation and environmental protection policies, and introduces tubing status identification, material traceability, and remanufacturing adaptability analysis systems to enhance intelligent manufacturing capabilities.

[0070] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0071] In the description of this application, it should be understood that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0072] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0073] Those skilled in the art to which this application pertains may make various modifications or additions to the specific embodiments described, or adopt similar methods to replace them, without departing from the spirit of this application or exceeding the scope defined by the appended claims.

Claims

1. A threaded joint structure for an oil pipe, comprising an oil pipe body and a coupling fastened to the oil pipe body by threads, characterized in that, The tubing body has an external thread, an external sealing surface, and an end face shoulder sequentially arranged at its end. The end face shoulder is located at the end of the tubing body with the external thread. The inner surfaces on both sides of the coupling have an internal thread, an internal sealing surface, and a torque shoulder sequentially arranged. Both the external thread and the internal thread are trapezoidal threads. The external sealing surface and the internal sealing surface are interference-fitted to form a sealing structure to prevent fluid leakage inside the tubing. The end face shoulder and the torque shoulder are mating.

2. The oil pipe threaded joint structure according to claim 1, characterized in that, The external thread at the top of the tubing body and the internal threads symmetrically arranged at both ends of the coupling both have a taper of 1:16, a pitch of 8 threads / inch, a bearing surface angle of -5° to 0°, and a guide surface angle of 10° to 15°. The external thread has a groove width of 1.5875 mm, a tooth width of 1.5875 mm, and a tooth height of 1 mm. The internal thread has a groove width of 1.613 mm, a tooth width of 1.5621 mm, and a tooth height of 1.2 mm.

3. The oil pipe threaded joint structure according to claim 1, characterized in that, The angle between the bearing surfaces of the external thread and the internal thread is a negative angle, forming a hook-shaped trapezoidal thread.

4. The oil pipe threaded joint structure according to claim 1, characterized in that, The interference fit between the outer sealing surface and the inner sealing surface is at least 0.2 mm, the length of the outer sealing surface is 5 mm, and the length of the inner sealing surface is 5 mm.

5. The oil pipe threaded joint structure according to claim 1, characterized in that, The outer sealing surface is provided with a circular arc protrusion, which is an elliptical structure, and its center position is 3mm away from the reference line of the external thread end face. The inner sealing surface is provided with a second circular arc protrusion, which is also an elliptical structure, and its center position is 1mm away from the internal thread end face. The major axis of the elliptical structure is 1mm, and the minor axis is 0.1-0.2mm.

6. The oil pipe threaded joint structure according to claim 1, characterized in that, The transition surface between the outer sealing surface and the end face shoulder is set as a curved profile, which is a Bézier curve or a circular arc; the transition surface between the inner sealing surface and the torque shoulder is set as a curved profile, which is a Bézier curve or a circular arc; the interference compression of both the outer sealing surface and the inner sealing surface is 0.3±0.05mm.

7. The oil pipe threaded joint structure according to claim 1, characterized in that, The shoulder angle of the external thread end face is 0° to -15°, and the shoulder angle of the internal thread torque is 0° to -15°.

8. A green remanufacturing method for waste oil pipes, characterized in that, Includes the following steps: S1. Provide waste oil pipes, which are waste oil pipes recovered from different areas of oil and gas fields and oil and gas wells; S2. Pre-treatment and information collection of waste oil pipes: Conduct a preliminary visual inspection of the recycled waste oil pipes and remove those that are obviously bent, broken or severely deformed; clean the surface of the oil pipes to remove oil, mud and other adhering substances. High-definition image acquisition using industrial cameras was used to obtain image information on pipe damage and corrosion morphology. S3. Intelligent identification and classification of oil pipe condition: Input the image collected in step S2 into the pre-trained convolutional neural network model to automatically identify the pipe damage level, corrosion pit depth, and crack orientation index; classify the oil pipe into three categories: A, B, and C according to the identification results; where category A is light wear and can be directly repaired, category B is moderate damage and requires machining, and category C is severe damage and cannot be remanufactured. S4. Environmentally friendly rust removal and surface treatment: For Class A and Class B oil pipes, use environmentally friendly rust remover for chemical spraying; use dry compressed air to dry or use low-temperature drying equipment to achieve drying; apply a phosphorus-free environmentally friendly coating for rust prevention pre-coating; S5. Thread repair and structural remanufacturing: For Class A oil pipes, laser cladding technology is used to repair the worn parts of the oil pipe, and wear-resistant alloy powder is clad to form a uniform and dense repair layer, and the thread structure is then reprocessed; For Class B oil pipes, the oil pipe end is cut off and the thread structure is reprocessed, wherein the thread structure is the external thread and internal thread in the oil pipe threaded joint structure as described in any one of claims 1-7. S6. Mechanical and airtight performance testing: Conduct thread size consistency and coaxiality tests on remanufactured tubing samples; perform airtightness tests, hydrostatic strength tests, and fatigue life tests; unqualified tubing is returned for repair or rejection. S7. Carbon Footprint Assessment and Digital Tracking: Record the remanufacturing process parameters and test data for each tubing; establish a carbon emission calculation model to comprehensively assess energy savings, material savings, and pollutant emission reduction; generate a unique tracking QR code to bind the identification data and carbon footprint record of each remanufactured tubing.

9. The green remanufacturing method for waste oil pipes according to claim 8, characterized in that, In step S5, for Class B tubing, the length of the tubing end to be cut is 80-120 mm.

10. The green remanufacturing method for waste oil pipes according to claim 8, characterized in that, After assembly, the sealing fit structure is monitored by an online monitoring system to detect the degree of interference sealing, assembly consistency, and thread preload status; the manufacturing process of the oil pipe thread connection structure adopts a carbon footprint monitoring and energy consumption assessment module.

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