High-temperature and high-pressure self-balancing air-tight sealing threaded connection structure

Abstract

The invention relates to the technical field of threads, and provides a high-temperature and high-pressure self-balancing air-tight sealing threaded connection structure which comprises two pipe fittings, the end of each pipe fitting is provided with a first threaded part and a second threaded part, the second threaded parts are arranged on the inner sides of the pipe fittings, the tooth bottoms of the first threaded parts are provided with nested threaded parts which are arranged in a protruding mode, and the nested threaded parts are arranged in the nested threaded parts. The peripheries of the adjacent ends of the two pipe fittings are sleeved with the coupling part, the third threaded parts are located at the two ends of the coupling part respectively and are in threaded connection with the first threaded parts of the pipe fittings, the tooth tops of the third threaded parts are provided with nested threaded grooves in threaded connection with the nested threaded parts, the sealing part is connected to the inner sides of the adjacent ends of the two pipe fittings, and the sealing part is provided with two sealing threaded parts; and the two sealing thread parts are respectively in threaded connection with the second thread parts of the two pipe fittings. The technical problem that in the prior art, thread deformation of a pipeline structure is generated due to thermal creep in the high-temperature and high-pressure environment, and consequently the thread structure is damaged is solved, and the fault rate of the pipeline structure in the high-temperature and high-pressure environment is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of threads, and in particular to a high-temperature and high-pressure self-balancing airtight threaded connection structure. Background Art

[0002] In the oil and gas industry, especially in high-temperature, high-pressure oil wells (such as deep and ultra-deep wells and steam injection thermal recovery wells), the reliability of pipe connection structures is directly related to production safety and efficiency. Traditional pipe connection methods, due to insufficient sealing performance, limited load-bearing capacity, and poor thermal creep resistance, are unable to adapt to the extreme environment of high temperature, high pressure, and severe corrosion within oil wells, becoming a key bottleneck restricting safe oil well production.

[0003] Early pipe connections mostly employed a single threaded structure (such as API standard round threads). The threaded mesh relied solely on metal-to-metal contact for sealing, lacking targeted leak prevention design. Under the pulsed impact of high-temperature, high-pressure gas-liquid mixed-phase flows (such as slug flows), thread gaps can easily expand due to pressure fluctuations, leading to leakage of the medium along the gaps. Data shows that the annual leakage rate of traditional threaded connections in steam injection wells exceeds 15%, not only wasting oil and gas resources but also potentially causing safety incidents such as wellhead explosions and environmental pollution. Furthermore, acidic media corroding the threads along the leakage path can further exacerbate seal failure, shorten maintenance cycles, and increase production costs.

[0004] Traditional coupling and pipe fitting design flaws make it difficult to balance the dual requirements of load bearing and sealing. For example, some structures utilize an interference fit for sealing performance, resulting in "seizure" of the threads during installation. Clearance fits, however, prioritize assembly convenience, can lead to plastic deformation and even fracture of the threads due to concentrated radial loads under high pressure. In thick-walled pipe connections, traditional designs are unable to effectively distribute axial loads (such as the deadweight of the pipe string and formation compression loads). Localized stress concentration on the threads can reach over 1.5 times the material's yield strength, easily leading to "debonding" accidents. These failures are costly to address in deep well mining.

[0005] Thermal creep is another core issue facing traditional connection structures. The long-term high temperatures of oil wells can cause slow plastic deformation of threaded materials (such as 4130 steel), shortening the thread profile and lengthening the pitch. Due to the lack of compensation in traditional structures, two extreme situations can easily occur: first, there is no reserved clearance in the sealing section, causing the threads to become "stuck" after creep, making it impossible to disassemble during well repairs; second, the load-bearing section is too loose, and the preload is relaxed after creep, increasing the thread meshing gap and losing both sealing and load-bearing capacity.

[0006] Furthermore, traditional structures lack sealing redundancy and ignore the impact of fluid flow on connections. When the primary seal (the coupling and the external thread of the pipe fitting) fails due to corrosion or creep, the lack of a secondary sealing barrier allows the medium to leak directly out of the pipe. Furthermore, in some connection structures, the seals and the inner diameters of the pipe fittings are inconsistent, causing turbulence as the fluid passes through. This exacerbates the erosion of the connection by high-speed, sand-carrying fluids, further shortening service life. In asymmetric connection designs, the additional stress generated by the difference in thermal expansion coefficients between the pipe fitting and the coupling can also lead to eccentric loading of the threads, accelerating localized wear and fracture. Summary of the Invention

[0007] To overcome the above-mentioned defects, an embodiment of the present invention provides a high-temperature and high-pressure self-balancing air-sealed threaded connection structure, which solves the technical problem in the prior art that the pipeline structure in a high-temperature and high-pressure environment produces thread deformation due to thermal creep, causing damage to the thread structure.

[0008] According to one aspect, at least one embodiment of the present invention provides a high-temperature and high-pressure self-balancing airtight threaded connection structure, comprising: A pipe fitting, wherein there are two pipe fittings, each end of the pipe fitting has a first threaded portion and a second threaded portion, the first threaded portion is arranged on the outside of the pipe fitting, the second threaded portion is arranged on the inside of the pipe fitting, and the bottom of the first threaded portion has a protruding nested threaded portion; A coupling member, the coupling member being sleeved on the outer circumference of the adjacent ends of the two pipe fittings, the coupling member having two third threaded portions, the third threaded portions being located at both ends of the coupling member and being threadedly connected to the first threaded portions of the two pipe fittings, respectively, the top portion of the third threaded portion having a nested thread groove threadedly connected to the nested threaded portion; A sealing member is connected to the inner sides of adjacent ends of the two pipes. The sealing member has two sealing threaded portions, and the two sealing threaded portions are respectively threadedly connected to the second threaded portions of the two pipes.

[0009] As a further technical solution, the third threaded portion has a load-bearing section and a sealing section. The load-bearing section is located at the end of the coupling and transitionally fits with the first threaded portion. The sealing section has a clearance fit with the first threaded portion. The sealing section can produce expansion deformation under high temperature and high pressure environment to seal between the pipe fitting and the coupling.

[0010] As a further technical solution, the first threaded portion and the third threaded portion are both serrated threads, and a first expansion gap extending helically is formed between the sealing section and the first threaded portion. The first expansion gap has an expansion load section, an expansion abutment section, and a creep give-way section that are interconnected and arranged in sequence. The first expansion gap is used to give way to the straight-side expansion of the first threaded portion, the expansion abutment section is used to abut against the top portion of the expanded and deformed first threaded portion, and the creep give-way section is used to give way to the oblique-side expansion of the first threaded portion. The width of the expansion load section is smaller than the width of the creep give-way section.

[0011] As a further technical solution, the nested threaded portion has a first sealing surface and a second sealing surface, the angle between the first sealing surface and the tooth bottom of the first threaded portion is greater than the angle between the second sealing surface and the tooth bottom of the first threaded portion, and the first sealing surface is close to the inclined surface of the first threaded portion.

[0012] As a further technical solution, the top of the third threaded portion has a first abutment portion and a second abutment portion respectively located on the upper and lower sides of the nested thread groove, the first abutment portion is close to the first sealing surface, and the length of the first abutment portion and the bottom of the third threaded portion is greater than the length of the second abutment portion and the bottom of the third threaded portion.

[0013] As a further technical solution, a thermal expansion sealing groove is provided between the nested thread portion and the nested thread groove, and the nested thread portion can expand after being heated to fill the thermal expansion sealing groove.

[0014] As a further technical solution, a first communicating groove is formed between the first abutting portion and the tooth bottom of the first threaded portion, and the two ends of the first communicating groove are respectively connected to the thermal expansion sealing groove and the creep yielding section. A second communicating groove is provided between the second abutting portion and the tooth bottom of the first threaded portion, and the two ends of the second communicating groove are respectively connected to the thermal expansion sealing groove and the expansion load section.

[0015] As a further technical solution, the width of the first communicating groove is greater than that of the second communicating groove, and the width of the thermal expansion sealing groove is greater than that of the first communicating groove.

[0016] As a further technical solution, the thermal expansion sealing groove comprises a first sealing groove and a second sealing groove that are connected to each other, and the width of the first sealing groove is greater than the width of the second sealing groove.

[0017] As a further technical solution, the second threaded portion and the sealing threaded portion are both rectangular threads and are transition fit. The second threaded portion has an annular mounting groove. There are a plurality of annular mounting grooves arranged along the axial direction of the second threaded portion. The high-temperature and high-pressure self-balancing airtight sealing threaded connection structure further includes: An annular seal has a fourth threaded portion, the fourth threaded portion is smoothly connected to the second threaded portion, and the fourth threaded portion is transitionally matched with the sealing threaded portion.

[0018] The beneficial effects of the present invention are: In the present invention, long-term high temperature of oil wells will cause creep of threaded materials. Before thermal creep: the load-bearing section and the first threaded portion are transitionally matched to bear the weight of the pipe string, the formation extrusion load and the axial force of the high-pressure fluid, and at the same time, the initial seal is achieved through tight engagement, avoiding leakage caused by gaps in the early stage of installation; during thermal creep, as the high-temperature service time increases, the threaded material undergoes slow plastic deformation. At this time, the sealing section can accommodate the deformation caused by creep due to the reserved gap, avoiding "seizing" or breaking of the thread; at the same time, thermal expansion reduces the gap in the sealing section, increases the contact pressure of the thread tooth surface, strengthens the sealing effect, and reduces pressure leakage caused by creep relaxation.

[0019] The sealing thread of the seal mates with the second thread of the pipe, further optimizing stress distribution and reducing thread creep through thermal expansion. In high-temperature environments, the sealing thread expands as the temperature rises, reducing the clearance between the threads and the second thread, creating a tighter interference fit. The radial pressure generated by this expansion is evenly distributed across the entire threaded engagement surface. Simultaneously, the high-pressure fluid places significant radial forces on the inner wall of the pipe, which can easily cause the pipe to elastically expand outward, "stretching" the pitch of the second thread. The expansion of the sealing thread offsets some of this expansion, maintaining thread engagement stability and minimizing "misalignment" caused by pitch deviation, thereby reducing the additional shear force on the threads and slowing the creep process.

[0020] The overall symmetrical structure can alleviate the additional stress caused by the difference in thermal expansion coefficient of different components, reduce the uneven creep caused by local overheating, and thus reduce the occurrence of preload relaxation and thread overload. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly describes the drawings required for describing the embodiments of the present invention. Obviously, the drawings described below are merely exemplary embodiments of the present invention. Those skilled in the art can, without inventive effort, derive other drawings based on the contents of the exemplary embodiments of the present invention and these drawings.

[0022] Figure 1 A schematic structural diagram of an embodiment of the present invention; Figure 2 for Figure 1 A schematic structural diagram of the upper half of an embodiment of the present invention; Figure 3 for Figure 2 Schematic diagram of the enlarged structure of A in the middle; Figure 4 for Figure 3 Schematic diagram of the enlarged structure of B.

[0023] In the figure: pipe fitting 1, first threaded portion 101, second threaded portion 102, nested threaded portion 103, first expansion gap 104, expansion load section 105, expansion abutment section 106, creep yield section 107, first sealing surface 108, second sealing surface 109, annular mounting groove 110, coupling 2, third threaded portion 201, nested threaded groove 202, load section 203, sealing section 204, first abutment section 205, second abutment section 206, thermal expansion sealing groove 207, first connecting groove 208, first sealing groove 209, second sealing groove 210, second connecting groove 211, seal 3, sealing threaded portion 301, annular seal 4, fourth threaded portion 401. DETAILED DESCRIPTION The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention.

[0024] To simplify the drawings, only portions relevant to the invention are schematically depicted in each figure; they do not represent the actual structure of the product. Furthermore, to simplify the drawings and facilitate understanding, in some figures, only one component with the same structure or function is schematically depicted or labeled. In this document, "one" not only means "only one" but also "more than one," and "several" includes "two" and "more than two."

[0025] It should be noted that, unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they can refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0026] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0027] In the description of this embodiment, the terms "up", "down", "left", "right", etc., and the orientation or position relationship are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be understood as a limitation on the present invention.

[0028] In addition, in the description of the present application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0029] like Figures 1 to 4 As shown, it shows a high-temperature and high-pressure self-balancing air-sealed threaded connection structure in one embodiment of the present invention.

[0030] In some examples, the pipe fitting 1 is the basic component of the connection structure, and several pipe fittings 1 are arranged in sequence along the axial direction. The two first threaded portions 101 symmetrically arranged on the outside of the two ends form a connection with the third threaded portions 201 at the two ends of the coupling 2. The nested threaded portion 103 at the bottom of the first threaded portion 101 can engage with the nested threaded groove 202 at the top of the third threaded portion 201 of the coupling 2. This nested structure can further enhance the tightness of the connection under high temperature and high pressure, and effectively prevent the threaded connection from loosening or leaking due to changes in ambient temperature. At the same time, the two second threaded portions 102 symmetrically arranged on the inside of the two ends of the pipe fitting 1 are used to connect with the sealing threaded portion 301 of the seal 3. This connection can further enhance the sealing effect of the entire structure and ensure that the high-temperature and high-pressure medium in the oil well will not leak from the connection part.

[0031] The two third threaded portions 201 of the coupling 2 serve as internal threads and are respectively threadedly connected to the first threaded portions 101 of the two adjacent pipe fittings 1, thereby connecting the adjacent pipe fittings 1. The load-bearing section 203 of the third threaded portion 201 is located at the end of the coupling 2 and transitionally fits with the first threaded portion 101. This fit can effectively withstand the axial and radial loads within the oil well, ensuring the stability and load-bearing capacity of the connection structure under high-pressure environments. The sealing section 204 is loosely fitted with the first threaded portion 101. Under high-temperature and high-pressure environments, due to the thermal expansion and contraction characteristics of the material, the gap will gradually decrease or even disappear, thereby forming a good sealing effect and preventing leakage of high-temperature and high-pressure oil and gas media.

[0032] The two sealing threads 301 of the seal 3 are threadedly connected to the second threaded portions 102 of two adjacent pipe fittings 1, further enhancing the sealing performance of the overall structure. Furthermore, the inner diameter of the seal 3 is equal to that of the pipe fitting 1. This design ensures smooth oil flow within the pipeline, avoiding turbulence and pressure loss caused by inconsistent inner diameters. It also reduces erosion and corrosion of the connection points by the medium.

[0033] In high-temperature, high-pressure oil wells, formation fluids (including acidic gases and high-temperature steam) easily penetrate through the thread gaps. The nested threaded portion 103 (the root of the first threaded portion 101 of the pipe fitting 1) and the nested thread groove 202 (the crest of the third threaded portion 201 of the coupling 2) form multiple sealing interfaces through interlocking teeth. This tight nesting of the two extends the leakage path, forcing high-temperature, high-pressure fluids to penetrate multiple thread engagement barriers, significantly increasing leakage resistance. This reduces transient leakage, particularly during pulsed impacts of gas-liquid mixed-phase flow (such as slug flow). When temperature fluctuations (such as the 200-300°C fluctuations in steam injection production) cause threads to expand and contract, the nested structure compensates for gaps by aligning the tooth surfaces, avoiding leakage paths caused by loosening of conventional threads. This adapts to the frequent temperature fluctuations in oil wells. Furthermore, the nested structure increases the thread engagement contact area in high-temperature, high-pressure environments, improving the connection's pullout and torque resistance. It effectively distributes axial and radial forces under high pressure and reduces localized stress concentration on the threads.

[0034] To prevent trace leakage of the main seal (connection between coupling 2 and pipe 1) in oil wells due to thermal creep and corrosion, seal 3 forms "internal redundant protection": the sealing threaded portion 301 of seal 3 is connected to the second threaded portion 102 of pipe 1, forming an independent sealing cavity inside the pipe. When the sealing section 204 of coupling 2 leaks due to hydrogen sulfide corrosion or thermal deformation, it can block the fluid from diffusing out of the pipe, avoiding wellhead leakage or further corrosion of the pipe string by acidic media; the inner diameter of seal 3 is consistent with that of pipe 1, and does not interfere with the flow of high-pressure fluid (such as sand-laden crude oil). At the same time, it maintains structural stability under high pressure difference, prevents deformation due to fluid impact, and adapts to the harsh environment of high flow rate and high sand content in oil wells.

[0035] Long-term high temperatures in oil wells (such as 250°C in steam injection wells) can cause creep of the threaded material (for example, the thread profile of 4130 steel becomes "shorter"). Before thermal creep: the third threaded portion 201 has a load-bearing section 203 and a sealing section 204. The load-bearing section 203 is located at the end of the coupling 2 and transitionally fits with the first threaded portion 101. The load-bearing section 203 transitionally fits with the first threaded portion 101, bearing the weight of the tubing string, the formation extrusion load, and the axial force of the high-pressure fluid. At the same time, initial sealing is achieved through tight engagement, avoiding leakage caused by gaps in the early stages of installation. During thermal creep, as the high-temperature service time increases, the threaded material undergoes slow plastic deformation. At this time, the sealing section 204 (which is in a clearance fit with the first threaded portion 101) can accommodate the deformation caused by creep due to the reserved gap, avoiding "seizure" or breakage of the thread. At the same time, thermal expansion reduces the gap in the sealing section 204, increasing the contact pressure on the thread tooth surface, enhancing the sealing effect, and reducing pressure leakage caused by creep relaxation.

[0036] The sealing threaded portion 301 of the seal 3 mates with the second threaded portion 102 of the pipe fitting 1. Under high temperatures, the seal 3 thermally expands, distributing the stress on the pipe fitting 1 across the seal 3, thereby optimizing stress distribution and reducing thread creep. Under high temperatures, the sealing threaded portion 301 expands as the temperature rises, reducing the thread engagement clearance with the second threaded portion 102 and forming a tighter interference fit. This expansion generates radial pressure that is evenly distributed across the entire threaded engagement surface. Simultaneously, the high-pressure fluid exerts significant radial force on the inner wall of the pipe, potentially causing the pipe fitting 1 to elastically expand outward. Due to thermal creep, the pitch of the second threaded portion 102 "stretches" as the temperature drops. The expansion of the sealing threaded portion 301, under stress, partially offsets this axial expansion, maintaining thread engagement stability and minimizing "misalignment" caused by pitch deviation. This reduces the additional shear force on the threads and slows down creep.

[0037] The overall symmetrical structure (symmetrical threads at both ends of the pipe fitting 1 and symmetrical connection of the coupling 2) can alleviate the additional stress caused by the difference in thermal expansion coefficients of different components (such as the pipe fitting and the coupling), reduce the uneven creep caused by local overheating, and thus reduce the occurrence of preload relaxation and thread eccentric loading.

[0038] Furthermore, in the high-temperature and high-pressure environment of oil wells, both the first threaded portion 101 and the third threaded portion 201 adopt serrated threads. The tooth profile of this thread form is asymmetrical, with a steeper straight edge on one side and a flatter bevel on the other side. It can more effectively disperse the force when bearing axial loads and enhance the anti-loosening ability of the connection. It is very suitable for oil wells, which need to withstand high pressure and vibration for a long time.

[0039] During the production process, a spiral-shaped first expansion gap 104 is formed between the third threaded portion 201 and the first threaded portion 101 by removing material from either the third threaded portion 201 or the first threaded portion 101. This gap is designed to accommodate thermal expansion in high-temperature and high-pressure environments. First expansion gap 104 consists of an interconnected and sequentially arranged expansion load section 105, expansion abutment section 106, and creep relief section 107. Each section has a distinct function, collectively ensuring the sealing and structural integrity of the threaded connection in extreme environments.

[0040] When the temperature inside an oil well rises, the first threaded portion 101 of the pipe fitting 1 deforms due to thermal expansion. The expansion-loading section 105 is relatively shallow and primarily serves to accommodate the initial expansion of the straight edge of the first threaded portion 101. During the initial temperature rise, the expansion of the straight edge is relatively small, and the space provided by the expansion-loading section 105 mitigates the resulting pressure. Furthermore, the contact force between the threads partially absorbs the load, preventing damage to the threads due to localized excessive stress.

[0041] As the temperature continues to rise, the expansion gradually increases, and the top of the first threaded portion 101 undergoes significant expansion and deformation. This is when the expansion abutment section 106 begins to function. By abutting against the top of the thread, it limits excessive expansion and, using the pressure generated by the abutment, enhances the sealing effect between the threads, preventing leakage of high-temperature, high-pressure media from the gap.

[0042] The creep clearance section 107 is deep, primarily to accommodate the expansion of the beveled edge of the first threaded portion 101. Under prolonged high-temperature conditions, the material will creep, and the creep expansion of the beveled edge requires more space to release stress. The ample space provided by the creep clearance section 107 effectively prevents plastic deformation or cracks caused by the restricted expansion of the beveled edge, ensuring the long-term stability of the threaded connection.

[0043] At the same time, the bevel of the first threaded portion 101 itself is composed of a relatively large proportion of material, which gives it a greater potential for deformation during temperature changes. However, because the creep yielding section 107 provides ample space, the deformation of the bevel can be fully released within this area, with little or no contact with other structures. This design effectively prevents the deformation of the bevel from being transferred to the sealing section 204, thereby ensuring that the deformation of the sealing section 204 is relatively small during temperature changes. As the key part for achieving high-temperature and high-pressure sealing after creep deformation, the smaller deformation of the sealing section 204 allows it to always maintain a relatively stable fit, which is conducive to maintaining the initial sealing effect.

[0044] When the material is exposed to high temperatures for a long time, causing creep deformation, the bevel of the first threaded portion 101 will undergo a certain amount of creep expansion. At this time, the creep clearance section 107 will gradually become thinner under the action of tension. This thinning phenomenon does not indicate structural damage. Instead, it will further reduce the gap between the creep clearance section 107 and the bevel, forming a tighter fit. At the same time, since the bevel has less contact with other structures, the stress generated by its creep mainly acts on the wall of the creep clearance section 107, causing this area to fit more closely with the bevel, thereby improving the overall sealing of the threaded connection and effectively preventing the leakage of high-temperature and high-pressure oil and gas media.

[0045] This design utilizes the interaction between the properties of the material and the structure. Under the conditions of temperature changes and long-term creep, it can not only protect the stability of the sealing section 204 through the yielding function of the creep yielding section 107, but also enhance the sealing performance with the help of the structural changes brought about by creep, so that the entire connection structure has better long-term working performance in the high-temperature and high-pressure oil well environment.

[0046] This three-stage expansion gap, combined with the structural characteristics of the serrated thread, allows the first threaded portion 101 and the third threaded portion 201 to freely release expansion stress under high temperature and high pressure, and to achieve dynamic sealing and load balance through the synergistic action of each section, further improving the reliability of the entire connection structure in the extreme environment of oil wells.

[0047] Furthermore, the nested threaded portion 103 serves as a sealing unit that cooperates with the first threaded portion 101 and the nested threaded groove 202 of the coupling 2. The angle design and position distribution of the first sealing surface 108 and the second sealing surface 109 of the nested threaded portion 103 form a stepped sealing barrier under the high temperature and high pressure environment of the oil well, thereby improving the leakage resistance of the threaded connection.

[0048] From the perspective of structural characteristics, the angle between the first sealing surface 108 and the root of the first threaded portion 101 is greater than the angle between the second sealing surface 109 and the root of the thread, and the first sealing surface 108 is adjacent to the inclined surface of the first threaded portion 101 (i.e., the hypotenuse of the serrated thread). The reason for this angular difference and position layout is that it is close to the inclined surface and has a larger angle. When the thread is tightened and in a high temperature and high pressure environment, the first sealing surface 108 will first form a tight fit with the corresponding surface of the nested thread groove 202. The large angle design enables it to generate greater sealing contact pressure when it is subjected to axial load and radial expansion force, and the contact area is wider, which can quickly block the penetration path of high-pressure oil and gas. At the same time, its position close to the inclined surface can directly bear the radial thrust generated by the thermal expansion of the first threaded portion 101, converting the expansion force into sealing pressure, thereby enhancing the main sealing effect.

[0049] The smaller angle of the second sealing surface 109 creates a second sealing edge. After the first sealing surface 108 achieves a preliminary seal, the second sealing surface 109 forms a secondary contact with the inner wall of the nested thread groove 202. This design offers the advantage that when high temperatures cause material creep or vibrations cause minor displacements, the second sealing surface 109 can fill any resulting minor gaps through its own angular properties, creating a compensating seal. Furthermore, the small angle creates a higher contact stress for the same amount of expansion, providing a secondary barrier to any trace amounts of media not completely blocked by the first sealing surface 108.

[0050] In the high-temperature, high-pressure environment of oil wells, when rising temperatures cause the first threaded portion 101 to expand, the first sealing surface 108, due to its large angle and advantageous position, is the first to enhance the seal through expansion force. If long-term creep occurs, the second sealing surface 109, leveraging the stress concentration characteristics of its small angle, continuously maintains the seal to compensate for the gap. This design enables the nested threaded portion 103 to withstand instantaneous high-pressure shocks in extreme environments while also adapting to long-term changes in material properties, providing a stable and reliable seal for the entire threaded connection.

[0051] Furthermore, the first abutment portion 205 and the second abutment portion 206 provided at the top of the third threaded portion 201 cooperate with the first sealing surface 108 and the second sealing surface 109 of the nested threaded portion 103, further improving the sealing performance and structural stability of the threaded connection in the high-temperature and high-pressure oil well environment.

[0052] The first abutment portion 205 is located close to the first sealing surface 108. When the first threaded portion 101 and the third threaded portion 201 are threadedly connected, the first abutment portion 205 contacts the first sealing surface 108. The length between the first abutment portion 205 and the root of the third threaded portion 201 is greater than the length between the second abutment portion 206 and the root of the third threaded portion 201. This length difference is designed based on the functions and stresses they bear.

[0053] Because the first sealing surface 108 is close to the inclined surface of the first threaded portion 101 and has a large angle with the root of the thread, the pressure on the first sealing surface 108 is relatively large in a high-temperature and high-pressure environment. The longer length of the first abutment portion 205 provides more stable and sufficient support for the first sealing surface 108, ensuring that the first sealing surface 108 and the first abutment portion 205 always maintain close contact under pressure, effectively preventing the penetration of high-temperature and high-pressure media. The longer length also increases the contact area between the two, disperses the contact pressure, avoids damage to the sealing surface due to excessive local pressure, and extends the service life of the sealing structure.

[0054] The second abutment portion 206 corresponds to the second sealing surface 109 and is relatively short in length relative to the root of the third threaded portion 201. This is because the second sealing surface 109 has a relatively small angle with the root, primarily performing a secondary sealing function and subjecting it to relatively low pressure. This shorter length allows the second abutment portion 206 to form a tighter fit with the second sealing surface 109, effectively sealing and effectively intercepting media not fully blocked by the first sealing surface 108.

[0055] The cooperation between the first abutment portion 205 and the second abutment portion 206 and the first sealing surface 108 and the second sealing surface 109 can adapt to the thermal expansion and contraction and creep of the material. Through the stable support of the first abutment portion 205 and the close fit of the second abutment portion 206, the sealing performance of the entire threaded connection is ensured to always remain in good condition, providing protection for the safe exploitation of oil wells.

[0056] Furthermore, a thermal expansion seal groove 207 is provided between the nested threaded portion 103 and the nested thread groove 202. This structural design further enhances the sealing effect in high-temperature environments. At room temperature, the thermal expansion seal groove 207 provides sufficient space for the nested threaded portion 103, without affecting the normal connection and fit of the components. However, when exposed to the high-temperature environment of an oil well, the nested threaded portion 103 expands due to the rising temperature, and its expanded volume fills the thermal expansion seal groove 207. This filling action completely eliminates the gap between the nested threaded portion 103 and the nested thread groove 202, forming an additional sealing barrier and effectively preventing high-temperature and high-pressure oil and gas media from leaking through the tiny gap between them. Furthermore, filling the thermal expansion seal groove 207 strengthens the overall connection strength between the nested threaded portion 103 and the nested thread groove 202, ensuring a more secure fit under high-temperature and high-pressure conditions, further enhancing the stability and reliability of the entire threaded connection structure.

[0057] Furthermore, the first connecting groove 208 formed between the first abutting portion 205 and the tooth bottom of the first threaded portion 101, and the second connecting groove 211 between the second abutting portion 206 and the tooth bottom of the first threaded portion 101, play a connecting and synergistic role in the sealing and stress adjustment of the entire structure.

[0058] The two ends of the first connecting groove 208 are connected to the thermal expansion seal groove 207 and the creep relief section 107, respectively. In a high-temperature environment, when the nested threaded portion 103 expands and fills the thermal expansion seal groove 207, a certain amount of pressure is generated. The first connecting groove 208 can provide a channel for this pressure to flow to the creep relief section 107. The creep relief section 107 itself provides space for the expansion and creep of the bevel of the first threaded portion 101. It has a certain stress dissipation and absorption capacity, which can absorb the pressure from the first connecting groove 208, preventing excessive pressure in the thermal expansion seal groove 207 from affecting the sealing effect, while also reducing the erosion of the sealing surface by the medium.

[0059] The two ends of the second connecting groove 211 communicate with the thermal expansion seal groove 207 and the expansion load section 105, respectively. When the thermal expansion seal groove 207 is filled, the second connecting groove 211 transfers some of the pressure within the thermal expansion seal groove 207 to the expansion load section 105. The expansion load section 105, in conjunction with the first threaded portion 101, has a certain load-bearing capacity, capable of withstanding this pressure and distributing it throughout the entire connection structure, thus avoiding localized pressure concentration. This pressure transfer also promotes a tighter fit between the expansion load section 105 and the first threaded portion 101, indirectly improving sealing performance.

[0060] The design of these two connecting grooves enables the thermal expansion sealing groove 207, the creep yielding section 107 and the expansion load section 105 to form an interconnected whole, thereby achieving reasonable pressure distribution and effective medium drainage, further enhancing the adaptability and reliability of the threaded connection structure in the high-temperature and high-pressure oil well environment.

[0061] Furthermore, the width of the thermal expansion sealing groove 207 is greater than that of the first connecting groove 208, and the width of the second connecting groove 211 is less than that of the thermal expansion sealing groove 207. The thermal expansion sealing groove 207 needs to provide sufficient space for the expansion of the nested threaded portion 103 at high temperatures. The deeper width ensures its capacity, ensuring that the nested threaded portion 103 can fully fill the groove after expansion to form an effective seal. The first connecting groove 208 is smaller than the width of the thermal expansion sealing groove 207, which can form a certain pressure gradient during the drainage process, prompting pressure and media to flow toward the creep yield section 107. The smaller width of the second connecting groove 211 can better control the intensity of pressure transmission, prevent excessive pressure from suddenly acting on the expansion load section 105, and ensure stable stress on the structure.

[0062] Furthermore, the thermal expansion seal groove 207 includes a first sealing groove 209 and a second sealing groove 210 that are interconnected, with the width of the first sealing groove 209 being greater than that of the second sealing groove 210. This width difference design is compatible with the expansion characteristics of the nested threaded portion 103. Under high temperature conditions, different areas of the nested threaded portion 103 expand differently. The thicker width of the first sealing groove 209 provides ample space for the area with greater expansion, ensuring that this area can fully fill the groove body to form a tight seal. The smaller width of the second sealing groove 210 can cooperate with the area with relatively less expansion, forming a tighter fit after filling, further enhancing the overall sealing effect. At the same time, the interconnectedness of the two allows the expansion force of the nested threaded portion 103 to be more evenly distributed within the thermal expansion seal groove 207, avoiding localized excessive pressure that could lead to seal failure, thereby improving the sealing reliability of the thermal expansion seal groove 207 in high temperature and high pressure environments.

[0063] Furthermore, both the second threaded portion 102 and the sealing threaded portion 301 are designed with rectangular threads and are transition fit. Rectangular threads have the characteristics of rectangular tooth profile, high strength, and high transmission efficiency. In the high-temperature and high-pressure oil well environment, this thread form can better withstand axial forces and ensure the stability of the connection between the second threaded portion 102 and the sealing threaded portion 301. The transition fit allows a certain amount of interference between the two to ensure a tight connection, but does not cause installation difficulties or thread damage due to excessive interference, which is conducive to maintaining good sealing performance under high temperature and high pressure. In steam injection mining or high-pressure gas lift scenarios, its high strength characteristics can reduce the plastic deformation of the thread teeth due to stress concentration, avoid pitch deviation caused by creep, and ensure long-term connection stability. At the same time, the rectangular thread has high transmission efficiency, which can reduce friction resistance during installation, adapt to the needs of frequent disassembly and assembly at the oil well site, and reduce the risk of thread "seizure" during assembly. In high-temperature environments, the deformation of the two parts caused by thermal expansion can be compensated by the interference, avoiding sealing failure caused by expansion of the clearance fit. At the same time, the thread will not "crack" due to excessive interference, which is suitable for working conditions where the oil well temperature fluctuates frequently.

[0064] The second threaded portion 102 is also provided with an annular mounting groove 110. The high-temperature and high-pressure self-balancing air-sealing threaded connection structure is equipped with an annular seal 4. The annular seal 4 is a rubber component. The annular seal 4 has a fourth threaded portion 401. The fourth threaded portion 401 is smoothly connected to the second threaded portion 102 and transitionally matched with the sealing threaded portion 301. The annular mounting groove 110 provides precise positioning for the installation of the annular seal 4, ensuring that it will not be displaced during operation. The smooth connection between the fourth threaded portion 401 and the second threaded portion 102 avoids stress concentration in the threaded connection area. At the same time, the transitional match with the sealing threaded portion 301 further enhances the sealing effect of this area, and forms a double sealing guarantee with the second threaded portion 102 and the sealing threaded portion 301, effectively preventing the leakage of high-temperature and high-pressure oil and gas media, and improving the sealing reliability of the entire connection structure.

[0065] The transitional fit between the fourth threaded portion 401 and the sealing threaded portion 301 creates a "secondary meshing seal," in addition to the primary seal between the second threaded portion 102 and the sealing threaded portion 301. If a slight gap develops in the primary seal due to thermal creep, the fourth threaded portion 401's tight engagement blocks media penetration. Combined with the large contact area of ​​the rectangular threads, this creates a "double barrier," significantly reducing leakage.

[0066] At high temperatures, the second threaded portion 102 is prone to problems such as pitch elongation and tooth profile distortion due to material creep. The annular mounting groove 110, as an annular groove structure on the second threaded portion 102, can alleviate stress concentration in the following ways: the mounting groove divides the continuous thread structure of the second threaded portion 102 into "two sections", so that the axial stress generated by thermal creep forms a "stress release node" at the groove body, avoiding the accumulation of stress along the entire length of the thread and causing overall deformation. The spatial structure of the groove body provides a tiny deformation buffer space for the threaded portion. When the thread expands or creeps outward due to high temperature, the mounting groove can accommodate part of the deformation increment, reducing excessive extrusion of the thread crest and the sealing threaded portion 301, thereby reducing the risk of tooth profile deformation. This design is particularly suitable for scenarios with frequent temperature fluctuations such as steam injection mining, and can reduce thread fatigue deformation caused by alternating thermal expansion and contraction.

[0067] The tight fit between the annular mounting groove 110 and the annular seal 4 forms a "stress conduction path": when the second threaded portion 102 generates radial or axial stress due to thermal creep, the inner wall of the mounting groove transfers some of this stress to the annular seal 4 embedded therein. Because the annular seal 4 transitions with the sealing threaded portion 301 via the fourth threaded portion 401, its flexible structure acts as a "stress carrier," relieving the load of the second threaded portion 102. The stress transferred to the annular seal 4 is converted into contact pressure between it, the mounting groove, and the sealing threaded portion 301. This pressure can further increase with thermal expansion at high temperatures, thereby enhancing the tightness of the engagement between the annular seal 4 and the threads, dispersing stress while improving sealing redundancy.

[0068] The rectangular threads and transition fit between the second threaded portion 102 and the sealing threaded portion 301 address axial load-bearing and basic sealing issues under high temperature and high pressure. The positioning of the annular seal 4 through the annular mounting groove 110 and the dual engagement of the fourth threaded portion 401 further enhance sealing redundancy and structural stability. These three elements work together to form an integrated design that combines high load-bearing capacity with dual sealing and thermal shock resistance. This design is suitable for the extreme environments of high temperature, high pressure, severe corrosion, and high vibration found in oil wells, effectively extending the service life of the threaded connection and reducing safety risks such as wellhead leakage and tubing failure.

[0069] Furthermore, multiple axially arranged annular mounting grooves 110 divide the continuous thread structure of the second threaded portion 102 into multiple independent load-bearing units. During high-temperature creep, the creep stress of each thread segment is "intercepted" by the adjacent mounting grooves, preventing continuous axial stress accumulation. For example, three mounting grooves can divide the threaded portion into two independent areas, with each segment experiencing only half the creep deformation of the overall structure, significantly reducing the risk of thread collapse or pitch deviation due to excessive deformation.

[0070] At the same time, each mounting groove transmits part of the stress through the annular seal 4, distributing the load to multiple annular seals 4, avoiding failure of a single annular seal 4 due to stress overload, and adapting to the continuous load conditions under long-term high temperature and high pressure of oil wells.

[0071] Multiple annular seals 4 are mounted corresponding to the plurality of annular mounting grooves 110, forming a serial array along the axial direction of the second threaded portion 102. When high-pressure oil and gas penetrate, they must sequentially penetrate the mating interface between the fourth threaded portion 401 and the sealing threaded portion 301 of the multi-stage annular seal 4, significantly extending the leakage path.

[0072] Even if a certain stage of sealing has a slight gap due to local corrosion or creep, the subsequent annular seal 4 can still block the diffusion of the medium. Compared with the single-stage seal, its leakage rate can be reduced, which is especially suitable for dynamic sealing scenarios under the impact of gas-liquid mixed phase flow.

[0073] The multiple axially arranged mounting grooves provide multi-point rigid support for the second threaded portion 102. In the vibration environment of oil well operations, the multi-point constraint can reduce radial swing of the threaded portion and avoid the expansion of the thread engagement gap caused by vibration.

[0074] At the same time, the multi-groove design reduces the impact of the installation deviation of a single annular seal 4. Even if a certain annular seal 4 is slightly deflected due to assembly error, the remaining annular seals 4 can still ensure the overall sealing performance, improve the fault tolerance of on-site assembly, and adapt to the installation requirements under complex working conditions of oil wells.

[0075] Deep oil wells experience axial temperature gradients, leading to differences in thermal expansion between threads of varying widths. Multiple axially arranged mounting grooves adapt to changing sealing requirements caused by temperature gradients by corresponding to the differential deformation of the annular seal 4, thus preventing single seals from failing due to overtightening or leaking due to loosening in areas with large temperature differences. This further enhances the structural stability and sealing reliability of the second threaded portion 102 in high-temperature, high-pressure oil well environments, providing comprehensive protection for threaded connections under extreme operating conditions.

[0076] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. High temperature and high pressure self-balancing airtight threaded connection structure, characterized in that: include: A pipe fitting (1), wherein there are two pipe fittings (1), each end of the pipe fitting (1) has a first threaded portion (101) and a second threaded portion (102), the first threaded portion (101) is arranged on the outside of the pipe fitting (1), the second threaded portion (102) is arranged on the inside of the pipe fitting (1), and the bottom of the first threaded portion (101) has a protruding nested threaded portion (103); A coupling member (2), the coupling member (2) being sleeved on the outer peripheries of adjacent ends of the two pipe members (1), the coupling member (2) having two third threaded portions (201), the third threaded portions (201) being respectively located at two ends of the coupling member (2) and being respectively threadedly connected to the first threaded portions (101) of the two pipe members (1), the top portion of the third threaded portion (201) having a nested thread groove (202) threadedly connected to the nested threaded portion (103); The sealing member (3) is connected to the inner sides of adjacent ends of the two pipe fittings (1), and the sealing member (3) has two sealing threaded portions (301). The two sealing threaded portions (301) are respectively threadedly connected to the second threaded portions (102) of the two pipe fittings (1).

2. The high-temperature and high-pressure self-balancing airtight threaded connection structure according to claim 1, characterized in that: The third threaded portion (201) comprises a load-bearing section (203) and a sealing section (204); the load-bearing section (203) is located at the end of the coupling member (2) and is transitionally matched with the first threaded portion (101); the sealing section (204) is clearance-matched with the first threaded portion (101); the sealing section (204) is capable of generating expansion deformation under a high-temperature and high-pressure environment, so as to achieve a seal between the pipe member (1) and the coupling member (2).

3. The high-temperature and high-pressure self-balancing airtight threaded connection structure according to claim 2, characterized in that: The first threaded portion (101) and the third threaded portion (201) are both sawtooth threads. A first expansion gap (104) extending helically is formed between the sealing section (204) and the first threaded portion (101). The first expansion gap (104) comprises an expansion load section (105), an expansion abutment section (106), and a creep yielding section (107) which are interconnected and arranged in sequence. The first expansion gap (104) is used to yield to the expansion of the straight side of the first threaded portion (101). The expansion abutment section (106) is used to abut against the tooth top of the first threaded portion (101) that has expanded and deformed. The creep yielding section (107) is used to yield to the expansion of the oblique side of the first threaded portion (101). The width of the expansion load section (105) is smaller than the width of the creep yielding section (107).

4. The high-temperature and high-pressure self-balancing airtight threaded connection structure according to claim 3, characterized in that: The nested threaded portion (103) has a first sealing surface (108) and a second sealing surface (109), the tooth bottom angle between the first sealing surface (108) and the first threaded portion (101) is greater than the tooth bottom angle between the second sealing surface (109) and the first threaded portion (101), and the first sealing surface (108) is close to the inclined surface of the first threaded portion (101).

5. The high-temperature and high-pressure self-balancing airtight threaded connection structure according to claim 4, characterized in that: The top of the third threaded portion (201) has a first abutment portion (205) and a second abutment portion (206) respectively located on the upper and lower sides of the nested thread groove (202), the first abutment portion (205) is close to the first sealing surface (108), and the length of the first abutment portion (205) and the root of the third threaded portion (201) is greater than the length of the second abutment portion (206) and the root of the third threaded portion (201).

6. The high-temperature and high-pressure self-balancing airtight threaded connection structure according to claim 5, characterized in that: A thermal expansion sealing groove (207) is provided between the nested thread portion (103) and the nested thread groove (202), and the nested thread portion (103) can expand when heated to fill the thermal expansion sealing groove (207).

7. The high-temperature and high-pressure self-balancing airtight threaded connection structure according to claim 6, characterized in that: A first communicating groove (208) is formed between the first abutting portion (205) and the tooth bottom of the first threaded portion (101), and the two ends of the first communicating groove (208) are respectively connected to the thermal expansion sealing groove (207) and the creep yielding section (107). A second communicating groove (211) is formed between the second abutting portion (206) and the tooth bottom of the first threaded portion (101), and the two ends of the second communicating groove (211) are respectively connected to the thermal expansion sealing groove (207) and the expansion load section (105).

8. The high-temperature and high-pressure self-balancing airtight threaded connection structure according to claim 7, characterized in that: The width of the first communicating groove (208) is greater than the width of the second communicating groove (211), and the width of the thermal expansion sealing groove (207) is greater than the width of the first communicating groove (208).

9. The high-temperature and high-pressure self-balancing airtight threaded connection structure according to claim 8, characterized in that: The thermal expansion sealing groove (207) comprises a first sealing groove (209) and a second sealing groove (210) which are connected to each other, and the width of the first sealing groove (209) is greater than the width of the second sealing groove (210).

10. The high-temperature and high-pressure self-balancing airtight threaded connection structure according to claim 1, characterized in that: The second threaded portion (102) and the sealing threaded portion (301) are both rectangular threads and are transition fit. The second threaded portion (102) has an annular mounting groove (110). There are a plurality of annular mounting grooves (110) arranged along the axial direction of the second threaded portion (102). The high-temperature and high-pressure self-balancing airtight sealing threaded connection structure further includes: An annular seal (4), the annular seal (4) having a fourth threaded portion (401), the fourth threaded portion (401) smoothly connected to the second threaded portion (102), and the fourth threaded portion (401) transitionally matched to the sealing threaded portion (301).

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