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

Abstract

The application relates to the technical field of threads, and provides a high-temperature and high-pressure self-balancing airtight 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 part is arranged on the inner side of the pipe fitting, the tooth root of the first threaded part is provided with a nested threaded part in a convex manner, a coupling fitting is sleeved on the outer periphery of the adjacent ends of the two pipe fittings, a third threaded part is arranged at each end of the coupling fitting and is in threaded connection with the first threaded part of the pipe fitting, the tooth top of the third threaded part is provided with a nested threaded groove in threaded connection with the nested threaded part, a sealing piece is connected to the inner side of the adjacent ends of the two pipe fittings, the sealing piece is provided with two sealing threaded parts, and the two sealing threaded parts are in threaded connection with the second threaded parts of the two pipe fittings respectively. The technical problem that the threaded structure is damaged due to thread deformation caused by thermal creep of the pipeline structure under a high-temperature and high-pressure environment in the prior art is solved, and the failure rate of the pipeline structure under the high-temperature and high-pressure environment is reduced.

Description

Technical Field

[0001] This invention relates to the field of thread technology, specifically to a high-temperature, high-pressure self-balancing gas-tight threaded connection structure. Background Technology

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

[0003] Early pipe connections often used a single threaded fit (such as API standard round threads), relying solely on metal-to-metal contact for sealing, lacking specific leak-proof design. Under the pulse impact of high-temperature, high-pressure gas-liquid mixed flow (such as slug flow), the thread clearance is prone to widening due to pressure fluctuations, leading to media seepage and leakage along the gap. 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 wellhead explosions, environmental pollution, and other safety accidents. Simultaneously, acidic media corrode the thread teeth along the leakage path, further exacerbating seal failure, shortening maintenance cycles, and increasing extraction costs.

[0004] Traditional coupling and pipe fitting designs have flaws, making it difficult to balance the dual requirements of load-bearing and sealing. For example, some structures use interference fits to pursue sealing performance, causing the threads to "seize" during installation; while clearance fits, which prioritize ease of assembly, can cause plastic deformation or even fracture of the threads under high pressure due to concentrated radial loads. In thick-walled pipe connections, traditional structures cannot effectively distribute axial loads (such as the weight of the pipe string and formation compression loads), and local stress concentration on the thread teeth can reach more than 1.5 times the material's yield strength, easily leading to "disengagement" accidents. In deep well mining, the cost of handling such failures is high.

[0005] Thermal creep is another core problem faced by traditional connection structures. The long-term high-temperature environment of oil wells causes the thread material (such as 4130 steel) to undergo slow plastic deformation, resulting in a shorter thread profile and a longer pitch. Traditional structures, lacking compensation design, are prone to two extreme situations: First, if the sealing section has no reserved clearance, the threads will "jam" together after creep, making disassembly impossible during well workover; second, if the load-bearing section is too loose, the preload will loosen after creep, the thread meshing clearance will expand, and the sealing and load-bearing capacity will be lost.

[0006] Furthermore, traditional structures suffer from insufficient sealing redundancy and neglect the impact of fluid flow on the connection. When the primary seal (the mating of the coupling and the pipe's external thread) fails due to corrosion or creep, the lack of a secondary sealing barrier allows the medium to leak directly to the outside of the pipe. Simultaneously, in some connection structures, the seals and pipe fittings have inconsistent inner diameters, causing turbulence as the fluid flows through. This intensifies the scouring of the connection area by high-speed, sand-laden fluid, further shortening its service life. In asymmetrical connection designs, the additional stress caused by the difference in thermal expansion coefficients between the pipe fitting and the coupling can also lead to uneven thread loading, accelerating localized wear and breakage. Summary of the Invention

[0007] To overcome the above-mentioned defects, embodiments of the present invention provide a high-temperature and high-pressure self-balancing gas-tight threaded connection structure, which solves the technical problem in the prior art where thread deformation caused by thermal creep in pipeline structures under high-temperature and high-pressure environments leads to damage to the threaded structure.

[0008] According to one aspect, at least one embodiment of the present invention provides a high-temperature, high-pressure self-balancing gas-tight threaded connection structure, comprising:

[0009] The pipe fittings are in pairs, and each end of the pipe fittings has a first threaded portion and a second threaded portion. The first threaded portion is located on the outside of the pipe fittings, and the second threaded portion is located on the inside of the pipe fittings. The root of the first threaded portion has a protruding nested threaded portion.

[0010] A coupling is fitted around the outer periphery of adjacent ends of two pipe fittings. The coupling has two third threaded portions, which are located at both ends of the coupling and are threadedly connected to the first threaded portions of the two pipe fittings respectively. The top of the third threaded portion has a nested threaded groove that is threadedly connected to the nested threaded portion.

[0011] A sealing element is connected to the inner side of adjacent ends of the two pipe fittings. The sealing element has two sealing threads, which are respectively threaded to the second threads of the two pipe fittings.

[0012] 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 expand and deform under high temperature and high pressure to seal between the pipe and the coupling.

[0013] As a further technical solution, both the first threaded portion and the third threaded portion are sawtooth threads. A spirally extending first expansion gap 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 relief section that are interconnected and arranged sequentially. The first expansion gap is used to make way for the straight edge expansion of the first threaded portion. The expansion abutment section is used to abut against the tooth tip of the expanded and deformed first threaded portion. The creep relief section is used to make way for the oblique edge expansion of the first threaded portion. The width of the expansion load section is smaller than the width of the creep relief section.

[0014] 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 root of the first threaded portion is greater than the angle between the second sealing surface and the root of the first threaded portion, and the first sealing surface is close to the inclined surface of the first threaded portion.

[0015] As a further technical solution, the top of the third thread has a first abutting portion and a second abutting portion located on the upper and lower sides of the nested thread groove, respectively. The first abutting portion is close to the first sealing surface, and the length of the first abutting portion and the root of the third thread is greater than the length of the second abutting portion and the root of the third thread.

[0016] As a further technical solution, a thermal expansion sealing groove is provided between the nested threaded portion and the nested threaded groove, and the nested threaded portion can expand after being heated to fill the thermal expansion sealing groove.

[0017] As a further technical solution, a first connecting groove is formed between the first abutting part and the root of the first threaded part, and the two ends of the first connecting groove are respectively connected to the thermal expansion sealing groove and the creep relief section. A second connecting groove is provided between the second abutting part and the root of the first threaded part, and the two ends of the second connecting groove are respectively connected to the thermal expansion sealing groove and the expansion load section.

[0018] As a further technical solution, the width of the first connecting groove is greater than the width of the second connecting groove, and the width of the thermal expansion sealing groove is greater than the width of the first connecting groove.

[0019] As a further technical solution, the thermal expansion sealing groove has a first sealing groove and a second sealing groove that are interconnected, wherein the width of the first sealing groove is greater than the width of the second sealing groove.

[0020] As a further technical solution, both the second threaded portion and the sealing threaded portion are rectangular threads and are transition fits. The second threaded portion has an annular mounting groove, and there are several annular mounting grooves arranged along the axial direction of the second threaded portion. The high-temperature and high-pressure self-balancing gas-tight threaded connection structure further includes:

[0021] An annular seal having a fourth threaded portion that smoothly engages with a second threaded portion and transitionally engages with a sealing threaded portion.

[0022] The beneficial effects of this invention are as follows:

[0023] In this invention, long-term high temperatures in oil wells can cause creep in the thread material. Before thermal creep: the load-bearing section transitions into the first threaded section, bearing the weight of the tubing string, the formation compression load, and the axial force of the high-pressure fluid. At the same time, the tight meshing achieves initial sealing, avoiding leakage caused by gaps in the early stages of installation. During thermal creep, as the high-temperature service time increases, the thread material undergoes slow plastic deformation. At this time, the sealing section, due to the reserved gap, can accommodate the deformation caused by creep, preventing the thread from "seizing up" or breaking. Simultaneously, thermal expansion reduces the gap in the sealing section, increases the contact pressure on the thread tooth surface, strengthens the sealing effect, and reduces pressure leakage caused by creep relaxation.

[0024] The sealing thread of the seal mates with the second thread of the pipe fitting. Through thermal expansion, the stress distribution is further optimized, reducing thread creep. At high temperatures, the sealing thread expands with increasing temperature, reducing the thread engagement clearance with the second thread and creating a tighter interference fit. This expansion generates radial pressure that is evenly distributed across the entire thread engagement surface. Simultaneously, under the influence of high-pressure fluid, the inner wall of the pipe experiences significant radial force, which can easily cause the pipe fitting to expand outwards elastically, thus "stretching" the pitch of the second thread. The expansion of the sealing thread offsets some of this expansion, maintaining thread engagement stability and reducing misalignment caused by pitch deviations. This reduces the additional shear force on the thread teeth and slows down the creep process.

[0025] The overall symmetrical structure can alleviate the additional stress caused by the difference in thermal expansion coefficients of different components, reduce uneven creep caused by local overheating, and thus reduce the occurrence of preload relaxation and thread eccentricity. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are merely some exemplary embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the exemplary embodiments of the present invention and these drawings without any creative effort.

[0027] Figure 1 This is a schematic diagram of a structure according to an embodiment of the present invention;

[0028] Figure 2 for Figure 1 A schematic diagram of the upper part of the embodiment;

[0029] Figure 3 for Figure 2 A magnified structural diagram of A in the middle;

[0030] Figure 4 for Figure 3 A magnified structural diagram of B in the diagram.

[0031] In the diagram: Pipe fitting-1, First threaded section-101, Second threaded section-102, Nested threaded section-103, First expansion gap-104, Expansion load section-105, Expansion abutment section-106, Creep clearance section-107, First sealing surface-108, Second sealing surface-109, Annular mounting groove-110, Coupling-2, Third threaded section-201, Nested threaded groove-202, Load-bearing 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 section-301, Annular seal-4, Fourth threaded section-401. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it.

[0033] To keep the drawings concise, each drawing only schematically shows the parts relevant to the invention; these do not represent the actual structure of the product. Furthermore, for ease of understanding, in some drawings, only one of components with the same structure or function is schematically shown, or only one is labeled. In this document, "one" not only means "only one," but can also mean "more than one," and "several" includes "two" and "more than two."

[0034] In this document, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0035] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0036] In the description of this embodiment, terms such as "upper," "lower," "left," and "right" are based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of description and simplification of operation, and are not intended to 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 the present invention.

[0037] Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0038] like Figures 1-4 As shown, it illustrates a high-temperature and high-pressure self-balancing gas-tight threaded connection structure in one embodiment of the present invention.

[0039] In some examples, pipe fitting 1 is a fundamental component of the connection structure, with several pipe fittings 1 arranged sequentially along the axial direction. Two first threaded portions 101, symmetrically arranged on the outer sides of both ends of the fitting, connect with the third threaded portions 201 at both ends of the coupling 2. The nested threaded portions 103 at the root of the first threaded portions 101 can engage with the nested threaded grooves 202 at the top of the third threaded portions 201 of the coupling 2. This nested structure further enhances the tightness of the connection under high temperature and pressure, effectively preventing loosening or leakage of the threaded connection due to changes in ambient temperature. Simultaneously, two second threaded portions 102, symmetrically arranged on the inner sides of both ends of the pipe fitting 1, connect with the sealing threaded portions 301 of the sealing element 3. This connection further improves the sealing effect of the entire structure, ensuring that the high-temperature, high-pressure medium in the oil well does not leak from the connection point.

[0040] The two third threaded portions 201 of the coupling 2 serve as internal threads, respectively connecting to the first threaded portions 101 of two adjacent pipe fittings 1, thus 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 effectively withstands axial and radial loads within the oil well, ensuring the stability and load-bearing capacity of the connection structure under high pressure. The sealing section 204 has a clearance fit with the first threaded portion 101. Under high temperature and high pressure, due to the thermal expansion and contraction characteristics of the material, the clearance gradually decreases or even disappears, thus forming a good sealing effect and preventing leakage of high-temperature and high-pressure oil and gas media.

[0041] The two sealing threaded portions 301 of the seal 3 are respectively threadedly connected to the second threaded portions 102 of the two adjacent pipe fittings 1, further enhancing the sealing performance of the overall structure. In addition, the inner diameter of the seal 3 is equal to the inner diameter of the pipe fitting 1. This design can ensure the smooth flow of oil in the pipeline, avoid turbulence or pressure loss caused by inconsistent inner diameters, and also reduce the scouring and corrosion of the connection parts by the medium.

[0042] In high-temperature and high-pressure oil wells, formation fluids (including acidic gases and high-temperature steam) easily permeate along the thread gaps. The nested threaded part 103 (the root of the first threaded part 101 of pipe fitting 1) and the nested threaded groove 202 (the crest of the third threaded part 201 of coupling 2) form multiple sealing interfaces through "tooth meshing". The tight nesting of the two extends the leakage path, requiring the high-temperature and high-pressure fluid to break through multiple thread meshing barriers, significantly increasing the leakage resistance. Especially for the pulse impact of gas-liquid mixed flow (such as slug flow), it can reduce the instantaneous leakage. When the temperature fluctuates (such as the alternation of 200-300℃ in steam injection) and causes the thread to expand and contract, the nested structure compensates for the gap through the tooth surface fit, avoiding the leakage channel caused by the loose fit of ordinary threads. It is suitable for the working conditions of frequent temperature changes in oil wells. At the same time, it increases the thread meshing contact area under high-temperature and high-pressure environment, improves the pull-out force and torque resistance of the connection, and can effectively disperse the axial force and radial force under high pressure, reducing the local stress concentration of the thread teeth.

[0043] To address minor leaks caused by thermal creep and corrosion in the main seal (connection of coupling 2 and pipe fitting 1) of the oil well, the seal 3 forms "internal redundant protection": the sealing thread 301 of the seal 3 is connected to the second thread 102 of the pipe fitting 1, forming an independent sealing cavity inside the pipe fitting. When the sealing section 204 of the coupling 2 leaks due to hydrogen sulfide corrosion or thermal deformation, it can block the fluid from spreading to the outside of the pipe, avoiding wellhead leakage or further corrosion of the tubing by acidic media. The inner diameter of the seal 3 is the same as that of the pipe fitting 1, so it does not interfere with the flow of high-pressure fluids (such as sand-laden crude oil), and at the same time maintains structural stability under high pressure differential, preventing deformation caused by fluid impact, and is suitable for the harsh environment of high flow velocity and high sand content in oil wells.

[0044] Long-term high temperatures in oil wells (such as 250°C in steam injection wells) can cause creep in the thread material (e.g., the thread profile of 4130 steel becomes "shorter"). Before thermal creep: the third thread section 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 transitions to the first thread section 101. The load-bearing section 203 and the first thread section 101 transition to bear the weight of the tubing string, the formation extrusion load, and the axial force of the high-pressure fluid. At the same time, it achieves initial sealing through tight meshing, avoiding leakage caused by gaps in the early stages of installation. During thermal creep, as the high-temperature service time increases, the thread material undergoes slow plastic deformation. At this time, the sealing section 204 (with a clearance fit to the first thread section 101) can accommodate the deformation caused by creep due to the reserved gap, preventing the thread from "seizing" or breaking. At the same time, thermal expansion reduces the gap of the sealing section 204, increases the contact pressure of the thread surface, strengthens the sealing effect, and reduces pressure leakage caused by creep relaxation.

[0045] The sealing thread 301 of the seal 3 mates with the second thread 102 of the pipe fitting 1. Under high temperature conditions, the seal 3 expands thermally, causing the stress of the pipe fitting 1 to be distributed and borne by the seal 3, thereby optimizing the stress distribution and reducing the creep effect of the thread. Under high temperature conditions, the sealing thread 301 will expand thermally with the temperature rise, reducing the thread engagement clearance with the second thread 102 and forming a tighter interference fit. The radial pressure generated by this expansion will be evenly distributed across the entire thread engagement surface. At the same time, under the action of high pressure fluid, the inner wall of the pipe is subjected to huge radial force, which can easily cause the pipe fitting 1 to undergo outward elastic expansion. Under the thermal creep effect, the pitch of the second thread 102 is "stretched" when the temperature drops. The expansion of the sealing thread 301 under stress can offset part of the axial expansion, maintain the stability of the thread engagement, reduce the "misalignment" phenomenon caused by pitch deviation, thereby reducing the additional shear force on the thread teeth and delaying the creep process.

[0046] The overall symmetrical structure (symmetrical threads at both ends of pipe fitting 1 and symmetrical connection of coupling 2) can alleviate the additional stress caused by the difference in thermal expansion coefficients of different components (such as pipe fitting and coupling), reduce uneven creep caused by local overheating, and thus reduce the occurrence of preload relaxation and thread eccentricity.

[0047] Furthermore, in the high-temperature and high-pressure environment of oil wells, both the first threaded part 101 and the third threaded part 201 adopt sawtooth threads. This type of thread has an asymmetrical tooth profile, with a steeper straight edge on one side and a gentler bevel on the other side. When subjected to axial loads, it can more effectively disperse the force and enhance the connection's resistance to loosening. It is very suitable for the environment of oil wells, which need to withstand high pressure and vibration for a long time.

[0048] During the manufacturing process, a portion of the material from either the third threaded section 201 or the first threaded section 101 is cut to create a spiral-shaped first expansion gap 104 between the third threaded section 201 and the first threaded section 101. This gap is designed to accommodate the thermal expansion of the material under high temperature and high pressure conditions. The first expansion gap 104 consists of interconnected and sequentially arranged expansion load sections 105, expansion abutment sections 106, and creep clearance sections 107. Each section has a clear function, working together to ensure the sealing performance and structural integrity of the threaded connection under extreme environments.

[0049] When the temperature inside the oil well rises, the first threaded portion 101 of the fitting 1 will deform due to thermal expansion. The expansion load section 105 has a relatively shallow depth and is mainly used to accommodate the initial expansion of the straight edge of the first threaded portion 101. In the initial stage of temperature rise, the expansion of the straight edge is relatively small, and the space provided by the expansion load section 105 can alleviate the pressure caused by the expansion. Simultaneously, it uses the contact force between the threads to bear part of the load, preventing thread damage due to excessive local stress.

[0050] As the temperature continues to rise, the expansion gradually increases, and the tip of the first thread 101 undergoes significant expansion deformation. At this point, the expansion contact section 106 begins to function. By contacting the tip of the thread, it limits excessive expansion and simultaneously uses the pressure generated by the contact to enhance the sealing effect between the threads, preventing high-temperature and high-pressure media from leaking from the gap.

[0051] The creep clearance section 107 has a relatively large depth, mainly used to accommodate the expansion of the bevel of the first threaded portion 101. Under long-term high-temperature conditions, the material will undergo creep. The creep expansion of the bevel requires more space to release stress. The sufficient space provided by the creep clearance section 107 can effectively avoid plastic deformation or cracks caused by the limited expansion of the bevel, ensuring the long-term stability of the threaded connection.

[0052] Meanwhile, the bevel of the first threaded portion 101 has a relatively high material content, giving it significant deformation potential during temperature changes. However, due to the ample clearance space provided by the creep clearance section 107, the deformation of the bevel is fully released within this area, with minimal or no contact with other structures. This design effectively prevents the deformation of the bevel from being transmitted to the sealing section 204, thus ensuring minimal deformation of the sealing section 204 during temperature changes. As a key component for achieving high-temperature and high-pressure sealing after creep deformation, the smaller deformation of the sealing section 204 allows it to maintain a relatively stable fit, which is beneficial for maintaining the initial sealing effect.

[0053] When the material undergoes creep deformation due to prolonged exposure to high temperatures, the bevel of the first threaded portion 101 will experience a certain degree of creep expansion. At this time, the creep relief section 107 will gradually thin under tension. This thinning is not structural damage; instead, it further reduces the gap between the creep relief section 107 and the bevel, resulting in a tighter fit. Simultaneously, because the bevel has less contact with other structures, the stress generated by creep mainly acts on the wall of the creep relief section 107, promoting a tighter fit between this area and the bevel, thereby improving the overall sealing performance of the threaded connection and effectively preventing leakage of high-temperature, high-pressure oil and gas media.

[0054] This design utilizes the properties of materials and the interaction between structures. Under temperature changes and long-term creep, it can protect the stability of the sealing section 204 through the yielding function of the creep yielding section 107, and enhance the sealing performance by means of the structural changes brought about by creep. This gives the entire connection structure better long-term working performance in the high temperature and high pressure environment of oil wells.

[0055] This three-section expansion gap, combined with the structural characteristics of the sawtooth thread, allows the first thread section 101 and the third thread section 201 to freely release expansion stress under high temperature and high pressure, and to achieve dynamic sealing and load balance through the synergistic effect of each section, further improving the reliability of the entire connection structure in the extreme environment of oil wells.

[0056] Furthermore, the nested threaded portion 103 serves as a sealing unit that mates with the first threaded portion 101 and the nested threaded groove 202 of the coupling member 2. The angle design and positional 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 anti-leakage capability of the threaded connection.

[0057] Structurally, the angle between the first sealing surface 108 and the root of the first thread 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 thread 101 (i.e., the hypotenuse of the sawtooth thread). This angular difference and positional arrangement are due to its proximity to the inclined surface and the larger angle. Under thread tightening and high-temperature, high-pressure conditions, 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 allows it to generate greater sealing contact pressure and a wider contact area when subjected to axial loads and radial expansion forces, quickly blocking the penetration path of high-pressure oil and gas. Simultaneously, its position near the inclined surface directly receives the radial thrust generated by the thermal expansion of the first thread 101, converting the expansion force into sealing pressure and enhancing the main sealing effect.

[0058] The smaller included angle of the second sealing surface 109 forms another sealing edge. After the first sealing surface 108 achieves initial sealing, the second sealing surface 109 will form a secondary fit with the inner wall of the nested threaded groove 202. The advantage of this design is that when high temperature causes material creep or vibration causes small displacement, the second sealing surface 109 can fill any small gaps that may occur through its own angular characteristics, forming a compensating seal. In addition, the small included angle design results in higher contact stress under the same amount of expansion, which can form a secondary barrier for trace amounts of media that are not completely blocked by the first sealing surface 108.

[0059] In the high-temperature and high-pressure environment of oil wells, when the temperature rises and causes the first threaded portion 101 to expand, the first sealing surface 108, due to its large included angle and advantageous position, firstly enhances the seal through expansion force. If long-term creep occurs, the second sealing surface 109, with its stress concentration characteristics at a small included angle, continuously maintains the sealing compensation for the gap. This design enables the nested threaded portion 103 to withstand instantaneous high-pressure impacts in extreme environments and adapt to long-term changes in material properties, providing a stable and reliable sealing guarantee for the entire threaded connection structure.

[0060] Furthermore, the first abutment portion 205 and the second abutment portion 206 provided at the top of the third thread portion 201 cooperate with the first sealing surface 108 and the second sealing surface 109 of the nested thread portion 103, further improving the sealing performance and structural stability of the threaded connection in the high temperature and high pressure oil well environment.

[0061] The first abutment portion 205 is 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 will contact the first sealing surface 108. The length of the root of the first abutment portion 205 and the third threaded portion 201 is greater than the length of the root of the second abutment portion 206 and the third threaded portion 201. This length difference is designed according to the function and stress conditions of the two.

[0062] 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 thread root, the pressure on the first sealing surface 108 is relatively large under high temperature and high pressure conditions. The relatively long design of the first abutting portion 205 provides more stable and sufficient support for the first sealing surface 108, ensuring that the first sealing surface 108 and the first abutting 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, dispersing the contact pressure, avoiding damage to the sealing surface caused by excessive local pressure, and extending the service life of the sealing structure.

[0063] The second abutment portion 206 corresponds to the second sealing surface 109, and its length relative to the root of the third thread portion 201 is relatively short. This is because the angle between the second sealing surface 109 and the thread root is small, and it mainly performs the function of secondary sealing, thus bearing relatively less pressure. The shorter length design allows the second abutment portion 206 to form a tighter fit when in contact with the second sealing surface 109, better performing the sealing function and effectively intercepting the medium that the first sealing surface 108 has not completely blocked.

[0064] The cooperation between the first abutting part 205 and the second abutting part 206 and the first sealing surface 108 and the second sealing surface 109 can adapt to the thermal expansion and contraction and creep phenomenon of the material. Through the stable support of the first abutting part 205 and the tight fit of the second abutting part 206, the sealing performance of the entire threaded connection is always kept in good condition, providing a guarantee for the safe mining of oil wells.

[0065] Furthermore, a thermal expansion sealing groove 207 is provided between the nested threaded portion 103 and the nested threaded groove 202. This structural design further enhances the sealing effect under high-temperature environments. At room temperature, the thermal expansion sealing groove 207 provides sufficient space for the nested threaded portion 103, without affecting the normal connection and fit of the components. However, in the high-temperature environment of an oil well, the nested threaded portion 103 expands due to the increased temperature, and its expanded volume fills the thermal expansion sealing groove 207. This filling effect completely eliminates the gap between the nested threaded portion 103 and the nested threaded groove 202, forming an additional sealing barrier that effectively prevents high-temperature, high-pressure oil and gas media from leaking through the tiny gaps between them. At the same time, the filling of the thermal expansion sealing groove 207 also enhances the overall connection strength between the nested threaded portion 103 and the nested threaded groove 202, making their fit more robust under high temperature and pressure, further improving the stability and reliability of the entire threaded connection structure.

[0066] Furthermore, the first connecting groove 208 formed between the first abutting portion 205 and the root of the first threaded portion 101, and the second connecting groove 211 between the second abutting portion 206 and the root of the first threaded portion 101, play a connecting and synergistic role in the sealing and stress adjustment of the entire structure.

[0067] The two ends of the first connecting groove 208 are connected to the thermal expansion sealing groove 207 and the creep relief section 107, respectively. In a high-temperature environment, when the nested threaded portion 103 expands to fill the thermal expansion sealing groove 207, a certain pressure is generated. The first connecting groove 208 can provide a channel for this pressure, allowing it to flow to the creep relief section 107. The creep relief section 107 itself provides space for the expansion and creep of the inclined side of the first threaded portion 101. It has a certain stress dispersion and absorption capacity, and can accept the pressure from the first connecting groove 208, preventing excessive pressure in the thermal expansion sealing groove 207 from affecting the sealing effect. It also reduces the erosion of the sealing surface by the medium.

[0068] The two ends of the second connecting groove 211 are connected to the thermal expansion sealing groove 207 and the expansion load section 105, respectively. When the thermal expansion sealing groove 207 is filled, the second connecting groove 211 can transfer part of the pressure in the thermal expansion sealing groove 207 to the expansion load section 105. The expansion load section 105 has a transition fit with the first threaded part 101, has a certain load-bearing capacity, can withstand this part of the pressure, and distribute it throughout the entire connection structure to avoid local pressure concentration. At the same time, this pressure transmission can also make the fit between the expansion load section 105 and the first threaded part 101 tighter, indirectly improving the sealing performance.

[0069] The design of these two connecting grooves makes the thermal expansion sealing groove 207, the creep relief section 107 and the expansion load section 105 form an interconnected whole, realizing the rational distribution of pressure and the effective drainage of the medium, further enhancing the adaptability and reliability of the threaded connection structure in the high temperature and high pressure oil well environment.

[0070] Furthermore, the width of the thermal expansion sealing groove 207 is greater than the width of the first connecting groove 208, and the width of the second connecting groove 211 is less than the width 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 greater depth ensures its capacity, guaranteeing that the nested threaded portion 103 can fully fill the groove after expansion to form an effective seal. The width of the first connecting groove 208 is smaller than that of the thermal expansion sealing groove 207, which can create a certain pressure gradient during the drainage process, prompting pressure and medium to flow towards the creep relief section 107. The smaller width of the second connecting groove 211 allows for better control of the intensity of pressure transmission, preventing excessive pressure from suddenly acting on the expansion load section 105 and ensuring the stable stress of the structure.

[0071] Furthermore, the thermal expansion sealing groove 207 has a first sealing groove 209 and a second sealing groove 210 that are interconnected, and the width of the first sealing groove 209 is greater than the width of the second sealing groove 210. This width difference design is adapted to the expansion characteristics of the nested threaded portion 103. Under high-temperature conditions, different areas of the nested threaded portion 103 have different expansion amounts. The thicker width of the first sealing groove 209 can provide sufficient space for areas with larger expansion amounts, ensuring that this part can fully fill the groove to form a tight seal. The narrower width of the second sealing groove 210 can cooperate with areas with relatively smaller expansion amounts, forming a tighter fit after filling, further enhancing the overall sealing effect. At the same time, the interconnection between the two allows the expansion force of the nested threaded portion 103 to be more evenly distributed within the thermal expansion sealing groove 207, avoiding excessive local pressure that could lead to seal failure, and improving the sealing reliability of the thermal expansion sealing groove 207 under high-temperature and high-pressure environments.

[0072] Furthermore, both the second threaded portion 102 and the sealing threaded portion 301 adopt a rectangular thread design with a transition fit. Rectangular threads are characterized by their rectangular tooth profile, high strength, and high transmission efficiency. In the high-temperature and high-pressure environment of oil wells, this thread type can better withstand axial forces, ensuring the stability of the connection between the second threaded portion 102 and the sealing threaded portion 301. The transition fit provides a certain amount of interference between the two, ensuring a tight connection without causing installation difficulties or thread damage due to excessive interference. This helps maintain good sealing performance under high temperature and pressure. In steam injection or high-pressure gas lift scenarios, its high strength characteristics reduce plastic deformation of the thread teeth caused by stress concentration, avoiding pitch deviation caused by creep and ensuring long-term connection stability. Simultaneously, the high transmission efficiency of rectangular threads reduces frictional resistance during installation, adapting to the frequent disassembly and assembly needs of oil well sites and reducing the risk of thread seizure during assembly. In high-temperature environments, the deformation caused by thermal expansion of both parts can be compensated by the interference fit, avoiding sealing failure due to expansion of the clearance fit, and at the same time, the threads will not "crack" due to excessive interference fit, making it suitable for the working conditions of frequent temperature fluctuations in oil wells.

[0073] The second threaded portion 102 is also provided with an annular mounting groove 110. The high-temperature and high-pressure self-balancing gas-sealing threaded connection structure is equipped with an annular seal 4, which is a rubber component. The annular seal 4 has a fourth threaded portion 401, which smoothly connects to the second threaded portion 102 and transitions into 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 shift during operation. The smooth connection between the fourth threaded portion 401 and the second threaded portion 102 avoids stress concentration at the threaded connection. At the same time, the transitional fit with the sealing threaded portion 301 further enhances the sealing effect in this area. The cooperation with the second threaded portion 102 and the sealing threaded portion 301 forms a double sealing guarantee, effectively preventing leakage of high-temperature and high-pressure oil and gas media and improving the sealing reliability of the entire connection structure.

[0074] The transition fit between the fourth threaded portion 401 and the sealing threaded portion 301 forms a "secondary meshing seal" in addition to the basic seal between the second threaded portion 102 and the sealing threaded portion 301. When the main seal develops a slight gap due to thermal creep, the fourth threaded portion 401 can block media penetration through tight meshing. Combined with the large-area contact of the rectangular thread, it forms a "double barrier," significantly reducing the leakage rate.

[0075] At high temperatures, the second threaded section 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 section 102, can alleviate stress concentration in the following ways: the mounting groove divides the continuous thread structure of the second threaded section 102 into "two segments," allowing the axial stress generated by thermal creep to form a "stress release node" at the groove, preventing stress accumulation along the entire thread length and thus avoiding overall deformation. The spatial structure of the groove provides a small deformation buffer space for the threaded section. When the thread expands due to high temperature or attempts to expand outward due to creep, the mounting groove can accommodate part of the deformation increment, reducing excessive compression between the thread crest and the sealing threaded section 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.

[0076] The tight fit between the annular mounting groove 110 and the annular seal 4 forms a "stress transmission path": when the second threaded portion 102 generates radial or axial stress due to thermal creep, the inner wall of the mounting groove will transfer part of the stress to the annular seal 4 embedded therein. Since the annular seal 4 transitions to the sealing threaded portion 301 through the fourth threaded portion 401, its flexible structure can act as a "stress bearer," releasing the load of the second threaded portion 102. The stress transmitted to the annular seal 4 will be converted into contact pressure between it and the mounting groove and the sealing threaded portion 301. This pressure can further increase with thermal expansion at high temperatures, which in turn enhances the tightness of the meshing between the annular seal 4 and the thread, improving sealing redundancy while dispersing stress.

[0077] The rectangular thread of the second threaded part 102 and the sealing threaded part 301, with a transition fit, solves the problems of axial force bearing and basic sealing under high temperature and high pressure. The annular seal 4, positioned by the annular mounting groove 110 and with the double engagement of the fourth threaded part 401, further enhances the sealing redundancy and structural stability. The three components work together to form an integrated design of "strong load bearing, double sealing, and resistance to thermal deformation", which is suitable for the extreme environment of high temperature, high pressure, strong corrosion, and high vibration in oil wells, effectively extending the service life of the threaded connection and reducing safety risks such as wellhead leakage and tubing failure.

[0078] Furthermore, multiple axially arranged annular mounting grooves 110 divide the continuous thread structure of the second threaded section 102 into multiple independent load-bearing units. During high-temperature creep, the creep stress of each thread segment is "interrupted" by adjacent mounting grooves, preventing stress from continuously accumulating along the axial direction. For example, three mounting grooves can divide the threaded section into two independent regions, with the creep deformation of each segment being only 1 / 2 of the overall structure, significantly reducing the risk of thread teeth "crushing" or pitch deviation due to excessive deformation.

[0079] Meanwhile, each mounting groove transmits part of the stress through an annular seal 4, distributing the load to multiple annular seals 4, preventing a single annular seal 4 from failing due to stress overload, and adapting to the continuous load conditions under long-term high temperature and high pressure in oil wells.

[0080] Several annular mounting grooves 110 are used to install multiple annular seals 4, forming a series array along the second threaded portion 102. When high-pressure oil and gas media permeate, the interface between the fourth threaded portion 401 and the sealing threaded portion 301 of the multi-stage annular seals 4 needs to be broken through in sequence, and the leakage path is greatly extended.

[0081] Even if a small gap appears in a certain stage seal due to local corrosion or creep, the subsequent annular seal 4 can still block the diffusion of the medium. Compared with a single-stage seal, its leakage rate can be reduced, making it particularly suitable for dynamic sealing scenarios under gas-liquid mixed-phase flow impact.

[0082] Multiple axially arranged mounting slots provide multi-point rigid support for the second threaded section 102. In the vibrating environment of oil well operations, multi-point constraint can reduce radial oscillation of the threaded section and prevent the thread engagement clearance from widening due to vibration.

[0083] Meanwhile, the multi-groove design reduces the impact of installation deviation of a single annular seal 4. Even if a certain annular seal 4 is slightly misaligned 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.

[0084] Deep oil wells exhibit axial temperature gradients, resulting in varying thermal expansion rates for threaded sections of different widths. Multiple axially arranged mounting grooves can adapt to changes in sealing requirements caused by temperature gradients through differentiated deformation of the corresponding annular seal 4, preventing issues like "overtightening failure" or "loosening leakage" in areas with large temperature differences caused by a single seal. This further enhances the structural stability and sealing reliability of the second threaded section 102 in high-temperature, high-pressure oil well environments, providing more comprehensive protection for threaded connections under extreme conditions.

[0085] 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 it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-temperature, high-pressure self-balancing gas-tight threaded connection structure, characterized in that, include: Pipe fitting (1), there are two pipe fittings (1), each of the pipe fittings (1) has a first threaded part (101) and a second threaded part (102) at its end. The first threaded part (101) is located on the outside of the pipe fitting (1), and the second threaded part (102) is located on the inside of the pipe fitting (1). The root of the first threaded part (101) has a protruding nested threaded part (103). A coupling (2) is fitted around the outer periphery of the adjacent ends of the two pipe fittings (1). The coupling (2) has two third threaded portions (201). The third threaded portions (201) are located at both ends of the coupling (2) and are threadedly connected to the first threaded portions (101) of the two pipe fittings (1). The top of the third threaded portion (201) has a nested threaded groove (202) that is threadedly connected to the nested threaded portion (103). A sealing element (3) is connected to the inner side of the adjacent ends of the two pipe fittings (1). The sealing element (3) has two sealing threaded portions (301), which are respectively threaded to the second threaded portions (102) of the two pipe fittings (1).

2. The high-temperature and high-pressure self-balancing gas-tight threaded connection structure according to claim 1, characterized in that, The third threaded part (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 part (101). The sealing section (204) is clearance-fitted with the first threaded part (101). The sealing section (204) can expand and deform under high temperature and high pressure to seal between the pipe fitting (1) and the coupling (2).

3. The high-temperature and high-pressure self-balancing gas-tight threaded connection structure according to claim 2, characterized in that, Both the first threaded portion (101) and the third threaded portion (201) are sawtooth threads. A spirally extending first expansion gap (104) is formed between the sealing section (204) and the first threaded portion (101). The first expansion gap (104) has an expansion load section (105), an expansion abutment section (106), and a creep yielding section (107) that are interconnected and arranged in sequence. The first expansion gap (104) is used to yield to the straight edge expansion of the first threaded portion (101). The expansion abutment section (106) is used to abut against the tooth tip of the expanded and deformed first threaded portion (101). The creep yielding section (107) is used to yield to the oblique edge expansion 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 gas-tight 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 angle between the first sealing surface (108) and the first threaded portion (101) is greater than the angle between the second sealing surface (109) and the first threaded portion (101). 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 gas-tight threaded connection structure according to claim 4, characterized in that, The top of the third threaded portion (201) has a first abutting portion (205) and a second abutting portion (206) located on the upper and lower sides of the nested threaded groove (202), respectively. The first abutting portion (205) is close to the first sealing surface (108). The length of the root of the first abutting portion (205) and the third threaded portion (201) is greater than the length of the root of the second abutting portion (206) and the third threaded portion (201).

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

7. The high-temperature and high-pressure self-balancing gas-tight threaded connection structure according to claim 6, characterized in that, A first connecting groove (208) is formed between the first abutting part (205) and the root of the first threaded part (101). The two ends of the first connecting groove (208) are respectively connected to the thermal expansion sealing groove (207) and the creep relief section (107). A second connecting groove (211) is formed between the second abutting part (206) and the root of the first threaded part (101). The two ends of the second connecting 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 gas-tight threaded connection structure according to claim 7, characterized in that, The width of the first connecting groove (208) is greater than the width of the second connecting groove (211), and the width of the thermal expansion sealing groove (207) is greater than the width of the first connecting groove (208).

9. The high-temperature and high-pressure self-balancing gas-tight threaded connection structure according to claim 8, characterized in that, The thermal expansion sealing groove (207) has a first sealing groove (209) and a second sealing groove (210) that are interconnected, wherein 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 gas-tight threaded connection structure according to claim 1, characterized in that, Both the second threaded portion (102) and the sealing threaded portion (301) are rectangular threads and are transition fits. The second threaded portion (102) has an annular mounting groove (110), and there are several annular mounting grooves (110) arranged along the axial direction of the second threaded portion (102). The high-temperature and high-pressure self-balancing gas-tight threaded connection structure further includes: The annular seal (4) has a fourth threaded portion (401) that smoothly engages with the second threaded portion (102) and transitionally engages with the sealing threaded portion (301).

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