A gas seal structure of a casing

Abstract

The present application relates to the technical field of casing joint structure, and discloses a casing and tubing airtight seal buckle structure, which comprises two casing and tubing bodies and a joint pipe, the outer side of the connecting end of the two casing and tubing bodies is provided with external threads, and the inner side of the two ends of the joint pipe is provided with internal threads matched with the external threads, and when the opposite end faces of the two casing and tubing bodies abut against each other, the casing and tubing airtight seal buckle structure further comprises a port clamping piece which is detachably arranged at the two ends of the joint pipe.The casing and tubing airtight seal buckle structure generates fastening force when the port clamping piece is installed at the two ends of the joint pipe, further fastens the end part of the casing and tubing body, and limits the axial relative sliding between the casing and tubing body and the joint pipe.During the installation of the port clamping piece, the driving load sharing piece moves along the casing and tubing body in the radial direction and abuts against the outer peripheral wall thereof, an auxiliary support structure is formed between the outer peripheral wall of the casing and tubing body and the inner wall of the joint pipe, and the stress concentration of the threads on the casing and tubing body and the joint pipe is reduced.

Description

Technical Field

[0001] This invention relates to the field of casing joint structure technology, specifically to an oil casing gas-tight joint structure. Background Technology

[0002] Gas sealing of casing is a core technology for ensuring wellbore integrity in oil and gas well engineering. Its core objective is to achieve gas sealing of the tubing string under complex conditions such as high pressure, high temperature, and corrosion by using a specially designed gas-sealing thread structure in the casing joint, through precision structure and material optimization, and by strictly following the threading process. This solves the problem of insufficient sealing performance of traditional API threads.

[0003] Currently, existing gas-tight coupling structures for oil casing and tubing improve the sealing performance between the oil casing and tubing and the fittings by modifying the thread profile. However, in actual use, the casing is also subjected to various dynamic loads during oil extraction. Under long-term working conditions, vibration or alternating loads cause axial relative sliding of the thread contact surface, leading to stripping of the thread. This results in damage to the surface oxide layer, direct friction between metals, the formation of wear debris, and accelerated wear, causing gaps in the threaded sealing area and resulting in leakage. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, this invention provides an oil casing gas-tight threaded joint structure, which effectively solves the problem in existing technologies where, under prolonged working conditions, vibration or alternating loads cause axial relative sliding of the threaded contact surface, leading to stripping, damage to the surface oxide layer, direct metal-to-metal friction, the formation of wear debris, and accelerated wear, resulting in gaps and leakage at the threaded sealing area. Technical solution

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a gas-tight coupling structure for oil casing, comprising two oil casing bodies and a connector fitting. External threads are provided on the outer sides of the connecting ends of the two oil casing bodies, and internal threads adapted to the external threads are provided on the inner sides of both ends of the connector fitting. When the opposite end faces of the two oil casing bodies abut against each other, the connector fitting is used to be sleeved on the two oil casing bodies. The invention also includes: The port clamps are detachably installed at both ends of the connector fitting, and are used to further secure the ends of the oil casing body; The load-sharing component is located inside the port clamp and is used to reduce stress concentration on the threads of the oil casing and fittings. During the process of installing the port clamp as a whole into the connector fitting, the drive load-sharing component moves along the radial direction of the oil casing body and presses against the outer peripheral wall of the oil casing body to form an auxiliary support structure between the outer peripheral wall of the oil casing body and the inner wall of the connector fitting.

[0006] Furthermore, the port clamp includes a shrink sleeve disposed at the end of the connector fitting. The diameter of the shrink sleeve gradually decreases from the side near the connector fitting to the far end, and the minimum inner diameter of the shrink sleeve is equal to the diameter of the oil casing body. The outer side of the closing sleeve is threaded with a locking ring, and the inner diameter of the locking ring is consistent with the outer conical surface of the closing sleeve. When the locking ring is tightened, it contacts the outer conical surface of the closing sleeve, causing it to contract radially. The inner sidewall of the closing sleeve is provided with an anti-slip pad.

[0007] Furthermore, both of the oil casing bodies have sealing grooves on their opposite end faces, the two sealing grooves are staggered, and each sealing groove has a hollow sealing ring. Furthermore, the outer circumferential surface of the locking ring is knurled.

[0008] Furthermore, the load-sharing component includes a slip ring disposed on the outside of the connector pipe, and the inner diameter of the slip ring is smaller than the outer diameter of the locking ring. A sliding groove for axial movement of the slip ring is provided on the outer wall of the connector pipe. A plurality of insert rods are movably disposed through the wall of the connector pipe, and a receiving hole for the insert rods to pass through is provided on the wall of the connector pipe.

[0009] Furthermore, the number of the insertion rods is not less than two, and one end of the insertion rod is provided with a wedge block, which is located on the outside of the joint fitting. When the slip ring moves toward the middle of the connector fitting, the wall of the slip ring presses against the inclined surface of the wedge, and the wedge drives the insertion rod to move toward the inside of the connector fitting.

[0010] Furthermore, a limiting ring is fitted on the insertion rod, and a first spring is fitted on the rod segment located in the receiving hole. The two ends of the first spring abut against the bottom surface of the receiving hole and the limiting ring, respectively. A through hole is provided on the oil casing body, and a piston is slidably connected in the through hole. One end of a sliding rod is connected to the piston, and the other end of the sliding rod is slidably connected in the insertion rod. A second spring is fitted on the sliding rod, and the two ends of the second spring abut against the opposite surfaces of the insertion rod and the piston, respectively. An air cavity is formed between the upper surface of the piston and the lower surface of the insertion rod. An air passage is provided in the oil casing body, one end of the air passage is connected to the air cavity, and the other end of the air passage is connected to the corresponding hollow sealing ring.

[0011] Furthermore, each of the two slip rings is provided with a locking piece on the side closest to each other. The locking piece includes a plug strip connected to the outer wall of the slip ring, and the plug strip is made of elastic material. The end of the plug strip is integrally formed with a snap-fit ​​block.

[0012] Furthermore, the snap-fit ​​block has a trapezoidal protrusion structure with an inclined surface, and the inclination angle α of the inclined surface of the snap-fit ​​block is greater than 90 degrees.

[0013] Furthermore, the number of locking plates is not less than two, and the wall of the connector fitting is provided with an L-shaped groove for the locking plates to be inserted.

[0014] 1. In this invention, the port clamping component generates a tightening force when installed at both ends of the connector fitting, further securing the ends of the casing body and restricting axial relative sliding between the casing body and the connector fitting. During the installation of the port clamping component, the drive load-sharing component moves radially along the casing body and presses against its outer peripheral wall, forming an auxiliary support structure between the outer peripheral wall of the casing body and the inner wall of the connector fitting, reducing stress concentration on the threads of both the casing body and the connector fitting. The combined effect of these two components reduces stripping and wear caused by vibration or alternating loads, and prevents leakage due to gaps in the threaded sealing area.

[0015] 2. In this invention, because the diameter of the wall of the constriction sleeve gradually decreases from the side near the joint fitting to the far end, the contraction force can be evenly applied to the end of the casing body, thereby achieving further tightening of the casing body. Furthermore, the anti-slip pad fixedly installed or bonded to the inner wall of the constriction sleeve increases the friction between the two during the process of the constriction sleeve tightening the casing body, effectively preventing relative sliding between the casing body and the constriction sleeve.

[0016] 3. In this invention, when the locking block is inserted into the L-shaped groove, the inclined surface greater than 90 degrees causes greater friction and engagement force between the inclined surface and the L-shaped groove wall when the locking block is subjected to a tensile force along the axial direction of the groove wall. Because of the larger inclination angle, the component of the tensile force perpendicular to the inclined surface is larger, thereby increasing the pressure between the locking block and the groove wall. The increased pressure leads to increased friction, effectively preventing the locking block from loosening from the L-shaped groove, thus ensuring the locking effect of the locking plate on the slip ring and guaranteeing the stable operation of the load-sharing component. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0018] Figure 1 This is a schematic diagram of the installation of the oil casing body according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the joint fitting in an embodiment of the present invention; Figure 3 This is a partial cross-sectional view of an embodiment of the present invention; Figure 4 This is an embodiment of the present invention. Figure 1 A magnified structural diagram of part A in the middle; Figure 5 This is an embodiment of the present invention. Figure 3 A magnified structural diagram of section B in the middle; Figure 6 This is a schematic diagram of the slip ring structure according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the installation of the locking plate according to an embodiment of the present invention; Figure 8 This is a diagram showing the state changes of the piston in an embodiment of the present invention.

[0019] The labels in the diagram represent: 100, main body of the oil casing; 110, sealing groove; 200, joint fitting; 300, port snap-fit ​​fitting; 301, closing sleeve; 302, locking ring; 303, anti-slip pad; 400, load-sharing component; 401, slip ring; 402, sliding groove; 403, insertion rod; 404, perforation; 405, wedge block; 406, limiting ring; 407, first spring; 408, locking plate; 4081, insertion strip; 4082, snap-fit ​​block; 409, L-shaped groove; 4010, sliding rod; 4011, piston; 4012, second spring; 500, hollow sealing ring. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] The present invention will be further described below with reference to embodiments.

[0022] Example 1, referring to Figures 1-3The first embodiment of the present invention provides an oil casing gas-tight coupling structure, including two oil casing bodies 100 and a connector fitting 200. The outer sides of the connecting ends of the two oil casing bodies 100 are provided with external threads, and the inner sides of both ends of the connector fitting 200 are provided with internal threads adapted to the external threads. When the opposite end faces of the two oil casing bodies 100 abut against each other, the connector fitting 200 is used to be sleeved on the two oil casing bodies 100.

[0023] Currently, the existing installation of the casing body 100 and the fitting 200 improves the sealing performance between the casing body 100 and the fitting 200 by improving the thread profile. However, in actual use, the casing body 100 is also subjected to various dynamic loads during oil extraction. Under long-term working conditions, vibration or alternating loads cause axial relative sliding of the thread contact surface, leading to stripping. This results in the destruction of the oxide layer on the surface of the casing body 100 and the fitting 200, direct metal-to-metal friction, the formation of wear debris, and accelerated wear, causing gaps in the threaded sealing area and resulting in leakage.

[0024] The present invention also includes: port clamps 300 detachably installed at both ends of the connector fitting 200, the port clamps 300 being used to further secure the ends of the oil casing body 100; and load-sharing members 400 installed inside the port clamps 300, the load-sharing members 400 being used to reduce stress concentration on the threads of the oil casing body 100 and the connector fitting 200.

[0025] During the process of the port clamp 300 being installed in the connector fitting 200, the drive load sharing member 400 moves along the radial direction of the casing body 100 and abuts against the outer peripheral wall of the casing body 100, so as to form an auxiliary support structure between the outer peripheral wall of the casing body 100 and the inner wall of the connector fitting 200.

[0026] Specifically, the port clamp 300 can be composed of a split clamp and a wedge-shaped locking ring. The inner surface of the split clamp is coated with a wear-resistant coating, such as a tungsten carbide coating with a thickness of 50~100μm, with a friction coefficient ≤0.15, to avoid damage to the wedge-shaped locking ring on the surface of the oil casing during clamping. Two semi-circular clamps are made of high-strength alloy steel, with grooves on the inner side that match the outer wall of the oil casing body 100. They are connected into a ring by bolts to provide radial clamping force. The outer side of the split clamp is provided with a tapered thread that mates with the inner tapered surface of the wedge-shaped locking ring. When the wedge-shaped locking ring is tightened, an axial component force is generated, which is converted into radial clamping force to enhance the fastening effect.

[0027] Specifically, the load-sharing component 400 can be made of high-strength alloy steel pins. The pins are inserted perpendicular to the axis of the casing body 100, with a diameter of 10~20mm and a length covering the casing wall thickness plus the joint gap. They bear the radial shear force between the casing body 100 and the joint fitting 200, reducing the stress on the thread roots.

[0028] Specifically, when the port clamp 300 is installed at both ends of the connector fitting 200, it generates a tightening force, further securing the ends of the casing body 100 and restricting axial relative sliding between the casing body 100 and the connector fitting 200. During the installation of the port clamp 300, the drive load-sharing component 400 moves radially along the casing body and abuts against its outer peripheral wall, forming an auxiliary support structure between the outer peripheral wall of the casing body 100 and the inner wall of the connector fitting 200, reducing stress concentration on the threads of the casing body 100 and the connector fitting 200. Together, these components reduce thread stripping and wear caused by vibration or alternating loads, and prevent leakage due to gaps in the threaded sealing area.

[0029] Example 2, refer to Figures 1-2 This is the second embodiment of the present invention. The difference between this embodiment and the first embodiment is that the port snap-fit ​​300 includes a closing sleeve 301 that is slidably connected to the end of the connector pipe fitting 200. The diameter of the wall of the closing sleeve 301 gradually decreases from the side near the connector pipe fitting 200 to the far end, and the minimum inner diameter of the closing sleeve 301 is equal to the diameter of the oil casing body 100. An anti-slip pad 303 is fixedly installed or adhered to the inner wall of the closing sleeve 301.

[0030] The outer side of the closing sleeve 301 is threaded with a locking ring 302, and the inner diameter of the locking ring 302 is consistent with the outer conical surface of the closing sleeve 301. The outer circumferential surface of the locking ring 302 is knurled to facilitate the locking ring 302 to tighten the closing sleeve 301 to limit the oil casing body 100. When the locking ring 302 is tightened, it contacts the outer conical surface of the closing sleeve 301, causing it to contract radially.

[0031] Specifically, when the port clamp 300 needs to be installed, first insert the connecting end of the casing body 100 into the closing sleeve 301 at the end of the connector fitting 200, and then rotate the casing body 100 or the connector fitting 200. In this way, the casing body 100 and the connector fitting 200 are threaded together. Since the minimum inner diameter of the closing sleeve 301 is equal to the diameter of the casing body 100, in the initial state, due to friction and the threaded installation method, the two are in a relatively tight fit. Next, manually or using a tool such as a wrench, the knurled area on the outer circumference of the locking ring 302 is applied, and the operator rotates the locking ring 302. As the locking ring 302 is tightened, it gradually moves inward along the outer conical surface of the closing sleeve 301. During this process, the closing sleeve 301 is compressed by the locking ring 302, resulting in radial contraction.

[0032] Because the diameter of the wall of the constriction sleeve 301 gradually decreases from the side near the joint fitting 200 to the far end, its contraction force can be evenly applied to the end of the casing body 100, thereby further tightening the casing body 100. The anti-slip pad 303, fixedly installed or bonded to the inner wall of the constriction sleeve 301, increases the friction between the two during the process of the constriction sleeve 301 tightening the casing body 100, effectively preventing relative sliding between the casing body 100 and the constriction sleeve 301.

[0033] Specifically, through the above-described process, the clamping force of the retaining sleeve 301 on the end of the casing body 100 is greatly increased, making the connection between the casing body 100 and the joint fitting 200 tighter and more stable. This reduces axial relative sliding caused by vibration or alternating loads during oil production, effectively preventing thread stripping and ensuring the stability of the casing connection, thereby enhancing sealing performance. It effectively prevents leakage caused by gaps in the threaded sealing area, ensuring the normal operation of oil production. The remaining structure is the same as in Embodiment 1.

[0034] Example 3, referring to Figures 1-7 This is the third embodiment of the present invention. The difference between this embodiment and the first embodiment is that the load-sharing component 400 includes a slip ring 401 that is slidably installed on the outside of the connector pipe 200, and the inner diameter of the slip ring 401 is smaller than the outer diameter of the locking ring 302. A sliding groove 402 for axial movement of the slip ring 401 is provided on the outer wall of the connector pipe 200. A plurality of insert rods 403 are movably disposed through the wall of the connector pipe 200, and a receiving hole for the insert rods 403 to pass through is provided on the wall of the connector pipe 200.

[0035] Reference Figure 3 and Figure 5Both oil casing bodies 100 have sealing grooves 110 on their opposite end faces. The two sealing grooves 110 are staggered. Each sealing groove 110 has a hollow sealing ring 500. There are no fewer than two insertion rods 403. One end of the insertion rod 403 is provided with a wedge 405, and the wedge 405 is located on the outside of the joint fitting 200. When the slip ring 401 moves toward the middle of the joint fitting 200, the wall of the slip ring 401 presses against the inclined surface of the wedge 405, and the wedge 405 drives the insertion rod 403 to move toward the inside of the joint fitting 200.

[0036] Specifically, the hollow sealing ring 500 is made of high-temperature resistant material, and the opposite end faces of the two oil casing bodies 100 are the sealing surfaces. During the tightening process of the locking ring 302, the locking ring 302 continuously moves closer to the middle of the connector fitting 200. While moving, it causes the slip ring 401 to move axially within the sliding groove 402. When the slip ring 401 moves towards the middle of the connector fitting 200, its wall will press against the inclined surface of the wedge block 405. The wedge block 405 is connected to the insertion rod 403. After being pressed by the slip ring 401, the wedge block 405 drives the insertion rod 403 to move towards the inside of the connector fitting 200, pressing against the outer peripheral wall of the oil casing body 100 and inserting into the receiving hole on the connector fitting 200, thus forming an effective auxiliary support structure between the outer peripheral wall of the oil casing body 100 and the inner wall of the connector fitting 200.

[0037] Reference Figure 5 and Figure 8 A limiting ring 406 is fitted on the insertion rod 403. A first spring 407 is fitted on the rod section of the insertion rod 403 located in the receiving hole. The two ends of the first spring 407 abut against the bottom surface of the receiving hole and the limiting ring 406, respectively. A through hole 404 is provided on the oil casing body 100. A piston 4011 is slidably connected in the through hole 404. One end of a slide rod 4010 is connected to the piston 4011. The other end of the slide rod 4010 is slidably connected in the insertion rod 403. A second spring 4012 is fitted on the slide rod 4010. The two ends of the second spring 4012 abut against the opposite surfaces of the insertion rod 403 and the piston 4011, respectively. An air cavity is formed between the upper surface of the piston 4011 and the lower surface of the insertion rod 403. An air passage is provided in the oil casing body 100. One end of the air passage is connected to the air cavity, and the other end of the air passage is connected to the corresponding hollow sealing ring 500.

[0038] Specifically, the first spring 407 facilitates the removal of the port latch 300 or the adjustment of the oil casing body 100. The first spring 407 applies an outward force to the limiting ring 406, thereby driving the insertion rod 403 to move outward and reset, so that the insertion rod 403 is disengaged from the outer peripheral wall of the oil casing body 100, which facilitates subsequent operations. When the slip ring 401 does not compress the wedge block 405 and the insertion rod 403, the elastic support of the first spring 407 keeps the insertion rod 403 in the inner wall of the connector fitting 200, so as not to extend into the inner cavity of the connector fitting 200, thus avoiding affecting the threaded installation of the oil casing body 100 in the inner cavity of the connector fitting 200. The bottom outer peripheral surface of the insertion rod 403 is provided with a sealing rubber ring to ensure the airtightness of the air cavity formed between the insertion rod 403 and the piston 4011.

[0039] In this optional embodiment, after inserting the two oil casing bodies 100 into the end caps 301 and bringing their opposite end faces into contact, the two hollow sealing rings 500 abut against the corresponding end faces of the corresponding oil casing bodies 100, thereby forming two seals, improving sealing performance, and combining Figure 8 As shown, by moving the two slip rings 401 toward the center of the connector fitting 200, the wedge block 405 is forced to move toward the axis of the oil casing body 100. At this time, the limiting ring 406 moves downward, compressing the first spring 407. Simultaneously, the slide rod 4010 and piston 4011 move downward, and the second spring 4012 is in its natural state. Figure 8 From the state shown in the left diagram to the state shown in the middle diagram, it should be noted that the volume of the air chamber does not change from the state shown in the left diagram to the state shown in the middle diagram, and the air passage is always connected to the air chamber. After all components are installed in place, the oil casing body 100 begins to transport oil and gas. When the pressure of the oil and gas transported in the oil casing body 100 increases, due to the extremely strong penetrating ability of high-pressure gas molecules, it may cause a slight relative displacement or separation of the sealing contact surface, resulting in a decrease in the sealing effect of the hollow sealing ring 500 and easily causing leakage problems. Figure 8From the state shown in the middle diagram to the state shown in the right diagram, when the oil and gas pressure increases, the pressure of the oil and gas in the lower part of the perforation 404 on the piston 4011 increases, causing the piston 4011 to move upward a greater distance. During this process, the slide rod 4010 slides upward along the inside of the insert rod 403, and the second spring 4012 is compressed, allowing more gas to enter the gas passage in the gas chamber. Consequently, more gas enters the hollow sealing ring 500, making the hollow sealing ring 500 more bulging and harder, increasing the pressure of the hollow sealing ring 500 on the sealing surface. Increased contact pressure prevents oil and gas from leaking from the sealing surface. Furthermore, the temperature of high-pressure oil and gas is typically higher. Higher temperatures cause the hollow sealing ring 500 to become softer and less elastic, leading to decreased sealing performance. By inflating the hollow sealing ring 500, it is hardened, thereby improving sealing performance. Furthermore, by adaptively improving the sealing performance of the hollow sealing ring 500 according to the oil and gas pressure within the oil casing body 100, not only is the risk of high-pressure leakage eliminated, but the problem of thermal relaxation leakage in traditional seals is also solved.

[0040] Reference Figure 6 and Figure 7 Each of the two slip rings 401 has a locking piece 408 welded or fixedly installed on the side closest to each other. The locking piece 408 includes a plug strip 4081 connected to the outer wall of the slip ring 401. The plug strip 4081 is made of elastic material, and the end of the plug strip 4081 is integrally formed with a snap-fit ​​block 4082. The number of locking pieces 408 is not less than two. The wall of the connector fitting 200 is provided with an L-shaped groove 409 for the locking piece 408 to be inserted.

[0041] Specifically, as the slip ring 401 moves continuously, because the insertion strip 4081 of the locking plate 408 is made of elastic material, the locking plate 408 inserts into the L-shaped groove 409 on the wall of the connector fitting 200. During insertion, the locking block 4082 is squeezed by the groove wall of the L-shaped groove 409, causing the insertion strip 4081 to undergo elastic deformation. When the locking block 4082 passes the corner of the L-shaped groove 409, the insertion strip 4081 returns to its elasticity, and the locking block 4082 engages in the transverse groove of the L-shaped groove 409, thereby fixing the locking plate 408 in the L-shaped groove 409, further restricting the axial movement of the slip ring 401, and keeping the insertion rod 403 pressed against the outer peripheral wall of the oil casing body 100. During disassembly, force needs to be applied in the opposite direction to deform the insertion strip 4081 again, and the locking block 4082 can be removed from the transverse groove of the L-shaped groove 409, thus releasing the lock on the slip ring 401. The remaining structure is the same as that in Example 2.

[0042] Example 4, refer to Figure 7 This is the fourth embodiment of the present invention. The difference between this embodiment and the second embodiment is that the snap-fit ​​block 4082 has a trapezoidal protrusion structure with an inclined surface, and the inclination angle α of the inclined surface of the snap-fit ​​block 4082 is greater than 90 degrees.

[0043] Specifically, this special trapezoidal protrusion structure allows the inclined surface of the locking piece 408 to better fit against the wall of the L-shaped groove 409 after insertion. The inclination angle greater than 90 degrees ensures a tighter contact between the locking block 4082 and the groove wall, preventing gaps between the locking block 4082 and the L-shaped groove 409 and thus eliminating any signs of loosening of the slip ring 401. Simultaneously, the larger inclination angle causes the locking block 4082 to exert a certain degree of compression deformation on the groove wall during insertion, further filling any potential tiny gaps and enhancing the overall sealing and stability of the structure.

[0044] Specifically, when the locking block 4082 is inserted into the L-shaped groove 409, the inclined surface greater than 90 degrees causes the locking block 4082 to generate greater friction and engagement force between the inclined surface and the groove wall of the L-shaped groove 409 when subjected to a tensile force along the axial direction of the groove wall. Because the inclination angle is large, the component of the tensile force perpendicular to the inclined surface is larger, thereby increasing the pressure between the locking block 4082 and the groove wall. The increased pressure leads to increased friction, effectively preventing the locking block 4082 from loosening from the L-shaped groove 409, thus ensuring the locking effect of the locking piece 408 on the slip ring 401 and ensuring the stable operation of the load-sharing component 400. The remaining structure is the same as that in Embodiment 3.

[0045] Based on embodiments 1-4, the working principle of the present invention is as follows: To address the problem of thread stripping and wear leakage in existing oil casing during oil extraction due to dynamic loads, this invention solves the sealing failure problem of the oil casing body 100 under dynamic loads by having a port clamp 300 and a load-sharing component 400 work together. The port clamp 300 applies a radial clamping force to the end of the oil casing, suppressing axial sliding of the threaded contact surface. During the installation of the port clamp 300, the load-sharing component 400 is driven to work, driving the insertion rod 403 to press against the outer peripheral wall of the oil casing body 100 to form an auxiliary support structure, which bears the radial shear force, thus reducing the phenomenon of leakage caused by gaps in the threaded sealing parts of the oil casing body 100 and the joint fitting 200.

[0046] 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 the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A gas-tight coupling structure for an oil casing, comprising two oil casing bodies (100) and a connector fitting (200), wherein the outer sides of the connecting ends of the two oil casing bodies (100) are provided with external threads, and the inner sides of both ends of the connector fitting (200) are provided with internal threads adapted to the external threads; when the opposite end faces of the two oil casing bodies (100) abut against each other, the connector fitting (200) is used to be sleeved on the two oil casing bodies (100), characterized in that, Also includes: Port clamps (300) are detachably installed at both ends of the connector fitting (200). The port clamps (300) are used to further secure the ends of the oil casing body (100). A load-sharing component (400) is provided inside the port snap-fit ​​component (300). The load-sharing component (400) is used to reduce the stress concentration on the threads of the oil casing body (100) and the joint fitting (200). During the process of the port snap-fit ​​(300) being installed in the connector fitting (200), the drive load sharing component (400) moves along the radial direction of the oil casing body (100) and abuts against the outer peripheral wall of the oil casing body (100) to form an auxiliary support structure between the outer peripheral wall of the oil casing body (100) and the inner wall of the connector fitting (200). Both of the two oil casing bodies (100) are provided with sealing grooves (110) on their opposite end faces. The two sealing grooves (110) are staggered from each other, and each sealing groove (110) is provided with a hollow sealing ring (500). The load-sharing component (400) includes a slip ring (401) disposed on the outside of the connector pipe fitting (200), and the inner diameter of the slip ring (401) is smaller than the outer diameter of the locking ring (302). A sliding groove (402) for axial movement of the slip ring (401) is provided on the outer wall of the connector pipe fitting (200). A plurality of insert rods (403) are movably disposed through the wall of the connector pipe fitting (200), and a receiving hole for the insert rods (403) to pass through is provided on the wall of the connector pipe fitting (200). The number of the insert rods (403) is not less than two, and one end of the insert rod (403) is provided with a wedge (405), and the wedge (405) is located on the outside of the connector fitting (200); When the slip ring (401) moves toward the middle of the connector fitting (200), the wall of the slip ring (401) presses against the inclined surface of the wedge block (405), and the wedge block (405) drives the insertion rod (403) to move toward the inside of the connector fitting (200); A limiting ring (406) is fitted on the insert rod (403). A first spring (407) is fitted on the rod segment of the insert rod (403) located in the receiving hole. The two ends of the first spring (407) abut against the bottom surface of the receiving hole and the limiting ring (406), respectively. A through hole (404) is provided on the oil casing body (100). A piston (4011) is slidably connected in the through hole (404). One end of a sliding rod (4010) is connected to the piston (4011). The other end is slidably connected to the insert rod (403). A second spring (4012) is sleeved on the slide rod (4010). The two ends of the second spring (4012) abut against the opposite surfaces of the insert rod (403) and the piston (4011). An air cavity is formed between the upper surface of the piston (4011) and the lower surface of the insert rod (403). An air passage is provided in the oil casing body (100). One end of the air passage is connected to the air cavity, and the other end of the air passage is connected to the corresponding hollow sealing ring (500).

2. The gas-tight coupling structure for oil casing according to claim 1, characterized in that, The port snap-fit ​​(300) includes a closing sleeve (301) disposed at the end of the connector fitting (200). The diameter of the wall of the closing sleeve (301) gradually decreases from the side near the connector fitting (200) to the far end, and the minimum inner diameter of the closing sleeve (301) is equal to the diameter of the oil casing body (100). The outer side of the closing sleeve (301) is threaded with a locking ring (302), and the inner diameter of the locking ring (302) is consistent with the outer conical surface of the closing sleeve (301). When the locking ring (302) is tightened, it contacts the outer conical surface of the closing sleeve (301) to make it radially contracted. The inner side wall of the closing sleeve (301) is provided with an anti-slip pad (303).

3. The gas-tight coupling structure for oil casing according to claim 2, characterized in that, The outer circumferential surface of the locking ring (302) is knurled.

4. The gas-tight coupling structure for oil casing according to claim 3, characterized in that, Both slip rings (401) are provided with locking pieces (408) on the side close to each other. The locking piece (408) includes a plug strip (4081) connected to the outer wall of the slip ring (401), and the plug strip (4081) is made of elastic material. The end of the plug strip (4081) is integrally formed with a snap block (4082).

5. The gas-tight coupling structure for oil casing according to claim 4, characterized in that, The snap-fit ​​block (4082) has a trapezoidal protrusion structure with an inclined surface, and the inclination angle α of the inclined surface of the snap-fit ​​block (4082) is greater than 90 degrees.

6. The gas-tight coupling structure for oil casing according to claim 5, characterized in that, The number of locking plates (408) is not less than two, and the wall of the connector fitting (200) is provided with an L-shaped groove (409) for the locking plates (408) to be inserted.

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