Casing body small hole high bearing sealing structure and application thereof

Abstract

The application discloses an oil casing pipe body small hole high bearing sealing structure and application thereof, which comprises a bearing sealing female structure and a bearing sealing male structure which are arranged in the through pipe body and are matched with each other. The bearing sealing female structure comprises a female sealing surface which is arranged from the outer wall surface to the inner wall surface of the pipe body and a sealing female threaded hole which is connected to the end of the female sealing surface, and a bearing shoulder is arranged between the end of the female sealing surface and the upper end of the sealing female threaded hole. The bearing sealing male structure comprises a stud head, a male sealing surface which is connected to the lower end surface of the stud head and is matched with the female sealing surface in an interference fit, and a sealing male threaded column which is connected to the lower end surface of the male sealing surface and is matched with the sealing female threaded hole, and a torsion resisting shoulder is reserved between the lower end surface of the male sealing surface and the upper end of the male threaded column, and the torsion resisting shoulder is matched with the bearing shoulder. The application can effectively improve the sealing performance of the well completion pipe column, and further realizes the well completion and reconstruction of high temperature and high pressure ultra-deep wells.

Description

Technical Field

[0001] This invention relates to the field of high-temperature and high-pressure drilling and completion technology in the oil and gas industry, and particularly to a high-load-bearing sealing structure for small holes in oil casing and its application. Background Technology

[0002] In oil and gas exploration and development, oil and gas extraction activities are gradually moving towards more complex and extreme geological environments. This is especially true for the development of deep oil and gas resources, which are located deep underground and typically characterized by high temperatures (temperatures exceeding 140°C), high pressures (pressures exceeding 100 MPa), and significant well depths (greater than 5000 meters). Furthermore, the formation media contain high concentrations of corrosive components such as CO2, H2S, and Cl-. These harsh geological conditions place high demands on well completion technologies.

[0003] Currently, a key technical aspect of well completion string or tool technology is to use a different material from the main body of the tubing or tool to create a sealing structure for the small holes in the tubing. Because the tubing is subjected to harsh conditions of high temperature and high pressure downhole, the sealing capacity of this structure determines the load-bearing capacity and operating limit of the tubing. However, there is currently a lack of a good solution to achieve high-pressure sealing of the small holes in the tubing, resulting in the limited application of well completion strings or tools in ultra-deep well conditions and frequent accidents. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a high load-bearing sealing structure with small holes in the casing and tubing and its application, which can effectively improve the sealing performance of the completion string, thereby solving the completion and stimulation problems of high-temperature, high-pressure, and ultra-deep wells.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: According to a first aspect of the present invention, a high load-bearing sealing structure for a small hole in an oil casing is provided, comprising a load-bearing sealing female structure formed through the inner and outer walls of the casing body, and a load-bearing sealing male structure that cooperates with the load-bearing sealing female structure. The bearing sealing female structure includes a female sealing surface opened along the outer wall surface of the tube body to the inner wall surface and a sealing female threaded hole connected to the end of the female sealing surface, and a bearing shoulder is provided between the end of the female sealing surface and the upper end of the sealing female threaded hole. The bearing sealing male structure includes a stud head, a male sealing surface connected to the lower end face of the stud head and interference fit with the female sealing surface, and a sealing male threaded post connected to the lower end face of the male sealing surface and matched with the sealing female threaded hole. A torsional shoulder is reserved between the lower end face of the male sealing surface and the upper end of the male threaded post, and the torsional shoulder matches the bearing shoulder.

[0006] In one possible implementation of the first aspect, the upper end face of the stud head is provided with a sealant storage groove, and the sealant storage groove is provided with a plurality of sealant flow channels extending to the male sealing surface.

[0007] In one possible implementation of the first aspect, several of the sealant channels are uniformly distributed around the central axis of the stud head.

[0008] In one possible implementation of the first aspect, the sealant storage tank contains a sealant, which includes epoxy resin sealant, acrylic resin sealant, polyester resin sealant, phenolic resin sealant, or amino resin sealant.

[0009] In one possible implementation of the first aspect, both the female sealing surface and the male sealing surface are inverted conical surfaces, and the angle between the conical surface and the central axis is not less than 50 degrees.

[0010] In one possible implementation of the first aspect, the load-bearing sealing structure is made of any one of titanium alloy, aluminum alloy, or magnesium-aluminum alloy.

[0011] In one possible implementation of the first aspect, the titanium alloy material comprises: Ti-2Al-(0.1~2.0)%Fe alloy, Ti-3Al-2.5V alloy, Ti-6Al-4V alloy, Ti-4Al-2.5V alloy, Ti-4Al-2.5V-(0.9~1.6)%Fe-(0.1~0.35)%O alloy, Ti-6Al-4V-(0.7~1.6)%Fe alloy, Ti-6Al-4V-(0.1~1.1)%Ni-(0.3~1.0)%Nb alloy, or Ti-5.5Al-4.5V-2Zr-1Mo alloy, all of which are mass percentages; The aluminum alloy material includes Al-Cu-Mg alloys, Al-Cu-Mg-Ag alloys, Al-Mg-Si alloys, or Al-Zn-Mg-Cu alloys. The magnesium-aluminum alloy materials include Mg-Al-Cu-Zn alloys, Mg-Al-Cu-Zr alloys, Mg-Al-Cu-Ni alloys, Mg-Al-Mn-Zr alloys, or Mg-Al-Ca-Mn-Cu-Ni alloys.

[0012] In one possible implementation of the first aspect, the threads on the sealing female threaded hole and the sealing male threaded post are cylindrical threads, tapered threads, variable pitch threads, or variable taper threads.

[0013] In one possible implementation of the first aspect, the cylindrical surface of the stud head has a polygonal structure.

[0014] According to a second aspect of the present invention, an application of a high load-bearing sealing structure for a small orifice in an oil casing is provided, which is applied to well completion tools.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: This invention provides a high-load-bearing sealing structure for the small orifice of the casing and tubing. Through the unique design of a load-bearing sealing female structure and a load-bearing sealing male structure, the combination of the sealing surface (interference fit between the female and male sealing surfaces) and the anti-torsion shoulder, and the assistance of sealing threads, the sealing limit is greatly improved, even achieving a gas-tight seal effect. This effectively enhances the sealing strength of the small orifice in the casing and tubing, enabling it to withstand extreme downhole environments with high temperatures and pressures (temperatures exceeding 140°C and pressures exceeding 100MPa), and maintain long-term sealing stability in formation media containing high concentrations of corrosive components (such as CO2, H2S, and Cl-). This significantly improves the sealing performance and load-bearing capacity of the completion string. The sealing structure of this invention, through the main sealing structure design of sealing surface + anti-torsion shoulder + sealing threads, not only simplifies the structure but also makes the preparation and installation process more convenient. Simultaneously, the matching design of the anti-torsion shoulder and the load-bearing shoulder provides intuitive feedback on the proper engagement, ensuring the integrity and uniformity of the sealing structure during mass production and installation, improving the efficiency and success rate of installation. By transferring the high-stress state from the traditional sealing threads to the anti-torsion shoulder, thread damage caused by excessive stress is effectively avoided, extending the service life of the sealing structure and improving the reliability of the entire completion string. Because the sealing structure of this invention is rationally designed, easy to manufacture and install, and ensures the integrity and uniformity of the sealing structure, it can effectively reduce production and installation costs in practical applications. Furthermore, by improving the load-bearing capacity and sealing performance of the completion string, this invention can be more widely applied in complex geological conditions such as ultra-deep wells.

[0016] Furthermore, the load-bearing sealing structure is mainly made of high-strength, low-density alloy materials such as titanium and titanium alloys, aluminum alloys, and magnesium-aluminum alloys. The selection of materials not only ensures the strength and sealing performance of the high load-bearing sealing structure, but also allows for the use of different alloy materials according to different environmental conditions and operating processes, making it widely applicable and improving construction efficiency and success rate.

[0017] Furthermore, in addition to adopting the main sealing structure design of sealing surface + anti-torsion shoulder + sealing thread, an auxiliary sealant protection design is added to the upper part of the bearing sealing male structure. After the main sealing structure is fastened, the sealant fills and reacts and cures in the gaps of the bearing shoulder and the sealing male and female threads, enhancing the high bearing sealing effect on the small holes of the oil casing pipe. It can effectively protect the structure from interference, damage, erosion, pollution or even human-caused damage that may be encountered during testing, transportation, construction and repeated operations from the time the structure is fastened to its application in the well. It can not only ensure the reliability of the installation and use of the main sealing structure, but also further increase the sealing effect. The structure is simple, reliable, protective, flexible and convenient, and reduces accidental failure. To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the installation of a high load-bearing sealing structure for a small hole in an oil casing according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the load-bearing sealing male structure in a high load-bearing sealing structure for a small hole in an oil casing according to an embodiment of the present invention; Figure 3 This is a cross-sectional view of the load-bearing sealing male structure in a high-load-bearing sealing structure for a small orifice in an oil casing according to an embodiment of the present invention. Figure 4 This is a lower schematic diagram of the load-bearing sealing male structure in a high load-bearing sealing structure for a small hole in an oil casing according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the load-bearing sealing mother structure in a high load-bearing sealing structure for a small hole in an oil casing according to an embodiment of the present invention.

[0020] In the figure: 1-pipe body; 2-bearing sealing female structure; 20-female sealing surface; 21-sealing female threaded hole; 22-bearing shoulder; 3-bearing sealing male structure; 30-stud head; 300-sealant storage tank; 301-sealant flow channel; 31-male sealing surface; 32-male threaded stud; 33-torsion shoulder. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Combination Figures 1 to 5 As shown, this invention provides a high-load-bearing sealing structure for a small orifice in a casing pipe, primarily to address the problem of insufficient sealing performance of completion tubing or tools in high-temperature, high-pressure, ultra-deep well environments in the prior art. This high-load-bearing sealing structure for a small orifice in the casing pipe includes a load-bearing sealing female structure 2 extending through the inner and outer walls of the casing body 1, and a load-bearing sealing male structure 3 that cooperates with the load-bearing sealing female structure 2.

[0023] It should be understood that the pipe body 1, as the basic structure of the oil casing, is made of materials that can withstand the operating requirements of high temperature and high pressure environments, and is usually made of high-strength, corrosion-resistant alloy materials.

[0024] like Figure 5 As shown, the bearing sealing female structure 2 includes a female sealing surface 20 opened along the outer wall surface of the pipe body 1 to the inner wall surface and a sealing female threaded hole 21 connected to the end of the female sealing surface 20. A bearing shoulder 22 is provided between the end of the female sealing surface 20 and the upper end of the sealing female threaded hole 21.

[0025] like Figure 2 , Figure 3 and Figure 4 As shown, the bearing sealing male structure 3 includes a stud head 30, a male sealing surface 31 connected to the lower end face of the stud head 30 and interference-fitted with the female sealing surface 20, and a sealing male threaded post 32 connected to the lower end face of the male sealing surface 31 and matched with the sealing female threaded hole 21. A torsional shoulder 33 is reserved between the lower end face of the male sealing surface 31 and the upper end of the male threaded post 32, and the torsional shoulder 33 matches the bearing shoulder 22.

[0026] Specifically, the female sealing surface 20 is opened along the outer wall surface of the pipe body 1 to the inner wall surface, forming a smooth sealing contact surface that matches the male sealing surface 31, ensuring that the interference fit between the female and male sealing surfaces 31 achieves the best sealing effect. The sealing female threaded hole 21 is located at the end of the female sealing surface 20 and is used for threaded connection with the sealing male threaded post 32, providing additional tightening force and sealing performance. The bearing shoulder 22 is provided between the end of the female sealing surface 20 and the upper end of the sealing female threaded hole 21 to withstand the torque generated during the tightening process and to prevent the sealing male structure 3 from going too deep.

[0027] The stud head 30 serves as the handle or tool contact surface during the tightening operation. It should be noted that the stud head 30 must be easy to operate and possess sufficient strength to withstand the tightening torque. The male sealing surface 31 is connected to the lower end face of the stud head 30, forming an interference fit with the female sealing surface 20 to ensure sealing performance. The sealing male threaded stud 32 is connected to the lower end face of the male sealing surface 31 and matches the sealing female threaded hole 21 to achieve a threaded connection. Its thread parameters match those of the sealing female threaded hole 21 to ensure connection strength and sealing performance. The anti-torsion shoulder 33 is reserved between the lower end face of the male sealing surface 31 and the upper end of the male threaded stud 32, used to match the bearing shoulder 22, withstand the tightening torque, and prevent torsional damage to the sealing male structure 3 during tightening.

[0028] In this embodiment, both the female sealing surface 20 and the male sealing surface 31 are metal sealing surfaces.

[0029] In use, align the male threaded post 32 of the male bearing sealing structure 3 with the female threaded hole 21 of the female bearing sealing structure 2, and begin the threading operation. As threading progresses, the anti-torsion shoulder 33 gradually approaches the bearing shoulder 22. When they contact each other, the torque is mainly borne by the bearing shoulder 22, while providing a significant resistance feedback to the stud head 30. The operator controls the threading torque based on the resistance feedback, avoiding excessive or insufficient torque, thereby mitigating the high stress distribution on the male threaded post 32 and the female threaded hole 21, and preventing thread damage to the male thread of the male bearing sealing structure 3 due to excessive stress. When the male bearing sealing structure 3 and the female bearing sealing structure 2 are fully threaded, the male sealing surface 31 and the female sealing surface 20 achieve a surface contact interference fit, forming a high sealing effect.

[0030] As can be seen, the sealing structure provided in this embodiment can withstand the fluid / gas pressure under high temperature and high pressure environments, ensuring a high-pressure sealing effect for the small orifice on the casing. The dual protection of surface contact interference fit and threaded connection achieves a high-pressure sealing effect for the small orifice on the casing. The bearing shoulder 22 and anti-torsion shoulder 33 effectively disperse the upper torque, preventing damage to the sealing structure. This sealing structure is suitable for well completion operations in harsh environments such as high temperature, high pressure, and ultra-deep wells, improving the reliability of the completion string.

[0031] In one feasible approach, combining Figure 2 , Figure 3 and Figure 4 As shown, a sealant storage groove 300 is provided on the upper end face of the stud head 30, and a plurality of sealant flow channels 301 extending to the male sealing surface 31 are provided in the sealant storage groove 300.

[0032] In other words, a sealant storage groove 300 is provided on the upper end face of the stud head 30, that is, the end away from the male sealing surface 31. A sealant flow channel 301 is provided in the sealant storage groove 300 and extends to the male sealing surface 31. The sealant storage groove 300 is used to store sealant so that during or after the threading process, the sealant can flow through the sealant flow channel 301 and fill the tiny gap between the male sealing surface 31 and the female sealing surface 20, thereby enhancing the sealing effect.

[0033] It should be noted that the shape and size of the sealant storage tank 300 are designed according to actual needs. For example, the sealant storage tank 300 is an arc-shaped groove to ensure that it can store enough sealant. The sealant flow channel 301 consists of multiple evenly distributed fine channels to ensure that the sealant can flow evenly and effectively from the sealant storage tank 300 to the male sealing surface 31 and fill the gap between it and the female sealing surface 20.

[0034] Specifically, before the coupling, an appropriate amount of sealant is filled into the sealant storage tank 300. During the coupling process, the male bearing sealing structure 3 and the female bearing sealing structure 2 are coupled together. As the stud head 30 rotates and advances, the sealant, under the pressure of compression, flows through the sealant flow channel 301 to the male sealing surface 31 and fills the tiny gap between it and the female sealing surface 20. Based on the interference fit formed between the male sealing surface 31 and the female sealing surface 20, the sealing effect is further enhanced through the filling and compression of the sealant. The sealant can fill tiny gaps caused by factors such as machining precision and material deformation, thereby improving the sealing reliability of the sealing structure. If the sealing performance deteriorates during long-term operation, the sealing effect can be restored by refilling the sealant.

[0035] In one implementation, a plurality of sealant channels 301 are evenly distributed around the central axis of the stud head 30, ensuring that the sealant can flow evenly and effectively from the sealant storage tank 300 to the male sealing surface 31 and fill the gap between it and the female sealing surface 20. In other words, the evenly distributed channels help to uniformly extrude the sealant through compression during the fastening process, forming a tighter sealing layer and thus improving the sealing effect. For example, the sealant channels 301 can be designed to be 3 to 12 in number to meet the needs of sealing structures of different materials and sizes.

[0036] In one possible implementation, the sealant contained in the sealant storage tank 300 includes, but is not limited to, the following types of sealant: epoxy resin sealant, acrylic resin sealant, polyester resin sealant, phenolic resin sealant, and amino resin sealant. Furthermore, the sealant can also be a modified resin material such as bisphenol A resin, a polymeric resin material containing various metal powders (such as copper powder, aluminum powder, iron powder, etc.), or a combination of elastic rubber material and a surface-dissolving wetting agent.

[0037] In one possible implementation, both the female sealing surface 20 and the male sealing surface 31 are inverted conical surfaces, and the angle between the conical surface and the central axis is not less than 50°. That is, both the female sealing surface 20 and the male sealing surface 31 are designed as inverted conical surfaces, meaning the outer diameter of the sealing surface is larger than the inner diameter, forming a certain taper. During the tightening process, as the stud head 30 rotates and advances, the male sealing surface 31 can gradually be squeezed and adhered to the female sealing surface 20, forming a tighter sealing layer. The angle between the conical surface and the central axis is not less than 50°, which ensures both a good sealing effect and smooth tightening.

[0038] It should be noted that the female sealing surface 20 and the male sealing surface 31 can also adopt metal-to-metal sealing forms such as conical surface to arc surface or arc surface to arc surface.

[0039] In one feasible approach, the bearing sealing structure 3 is made of any one of the following high-strength, low-density, lightweight alloy materials: titanium alloy, aluminum alloy, or magnesium-aluminum alloy. While possessing a certain strength, it can be easily dissolved by downhole high-mineralization fluids or acidic fluids, thus establishing a fluid channel inside and outside the tubing string.

[0040] Among them, titanium alloy materials include, but are not limited to: Ti-2Al-(0.1~2.0)%Fe alloy, Ti-3Al-2.5V alloy, Ti-6Al-4V alloy, Ti-4Al-2.5V alloy, Ti-4Al-2.5V-(0.9~1.6)%Fe-(0.1~0.35)%O alloy, Ti-6Al-4V-(0.7~1.6)%Fe alloy, Ti-6Al-4V-(0.1~1.1)%Ni-(0.3~1.0)%Nb alloy or Ti-5.5Al-4.5V-2Zr-1Mo alloy, all of which are mass percentages.

[0041] Aluminum alloy materials include, but are not limited to, Al-Cu-Mg alloys, Al-Cu-Mg-Ag alloys, Al-Mg-Si alloys, or Al-Zn-Mg-Cu alloys.

[0042] Magnesium-aluminum alloy materials include, but are not limited to, Mg-Al-Cu-Zn alloys, Mg-Al-Cu-Zr alloys, Mg-Al-Cu-Ni alloys, Mg-Al-Mn-Zr alloys, or Mg-Al-Ca-Mn-Cu-Ni alloys.

[0043] For example, the pipe body 1 is made of high-strength alloy steel. The material of the load-bearing sealing female structure 2 matches that of the pipe body 1. The load-bearing sealing male structure 3 is made of Ti-6Al-4V alloy, which has high strength, excellent corrosion resistance and high temperature resistance, and is suitable for sealing requirements in harsh environments such as high-temperature, high-pressure, and ultra-deep wells. Both the female sealing surface 20 and the male sealing surface 31 are designed as inverted conical surfaces, with an angle of 60° between the conical surface and the central axis to ensure good sealing performance. The sealant storage tank 300 is filled with high-performance epoxy resin sealant to further enhance the sealing performance of the sealing structure.

[0044] In one possible implementation, the threads on the sealing female threaded hole 21 and the sealing male threaded post 32 are cylindrical threads, tapered threads, variable pitch threads, or variable taper threads.

[0045] Specifically, cylindrical threads are the most common type of thread, with a tooth profile of a cylinder of uniform cross-section, offering advantages such as simple processing and low cost. Tapered threads have a tapered tooth profile, characterized by good self-locking performance, strong sealing, and high load-bearing capacity. Variable pitch threads refer to threads where the pitch changes axially; this design reduces frictional resistance and torque during threaded connections, making installation smoother. Variable taper threads refer to threads where the taper changes axially; this design can adapt to pipes of different diameters, improving the adaptability of the sealing structure.

[0046] In one implementation, the cylindrical surface of the stud head 30 has a polygonal structure. For example, the polygonal structure can be an equilateral polygon, such as a regular hexagon or octagon. This polygonal structure makes the stud head 30 easier to grip with a wrench or special tool, thus facilitating installation and removal. When tightening or loosening the stud head 30, the polygonal structure provides better resistance to rotation. Simultaneously, the polygonal structure has better resistance to deformation under radial forces, thereby enhancing the structural strength of the stud head.

[0047] The method for preparing a high load-bearing sealing structure for a small orifice in an oil casing according to the present invention is as follows: ①According to the requirements of well completion string operation, multiple bearing and sealing mother structures 2 are processed on the well completion casing or tool pipe body in a circumferentially evenly distributed manner. The bearing and sealing mother structures 2 on the pipe body 1 from top to bottom are the mother sealing surface 20, the bearing shoulder 22 and the sealing mother threaded hole 21.

[0048] ② A corresponding number of load-bearing sealing male structures 3 are processed using lightweight alloy materials (such as titanium and titanium alloys, aluminum alloys, magnesium-aluminum alloys, etc.). The load-bearing sealing male structures 3 are arranged from top to bottom as stud head 30, male sealing surface 31, anti-torsion shoulder 33 and sealing male threaded post 32; a sealant storage tank 300 and a sealant flow channel 301 are processed inside the stud head 30.

[0049] ③ Apply anti-sticking sealing grease or anti-sticking coating to the sealing male threaded post 32 and the sealing female threaded hole 21. Align the load-bearing sealing female structure 2 and the load-bearing sealing male structure 3 on the pipe body 1 and then tighten them. Use a tightening wrench / caliper to apply torque to the load-bearing sealing male structure 3 on the stud head 30 and tighten until the anti-torsion shoulder 33 touches the load-bearing shoulder 22 and generates a large resistance feedback. Stop tightening. At this time, the male sealing surface 31 on the load-bearing sealing male structure 3 and the female sealing surface 20 on the load-bearing sealing female structure 2 will have a metal-to-metal interference fit.

[0050] ④ Fill the sealant storage tank 300 inside the stud head 30 of the bearing sealing structure 3 with sealant. After the sealant flows out from the sealant flow channel 301, it fills the gaps of the bearing shoulder 22, the sealing surface and the sealing thread and reacts and cures, thereby enhancing the high bearing sealing effect on the small hole of the oil casing.

[0051] ⑤ Repeat steps ① to ④, fasten each load-bearing sealing female structure 2 and load-bearing sealing male structure 3 distributed on the completion casing or tool pipe into place, and after the sealant has reacted and cured, seal both ends of the completion casing or tool pipe, pressurize the inside of the pipe, test the pressure resistance of all high load-bearing sealing structures, and complete the preparation and inspection.

[0052] Example 1: On a P110 grade 3-1 / 2-inch tubing (7.34mm wall thickness), load-bearing sealing female structures 2 are machined at 0, 90, 180, and 270 degrees along the same circumference on the outer wall. Ten sets are machined on each tubing, with each set spaced 60cm apart. On each load-bearing sealing female structure 2, from top to bottom, there is a female sealing surface 20, a load-bearing shoulder 22, and a sealing female threaded hole 21. The angle between the longitudinal line of the female sealing surface 20 and the central axis of the load-bearing sealing female structure 2 is 60 degrees. A corresponding number of load-bearing sealing male structures 3 are machined using Ti-6Al-4V-0.5Ni-0.8Nb titanium alloy. The load-bearing sealing male structure 3 consists of a stud head 30, a male sealing surface 31, an anti-torsion shoulder 33, and a sealing male threaded stud 32 from top to bottom. A sealant storage tank 300 is machined inside the stud head 30, and four sets of sealant flow channels 301 are machined inside the sealant storage tank 300. The male sealing surface 31 on the load-bearing sealing male structure 3 and the female sealing surface 20 on the load-bearing sealing female structure 2 adopt a conical-to-conical metal sealing form. The machined sealing male / female threads adopt the ISO standard 3 / 8” NPT tapered sealing threads.

[0053] Apply anti-sticking sealing grease to the sealing male threaded post 32 and the sealing female threaded hole 21. Align the load-bearing sealing female structure 2 and the load-bearing sealing male structure 3 on the pipe body 1 and then tighten them. Use a tightening wrench / caliper to apply torque to the load-bearing sealing male structure 3 on the stud head 30. Stop tightening when the tightening torque value is greater than 20 Nm. At this time, the male sealing surface 31 on the load-bearing sealing male structure 3 and the female sealing surface 20 on the load-bearing sealing female structure 2 will have a metal-to-metal interference fit.

[0054] Phenolic resin sealant is filled into the sealant storage tank 300 inside the stud head 30 of the bearing sealing male structure 3. After the sealant flows out from the sealant flow channel 301, it fills the gaps in the bearing shoulder 22, the sealing surface and the sealing thread and reacts and cures, thereby enhancing the high bearing sealing effect on the small hole of the oil casing pipe.

[0055] Repeat the above steps, attach each load-bearing sealing female structure 2 and load-bearing sealing male structure 3 of the completion tubing, and use sealant to react and cure. Then transport the entire tubing string to the well site, seal both ends of the tubing body, and pressurize the inside of the tubing body. The test shows that when the internal air pressure reaches 55MPa, none of the multiple sets of high load-bearing sealing structures leaked, demonstrating high pressure resistance.

[0056] Example 2: On a P110 grade 5-1 / 2-inch sleeve (7.73mm wall thickness), six load-bearing sealing female structures 2 are machined with equal arc along the circumference at the same position on the outer wall. Eight sets are machined on each sleeve, and each set is spaced 80cm apart. On each load-bearing sealing female structure 2, from top to bottom, there is a female sealing surface 20, a load-bearing shoulder 22, and a sealing female threaded hole 21. The angle between the long line of the female sealing surface 20 and the central axis of the load-bearing sealing female structure 2 is 55 degrees. A corresponding number of load-bearing sealing male structures 3 are machined using Al-Zn-Mg-Cu aluminum alloy. The load-bearing sealing male structure 3 consists of a stud head 30, a male sealing surface 31, an anti-torsion shoulder 33, and a sealing male threaded stud 32 from top to bottom. A sealant storage tank 300 is machined inside the stud head 30, and six sets of sealant flow channels 301 are machined inside the sealant storage tank 300. The male sealing surface 31 on the load-bearing sealing male structure 3 and the female sealing surface 20 on the load-bearing sealing female structure 2 adopt a conical-to-arc metal sealing form. The machined sealing male / female threads adopt the international standard 1 / 2” ZG sealing thread.

[0057] Apply an anti-sticking coating to the sealing male threaded post 32 and the sealing female threaded hole 21. Align the load-bearing sealing female structure 2 and the load-bearing sealing male structure 3 on the pipe body 1 and then tighten them. Use a tightening wrench / caliper to apply torque to the load-bearing sealing male structure 3 on the stud head 30. Stop tightening when the tightening torque value is greater than 30 Nm. At this time, the male sealing surface 31 on the load-bearing sealing male structure 3 and the female sealing surface 20 on the load-bearing sealing female structure 2 will have a metal-to-metal interference fit.

[0058] Bisphenol A modified resin sealant is filled into the sealant storage tank 300 inside the stud head 30 of the bearing sealing male structure 3. After the sealant flows out from the sealant flow channel 301, it fills the gaps in the bearing shoulder 22, the sealing surface and the sealing thread and reacts and cures, thereby enhancing the high bearing sealing effect on the small hole of the oil casing.

[0059] Repeat the above steps, attach each load-bearing sealing female structure 2 and load-bearing sealing male structure 3 of the completion casing, and use sealant to react and cure. Then transport the entire tubing string to the well site, seal both ends of the tubing body, and pressurize the inside of the tubing body. The test shows that when the internal air pressure reaches 70MPa, none of the multiple sets of high load-bearing sealing structures leaked, demonstrating high pressure resistance.

[0060] Example 3: On a 7-inch Q125 steel sleeve (11.99mm wall thickness), eight load-bearing sealing female structures 2 are machined with equal arc along the circumference at the same position on the outer wall. Seven sets are machined on each sleeve, and each set is spaced 100cm apart. On each load-bearing sealing female structure 2, from top to bottom, there is a female sealing surface 20, a load-bearing shoulder 22, and a sealing female threaded hole 21. The angle between the long line of the female sealing surface 20 and the central axis of the load-bearing sealing female structure 2 is 75 degrees. A corresponding number of load-bearing sealing male structures 3 are machined using Mg-Al-Cu-Ni magnesium-aluminum alloy. The load-bearing sealing male structure 3 consists of a stud head 30, a male sealing surface 31, an anti-torsion shoulder 33, and a sealing male threaded stud 32 from top to bottom. A sealant storage tank 300 is machined inside the stud head 30, and nine sets of sealant flow channels 301 are machined inside the sealant storage tank 300. The male sealing surface 31 on the load-bearing sealing male structure 3 and the female sealing surface 20 on the load-bearing sealing female structure 2 adopt an arc-to-arc metal sealing form, and the machined sealing male / female threads adopt a special sealing thread with variable taper.

[0061] Apply locking grease to the sealing male threaded post 32 and the sealing female threaded hole 21. Align the load-bearing sealing female structure 2 and the load-bearing sealing male structure 3 on the pipe body 1 and then tighten them. Use a tightening wrench / caliper to apply torque to the load-bearing sealing male structure 3 on the stud head 30. Stop tightening when the tightening torque value is greater than 35 Nm. At this time, the male sealing surface 31 on the load-bearing sealing male structure 3 and the female sealing surface 20 on the load-bearing sealing female structure 2 will have a metal-to-metal interference fit.

[0062] The sealant storage tank 300 inside the stud head 30 of the bearing sealing male structure 3 is filled with a combination of polymer resin material containing metal powders such as Zn, Cu, and Ti, elastic rubber material, and surface dissolving wetting agent. After the sealant flows out from the sealant flow channel 301, it fills the gaps in the bearing shoulder 22, sealing surface, and sealing thread and reacts and cures, enhancing the high bearing capacity sealing effect on the small hole of the oil casing pipe body.

[0063] Repeat the above steps, attach each load-bearing sealing female structure 2 and load-bearing sealing male structure 3 of the completion oil casing, and use sealant to react and cure. Then transport the entire tubing string to the well site, seal both ends of the tubing body, and pressurize the inside of the tubing body. The test shows that when the internal air pressure reaches 65MPa, none of the multiple sets of high load-bearing sealing structures leaked, demonstrating high pressure resistance.

[0064] In the description of this invention, it should be understood that the terms "upper", "lower", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0065] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0066] In this invention, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0067] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0068] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0069] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of protection of the claims.

Claims

1. A high-load-bearing sealing structure for a small orifice in an oil casing, characterized in that, It includes a load-bearing sealing female structure (2) that runs through the inner and outer walls of the pipe body (1), and a load-bearing sealing male structure (3) that cooperates with the load-bearing sealing female structure (2). The bearing sealing female structure (2) includes a female sealing surface (20) opened along the outer wall surface of the tube body (1) to the inner wall surface and a sealing female threaded hole (21) connected to the end of the female sealing surface (20). A bearing shoulder (22) is provided between the end of the female sealing surface (20) and the upper end of the sealing female threaded hole (21). The bearing sealing male structure (3) includes a stud head (30), a male sealing surface (31) connected to the lower end face of the stud head (30) and interference fit with the female sealing surface (20), and a sealing male threaded post (32) connected to the lower end face of the male sealing surface (31) and matched with the sealing female threaded hole (21). A torsion shoulder (33) is reserved between the lower end face of the male sealing surface (31) and the upper end of the male threaded post (32), and the torsion shoulder (33) matches the bearing shoulder (22).

2. The high load-bearing sealing structure for the small orifice of an oil casing pipe according to claim 1, characterized in that, The upper end face of the stud head (30) is provided with a sealant storage groove (300), and a plurality of sealant flow channels (301) are provided in the sealant storage groove (300) that extend to the male sealing surface (31).

3. The high load-bearing sealing structure for the small orifice of an oil casing pipe according to claim 2, characterized in that, Several of the sealant channels (301) are evenly distributed around the central axis of the stud head (30).

4. The high load-bearing sealing structure for the small orifice of an oil casing pipe according to claim 2, characterized in that, The sealant storage tank (300) contains a sealant, which includes epoxy resin sealant, acrylic resin sealant, polyester resin sealant, phenolic resin sealant or amino resin sealant.

5. The high load-bearing sealing structure for the small orifice of an oil casing pipe according to claim 1, characterized in that, Both the female sealing surface (20) and the male sealing surface (31) are inverted conical surfaces, and the angle between the conical surface and the central axis is not less than 50 degrees.

6. The high load-bearing sealing structure for the small orifice of an oil casing pipe according to claim 1, characterized in that, The load-bearing sealing structure (3) is made of any one of titanium alloy, aluminum alloy or magnesium-aluminum alloy.

7. The high load-bearing sealing structure for the small orifice of an oil casing pipe according to claim 6, characterized in that, The titanium alloy materials include: Ti-2Al-(0.1~2.0)%Fe alloy, Ti-3Al-2.5V alloy, Ti-6Al-4V alloy, Ti-4Al-2.5V alloy, Ti-4Al-2.5V-(0.9~1.6)%Fe-(0.1~0.35)%O alloy, Ti-6Al-4V-(0.7~1.6)%Fe alloy, Ti-6Al-4V-(0.1~1.1)%Ni-(0.3~1.0)%Nb alloy, or Ti-5.5Al-4.5V-2Zr-1Mo alloy, all of which are mass percentages; The aluminum alloy material includes Al-Cu-Mg alloys, Al-Cu-Mg-Ag alloys, Al-Mg-Si alloys, or Al-Zn-Mg-Cu alloys. The magnesium-aluminum alloy materials include Mg-Al-Cu-Zn alloys, Mg-Al-Cu-Zr alloys, Mg-Al-Cu-Ni alloys, Mg-Al-Mn-Zr alloys, or Mg-Al-Ca-Mn-Cu-Ni alloys.

8. The high load-bearing sealing structure for the small orifice of an oil casing pipe according to claim 1, characterized in that, The threads on the sealing female threaded hole (21) and the sealing male threaded post (32) are cylindrical threads, tapered threads, variable pitch threads, or variable taper threads.

9. The high load-bearing sealing structure for the small orifice of an oil casing pipe according to claim 1, characterized in that, The cylindrical surface of the stud head (30) has a polygonal structure.

10. The application of the high load-bearing sealing structure for the small orifice of the oil casing as described in any one of claims 1 to 9, characterized in that, Used in well completion tools.

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