A sleeve connection structure

Abstract

The application discloses a casing connection structure, two adjacent pipe bodies are connected together by a coupling to form a casing, threads corresponding to the connection are arranged in the interior of the coupling and the exterior of the pipe body, the width of the thread groove is greater than the width of the thread tooth, the thread groove can reserve a certain axial movement space when the casing is subjected to axial deformation caused by high temperature, the thread groove absorbs the axial elongation force of the casing, avoids a large compression load, and causes deformation of the casing; when the temperature decreases, the casing is shortened in the axial direction, the thread tooth moves in the axial direction along the thread groove, the compression deformation of the thread is released again, the axial tensile load in the casing can be controlled within a certain range, and the casing will not be pulled off, the casing connection structure reserves a tensile space for deformation of the casing, avoids compression yield deformation of the casing caused by the influence of temperature, and improves the effectiveness of the casing.

Description

Technical Field

[0001] This invention belongs to the field of pipeline connection technology and relates to a sleeve connection structure. Background Technology

[0002] Currently, commonly used threaded fittings for sleeves, including API and non-API fittings, involve contact between the bearing surface and the guide surface after threading, or even if they do not contact, the gap between them is very small, preventing free expansion and contraction. The advantage of this type of threaded fitting is that it has relatively stable performance, and its tensile connection strength can be equal to or greater than that of the pipe body. Its compressive load resistance can also reach more than half or equal to that of the pipe body.

[0003] However, in heavy oil thermal recovery wells used for steam injection, the casing string is cemented. Each time steam injection and oil production occur, the casing string undergoes a heating (up to 50°C) and cooling (formation temperature) process, each cycle lasting approximately six months. Because the casing expands after each heating, and due to cementing outside the casing, the radial expansion is not fully released, instead converting into a certain proportion of axial elongation. This causes the overall elongation of the casing to exceed the yield strength of the casing material, resulting in an axial compressive load inside the casing exceeding the material's yield strength (especially at high temperatures where the yield strength decreases significantly; ordinary alloy steel can experience a reduction of over 25% at 300°C). Once cooling begins, the casing string gradually contracts, and theoretically should return to its original shape upon reaching the original temperature. However, due to the compressive yield deformation that occurred at high temperatures, residual compressive deformation remains inside the casing string upon cooling to the original low temperature, preventing recovery. Therefore, additional axial tensile loads begin to occur inside the casing string. After undergoing multiple steam injection and oil production cycles, the casing string is subjected to an additional initial axial tensile load. The actual axial tensile load borne by the casing string may exceed its actual tensile strength, leading to breakage and failure. Summary of the Invention

[0004] The purpose of this invention is to solve the problem in the prior art that when the sleeve deforms at high temperature, it undergoes compressive yield deformation, which cannot be recovered at low temperature. After repeated use, the axial tensile load actually borne by the sleeve may exceed the actual tensile strength, thus causing it to break and fail. The invention provides a sleeve connection structure.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A sleeve connection structure, characterized in that it includes a coupling for connecting two adjacent pipe bodies, the coupling being sleeved on the outside of the pipe body, the outer wall of the pipe body being provided with an external thread, and the inner wall of the coupling being provided with an internal thread corresponding to the external thread.

[0007] The width of the thread teeth and the width of the thread groove are the same for both the external and internal threads, and the width of the thread groove is greater than the width of the thread teeth for both the external and internal threads.

[0008] A further improvement of the present invention is that:

[0009] The external and internal threads have the same pitch;

[0010] The width of the thread teeth in both the external and internal threads is less than the length of the thread pitch.

[0011] The thread width of both the external and internal threads is 0.2-0.4 times the thread pitch.

[0012] The pitch length of both the external and internal threads is 12.7mm-50.8mm.

[0013] The difference between the thread groove and the thread tooth is greater than or equal to 0.5 times the preset movement of the sleeve to be constructed.

[0014] The tooth profile height of the internal thread is greater than that of the external thread.

[0015] It also includes an elastic seal, which is embedded in the inner wall of the coupling, and the two ends of the elastic seal abut against the ends of the adjacent pipe body.

[0016] The elastic seal includes an elastic body, and a spring is disposed inside the elastic body.

[0017] The length of the elastic seal is greater than the preset moving length of the sleeve to be constructed.

[0018] The pitch of the spring is greater than the diameter of the spring.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention discloses a sleeve connection structure. Two adjacent pipe bodies are connected together to form a sleeve via a coupling. Corresponding connecting threads are provided inside the coupling and outside the pipe bodies. The width of the thread groove is greater than the width of the thread teeth, ensuring that when the sleeve undergoes axial deformation at high temperatures, the thread groove can reserve a certain axial movement space, allowing the thread teeth to move along the thread groove. The thread groove absorbs the axial elongation force of the sleeve, avoiding excessive compressive load that could cause sleeve deformation. When the temperature decreases, the sleeve shortens axially. At this time, the thread teeth move axially in the opposite direction along the thread groove, releasing the compressive deformation absorbed by the thread again. This allows the axial tensile load within the sleeve to be controlled within a certain range, preventing breakage. The sleeve connection structure disclosed in this invention reserves tensile space for sleeve deformation, preventing compressive yielding deformation of the sleeve under temperature influence, and improving the effectiveness of the sleeve for multiple uses.

[0021] Furthermore, in this invention, the width of the thread teeth is less than the length of the thread pitch, ensuring that the thread teeth have sufficient space to move during deformation.

[0022] Furthermore, in this invention, the tooth profile height of the internal thread is greater than that of the external thread, ensuring that the damage caused by deformation during the deformation process is mainly on the external thread, which facilitates later observation and repair.

[0023] Furthermore, in this invention, an elastic sealing element is embedded inside the coupling, which not only improves the sealing performance of the pipe connection at both ends during installation, but also limits the axial installation of the pipe.

[0024] Furthermore, in this invention, the elastic seal includes a spring and an elastic body. The spring is inside the elastic body and plays a positioning role, preventing the elastic seal from shifting during deformation and ensuring the sealing performance of the pipe installation. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0027] Figure 2 For the present invention Figure 1 A magnified view of a portion of the image;

[0028] Figure 3 This is the internal thread structure of the present invention;

[0029] Figure 4 The external thread structure of the present invention

[0030] Figure 5 This is a schematic diagram of the elastic seal of the present invention;

[0031] Figure 6 This is a structural diagram of the sealing surface of the present invention;

[0032] Figure 7 This is a schematic diagram illustrating the displacement of a thread under axial compressive load in an embodiment of the present invention.

[0033] Figure 8 For the present invention Figure 7 A magnified view of a portion of the image.

[0034] Wherein: 1-coupling; 2-pipe body; 3-elastic seal; 4-spring; 5-elastic body; 6-tooth top; 7-tooth bottom. Detailed Implementation

[0035] 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 embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0036] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0037] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0038] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present 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, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0039] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0040] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0041] The present invention will now be described in further detail with reference to the accompanying drawings:

[0042] See Figures 1 to 2 This invention discloses a sleeve connection structure. At high temperatures, the sleeve column undergoes axial expansion and elongation. The significant axial elongation of the sleeve column is absorbed by the threaded joint, preventing large compressive loads within the sleeve column and thus avoiding compressive yield deformation. When the sleeve column temperature decreases, the sleeve shortens axially, and the compressive deformation absorbed by the threaded joint is released again. This allows the axial tensile load within the sleeve column to be controlled within a certain range, preventing breakage.

[0043] Specifically, it includes the following structure:

[0044] A sleeve connection structure includes a coupling 1 for connecting two adjacent pipe bodies 2. The coupling 1 is sleeved on the outside of the pipe body 2. The outer wall of the pipe body 2 is provided with an external thread, and the inner wall of the coupling 1 is provided with an internal thread corresponding to the external thread. The width of the thread teeth and the width of the thread groove of the external thread and the internal thread are the same, and the width of the thread groove of the external thread and the internal thread is greater than the width of the thread teeth.

[0045] Furthermore, in the embodiments of the present invention, see... Figures 3 to 4 The width T_wP and the width T_wB of the external thread teeth are both 0.2 to 0.4 times the pitch.

[0046] Specifically, this embodiment of the invention discloses a specific dimension, wherein the width of the thread teeth is approximately 2.54mm to 20.32mm, ensuring that the groove width wP of the external thread profile and the groove width wB of the internal thread profile are both greater than the tooth width T_wP of the external thread and the T_wB of the internal thread, and the difference dis (i.e., the maximum allowable movement disY) is not less than 0.5 times the design allowable movement of each sleeve. In this embodiment of the invention, the maximum allowable movement of the sleeve is determined based on the temperature difference of the sleeve circulation and the length of a single sleeve.

[0047] Furthermore, in this embodiment of the invention, the thread uses 0.5 to 2 threads per inch, that is, the pitch is 12.7 mm to 50.8 mm. The purpose of the large pitch is to leave enough distance for the axial movement of the joint.

[0048] In this embodiment of the invention, the specific length of the pitch can be determined based on the temperature difference of the cycle and the length of a single sleeve. For steel sleeves, the allowable movement of each sleeve can be estimated as (temperature difference × expansion coefficient × 1.3 - 0.0025) × 12000 mm.

[0049] Furthermore, in this embodiment of the invention, the complete thread length L4 of the external thread is less than or equal to 82mm, and the larger the external thread specification, the longer L4 is.

[0050] Furthermore, in this embodiment of the invention, the tooth tip 6 and tooth root 7 of the thread are both parallel to the axial direction of the sleeve, but the thread has a helix angle along the axial direction and is tapered as a whole, with a taper angle TaperD of 0.8 to 1.15.

[0051] Furthermore, in this embodiment of the invention, the tooth profile height of the internal thread is greater than that of the external thread, specifically:

[0052] The tooth height (THP) of the external thread teeth is less than or equal to 1.15 mm;

[0053] The tooth height THB of the internal thread is less than or equal to 1.25 mm.

[0054] Furthermore, in this embodiment of the invention, the chamfer of the thread is defined as follows:

[0055] The chamfer radius R1 of the internal thread is less than or equal to 0.2 mm, and R2 is between 0.4 and 0.6 mm;

[0056] The chamfer radius R3 of the external thread is less than or equal to 0.25 mm, and R4 is between 0.45 and 0.7 mm;

[0057] The larger the outer diameter of the casing, the larger the values ​​of R2 and R4 can be.

[0058] See Figure 5Furthermore, in this embodiment of the invention, an elastic sealing element 3 is also provided inside the coupling 1. The elastic sealing element is interference-fitted into the inside of the coupling 1, and the inner diameter of the elastic sealing element 3 is equal to the end of the external threaded pipe body 2.

[0059] Specifically, the elastic seal 3 includes an elastic body 5, with a spring 4 embedded inside the elastic body 5. The elastic body 5 is made of a high-temperature resistant and highly elastic resin, such as rubber. The spring 4 has a spring body diameter of not less than 2.5 mm, a pitch of 3 mm or more plus the spring body diameter, and a number of pitches of 8 or more. The elastic seal 3 ensures that after compressing the allowable movement of each sleeve, it can still return to its initial length.

[0060] Specifically, the thickness of the elastic seal 3 is greater than 3.5mm, and the length LS is greater than 20mm plus the allowable movement of each sleeve.

[0061] See Figure 6 Furthermore, in this embodiment of the invention, the sealing surface inside the coupling 1 at the connection between the pipe body 2 and the elastic seal 3 is an arc-shaped structure, ensuring that the sealing surface still has sufficient sealing effect even when the sleeve thread undergoes a large axial displacement. Under the action of the elastic seal 3, the sealing performance of the coupling 1 and the pipe body 2 is improved. Combined with the arc-shaped sealing surface here, the thread has a two-stage sealing structure.

[0062] Furthermore, in this embodiment of the invention, since the coupling 1 does not have a shoulder structure with ordinary special threads in the middle, but is an elastic seal 3 that can generate a large amount of compression, when the recommended torque setting is used, the shoulder torque of the upper buckle should not be less than 60% of the final upper buckle torque, and the inflection point of the shoulder torque can be seen on the number of turns-torque curve.

[0063] The present invention also discloses a specific example:

[0064] Applied to Φ244.48×8.94N80 bushing, maximum temperature 350℃, maximum temperature difference 320℃, steel bushing, expansion coefficient 0.000012, single bushing length calculated as 12m, maximum design movement of each bushing is 30mm.

[0065] The main design parameters are shown in Table 1. The integral calculation results of the sealing surface contact pressure line show that the sealing surface has high sealing reliability. After casing is run into the well and cemented, when the temperature rises to 200°C, the external thread of the special joint is pressed into the internal thread, the thread bearing surface separates, the thread guide surface gradually approaches, and dis gradually decreases. The external thread sealing cylinder continuously compresses the resin spring assembly. (See Table 1 for details.) Figures 7 to 8 .

[0066]

[0067]

[0068] The special threaded joint disclosed in this invention is suitable for sleeves operating under high-temperature and low-temperature cyclic conditions. Its axial tensile strength is no greater than 70% of the axial tensile yield strength of the pipe body, sufficient to suspend its own weight. The final axial compressive strength is no greater than 40% of the axial yield strength of the pipe body. The minimum yield strength of the material is no less than 552 MPa.

[0069] The sleeve connection structure disclosed in this invention, when used under high-temperature and low-temperature cyclic loading, can significantly reduce residual deformation and residual stress caused by temperature expansion and contraction within the sleeve, ensuring that the maximum stress inside the sleeve remains within the material's strength range, thereby preventing fracture. At high temperatures, the sleeve experiences axial expansion and elongation, while the joint experiences significant compression, resulting in compressive deformation. The substantial axial elongation of the sleeve is absorbed by the threaded joint, preventing large compressive loads within the sleeve and thus avoiding compressive yielding deformation. When the sleeve temperature decreases, the sleeve shortens axially, releasing the compressive deformation absorbed by the threaded joint. The sleeve lengthens, controlling the maximum axial tensile load within the sleeve within a certain range, ensuring that the maximum stress does not exceed the material's tensile strength, preventing breakage.

[0070] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A casing connection structure characterized by comprising: The utility model provides a connecting piece (1) for connecting two adjacent pipe bodies (2), the connecting piece (1) is sleeved on the outer side of the pipe body (2), the outer side wall of the pipe body (2) is provided with external thread, and the inner side wall of the connecting piece (1) is provided with internal thread corresponding to the external thread; The width of the thread tooth and the width of the thread groove of the external thread and the internal thread are the same, and the width of the thread groove of the external thread and the internal thread is greater than the width of the thread tooth; The difference between the thread groove and the thread tooth is greater than or equal to 0.5 times the preset movement amount of the casing to be formed; Further comprising an elastic sealing element (3) embedded on the inner wall of the connecting piece (1), and the two ends of the elastic sealing element (3) respectively abut against the end portions of the adjacent pipe bodies (2); The elastic sealing element (3) comprises an elastic body (5), and a spring (4) is arranged in the elastic body (5); The pitches of the external thread and the internal thread are the same; The width of the thread tooth of the external thread and the internal thread is less than the length of the pitch; The width of the thread tooth of the external thread and the internal thread is 0.2-0.4 times the length of the pitch; The tooth profile height of the thread tooth on the internal thread is greater than the tooth profile height of the thread tooth on the external thread; The pitch of the spring (4) is greater than the diameter of the spring (4).

2. A casing connection as defined in claim 1, wherein The length of the pitch of the external thread and the internal thread is 12.7mm-50.8mm.

3. A casing connection as defined in claim 1, wherein The length of the elastic sealing element (3) is greater than the preset movement length of the casing to be formed.

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