A back sub for cementing

Abstract

The present application belongs to the field of oil well cementing tools, and particularly relates to a back-connection plug for well cementing, which comprises a centralizing connector, a connecting cylinder, a centralizing assembly and a guide head, wherein the centralizing assembly comprises a centralizing cylinder and a centralizer. In the process of being lowered into the back-connection cylinder along with the back-connection casing to complete the butt joint, the back-connection plug can always maintain the central position relative to the back-connection cylinder under the action of the centralizing connector and the centralizer, so that the accurate butt joint of the back-connection plug and the back-connection cylinder is realized conveniently and quickly, and the back-connection plug has wide applicability in the field of well cementing. In addition, the guide head can be automatically detached after the back-connection process is completed, so that the subsequent drilling process is avoided, and the work efficiency is improved. Moreover, the back-connection plug also has good sealing performance due to the arrangement of the sealing part and other components.

Description

Technical Field

[0001] This invention belongs to the field of oil cementing tools, specifically relating to a reconnector for cementing. Background Technology

[0002] In the cementing field, tailpipe reconnection technology refers to the technique of running a reconnection casing from the wellhead into the well and connecting it to the tailpipe reconnection sleeve via a reconnection plug. In existing tailpipe reconnection technology, the reconnection plug is first run through the reconnection casing to the position of the tailpipe reconnection sleeve, but not yet inserted. Cement grout is then injected into the annulus, and the reconnection plug is then inserted into the tailpipe reconnection sleeve to achieve a seal and allow it to set. However, in this technical solution, to ensure a smooth and accurate connection between the reconnection plug and the reconnection sleeve, a cement grouting process is required, which is relatively cumbersome. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention aims to provide a return plug for cementing, comprising: a centralizing connector having a cylindrical first body and a first limiting step disposed outside the first body; a connecting cylinder including a second body partially sleeved inside the first body; a centralizing assembly including a centralizing cylinder having a third body and a centralizer sleeved outside the third body, the third body being partially sleeved inside the second body; and a guide head, partially sleeved inside the third body, for guiding the return plug for cementing into the return cylinder along with the return casing, wherein the return plug for cementing is centered relative to the return cylinder during insertion via the centralizing connector and the centralizer.

[0004] As a further extension of the above technical solution, the present invention also provides the following embodiments:

[0005] The straightener includes a middle part with an outwardly convex arc-shaped axial cross section, and an upper working part and a lower working part respectively connected to the upper and lower ends of the middle part, wherein the straightener is fixedly connected to the third main body through the lower working part.

[0006] The straightening cylinder includes a first pin hole on the side wall of the third main body, and a second pin hole corresponding to the first pin hole is provided on the side wall of the fourth main body of the guide head. In the initial state, a separating pin is provided in the first pin hole and the second pin hole to connect the guide head to the third main body.

[0007] The transition pin portion is disposed within the first pin hole, partially protruding beyond the third body and located inside the middle portion, and the transition pin is configured to push the separation pin radially under the action of the middle portion to completely disengage from the first pin hole.

[0008] The separating pin is a smooth cylinder and is disposed in the first pin hole and the second pin hole in an interference fit manner. The transition pin is also a cylinder, including a threaded surface and a smooth working surface. The threaded surface is used to form an engagement with the internal thread in the first pin hole.

[0009] The straightener includes a rubber layer disposed on the outermost side.

[0010] The first limiting step includes a cylindrical surface and a first inclined surface below the cylindrical surface. The diameter of the cylindrical surface is the same as the inner diameter of the outer sleeve, which is used to ensure that the upper end of the reconnector is straightened. The first inclined surface corresponds to the inclined surface inside the end face of the reconnector tube, so that the first limiting step can limit the movement of the reconnector.

[0011] The guide head includes a second inclined surface that slopes downwards from the outside to the inside in the radial direction at the lower end, and a first circulation hole and a second circulation hole that are connected in order from top to bottom inside the guide head, wherein the inner diameter of the first circulation hole is larger than the inner diameter of the second circulation hole.

[0012] It includes a sealing portion fitted onto the outside of the second body and the third body.

[0013] A second limiting step is provided on the outside of the second main body, and a third limiting step is provided on the outside of the third main body. The sealing parts are respectively provided between the lower end face of the straightening joint or the lower end face of the connecting cylinder and the second limiting step, and between the lower end face of the connecting cylinder and the third limiting step.

[0014] The sealing part includes a plurality of sealing elements, each of which includes a ring body and through grooves disposed at the upper and lower ends of the ring body, and a rubber ring is disposed in the through groove.

[0015] A sealing groove for placing the sealing ring is provided on the inner side of the ring body.

[0016] The advantages of this invention compared to existing technologies are as follows: First, under the action of the centralizing connector and the centralizer, the reconnection plug can maintain a centered position relative to the reconnection sleeve, thereby improving reconnection accuracy and success rate in a simple way. It also has a centralizing effect on outer casings of different wall thicknesses, making it widely applicable in cementing. Second, after the reconnection plug is inserted into the reconnection sleeve, the guide head can automatically detach without drilling, shortening the workflow and improving work efficiency. Third, thanks to the design of the sealing part and the rubber layer distributed on the outermost side of the centralizer, the reconnection plug, after connecting to the reconnection sleeve, has excellent sealing performance. Furthermore, the reconnection plug has a simple overall structure, uses widely available materials, is easy to process and manufacture, and has good economic advantages and prospects for industrial production. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the back-insertion joint for cementing according to the present invention;

[0018] Figure 2 A schematic diagram of the structure of the straightening joint;

[0019] Figure 3 This is a schematic diagram of the connecting cylinder.

[0020] Figure 4 This is a schematic diagram of the uprighting cylinder.

[0021] Figure 5 This is a schematic diagram of the centralizer.

[0022] Figure 6 A schematic diagram of the guide head structure;

[0023] Figure 7 This is a schematic diagram of the structure of the separating pin;

[0024] Figure 8 This is a structural diagram of the transition pin;

[0025] Figure 9 This is a schematic diagram of the sealing element.

[0026] In this application, all the accompanying drawings are schematic diagrams for illustrating the structure and principle, and are not drawn according to actual dimensions and scale.

[0027] The meanings of the labels in the figures are as follows:

[0028] 1. Straightening connector; 11. First body; 12. First limiting step; 121. Cylindrical surface; 122. First inclined surface; 13. First internal thread; 14. Second internal thread; 15. First threaded through hole; 16. Second screw; 2. Connecting cylinder; 21. Second body; 22. Second limiting step; 23. First external thread; 24. Third internal thread; 25. First blind hole; 26. Second threaded through hole; 27. Third screw; 28. Fourth screw; 3. Straightening assembly; 31. Straightening cylinder; 311. Third body; 312. First pin hole; 313. Third limiting step; 314. Third threaded through hole; 315. Second external thread; 316. Second blind hole; 317. Stepped surface 32. Centralizer; 321. Middle section; 322. Upper working section; 323. Lower working section; 324. Rubber layer; 325. Through hole; 326. First screw; 4. Guide head; 41. Fourth body; 42. Second pin hole; 43. Second inclined surface; 44. First circulation hole; 441. First rounded corner; 45. Second circulation hole; 451. Second rounded corner; 5. Separating pin; 51. First chamfer; 6. Transition pin; 61. Threaded surface; 62. Working surface; 63. Second chamfer; 7. Sealing part; 71. Sealing element; 711. Ring body; 712. Through groove; 713. Rubber ring; 714. Sealing ring; 715. Sealing groove; 100. Reconnection plug for cementing. Detailed Implementation

[0029] The embodiments of the present invention will now be described in more detail with reference to the accompanying drawings.

[0030] Figure 1 This is a schematic diagram of the reconnection plug 100 for cementing according to the present invention (hereinafter referred to as "reconnection plug 100"). As shown in the figure, the reconnection plug 100 includes a centering connector 1, a connecting cylinder 2, a centering assembly 3, and a guide head 4.

[0031] like Figures 1 to 5 As shown, the straightening connector 1 has a cylindrical first body 11 and a first limiting step 12 disposed on the outside of the first body 11. A connecting cylinder 2 is disposed below the straightening connector 1 and is connected to the straightening connector 1 via a second body 21 partially fitted inside the first body 11. A straightening assembly 3 is connected below the connecting cylinder 2. The straightening assembly 3 includes a straightening cylinder 31 and a straightener 32. The straightening cylinder 31 includes a third body 311, which is partially fitted inside the second body 21, serving to connect the straightening assembly 3 to the connecting cylinder 2. The straightener 32 is fitted outside the third body 311. A guide head 4, used to guide the return plug 100 as it is lowered into the return cylinder (not shown) along with the return sleeve (the same below), is partially fitted inside the third body 311.

[0032] In actual operation, after the reconnection plug 100 is connected to the reconnection casing, it extends into the outer casing (not shown, the same below) that has been pre-installed in the well and performs the reconnection operation. The reconnection plug 100 maintains its upper end in a centered position relative to the outer casing through the centralizing connector 1, and its lower end in a centered position relative to the outer casing through the centralizer 32. The outer casing and the reconnection tube are centered, so the reconnection plug 100 is also centered relative to the reconnection tube. In this way, the reconnection plug 100 maintains a centered posture throughout its downward movement and gradual connection with the reconnection tube. When the first limiting step 12 on the centralizing connector 1 is completely aligned with the upper surface of the reconnection tube, the reconnection plug 100 completes the connection operation with the reconnection tube.

[0033] like Figure 1 and Figure 5 As shown, in one embodiment of the present invention, the centralizer 32 includes a central portion 321 with an outwardly convex arcuate cross-section, and an upper working portion 322 and a lower working portion 323 respectively connected to the upper and lower ends of the central portion 321. Preferably, the upper working portion 322 and the lower working portion 323 are cylindrical. The centralizer 32 is fixedly connected to the third body 311 through the lower working portion 323, while the upper working portion 322 is in a free state. With this arrangement, when the reconnector 100 contacts the outer sleeve, its lower end can remain centered relative to the outer sleeve under the support of the arcuate central portion 321. Furthermore, during the process of the reconnector 100 moving downward and completing the connection with the reconnector cylinder, the central portion 321 will gradually be compressed and undergo elastic deformation. Since the upper working part 322 is in a free state, the middle part 321 and the upper working part 322 will move upward along the third body 311 until the reconnection plug 100 completes the connection with the reconnection cylinder, and the straightener 32 and the third body 311 are fully in contact, at which point the movement stops. During this reconnection process, since the middle part 321 is always in a compressed state, the middle part 321 always has a straightening effect on the reconnection plug 100, maintaining the lower end of the reconnection plug 100 in a centered position relative to the reconnection cylinder when the reconnection operation is completed.

[0034] Furthermore, the axial arc-shaped cross-section of the intermediate portion 321 is symmetrical. This design facilitates the processing of the centralizer 32 and makes the force on the intermediate portion 321 more uniform during the compression process, which helps to improve the service life of the intermediate portion 321. Preferably, the axial arc-shaped cross-section of the intermediate portion 321 is set as a semi-circle.

[0035] Furthermore, the stabilizer 32 includes a rubber layer 324 disposed on its outermost side to ensure that the reconnection plug 100 can fit tightly with the reconnection tube when inserted into the reconnection tube, and to form a good seal between the reconnection plug 100 and the reconnection tube.

[0036] Furthermore, the thickness of the centralizer 32 is equal to the difference between the inner diameter of the return sleeve and the outer diameter of the third body 311. This design ensures a good seal between the centralizer 32 and the return sleeve after the return sleeve is inserted.

[0037] Furthermore, a plurality of through holes 325 distributed circumferentially are provided on the side wall of the lower working part 323, and a plurality of third threaded through holes 314 are provided on the side wall of the third body 311 at positions corresponding to the through holes 325. The centralizer 32 is fixedly connected to the third body 311 by screwing the first screw 326 into the through holes 325 and the third threaded through holes 314. Preferably, the number of both through holes 325 and third threaded through holes 314 is four.

[0038] Furthermore, in order to ensure the straightening effect of the straightener 32 on the reconnection plug 100, the straightener 32 is preferably made of highly elastic spring steel.

[0039] like Figure 1 , Figure 4 and Figure 6 As shown, in one embodiment of the present invention, a first pin hole 312 is provided on the side wall of the third body 311, and a second pin hole 42 corresponding to the first pin hole 312 is provided on the side wall of the fourth body 41 of the guide head 4. In the initial state, the separating pin 5 is disposed within the first pin hole 312 and the second pin hole 42 to connect the guide head 4 to the third body 311. With this arrangement, the guide head 4 is detachably installed on the straightening cylinder 31, which is simple, convenient, and easy to replace.

[0040] Furthermore, there are two of each of the first pin hole 312 and the second pin hole 42. Preferably, the first pin hole 312 and the second pin hole 42 are evenly distributed along the circumference.

[0041] Furthermore, a transition pin 6 is installed within the first pin hole 312. The transition pin 6 is partially located within the first pin hole 312 and partially extends beyond the third body 311, situated inside the intermediate portion 321. Thus, the transition pin 6, under the pressure of elastic deformation of the intermediate portion 321, can push the separation pin 5 radially, completely detaching it from the first pin hole 312. In this situation, a connection is no longer formed between the guide head 4 and the third body 311 of the centering assembly 3, allowing the guide head 4 to separate from the third body 311 under its own weight and fall to the bottom of the well. This design enables the guide head 4 to detach automatically after entering the return plug 100, eliminating the need for drilling operations after the return plug 100 is in place and improving production efficiency.

[0042] Furthermore, in a preferred embodiment of the present invention, the length of the transition pin 6 is set to be equal to the hole depth of the first pin hole 312, and the separating pin 5 is initially in contact with the transition pin 6 at one end and flush with the inner surface of the guide head 4 at the other end. This arrangement can also achieve the above-mentioned technical effects of facilitating the self-disengagement of the guide head 4, reducing drilling operations after the reconnector plug 100 is in place, and improving production efficiency.

[0043] Furthermore, in another preferred embodiment of the present invention, the positions of the first pin hole 312 and the second pin hole 42 are configured not to correspond to the largest protruding portion of the intermediate portion 321. This design is based on the following considerations: on the one hand, during the process of the intermediate portion 321 moving towards the third body 311 and completing the fitting, the largest protruding portion of its part requires the greatest pressure, meaning that this part is least likely to fully fit with the third body 311; on the other hand, during the insertion of the reconnector plug 100, the rubber layer 324 on the outer side of the largest protruding portion of the intermediate portion 321 is most prone to wear. If wear occurs, the intermediate portion 321 may not fully fit with the third body 311 after the movement is completed. Both of these situations may result in the transition pin 6 not being fully pressed into the third body 311, which may in turn affect the complete disengagement of the separating pin 5 from the third body 311, ultimately affecting the automatic detachment of the guide head 4. By setting the first pin hole 312 and the second pin hole 42 at positions that do not correspond to the maximum protrusion of the middle part 321, the above situation can be avoided, ensuring the realization of the automatic detachment function of the guide head 4.

[0044] Furthermore, in one embodiment of the present invention, the separating pin 5 is a smooth-surfaced cylinder and is placed within the first pin hole 312 and the second pin hole 42 with an interference fit. The transition pin 6 is also a cylinder, but includes a threaded surface 61 and a smooth working surface 62. The threaded surface 61 serves to engage with the internal thread (not shown, the same below) inside the first pin hole 312. In specific operation, the straightening cylinder 31 is first combined with the guide head 4, and the separating pin 5 is hammered into the first pin hole 312 and the second pin hole 42 by tapping. Then, the threaded surface 61 of the transition pin 6 is screwed into the first pin hole 312 and engages with the separating pin. During the insertion of the reconnector 100, when the force on the transition pin 6 reaches a certain level, the threaded surface 61 breaks the internal thread in the first pin hole 312. Under the action of external force, the transition pin 6 moves radially inward, pushing the separating pin 5 completely away from the first pin hole 312, causing the guide head 4 to automatically detach. This design ensures the stability of the installation of the separating pin 5 and the transition pin 6, preventing premature movement of the separating pin 5 and the transition pin 6 due to shaking or unexpected pressure during the insertion of the reconnector 100, which could lead to premature detachment of the guide head 4 and subsequent loss of its function.

[0045] Furthermore, in a preferred embodiment of the present invention, a first chamfer 51 is provided at both the upper and lower ends of the separating pin 5, and a second chamfer 63 is provided at both the upper and lower ends of the transition pin 6. The first chamfer 51 and the second chamfer 63 prevent workers from being injured by the sharp edges of the separating pin 5 and the transition pin 6 during installation. They also prevent unnecessary collisions between the separating pin 5 and the transition pin 6 and other components during installation, reducing the possibility of damage to the reconnector 100.

[0046] Furthermore, in one embodiment of the invention, both the separating shear pin 5 and the transition shear pin 6 are made of copper.

[0047] like Figure 1 and Figure 2As shown, in one embodiment of the present invention, the first limiting step 12 includes a cylindrical surface 121 and a first inclined surface 122 located below the cylindrical surface 121. The diameter of the cylindrical surface 121 is the same as the diameter of the outer sleeve, which is used to ensure that the upper end of the reconnector plug 100 is aligned when it mates with the outer sleeve and when it moves downwards for reconnection. The first inclined surface 122 corresponds to the inclined surface inside the end face of the reconnector tube. By setting the first inclined surface 122, the first limiting step 12 has a limiting effect on the movement of the reconnector plug 100. Preferably, the inclination angle of the first inclined surface 122 is consistent with the inclination angle of the inclined surface inside the end face of the reconnector tube, so that the first inclined surface 122 can fit tightly against the end face of the reconnector tube when it plays a limiting role, so as to maintain the stability of the limiting state of the first limiting step 12.

[0048] like Figure 1 and Figure 6 As shown, in one embodiment of the present invention, the guide head 4 includes a second inclined surface 43, a first circulation hole 44, and a second circulation hole 45. The second inclined surface 43 is disposed at the lower end of the fourth body 41 and slopes downward from the outside to the inside in the radial direction. This design avoids the situation where the guide head 4 cannot enter the reconnection tube due to the lack of a certain movement trajectory restriction during the process of the reconnection plug 100 being lowered into the reconnection tube with the reconnection sleeve, resulting in a collision or misalignment between the surfaces of the guide head 4 and the reconnection tube, thus ensuring the accuracy of the reconnection process. The setting of the first circulation hole 44 and the second circulation hole 45 avoids the situation where the guide head 4 detaches and blocks the wellbore, thus not obstructing the flow of fluid in the well during subsequent production. In addition, the inner diameter of the first circulation hole 44 is set to be larger than the inner diameter of the second circulation hole 45. This design reduces the volume of unnecessary parts in the guide head 4, thereby reducing the weight of the guide head 4 and making the reconnection plug 100 lighter.

[0049] Furthermore, a first rounded corner 441 is provided at the lower end of the first circulation hole 44, and a second rounded corner 451 is provided at the lowermost end of the second circulation hole 45. This design enhances the strength of the internal connections and boundaries of the guide head 4, reduces the presence of sharp edges on the guide head 4, and helps improve the safety of the guide head 4 during use.

[0050] Furthermore, for the sake of weight reduction and ease of drilling, the guide head 4 is made of plastic.

[0051] like Figure 1 As shown, in one embodiment of the present invention, a sealing portion 7 is sleeved on the outer side of the second body 21 and the third body 311. The sealing portion 7 ensures a good seal between the reconnection plug 100 and the reconnection cylinder after they are connected, preventing leakage during subsequent production processes.

[0052] Furthermore, such as Figure 1 , Figure 3 , Figure 4 and Figure 9 As shown, in one embodiment of the present invention, a second limiting step 22 is provided on the outer side of the second main body 21, and a third limiting step 313 is provided on the outer side of the third main body 311. Sealing portions 7 are provided between the lower end face of the straightening connector 1 and the second limiting step 22, and between the lower end face of the connecting cylinder 2 and the third limiting step 313. Furthermore, when the reconnector 100 includes multiple sequentially connected connecting cylinders 2, a sealing portion 7 is also provided between the lower end face of the previous connecting cylinder 2 and the second limiting step 22 in the next connecting cylinder 2. Through this design, the range of motion of the sealing portion 7 is limited by the limiting steps and the end faces of each component, preventing large-scale movement of the sealing portion 7 when the reconnector 100 is lowered into the reconnector cylinder, thereby improving the sealing effect.

[0053] Furthermore, in one embodiment of the present invention, the sealing portion 7 covers the area between the lower end face of the straightening connector 1 or the lower end face of the connecting cylinder 2 and the second limiting step 22, and between the lower end face of the connecting cylinder 2 and the third limiting step 313. This design increases the sealing range of the sealing portion 7 and ensures that the sealing portion 7 is fixed between the limiting step and the end faces of each component, preventing any movement when the reconnector plug 100 is lowered into the reconnector cylinder. Both of these aspects contribute to improving the sealing performance of the sealing assembly 7.

[0054] Furthermore, in one embodiment of the present invention, the sealing part 7 includes a plurality of sealing elements 71. Each sealing element 71 includes a ring body 711 and a through groove 712 disposed on the ring body 711, and a rubber ring 713 is disposed in the through groove 712. This arrangement facilitates the replacement and installation of the sealing part 7. In addition, using a plurality of rubber rings 713 disposed in the through groove 712 for sealing is more economical than arranging rubber rings 713 on the entire circumference, while still meeting the sealing requirements, as it saves materials and improves the smoothness of the insertion process of the reconnector 100.

[0055] Furthermore, to enhance sealing, grooves 712 for placing rubber rings 713 are provided at both the upper and lower ends of the ring body 711.

[0056] Furthermore, in one embodiment of the present invention, a sealing groove 715 for placing the sealing ring 714 is provided on the inner side of the ring body 711. Preferably, the sealing groove 715 is located at the middle position on the inner side of the ring body 711. This design is for the purpose of improving the sealing performance between the sealing member 71 and the second body 21 and the third body 311, as well as for ease of processing.

[0057] Furthermore, in one embodiment of the present invention, the reconnector 100 includes two second bodies 21 and one third body 311. Three sealing elements 71 are respectively fitted onto the outer sides of the two second bodies 21 and the third body 311, meaning the reconnector 100 includes nine sealing elements 71. This design achieves the aforementioned technical effects related to the sealing elements 71, which will not be elaborated further here.

[0058] like Figures 1 to 4 As shown, in one embodiment of the present invention, a first internal thread 13 is provided on the inner side of the upper end of the first body 11 for connecting the straightening connector 1 to the return sleeve, thereby connecting the return plug 100 to the return sleeve. A second internal thread 14 is provided on the inner side of the lower end of the first body 11, and a first external thread 23 is provided on the outer side of the upper end of the second body 21 for matching with the second internal thread 14 to connect the connecting cylinder 2 to the lower end of the straightening connector 1. A third internal thread 24 is provided on the inner side of the lower end of the second body 21, and a second external thread 315 is provided on the outer side of the upper end of the straightening cylinder 31. The third internal thread 24 can form a matching relationship with both the first external thread 23 and the second external thread 315. Through this design, the straightening cylinder 31 can be connected to the lower part of the connecting cylinder 2 through the second external thread 315. At the same time, according to production needs, another connecting cylinder 2 can be installed below one connecting cylinder 2 by combining the first external thread 23 and the third internal thread 24, so that the return plug 100 has sufficient length.

[0059] Furthermore, in a preferred embodiment of the present invention, the reconnection plug 100 includes two sequentially connected connecting tubes 2.

[0060] Furthermore, in another embodiment of the present invention, a first threaded through hole 15 is provided at the lower end of the first body 11, and a first blind hole 25 is provided at a corresponding position on the side wall at the upper end of the second body 21. During installation, the connection between the straightening connector 1 and the connecting cylinder 2 is strengthened by screwing a second screw 16 into the first threaded through hole 15 and abutting against the first blind hole 25. A second threaded through hole 26 is provided at the lower end of the second body 21, and a second blind hole 316 is provided at a corresponding position on the side wall at the upper end of the straightening cylinder 31. During installation, the connection between the connecting cylinder 2 and the straightening cylinder 31 is strengthened by screwing a third screw 27 into the second threaded through hole 26 and abutting against the second blind hole 316. In addition, when there is more than one connecting cylinder 2, the second threaded through hole 26 on the previous connecting cylinder 2 can correspond to the first blind hole 25 on the next connecting cylinder 2. Thus, during actual installation, the connection between different connecting cylinders 2 can be strengthened by screwing the fourth screw 28 into the second threaded through hole 26 and abutting it in the first blind hole 25.

[0061] Furthermore, the first blind hole 25 penetrates the first external thread 23, and the second blind hole 316 penetrates the second external thread 315. This design allows for a compact arrangement of the connection points between different components, which helps to improve the strength of the reconnector 100 and the robustness of the connection between components.

[0062] like Figure 4 As shown, in one embodiment of the present invention, a stepped surface 317 is provided on the inner side of the lower end of the straightening cylinder 31. This design reduces the contact area between the guide head 4 and the straightening cylinder 31, thereby reducing the frictional resistance encountered by the guide head 4 during the automatic detachment process, so that the guide head 4 can smoothly complete the automatic detachment process.

[0063] Furthermore, in order to maintain the stability of the guide head 4 installation, the first step surface 317 is provided below the first pin hole 312 and the second pin hole 42.

[0064] According to the reconnector 100 of the present invention, during the docking process when the reconnecting casing is lowered into the reconnecting sleeve, the centering connector 1 and the centralizer 32 maintain a centered position relative to the reconnecting sleeve. This allows for precise docking of the reconnector 100 and the reconnecting sleeve without additional operations, making it simple and convenient. Furthermore, it provides a centering effect for outer casings of varying wall thicknesses, making it widely applicable in cementing applications. Additionally, after the reconnector 100 is inserted into the reconnecting sleeve, the guide head 4 automatically detaches, avoiding drilling operations and improving work efficiency. Secondly, the reconnector 100 has a sealing part 7, and the outermost side of the centralizer 32 is also provided with a rubber layer 324. Both provide a good sealing effect at the connection between the reconnector 100 and the reconnecting sleeve, improving the safety and reliability of the reconnector 100. Finally, the reconnector 100 has a simple overall structure, uses widely available materials, is easy to process and manufacture, and has good economic efficiency and industrial production prospects.

[0065] In this application, the specific meanings of directional terms such as "up," "down," "inside," and "outside" are as follows: Figure 1 The drawing state of the middle reconnector plug 100 is for reference.

[0066] Finally, it should be noted that although the present invention has been described in detail with reference to preferred embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, the technical features mentioned in the various embodiments can be combined in any way, provided there is no structural conflict. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A return plug (100) for cementing, comprising: The straightening connector (1) has a cylindrical first body (11) and a first limiting step (12) disposed on the outside of the first body (11). The connecting tube (2) includes a second body (21) partially fitted inside the first body (11); The straightening assembly (3) includes a straightening cylinder (31) having a third body (311) and a straightener (32) sleeved on the outside of the third body (311), wherein the third body (311) is partially sleeved inside the second body (21); and The guide head (4), which is partially fitted inside the third body (311), is used to guide the return plug (100) for cementing into the return sleeve along with the return casing. The centralizer (32) includes a middle part (321) with an outwardly convex arc-shaped axial cross section, and an upper working part (322) and a lower working part (323) respectively connected to the upper and lower ends of the middle part (321). The centralizer (32) is fixedly connected to the third body (311) through the lower working part (323). The straightening cylinder (31) includes a first pin hole (312) provided on the side wall of the third body (311), and a second pin hole (42) corresponding to the first pin hole (312) is provided on the side wall of the fourth body (41) of the guide head (4). In the initial state, a separating pin (5) is provided in the first pin hole (312) and the second pin hole (42) to connect the guide head (4) to the third body (311). The transition pin (6) is partially disposed within the first pin hole (312), and partially extends beyond the third body (311) and is located inside the middle part (321). The transition pin (6) is configured to push the separation pin (5) radially out of the first pin hole (312) under the squeezing action of the middle part (321) after elastic deformation. The first limiting step (12) includes a cylindrical surface (121) and a first inclined surface (122) below the cylindrical surface (121). The diameter of the cylindrical surface (121) is the same as the inner diameter of the outer sleeve, which is used to ensure that the upper end of the reconnector (100) is straightened. The first inclined surface (122) corresponds to the inclined surface inside the end face of the reconnector tube, so that the first limiting step (12) can limit the movement of the reconnector (100). The return plug (100) for cementing is able to remain centered relative to the return tube during insertion via the centralizing connector (1) and the centralizer (32).

2. The reconnection plug (100) for cementing according to claim 1, characterized in that: The separating pin (5) is a smooth cylinder and is disposed in the first pin hole (312) and the second pin hole (42) with an interference fit. The transition pin (6) is a cylinder, including a threaded surface (61) and a smooth working surface (62). The threaded surface (61) is used to form a connection with the internal thread in the first pin hole (312).

3. The reconnection plug (100) for cementing according to claim 2, characterized in that: The stabilizer (32) includes a rubber layer (324) disposed on the outermost side.

4. The reconnection plug (100) for cementing according to claim 3, characterized in that: The guide head (4) includes a second inclined surface (43) that slopes downward from the outside to the inside in the radial direction at the lower end, and a first circulation hole (44) and a second circulation hole (45) that are connected in the order from top to bottom inside the guide head (4), wherein the inner diameter of the first circulation hole (44) is larger than the inner diameter of the second circulation hole (45).

5. The reconnection plug (100) for cementing according to any one of claims 1 to 4, characterized in that: It includes a sealing part (7) fitted on the outside of the second body (21) and the third body (311).

6. The reconnection plug (100) for cementing according to claim 5, characterized in that: A second limiting step (22) is provided on the outside of the second main body (21), and a third limiting step (313) is provided on the outside of the third main body (311). The sealing part (7) is respectively provided between the lower end face of the straightening joint (1) or the lower end face of the connecting cylinder (2) and the second limiting step (22), and between the lower end face of the connecting cylinder (2) and the third limiting step (313).

7. The reconnection plug (100) for cementing according to claim 6, characterized in that: The sealing part (7) includes a plurality of sealing elements (71), each of the sealing elements (71) includes a ring body (711) and a through groove (712) provided at the upper and lower ends of the ring body (711), and a rubber ring (713) is provided in the through groove (712).

8. The reconnection plug (100) for cementing according to claim 7, characterized in that: A sealing groove (715) for placing a sealing ring (714) is provided on the inner side of the ring body (711).

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