A completion string

Abstract

The utility model belongs to the drilling lining integrated well completion technical field, specifically relates to a well completion pipe column. Well completion pipe column includes: the liner; The back -connection plug of coaxial setting is above the liner; The first oil pipe of coaxial setting above the back -connection plug through detachable mode, the second oil pipe of setting above the first oil pipe through the back-off device. In normal sidetracking, the first oil pipe is separated from the back -connection plug, the pipe column above the back -connection plug is drawn from the well, then the sidetracking tool is lowered to the open hole section and is sidetracked, if the first oil pipe and the back -connection plug cannot be normally separated, then the second oil pipe can be separated from the first oil pipe through the back-off device, then the back -off device and the first oil pipe are drilled, and the sidetracking tool is lowered to the open hole section and is sidetracked.

Description

Technical Field

[0001] This utility model belongs to the field of drilling-lining integrated well completion technology, specifically, it relates to a well completion string. Background Technology

[0002] In the drill-liner integrated drilling and completion process, to meet the requirements of later open-hole sidetracking, a liner is usually first run to support the open-hole section. There is an axial gap between the upper end of the liner and the upper end of the open-hole section. Then, the lower end of the upper tubing string (small-diameter tubing) is inserted back into the liner to form a continuous tubing working channel. When sidetracking is required in the open-hole section, the upper tubing string is separated from the liner, pulled out of the well, and the open-hole section is exposed. Then, sidetracking tools are run to perform sidetracking in the open-hole section.

[0003] In actual operation, the above process has many technical problems: the use of small-sized tubing for back-insertion makes it impossible to determine whether it has been back-inserted in place and the circulation channel is not sealed, which affects the normal construction of coiled tubing; if the well wall of the open hole section becomes unstable and collapses, it may even bury the connection between the upper tubing string and the liner, making it impossible to pull the upper tubing string out of the well, which increases the difficulty of handling, and the original tubing string structure is difficult to take into account both open hole support and reserved side-drilling windows.

[0004] Therefore, it is necessary to optimize the tubing structure and docking tools to achieve single-tube docking operations, solve the problems of difficult tubing adjustment and difficult re-insertion in traditional processes, and meet the support requirements of open-hole mudstone penetration sections and subsequent side-drilling requirements. Utility Model Content

[0005] In view of the technical problems mentioned above, the present invention aims to provide a well completion string.

[0006] According to this utility model, a well completion string is provided, comprising: Liner; A reconnection plug is coaxially positioned above the liner. The first oil pipe is detachably and coaxially mounted above the reconnection plug; A second oil pipe is installed above the first oil pipe via a release mechanism.

[0007] In one specific embodiment, the liner, the reconnection plug, and the first oil pipe are located in the bare eye section, and the connection point between the second oil pipe and the release device is not lower than the upper end face of the bare eye section.

[0008] In one specific embodiment, the reconnection plug includes a body and a connector coaxially disposed at the lower end of the body for connecting to a downhole tool below, wherein the first tubing is coaxially disposed within the body via a shear pin.

[0009] In one specific embodiment, the main body includes a reconnection tube disposed at the lower end, and the connector includes a connecting cylinder coaxially fixed to the outside of the reconnection tube and a pawl coaxially disposed below the connecting cylinder, with a gap between the inner wall of the pawl and the outer wall of the connecting cylinder.

[0010] In one specific embodiment, a protrusion is provided at the lower end of the reconnection cannula, the protrusion being located below the pawl, and there is an axial gap between the protrusion and the pawl.

[0011] In one specific embodiment, a groove is provided on the outer wall of the reconnection cannula, and the pawl is located outside the groove.

[0012] In one specific embodiment, the main body includes a release section coaxially disposed above the reconnection tube, and the first oil pipe is coaxially disposed within the release section via a shear pin.

[0013] In one specific embodiment, a limiting step is provided on the inner wall of the release section for axially abutting the lower end of the first oil pipe.

[0014] In one specific embodiment, when the first oil pipe is fixedly connected to the release section by a shear pin, there is an axial gap between the lower end of the first oil pipe and the limiting step.

[0015] In one specific embodiment, the main body includes a reconnecting sleeve coaxially disposed above the release section, the reconnecting sleeve being constructed with an inner diameter that gradually increases from bottom to top, and the first oil pipe being capable of being repeatedly inserted into the reconnecting sleeve.

[0016] Compared with the prior art, the advantages of this application are as follows.

[0017] The first tubing of this invention is connected to the second tubing via a release device at the top, and to the liner via a reconnection plug at the bottom. During well completion, the tubing string formed by the connection of the second tubing, release device, first tubing, and reconnection plug is lowered into the well and connected to the liner to form a circulation channel. The pressure of the lowered tubing string indicates whether it has been properly reconnected, and the airtightness of the circulation channel is ensured. During normal sidetracking, the first tubing is separated from the reconnection plug, and the tubing string above the reconnection plug is pulled out of the well. Then, sidetracking tools are lowered to perform sidetracking on the open hole section. If sidetracking is required and the first tubing cannot be properly separated from the reconnection plug, the second tubing can be released from the first tubing via a release device. After the release device and the first tubing are drilled out, sidetracking tools are lowered to perform sidetracking on the open hole section.

[0018] This utility model optimizes the pipe column structure and achieves the simultaneous completion of open hole section support and upper pipe column re-insertion through an integrated drilling and lining design, realizing integrated operation of open hole support, re-insertion docking and side drilling pre-reservation.

[0019] The reconnection plug of this invention connects to the upper end of the liner via a ratchet pawl, facilitating reconnection. The reconnection plug connects to the first oil pipe via a shear pin, enabling easy disconnection of both. Attached Figure Description

[0020] The present invention will now be described with reference to the accompanying drawings.

[0021] Figure 1 This is a schematic diagram of one embodiment of the well completion string according to the present invention; Figure 2 This is a schematic diagram of one embodiment of the reconnection plug according to the present invention; Figure 2a and Figure 2b This is a schematic diagram of an embodiment of the connection between the reconnector and the connector according to the present invention; Figures 3 to 9 This is a schematic diagram illustrating the workflow of running the completion string and side-drilling the completion string according to the present invention. Figures 10 to 13 This is a schematic diagram of the working process of the reconnection plug according to this utility model.

[0022] Figure label: 1. Liner; 2. Connector; 3. Reconnector plug; 4. First oil pipe; 5. Release device; 6. Packer; 7. Second oil pipe; 21. Card slot; 22. Abutment part; 31. Main body; 311. Reconnecting tube; 312. Release section; 313. Reconnecting sleeve; 314. Protrusion; 315. Groove; 316. Limiting step; 32. Connecting part; 321. Connecting sleeve; 322. Pawl; 33. Shear pin; 100. Completion string; 101. Open hole section; 102. Casing section.

[0023] In this application, all the accompanying drawings are schematic drawings, used only to illustrate the principle of the present invention, and are not drawn to scale. Detailed Implementation

[0024] The present invention will now be described with reference to the accompanying drawings.

[0025] It should be noted that in this application, the direction of the well completion string near the wellhead after it is inserted into the well is described as "up", "forward" or similar terms, while the direction of the well string away from the wellhead after it is inserted into the well is described as "down", "back" or similar terms.

[0026] Figure 1 The structure of the well completion string 100 according to this utility model is shown. For example... Figure 1 As shown, the completion string 100 includes a liner 1, a reconnection plug 3, a first tubing 4, a release device 5, and a second tubing 7.

[0027] In this embodiment, the wellbore includes an open hole section 101 and a casing section 102 coaxially disposed above the open hole section 101. A liner 1 is disposed within the open hole section 101, and there is an axial gap between the upper end face of the liner 1 and the upper end face of the open hole section 101 to allow space for subsequent side-drilling. A reconnection plug 3 is coaxially connected to the upper end of the liner 1, a first tubing 4 is detachably coaxially connected to the upper end of the reconnection plug 3, and a second tubing 7 is coaxially connected to the upper end of the first tubing 4 via a release device 5.

[0028] like Figures 3 to 9 The completion process of the completion string 100 is shown, as well as the workflow for sidetracking the completion string 100.

[0029] The completion process for a 100mm completion string is as follows. For example... Figure 3 As shown, the liner 1 is first lowered into the well, with its upper end face positioned below the upper end face of the open hole section 101, leaving space for subsequent sidetracking. It should be noted that in this embodiment, a connector 2 is provided at the upper end of the liner 1. The connector 2 is a part of the release assembly left after the drilling string above the liner 1 is released following the completion of drilling in the drill-liner integrated drilling process. The drill-liner integrated drilling process is well known to those skilled in the art and will not be described in detail here. Figure 4 As shown, the reconnector 3 is then assembled to the lower end of the first tubing 4 at the wellhead. Figure 5 As shown, the upper end of the first tubing 4 is then connected to the release device 5 at the wellhead. Figure 6 As shown, the upper end of the release device 5 is then connected to the second oil pipe 7, and a packer 6 is installed on the outer wall of the second oil pipe 7. Figure 7 As shown, the reconnection plug 3 is finally reconnected to the connector 2 at the upper end of the liner 1 by lowering the second oil pipe 7.

[0030] When side-drilling is required, in one embodiment provided by this utility model, such as Figure 8 As shown, by releasing the first tubing 4 and the return connector 3, the entire tubing string above the return connector 3 is pulled out of the well, exposing the open hole section 101, which facilitates the subsequent running of side-drilling tools from the wellhead into the well for side-drilling of the open hole section 101.

[0031] In another embodiment provided according to the present invention, such as Figure 9As shown, when the wellbore of open hole section 101 becomes unstable and collapses, burying the connection between the first tubing 4 and the return plug 3, making it impossible for the return plug 3 to separate from the first tubing 4, the first tubing 4 and the second tubing 7 can be released using the release device 5. The entire tubing string above the release device 5 can be pulled out of the well, and then the drill bit can be run down to remove the release device 5 and the first tubing 4 left in the well, exposing open hole section 101. This facilitates the subsequent running of sidetracking tools from the wellhead into the well for sidetracking of open hole section 101.

[0032] The structures of the dropper 5 and the packer 6 are well known to those skilled in the art and will not be described in detail here.

[0033] According to this utility model, such as Figure 2 As shown, the reconnector 3 includes a main body 31 and a connector 32 coaxially disposed at the lower end of the main body 31 for connecting to a downhole tool below. In this embodiment, the downhole tool connected to the lower end of the main body 31 is a connector 2 at the upper end of the liner 1, and the connector 32 is used to coaxially fix the main body 31 and the connector 2. The upper end of the main body 31 is used to connect to the first tubing 4, and the first tubing 4 is coaxially fixed inside the main body 31 by shear pins 33.

[0034] In this embodiment, the main body 31 includes a reconnection tube 313, a release section 312, and a reconnection insertion tube 311, which are coaxially and fixedly connected from top to bottom.

[0035] The connector 32 is coaxially fixed on the outside of the reconnection tube 311. Specifically, the connector 32 includes a connecting cylinder 321 and a pawl 322. The connecting cylinder 321 is coaxially fixed on the outside of the reconnection tube 311, and the pawl 322 is coaxially located at the lower end of the connecting cylinder 321. There is a gap between the inner wall of the pawl 322 and the outer wall of the connecting cylinder 321, allowing the pawl 322 to retract radially inward under external force. The diameter of the inner wall of the connector 2 is smaller than the outer diameter of the pawl 322 when no external force is applied. A groove 21 for fitting and connecting with the pawl 322 is provided on the inner wall of the connector 2. During the process of inserting the reconnection plug 3 into the connector 2 from top to bottom, the pawl 322 retracts radially under the squeezing action of the inner wall of the connector 2. When the pawl 322 reaches the position of the groove 21, the pawl 322 expands radially under its own elastic force and thus engages with the groove 21. At this time, the reconnection plug 3 and the connector 2 are reconnected.

[0036] In one specific embodiment, a protrusion 314 is provided at the lower end of the reconnection cannula 311. The protrusion 314 is located below the pawl 322, and there is an axial gap between the protrusion 314 and the pawl 322. An abutment portion 22 for fitting the protrusion 314 is provided on the inner wall of the connector 2. The abutment portion 22 is located below the slot 21, and its inner diameter is smaller than that of the protrusion 314. During the process of inserting the reconnection plug 3 into the connector 2 from top to bottom, the pawl 322 contracts radially under the squeezing action of the inner wall of the connector 2, thus entering the interior of the connector 2. When the pawl 322 reaches the position of the slot 21, it expands radially under its own elastic force, thus locking into the slot 21. At this time, the reconnection plug 3 and the connector 2 are reconnected. Simultaneously, as... Figure 10 As shown, the protrusion 314 at the lower end of the reconnection tube 311 axially abuts against the abutment portion 22 on the inner wall of the connector 2. By providing the protrusion 314 and the abutment portion 22, the insertion of the reconnection plug 3 into the connector 2 can be detected by applying pressure from the wellhead to the completion string 100. In this embodiment, a pressure of two tons is applied from the wellhead to the completion string 100. If the completion string 100 no longer moves downward, it indicates that the reconnection plug 3 has been inserted into the connector 2. Then, by lifting the completion string 100 from the wellhead, it is detected whether the pawl 322 of the reconnection plug 3 has connected with the slot 21 of the connector 2. It should be noted that when detecting the connection between the reconnection plug 3 and the connector 2 by applying pressure from the wellhead to the completion string 100 or by lifting it, the applied tonnage should be controlled within the strength range of the shear pin 33 to avoid shearing the shear pin 33.

[0037] In this embodiment, as Figure 2a and Figure 2b As shown, the pawl 322 is axially movable on the outside of the reconnection tube 311. The upper and lower ends of the pawl 322 are respectively limited by the connecting cylinder 321 and the protrusion 314. That is, the axial distance between the connecting cylinder 321 and the protrusion 314 is greater than the axial length of the pawl 322, and the pawl 322 can move within the axial range between the connecting cylinder 321 and the protrusion 314.

[0038] A groove 315 is provided on the outer wall of the reconnection cannula 311. There is an axial gap between the lower end of the groove 315 and the upper end of the protrusion 314.

[0039] During the insertion of the reconnector 3 into the connector 2, the outer diameter of the pawl 322 is larger than the inner diameter of the upper part of the connector 2. Therefore, the connector 2 applies an upward thrust to the pawl 322, causing the upper end of the pawl 322 to axially abut against the connector tube 321. At this time, the lower end of the pawl 322 is located in the groove 315. Under the pressure of the inner wall of the connector 2, the pawl 322 can radially retract into the groove 315, thereby allowing the entire reconnector 3 to be inserted into the connector 2. When the protrusion 314 of the reconnection tube 311 axially abuts against the abutment portion 22 of the inner wall of the connector 2, the pawl 322 engages with the slot 21 of the connector 2. When the reconnector 3 is lifted, the pawl 322 remains stationary under the engagement of the slot 21. The reconnector tube 311 moves upward relative to the pawl 322, causing the lower end of the pawl 322 to axially abut against the protrusion 314 at the lower end of the reconnector tube 311. Furthermore, the groove 315 on the outer wall of the reconnector tube 311 moves upward relative to the pawl 322. At this point, the lower end of the pawl 322 is no longer within the groove 315. The inner and outer sides of the pawl 322 abut against the outer wall of the reconnector tube 311 and the inner wall of the connector 2, respectively. This prevents the pawl 322 from retracting radially and from disengaging from the slot 21, thus preventing the reconnector 3 from separating from the connector 2. Figure 2b As shown.

[0040] In this embodiment, an internal thread is provided on the inner wall of the lower end of the release section 312, and an external thread is provided on the outer wall of the upper end of the reconnection tube 311. The release section 312 is coaxially fixedly connected to the upper part of the reconnection tube 311 by means of threaded connection. The first oil pipe 4 is coaxially disposed inside the release section 312, and the first oil pipe 4 and the release section 312 are fixedly connected by a shear pin 33.

[0041] After the pawl 322 of the reconnector 3 is connected to the slot 21 of the connector 2, the shear pin 33 is cut off by applying pressure from the wellhead to the completion string 100. Figure 11 As shown, this separates the first oil pipe 4 from the release section 312 of the reconnection plug 3. Figure 12 As shown, at this time, the first tubing 4 and the tubing string above it can be moved up or down to adjust the position of the wellhead tubing string, which facilitates the installation of the wellhead equipment.

[0042] In this embodiment, a limiting step 316 is provided on the inner wall of the release section 312. The inner diameter of the limiting step 316 is smaller than the outer diameter of the first oil pipe 4, and it is used to axially abut against the first oil pipe 4. The limiting step 316 is located below the first oil pipe 4. When the first oil pipe 4 is fixedly connected to the release section 312 by the shear pin 33, there is an axial gap between the lower end face of the first oil pipe 4 and the limiting step 316, thereby providing space for the subsequent vertical movement of the first oil pipe 4 to adjust the tubing.

[0043] In this embodiment, the reconnection sleeve 313 is coaxially fixed above the release section 312. The reconnection sleeve 313 is constructed with an inner diameter that gradually increases from bottom to top, serving as a guide for the insertion of the first oil pipe 4, allowing the first oil pipe 4 to be repeatedly inserted into the reconnection sleeve 313. Figure 13 As shown, after adjusting the position of the wellhead tubing string, the first tubing 4 can be re-inserted into the release sub 312 under the guidance of the reconnection sleeve 313.

[0044] According to this utility model, a method for constructing a well completion string is also provided, including the following steps.

[0045] First, the liner 1 is lowered into the well, with its upper end face positioned below the upper end face of the open hole section 101, leaving space for subsequent side-drilling. Figure 3 As shown. It should be noted that in this embodiment, a connector 2 is provided at the upper end of the liner 1. The connector 2 is a part of the release component left after the drilling string above the liner 1 is released after drilling is completed in the drill-liner integrated drilling process. The drill-liner integrated drilling process is well known to those skilled in the art and will not be described in detail here.

[0046] like Figure 4 As shown, the reconnector 3 is then assembled at the wellhead to the lower end of the first tubing 4.

[0047] like Figure 5 As shown, the upper end of the first tubing 4 is then connected to the release device 5 at the wellhead.

[0048] like Figure 6 As shown, the upper end of the release device 5 is then connected to the second oil pipe 7, and a packer 6 is provided on the outer wall of the second oil pipe 7.

[0049] like Figure 7 As shown, the reconnection plug 3 is reconnected to the connector 2 at the upper end of the liner 1 via the second oil pipe 7 below. Figure 10 As shown, at this time, the pawl 322 of the reconnector plug 3 is connected to the slot 21 of the connector 2.

[0050] Then, apply a two-ton downforce to the completion string 100. If the completion string 100 no longer moves down, it indicates that the reconnector 3 has been inserted into the connector 2. Next, check whether the pawl 322 of the reconnector 3 is engaged with the slot 21 of the connector 2 by lifting the completion string 100 from the wellhead. If the first tubing 4 and the tubing above it do not move upward or move upward a very small distance (the distance from when the pawl 322 abuts against the upper connecting sleeve 313 to when it abuts against the lower protrusion 314) and then stop, it indicates that the pawl 322 of the reconnector 3 is engaged with the slot 21 of the connector 2. It should be noted that when checking the connection between the reconnector 3 and the connector 2 by applying pressure or lifting the completion string 100 from the wellhead, the applied tonnage should be controlled within the strength range of the shear pin 33 to avoid shearing the shear pin 33.

[0051] like Figure 11 As shown, by applying pressure from the wellhead to the completion string 100, the first tubing 4 moves downward relative to the release section 312, shearing the shear pin 33 and separating the first tubing 4 from the release section 312 of the reconnection plug 3. Figure 12 As shown, at this time, the first tubing 4, the release device 5, and the second tubing 7 can be moved up or down to adjust the position of the wellhead string, facilitating the installation of the wellhead equipment. The process of adjusting the position of the wellhead string is as follows: The second tubing 7 is composed of multiple short tubings connected in series. When the reconnector 3 has been inserted into the connector 2 and connected to each other, if the upper end of the second tubing 7 exceeds the specified height of the wellhead, the second tubing 7 is lifted, and the uppermost short tubing of the second tubing 7 is replaced with a shorter tubing, so that after the first tubing 4 is reconnected to the reconnector 313 and the release device 312, the uppermost end of the second tubing 7 can be located at the specified height of the wellhead. The process of replacing the uppermost short tubing of the second tubing 7 when adjusting the position of the wellhead string is well known to those skilled in the art and will not be described in detail here.

[0052] like Figure 13 As shown, the first tubing 4 and the tubing string above it are lowered, so that the first tubing 4 is reconnected to the reconnection plug 3 through the reconnection sleeve 313, and the packer 6 is set, thus completing the well completion work.

[0053] When sidetracking is required or well workover is needed in the upper section, such as Figure 8 As shown, the packer 6 is unsealed, and then the well casing string 100 is pulled up directly from the wellhead position to separate the reconnector 3 from the first tubing 4. The casing string above the reconnector 3 is pulled out of the well, thereby exposing the open hole section 101. Then, the side-drilling tool is run down to side-drill the open hole section 101.

[0054] In another embodiment provided according to the present invention, such as Figure 9As shown, when sidetracking is required or well workover is needed in the upper part, and the connection between the reconnector 3 and the first tubing 4 cannot be separated, the first tubing 4 and the second tubing 7 are separated by the release device 5, the tubing string above the release device 5 is pulled out of the well, and then the release device 5 and the first tubing 4 are drilled out, and the sidetracking tool is lowered to perform sidetracking on the open hole section 101.

[0055] In the description of this utility model, it should be understood that 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 indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0056] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., 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 this utility model according to the specific circumstances.

[0057] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present 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.

[0058] Finally, it should be noted that the above description is merely a preferred embodiment of this utility model and does not constitute any limitation on this utility model. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A well completion string, characterized in that, include: Liner (1); A reconnection plug (3) is coaxially disposed above the liner (1); The first oil pipe (4) is detachably and coaxially mounted above the reconnection plug (3); A second oil pipe (7) is installed above the first oil pipe (4) via a release device (5).

2. The completion string according to claim 1, characterized in that, The liner (1), the reconnection plug (3) and the first oil pipe (4) are located in the bare section (101), and the connection between the second oil pipe (7) and the release device (5) is not lower than the upper end face of the bare section (101).

3. The completion string according to claim 1, characterized in that, The reconnection plug (3) includes a main body (31) and a connector (32) coaxially disposed at the lower end of the main body (31) for connecting to the downhole tool below. The first tubing (4) is coaxially disposed in the main body (31) by a shear pin (33).

4. The completion string according to claim 3, characterized in that, The main body (31) includes a reconnection tube (311) disposed at the lower end, and the connector (32) includes a connecting cylinder (321) coaxially fixedly disposed on the outside of the reconnection tube (311) and a pawl (322) coaxially disposed below the connecting cylinder (321). There is a gap between the inner wall of the pawl (322) and the outer wall of the connecting cylinder (321).

5. The completion string according to claim 4, characterized in that, A protrusion (314) is provided at the lower end of the reconnection cannula (311), the protrusion (314) is located below the pawl (322), and there is an axial gap between the protrusion (314) and the pawl (322).

6. The completion string according to claim 5, characterized in that, A groove (315) is provided on the outer wall of the reconnection tube (311), and the pawl (322) is located outside the groove (315).

7. The completion string according to claim 4, characterized in that, The main body (31) includes a release section (312) coaxially disposed above the reconnection tube (311), and the first oil pipe (4) is coaxially disposed inside the release section (312) by a shear pin (33).

8. The completion string according to claim 7, characterized in that, The inner wall of the release section (312) is provided with a limiting step (316) for axially abutting the lower end of the first oil pipe (4).

9. The completion string according to claim 8, characterized in that, When the first oil pipe (4) is fixedly connected to the release section (312) by the shear pin (33), there is an axial gap between the lower end of the first oil pipe (4) and the limiting step (316).

10. The completion string according to claim 7, characterized in that, The main body (31) includes a reconnector (313) coaxially disposed above the release section (312), the reconnector (313) being constructed with an inner diameter that gradually increases from bottom to top, and the first oil pipe (4) being able to be repeatedly inserted into the reconnector (313).

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