Multi-stage branch completion device

Abstract

The present invention provides a multi-stage branch completion device, comprising: a downhole positioning structure; a main wellbore hollow core whipstock, arranged on the downhole positioning structure, the main wellbore hollow core whipstock comprises an inner sleeve and an outer sleeve, the inner sleeve is arranged in the outer sleeve, a first opening is arranged on the side wall of the outer sleeve, and at least a portion of the inner sleeve is located at the first opening; a positioning suspension structure, arranged on the main wellbore hollow core whipstock, the positioning suspension structure comprises a cylindrical body and an inner liner, the inner liner is arranged in the cylindrical body, a second opening is arranged on the cylindrical body, the second opening is arranged opposite to the first opening, and at least a portion of the inner liner is located at the second opening; wherein the inner liner is made of a soluble metal material. The technical solution provided by the present invention can solve the technical problem of complex operation of the multi-stage branch completion device in the prior art.

Description

Technical Field

[0001] The present invention relates to the field of drilling equipment and tools in the petroleum industry, and in particular to a multi-stage branch completion device. Background Art

[0002] At present, multi-branch wells are wells that are drilled at different depths in a main wellbore to exploit oil layers at different depths. This technology can increase the oil drainage area, increase oil well production, and comprehensively reduce the cost of reservoir development. Branch well technology is generally considered to be one of the cutting-edge technologies with broad development prospects that uses drilling technology to increase oil and gas well recovery rates, turn difficult-to-use reserves into usable reserves, and further improve the economic benefits of oil and gas wells.

[0003] Among them, the connection between the main wellbore and the branch wellbore has mechanical integrity, and the hydraulic seal is mainly sealed by the cement ring. This means that there is mechanical support provided by the casing and cementing cement at the connection between the main wellbore and the branch wellbore, and the branch wells of this level can fully enter the main wellbore and the branch wellbore in any well repair operation. How to ensure the mechanical connectivity, hydraulic integrity and selective re-entry of the branch well branch part is the main technical problem restricting the development and application of domestic branch well technology. The key to branch well technology is completion, and reliable downhole system tools are the key to successful completion. The quality of cement cementing at the pre-opening window of the branch casing of the existing pre-opening window downhole system of the domestic downhole branch system is greatly affected by the pre-opening window. If the pre-opening window is open during cementing, the cementing cement will enter the branch wellbore through the pre-opening window, and the cement ring will not be formed at the pre-opening window and above, and the cementing quality is poor.

[0004] There are two existing solutions. One is to place a section of steel liner inside the pre-opening window of the branch casing, and pre-block the pre-opening window of the branch casing during cementing. The cementing cement cannot enter the branch wellbore through the pre-opening window, but returns to the upper part of the branch casing as in normal cementing. After cementing is completed, the steel liner placed inside the branch casing is removed. Although this method improves the cementing quality, it requires an extra trip of the drill string to remove the steel liner. The main wellbore is connected by grinding the cement in the core of the hollow whipstock tool of the main wellbore and the aluminum bottom plug in the downhole permanent positioning tool through the next trip of grinding shoes. The other is to run casing into the branch wellbore. After the branch wellbore is cemented normally, the branch casing, the cement in the core of the hollow whipstock tool of the main wellbore and the aluminum bottom plug in the downhole permanent positioning tool are ground through by the next trip of special grinding and milling tools. This method has good cementing quality, but it is very difficult to grind through the branch wellbore casing with an angle of no more than 3 degrees with the main wellbore downhole. Summary of the invention

[0005] The main purpose of the present invention is to provide a multi-stage branch completion device to solve the technical problem of complex operation of the multi-stage branch completion device in the prior art.

[0006] In order to achieve the above-mentioned objectives, the present invention provides a multi-stage branch completion device, comprising: a downhole positioning structure; a main wellbore hollow core bender, which is arranged on the downhole positioning structure, the main wellbore hollow core bender comprising an inner sleeve and an outer sleeve, the inner sleeve is arranged in the outer sleeve, a first opening is arranged on the side wall of the outer sleeve, and at least a portion of the inner sleeve is located at the first opening; a positioning suspension structure, which is arranged on the main wellbore hollow core bender, the positioning suspension structure comprises a cylindrical body and an inner liner, the inner liner is arranged in the cylindrical body, a second opening is arranged on the cylindrical body, the second opening is arranged opposite to the first opening, and at least a portion of the inner liner is located at the second opening; wherein the inner liner is made of a soluble metal material.

[0007] Furthermore, the multi-stage branch completion device also includes a connecting piece, which passes through the inner liner pipe and is connected to the cylindrical body.

[0008] Furthermore, the connecting piece is a connecting screw, a connecting through hole is provided on the inner liner pipe, a threaded hole is provided on the cylindrical body, and the connecting screw passes through the connecting through hole and is threadedly connected with the threaded hole.

[0009] Further, the connecting screw is made of a soluble material.

[0010] Furthermore, the downhole positioning structure comprises a first casing, a first clamping structure is arranged on the first casing, and a second clamping structure matched with the first clamping structure is arranged on the inner sleeve.

[0011] Further, the first clamping structure is a first positioning hole, the second clamping structure is a first clamping protrusion, and the first clamping protrusion is clamped in the first positioning hole so that the outer sleeve is arranged on the first sleeve.

[0012] Furthermore, a first annular positioning surface is provided at the end of the first sleeve, and a second annular positioning surface matched with the first annular positioning surface is provided on the inner sleeve, and the first annular positioning surface is used for fitting and positioning with the second annular positioning surface.

[0013] Furthermore, a third clamping structure is arranged on the outer sleeve, and a fourth clamping structure matched with the third clamping structure is arranged on the cylindrical body.

[0014] Furthermore, the third clamping structure is a clamping groove, the second clamping structure is a second clamping protrusion, and the second clamping protrusion is clamped in the clamping groove so that the outer sleeve is arranged on the cylindrical body.

[0015] Furthermore, the inner sleeve has an annular guiding bevel, which is located at the end of the inner sleeve, so that the cylindrical body can pass through the first opening under the guidance of the annular guiding bevel.

[0016] Furthermore, the multi-stage branch completion device also includes: a second casing, which is arranged at one end of the downhole positioning structure away from the hollow core whipstock of the main wellbore.

[0017] By applying the technical solution of the present invention, since the liner is made of soluble metal material, after cementing is completed, there is no need to remove the liner of soluble metal, and the liner of soluble metal only needs to be directly dissolved by drilling fluid, and then the milling tool is lowered to connect the main wellbore and the branch wellbore. Therefore, the technical solution provided by the present invention can solve the technical problem of complex operation of the multi-stage branch completion device in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0019] Figure 1 It shows a schematic diagram of the assembly structure of a multi-stage branch completion device provided in an embodiment of the present invention;

[0020] Figure 2 A schematic diagram of the structure of a downhole positioning structure in a well according to an embodiment of the present invention is shown;

[0021] Figure 3 It shows a schematic structural diagram of a main wellbore hollow core whipstock provided according to an embodiment of the present invention;

[0022] Figure 4 A schematic structural diagram of a positioning suspension structure provided according to an embodiment of the present invention is shown;

[0023] Figure 5 It shows a schematic diagram of the installation structure of the soluble metal lined pipe in the positioning suspension structure provided in an embodiment of the present invention;

[0024] Figure 6 Shows Figure 5 A magnified view of the local structure at the circle in the figure;

[0025] Figure 7 A schematic diagram of the structure of branch well cementing provided according to an embodiment of the present invention is shown;

[0026] Figure 8 A schematic diagram showing a grinding shoe grinding through cement and aluminum bottom plugging to connect to a main wellbore after cementing provided by an embodiment of the present invention is shown.

[0027] The above drawings include the following reference numerals:

[0028] 10. Downhole positioning structure; 11. First casing; 111. First clamping structure; 112. First annular positioning surface; 113. Neck section; 114. Aluminum bottom plug; 12. Sealing element; 20. Hollow core whipstock; 21. Inner sleeve; 211. Annular guide slope; 22. Outer sleeve; 221. First opening; 222. Second clamping structure; 223. Third clamping structure; 224. Second annular positioning surface; 225. The third annular positioning surface; 23, the first lowering release handle; 24, the plug; 30, the positioning suspension structure; 31, the cylindrical body; 311, the fourth clamping structure; 312, the fourth annular positioning surface; 32, the inner liner; 321, the second opening; 322, the casing connecting thread; 33, the second lowering release handle; 40, the connecting piece; 50, the second casing; 60, the grinding shoe; 70, the cementing pipe string; 81, the branch wellbore casing; 82, the working pipe string. DETAILED DESCRIPTION

[0029] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0030] like Figures 1 to 8As shown, an embodiment of the present invention provides a multi-level branch completion device. Specifically, the multi-level branch completion device in this embodiment is mainly a 4-level branch completion tool. The 4-level branch is a branch well in which both the main wellbore and the branch wellbore can be cemented. The multi-level branch completion device includes a downhole positioning structure 10 (the downhole positioning structure 10 can also be called a downhole permanent positioning tool), a main wellbore hollow core bevel 20 and a positioning suspension structure 30 (the positioning suspension structure 30 can also be called a branch wellbore pre-window positioning suspension tool). The downhole positioning structure 10 can be permanently fixed and sleeved in the main casing downhole. The main wellbore hollow-core bend tool 20 is arranged on the downhole positioning structure 10. The main wellbore hollow-core bend tool 20 is located above the downhole positioning structure 10. The main wellbore hollow-core bend tool 20 includes an inner sleeve 21 and an outer sleeve 22. The inner sleeve 21 is arranged in the outer sleeve 22. The lower end of the inner sleeve 21 is inserted into the upper end of the downhole positioning structure 10. The upper end of the inner sleeve 21 is inserted into the outer sleeve 22. A first opening 221 is provided on the side wall of the outer sleeve 22. At least part of the inner sleeve 21 is located at the first opening 221. The positioning suspension structure 30 is arranged on the hollow core whipstock 20 of the main wellbore. The positioning suspension structure 30 can be bent. The positioning suspension structure 30 includes a cylindrical body 31 and an inner liner 32. The inner liner 32 is arranged in the cylindrical body 31. The cylindrical body 31 is provided with a second opening 321. The second opening 321 is arranged opposite to the first opening 221. At least part of the inner liner 32 is located at the second opening 321. The inner liner 32 can be fixed at the second opening 321 by expansion, clamping, connection with a connector 40, etc., so as to block the first opening 221 and the second opening 321 through the inner liner 32. The inner liner 32 is made of a soluble metal material.

[0031] By using the multi-stage branch completion device provided in this embodiment, after cementing is completed, there is no need to remove the soluble metal liner 32. It is only necessary to use the drilling fluid to directly dissolve the soluble metal liner 32, and then lower the milling tool to communicate the main wellbore and the branch wellbore, and then lower the milling tool to communicate the main wellbore and the branch wellbore, so as to improve the operation efficiency and reliability. When the soluble metal liner 32 is not completely dissolved, the next grinding shoe 60 can also be used to grind through the soluble metal liner 32 first. Since the metal hardness of the soluble metal liner 32 is relatively low, it is very easy to grind through. Then grind through the cement in the inner core of the main wellbore hollow bevel 20 tool and the aluminum bottom plug 114 in the downhole permanent positioning tool. Therefore, the multi-stage branch completion device provided in this embodiment can solve the technical problem of complex operation of the multi-stage branch completion device in the prior art.

[0032] In order to improve the setting stability of the liner pipe 32, the soluble metal liner pipe 32 can be directly expanded in the cylindrical body 31, and the soluble metal liner pipe 32 can be located at the second opening 321; or, the multi-stage branch completion device in this embodiment can also include a connector 40, which passes through the liner pipe 32 and is connected to the cylindrical body 31.

[0033] Specifically, the connecting member 40 is a connecting screw, and a connecting through hole may be provided on the inner liner tube 32, and a threaded hole may be provided on the cylindrical body 31, and the connecting screw passes through the connecting through hole and is threadedly connected with the threaded hole. With such a setting, the inner liner tube 32 and the cylindrical body 31 can be stably connected together, and the setting stability of the inner liner tube 32 is better improved.

[0034] In this embodiment, the connecting screws are made of a soluble material, which makes it easy to separate the liner pipe 32 from the cylindrical body 31 after cementing is completed.

[0035] Specifically, the downhole positioning structure 10 in this embodiment includes a first casing 11, a first clamping structure 111 is provided on the first casing 11, and a second clamping structure 222 adapted to the first clamping structure 111 is provided on the inner sleeve 21. With such a structural arrangement, it is convenient to connect the first casing 11 and the inner sleeve 21, so that the main wellbore hollow core whipstock 20 is stably arranged on the downhole positioning structure 10.

[0036] Specifically, the first clamping structure 111 in this embodiment is a clamping hole, and the second clamping structure 222 is a first clamping protrusion, which is clamped in the clamping hole so that the outer sleeve 22 is arranged on the first sleeve 11. With such a clamping structure, the clamping is convenient and stable, and it is easy for the staff to operate.

[0037] In this embodiment, the end of the first sleeve 11 is provided with a first annular positioning surface 112, and the inner sleeve 21 is provided with a second annular positioning surface 224 adapted to the first annular positioning surface 112, and the first annular positioning surface 112 is used to fit and position with the second annular positioning surface 224. Such a structural setting can facilitate the improvement of the setting stability of the first sleeve 11 and the outer sleeve 22, avoid the positional displacement of the first sleeve 11 and the inner sleeve 21 during use, and improve the stability of the overall structure. Specifically, in this embodiment, the upper end of the first sleeve 11 is provided with the first annular positioning surface 112 along the axial direction, and the lower outer portion of the inner sleeve 21 is provided with the second annular positioning surface 224 along the axial direction. Both the first annular positioning surface 112 and the second annular positioning surface 224 are inclined structures. During installation, the lower end of the inner sleeve 21 of the main wellbore hollow core whipstock 20 tool is inserted into the upper end of the downhole permanent positioning tool, and the inner sleeve 21 and the downhole permanent positioning tool are connected and fixed by an elastic pin (the first clamping protrusion can be an elastic pin).

[0038] Specifically, the outer sleeve 22 in this embodiment is provided with a third clamping structure 223, and the cylindrical body 31 is provided with a fourth clamping structure 311 adapted to the third clamping structure 223. With such a structural arrangement, the outer sleeve 22 and the cylindrical body 31 can be easily connected, so that the main wellbore hollow core whipstock 20 is stably connected to the positioning suspension structure 30.

[0039] Specifically, the third clamping structure 223 in this embodiment is a clamping groove, and the second clamping structure 222 is a second clamping protrusion, which is clamped in the clamping groove so that the outer sleeve 22 is set on the cylindrical body 31. Specifically, the clamping groove in this embodiment can be an open groove, and the second clamping protrusion slides into the opening of the open groove so that the second clamping protrusion is clamped into the clamping groove to improve the stability of the clamping. With such a clamping structure, the clamping is convenient and stable, which is convenient for the staff to operate.

[0040] In this embodiment, the upper end of the outer sleeve 22 is provided with a third annular positioning surface 225 along the circumferential direction, and the end of the cylindrical body 31 is provided with a fourth annular positioning surface 312 adapted to the third annular positioning surface 225, and the third annular positioning surface 225 is used to fit and position with the fourth annular positioning surface 312. With such a structural setting, it is easy to improve the setting stability of the outer sleeve 22 and the cylindrical body 31, avoid the position displacement of the outer sleeve 22 and the cylindrical body 31 during use, and improve the stability of the overall structure. Specifically, the third annular positioning surface 225 and the fourth annular positioning surface 312 can both be inclined structures.

[0041] Specifically, the second opening 321 in this embodiment is arranged on the side wall of the cylindrical body 31 , and the lower end of the second opening 321 is lower than the lower end of the annular guide slope 211 , so that the liner tube 32 at the second opening 321 can extend from the first opening 221 .

[0042] In this embodiment, the inner sleeve 21 has an annular guiding bevel 211, and the annular guiding bevel 211 is located at the end of the inner sleeve 21, so that the cylindrical body 31 passes through the first opening 221 under the guidance of the annular guiding bevel 211. With such a structural arrangement, it is possible to avoid that the cylindrical body 31 is completely inserted into the outer sleeve 22 during the installation process, so that a portion of the cylindrical body 31 is bent and extends out of the first opening 221. Specifically, the annular guiding bevel 211 is located at the first opening 221, and the annular guiding bevel 211 is arranged toward the first opening 221, so as to better guide at least a portion of the cylindrical body 31 to pass through the first opening 221.

[0043] Specifically, the lower end connecting sleeve of the branch wellbore pre-window positioning and hanging tool in this embodiment extends out from the first opening 221 of the main wellbore hollow whipstock 20 tool, and the upper part of the branch wellbore pre-window pipe group tool is sleeved in the upper end of the outer sleeve 22, and the second opening 321 corresponds to the position of the annular guide slope 211. The outer diameter of the lower end of the branch wellbore pre-window positioning and hanging tool in this embodiment is greater than the inner diameter of the annular guide slope 211 to prevent the lower end of the branch wellbore pre-window positioning and hanging tool from being inserted into the inner sleeve 21, so that the annular guide slope 211 can better play a guiding role.

[0044] In this embodiment, the downhole permanent positioning tool also includes a seal 12, a necking section 113 and an aluminum bottom plug 114. The downhole permanent positioning tool contains a necking section 113, and a seal 12 is provided outside the necking section 113. A downhole permanent positioning tool is set in the second casing 50 as a positioning base for the branch wellbore. After the downhole permanent positioning tool is designed with a seal 12, the lower part of the main wellbore and the branch wellbore can be isolated during setting. The downhole permanent positioning tool is designed with a locking hole (the locking hole is a snap-on hole) connected to the main wellbore re-entry guide tool.

[0045] The main wellbore hollow core whipstock 20 tool in this embodiment also includes a first lowering release hand 23 and a plug 24. The branch wellbore pre-window positioning and hanging tool is composed of a second lowering release hand 33 and a casing connection thread 322. The soluble metal liner pipe 32 is connected to the branch wellbore pre-window positioning and hanging tool by a connection screw.

[0046] Specifically, the multi-stage branch completion device in this embodiment further includes a second casing 50 and a branch wellbore casing 81 . The second casing 50 is disposed at one end of the downhole positioning structure 10 away from the main wellbore hollow core whipstock 20 .

[0047] The specific steps of using the 4-stage branch well completion device provided in this embodiment are as follows:

[0048] Step 1, lower the above-mentioned downhole permanent positioning tool to the set position of the main wellbore, and make the downhole permanent positioning tool at the set angle, expand and seal the permanent positioning tool, and then lower the removable whipstock to be hung on the downhole permanent positioning tool, lower the milling cone casing to open a window on the whipstock casing, lower the side drilling, and then take out the removable whipstock;

[0049] Step 2: lower the main wellbore hollow core whipstock 20 tool into the main wellbore, so that the lower end of the main wellbore hollow core whipstock 20 tool is correspondingly inserted into the upper end of the downhole permanent positioning tool;

[0050] Step 3: lower the branch wellbore pre-window positioning hanging tool and the casing string connected thereto into the main wellbore, so that the casing string at the lower end of the branch wellbore re-entry guide tool is guided by the annular guide slope 211 to extend from the first opening 221 and correspond to the position of the branch wellbore, thereby completing the installation of a 4-level branch well completion tool;

[0051] Step 4: Cementing the branch well. Insert the cementing pipe string 70 into the branch well. After cementing, the branch well performs subsequent operations. During cementing and subsequent operations, the drilling fluid reacts with the soluble metal liner 32 in the branch well pre-opening window positioning hanging tool to dissolve the soluble metal liner 32.

[0052] Step 5, after the branch well and other subsequent operations such as branch wellbore cementing are completed, the next operation pipe string 82 with grinding shoes 60 grinds through the cement in the inner core of the main wellbore hollow whipstock 20 tool and the aluminum bottom plug 114 in the downhole permanent positioning tool, and the main wellbore communication is completed.

[0053] From the above description, it can be seen that the above-mentioned embodiments of the present invention achieve the following technical effects: when cementing a branch well, the branch wellbore pre-opening window positioning suspension tool has a liner pipe to seal the pre-opening window. The cementing cement can be returned to the upper part of the branch wellbore pre-opening window pipe group tool in the same way as conventional cementing, and the pre-opening window is also cemented normally. After the cementing is completed, there is no need to lower the salvage tool to remove the soluble metal liner. The soluble metal liner dissolves in the drilling fluid by itself. This improves the cementing quality and reduces the difficulty of the operation.

[0054] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0055] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0056] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0057] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0058] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multi-stage branch completion device, characterized in that: include: Downhole positioning structure (10); A main wellbore hollow core whipstock (20) is arranged on the downhole positioning structure (10), the main wellbore hollow core whipstock (20) comprising an inner sleeve (21) and an outer sleeve (22), the inner sleeve (21) being arranged inside the outer sleeve (22), a first opening (221) being arranged on a side wall of the outer sleeve (22), and at least a portion of the inner sleeve (21) being located at the first opening (221); a positioning suspension structure (30) arranged on the main wellbore hollow core whipstock (20), the positioning suspension structure (30) comprising a cylindrical body (31) and an inner liner (32), the inner liner (32) being arranged in the cylindrical body (31), the cylindrical body (31) being provided with a second opening (321), the second opening (321) being arranged opposite to the first opening (221), and at least a portion of the inner liner (32) being located at the second opening (321); Wherein, the inner lining tube (32) is made of a soluble metal material; The multi-stage branch completion device further comprises a connecting piece (40), wherein the connecting piece (40) passes through the inner liner (32) and is connected to the cylindrical body (31); The connecting member (40) is a connecting screw, the inner liner tube (32) is provided with a connecting through hole, the cylindrical body (31) is provided with a threaded hole, and the connecting screw passes through the connecting through hole and is threadedly connected to the threaded hole; The connecting screw is made of soluble material; The downhole positioning structure (10) comprises a first casing (11), the first casing (11) being provided with a first clamping structure (111), and the inner sleeve (21) being provided with a second clamping structure (222) adapted to the first clamping structure (111); The first clamping structure (111) is a first positioning hole, the second clamping structure (222) is a first clamping protrusion, and the first clamping protrusion is clamped in the first positioning hole so that the outer sleeve (22) is arranged on the first sleeve (11); The end of the first sleeve (11) is provided with a first annular positioning surface (112), and the inner sleeve (21) is provided with a second annular positioning surface (224) adapted to the first annular positioning surface (112), wherein the first annular positioning surface (112) is used for fitting and positioning with the second annular positioning surface (224).

2. The multi-stage branch completion device according to claim 1, characterized in that: The outer sleeve (22) is provided with a third clamping structure (223), and the cylindrical body (31) is provided with a fourth clamping structure (311) that matches the third clamping structure (223).

3. The multi-stage branch completion device according to claim 2, characterized in that: The third clamping structure (223) is a clamping groove, the second clamping structure (222) is a second clamping protrusion, and the second clamping protrusion is clamped in the clamping groove so that the outer sleeve (22) is arranged on the cylindrical body (31).

4. The multi-stage branch completion device according to claim 1, characterized in that: The inner sleeve (21) has an annular guiding bevel (212), and the annular guiding bevel (212) is located at the end of the inner sleeve (21), so that the cylindrical body (31) passes through the first opening (221) under the guidance of the annular guiding bevel (212).

5. The multi-stage branch completion device according to claim 1, characterized in that: The multi-stage branch completion device also includes: The second casing (50) is arranged at an end of the downhole positioning structure (10) away from the main wellbore hollow core whipstock (20).

Images