Double-branch fracturing reentry and reinsertion tool

Abstract

According to the double-branch fracturing reentry and reinsertion tool, in the tool, an upper tie-back barrel is arranged in a perforated pipe column, and a second sealing piece is arranged on the outer side of the upper tie-back barrel so that second high-pressure sealing can be formed between the upper tie-back barrel and the inner surface of the perforated pipe column; the upper tie-back sealing pipe is inserted into the upper tie-back barrel, the locking inner pipe is arranged around the upper tie-back sealing pipe and is in threaded connection with the upper tie-back sealing pipe, and the upper tie-back sealing pipe and the upper tie-back barrel form first high-pressure sealing through a first sealing piece; the lower tieback pipe is in threaded connection in the upper tieback cylinder, and a third sealing piece is arranged on the outer side of the bottom of the lower tieback pipe; the branch lower tieback barrel comprises an external thread in threaded connection with the perforated pipe column and an internal thread in threaded connection with the lower tieback pipe, and the smooth inner surface is matched with a third sealing piece to form a third high-pressure seal; the main borehole lower tie-back barrel is installed on the lower portion of the main borehole suspension packer, and after the main borehole lower tie-back barrel is restarted into the main borehole, a third sealing piece at the bottom of the lower tie-back pipe and the inner surface of the main borehole lower tie-back barrel form fourth high-pressure sealing. According to the tool, accurate reentry and back insertion of main and branch wells are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of petroleum drilling branch well drilling and completion, and in particular to a double-branch fracturing re-entry and re-insertion tool. Background Art

[0002] Branch well technology is an advanced drilling and completion technology for improving recovery and single well production. Due to the complex wellbore structure, it is difficult to match it with the fracturing process. The existing branch well technology often requires multiple re-entry to achieve fracturing of the main and branch wellbores respectively. The process is often complicated, with many processes, long cycles and high costs. Therefore, the reliability optimization of branch well fracturing technology is an important task to promote the widespread application of branch well technology in low permeability reservoirs, and whether it can quickly and accurately re-enter the main and branch wellbores is one of the key technologies that determine the simplification of branch well fracturing technology, ultimately achieving the goal of reducing processes and improving economic efficiency.

[0003] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0004] The purpose of the present invention is to provide a double-branch fracturing re-entry and reinsertion tool for branch well fracturing re-entry and reinsertion, which can achieve accurate re-entry and reinsertion of the main and branch wellbores without rotating the tubing, overcome the problem of multiple tripping and lowering of the tubing in conventional processes, and greatly improve the efficiency of the branch well fracturing process.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A double-branch fracturing re-entry tool of the present invention comprises:

[0007] a main wellbore casing having window opening points;

[0008] The perforated pipe string is anchored and hung in the main wellbore casing above the window opening point. The perforated pipe string opens a long opening and aligns with the main wellbore to form a main wellbore re-entry channel;

[0009] The main wellbore hanging packer is anchored to the main wellbore casing below the window opening point;

[0010] An upper return tube is arranged in the perforated pipe column, a tooth buckle is arranged on the inner side of the top of the upper return tube, and a second sealing member is arranged on the outer side of the upper return tube to form a high-pressure seal with the inner surface of the perforated pipe column;

[0011] An upper tie-back locking tool is inserted into the upper tie-back cylinder, and the upper tie-back locking tool includes:

[0012] The upper return sealing tube is inserted into the upper return tube.

[0013] The locking inner tube is arranged around the upper return sealing tube and is threadedly connected to the upper return sealing tube. A tooth buckle is provided on the outer side of the lower part of the locking inner tube to lock the upper return tube.

[0014] A first fixing pin, which locks the locking inner tube and the upper return sealing tube,

[0015] A first sealing member, which is arranged on the outer side of the lower part of the upper return sealing pipe, and the upper return sealing pipe and the upper return tube form a high-pressure seal through the first sealing member;

[0016] A lower return pipe is threadedly connected to the upper return tube, and a third sealing member is provided on the outer side of the bottom of the lower return pipe;

[0017] A second fixing pin, which locks the lower return pipe and the upper return pipe;

[0018] The branch lower return pipe comprises an external thread threadedly connected to the open hole pipe column and an internal thread threadedly connected to the lower return pipe, a smooth inner surface of a predetermined length is processed at the lower part of the internal thread, and the smooth inner surface cooperates with the third sealing member to form a high-pressure seal three;

[0019] The main wellbore lower return tube is installed at the lower part of the main wellbore suspension packer. After re-entering the main wellbore, the third sealing member at the bottom of the lower return tube forms a high-pressure seal four with the inner surface of the main wellbore lower return tube.

[0020] In the described double-branch fracturing re-entry and re-insertion tool, the branch tubing string suspension packer is anchored and hung in the main wellbore casing above the window opening point, and the branch tubing string suspension packer is connected to the opening tubing string.

[0021] In the described double-branch fracturing re-entry and re-insertion tool, the branch pipe column suspension packer has a rubber cylinder which is sealed and connected to the open-hole pipe column.

[0022] In the dual-branch fracturing re-entry tool, the perforating tubing string and the branch tubing string suspension packer are lowered into the branch wellbore.

[0023] In the described double-branch fracturing re-entry and re-insertion tool, the upper part of the upper reconnection sealing pipe is connected to the fracturing reconnection pipe string.

[0024] In the dual-branch fracturing re-entry tool, the fracturing re-entry pipe string includes an oil pipe or a casing.

[0025] In the described double-branch fracturing re-entry and re-insertion tool, the horse tooth buckle of the locking inner tube is an elastic petal structure. When the locking inner tube enters the upper reconnection tube, the petal structure elastically contracts so that the locking inner tube and the upper reconnection tube are inserted and locked.

[0026] In the dual-branch fracturing re-entry and re-insertion tool, the horse tooth buckle for locking the inner tube is a positive buckle.

[0027] In the dual-branch fracturing re-entry and re-insertion tool, the upper re-connection tube and the lower re-connection tube are sealed by an O-ring.

[0028] In the dual-branch fracturing re-entry and re-insertion tool, the central axes of the upper re-connection tube, the upper re-connection sealing tube, the locking inner tube and the lower re-connection tube are in a collinear line.

[0029] In the above technical scheme, the double-branch fracturing re-entry and re-insertion tool provided by the present invention has the following beneficial effects: the cross-window re-insertion fracturing process can use the seal to make the upper and lower pipe strings of the window form a complete seal, meet the requirements of high-pressure fracturing, avoid the open hole formation at the window due to excessive pressure leakage, and ensure the normal implementation of the fracturing construction. The present invention adopts a two-stage re-insertion process, and a small-sized re-insertion plug is used at the bottom. After the branch wellbore fracturing is completed, the re-insertion pipe string can automatically re-enter the main wellbore under the action of gravity without rotating the pipe string, which greatly reduces the complexity of the branch well fracturing process and makes the branch well fracturing technology more economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0031] Figure 1 A schematic structural diagram of a branch wellbore completion string before reinsertion of a dual-branch fracturing re-entry reinsertion tool provided in an embodiment of the present invention.

[0032] Figure 2 A schematic structural diagram of a branch wellbore completion string after reinsertion of a dual-branch fracturing re-entry reinsertion tool provided in an embodiment of the present invention.

[0033] Figure 3 A schematic structural diagram of an upper tie-back locking tool for a dual-branch fracturing re-entry tool provided in an embodiment of the present invention.

[0034] Figure 4 A schematic structural diagram of a main wellbore tubular string connected back to a double-branch fracturing re-entry reinsertion tool before reinsertion provided in an embodiment of the present invention.

[0035] Figure 5 A schematic structural diagram of a dual-branch fracturing re-entry and re-insertion tool provided in an embodiment of the present invention and connected back to a main wellbore tubular string after re-insertion. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0039] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0040] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0041] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0043] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0044] See also Figure 1-5 As shown, in one embodiment, a dual-branch fracturing re-entry tool of the present invention comprises:

[0045] Main wellbore casing 0-1, which has a window opening point;

[0046] The perforating string 0-3 is anchored in the main wellbore casing 0-1 above the window opening point. The perforating string 0-3 opens a long opening and aligns with the main wellbore to form a main wellbore re-entry channel;

[0047] The main wellbore hanging packer 0-4 is anchored in the main wellbore casing 0-1 below the window opening point;

[0048] An upper return tube 5 is arranged in the perforated pipe column 0-3, a tooth buckle is arranged on the inner side of the top of the upper return tube 5, and a second sealing member 6 is arranged on the outer side of the upper return tube 5 to form a high-pressure seal 2 with the inner surface of the perforated pipe column 0-3;

[0049] The upper tie-back locking tool is inserted into the upper tie-back tube 5. The upper tie-back locking tool includes:

[0050] The upper return sealing pipe 1 is inserted into the upper return tube 5.

[0051] The locking inner tube 3 is arranged around the upper return sealing tube 1 and is threadedly connected to the upper return sealing tube 1. A tooth buckle is provided on the outer side of the lower part of the locking inner tube 3 to lock the upper return tube 5.

[0052] The first fixing pin 2 locks the locking inner tube 3 and the upper return sealing tube 1.

[0053] A first sealing member 4 is provided on the outer side of the lower part of the upper return sealing pipe 1, and the upper return sealing pipe 1 and the upper return tube 5 form a high pressure seal 1 through the first sealing member 4;

[0054] A lower return pipe 7, which is threadedly connected to the upper return pipe 5, and a third sealing member 10 is provided on the outer side of the bottom of the lower return pipe 7;

[0055] A second fixing pin, which locks the lower return pipe 7 and the upper return pipe 5;

[0056] The branch lower return pipe 8 includes an external thread threadedly connected to the opening pipe column 0-3 and an internal thread threadedly connected to the lower return pipe 7, and a smooth inner surface of a predetermined length is processed at the lower part of the internal thread, and the smooth inner surface cooperates with the third sealing member 10 to form a high-pressure seal three;

[0057] The main wellbore lower tie-back tube 9 is installed at the lower part of the main wellbore suspension packer 0-4. After re-entering the main wellbore, the third sealing member 10 at the bottom of the lower tie-back tube 7 forms a high-pressure seal four with the inner surface of the main wellbore lower tie-back tube 9.

[0058] In a preferred embodiment of the dual-branch fracturing re-entry tool, the branch tubing string suspension packer 0-2 is anchored and hung in the main wellbore casing 0-1 above the window opening point, and the branch tubing string suspension packer 0-2 is connected to the opening tubing string 0-3.

[0059] In a preferred embodiment of the dual-branch fracturing re-entry and re-insertion tool, the branch tubing string suspension packer 0-2 has a rubber sleeve that is sealed and connected to the opening tubing string 0-3.

[0060] In a preferred embodiment of the dual-branch fracturing re-entry tool, the perforating tubing string 0-3 and the branch tubing string suspension packer 0-2 are lowered into the branch wellbore.

[0061] In a preferred embodiment of the dual-branch fracturing re-entry tool, the upper portion of the upper reconnection sealing pipe 1 is connected to the fracturing reconnection pipe string.

[0062] In a preferred embodiment of the dual-branch fracturing re-entry tool, the fracturing re-entry pipe string includes an oil pipe or a casing.

[0063] In a preferred embodiment of the dual-branch fracturing re-entry and re-insertion tool, the tooth buckle of the locking inner tube 3 is an elastic petal structure. When the locking inner tube 3 enters the upper reconnection tube 5, the petal structure elastically contracts so that the locking inner tube 3 and the upper reconnection tube 5 are inserted and locked.

[0064] In a preferred embodiment of the dual-branch fracturing re-entry and re-insertion tool, the horse tooth buckle for locking the inner tube 3 is a positive buckle.

[0065] In a preferred embodiment of the dual-branch fracturing re-entry and re-insertion tool, the upper reconnection tube 5 and the lower reconnection tube 7 are sealed by an O-ring.

[0066] In a preferred embodiment of the dual-branch fracturing re-entry tool, the central axes of the upper reconnection tube 5, the upper reconnection sealing tube 1, the locking inner tube 3 and the lower reconnection tube 7 are collinear.

[0067] In one embodiment, the outer diameter of the upper tieback tool is greater than the outer diameter of the lower tieback pipe 7 .

[0068] In one embodiment, a dual-branch fracturing re-entry tool comprises:

[0069] Main wellbore casing 0-1, which has a window opening point;

[0070] The branch string hanging packer 0-2 is anchored in the main wellbore casing 0-1 above the window opening point;

[0071] The perforating string 0-3 is anchored and hung in the main wellbore casing 0-1 above the window opening point and connected to the branch string hanging packer 0-2. The perforating string 0-3 opens a long opening and aligns with the main wellbore to form a main wellbore re-entry channel;

[0072] The main wellbore hanging packer 0-4 is anchored in the main wellbore casing 0-1 below the window opening point;

[0073] An upper return tube 5 is arranged in the perforated pipe column 0-3, a tooth buckle is arranged on the inner side of the top of the upper return tube 5, and a second sealing member 6 is arranged on the outer side of the upper return tube 5 to form a high-pressure seal 2 with the inner surface of the perforated pipe column 0-3;

[0074] The upper tie-back locking tool is inserted into the upper tie-back tube 5. The upper tie-back locking tool includes:

[0075] The upper return sealing pipe 1 is inserted into the upper return tube 5, and the upper part of the upper return sealing pipe 1 is connected to the fracturing return pipe string.

[0076] The locking inner tube 3 is arranged around the upper return sealing tube 1 and is threadedly connected to the upper return sealing tube 1. A horse tooth buckle is provided on the outer side of the lower part of the locking inner tube 3. When the locking inner tube 3 enters the upper return tube 5, it elastically contracts so that the two can be permanently inserted and locked.

[0077] The first fixing pin 2 locks the locking inner tube 3 and the upper return sealing tube 1.

[0078] A first sealing member 4 is provided on the outer side of the lower part of the upper return sealing pipe 1, and the upper return sealing pipe 1 and the upper return tube 5 form a high pressure seal 1 through the first sealing member 4;

[0079] The lower return pipe 7 is threadedly connected to the upper return pipe 5 and is sealed by an O-ring. A third sealing member 10 is provided on the outer side of the bottom of the lower return pipe 7;

[0080] A second fixing pin, which locks the lower return pipe 7 and the upper return pipe 5;

[0081] The branch lower return pipe 8 includes an external thread threadedly connected to the opening pipe column 0-3 and an inverted internal thread threadedly connected to the lower return pipe 7. A smooth inner surface of a predetermined length is processed at the lower part of the inverted internal thread. The smooth inner surface cooperates with the third sealing member 10 to form a high-pressure seal three;

[0082] The main wellbore lower tie-back tube 9 is installed at the lower part of the main wellbore suspension packer 0-4. After re-entering the main wellbore, the third sealing member 10 at the bottom of the lower tie-back tube 7 establishes a high-pressure seal four with the inner surface of the main wellbore lower tie-back tube 9.

[0083] In one embodiment, the branch pipe string hanger is connected to the perforated pipe string 0-3 and anchored in the main wellbore casing 0-1 above the window opening point; the perforated pipe string 0-3 is processed into a long opening and aligned with the main wellbore to form a main wellbore re-entry channel; the main wellbore suspension packer 0-4 is anchored on the main wellbore casing 0-1 at the lower part of the window. The upper return sealing pipe 1, the first fixed pin 2, the locking inner pipe 3, and the first sealing member 4 constitute the upper return locking tool. The upper return sealing pipe 1 and the locking inner pipe 3 are connected by threads, and the first fixed pin 2 prevents the two from rotating relative to each other, so as to prevent the upper return sealing pipe 1 and the locking inner pipe 3 from loosening during subsequent operations. After the upper return sealing pipe 1 is re-inserted, it will form a high-pressure seal with the upper return pipe 5 through the first sealing member 4. The upper part of the upper return sealing pipe 1 is connected to the fracturing return pipe string, such as a tubing or casing. The top inner side of the upper return tube 5 is designed with a tooth buckle, and the lower part of the locking inner tube 3 is also a tooth buckle, and the tooth buckle position of the locking inner tube 3 is designed to be a petal structure to make it have high elasticity. When the locking inner tube 3 enters the upper return tube 5, it will elastically contract so that the two can be permanently inserted and locked. The tooth buckle adopts a positive buckle design, and the buckle will not be loosened and unlocked during the subsequent forward operation. The upper return tube 5 and the lower return tube 7 are connected by threads, and a seal is formed by an O-ring, and the second fixed pin is locked to prevent the two from rotating relative to each other. The upper return tube 5 forms a high-pressure seal 2 with the smooth inner surface near the upper part of the perforated pipe column 0-3 through the second seal 6. The seal here is used to completely isolate the fluid above and below the window. During fracturing construction, back pressure can be applied above this position without causing pressure on the window. The branch lower return tube 8 is connected to the perforated pipe column 0-3 through an external thread. The branch lower return tube 8 is connected to the lower return pipe 7 through an inverted internal thread. A certain length of smooth inner surface is processed at the lower part of the inverted internal thread, which can cooperate with the third sealing member 10 at the bottom of the lower return pipe 7 to form a high-pressure seal. The main wellbore lower return tube 9 is installed at the lower part of the main wellbore suspension packer 0-4. After re-entering the main wellbore, Figure 5As shown, the third sealing member 10 at the bottom of the lower return pipe 7 establishes four high-pressure seals with the inner surface of the lower return pipe 9 of the main wellbore. The four high-pressure seals can realize hydraulic isolation across the windows when the branch wellbore and the main wellbore are fracturing, so as to avoid direct contact of the window position with weaker pressure bearing capacity with high-pressure fluid.

[0084] In one embodiment, after the branch wellbore is drilled and run, the branch wellbore fracturing completion string, the opening string 0-3 and the branch string suspension packer 0-2 are lowered into the well. The opening string 0-3 is aligned with the main wellbore in some way, and then the suspension packer is set and released. Cementing or non-cementing is selected according to the needs. After the running string is pulled out, the upper tie-back locking tool is lowered. Figure 3 As shown and inserted into the upper return tube 5, as Figure 2 As shown, the locking inner tube 3 elastically contracts and enters the tooth buckle at the top of the upper return tube 5 to achieve locking, and at the same time, the first seal 4 at the bottom of the locking inner tube 3 contacts the sealing surface in the upper return tube 5 to form a seal. Relying on the second seal 6 and the rubber seal of the branch pipe string suspension packer 0-2, the pipe string annulus above the second seal 6 can be completely isolated from the window, so that the back pressure can be applied to the annulus outside the return pipe string without contacting the open hole formation at the window to meet the fracturing process requirements. After the upper part of the branch wellbore is re-inserted, a ball or bridge plug can be dropped to perform segmented fracturing of the branch wellbore. After the fracturing of the branch wellbore is completed, operations such as drilling plugs, backflow, and well pressure can be carried out, and the construction of re-entry into the main wellbore can be carried out under the premise of ensuring the safety of well control of the branch wellbore.

[0085] In one embodiment, after the branch wellbore fracturing construction is completed, the reverse thread of the lower return pipe 7 and the lower return tube is loosened by rotating the pipe string forward so that both are released. Since the connection thread of the locking inner pipe 3 of the upper return tool and the upper return tube 5 is positively threaded, it will not be loosened with the forward rotation of the pipe string and is always in a locked state. The pipe string is lifted up to a position above the window and the lowered pipe string is re-entered, as shown in the attached Figure 4 As shown, the upper tie-back tool with a large outer diameter has not yet entered the interior of the hanger and thus will not have a straightening effect on the tubing string. The round head with a small outer diameter at the bottom of the lower tie-back tube 7 will automatically enter the main wellbore under the action of its own weight. When the lower tie-back tube 7 is fully inserted into the lower tie-back tube, a high-pressure seal is established. The upper tie-back tool enters the smooth tube inside the hanger to establish an upper seal again, completing the main wellbore re-entry operation.

[0086] Finally, it should be noted that the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making any creative work are within the scope of protection of the present application.

[0087] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A double-branch fracturing re-entry tool, characterized in that: These include, a main wellbore casing having window opening points; The perforated pipe string is anchored and hung in the main wellbore casing above the window opening point. The perforated pipe string opens a long opening and aligns with the main wellbore to form a main wellbore re-entry channel; The main wellbore hanging packer is anchored to the main wellbore casing below the window opening point; An upper return tube is arranged in the perforated pipe column, a tooth buckle is arranged on the inner side of the top of the upper return tube, and a second sealing member is arranged on the outer side of the upper return tube to form a high-pressure seal with the inner surface of the perforated pipe column; An upper tie-back locking tool is inserted into the upper tie-back cylinder, and the upper tie-back locking tool includes: The upper return sealing tube is inserted into the upper return tube. The locking inner tube is arranged around the upper return sealing tube and is threadedly connected to the upper return sealing tube. A tooth buckle is provided on the outer side of the lower part of the locking inner tube to lock the upper return tube. A first fixing pin, which locks the locking inner tube and the upper return sealing tube, A first sealing member, which is arranged on the outer side of the lower part of the upper return sealing pipe, and the upper return sealing pipe and the upper return tube form a high-pressure seal through the first sealing member; A lower return pipe is threadedly connected to the upper return pipe, and a third sealing member is provided on the outer side of the bottom of the lower return pipe; A second fixing pin, which locks the lower return pipe and the upper return pipe; The branch lower return pipe comprises an external thread threadedly connected to the open hole pipe column and an internal thread threadedly connected to the lower return pipe, a smooth inner surface of a predetermined length is processed at the lower part of the internal thread, and the smooth inner surface cooperates with the third sealing member to form a high-pressure seal three; The main wellbore lower return tube is installed at the lower part of the main wellbore suspension packer. After re-entering the main wellbore, the third sealing member at the bottom of the lower return tube forms a high-pressure seal four with the inner surface of the main wellbore lower return tube.

2. A dual-branch fracturing re-entry tool according to claim 1, characterized in that: The branch pipe string suspension packer is anchored and hung in the main wellbore casing above the window opening point, and the branch pipe string suspension packer is connected to the opening pipe string.

3. A dual-branch fracturing re-entry tool according to claim 2, characterized in that: The branch pipe column suspension packer has a rubber sleeve which is sealed and connected to the open-hole pipe column.

4. A dual-branch fracturing re-entry tool according to claim 2, characterized in that: The perforated tubular column and the branch tubular column suspension packer are lowered into the branch wellbore.

5. A dual-branch fracturing re-entry tool according to claim 1, characterized in that: The upper part of the upper return sealing pipe is connected to the fracturing return pipe string.

6. A dual-branch fracturing re-entry tool according to claim 5, characterized in that: The fracturing tie-back pipe string includes an oil pipe or a casing.

7. A dual-branch fracturing re-entry tool according to claim 1, characterized in that: The horse tooth buckle of the locking inner tube is an elastic petal structure. When the locking inner tube enters the upper return tube, the petal structure elastically contracts so that the locking inner tube and the upper return tube are inserted and locked.

8. A dual-branch fracturing re-entry tool according to claim 1, characterized in that: The horse tooth buckle for locking the inner tube is a positive buckle.

9. A dual-branch fracturing re-entry tool according to claim 1, characterized in that: The upper return connection tube and the lower return connection tube are sealed by an O-ring.

10. A dual-branch fracturing re-entry tool according to claim 1, characterized in that: The central axes of the upper return connection tube, the upper return connection sealing tube, the locking inner tube and the lower return connection pipe are collinear.

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