Branch well construction process and branch well structure

Abstract

The invention belongs to the technical field of oil and gas drilling, and particularly relates to a multilateral well construction technology and a multilateral well structure. The multilateral well construction technology comprises the following steps that S1, a main borehole is temporarily blocked; s2, sidetrack drilling is conducted on a branch well hole through a drilling tool; s3, taking out the drilling tool after the multilateral well hole is drilled; s4, a bent pipe capable of supporting the well wall of the branch well hole is put into the joint of the branch well hole and the main well hole, one end of the bent pipe is located in the main well hole, and the other end of the bent pipe is located in the branch well hole; s5, fracturing is conducted on the branch well holes; and S6, plugging of the main borehole is relieved, an oil pipe with a packer is put into the well from the wellhead, and the lower end of the oil pipe is made to communicate with the bent pipe.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas drilling, and in particular, relates to a branch well construction process and a branch well structure. Background Art

[0002] The branch well staged fracturing technology is a new technical development direction for the development of low permeability oil and gas reservoirs. Two or more branch horizontal wellbores are drilled from the side of a main wellbore to enter the oil and gas reservoir. The branch wellbores are staged and fractured in sequence. Branch wells are used to reduce the comprehensive decline of gas fields, revitalize idle assets of gas fields, achieve re-evaluation and re-exploitation of old areas, and help old gas fields reach a new level of stable production. The side drilling transformation of old wells has become the main technology for improving the efficiency and increasing production of old oil fields. However, some old wells have technical problems such as unstable side drilling wellbores and easy collapse of side drilling wellbores.

[0003] Therefore, it is urgent to develop a branch well construction technology suitable for side drilling transformation of old wells. Summary of the invention

[0004] In view of the above-mentioned technical problems, the present invention aims to propose a branch well construction process, which can solve the above-mentioned technical problems.

[0005] According to the present invention, a branch well construction process is provided, comprising the following steps:

[0006] S1. Temporarily plug the main wellbore;

[0007] S2, using drilling tools to side-drill branch wellbores;

[0008] S3. After the branch wellbore is drilled, the drilling tool is removed;

[0009] S4, releasing the blockage of the main wellbore;

[0010] S5, lowering a curved pipe capable of supporting the well wall of the branch wellbore at the connection between the branch wellbore and the main wellbore, wherein the curved pipe includes a main well channel and a branch well channel;

[0011] S6, fracturing the branch wellbore;

[0012] S7, lowering an oil pipe with an oil pipe packer into the well from the wellhead, and making the lower end of the oil pipe communicate with the branch well channel of the elbow.

[0013] In a specific embodiment, a switch sleeve is provided on the oil pipe, and the switch sleeve is located between the oil pipe packer and the elbow.

[0014] In a specific embodiment, during the oil production process, when it is necessary to produce the branch wellbore separately, the switch sleeve is closed; when it is necessary to produce the main wellbore and the branch wellbore together, the switch sleeve is opened.

[0015] In a specific embodiment, the switch sleeve realizes switching by wire operation.

[0016] In a specific embodiment, in S1, a rupture disk is arranged in the main wellbore to temporarily block the main wellbore.

[0017] In a specific embodiment, in S4, the rupture disk is fractured by pumping pressure into the well, thereby releasing the blockage of the main wellbore.

[0018] In a specific embodiment, in S2, the drilling tool includes a whipstock, and the whipstock is lowered into the well to achieve side drilling of the branch wellbore through the guiding effect of the whipstock.

[0019] In a specific embodiment, a fracturing tool string is arranged on the elbow, and in S6, the branch wellbore is fractured using the fracturing tool string.

[0020] In a specific embodiment, the fracturing tool string includes a fracturing sleeve and a bridge plug.

[0021] According to the present invention, there is also provided a branch well structure manufactured according to the branch well construction process of the present invention, comprising:

[0022] A curved pipe is arranged at the connection between the branch wellbore and the main wellbore through a hanger, wherein the hanger is located in the main wellbore;

[0023] The elbow comprises a main well channel and a branch well channel, wherein the branch well channel connects the branch wellbore with the main wellbore located above the hanger, and the main well channel connects the main wellbore located at the upper and lower sides of the hanger; and

[0024] An oil pipe connected to the branch wellbore is arranged above the elbow, and the oil pipe is arranged in the main wellbore through an oil pipe packer. The lower end of the oil pipe is connected to the branch well channel, and a switch sleeve is arranged on the oil pipe, and the switch sleeve is located between the elbow and the oil pipe packer.

[0025] Compared with the prior art, the advantages of the present application are as follows.

[0026] The present invention adopts the bent pipe lowering technology, which can effectively solve the technical problem of unstable and easy collapse of the wellbore wall of the side-drilled branch well.

[0027] The present invention uses a rupture disk as a special anti-leakage device for the main wellbore, which can effectively protect the reservoir of the main wellbore from pollution and realize the connection of the main wellbore by wellhead control.

[0028] The present invention realizes the combined production and separate production of the main wellbore and the branch wellbore by switching the switch sleeve, thereby reducing the investment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be described below with reference to the accompanying drawings.

[0030] Figure 1 A schematic diagram showing one embodiment of a main wellbore;

[0031] Figure 2 A schematic diagram showing an embodiment of temporarily plugging a main wellbore using a rupture disk;

[0032] Figure 3 A schematic diagram showing an embodiment of a running whipstock;

[0033] Figure 4 A schematic diagram showing an embodiment of a sidetracked branch wellbore;

[0034] Figure 5 A schematic diagram showing an embodiment of removing the whipstock;

[0035] Figure 6 A schematic diagram showing an embodiment of a lower elbow is shown;

[0036] Figure 7 A schematic diagram showing an embodiment of a lower oil pipe;

[0037] Figure 8 is a schematic diagram of an embodiment of an open hole packer;

[0038] Fig. 9 is a schematic diagram of an embodiment of a rubber cartridge assembly;

[0039] Fig.10 A schematic diagram of an embodiment of a sealing assembly.

[0040] The reference numerals in the figures are as follows:

[0041] 1. Central tube; 11. Flow channel; 12. First pressure transmission hole; 13. Second pressure transmission hole; 14. First pipe section; 15. Second pipe section;

[0042] 2. Rubber cylinder assembly; 21. Middle rubber cylinder; 22. Spacer ring; 23. Side rubber cylinder; 24. Gasket ring; 25. Inner support ring; 26. Shoulder guard;

[0043] 3. Retaining ring;

[0044] 4. Double cylinder assembly; 41. First cylinder; 411. First large diameter portion; 412. First small diameter portion; 42. Second cylinder; 421. Second large diameter portion; 422. Second small diameter portion; 43. Connecting sleeve; 44. Limiting spring; 45. Sealing assembly; 451. Back ring; 452. V-ring; 453. Pressing ring;

[0045] 5. Shear pins;

[0046] 61. a first sealing member; 62. a second sealing member;

[0047] 71. Locking ring; 72. Locking circlip;

[0048] 81. retaining ring; 82. set screw;

[0049] 10. Open hole packer;

[0050] 101. Main wellbore; 102. Rupture disk; 201. Rupture disk packer; 103. Whipstock; 104. Drilling tool; 105. Branch wellbore; 106. Bend pipe; 601. Hanger; 602. Main well channel; 603. Branch well channel; 107. Tubing; 108. Tubing packer; 109. Fracturing tool string; 100. Switch sleeve.

[0051] In the present application, all drawings are schematic drawings, which are only used to illustrate the principles of the present invention and are not drawn according to the actual scale. DETAILED DESCRIPTION

[0052] The present invention will be described below with reference to the accompanying drawings.

[0053] It should be noted that the directional terms or qualifiers "upper" and "lower" used in this application are all directed to the referenced Figure 1 They are not intended to define the absolute positions of the components involved, but may vary depending on the specific circumstances.

[0054] Figure 1 Schematic diagram of the structure of the main wellbore 101 in this embodiment.

[0055] According to the present invention, a branch well construction process is provided, comprising the following steps.

[0056] S1. Temporarily plugging the main wellbore 101.

[0057] like Figure 2 As shown, in this embodiment, the main wellbore 101 is temporarily blocked by lowering a rupture disk 102 into the main wellbore 101 , and the rupture disk 102 is disposed in the main wellbore 101 through a rupture disk packer 201 .

[0058] S2. Use a drilling tool to side-drill the branch wellbore 105.

[0059] like Figure 3 As shown, in this embodiment, the drilling tool mainly includes a whipstock 103 and a drilling tool 104. First, the whipstock 103 is lowered into the main wellbore. A keyway is provided on the rupture disk packer 201, and a key for matching with the keyway of the rupture disk packer 201 is provided at the lower part of the whipstock 103. After the whipstock 103 is put into the well, its key matches with the keyway of the rupture disk packer 201, so as to find the window opening position accurately. Then, the drilling tool 104 is lowered, as shown in FIG. Figure 4 As shown, the drilling tool 104 performs side drilling of the branch wellbore 105 under the guidance of the whipstock 103 .

[0060] S3. After the branch wellbore 105 is drilled, the drilling tool is removed.

[0061] First, lift the drill pipe to remove the drilling tool 104 from the well. Then, Figure 5 As shown, the whipstock 103 is recovered using a whipstock recovery tool and taken out from the well.

[0062] S4. Unblocking the main wellbore 101.

[0063] S5. A curved pipe 106 capable of supporting the well wall of the branch wellbore 105 is lowered into the connection between the branch wellbore 105 and the main wellbore 101. One end of the curved pipe 106 is located in the main wellbore 101, and the other end is located in the branch wellbore 105. The curved pipe 106 includes a main well channel 602 and a branch well channel 603.

[0064] like Figure 6 As shown, the lower end of the elbow 106 extends into the branch wellbore 105, and the upper end of the elbow 106 is fixed in the main wellbore 101 through the hanger 601. The branch well channel 603 connects the branch wellbore 105 with the main wellbore 101 located above the hanger 601, and the main well channel 602 connects the main wellbore 101 located above and below the hanger 601.

[0065] S6. Fracturing the branch wellbore 105.

[0066] A fracturing tool string 109 is preset on the elbow 106 . A pipeline used for fracturing is lowered from the wellhead and connected to the branch well channel 603 . The branch wellbore 105 is fractured through the fracturing tool string 109 .

[0067] In a specific embodiment, in a specific embodiment, the fracturing tool string 109 includes a plurality of open hole packers 10 and fracturing sleeves arranged alternately in sequence along the axial direction. During the fracturing process, the lower end of the fracturing tool string 109 is blocked by dropping a ball or other means, and pressure is held in the fracturing tool string 109 through the elbow 106 to start the open hole packer 10, so that the open hole packer 10 can isolate the annulus between the fracturing tool string 109 and the branch wellbore 105. Then, the pressure holding balls adapted to each fracturing sleeve in the fracturing tool string 109 are sequentially dropped through the elbow 106 and pressure is held, and each fracturing sleeve is sequentially opened and fractured.

[0068] S7, the oil pipe 107 with the oil pipe packer 108 is lowered into the well from the wellhead, and the lower end of the oil pipe 107 is connected to the branch well channel 603 of the elbow 106, as shown in FIG. Figure 7 As shown. In this embodiment, the upper end surface of the elbow 106 is the outlet of the branch well channel 603 and the main well channel 602. The outlet of the branch well channel 603 is arranged in a circular shape and is coaxially arranged on the upper end surface of the elbow 106. The outlet of the main well channel 602 is arranged in an annular shape and is arranged radially outside the outlet of the branch well channel 603. Through this arrangement, the lower end of the oil pipe 107 can be quickly connected to the branch well channel 603.

[0069] The tubing packer 108 has an anchoring and sealing function.

[0070] According to the present invention, in a specific embodiment, a switch sleeve 100 is preset on the tubing 107 , and the switch sleeve 100 is located between the tubing packer 108 and the hanger 601 of the elbow 106 .

[0071] During the oil production process, when the branch wellbore 105 needs to be produced separately, the switch sleeve 100 is closed, and the oil and gas in the main wellbore cannot enter the oil pipe 107. When the main wellbore 101 and the branch wellbore 105 need to be produced together, the switch sleeve 100 is opened, and the oil and gas in the main wellbore can enter the oil pipe 107 through the main well channel 602 and the switch sleeve 100.

[0072] In this embodiment, the switch sleeve 100 realizes switching by wire operation.

[0073] It should be noted that the specific structures of the rupture disk 102, rupture disk packer 201, whipstock 103, drilling tool 104, hanger 601, tubing packer 108, fracturing tool string 109, and switch sleeve 100 in this embodiment are well known to those skilled in the art and will not be repeated here.

[0074] According to the present invention, a branch well structure manufactured by the branch well construction process provided by the present invention is also provided, which mainly includes a bend pipe 106 and an oil pipe 107, such as Figure 7 shown.

[0075] The elbow 106 is arranged at the connection between the branch wellbore 105 and the main wellbore 101 through the hanger 601. The upper end of the elbow 106 is located in the main wellbore 101, and the lower end of the elbow 106 is located in the branch wellbore 105. The hanger 601 is located in the main wellbore 101 and above the branch wellbore 105.

[0076] The elbow 106 includes a main well channel 602 and a branch well channel 603. The branch well channel 603 connects the branch wellbore 105 with the main wellbore 101 located above the hanger 601, and the main well channel 602 connects the main wellbore 101 located on the upper and lower sides of the hanger 601. Specifically, the upper and lower ports of the branch well channel 603 are respectively located on the upper and lower end surfaces of the elbow 106. The upper port of the main well channel 602 is located on the upper end surface of the elbow 106, and the lower port of the main well channel 602 is located on the side of the elbow 106 and connects to the main wellbore 101 below the hanger 601.

[0077] The oil pipe 107 is arranged above the elbow 106 and communicates with the branch wellbore 105. The oil pipe 107 is arranged in the main wellbore 101 through the oil pipe packer 108, and the oil pipe packer 108 is located above the hanger 601. The lower end of the oil pipe 107 is connected to the branch well channel 603. A switch sleeve 100 is arranged on the oil pipe 107, and the switch sleeve 100 is located between the hanger 601 of the elbow 106 and the oil pipe packer 108.

[0078] According to the present invention, there is provided an open hole packer 10, such as Figure 8 As shown, it mainly includes a central tube 1, a retaining ring 3, a double-liquid cylinder assembly 4 and a rubber cartridge assembly 2.

[0079] In this embodiment, a flow channel 11 is coaxially arranged in the central tube 1 and is configured in the shape of a cylindrical tube.

[0080] The retaining ring 3 is arranged on the outside of the central tube 1. In this embodiment, the retaining ring 3 is coaxially sleeved on the outside of the central tube 1.

[0081] The rubber cylinder assembly 2 is coaxially sleeved on the outer side of the central tube 1. Figure 8 As shown, the lower end of the rubber cartridge assembly 2 is in axial contact with the upper end of the retaining ring 3 .

[0082] The double cylinder assembly 4 is coaxially arranged on the outside of the central tube 1 through the shear pin 5. Figure 8 As shown, the lower end of the dual-cylinder assembly 4 is in axial contact with the upper end of the rubber cartridge assembly 2 .

[0083] According to the present invention, the double cylinder assembly 4 includes a first cylinder 41 and a second cylinder 42 which are coaxially arranged in sequence, and a first pressure transmission hole 12 and a second pressure transmission hole 13 which respectively connect the flow channel 11 with the first cylinder 41 and the second cylinder 42 are arranged on the side wall of the central pipe 1. When the pressure in the central pipe 1 increases, the first cylinder 41 and the second cylinder 42 of the double cylinder assembly 4 can respectively move downward through the first pressure transmission hole 12 and the second pressure transmission hole 13 in response to the pressure in the central pipe 1, thereby squeezing the rubber cylinder assembly 2, causing the rubber cylinder assembly 2 to expand radially, and the rubber cylinder assembly 2 after radial expansion can isolate the outer wall of the central pipe 1 and the inner wall of the branch wellbore 105.

[0084] According to the present invention, in a specific embodiment, the central tube 1 comprises a first tube section 14 and a second tube section 15 coaxially connected to each other. Figure 8 As shown, the first pipe section 14 is located above the second pipe section 15 , and the outer diameter of the first pipe section 14 is greater than the outer diameter of the second pipe section 15 .

[0085] The first liquid cylinder 41 includes a first large diameter portion 411 and a first small diameter portion 412 which are coaxially connected to each other. The inner diameter of the first large diameter portion 411 is larger than the inner diameter of the first small diameter portion 412, and the first large diameter portion 411 is located above the first small diameter portion 412. A first seal 61 is provided between the first large diameter portion 411 and the outer wall of the first pipe section 14 of the central tube 1, a second seal 62 is provided between the first small diameter portion 412 and the outer wall of the second pipe section 15 of the central tube 1, and the first pressure transmission hole 12 is located between the first seal 61 and the second seal 62. The pressure inside the central tube 1 can be transmitted to the upper end surface of the first small diameter portion 412 of the first liquid cylinder 41 through the first pressure transmission hole 12, so that the first liquid cylinder 41 moves downward relative to the central tube 1.

[0086] The shear pin 5 fixedly connects the first large diameter portion 411 of the first hydraulic cylinder 41 and the first pipe section 14 of the central pipe 1 .

[0087] The second liquid cylinder 42 is arranged between the first liquid cylinder 41 and the rubber cylinder assembly 2. The second liquid cylinder 42 includes a second large diameter portion 421 and a second small diameter portion 422. The inner diameter of the second small diameter portion 422 is smaller than the inner diameter of the second large diameter portion 421, and the second small diameter portion 422 is located at the lower part of the second large diameter portion 421. The second small diameter portion 422 is sealed with the outer wall of the second pipe section 15 of the central tube 1, and a sealing assembly 45 is arranged between the outer wall of the second pipe section 15 of the central tube 1 and the inner wall of the second large diameter portion 421. The second pressure transmission hole 13 is located between the sealing assembly 45 and the second small diameter portion 422. The pressure inside the central tube 1 can be transmitted to the upper end surface of the second small diameter portion 422 of the second liquid cylinder 42 through the second pressure transmission hole 13, so that the second liquid cylinder 42 moves downward relative to the central tube 1.

[0088] In a specific embodiment, both axial ends of the sealing assembly 45 are provided with limit clamping springs 44, which are clamped on the outer wall of the central tube 1, thereby fixing the sealing assembly 45 on the outer wall of the central tube 1. Through this arrangement, the sealing assembly 45 is detachably mounted on the outer wall of the central tube 1, which is easy to disassemble and provides convenience for the installation of the first liquid cylinder 41 and the second liquid cylinder 42.

[0089] According to the present invention, Fig.10 As shown, the sealing assembly 45 includes a back ring 451, a V-ring 452 and a pressure ring 453 which are sequentially arranged from the middle to both sides along the axial direction. Specifically, a plurality of V-rings 452 are arranged on both sides of the back ring 451 in the axial direction, and the openings of each V-ring 452 are all facing the back ring 451. A pressure ring 453 is arranged on the side of the V-ring 452 away from the back ring 451, and the shape of the side of the pressure ring 453 facing the V-ring 452 is adapted to the shape of the V-ring 452. The shape of the side of the pressure ring 453 away from the V-ring 452 is set to be a plane, so as to adapt and abut with the limit clamp 44.

[0090] A connecting sleeve 43 is provided between the first cylinder 41 and the second cylinder 42. The upper end of the connecting sleeve 43 is fixedly connected to the first small diameter portion 412 of the first cylinder 41 by threaded connection, and the lower end of the connecting sleeve 43 is fixedly connected to the second large diameter portion 421 of the second cylinder 42 by threaded connection. Further, both ends of the connecting sleeve 43 are respectively connected to the first small diameter portion 412 and the second large diameter portion 421 by fastening screws, thereby preventing the threads between the connecting sleeve 43 and the first small diameter portion 412 and the second large diameter portion 421 from loosening.

[0091] In a preferred embodiment, a locking ring 71 is coaxially sleeved on the central tube 1. Specifically, the locking ring 71 is arranged on the outer wall of the central tube 1 through a locking spring 72, and the upper end of the locking ring 71 is axially in contact with the lower end of the retaining ring 3, thereby fixing the retaining ring 3 on the central tube 1.

[0092] In a preferred embodiment, a retaining ring 81 is coaxially arranged outside the first pipe section 14 of the central pipe 1, and the retaining ring 81 is fixed to the central pipe 1 by a set screw 82. The lower end of the retaining ring 81 axially abuts against the upper end of the first cylinder 41 of the double cylinder assembly 4.

[0093] In this embodiment, if Fig. 9 As shown, the rubber cylinder assembly 2 includes a middle rubber cylinder 21, a spacer ring 22, a side rubber cylinder 23 and a gasket ring 24 which are arranged in sequence from the middle to both sides along the axial direction. An inner support ring 25 is arranged between the inner wall of the middle rubber cylinder 21 and the center tube 1. The axial cross-section of the middle rubber cylinder 21 is trapezoidal.

[0094] Specifically, the middle rubber tube 21 is arranged on the second pipe section 15 of the central tube 1, and a spacer ring 22 is respectively arranged at the two axial ends of the middle rubber tube 21, a side rubber tube 23 is arranged on the side of the spacer ring 22 away from the middle rubber tube 21, and a gasket ring 24 is arranged on the side of the side rubber tube 23 away from the middle rubber tube 21.

[0095] The middle rubber tube 21 and the side rubber tube 23 are made of rubber material, and the gasket 24 and the spacer ring 22 are made of metal material.

[0096] The axial cross section of the middle rubber tube 21 is configured as an isosceles trapezoid, and the axial length of the portion radially close to the central tube 1 is greater than the portion away from the central tube 1. The spacer ring 22 is configured as a cone and is adapted to the axial end surfaces of the middle rubber tube 21. The end of the side rubber tube 23 is adapted to the shape of the spacer ring 22.

[0097] Furthermore, shoulder guards 26 are provided at both axial ends of the rubber cartridge assembly 2 , and the axial ends of the shoulder guards 26 are axially abutted against the second liquid cylinder 42 and the rubber cartridge assembly 2 respectively, and the inner wall of the shoulder guards 26 is in contact with the outer wall of the second liquid cylinder 42 and the rubber cartridge assembly 2 .

[0098] According to the present invention, by applying pressure to the center pipe 1, the double cylinder assembly 4 can be pushed downward, thereby cooperating with the retaining ring 3 to axially squeeze the rubber cylinder assembly 2, causing the rubber cylinder assembly 2 to expand radially, thereby completing the sealing between the center pipe 1 and the inner wall of the branch wellbore 105.

[0099] In the description of the present invention, it should be understood that 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 technical features indicated. Thus, a feature defined as "first" or "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.

[0100] 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 a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0101] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0102] Finally, it should be noted that the above is only a preferred embodiment of the present invention and does not constitute any limitation to the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for a person skilled in the art to modify the technical solutions described in the aforementioned embodiments or to replace some of the technical features therein by equivalents. 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 branch well construction process, characterized in that: The steps include: S1. Temporarily plug the main wellbore; S2, using drilling tools to sidetrack the branch wellbore; S3. After the branch wellbore is drilled, the drilling tool is removed; S4, releasing the blockage of the main wellbore; S5. Running a curved pipe capable of supporting the well wall of the branch wellbore at the connection between the branch wellbore and the main wellbore, wherein the curved pipe includes a main well channel and a branch well channel; S6, fracturing the branch wellbore; S7. An oil pipe with an oil pipe packer is lowered into the well from the wellhead, and the lower end of the oil pipe is connected to the branch well channel of the elbow.

2. The branch well construction process according to claim 1, characterized in that: A switch sliding sleeve is provided on the oil pipe, and the switch sliding sleeve is located between the oil pipe packer and the elbow.

3. The branch well construction process according to claim 2, characterized in that: During the oil production process, when it is necessary to produce oil from the branch wellbore alone, the switch sleeve is closed; when it is necessary to produce oil from the main wellbore and the branch wellbore together, the switch sleeve is opened.

4. The branch well construction process according to claim 2 or 3, characterized in that: The switch sliding sleeve realizes switching by means of a steel wire operation.

5. The branch well construction process according to claim 1, characterized in that: In S1 , a rupture disk is placed in the main wellbore to temporarily block the main wellbore.

6. The branch well construction process according to claim 5, characterized in that: In S4, the rupture disk is fractured by pumping pressure into the well, thereby releasing the blockage of the main wellbore.

7. The branch well construction process according to claim 1, characterized in that: In the above-mentioned S2, the drilling tool includes a whipstock, which is lowered into the well and sidetracked into the branch wellbore by means of the guiding effect of the whipstock.

8. The branch well construction process according to claim 1, characterized in that: A fracturing tool string is provided on the elbow, and in S6 , the branch wellbore is fractured using the fracturing tool string.

9. The branch well construction process according to claim 8, characterized in that: The fracturing tool string includes a fracturing sleeve and a bridge plug.

10. A branch well structure manufactured according to the branch well construction process according to any one of claims 1 to 9, characterized in that: include: A bend pipe is provided at the connection between the branch wellbore and the main wellbore through a hanger, wherein the hanger is located in the main wellbore; The elbow includes a main well channel and a branch well channel, wherein the branch well channel connects the branch wellbore with the main wellbore located above the hanger, and the main well channel connects the main wellbore located above and below the hanger; and An oil pipe connected to the branch wellbore is arranged above the bend pipe. The oil pipe is arranged in the main wellbore through an oil pipe packer. The lower end of the oil pipe is connected to the branch well channel. A switch sleeve is provided on the oil pipe. The switch sleeve is located between the bend pipe and the oil pipe packer.

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