Open hole packer and multilateral well construction technology

Abstract

The invention belongs to the technical field of oil and gas drilling, and particularly relates to an open hole packer and a branch well construction technology. The open hole packer comprises a central pipe, a flow channel, an open hole packer and an open hole packer, wherein the central pipe is internally and coaxially provided with the flow channel; the baffle ring is arranged on the outer side of the central pipe; the double-hydraulic-cylinder assembly is arranged on the outer side of the central pipe through a shear pin, the double-hydraulic-cylinder assembly comprises a first hydraulic cylinder and a second hydraulic cylinder which are coaxially arranged in sequence, and a first pressure transmission hole and a second pressure transmission hole which are used for communicating the flow channel with the first hydraulic cylinder and the second hydraulic cylinder respectively are formed in the side wall of the central pipe; the rubber barrel assembly is arranged on the outer side of the central pipe and located between the baffle ring and the double-hydraulic-cylinder assembly; the double-hydraulic-cylinder assembly is constructed to be capable of responding to the pressure in the flow channel of the center pipe to move towards the baffle ring, so that the rubber sleeve assembly is extruded, and the rubber sleeve assembly expands in the radial direction.

Description

Technical Field

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

[0002] With the development of oil exploration and development, and the objective demand for cost reduction and consumption reduction, oil exploration and development is moving towards rapid development, quality improvement and efficiency enhancement.

[0003] As an extension and development of horizontal well technology, branch well technology can not only increase the oil leakage area of ​​a single well, but also effectively tap the potential of remaining oil, improve the recovery rate, and further improve the development effect of oil fields. It has become an advanced technology for oil and gas field development. However, there are technical difficulties in connecting the main wellbore and the branch wellbore during the completion of branch wells. In addition, the conventional bridge plug perforation combined staged fracturing method requires multiple trips of the pipe string, which has a long construction period and high construction cost, and does not meet the current exploration and development needs.

[0004] In view of the above problems, in accordance with the objective demand for efficient, economical and safe development, it is urgent to develop a branch well construction process that can simplify the fracturing process and an open hole packer suitable for the fracturing process in the branch well construction process. Summary of the invention

[0005] In view of the above-mentioned technical problems, the present invention aims to provide an open hole packer, which can solve at least one of the above-mentioned technical problems.

[0006] The present invention also proposes a branch well construction process, which can solve at least one of the above technical problems.

[0007] According to the present invention, there is provided an open hole packer, comprising:

[0008] a central tube, wherein a flow channel is coaxially disposed in the central tube;

[0009] A retaining ring disposed outside the central tube;

[0010] A double cylinder assembly is arranged outside the central tube through a shear pin, the double cylinder assembly comprises a first cylinder and a second cylinder which are arranged coaxially in sequence, and a first pressure transmission hole and a second pressure transmission hole are arranged on the side wall of the central tube to connect the flow channel with the first cylinder and the second cylinder respectively;

[0011] A rubber cylinder assembly is arranged outside the central tube, and the rubber cylinder assembly is located between the retaining ring and the double cylinder assembly;

[0012] The double cylinder assembly is configured to move toward the retaining ring in response to the pressure in the flow channel of the central tube, thereby squeezing the rubber cartridge assembly to cause the rubber cartridge assembly to expand radially.

[0013] In a specific embodiment, the second liquid cylinder is arranged between the first liquid cylinder and the rubber cylinder assembly, the second liquid cylinder includes a second large diameter portion and a second small diameter portion, the inner diameter of the second small diameter portion is smaller than the inner diameter of the second large diameter portion, the second small diameter portion is sealed with the outer wall of the center tube, a sealing assembly is arranged on the outer wall of the center tube through a limiting retaining spring, the sealing assembly seals the inner wall of the second large diameter portion with the outer wall of the center tube, and the second pressure transmission hole is located between the sealing assembly and the second small diameter portion.

[0014] In a specific embodiment, the sealing assembly includes a back ring, a V-ring and a pressure ring which are sequentially arranged from the middle to both sides along the axial direction, and the opening of the V-ring faces the back ring.

[0015] In a specific embodiment, the shear pins fixedly connect the first hydraulic cylinder and the central tube, and the first hydraulic cylinder and the second hydraulic cylinder are fixedly connected via a connecting sleeve.

[0016] In a specific embodiment, the first liquid cylinder includes a first large diameter portion and a first small diameter portion, the inner diameter of the first large diameter portion is larger than the inner diameter of the first small diameter portion, the two ends of the connecting sleeve are respectively connected to the first small diameter portion and the second large diameter portion by fastening screws, a first seal is provided between the first large diameter portion and the outer wall of the center tube, a second seal is provided between the first small diameter portion and the outer wall of the center tube, and the first pressure transmission hole is located between the first seal and the second seal.

[0017] In a specific embodiment, the rubber cylinder assembly includes a middle rubber cylinder, a spacer ring, a side rubber cylinder and a gasket ring arranged in sequence from the middle to both sides along the axial direction, an inner support ring is arranged between the inner wall of the middle rubber cylinder and the center tube, and the axial cross-section of the middle rubber cylinder is trapezoidal.

[0018] In a specific embodiment, a locking ring is provided on the outer side of the central tube via a locking clamp spring, and the locking ring axially abuts against the end of the retaining ring away from the rubber cartridge assembly.

[0019] In a specific embodiment, a retaining ring is arranged on the outer side of the central tube, and the retaining ring axially abuts against the end of the double-cylinder assembly away from the rubber cartridge assembly.

[0020] According to the present invention, a branch well construction process is also provided, comprising the following steps:

[0021] S1. Temporarily plug the main wellbore;

[0022] S2, lowering a whipstock into the main wellbore, and using a drilling tool to side-drill a branch wellbore under the action of the whipstock;

[0023] S3. After the branch wellbore is drilled, the drilling tool is removed;

[0024] S4, using an oil pipe to lower a fracturing string into the branch wellbore for fracturing, the fracturing string comprising an open hole packer provided by the present invention, and after fracturing is completed, the oil pipe and the fracturing string are released;

[0025] S5, taking out the whipstock, releasing the temporary blockage of the main wellbore, and lowering the production tubing into the main wellbore.

[0026] In a specific embodiment, the production tubing includes an oil pipe and an oil pipe packer arranged on the oil pipe, the oil pipe packer is located above the branch wellbore, and a switch sleeve is arranged on the oil pipe, and the switch sleeve is constructed to be able to connect the branch wellbore with the interior of the oil pipe.

[0027] Compared with the prior art, the advantages of the present application are as follows.

[0028] After the branch wellbore is drilled, the fracturing string is sent into the branch wellbore using an oil pipe. The open hole packer in the fracturing string can isolate the open hole of the branch wellbore, and then the staged fracturing operation is carried out. The operation steps are simple and there is no need to trip the string multiple times.

[0029] After the fracturing operation, the oil pipe, running tools, and the whipstock and anchor in the main wellbore are taken out and salvaged. The production string is lowered into the main wellbore. The main wellbore and branch wellbore are produced separately and together by opening and closing the switch sleeve, which effectively solves the technical problem of connecting the main wellbore and the branch wellbore.

[0030] After the branch wellbore is fracturing, the production tubing is lowered into the main wellbore without affecting the diameter of the branch wellbore, thereby achieving the full diameter of the tubing after fracturing the branch wellbore without affecting subsequent construction operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be described below with reference to the accompanying drawings.

[0032] Figure 1 A schematic diagram of an embodiment of a main wellbore;

[0033] Figure 2 A schematic diagram of an embodiment of using a rupture disk to temporarily plug a main wellbore;

[0034] Figure 3 A schematic diagram of an embodiment of running a whipstock and side-drilling a branch well;

[0035] Figure 4 A schematic diagram of an embodiment of running a fracturing string;

[0036] Figure 5This is a schematic diagram of the oil pipe used for running into the fracturing string after it is lost;

[0037] Figure 6 A schematic diagram of an embodiment for removing a whipstock;

[0038] Figure 7 A schematic diagram of an embodiment of running a production string;

[0039] Figure 8 is a schematic diagram of an embodiment of an open hole packer;

[0040] Fig. 9 is a schematic diagram of an embodiment of a rubber cartridge assembly;

[0041] Fig.10 A schematic diagram of an embodiment of a sealing assembly.

[0042] The reference numerals in the figures are as follows:

[0043] 1. Central tube; 11. Flow channel; 12. First pressure transmission hole; 13. Second pressure transmission hole; 14. First pipe section; 15. Second pipe section;

[0044] 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;

[0045] 3. Retaining ring;

[0046] 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;

[0047] 5. Shear pins;

[0048] 61. a first sealing member; 62. a second sealing member;

[0049] 71. Locking ring; 72. Locking circlip;

[0050] 81. retaining ring; 82. set screw;

[0051] 10. Open hole packer;

[0052] 101. Main wellbore; 102. Rupture disk; 201. Rupture disk packer; 103. Whipstock; 104. Drilling tool; 105. Branch wellbore; 106. First oil pipe; 107. Second oil pipe; 108. Oil pipe packer; 109. Fracturing string; 100. Switch sleeve.

[0053] 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

[0054] The present invention will be described below with reference to the accompanying drawings.

[0055] 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 and Figure 8 They are not intended to define the absolute positions of the components involved, but may vary depending on the specific circumstances.

[0056] According to the present invention, a branch well construction process is provided, comprising the following steps.

[0057] S1. Temporarily block the main wellbore. Figure 1 Schematic diagram of the structure of the main wellbore 101 in this embodiment. 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, side-drilling branch wellbore 105. Figure 3 As shown, in this embodiment, the whipstock 103 is first lowered into the main wellbore 101, 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 lowered 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, and the drilling tool 104 performs side drilling of the branch wellbore 105 under the guidance of the whipstock 103.

[0059] S3. After the branch wellbore 105 is drilled, the drilling tool 104 is removed.

[0060] S4. Insert the fracturing string 109 into the branch wellbore 105 for fracturing.

[0061] like Figure 4As shown, in this embodiment, the fracturing string 109 is connected to the lower end of the first oil pipe 106 through a hand-dropping tool. The fracturing string 109 includes a plurality of open hole packers 10 and fracturing sleeves that are alternately arranged in sequence along the axial direction. During the fracturing process, the lower end of the fracturing string 109 is blocked by throwing a ball or other means, and the pressure is held in the fracturing string 109 through the first oil pipe 106 to start the open hole packer 10, so that the open hole packer 10 can isolate the annulus between the fracturing string 109 and the branch wellbore 105. Then, the pressure holding balls that are compatible with each fracturing sleeve in the fracturing string 109 are sequentially thrown in through the first oil pipe 106 and the pressure is held, and each fracturing sleeve is opened and fractured in sequence.

[0062] After the fracturing is completed, the first oil pipe 106 is separated from the fracturing string 109 and the first oil pipe 106 is lifted out of the well. Figure 5 shown.

[0063] S5 , taking out the whipstock 103 , releasing the temporary blockage of the main wellbore 101 , and lowering a production string into the main wellbore 101 .

[0064] like Figure 6 As shown, the whipstock 103 is removed by using a whipstock removal tool. It is easy to understand that the whipstock removal tool is well known to those skilled in the art and will not be described in detail herein.

[0065] After taking out the whipstock 103, Figure 7 As shown, the production string is lowered into the main wellbore 101. Specifically, the production string includes a second oil pipe 107 and an oil pipe packer 108, and the oil pipe packer 108 is located above the branch wellbore 105. A switch sleeve 100 is provided on the second oil pipe 107, and the switch sleeve 100 is located below the oil pipe packer 108. When the switch sleeve 100 is opened, the branch wellbore 105 can be connected with the inside of the second oil pipe 107, thereby realizing the combined production of the main wellbore and the branch wellbore. When the switch sleeve 100 is closed, the branch wellbore 105 cannot enter the second oil pipe 107, thereby realizing the single production of the main wellbore.

[0066] In this embodiment, the tubing packer 108 has an anchoring and sealing function.

[0067] In this embodiment, the switch sleeve 100 realizes switching by wire operation.

[0068] It should be noted that the specific structures of the rupture disk 102, rupture disk packer 201, whipstock 103, drilling tool 104, tubing packer 108, fracturing string 109, and switch sleeve 100 in this embodiment are well known to those skilled in the art and will not be described in detail herein.

[0069] According to the present invention, there is provided an open hole packer 10, such as Figure 8As shown, it mainly includes a central tube 1, a retaining ring 3, a double-liquid cylinder assembly 4 and a rubber cartridge assembly 2.

[0070] 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.

[0071] 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.

[0072] 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 .

[0073] 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 .

[0074] 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.

[0075] 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 .

[0076] 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.

[0077] 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 .

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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 .

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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. An open hole packer, characterized in that: include: A central tube (1), wherein a flow channel (11) is coaxially arranged in the central tube (1); A retaining ring (3) arranged on the outside of the central tube (1); A double cylinder assembly (4) is arranged on the outside of the central tube (1) via a shear pin (5), the double cylinder assembly (4) comprising 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) are arranged on the side wall of the central tube (1) for connecting the flow channel (11) with the first cylinder (41) and the second cylinder (42) respectively; A rubber cartridge assembly (2) arranged outside the central tube (1), the rubber cartridge assembly (2) being located between the retaining ring (3) and the double-liquid cylinder assembly (4); The double cylinder assembly (4) is constructed to be able to move toward the retaining ring (3) in response to the pressure in the flow channel (11) of the central tube (1), thereby squeezing the rubber cartridge assembly (2) and causing the rubber cartridge assembly (2) to expand radially.

2. The open hole packer according to claim 1, characterized in that: The second liquid cylinder (42) is arranged between the first liquid cylinder (41) and the rubber cylinder assembly (2), and 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). The second small diameter portion (422) is sealed with the outer wall of the center tube (1). A sealing assembly (45) is arranged on the outer wall of the center tube (1) through a limiting retaining spring (44). The sealing assembly (45) seals the inner wall of the second large diameter portion (421) with the outer wall of the center tube (1). The second pressure transmission hole (13) is located between the sealing assembly (45) and the second small diameter portion (422).

3. The open hole packer according to claim 2, characterized in that: The sealing assembly (45) comprises a back ring (451), a V-shaped ring (452) and a pressure ring (453) which are arranged in sequence from the middle to both sides along the axial direction, and the opening of the V-shaped ring (452) faces the back ring (451).

4. The open hole packer according to claim 2, characterized in that: The shear pin (5) fixedly connects the first hydraulic cylinder (41) and the central tube (1), and the first hydraulic cylinder (41) and the second hydraulic cylinder (42) are fixedly connected via a connecting sleeve (43).

5. The open hole packer according to claim 4, characterized in that: The first liquid cylinder (41) comprises a first large diameter portion (411) and a first small diameter portion (412); the inner diameter of the first large diameter portion (411) is larger than the inner diameter of the first small diameter portion (412); the two ends of the connecting sleeve (43) are respectively connected to the first small diameter portion (412) and the second large diameter portion (421) by means of fastening screws; a first sealing member (61) is provided between the first large diameter portion (411) and the outer wall of the center tube (1); a second sealing member (62) is provided between the first small diameter portion (412) and the outer wall of the center tube (1); and the first pressure transmission hole (12) is located between the first sealing member (61) and the second sealing member (62).

6. The open hole packer according to any one of claims 1 to 5, characterized in that: The rubber cylinder assembly (2) comprises 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 the two sides along the axial direction. An inner support ring (25) is arranged between the inner wall of the middle rubber cylinder (21) and the central tube (1). The axial cross section of the middle rubber cylinder (21) is constructed in a trapezoidal shape.

7. The open hole packer according to any one of claims 1 to 5, characterized in that: A locking ring (71) is provided on the outer side of the central tube (1) via a locking spring (72), and the locking ring (71) axially abuts against the end of the retaining ring (3) away from the rubber cylinder assembly (2).

8. The open hole packer according to any one of claims 1 to 5, characterized in that: A retaining ring (81) is arranged on the outer side of the central tube (1), and the retaining ring (81) axially abuts against the end of the double cylinder assembly (4) away from the rubber cylinder assembly (2).

9. A branch well construction process, characterized in that: The steps include: S1. Temporarily plug the main wellbore; S2, lowering a whipstock into the main wellbore, and using a drilling tool to side-drill a branch wellbore under the action of the whipstock; S3. After the branch wellbore is drilled, the drilling tool is removed; S4, using an oil pipe to lower a fracturing string into the branch wellbore for fracturing, wherein the fracturing string comprises an open hole packer according to any one of claims 1 to 8, and after fracturing is completed, the oil pipe and the fracturing string are released; S5, taking out the whipstock, releasing the temporary blockage of the main wellbore, and lowering the production tubing into the main wellbore.

10. The branch well construction process according to claim 9, characterized in that: The production tubing string includes an oil pipe and an oil pipe packer arranged on the oil pipe, the oil pipe packer is located above the branch wellbore, and a switch sleeve is arranged on the oil pipe, and the switch sleeve is configured to connect the branch wellbore with the inside of the oil pipe.

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