Well completion process pipe column for sidetracking well and construction method of well completion process pipe column

Abstract

The invention discloses a sidetracking well completion process pipe column and a construction method.The pipe column comprises an expansion pipe hanger assembly, a multi-stage sliding sleeve, a toe end sliding sleeve and a rubber plug seat which are coaxially arranged and sequentially connected through a sleeve from top to bottom, the expansion pipe hanger assembly comprises a central pipe and an expansion pipe, the upper end of the central pipe is provided with an upper connector and a short section, and the lower end of the central pipe is provided with a lower connector; an expansion cone, an expansion pipe connecting pipe and a lower joint are arranged at the lower end of the central pipe, and the expansion cone promotes the expansion pipe to expand in a pressurized state; a sealing sleeve is arranged at the connecting position of the expansion cone and the expansion pipe connecting pipe, and the small rubber plug assembly moves downwards in a pressurized state and pushes the large rubber plug assembly to further move. And the multi-stage sliding sleeve is fixedly connected with the lower joint. The device has a good sealing and hanging function, can realize two-way hanging, has larger hanging force and higher reliability, can achieve the purpose of multi-section transformation, and breaks through the current situation that only one layer of low-permeability reservoir sidetracking well can be mixed and pressed or fractured at present.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield completion engineering, and in particular to a side-drilling completion process pipe string and a construction method thereof. Background Art

[0002] As the oilfield enters the middle and late stages of development, the frequency of casing damage in old wells continues to increase due to various reasons. Using old wellbores for casing window side drilling has become an important means of exploiting the remaining oil in old oilfields. The Dagang Oilfield side-drills about 15-30 wells per year. 5-1 / 2" casing side-drills, hangs Φ95.25mm casing, and uses a tail pipe with an inner diameter of Φ82.25mm for cementing and completion. The first side-drilled fracturing well in the Dagang Oilfield is from 38-34K. The tail pipe of the well is hung with a φ95.25mm small casing for completion. The inner diameter of the sent-in pipe string is φ60.3mm. Only two sections and one layer of the fracturing hole are fractured, and the construction displacement is only 4.3m 3 / min, the bridge-plug combined with multi-cluster perforation volume fracturing was not achieved.

[0003] The reservoirs of Kong 2 in the southern oil area of ​​Dagang Oilfield and Sha 1 and Sha 2 in the northern oil area can all be transformed by multi-cluster perforation volume fracturing with bridge plugs in side drilling to recover the remaining oil. Due to the reasons such as the lack of diameter and low pressure of the plug-in string insertion seal and hanger and the tail pipe completion string, the bridge plug joint staged fracturing volume transformation cannot be achieved. The fracturing can only be carried out by inserting a packer to seal, single layer or multiple mixed pressure, and the bridge plug multi-cluster staged fracturing transformation cannot be achieved.

[0004] For example, in application number 202010257552.6, a side drilling well completion method is provided, in which a tail pipe suspension and tie-back integrated tool is installed on the upper part of the small diameter casing, and the small diameter casing is cemented and suspended in the original wellbore, and a tie-back tube is left on the upper part of the small diameter casing. During fracturing construction, the sealing insert can be connected to the small diameter casing and lowered into the side drilling well. The sealing insert is inserted into the tie-back tube to form a wellbore similar to a new well, thereby realizing the full diameter of the side drilling wellbore, improving the pressure bearing capacity of the entire wellbore, and creating conditions for subsequent multi-layer and section transformation and water-proof oil production in the reservoir. The tail pipe suspension and tie-back integrated tool of this invention is a conventional suspension tool with a cava. The tool is relatively complex, and the inner diameter formed after the tie-back tube is inserted is small.

[0005] Based on this, the inventors of the present application realize that there is still much room for improvement in overcoming the problem that the current side drilling of low permeability reservoirs can only mix pressure or fracture one layer.

[0006] Therefore, it is very necessary to design a side drilling well completion process string and its construction method to solve the annular space loss problem of the overlapping section of the large casing and the small casing above the side drilling well window and achieve the purpose of multi-section transformation. Summary of the invention

[0007] In order to solve the existing technical problems, the present invention proposes a side drilling completion process pipe string and a construction method thereof. The expandable pipe hanger assembly of the device can achieve a two-way suspension effect. No matter it is lifted up or lowered, the tail pipe string cannot move, thereby eliminating the damage to the upper casing caused by conventional hanger slips, and can provide greater suspension force and higher reliability. It also solves the annular space loss problem of the overlapping section of the large casing and the small casing above the side drilling window, and achieves the purpose of multi-section transformation at the same time.

[0008] According to one aspect of the present invention, a sidetrack well completion process string is provided, comprising:

[0009] The expandable pipe hanger assembly, multi-stage sliding sleeve, toe end sliding sleeve and rubber plug seat are coaxially arranged and connected by casing from top to bottom.

[0010] Wherein, the expansion tube hanger assembly comprises a center tube and an expansion tube coaxially sleeved on the outside of the center tube, the upper end of the center tube is provided with an upper joint and a short joint, the lower end of the center tube is provided with an expansion cone, an expansion tube connecting tube and a lower joint in sequence, the expansion cone causes the expansion tube to expand in a pressurized state and resets in an unpressurized state; a sealing sleeve is provided at the connection between the expansion cone and the expansion tube connecting tube, a small rubber plug assembly is provided in the expansion tube connecting tube, a large rubber plug assembly is provided in the lower joint, the small rubber plug assembly moves downward in a pressurized state, and pushes the large rubber plug assembly to further move through the multi-stage sliding sleeve and the toe end sliding sleeve until it is locked with the rubber plug seat;

[0011] The multi-stage sliding sleeve is fixedly connected to the lower joint, and the multi-stage sliding sleeve comprises a plurality of fracturing ball-throwing sliding sleeves connected in sequence by casings. The fracturing ball-throwing sliding sleeves are opened step by step after soluble balls of corresponding sizes are thrown in.

[0012] According to one embodiment of the present invention, the outside of the connection between the central pipe and the short section is sequentially sleeved with a hanging sleeve, a limiting sleeve and a connecting sleeve from top to bottom, and the limiting sleeve is connected to the expansion pipe for fixing the expansion pipe.

[0013] According to one embodiment of the present invention, an expansion cone bushing is further provided inside the expansion cone.

[0014] According to one embodiment of the present invention, the large rubber plug assembly is fixedly connected to the upper end of the lower joint by shear pins, and the shear pins can be sheared off in a pressurized state, so that the large rubber plug assembly moves downward until it is locked with the rubber plug seat.

[0015] According to one embodiment of the present invention, the outer sides of the small rubber plug assembly and the large rubber plug assembly are both provided with an inverted frustum-shaped wing ring with a wide upper opening and a narrow lower opening.

[0016] According to an embodiment of the present invention, each stage of the fracturing ball-dropping sleeve is equipped with at least one soluble ball of corresponding size.

[0017] According to another aspect of the present invention, a construction method of a sidetracking well completion process string is provided, wherein the following steps are performed based on any one of the above sidetracking well completion process strings:

[0018] S1. Connect the expansion pipe hanger assembly, multi-stage sliding sleeve, toe end sliding sleeve and rubber plug seat in sequence from top to bottom through the casing, and transport them to the expected well depth;

[0019] S2. After cementing cement is injected into the cement injection channel at the wellhead, the cement injection channel is pressurized to enter a pressurized state, thereby moving the small rubber plug assembly downward to return the cement in the well to the annulus between the cementing open hole section and the casing;

[0020] S3, continue to pump the small rubber plug assembly to the large rubber plug assembly and push the large rubber plug assembly downward to lock it with the rubber plug seat, and wait for solidification to complete the cementing operation;

[0021] S4. Use casing to connect the insert seal, cooperate with the fully expanded expansion tube seal, use the sleeve opening tool to open the toe sleeve to carry out the bottom layer fracturing operation, and after inserting the soluble ball, open the multi-stage sleeves in turn to complete each layer fracturing operation step by step from bottom to top.

[0022] According to one embodiment of the present invention, the casing of the connection insertion seal has the same specification as the casing of the cementing section.

[0023] According to one embodiment of the present invention, it also includes: after the expansion pipe is fully expanded, the upper joint, the short joint, the hanging sleeve, the limiting sleeve, the connecting sleeve, the central pipe, the expansion cone bushing, the expansion cone and the sealing sleeve are removed.

[0024] According to one embodiment of the present invention, it also includes: after completing each layer of fracturing operation, inserting the seal, leaving the expansion pipe, small plug assembly, expansion pipe connecting pipe, large plug assembly, lower joint, multi-stage sliding sleeve, toe end sliding sleeve and plug seat in the well.

[0025] Due to the adoption of the above technical solution, the present invention has the following advantages compared with the prior art:

[0026] 1. This method has good sealing and suspension functions, and the pressure difference can reach 70MPa, which completely solves the annular leakage problem of the overlapping section between the large casing and the small casing above the side drilling window, so that the overlapping section between the small casing and the large casing can be less than 10m, saving casing costs, and making the open hole liner and the large casing form a complete whole;

[0027] 2. The expansion tube hanger assembly can achieve a two-way suspension effect. Whether it is lifted up or lowered, the tail pipe string cannot move, eliminating the damage to the upper casing caused by conventional hanger slips, and can provide greater suspension force and higher reliability;

[0028] 3. The developed process string achieves the purpose of multi-stage transformation, breaking through the current situation where side drilling of low-permeability reservoirs can only be mixed pressure or fracturing one layer, realizing independent innovation and reaching the domestic leading level. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings required for use in the embodiment will be briefly introduced below. Obviously, the drawings described below are only some implementation cases of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 A schematic diagram of a sidetracking well completion process string according to an embodiment of the present invention is shown;

[0031] Figure 2 A schematic diagram showing a first part of a sidetrack well completion process string according to an embodiment of the present invention is shown;

[0032] Figure 3 A schematic diagram showing a second part of a sidetrack well completion process string according to an embodiment of the present invention is shown;

[0033] Figure 4 A schematic diagram showing a third part of a sidetrack well completion process string according to an embodiment of the present invention;

[0034] Figure 5 A process flow chart of a method for constructing a sidetrack well completion process string according to an embodiment of the present invention is shown.

[0035] The reference numerals in the figures are described as follows:

[0036] 1-upper joint; 2-short joint; 3-hanging sleeve; 4-limiting sleeve; 5-connecting sleeve; 6-center tube; 7-expansion tube; 8-expansion cone bushing; 9-expansion cone; 10-sealing sleeve; 11-small rubber plug assembly; 12-expansion tube connecting pipe; 13-large rubber plug assembly; 14-lower joint; 15-multi-stage sliding sleeve; 16-toe sliding sleeve; 17-plug seat. DETAILED DESCRIPTION

[0037] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0038] 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, rather than indicating or implying 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 limiting the present invention.

[0039] like Figure 1 As shown, the present invention provides a side drilling well completion process string, Figure 1 A schematic diagram of an exemplary sidetracking completion process string according to the present invention is shown, which specifically includes an expandable pipe hanger assembly, a multi-stage sliding sleeve 15, a toe sliding sleeve 16 and a rubber plug seat 17 which are coaxially arranged and connected by casing from top to bottom.

[0040] The expansion tube hanger assembly comprises a central tube 6 and an expansion tube 7 coaxially sleeved on the outer side of the central tube 6, an upper joint 1 and a short joint 2 are arranged at the upper end of the central tube 6, and an expansion cone 9, an expansion tube connecting pipe and a lower joint 14 are arranged in sequence at the lower end of the central tube 6, the expansion cone 9 causes the expansion tube 7 to expand in a pressurized state and resets in an unpressurized state; a sealing sleeve 10 is arranged at the connection between the expansion cone 9 and the expansion tube connecting pipe, a small rubber plug assembly 11 is arranged in the expansion tube connecting pipe, and a large rubber plug assembly 13 is arranged in the lower joint 14, the small rubber plug assembly 11 moves downward in a pressurized state, and pushes the large rubber plug assembly 13 to further move through a multi-stage sliding sleeve 15 and a toe end sliding sleeve 16 until it is locked with the rubber plug seat 17; the multi-stage sliding sleeve 15 is fixedly connected to the lower joint 14, and the multi-stage sliding sleeve 15 comprises a plurality of fracturing ball sliding sleeves connected in sequence by casings, and the fracturing ball sliding sleeve is opened step by step from bottom to top after a soluble ball of corresponding size is put into the fracturing ball sliding sleeve.

[0041] like Figure 2-4 As shown, in some embodiments, the outside of the connection between the central pipe 6 and the short section 2 is sequentially sleeved with a hanging sleeve 3, a limiting sleeve 4 and a connecting sleeve 5 from top to bottom, and the limiting sleeve 4 is connected to the expansion pipe 7 to fix the expansion pipe 7 to prevent the expansion pipe from moving up or falling, ensuring that it is in a suitable position.

[0042] In some embodiments, an expansion cone bushing 8 is further provided inside the expansion cone 9. The expansion cone bushing 8 is used for sealing and reducing wear.

[0043] On the basis of the above embodiments, the large rubber plug assembly 13 is fixedly connected to the upper end of the lower joint 14 by shear pins, which can be sheared off in the pressurized state, so that the large rubber plug assembly 13 moves downward until it is locked with the rubber plug seat 17.

[0044] In some embodiments, the outer sides of the small rubber plug assembly 11 and the large rubber plug assembly 13 are provided with an inverted cone-shaped wing ring with a wide upper opening and a narrow lower opening. The setting of the wing ring enables the small rubber plug assembly 11 and the large rubber plug assembly 13 to maintain good sealing performance.

[0045] Each stage of the fracturing ball-throwing sliding sleeve is equipped with at least one soluble ball of corresponding size.

[0046] like Figure 5 As shown, the present invention also provides a method for constructing a side drilling well completion process pipe string, which specifically includes the following steps:

[0047] S1, connect the expansion tube 7 hanger assembly, the multi-stage sliding sleeve 15, the toe end sliding sleeve 16 and the rubber plug seat 17 from top to bottom in sequence through the casing, and transport them to the expected well depth;

[0048] S2, after injecting cement for cementing into the cement injection channel at the wellhead, pressurizing the cement injection channel to enter a pressurized state, thereby moving the small rubber plug assembly 11 downward, so that the cement in the well returns to the annulus between the cementing open hole section and the casing;

[0049] S3, continue to pressurize to pump the small rubber plug assembly 11 to the large rubber plug assembly 13 and push the large rubber plug assembly 13 downward to lock it with the rubber plug seat 17, and wait for solidification to complete the cementing operation;

[0050] S4. Use casing to connect the insert seal, and seal with the fully expanded expansion tube 7. Use the sleeve opening tool to open the toe sleeve 16 to perform the bottom layer fracturing operation. After the soluble ball is put in, open the multi-stage sleeves 15 in turn to complete the fracturing operation of each layer.

[0051] According to some embodiments, the casing of the connection insertion seal has the same specification as the casing of the cementing section.

[0052] In some embodiments, the method further includes: after the expansion pipe 7 is fully expanded, removing the upper joint 1, the short joint 2, the suspension sleeve 3, the limiting sleeve 4, the connecting sleeve 5, the center pipe 6, the expansion cone bushing 8, the expansion cone 9 and the sealing sleeve 10.

[0053] In some embodiments, the method further includes: after completing each layer of fracturing operation, removing the inserted seal, leaving the expansion tube 7, the small rubber plug assembly 11, the expansion tube 7 connecting pipe, the large rubber plug assembly 13, the lower joint 14, the multi-stage sliding sleeve 15, the toe end sliding sleeve 16 and the rubber plug seat 17 in the well.

[0054] The sidetracking well completion process string and construction method of the present invention are described in detail below through a specific embodiment.

[0055] refer to Figures 1 to 4 A side drilling completion process pipe string consists of an expansion tube hanger assembly, a multi-stage sliding sleeve 15, a toe end sliding sleeve 16, and a rubber plug seat 17; wherein the expansion tube hanger assembly consists of an upper joint 1, a short joint 2, a hanging sleeve 3, a limit sleeve 4, a connecting sleeve 5, a central pipe 6, an expansion tube 7, an expansion cone bushing 8, an expansion cone 9, a sealing sleeve 10, a small rubber plug assembly 11, an expansion tube connecting pipe, a large rubber plug assembly 13, and a lower joint 14; the multi-stage sliding sleeve 15 includes a plurality of fracturing ball sliding sleeves, and casing is connected between the plurality of fracturing ball sliding sleeves; the expansion tube hanger assembly, the multi-stage sliding sleeve 15, the toe end sliding sleeve 16, and the rubber plug seat 17 are connected from top to bottom by casing.

[0056] During use, the expansion tube hanger assembly is installed according to the structure, and the expansion tube hanger assembly, multi-stage sliding sleeve 15, toe end sliding sleeve 16, and plug seat 17 are transported to the expected well depth by 2 7 / 8TBG oil pipe, and the pipe string is suspended at the wellhead; after cementing cement is injected into the wellhead, the small plug assembly 11 is put in, and the small plug assembly 11 is pushed downward by the ground pump truck, and the cement in the well returns to the annulus between the cementing open hole section and the casing; when the small plug assembly 11 is pumped to the large plug assembly 13, the shear nails fixing the large plug assembly 13 are continuously pressed to cut off, and the large plug assembly 13 is pushed downward until it is locked with the plug seat 17, and the cementing operation is completed by waiting for solidification; the pipe string is pressed, and the expansion cone 9 starts to expand the expansion tube 7 under the action of hydraulic pressure. When all the expansion is completed, the upper joint 1, the short joint 2, the suspension sleeve 3, the limit sleeve 4, the connecting sleeve 5, the central pipe 6, the expansion cone bushing 8, the expansion cone 9, and the sealing sleeve 10 are pulled out,

[0057] A casing of the same specification as the casing of the cementing section is used to connect the insert seal, which is transported to the expansion pipe 7, and the insert seal is matched with the expansion pipe 7 seal; the surface is pressurized to open the toe end sliding sleeve 16, and the bottom layer is started to be fractured;

[0058] Soluble balls of corresponding sizes are sequentially put in, the multi-stage sliding sleeves 15 are opened in sequence, and the fracturing operation of each layer is completed step by step from bottom to top;

[0059] An insert seal connected to a casing of the same specification as the cementing section casing is proposed, and the expansion pipe 7, the small rubber plug assembly 11, the expansion pipe 7 connecting pipe, the large rubber plug assembly 13, the lower joint 14, the multi-stage sliding sleeve 15, the toe end sliding sleeve 16, and the rubber plug seat 17 remain in the well.

[0060] The method steps of the present invention are further explained below in conjunction with specific embodiments. Figure 1 The process column shown in the figure includes the following specific implementation steps:

[0061] Step 1: Install the expansion pipe 7 hanger assembly according to the structure, use 2 7 / 8TBG oil pipe to transport the expansion pipe 7 hanger assembly, multi-stage sliding sleeve 15, toe end sliding sleeve 16, and rubber plug seat 17 to the expected well depth, and hang the pipe string at the wellhead;

[0062] Step 2: After cementing is injected into the pipe string, a small rubber plug assembly 11 is put in, and the small rubber plug assembly 11 is pushed downward by a pump truck on the ground, and the cement in the well returns to the annulus between the cementing open hole section and the casing;

[0063] Step 3: When the small rubber plug assembly 11 is pumped to the large rubber plug assembly 13, continue to pressurize and cut off the shear pins fixing the large rubber plug assembly 13, and start to push the large rubber plug assembly 13 downward until it is locked with the rubber plug seat 17, and wait for solidification to complete the cementing operation;

[0064] Step 4, pressurize the pipe string, and the expansion cone 9 starts to expand the expansion pipe 7 under the action of hydraulic pressure. When all the expansion is completed, the upper joint 1, the short joint 2, the hanging sleeve 3, the limit sleeve 4, the connecting sleeve 5, the center pipe 6, the expansion cone bushing 8, the expansion cone 9 and the sealing sleeve 10 are taken out;

[0065] Step 5: Connect the insert seal with a casing of the same specification as the casing of the cementing section, transport it to the expansion pipe 7, and the insert seal is sealed and matched with the expansion pipe 7;

[0066] Step 6: Pressurize the surface to open the toe end sliding sleeve 16 and start fracturing the bottom layer;

[0067] Step 7: Throw in soluble balls, open the multi-stage sliding sleeves 15 in sequence, and complete the fracturing operation of each layer step by step from bottom to top;

[0068] Step 8, bring out the insert seal connected to the casing of the same specification as the cementing section casing, and leave the expansion pipe 7, small rubber plug assembly 11, expansion pipe 7 connecting pipe, large rubber plug assembly 13, lower joint 14, multi-stage sliding sleeve 15, toe end sliding sleeve 16 and rubber plug seat 17 in the well.

[0069] In a side drilling completion process string and construction method according to an embodiment of the present invention, on the basis of the prior art, a 51 / 2" side drilling bridge plug-linked multi-cluster segmented fracturing completion string is formed for a low permeability reservoir, and a bridge plug cable perforation-linked fracturing completion string or a cementing ball-dropping sliding sleeve fracturing completion string is put into an 82.25mm inner diameter tail pipe, which effectively reduces the perforation operation, thereby reducing the damage to the production layer, and achieving economic effects such as fast production and low cost.

[0070] Compared with the prior art, the present invention has the following advantages:

[0071] 1. This method has good sealing and suspension functions, and the pressure difference can reach 70MPa, which completely solves the annular leakage problem of the overlapping section between the large casing and the small casing above the side drilling window, so that the overlapping section between the small casing and the large casing can be less than 10m, saving casing costs, and making the open hole liner and the large casing form a complete whole;

[0072] 2. The expansion pipe hanger assembly can achieve a two-way suspension effect. Whether it is lifted up or lowered, the tail pipe string cannot move. It eliminates the damage to the upper casing caused by conventional hanger slips and can provide greater suspension force and higher reliability;

[0073] 3. The developed process string achieves the purpose of multi-stage transformation, breaking through the current situation where side drilling of low-permeability reservoirs can only be mixed pressure or fracturing one layer, realizing independent innovation and reaching the domestic leading level.

[0074] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the embodiments of the present invention as above, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A side drilling well completion process string, characterized in that: include: The expandable pipe hanger assembly, multi-stage sliding sleeve, toe end sliding sleeve and rubber plug seat are coaxially arranged and connected by casing from top to bottom. Wherein, the expansion tube hanger assembly comprises a center tube and an expansion tube coaxially sleeved on the outside of the center tube, the upper end of the center tube is provided with an upper joint and a short joint, the lower end of the center tube is provided with an expansion cone, an expansion tube connecting tube and a lower joint in sequence, the expansion cone causes the expansion tube to expand in a pressurized state and resets in an unpressurized state; a sealing sleeve is provided at the connection between the expansion cone and the expansion tube connecting tube, a small rubber plug assembly is provided in the expansion tube connecting tube, a large rubber plug assembly is provided in the lower joint, the small rubber plug assembly moves downward in a pressurized state, and pushes the large rubber plug assembly to further move through the multi-stage sliding sleeve and the toe end sliding sleeve until it is locked with the rubber plug seat; The multi-stage sliding sleeve is fixedly connected to the lower joint, and the multi-stage sliding sleeve comprises a plurality of fracturing ball-throwing sliding sleeves connected in sequence by casings. The fracturing ball-throwing sliding sleeves are opened step by step after soluble balls of corresponding sizes are thrown in.

2. The side drilling well completion process string according to claim 1, characterized in that: The outside of the connection between the central pipe and the short section is sequentially sleeved with a hanging sleeve, a limiting sleeve and a connecting sleeve from top to bottom, and the limiting sleeve is connected to the expansion pipe for fixing the expansion pipe.

3. The side drilling well completion process string according to claim 1, characterized in that: An expansion cone bushing is further arranged inside the expansion cone.

4. The side drilling well completion process string according to claim 3, characterized in that: The large rubber plug assembly is fixedly connected to the upper end of the lower joint by shear pins, and the shear pins can be sheared off in a pressurized state, so that the large rubber plug assembly moves downward until it is locked with the rubber plug seat.

5. The side drilling well completion process string according to claim 1, characterized in that: The outer sides of the small rubber plug assembly and the large rubber plug assembly are both provided with an inverted frustum-shaped wing ring with a wide upper opening and a narrow lower opening.

6. The sidetrack well completion process string according to claim 1, characterized in that: Each stage of the fracturing ball-throwing sliding sleeve is equipped with at least one soluble ball of corresponding size.

7. A method for constructing a side drilling well completion process string, characterized in that: The method comprises performing the following steps based on the sidetrack well completion process string according to any one of claims 1 to 6: S1. Connect the expansion pipe hanger assembly, multi-stage sliding sleeve, toe end sliding sleeve and rubber plug seat in sequence from top to bottom through the casing, and transport them to the expected well depth; S2. After cementing cement is injected into the cement injection channel at the wellhead, the cement injection channel is pressurized to enter a pressurized state, thereby moving the small rubber plug assembly downward to return the cement in the well to the annulus between the cementing open hole section and the casing; S3, continue to pump the small rubber plug assembly to the large rubber plug assembly and push the large rubber plug assembly downward to lock it with the rubber plug seat, and wait for solidification to complete the cementing operation; S4. Use casing to connect the insert seal, cooperate with the fully expanded expansion tube seal, use the sleeve opening tool to open the toe sleeve to carry out the bottom layer fracturing operation, and after inserting the soluble ball, open the multi-stage sleeves in turn to complete each layer fracturing operation step by step from bottom to top.

8. The method for constructing a side-drilling well completion process string according to claim 7, characterized in that: The casing for connecting, inserting and sealing is of the same specification as the casing of the cementing section.

9. The method for constructing a side-drilling well completion process string according to claim 7, characterized in that: Also includes: After the expansion pipe is fully expanded, the upper joint, the short joint, the hanging sleeve, the limiting sleeve, the connecting sleeve, the central pipe, the expansion cone bushing, the expansion cone and the sealing sleeve are removed.

10. The method for constructing a sidetrack well completion process string according to claim 7, characterized in that: Also includes: After completing each layer of fracturing operation, the inserted seal is removed, and the expansion pipe, small rubber plug assembly, expansion pipe connecting pipe, large rubber plug assembly, lower joint, multi-stage sliding sleeve, toe end sliding sleeve and rubber plug seat are left in the well.

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