Horizontal well shaft completion pipe string and reconstruction method

Abstract

The invention relates to the technical field of oil field fracturing operation, and provides a horizontal well shaft completion pipe string and a reconstruction method.The horizontal well shaft completion pipe string comprises an original casing pipe, an inner casing pipe, a suspension packer, a shearing ball seat, a float collar, a float shoe and a plurality of composite metal pipe outer packers.The suspension packer is connected to one end of the inner casing pipe, and the shearing ball seat, the float collar and the float shoe are sequentially connected to the other end of the inner casing pipe; a plurality of composite metal pipe outer packers are sequentially arranged on the inner casing pipe at intervals and used for blocking an annular space between the original casing pipe and the inner casing pipe and forming a plurality of fracturing sections, the inner drift diameter of a reconstructed new shaft is large, large-displacement and high-pressure fracturing construction can be met, the construction cost is reduced, the repeated transformation efficiency of an old well reservoir is improved, and the construction period is shortened. And in the later period, the original gas production section can be ejected to implement commingling production, and the oil-gas output efficiency is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield fracturing operations, and more particularly, to a horizontal wellbore completion string and a reconstruction method thereof. Background Art

[0002] In the later stage of oil and gas well production, the production decline rate accelerates, the water cut increases significantly, and problems such as casing corrosion and deformation frequently occur. In addition, due to factors such as large spacing between hydraulic fracturing segmented perforation fractures, small construction scale, and unreasonable fracturing design in the early stage, a large number of oil and gas wells have been shut down. Therefore, in order to restore the productivity of old wells and extend the life cycle of oil and gas wells, it is necessary to carry out repeated fracturing on horizontal wells. After investigation, the domestic and foreign repeated fracturing technologies for horizontal wells mainly involve chemical temporary plugging, mechanical isolation, and wellbore reconstruction. Among them, the chemical temporary plugging diversion technology uses a temporary plugging agent to block the formation fractures to achieve diversion, but it is easily affected by environmental factors such as tectonic stress and wellbore fluid flow pattern; the mechanical isolation technology includes three types: double-packing and single-sliding of tubing, packer group with liner, and non-moving string of hydraulic jetting, but all of them have problems such as limited construction displacement, high pressure requirements for pressure-bearing operations, and high risks; the wellbore reconstruction technology includes chemical plugging, expansion pipe subsidy, and sleeve-in-sleeve. Among them, the chemical plugging technology uses degradable cellulose, etc. to plug the original perforation holes. Although the internal diameter of the wellbore remains unchanged, the plugging reliability is poor, the pressure-bearing capacity is low, and the cost is high; the expansion pipe subsidy technology uses the principle of expansion of the expansion pipe to plug the holes on the original casing wall and then perform fracturing, but this technology has complex processes and high requirements for plugging long horizontal sections, and the actual application cost is high and the effect is not significant; the sleeve-in-sleeve technology is to lower a small oil / casing into the original casing to construct a new wellbore, but the current small casing has a small internal diameter and the annulus is mostly filled with cement slurry, resin, etc., resulting in a low pressure-bearing capacity of the new wellbore and a small fracturing scale. Therefore, a horizontal wellbore reconstruction repeated fracturing technology and a completion string that can meet the requirements of large internal diameter, large displacement, and high pressure construction are needed. Summary of the Invention

[0003] The first object of the present invention is to provide a horizontal wellbore completion string. The reconstructed new wellbore has a large internal diameter, which can meet the requirements of large displacement and high pressure fracturing construction, reduce the construction cost, improve the efficiency of repeated reservoir reconstruction of old wells, and can also perforate the original gas production section for combined production in the later stage to further improve the oil and gas production efficiency.

[0004] The second object of the present invention is to provide a reconstruction method for a horizontal wellbore completion string. This method can make the reconstructed new wellbore have a large internal diameter, ensure reducing the frictional resistance during the construction process, realize large displacement and high pressure repeated fracturing construction, while reducing the construction cost, greatly improving the efficiency of repeated reservoir reconstruction of old wells, and further increasing the oil and gas production.

[0005] To solve the above technical problems, the technical solution adopted in the present application is as follows:

[0006] In a first aspect, an embodiment of the present application provides a completion string for a horizontal wellbore, which includes an original casing, an inner casing, a hanging packer, a shear ball seat, a float collar, a float shoe, and a plurality of composite metal pipe external packers. The inner casing is located inside the original casing. One end of the inner casing is connected with a hanging packer, and the hanging packer is used to hang and fix the inner casing at the wellhead. The other end of the inner casing is sequentially connected with a shear ball seat, a float collar, and a float shoe. The shear ball seat is located inside the original casing and is used to cooperate with a resin ball to block the lower end of the inner casing. Both the float collar and the float shoe are located inside the original casing and are used to guide the lowering of the inner casing and prevent backflow. The plurality of composite metal pipe external packers are sequentially and spacedly connected with the inner casing and are used to block the annulus between the original casing and the inner casing and form a plurality of fracturing sections.

[0007] In the prior art, the technology of fixing the casing in the oilfield casing mainly uses a 3.5-inch inner casing. However, this specification of the inner casing cannot meet the construction requirements of large displacement and high pressure. Simply increasing the inner diameter of the inner casing cannot ensure smooth construction. There is an annular gap between the inner casing and the original casing, and it is necessary to ensure the annular seal during construction. In the prior art, materials such as resin curing agents, cement slurries, and ordinary packers are often used to block the annulus, but they have problems such as poor sealing effect and low pressure bearing capacity. Therefore, in the present application, a composite metal pipe external packer is proposed, which can meet the smooth implementation of the construction of the inner casing with a large inner diameter, and at the same time has an excellent sealing effect and high pressure bearing capacity compared with the prior art, meets the construction requirements of large displacement and high pressure, and does not require cementing, simplifies the wellbore reconstruction steps, and reduces the construction cost.

[0008] In some embodiments of the present invention, the shear ball seat is threadedly connected to the lower end of the inner casing. One end of the float collar is threadedly connected to the shear ball seat, and the other end is threadedly connected to the float shoe.

[0009] In some embodiments of the present invention, the composite metal pipe external packer includes a rubber cylinder and two metal bodies. The two metal bodies are respectively fixedly connected to both ends of the rubber cylinder. After the rubber cylinder expands, it has an interference fit with the inner wall of the original casing. Both metal bodies are also threadedly connected to the inner casing.

[0010] In some embodiments of the present invention, the outer diameter of the above-mentioned outer casing is 139.7 mm, and the inner diameter is 124.6 mm; the outer diameter of the inner casing is 114.3 mm, and the inner diameter is 98 mm; the outer diameter of the composite metal pipe external packer is 116 mm, and the inner diameter is 98 mm. Most of the original casing of the old wellbore to be reconstructed is 139.7 mm. The present application further defines the sizes of the inner casing and the composite metal pipe external packer for the original casing of this size to achieve the optimal implementation effect. However, it should be noted that the composite metal pipe external packer is not limited to being used with the 139.7 mm original casing. To meet the requirements of large displacement, for the original casing with a larger size, the composite metal pipe external packer can be adjusted according to the size of the original casing, and the original casing that meets the requirements of large displacement can all be used.

[0011] In some embodiments of the present invention, a hydraulic expansion system and a releasing structure are connected to the outside of the hanging packer. The hydraulic expansion system is used for the expansion of the bell mouth of the hanging packer, and the releasing structure is used for releasing the composite metal pipe external packer.

[0012] In some embodiments of the present invention, the above-mentioned inner casing is a Baosteel direct-connection type threaded pipe with a steel grade of BG140TT, which is used to provide a fracturing liquid supply channel.

[0013] In some embodiments of the present invention, a plurality of original perforation holes are provided on the above-mentioned original wellbore. The perforation section of the inner casing is arranged in a dislocation position with the plurality of original perforation holes, and a plurality of repeated fracturing perforation holes are formed after fracturing.

[0014] Secondly, the embodiments of the present application provide a reconstruction method for a completion string of a horizontal wellbore, including the following steps: S1. Clean the inner wall of the original casing, and conduct a wellbore verification to verify the integrity of the wellbore; S2. Determine the position and quantity of the composite metal pipe external packers, and arrange the pipe string structure based on the fracturing design; S3. Lower the reconstruction string into the original casing, set the composite metal pipe external packer and the hanging packer, seal the annulus between the original casing and the inner casing, and form a plurality of independent fracturing sections; S4. Conduct a full-well pressure test to verify the plugging effect and complete the wellbore reconstruction.

[0015] In some embodiments of the present invention, the above-mentioned step S1 is specifically as follows: For wellbore cleaning, use a solid-free low-density and well-diluted and shearable well-washing fluid to circulate and flush the wellbore at a small displacement to the artificial bottom hole. The purpose is to clean the attachments such as sediment and oil scale in the wellbore. After sand washing and well flushing to the bottom, use an elastic scraper to clean the debris on the well wall to the artificial bottom hole, and fully circulate the well-washing fluid for two more weeks. After cleaning, use a single milling column and a double milling column with the same outer diameter as the composite metal pipe external packer to conduct two simulated well flushes respectively. The purpose is to check the deformation of the inner casing in the well and ensure that the large-diameter reconstruction string can be safely lowered. If the milling column encounters resistance due to casing deformation, the well wall can be slightly ground. After completion, conduct a pressure test on the casing above the hanging packer. The pressure of the pressure test is the rated pressure of the flange used, and keep the pressure stable for 10 minutes.

[0016] In some embodiments of the present invention, the above-mentioned step S2 is specifically as follows: After the wellbore preparation is completed, start to lower the wellbore reconstruction string into the original casing. Before lowering the reconstruction string, it is necessary to jointly determine the position and quantity of the composite metal pipe external packers according to the previous production situation of the target well, the downhole production situation, and the new fracturing design. The position where the composite metal pipe external packer is lowered is to strictly seal different measure and pressure system well sections, so as to maximize the formation reservoir productivity and the fracturing transformation effect; after determining the position and quantity of the composite metal pipe external packers, according to the wellsite liner length data and tool data, arrange the pipe string program according to the fracturing design, and at the same time determine the position of the hanging packer and the total length of the liner.

[0017] In some embodiments of the present invention, the above-mentioned step S3 is specifically as follows: Use the running drill string to lower the reconstruction string into the well. During this process, it is necessary to control the pipe string lowering speed and maintain grouting to maintain the pressure balance inside and outside the pipe. The wellbore fluid needs to be free of solid phase and impurities. The grouting fluid is treated with multi-stage filtration and magnet adsorption. After lowering, first establish circulation at a small displacement to determine the accurate setting position. After sitting at the bottom of the well, the reconstruction string can be in a lifting state. After confirming the setting position, start the pump and pump resin balls. Reduce the displacement before the resin balls arrive, observe the pump pressure. After the resin balls arrive, confirm again that the reconstruction string is in a lifting state, and start to press to set the packer. First, hold the pressure to permanently close the isolation valve, continue to press and stabilize the pressure, perform the release hydraulic operation, continuously press and stabilize the pressure, complete the setting of the composite metal pipe external packer and the inflation and pasting of the hanging packer bell mouth, lower the pipe string to detect and verify the setting result, and lower the running drill string after completing the inflation and setting.

[0018] In some embodiments of the present invention, the above-mentioned step S4 is specifically as follows: After the new wellbore reconstruction is completed, it is necessary to verify the plugging effect. Perform a pressure test on the entire wellbore at the wellhead. The test pressure should be 2 - 6 Mpa higher than the repeated fracturing construction pressure of the target well, and it is qualified if the pressure is stabilized for more than 15 minutes without dropping.

[0019] In some embodiments of the present invention, the length of the subsidy section of the above-mentioned hanging packer is 10 - 50 m, which is used to realize the one-time setting of multiple composite metal pipe external packers.

[0020] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0021] 1. The inner diameter of the reconstruction string of the present invention is 98 mm, which can significantly reduce the friction during the repeated fracturing construction of old wells, meet the requirements of large displacement construction, and achieve better reservoir transformation effects;

[0022] 2. By adopting the method of combining a large-diameter inner casing with multiple composite metal pipe external packers, the wellbore reconstruction of the long horizontal section is realized, effectively avoiding the problems of poor technical reliability, insufficient pressure bearing, and high technical requirements of technologies such as chemical plugging, expansion pipe subsidy, and annular cement slurry filling.

[0023] 3. Cementing is not required, which simplifies the wellbore reconstruction steps and reduces the construction cost. Brief Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 It is a schematic structural diagram of a completion string for a horizontal wellbore provided by the present invention;

[0026] Figure 2 It is a schematic structural diagram of a composite metal pipe external packer of a completion string for a horizontal wellbore provided by the present invention;

[0027] Figure 3 It is a schematic cross-sectional structural diagram of a completion string for a horizontal wellbore provided by the present invention.

[0028] Reference numerals: 1 - original casing; 2 - hanging packer; 3 - inner casing; 4 - composite metal pipe external packer; 5 - shear ball seat; 6 - float collar; 7 - float shoe; 8 - original perforation hole; 9 - refracturing perforation hole; 10 - annulus; 100 - metal body; 200 - rubber barrel. Detailed Description of the Embodiments

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer are all conventional products that can be obtained through commercial purchase.

[0030] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to specific embodiments.

[0031] The features and performance of the present invention will be further described in detail below in conjunction with the embodiments.

[0032] Embodiment 1

[0033] Please refer to Figures 1-3 ,Figure 1 Schematic diagram of the completion string structure of the present invention; Figure 2 Schematic diagram of the structure of the composite metal pipe external packer 4 of the present invention; Figure 3 Schematic diagram of the cross-sectional structure of the completion string of the present invention.

[0034] This embodiment provides a completion string for a horizontal wellbore, including an original casing 1, an inner casing 3, a hanging packer 2, a shear ball seat 5, a float collar 6, a float shoe 7, and a plurality of composite metal pipe external packers 4. The inner casing 3 is located in the original casing 1. One end of the inner casing 3 is connected with a hanging packer 2, and the hanging packer 2 is used to hang and fix the inner casing 3 at the wellhead. The other end of the inner casing 3 is sequentially connected with a shear ball seat 5, a float collar 6, and a float shoe 7. The shear ball seat 5 is located in the original casing 1 and is used to cooperate with a resin ball to block the lower end of the inner casing 3. The float collar 6 and the float shoe 7 are both located in the original casing 1 and are used to guide the inner casing 3 to be lowered and prevent backflow. The plurality of composite metal pipe external packers 4 are sequentially and spacedly connected with the inner casing 3 and are used to block the annulus 10 between the original casing 1 and the inner casing 3 and form a plurality of fracturing sections.

[0035] In order to satisfy the connection of each component at the lower end of the inner casing 3, the above-mentioned shear ball seat 5 is threadedly connected to the lower end of the inner casing 3, one end of the float collar 6 is threadedly connected to the shear ball seat 5, and the other end is threadedly connected to the float shoe 7.

[0036] In order to satisfy the plugging effect of the composite metal pipe external packer 4, the above-mentioned composite metal pipe external packer 4 includes a rubber barrel 200 and two metal bodies 100. The two metal bodies 100 are respectively fixedly connected to both ends of the rubber barrel 200. After the rubber barrel 200 expands, it is in interference fit with the inner wall of the original casing 1. The two metal bodies 100 are also both threadedly connected to the inner casing 3.

[0037] In order to achieve the technical effect of large displacement, the outer diameter of the above-mentioned inner casing 3 is 114.3 mm, and the inner diameter is 98 mm; the outer diameter of the composite metal pipe external packer 4 is 116 mm, and the inner diameter is 98 mm. The original casing 1 of the old wellbore to be reconstructed has an outer diameter of 139.7 mm and an inner diameter of 124.6 mm. This size is set to achieve the optimal implementation effect. At the same time, the inner through-diameter of the hanging packer 2 is 98 mm, so as to achieve that the inner through-diameter of the reconstructed string ≥ 98 mm.

[0038] In order to achieve the plugging effect of the composite metal pipe external packer 4, a hydraulic expansion system and a releasing structure are connected to the outside of the above-mentioned hanging packer 2. The hydraulic expansion system is used for the expansion of the bell mouth of the hanging packer 2, and the releasing structure is used for releasing the composite metal pipe external packer 4.

[0039] In order to increase the durability of the inner casing 3, the above-mentioned inner casing 3 is a Baosteel direct-connection type threaded pipe, and the steel grade is BG140TT, which is used to provide a fracturing liquid supply channel.

[0040] To ensure the normal operation of subsequent construction, multiple original perforation holes 8 are provided on the above-mentioned original wellbore. The perforation section of the inner casing 3 is arranged out of position with respect to the positions of the multiple original perforation holes 8, and multiple repeated fracturing perforation holes 9 are formed after fracturing.

[0041] During use, the wellbore reconstruction string is lowered into the original casing 1. Multiple composite metal pipe external packers 4 are used to segmentally seal the annulus 10 between the original casing 1 and the reconstruction string to form multiple fracturing sections. The suspended packer 2 is used to suspend and seal the lowered reconstruction string and ensure the overall fixation of the reconstruction string. The shear ball seat 5 cooperates with a thrown ball to block the end of the reconstruction string, thereby realizing the secondary completion of wellbore reconstruction in a horizontal well and reconstructing a new wellbore environment.

[0042] Embodiment 2

[0043] This embodiment provides a method for reconstructing a completion string for a horizontal wellbore, including the following steps:

[0044] S1. Clean the inner wall of the original casing 1. For wellbore cleaning, a displacement-free low-density and well-diluted and shearable well-washing fluid is used for small-displacement circulating flushing of the wellbore to the artificial bottom hole. After sand washing and reaming to the bottom, an elastic scraping tool is used to clean the debris on the well wall to the artificial bottom hole, and then the well is fully circulated again for two weeks. After cleaning, a single milling column and a double milling column with the same outer diameter as the composite metal pipe external packer 4 are respectively used for two simulated reamings. First, the single milling column reaming string is used. The single milling column reaming string includes: a single roller bit, a double female joint, 1 watermelon peel mill, 1 string of heavy drill pipe, and drill tools to the wellhead. After lowering into the wellbore until the artificial bottom hole, then the double milling column reaming string is used. The double milling column reaming string includes: a single roller bit, a double female joint, 1 watermelon peel mill, 1 root of heavy drill pipe, 1 root of watermelon peel mill, 1 string of heavy drill pipe, and drill tools to the wellhead. Secondary simulated reaming is carried out at intervals of one drill pipe. During the lowering process, it is required to be stable and uniform. The pure lowering speed of the drill pipe in the vertical section is required to be greater than 60 seconds / column, and the pure lowering speed of the drill pipe in the build section and the horizontal section is required to be greater than 90 seconds / column. After entering the build section, the up and down movement of the drill string is stable, and the friction resistance is recorded for each column during the up and down movement. If there is resistance in the open hole, after deducting the normal friction resistance, the applied pressure shall not exceed 5 tons. After passing, the up and down movement in the blocked section shall be carried out no less than 3 times to ensure that it can "go down and be pulled out". After the friction resistance is normal, continue to lower for reaming; if the applied pressure exceeds 5 tons, then ream through, and after passing, repeatedly carry out the up and down movement in this well section until the friction resistance is normal. After confirming that the wellbore is unobstructed, circulate the well with a large displacement for more than one and a half weeks to fully discharge cuttings and the like from the wellbore to ensure the cleanliness of the wellbore. Finally, lift the reaming string above the suspended packer 2, and conduct a short trip to verify the reaming effect. Repeat the lowering without encountering resistance and with no obvious change in the friction resistance. The repeat interval time is not less than 10 hours. If the milling column encounters resistance due to casing deformation, the well wall can be slightly ground. After completion, pressure test the casing above the suspended packer 2, and the test pressure is the rated pressure of the flange used, and keep the pressure stable for 10 minutes;

[0045]

[0045] After the wellbore preparation is completed, the wellbore reconstruction string is lowered into the original casing 1. Before lowering the reconstruction string, it is necessary to jointly determine the position and quantity of the composite metal pipe external packer 4 according to the previous production situation of the target well, the downhole production situation, and the new fracturing design. The position where the composite metal pipe external packer 4 is lowered is to strictly seal the well sections with different measures and pressure systems, so as to maximize the formation reservoir productivity and the fracturing transformation effect. After determining the position and quantity of the composite metal pipe external packer 4, according to the wellsite liner length data and tool data, the pipe string program is arranged according to the fracturing design, and at the same time, the position of the hanging packer 2 and the total length of the liner are determined;

[0046] Use the running drill string to lower the reconstruction string into the well. During this process, it is necessary to control the lowering speed of the pipe string and maintain grouting to maintain the pressure balance inside and outside the pipe. The wellbore fluid should be free of solids and impurities. The grouting fluid is treated by multi-stage filtration and magnet adsorption. After lowering, first establish circulation at a small displacement to determine the accurate setting position. After sitting on the bottom of the well, the reconstruction string can be in a lifted state. After confirming the setting position, start the pump and pump resin balls. Reduce the displacement before the resin balls reach the position and observe the pump pressure. After the resin balls reach the position, confirm again that the reconstruction string is in a lifted state and start to apply pressure to set the packer. First, apply pressure to permanently close the isolation valve, continue to apply pressure and stabilize the pressure, perform the releasing hydraulic operation, continuously apply pressure and stabilize the pressure to complete the setting of the composite metal pipe external packer 4 and the expansion and pasting of the bell mouth of the hanging packer 2, seal the annulus 10 between the original casing 1 and the inner casing 3, form multiple independent fracturing sections, lower the pipe string to detect and verify the setting result, and lower the running drill string after completing the expansion and setting;

[0047]

[0046] After the new wellbore reconstruction is completed, it is necessary to verify the plugging effect. The entire wellbore is pressure-tested at the wellhead. The test pressure should be 4 Mpa higher than the repeated fracturing construction pressure of the target well, and it is qualified if the pressure is stabilized for more than 15 minutes without dropping, and the wellbore reconstruction is completed.

[0048] Example 3

[0049] On the basis of Example 2, in this Example 3, the wellbore reconstruction is carried out for a horizontal well with a horizontal section length of 1200 meters and cemented with a casing with an inner diameter of 124.6 mm. The initial 12-stage staged fracturing is carried out, the construction pressure is 69 - 78 MPa, and the construction displacement is 15 m 3 / min.

[0050]

[0049] According to the construction steps of Example 2, a small casing with an outer diameter of 114.3 mm and an inner diameter of 98 mm is lowered for secondary completion, and the annulus 10 is plugged and reconstructed using a composite metal pipe external packer 4 with an outer diameter of 116 mm and an inner diameter of 98 mm.

[0051] After the reconstruction is completed, the whole wellbore is pressure tested. The test pressure is 80 MPa. After stabilizing the pressure for 15 minutes, the pressure does not drop, meeting the conditions for refracturing. The inner diameter of the wellbore after reconstruction is 98 mm. Refracturing is carried out in 9 sections. The construction pressure is 65 - 75 MPa, and the construction displacement is 12 m 3 / min, and the secondary fracturing construction is successfully completed.

[0052] From the above data, it can be seen that the new wellbore after reconstruction can withstand high-pressure construction of 80 MPa, and the construction displacement meets the requirements of large-displacement construction, proving the feasibility of the wellbore reconstruction scheme of this application, solving the technical drawbacks of insufficient pressure resistance and small displacement in wellbore reconstruction in the prior art. At the same time, cementing is not required, simplifying the reconstruction steps and reducing the construction cost.

[0053] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

Claims

1. A horizontal wellbore completion string, characterized in that It includes an original casing, an inner casing, a hanging packer, a shear ball seat, a float collar, a float shoe, and multiple composite metal tube external packers. The inner casing is located in the original casing. One end of the inner casing is connected to the hanging packer, which is used to hang and fix the inner casing at the wellhead. The other end of the inner casing is connected to a shear ball seat, a float collar, and a float shoe in sequence. The shear ball seat is located in the original casing and is used to cooperate with a resin ball to seal the lower end of the inner casing. The float collar and the float shoe are both located in the original casing to guide the inner casing and prevent backflow. A plurality of composite metal pipe external packers are sequentially connected to the inner casing at intervals to seal the annulus between the original casing and the inner casing and form a plurality of fracturing sections.

2. The horizontal wellbore completion string according to claim 1, characterized in that, The composite metal pipe external sealer includes a rubber sleeve and two metal bodies. The two metal bodies are fixedly connected to the two ends of the rubber sleeve respectively. After the rubber sleeve expands, it has an interference fit with the inner wall of the original casing. The two metal bodies are also threadedly connected to the inner casing.

3. The horizontal wellbore completion string according to claim 1, characterized in that, The outer diameter of the outer casing is 139.7 mm and the inner diameter is 124.6 mm; the outer diameter of the inner casing is 114.3 mm and the inner diameter is 98 mm; the outer diameter of the composite metal pipe external packer is 116 mm and the inner diameter is 98 mm.

4. The horizontal wellbore completion string according to claim 2, wherein, The suspension packer is externally connected to a hydraulic expansion system and a release structure. The hydraulic expansion system is used for the bell-mouth expansion of the suspension packer, and the release structure is used for releasing the composite metal pipe external packer.

5. A reconstruction method for a completion string in a horizontal wellbore, according to any one of claims 1 to 4, characterized in that The following steps are involved: S1. Clean the inner wall of the original casing and verify the integrity of the wellbore; S2. Determine the position and quantity of the composite metal pipe external packer and arrange the pipe string structure based on the fracturing design; S3. Run the reconstruction string into the original casing, set the composite metal pipe external packer and the suspension packer, seal the annulus between the original casing and the inner casing, and form multiple independent fracturing stages; S4. Perform full-well pressure testing to verify the plugging effect and complete wellbore reconstruction.

6. The method according to claim 5, characterized in that, The step S1 specifically comprises: using a solid-free well washing fluid to circulate and flush the wellbore to the artificial bottom of the well, and after sand flushing and clearing the well to the bottom, using an elastic scraper to clean the well wall debris to the artificial bottom of the well, and then fully circulating and washing the well again for two weeks. After cleaning, using a single milling column and a double milling column with the same outer diameter as the composite metal pipe external packer to perform two simulated well clearing operations respectively. After completion, the upper casing of the suspension packer is pressure tested. The pressure of the pressure test is the rated pressure of the flange used, and the pressure is maintained for 10 minutes.

7. The method according to claim 5, characterized in that, The specific steps of step S2 are as follows: the position and quantity of the composite metal tube external packer are determined based on the previous production conditions of the target well, the downhole production conditions and the new fracturing design; the position where the composite metal tube external packer is lowered needs to strictly isolate the well sections with different measures and pressure systems; the pipe string procedure is discharged according to the fracturing design based on the well site tail pipe length data and tool data; and the position of the hanging packer and the total length of the tail pipe are determined at the same time.

8. The method according to claim 5, wherein The specific steps of step S3 are as follows: Lower the reconstructed pipe string into the well using a drill string. During this process, it is necessary to control the lowering speed of the pipe string and maintain grouting to maintain the pressure balance inside and outside the pipe. The well fluid should be free of solid phase and impurities. The grouting fluid is treated with multi-stage filtration and magnet adsorption. After lowering, start the pump and pump resin balls. Before the resin balls reach the designated position, reduce the displacement and observe the pump pressure. After the resin balls reach the designated position, confirm again that the reconstructed pipe string is in a lifting state, start to apply pressure to set the packer. First, apply pressure to permanently close the isolation valve, continue to apply pressure and stabilize the pressure, perform the releasing hydraulic operation, continuously apply pressure and stabilize the pressure to complete the setting of the composite metal pipe external packer and the expansion and pasting of the hanger packer bell mouth. Lower the pipe string to detect and verify the setting result. After completing the expansion and hanging, lower the drill string.

9. The method according to claim 5, characterized in that, The specific steps of step S4 are as follows: Conduct a pressure test on the entire wellbore at the wellhead position. The test pressure should be 2 - 6 Mpa higher than the repeated fracturing construction pressure of the target well, and it is qualified if the pressure is stabilized for more than 15 minutes without dropping.

10. The method according to claim 5, wherein The length of the subsidy section of the hanger packer is 10 - 50 m, which is used to achieve the setting of multiple composite metal pipe external packers at one time.

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