A tool and method for constructing a horizontal well repetitive volumetric fracturing wellbore reconstruction.

Abstract

This invention discloses a tool and method for constructing a horizontal wellbore through repeated volumetric fracturing. The tool includes a surface control device and a downhole main unit, with the surface control device located outside the downhole main unit. The downhole main unit includes a cylinder, with a top seat and a base connected to its top and bottom ends via upper and lower bearings, respectively. Both the top seat and the base are cylindrical. An electric motor is installed inside the base and connected to the surface control device and the lower bearing. A magnetic positioning device is installed inside the cylinder and connected to the surface control device. Several nozzles are provided on the sidewall of the cylinder, and each nozzle has a pressure-bearing, fracture-resistant outer wall matching its size. A connector for connecting to tubing is fixedly installed at the upper end of the top seat. Packers are installed on the outer sides of both the top seat and the base. This invention can reduce the amount of materials used in wellbore reconstruction and lower construction material costs.

Description

Technical Field

[0001] This invention patent belongs to the field of oil and gas development technology, specifically relating to the construction tools and methods for horizontal well reconstruction using repeated volumetric fracturing. Background Technology

[0002] Horizontal well staged volumetric fracturing can significantly increase the drainage area of ​​oil and gas reservoirs, making it an effective way to improve the production of single wells in low-permeability oil and gas reservoirs. However, with the extension of production time, well production gradually declines due to factors such as the initial stimulation scale and reduced conductivity of the fracture system, with some wells even becoming shut down. Early-stage horizontal wells, limited by technological conditions, had small-scale initial stimulation, resulting in low reservoir utilization. Simultaneously, poor reservoir properties and the development of natural fractures accelerated the decline of formation energy. Due to their long production life, older fractures contribute virtually no production, but there are significant remaining reserves between segments, indicating substantial potential for further stimulation and production enhancement. Repeated fracturing technology can be used to restore and increase production. However, directly repeating fracturing on older horizontal wells is limited in scale, difficult, and risky. Horizontal wells can be rebuilt first, and the rebuilt horizontal wells are like new wells, capable of large-scale volumetric fracturing. This can effectively increase the volume of repeated stimulation of low-yield old wells and the degree of reservoir utilization. At the same time, the implementation of this technology can effectively improve the scale and efficiency of fracturing stimulation, while greatly reducing the risks of repeated fracturing operations. The wellbore reconstruction technology provides a new direction for the efficient management of low-yield and inefficient horizontal wells in old areas, and has important practical significance for tapping the remaining oil potential in old areas.

[0003] At present, there are two main methods for reconstructing horizontal wells by repeated volume fracturing at home and abroad: (1) One is the casing-in-casing reconstruction process, which involves inserting a small-sized casing into the horizontal section of the original casing and sealing the small-sized casing in the original casing with cement to reconstruct a small-sized well; (2) The other is the chemical plugging well reconstruction process, which involves injecting chemical plugging material into a large section of the horizontal section of the original casing. After the plugging material has solidified, the cylindrical plugging material smaller than the inner diameter of the casing is drilled out, leaving a 5-10mm thin annular outer wall that is tightly attached to the inner wall of the casing. A new well is formed by relying on the solidified plugging material.

[0004] However, the advantages and disadvantages of the above two methods are as follows: (1) The inner casing well reconstruction process has the advantage that the bearing capacity of the well can be significantly improved, the safety factor of the well can be increased, and the stability and compressive strength of the well can be enhanced due to the adoption of a double steel pipe support structure. The disadvantage is that it requires a large amount of steel and cement, and the cost is high; at the same time, due to the small gap between the two casings, it is easy to get stuck during the lowering process, the small casing is difficult to center, and the cementing construction is difficult; it is not suitable for old or severely damaged wells; after the small casing is lowered, the inner diameter of the well is reduced, which affects the fracturing operation discharge and sand addition scale. (2) Chemical plugging well reconstruction process has the advantage that the whole well can be reconstructed and repaired, and the repaired well has good integrity and high pressure resistance. The disadvantage is that the whole well needs to be repaired, which requires a large amount of chemical plugging material. The material cost and construction cost are too high, resulting in high well reconstruction cost. Moreover, the subsequent drilling and plugging of the whole well results in a huge amount of wasted material, a large amount of drilling and plugging work, and a complicated process, which is not conducive to large-scale promotion and application. In addition, in order to ensure the strength of the well after curing, the outer thin wall of the annulus needs to be retained, which leads to a reduction in the inner diameter of the well and affects the subsequent construction. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a tool and method for constructing a horizontal well repetitive volumetric fracturing wellbore reconstruction. This method is highly targeted, reduces the amount of wellbore reconstruction materials used, and lowers construction material costs.

[0006] A tool for reconstructing a horizontal well using repeated volumetric fracturing includes a surface control device and a downhole main unit. The surface control device is located outside the downhole main unit. The downhole main unit includes a cylinder. The top and bottom ends of the cylinder are connected to a top seat and a base via upper and lower bearings, respectively. Both the top seat and the base are cylindrical. An electric motor for driving the cylinder to rotate is installed inside the base. The electric motor is connected to the surface control device and also to the lower bearing. A magnetic positioning device is installed inside the cylinder and is connected to the surface control device. Several nozzles are provided on the side wall of the cylinder. Each nozzle has a pressure-bearing, fracture-resistant outer wall matching the size of the nozzle. A connector for connecting to tubing is fixedly installed at the upper end of the top seat. Packers are installed on the outer sides of both the top seat and the base.

[0007] Preferably, the number and location of the nozzles match the number and density of the perforations in a perforation cluster in the target horizontal well.

[0008] Preferably, a baffle is also provided around the outside of the nozzle along the nozzle.

[0009] Preferably, the nozzle is funnel-shaped.

[0010] Preferably, the packer is a mechanical packer.

[0011] Preferably, the baffle is made of flexible rubber material.

[0012] A method for reconstructing a horizontal well using repeated volumetric fracturing, employing the aforementioned construction tools, is detailed below:

[0013] (I) Preparation of modified ultra-high molecular weight polyethylene fiber: Nano-silica was activated at 300-350℃ for 3h, and then the activated nano-silica and silane coupling agent were dispersed in toluene, ultrasonically dispersed for 10-15min, heated under reflux at 80-90℃ for 2h, cooled, centrifuged, and the precipitate obtained by centrifugation was washed three times with anhydrous ethanol, dried and pulverized to obtain modified silica; ultra-high molecular weight polyethylene fiber was dispersed in a mixed solution of chromic acid, hydrochloric acid and cerium chloride and soaked for 2-2.5h, filtered, and then soaked in octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate solution for 1-1.5h, filtered, and polydopamine coating solution was coated on its surface; then the modified silica and Skacher hydrophobic modified hydroxyethyl cellulose were mixed and coated on its surface, and dried and dispersed to obtain modified ultra-high molecular weight polyethylene fiber;

[0014] (ii) The modified ultra-high molecular weight polyethylene fiber is prepared into fiber rivets as follows: Take the modified ultra-high molecular weight polyethylene fiber, cut it into fiber segments with a length of 35 mm, and form a fiber bundle of 100 fiber segments. Tie the fiber bundle three times along the middle position to form a fiber rivet with a raised middle, symmetrical ends, and a tail length of 12-13 mm at both ends.

[0015] (iii) Based on the pre-perforation data and fracturing stimulation construction data of the horizontal well, calculate the amount of casing repair agent required for one perforation section, mix the fiber rivets with the casing repair agent evenly, and then add them into the cylinder;

[0016] (iv) Connect the connector of the tool to the tubing, lower the tubing into the horizontal section, and simultaneously install the packers to the outside of the top seat and base of the tool, lowering them into the horizontal well together with the tool. When the tool is lowered to the position of the uppermost perforation cluster at the farthest end of the horizontal well, lift and rotate the tubing to set the packers, locking the first perforation cluster between the two packers.

[0017] (v) The motor and magnetic positioning device are turned on by the ground control device. The cylinder rotates radially under the drive of the motor. When the magnetic positioning device identifies the uppermost perforation hole of the first perforation cluster, it sends a signal to the ground control device to control the motor to stop rotating. At this time, all the nozzles on the cylinder are aligned with all the perforation holes of the first perforation cluster.

[0018] (vi) Apply hydraulic pressure to the wellbore through the tubing to break the pressure-bearing outer wall. The casing repair agent and fiber rivets in the cylinder are squeezed into the perforation holes through the spray holes. After curing and bonding, the perforation holes of the first perforation cluster are sealed.

[0019] (vii) Repeat steps (iii) to (vi) to seal all the perforation holes of the perforation cluster, and then remove the tool;

[0020] (viii) After the casing repair agent that seals the perforation hole has completely cured, drill again in the next pass, and drill away the cured casing repair agent and fiber rivets that protrude and solidify at the blast hole opening along the inner wall of the casing, so as to keep the inner wall of the casing smooth and full bore.

[0021] (ix) Test the wellbore to 50 MPa. If the test is successful, the wellbore reconstruction work is completed. If the test fails, re-seal and repair the unsuccessful parts until the entire wellbore passes the test.

[0022] Preferably, the silane coupling agent is KH550 and KH560; the weight ratio of chromic acid, hydrochloric acid and cerium chloride is 5:(3-4):(1-2); the mass ratio of the activated nano-silica to the silane coupling agent is (4-6):1; and the mass ratio of the modified silica and Skacher hydrophobic modified hydroxyethyl cellulose is (2-4):1.

[0023] Preferably, when using a polydopamine coating solution, the mass ratio of the polydopamine coating solution to the ultra-high molecular weight polyethylene fiber is 1.2-1.3:1; when using modified silica and Skacher hydrophobic modified hydroxyethyl cellulose for coating, the total mass ratio of the modified silica and Skacher hydrophobic modified hydroxyethyl cellulose to the ultra-high molecular weight polyethylene fiber is 1.2-1.5:1.

[0024] Preferably, the mass ratio of the fiber rivet to the sleeve repair agent is (0.5-2):100.

[0025] The casing repair agent described in this invention is a high-strength composite material casing repair agent disclosed in Chinese Patent CN113735506B.

[0026] Advantages of this invention:

[0027] (1) The well reconstruction method of the present invention can seal and repair all perforations of a perforation cluster one by one at a time, which is highly targeted and can reduce the amount of well reconstruction materials used and reduce the construction material cost;

[0028] (2) The reconstructed wellbore has high pressure resistance, which can meet the requirements of large-volume fracturing construction in the later stage;

[0029] (3) The reconstructed wellbore of the present invention has the same inner diameter as the original wellbore and can maintain the full bore, without affecting the subsequent jacking and unjacking tools, and without affecting the subsequent construction discharge and renovation scale;

[0030] (4) In this invention, modified ultra-high molecular weight polyethylene fiber rivets are added to the casing repair agent. The two have strong interfacial adhesion and the rivets have antistatic properties. After curing, the fiber rivets can be sealed on the outermost side of the blast hole, which can seal the opening and improve the sealing strength of the blast hole opening.

[0031] (5) The rivet of the present invention adopts a tail-symmetrical structure design to ensure that at least one end of the polymer fiber rivet is fixed in the repair agent to the greatest extent, so that the knot and the repair agent are bonded more firmly; although the material has high compressive strength, it is easy to shear, which is beneficial for subsequent drilling and grinding, and to maintain the full diameter inside the sleeve.

[0032] (6) The tool and process are simple, easy to operate, and have low construction costs. Attached Figure Description

[0033] Figure 1 A schematic diagram of the structure of the horizontal well repetitive volumetric fracturing wellbore reconstruction construction tool provided by this invention;

[0034] Figure 2 Enlarged schematic diagram of a fiber rivet extruded through a nozzle;

[0035] Among them, 1-connector, 2-top seat, 3-base, 4-magnetic positioning device, 5-baffle, 6-spray hole, 8-motor, 9-cylinder, 10-shooting hole, 11-fiber rivet. Detailed Implementation

[0036] Example 1

[0037] A tool for reconstructing a horizontal well using repeated volumetric fracturing includes a surface control device and a downhole main unit. The surface control device is located outside the downhole main unit. The downhole main unit includes a cylinder 9 containing casing repair agent. The top and bottom ends of the cylinder 9 are connected to a top seat 2 and a base 3 via upper and lower bearings, respectively. Both the top seat 2 and the base 3 are cylindrical. An electric motor 8 for driving the cylinder 9 to rotate is installed inside the base 3. The electric motor 8 is connected to the surface control device and also to the lower bearing. A magnetic positioning device 4 is installed inside the cylinder 9 and is connected to the surface control device. Several nozzles 6 are provided on the side wall of the cylinder 9. Each nozzle 6 has a pressure-bearing, fracture-resistant outer wall matching the size of the nozzle. A connector 1 for connecting to the tubing is fixedly installed at the upper end of the top seat 2. Packers are installed on the outer sides of both the top seat 2 and the base 3.

[0038] The pressure-bearing and breakable outer wall can be made of aluminum foil. Its main function is to seal the nozzle 6 when no pressure is applied, keep the cylinder 9 intact, and hold the sleeve repair agent. When subjected to a certain pressure, the outer wall can break, and the sleeve repair agent in the cylinder 9 can be sprayed out from the nozzle 6.

[0039] The connector 1 is connected to the oil pipe via a threaded nut.

[0040] The inner ring of the lower bearing is connected to the cylinder 9 and the motor 8, and the outer ring of the lower bearing is connected to the base 3. When the motor 8 rotates, it drives the cylinder 9 to rotate by rotating the bearing.

[0041] Example 2

[0042] Based on the above embodiments, the number and location of the nozzles 6 are matched with the number and density of perforations in a perforation cluster in the target horizontal well.

[0043] The nozzle 6 is trumpet-shaped.

[0044] A baffle 5 is also provided around the outside of the nozzle 6 along the nozzle 6.

[0045] More preferably, the baffle 5 is made of flexible rubber material.

[0046] The packer is a mechanical packer. More preferably, the packer is a Y211-115 packer.

[0047] The horn-shaped flexible rubber nozzle 6 can reduce the spray resistance of the repair agent inside the cylinder 9 and prevent the repair agent from clogging the nozzle 6; secondly, the horn-shaped nozzle 6 has a large range, which can encompass the injection orifice 10 within the nozzle 6, ensuring that each focused orifice can be injected with a sufficient amount of repair agent.

[0048] Example 3

[0049] Modified ultra-high molecular weight polyethylene fiber rivets were prepared, wherein the ultra-high molecular weight polyethylene fiber (UHMWPE) used was produced by Yizheng Chemical Fiber Co., Ltd., as detailed below:

[0050] (1) Preparation of modified ultra-high molecular weight polyethylene fiber: Nano-silica was activated at 300℃ for 3h, and then the activated nano-silica, KH550 and KH560 were dispersed in toluene, ultrasonically dispersed for 15min, heated under reflux at 80℃ for 2h, cooled, centrifuged, and the precipitate obtained by centrifugation was washed 3 times with anhydrous ethanol, dried at 105℃ for 3h and then pulverized to obtain modified silica; wherein, the mass of KH550 and KH560 were equal, and the mass ratio of the total mass of KH550 and KH560 to the mass of activated nano-silica was 1:4; ultra-high molecular weight polyethylene fiber was dispersed in chromic acid, hydrochloric acid and chlorine in a weight ratio of 5:3:2. The fibers were etched by immersion in a mixed solution of cerium hydroxide for 2 hours, filtered, and then immersed in an octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate solution for 1 hour, filtered, and coated with a polydopamine coating solution at a mass ratio of 1.2:1 to ultra-high molecular weight polyethylene (UHMWPE) fibers. Then, a mixture of modified silica and skacher hydrophobic modified hydroxyethyl cellulose at a mass ratio of 2:1 was coated onto the surface, and dried and dispersed to obtain modified UHMWPE fibers. During immersion, the immersion solution was in excess, sufficient to submerge the fibers.

[0051] (2) Prepare the modified ultra-high molecular weight polyethylene fiber into a modified ultra-high molecular weight polyethylene fiber rivet: Take the modified ultra-high molecular weight polyethylene fiber, cut it into fiber segments with a length of 35 mm, form a fiber bundle with 100 fiber segments, tie the fiber bundle three times along the middle position to form a fiber rivet with a raised middle, symmetrical ends, and a tail length of 12-13 mm at both ends.

[0052] Example 4

[0053] Modified ultra-high molecular weight polyethylene fiber rivets were prepared, wherein the ultra-high molecular weight polyethylene fiber (UHMWPE) used was produced by Yizheng Chemical Fiber Co., Ltd., as detailed below:

[0054] (1) Preparation of modified ultra-high molecular weight polyethylene fiber: Nano-silica was activated at 350℃ for 3h, and then the activated nano-silica, KH550 and KH560 were dispersed in toluene, ultrasonically dispersed for 10min, heated under reflux at 90℃ for 2h, cooled, centrifuged, and the precipitate obtained by centrifugation was washed 3 times with anhydrous ethanol, dried at 105℃ for 3h and then pulverized to obtain modified silica; wherein, the mass of KH550 and KH560 were equal, and the total mass of KH550 and KH560 was in a mass ratio of 1:6 to that of activated nano-silica; ultra-high molecular weight polyethylene fiber was dispersed in chromic acid, hydrochloric acid and cerium chloride in a weight ratio of 5:4:1. The fiber was etched by immersion in a mixed solution for 2.5 hours, filtered, and then immersed in an octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate solution for 1.5 hours, filtered, and coated with a polydopamine coating solution at a mass ratio of 1.3:1 to ultra-high molecular weight polyethylene fiber. Then, a mixture of modified silica and skacher hydrophobic modified hydroxyethyl cellulose at a mass ratio of 4:1 was coated on the surface and dried to obtain modified ultra-high molecular weight polyethylene fiber. During immersion, the immersion solution was in excess, sufficient to submerge the fiber.

[0055] (2) Prepare the modified ultra-high molecular weight polyethylene fiber into a modified ultra-high molecular weight polyethylene fiber rivet: Take the modified ultra-high molecular weight polyethylene fiber, cut it into fiber segments with a length of 35 mm, form a fiber bundle with 100 fiber segments, tie the fiber bundle three times along the middle position to form a fiber rivet with a raised middle, symmetrical ends, and a tail length of 12-13 mm at both ends.

[0056] Example 5

[0057] A method for reconstructing a horizontal wellbore using repeated volumetric fracturing was employed with the construction tools described in Example 2. The casing repair agent used was the high-strength composite material casing repair agent described in the example of Chinese Patent (CN113735506B), as detailed below:

[0058] (i) Based on the pre-perforation data and fracturing stimulation construction data of the horizontal well, calculate the amount of high-strength composite casing repair agent required for one perforation section, mix the modified ultra-high molecular weight polyethylene fiber rivet with the casing repair agent at a mass ratio of 1:100, and then add it to the cylinder 9.

[0059] (ii) Connect the connector 1 of the tool to the tubing with a threaded nut, lower the tubing into the horizontal section, and simultaneously install the packers to the outside of the top seat 2 and the base 3 of the tool, lower them into the horizontal well together with the tool, until the tool is lowered to the uppermost hole position of the first perforation cluster at the farthest end of the horizontal well, lift and rotate the tubing to drive the packers to set and seal, and lock the first perforation cluster between the two packers;

[0060] (iii) The motor 8 and magnetic positioning device 4 are turned on by the ground control device. The cylinder 9 rotates radially under the drive of the motor 8. When the magnetic positioning device 4 (MI168 leakage magnetic internal detector produced by Chengdu Xiong Gu Jia Shi Company) identifies the uppermost perforation hole of the first perforation cluster, it sends a signal to the ground control device to control the motor 8 to stop rotating. At this time, all the nozzles on the cylinder are aligned with all the perforation holes of the first perforation cluster.

[0061] (iv) Apply hydraulic pressure to the wellbore through the tubing to break the crushable outer wall of the pressurized wall. The casing repair agent and modified ultra-high molecular weight polyethylene fiber rivets 11 in the cylinder 9 are squeezed into the perforation holes 10 through the spray hole 6. After curing and bonding, the perforation holes of the first perforation cluster are sealed.

[0062] (v) Repeat steps (i) to (iv) to seal all the perforations of the perforation cluster, and then remove the tool.

[0063] (vi) After the casing repair agent that seals the perforation hole has completely cured, drill again, and drill away the casing repair agent and modified ultra-high molecular weight polyethylene fiber rivets that have protruded and solidified at the blast hole opening after curing, close to the inner wall of the casing, in order to keep the inner wall of the casing smooth and full bore. Construction is then completed.

[0064] (vii) Pressure test the wellbore to 50 MPa. If the pressure test is qualified, the wellbore reconstruction work is completed. If the pressure test is unqualified, the unqualified parts are re-sealed and repaired until the entire wellbore is qualified.

[0065] Example 6

[0066] Pre-perforation data for Well X (horizontal well) (phase angle 90°, perforation density: 16 per meter), fracturing stimulation data (9 fracturing stages, 4m / stage, 1 cluster / stage), and the method for repeated volumetric fracturing wellbore reconstruction of this horizontal well using the construction tools described in Example 2, wherein the casing repair agent is the high-strength composite material casing repair agent described in Example 1 of Chinese Patent (CN113735506B), and the specific construction method is as follows:

[0067] (i) Based on the previous perforation data of Well X (horizontal well) (phase angle 90°, perforation density: 16 per meter) and the fracturing stimulation construction data (9 fracturing stages, 4m / stage, 1 cluster / stage), calculate the amount of high-strength composite casing repair agent required for one perforation stage (0.0096m³ of repair agent required for one perforation stage). 3 Repair agent density: 1.8 g / cm³ 3 Therefore, the repair agent weighs 17.28 kg. The modified ultra-high molecular weight polyethylene fiber rivets (0.3456 kg) are mixed evenly with the casing repair agent at a mass ratio of 2:100 (155.52 kg of repair agent and 3.1104 kg of modified ultra-high molecular weight polyethylene fiber rivets are used for 9 sections of a well), and then added to the cylinder 9. Compared with the conventional horizontal well general injection of 5000-6000 kg of repair material, the precise injection method of this invention greatly saves raw materials and reduces material usage costs.

[0068] (ii) Connect the connector 1 of the tool to the tubing with a threaded nut, lower the tubing into the horizontal section, and simultaneously install the packers to the outside of the top seat 2 and the base 3 of the tool, lower them into the horizontal well together with the tool, until the tool is lowered to the uppermost hole position of the first perforation cluster at the farthest end of the horizontal well, lift and rotate the tubing to drive the packers to set and seal, and lock the first perforation cluster between the two packers;

[0069] (iii) The motor 8 and magnetic positioning device 4 are turned on by the ground control device. The cylinder 9 rotates radially under the drive of the motor 8. When the magnetic positioning device 4 (MI168 leakage magnetic internal detector produced by Chengdu Xiong Gu Jia Shi Company) identifies the uppermost perforation hole of the first perforation cluster, it sends a signal to the ground control device to control the motor 8 to stop rotating. At this time, all the nozzles on the cylinder are aligned with all the perforation holes of the first perforation cluster.

[0070] (iv) Apply hydraulic pressure to the wellbore through the tubing to break the crushable outer wall of the pressurized wall. The casing repair agent and modified ultra-high molecular weight polyethylene fiber rivets 11 in the cylinder 9 are squeezed into the perforation holes 10 through the spray hole 6. After curing and bonding, the perforation holes of the first perforation cluster are sealed.

[0071] (v) Repeat steps (i) to (iv) to seal all the perforations of the perforation cluster, and then remove the tool.

[0072] (vi) After the casing repair agent that seals the perforation hole has completely cured, drill again, and drill away the casing repair agent and modified ultra-high molecular weight polyethylene fiber rivets that have protruded and solidified at the blast hole opening after curing, close to the inner wall of the casing, in order to keep the inner wall of the casing smooth and full bore. Construction is then completed.

[0073] (vii) Test the wellbore to 50 MPa and keep the pressure unchanged for 30 minutes. If the test is qualified, the wellbore reconstruction work is completed.

[0074] To verify the effectiveness of wellbore reconstruction and improve oil production, repeated volumetric fracturing operations were performed on well X after wellbore reconstruction, with a total fluid injection volume of 600 m³. 3 6m displacement 3 / min, sand addition rate 60m³ 3 The maximum construction pressure was 55 MPa. The construction pressure was stable and there was no cross-layering of fracturing fluid. The fracturing and stimulation construction went smoothly. After repeated fracturing operations, the well's initial daily oil production was 9t, which was 8t higher than before repeated fracturing (1t / d). The production increase effect of repeated fracturing was obvious.

[0075] To verify the pressure resistance level of the wellbore, during the pressure test in step (seven), the test pressure was increased to 60 MPa and maintained for 30 minutes without change. The test pressure exceeded the pressure resistance strength (38.6 MPa) of the casing repair agent described in Example 1 of Chinese Patent (CN113735506B), indicating that the fiber rivets have a sealing effect on the perforation orifice and can also improve the sealing strength of the perforation orifice.

Claims

1. A method for constructing a horizontal well using repeated volumetric fracturing, characterized in that: The horizontal well reconstruction project utilizes a repeatable volumetric fracturing wellbore reconstruction tool, comprising a surface control device and a downhole main assembly. The surface control device is located outside the downhole main assembly. The downhole main assembly comprises a cylinder, with a top seat and a base connected to its top and bottom ends via upper and lower bearings, respectively. Both the top seat and the base are cylindrical. An electric motor for driving the cylinder's rotation is housed within the base and is connected to both the surface control device and the lower bearing. A magnetic positioning device is installed inside the cylinder and is connected to the surface control device. Several nozzles are provided on the sidewall of the cylinder, and each nozzle is fitted with a pressure-bearing, fracture-resistant outer wall matching its size. A connector for connecting to tubing is fixedly mounted on the upper end of the top seat. Packers are installed on the outer sides of both the top seat and the base. The specific construction method for reconstructing the wellbore through repeated volumetric fracturing in the horizontal well is as follows: (I) Preparation of modified ultra-high molecular weight polyethylene fiber: Nano-silica was activated at 300-350℃ for 3h, and then the activated nano-silica and silane coupling agent were dispersed in toluene, ultrasonically dispersed for 10-15min, heated under reflux at 80-90℃ for 2h, cooled, centrifuged, and the precipitate obtained by centrifugation was washed three times with anhydrous ethanol, dried and pulverized to obtain modified silica; ultra-high molecular weight polyethylene fiber was dispersed in a mixed solution of chromic acid, hydrochloric acid and cerium chloride and soaked for 2-2.5h, filtered, and then soaked in an octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate solution for 1-1.5h, filtered, and polydopamine coating solution was coated on its surface; then the modified silica and Skacher hydrophobic modified hydroxyethyl cellulose were mixed and coated on its surface, and dried and dispersed to obtain modified ultra-high molecular weight polyethylene fiber; (ii) The modified ultra-high molecular weight polyethylene fiber is prepared into a fiber rivet as follows: Take the modified ultra-high molecular weight polyethylene fiber, cut it into fiber segments with a length of 35 mm, and form a fiber bundle of 100 fiber segments. Tie the fiber bundle three times along the middle position to form a fiber rivet with a raised middle, symmetrical ends, and a tail length of 12-13 mm at both ends. (iii) Based on the pre-perforation data and fracturing stimulation construction data of the horizontal well, calculate the amount of casing repair agent required for one perforation section, mix the fiber rivets with the casing repair agent evenly, and then add them into the cylinder; (iv) Connect the connector of the construction tool to the tubing, lower the tubing into the horizontal section, and simultaneously install the packers on the outside of the top seat and base of the construction tool, lower them into the horizontal well together with the tool, until the construction tool is lowered to the position of the uppermost hole of the first perforation cluster at the farthest end of the horizontal well, lift and rotate the tubing to drive the packers to set and seal, and lock the first perforation cluster between the two packers; (v) The motor and magnetic positioning device are turned on by the ground control device. The cylinder rotates radially under the drive of the motor. When the magnetic positioning device identifies the uppermost perforation hole of the first perforation cluster, it sends a signal to the ground control device to control the motor to stop rotating. At this time, all the nozzles on the cylinder are aligned with all the perforation holes of the first perforation cluster. (vi) Apply hydraulic pressure to the wellbore through the tubing to break the pressure-bearing outer wall. The casing repair agent and fiber rivets in the cylinder are squeezed into the perforation holes through the spray holes. After curing and bonding, the perforation holes of the first perforation cluster are sealed. (vii) Repeat steps (iii) to (vi) to seal all the perforation holes of the perforation cluster, and then remove the construction tools; (viii) After the casing repair agent that seals the perforation hole has completely cured, drill again in the next pass, and drill away the cured casing repair agent and fiber rivets that protrude and solidify at the blast hole opening along the inner wall of the casing, so as to keep the inner wall of the casing smooth and full bore. (ix) Test the wellbore to 50 MPa. If the test is successful, the wellbore reconstruction work is completed. If the test fails, re-seal and repair the unsuccessful parts until the entire wellbore passes the test.

2. The method for constructing a horizontal well using repeated volumetric fracturing as described in claim 1, characterized in that: The number and location of the nozzles are matched with the number and density of perforations in a perforation cluster in the target horizontal well.

3. The method for constructing a horizontal well using repeated volumetric fracturing as described in claim 2, characterized in that: A baffle is also provided around the outside of the nozzle, along the nozzle.

4. The method for constructing a horizontal well using repeated volumetric fracturing as described in claim 3, characterized in that: The nozzle is funnel-shaped.

5. The method for constructing a horizontal well using repeated volumetric fracturing as described in claim 1, characterized in that: The packer is a mechanical packer.

6. The method for constructing a horizontal well using repeated volumetric fracturing as described in claim 3, characterized in that: The baffle is made of flexible rubber material.

7. The method for constructing a horizontal well using repeated volumetric fracturing and wellbore reconstruction according to claim 1, characterized in that: The silane coupling agent is KH550 and KH560; the weight ratio of chromic acid, hydrochloric acid and cerium chloride is 5:3~4:1~2; the mass ratio of activated nano-silica to silane coupling agent is 4~6:1; the mass ratio of modified silica and Skacher hydrophobic modified hydroxyethyl cellulose is 2~4:

1.

8. The method for constructing a horizontal well using repeated volumetric fracturing as described in claim 7, characterized in that: When using a polydopamine coating solution, the mass ratio of the polydopamine coating solution to ultra-high molecular weight polyethylene fiber is 1.2~1.3:1; when using modified silica and Skacher hydrophobic modified hydroxyethyl cellulose for coating, the total mass ratio of the modified silica and Skacher hydrophobic modified hydroxyethyl cellulose to the ultra-high molecular weight polyethylene fiber is 1.2~1.5:

1.

9. The method for constructing a horizontal well using repeated volumetric fracturing as described in claim 8, characterized in that: The mass ratio of the fiber rivet to the sleeve repair agent is 0.5~2:100.

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