Old brine discharging well plugging device and method for salt cavern energy storage bank

Abstract

The invention discloses an old discharge brine well plugging device and method for a salt cavern energy storage reservoir, and relates to the field of old discharge brine well plugging. The plugging device comprises a sleeve pretreatment tool which is used for finishing and cleaning a shaft of an old discharge brine well and can be used for reaming a set position of the shaft to an original stratum in the radial direction of the shaft; the shaft packing tool comprises a first-stage plugging assembly and a second-stage plugging assembly. The first-stage plugging assembly can plug a cavity of the salt cavern energy storage bank and an opening in the end, located below a reaming area, of the shaft. The second-stage plugging assembly is located above the first-stage plugging assembly and can plug a reaming area of the shaft, an annulus is formed in the position, close to a top opening, of the shaft, and annulus protection liquid is injected into the annulus; the well completion wellhead device is arranged at an opening in the top of the shaft and used for regularly observing and monitoring pressure changes in the annulus and the shaft. The sealing integrity of the old brine discharging well can be improved, so that the gas leakage risk of the old brine discharging well during the operation of the salt cavern energy storage reservoir is reduced.

Description

Technical Field

[0001] This invention relates to the field of old brine well plugging technology, and in particular to a device and method for plugging old brine wells in salt cavern energy storage. Background Technology

[0002] Salt cavern compressed air energy storage technology, as a highly efficient energy storage method, places extremely high demands on the sealing performance of underground energy storage facilities. The core of the long-term safe and stable operation of salt cavern energy storage facilities lies in ensuring that the salt cavern cavity and connecting shaft have reliable long-term sealing capabilities, effectively blocking gas leakage channels and avoiding problems such as decreased energy storage efficiency and safety accidents caused by sealing failure.

[0003] As critical facilities left over from salt mining, old brine drainage wells have developed potential leakage risks due to their long-term service, posing a significant threat to the sealing integrity of salt cavern energy storage facilities. To ensure the long-term stable operation of salt cavern compressed air energy storage power stations, it is essential to implement professional and high-standard sealing and remediation measures for these risky old brine drainage wells.

[0004] However, traditional sealing techniques for old brine wells have significant technical limitations in meeting the high-quality sealing requirements of compressed air energy storage in salt caverns, making them unsuitable for practical applications. Specifically, during long-term use, the inner wall of the casing in old brine wells is prone to contaminants such as crude oil, while the outer wall develops a rust layer due to environmental corrosion. In some salt mining areas, the casing may also be covered with hard and dense salt scale. These deposits severely compromise the interfacial bonding quality between the cement and the casing surface, creating a channel between the cement sheath and the casing, providing a pathway for gas leakage.

[0005] Currently, the industry lacks a systematic solution for plugging old brine wells, and the common practice is to use a simple method of directly injecting cement into the wellhead for plugging. This method suffers from the insurmountable problem of micro-annular flow, resulting in extremely poor plugging effect, failing to meet the wellbore sealing integrity requirements, and being unable to prevent the leakage of high-pressure gas during the operation of salt cavern energy storage facilities. This severely restricts the large-scale application and development of salt cavern compressed air energy storage technology.

[0006] Therefore, there is an urgent need to design a technical solution that can improve the sealing integrity of old brine wells in order to reduce the risk of gas leakage from old brine wellbores during the operation of salt cavern energy storage facilities. Summary of the Invention

[0007] The purpose of this invention is to provide a device and method for sealing old brine wells in salt cavern energy storage facilities, so as to solve the problems existing in the prior art, improve the sealing integrity of old brine wells, and reduce the risk of gas leakage from old brine wells during the operation of salt cavern energy storage facilities.

[0008] To achieve the above objectives, the present invention provides the following solution: This invention provides a device for sealing old brine wells in salt cavern energy storage facilities, comprising: Casing pretreatment tools are used for wellbore repair and cleaning of old brine discharge wells, and can be used to enlarge the wellbore radially to the original formation at a set position. A wellbore packing tool includes a primary packing assembly and a secondary packing assembly. The primary packing assembly seals the cavity of the salt cavern energy storage tank and the wellbore opening located below the enlarged area. The secondary packing assembly, located above the primary packing assembly, seals the enlarged area of ​​the wellbore. An annulus is provided near the top opening of the wellbore, and an annulus protection fluid is injected into the annulus. The wellhead device is located at the top opening of the wellbore and is used to periodically observe and monitor pressure changes in the annulus and inside the wellbore.

[0009] In one embodiment, the casing pretreatment tool includes a well gauge with an inner diameter smaller than the inner diameter of the wellbore. One end of the well gauge can be connected to the drill pipe, which can drive the well gauge into the wellbore and move it up and down along the wellbore to verify the patency of the wellbore.

[0010] In one embodiment, the casing pretreatment tool further includes a scraper, which includes a scraper body. The upper end of the scraper body is threaded to a drill pipe. The scraper body is symmetrically arranged with forward and reverse scraper blades. The drill pipe can lower the scraper body below the intended placement position of the primary sealing component inside the wellbore. The scraper body is repeatedly raised and lowered multiple times at the intended placement position of the primary sealing component until the weight of the scraper does not change, so as to achieve 360° full wellbore wall coverage scraping inside the wellbore and remove the deposits on the inner wall of the wellbore.

[0011] In one embodiment, the casing pretreatment tool further includes a milling machine, which includes a milling machine body. The lower part of the milling machine body has multiple tapered guide shoes arranged circumferentially. The outer sidewall of each guide shoe can slide against the wellbore sidewall to provide axial straightening force to the milling machine body. The upper part of the milling machine body has evenly distributed inclined teeth. The upper end of each tooth is hinged to the sidewall of the milling machine body, and the lower inner side of each tooth is connected to the sidewall of the milling machine body by a hydraulic drive mechanism. The hydraulic drive mechanism can drive the teeth to swing around the hinge point to a set position.

[0012] In one embodiment, the casing pretreatment tool further includes an reamer, which includes an reamer body with multiple blades symmetrically arranged circumferentially on the reamer body. The upper ends of the blades are hinged to the sidewalls of the reamer body, and the lower inner sidewalls of the blades are connected to the sidewalls of the reamer body via a hydraulic drive mechanism. The hydraulic drive mechanism can drive the blades to swing around the hinge point to a set position. The sidewalls of the blades are provided with alloy teeth, which can radially cut the formation in the wellbore reaming area to ream the wellbore reaming area to the original formation.

[0013] In one embodiment, the primary sealing assembly includes a bridge plug located at the junction of the top of the cavity and the bottom of the wellbore to seal and separate the cavity and the wellbore; a cement plug is provided on the top of the bridge plug to form an artificial well bottom; the cement plug is located below the enlarged area of ​​the wellbore.

[0014] In one embodiment, the secondary plugging assembly includes a metal plugging element made of a low-melting-point alloy. The metal plugging element melts and fills the enlarged area, and after cooling and solidifying, it seals with the in-situ layer at the enlarged area.

[0015] In one embodiment, the secondary plugging assembly further includes a support member made of an alloy, the melting point of which is greater than that of the metal plugging member, and the metal plugging member is bonded to the outer wall of the support member. The support member has a cavity filled with combustible material. A suspension member is connected to the top of the support member, and a cable is connected to the suspension member, with one end of the cable located outside the wellbore. An electrical cable is installed within the cable and electrically connected to an igniter located at the top of the support member and connected to the combustible material. The temperature of the combustible material after ignition is greater than the melting point of the metal plugging member but lower than the melting point of the support member.

[0016] In one embodiment, the wellhead completion device includes a pressure gauge, a main control valve, a vent valve, a pressure sensor, a flange, and a control valve. The bottom of the main channel of the wellhead completion device is connected to the top casing head of the old brine discharge well via a flange. A control valve is connected in series on the main channel as a master switch. A lateral channel is provided on the side wall of the main channel above the control valve. The main control valve is installed in the lateral channel to regulate the flow rate. The pressure gauge, pressure sensor, and vent valve are connected in the area above the lateral channel of the main channel. The vent valve, as an independent safety valve, is connected to an emergency pipeline and is used for pressure relief and safety in an emergency. The main control valve and control valve are switches that control the flow of fluid. The secondary sealing assembly is filled with cement, reaching a height near the top opening of the wellbore. The area between the top of the cement and the top opening of the wellbore forms the annulus. The pressure gauge displays the dynamic pressure in the wellbore locally. The pressure sensor transmits pressure to the pressure gauge in real time. The main control valve is used to cut off the gas supply in an emergency to prevent gas from rising. The vent valve controls the release of pressure inside the well. The control valve adjusts the flow of fluid through the annulus pressure monitoring hole. The flange is used to achieve a high-pressure sealed connection between the devices.

[0017] This invention also provides a method for plugging old brine wells in salt cavern energy storage facilities, comprising the following steps: The well was circulated to the bottom opening position of the well using a well gauge and drill pipe to verify the well patency. Use a scraper to repeatedly lift and lower the primary plugging component at the intended placement location multiple times until the suspended weight is stable, ensuring the well wall is clean. Lower the bridge plug to the designed depth, hydraulically set the seal, and then perform a water pressure test to verify the integrity of the primary seal. The corroded section of the wellbore above the bridge plug was subjected to segmented forging and milling and enlargement to remove the damaged wellbore and form a regular wellbore. The secondary sealing component is lowered to the forging and milling section, and the combustible material is ignited by the cable-triggered igniter, causing the metal sealing component to melt and fill the micro-annular gap at the interface between the wellbore and the original formation in the enlarged area, forming a metallurgical-grade permanent seal. Remove the support components from the wellbore, leaving the molten metal plugging components in the enlarged area; After the metal plug has cooled and solidified, cement is injected into the wellbore up to below the top opening of the wellbore, and left to set for 48 hours. Annular protective fluid is injected into the top of the cement, and the wellhead equipment and pressure monitoring system are installed to continuously monitor changes in annular pressure and confirm the long-term stability of the plugging.

[0018] The present invention achieves the following technical effects compared to the prior art: The casing pretreatment tool of this invention is used to remove dense salt scale and corroded casing inside the wellbore; the wellbore sealing tool achieves mechanical isolation of the wellbore sections; and the completion wellhead device is used to periodically observe and monitor pressure changes in the annulus and wellbore. This invention solves the micro-annular flow problem inherent in traditional cement plugging through multi-tool collaborative operation, meeting the requirements for pressure monitoring, pressure relief, and fluid replenishment, and significantly improving the sealing reliability of salt cavern energy storage wellbore plugging. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the scraper in the casing pretreatment tool of one or more embodiments of the present invention during downhole operation; Figure 2 This is a schematic diagram of the forging and milling tool in one or more embodiments of the present invention during downhole operation; Figure 3 This is a schematic diagram of the structure of the expander in the casing pretreatment tool during downhole operation in one or more embodiments of the present invention; Figure 4 This is a schematic diagram illustrating the application scenario of the downhole plugging tool provided in one or more embodiments of the present invention. Figure 1 ; Figure 5 This is a schematic diagram illustrating the application scenario of the downhole plugging tool provided in one or more embodiments of the present invention. Figure 2 ; Figure 6 This is a schematic diagram of the wellbore after sealing of an old brine discharge well, provided in one or more embodiments of the present invention; Figure 7 This is a schematic diagram of a wellhead completion device provided in one or more embodiments of the present invention.

[0021] Explanation of reference numerals in the attached diagram: 1-Forward scraper; 2-Reverse scraper; 3-Drill pipe; 4-Scraper body; 5-Guide shoe; 6-Teeth; 7-Forging milling machine body; 8-Alloy teeth; 9-Cutter wing; 10-Expander body; 11-Cable; 12-Suspension component; 13-Combustible material; 14-Support component; 15-Bridge plug; 16-Cavity; 17-Igniter; 18-Metal sealing component; 19-Cement plug; 20-Wellbore; 21-Receptacle; 22-Annular protective fluid; 23-Flange; 24-Control valve; 25-Main control valve; 26-Pressure sensor; 27-Blowout valve; 28-Pressure gauge. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The purpose of this invention is to provide a device and method for sealing old brine wells in salt cavern energy storage facilities, so as to solve the problems existing in the prior art, improve the sealing integrity of old brine wells, and reduce the risk of gas leakage from old brine wells during the operation of salt cavern energy storage facilities.

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Currently, there is a lack of systematic solutions for plugging old brine wells. The common method is direct cement injection at the wellhead, which suffers from micro-annular flow problems between the outer wall of the wellbore and the original formation, resulting in poor plugging effectiveness and failing to meet the wellbore sealing integrity requirements for energy storage operation. To address this issue, this invention provides a plugging device for old brine wells in salt cavern energy storage, referencing... Figures 1-7 The system includes a casing pretreatment tool, a wellbore 20 packer tool, and a completion wellhead device. The casing pretreatment tool is used for trimming and cleaning the wellbore 20 of old brine discharge wells, and can enlarge the wellbore 20 radially to the original formation at a set position. The wellbore 20 packer tool includes a primary packer assembly and a secondary packer assembly. The primary packer assembly can seal the opening of the cavity 16 of the salt cavern energy storage and the wellbore 20 located below the enlarged area. The secondary packer assembly is located above the primary packer assembly and can seal the enlarged area of ​​the wellbore 20 to prevent micro-annular flow between the outer wall of the wellbore 20 and the original formation. An annulus is provided near the top opening of the wellbore 20, and an annulus protection fluid 22 is injected into the annulus. The completion wellhead device is located at the top opening of the wellbore 20 and is used to periodically observe and monitor the pressure changes in the annulus and inside the wellbore 20. This invention solves the micro-annular gap flow problem in traditional cement plugging by using a multi-tool collaborative operation, meets the requirements of pressure monitoring, pressure relief and fluid replenishment, and significantly improves the sealing reliability of the wellbore plugging of salt cavern energy storage.

[0026] In one embodiment, the casing pretreatment tools include a well gauge, a scraper, a milling cutter, and a reamer. The inner diameter of the well gauge is smaller than the inner diameter of the wellbore 20, and one end of the well gauge can be connected to the drill pipe 3. The drill pipe 3 can drive the well gauge into the wellbore 20 and move it up and down along the wellbore 20 to verify the patency of the wellbore 20. The scraper includes a scraper body 4, the upper end of which can be threaded to the drill pipe 3. The scraper body 4 is symmetrically arranged with forward scraper blades 1 and reverse scraper blades 2. The drill pipe 3 can lower the scraper body 4 below the intended placement position of the primary sealing component inside the wellbore 20. The scraper body 4 is repeatedly raised and lowered multiple times at the intended placement position of the primary sealing component until the weight of the scraper does not change, so as to achieve 360° full wellbore coverage scraping inside the wellbore 20 and remove the deposits on the inner wall of the wellbore 20. The milling machine includes a milling machine body 7. The lower part of the milling machine body 7 is circumferentially arranged with multiple tapered guide shoes 5. The outer side wall of the guide shoes 5 can slide against the side wall of the wellbore 20 to provide axial straightening force for the milling machine body 7. The upper part of the milling machine body 7 is circumferentially evenly distributed with inclined teeth 6. The upper end of the teeth 6 is hinged to the side wall of the milling machine body 7. The lower inner side of the teeth 6 is connected to the side wall of the milling machine body 7 by a hydraulic drive mechanism. The hydraulic drive mechanism can drive the teeth 6 to swing around the hinge point to a set position. The reamer includes a main body 10, on which multiple blades 9 are symmetrically arranged circumferentially. The upper end of the blades 9 is hinged to the side wall of the main body 10. The lower inner side wall of the blades 9 is connected to the side wall of the main body 10 through a hydraulic drive mechanism. The hydraulic drive mechanism can drive the blades 9 to swing around the hinge point to a set position. The hydraulic drive mechanism in this embodiment has the same structure and can be a hydraulic cylinder. The fixed end of the hydraulic cylinder is hinged to the side wall of the main body 10 or the side wall of the milling machine body 7. The end of the telescopic rod of the hydraulic cylinder is hinged to the lower inner side of the blades 9 or the lower inner side of the teeth 6, thereby controlling the blades 9 or teeth 6 to open or close. Alloy teeth 8 are provided on the side wall of the blades 9. The alloy teeth can radially cut the formation in the reaming area of ​​the wellbore 20 to ream the wellbore 20 to the original formation. In one specific embodiment, the well gauge has a diameter of 152 mm and is used with a drill pipe 3 with a diameter of 88.9 mm to circulate the well to the opening at the bottom of the wellbore 20; the scraper is a tubing structure with a diameter of 177.8 mm and is used with a drill pipe 3 with a diameter of 88.9 mm to scrape to below the setting position of the bridge plug 15; the forging mill is of type TDX-178 and is used with a drill pipe 3 with a diameter of 88.9 mm to forge and mill the casing of the corroded section of the wellbore 20; the reamer is of type YK144-265 and is used with a drill pipe 3 with a diameter of 88.9 mm to radially enlarge the forged section of the wellbore 20 to the original formation.

[0027] In one embodiment, the primary sealing assembly includes a bridge plug 15, which is located at the junction of the top of the cavity 16 and the bottom of the wellbore 20 to seal and separate the cavity 16 and the wellbore 20. In this embodiment, the bridge plug 15 is seated on the upper part of the cavity 16 to permanently seal the fluid channel between the cavity 16 and the wellbore 20. A cement plug 19 is provided on the top of the bridge plug 15 to form an artificial well bottom. The cement plug 19 is located below the enlarged area of ​​the wellbore 20.

[0028] In one embodiment, the secondary sealing assembly includes a metal sealing element 18 and a support element 14. The metal sealing element 18 is made of a low-melting-point alloy. After melting, the metal sealing element 18 can fill the enlarged area and seal with the in-situ formation at the enlarged area after cooling and solidification. Under a preset temperature trigger, the metal sealing element 18 melts and flows to fill the micro-gap at the interface between the wellbore 20 and the in-situ formation in the enlarged area, forming a metallurgical-grade sealing barrier. The support element 14 is made of an alloy, and the melting point of the support element 14 is greater than that of the metal sealing element 18. The metal sealing element 18 is bonded to the outer wall of the support element 14. A receiving cavity 21 is formed inside the support element 14, and the receiving cavity 21 is filled with combustible material 13. A suspension element 12 is connected to the top of the support element 14, and a cable 11 is connected to the outside of the suspension element 12. The end of the cable 11 away from the suspension element 12 is located outside the wellbore 20. An electric cable is provided inside the cable 11, and the electric cable is electrically connected to an igniter 17. The igniter 17 is located on the support element 14. The top of the support member 14 is connected to the igniter 17, which is connected to the combustible material 13. The temperature of the combustible material 13 after ignition is greater than the melting point of the metal plug 18, but lower than the melting point of the support member 14. The combustible material 13 is encapsulated in the accommodating cavity 21, and the heat released by its combustion is conducted to the metal plug 18. The igniter 17 is controlled to ignite the combustible material 13, causing the metal plug 18 to melt and flow and fill the micro-gap at the interface of the well shaft 20. The suspension member 12 is connected to the top of the support member 14 and is used for rope suspension.

[0029] In one embodiment, the completion wellhead device includes a pressure gauge 28, a main control valve 25, a blowout preventer valve 27, a pressure sensor 26, a flange 23, and a control valve 24, which are used to regularly observe and monitor the pressure changes in the annulus and the wellbore 20; the bottom of the main channel of the completion wellhead device is connected to the top casing head of the wellbore 20 of the old brine drainage well through the flange 23, and a control valve 24 is connected in series on the main channel as the main switch; a lateral channel is provided on the side wall of the main channel above the control valve 24, and a main control valve 25 is installed in the lateral channel to regulate the flow rate. The area of the main channel above the lateral channel is connected with a pressure gauge 28, a pressure sensor 26, and a blowout preventer valve 27. The blowout preventer valve 27 serves as an independent safety valve and is connected to an emergency pipeline, which is an emergency outlet for pressure relief and safety protection; the main control valve 25 and the control valve 24 are switches for controlling the on-off of the fluid, thereby regulating the flow rate in the main channel; cement is filled above the secondary plugging assembly, and the filling height of the cement reaches near the opening position at the top of the wellbore 20. The area between the top of the cement and the opening at the top of the wellbore 20 forms an annulus; the pressure gauge 28 is used to display the dynamic pressure of the wellbore 20 locally; the pressure sensor 26 is used to transmit the pressure to the pressure gauge 28 in real time; the main control valve 25 is used to cut off the gas source emergently to prevent the gas from surging up; the blowout preventer valve 27 is used to control the pressure relief in the well; the control valve 24 is used to regulate the on-off of the fluid in the annulus pressure monitoring hole; the flange 23 is used to achieve high-pressure seal connection between devices.

[0030] The present invention also provides a method for plugging the old brine drainage well of a salt cavern energy storage reservoir, which includes the following steps: Use a well gauge drill pipe 3 to run through the well to the bottom opening position of the wellbore 20 to verify the smoothness of the wellbore 20; Use a scraper to repeatedly lift and lower the scraper three times in the well section of ±5 m at the position where the primary plugging assembly is to be placed until the hook load is stable, ensuring that the wellbore wall at the setting section of the bridge plug 15 is clean; Lower the bridge plug 15 to the designed depth, conduct a hydrostatic test after hydraulic setting to verify the integrity of the primary seal; it is required that the pressure drop within 30 minutes during the pressure test of the bridge plug 15 is less than or equal to 0.5 MPa to be qualified. If the pressure test is unqualified, the bridge plug 15 should be reset. Inject a cement plug 19 above the bridge plug 15. After waiting for 48 hours, probe the cement surface and sweep away the excess cement plug 19, and conduct a pressure test on the artificial bottom hole. It is required that the pressure test on the cement plug 19 is 10 MPa and the pressure drop within 30 minutes is less than or equal to 0.5 MPa for the pressure test to be qualified. Only after the pressure test is qualified can the following operations be carried out; The corroded section of the wellbore 20 above the bridge plug 15 is subjected to segmented forging and milling and reaming to remove the damaged wellbore 20 and form a regular wellbore. The tapered guide shoe 5 at the bottom of the forging mill body 7 provides axial straightening force to suppress tool oscillation. The forging mill body 7 is circumferentially distributed with hydraulically driven teeth 6. During the forging milling process, the teeth 6 are in a closed state to reduce resistance. During the forging milling operation, hydraulic activation causes the teeth 6 to open radially, rotating and cutting the corroded casing to initially form an open hole section. The reamer body 10 is circumferentially symmetrically arranged with cutter wings 9. During the reaming process, the cutter wings 9 are closed, and their outer diameter is adapted to the forged wellbore. During the reaming operation, the cutter wings 9 are hydraulically deployed, and the alloy teeth 8 on the cutter wings 9 radially cut the formation, reaming to the original formation. The residual protrusions from the forging milling are eliminated to form a regular wellbore.

[0031] The secondary sealing assembly is lowered to the milling section. The igniter 17, triggered by a cable, ignites the combustible material 13, causing the metal sealing component 18 to melt. The molten metal flows towards the milling enlargement section under gravity and capillary action, filling the micro-annular gap at the interface between the wellbore 20 and the original formation. After natural cooling and solidification, a metallurgical bonded sealing layer is formed, permanently sealing the wellbore 20. A non-flammable rope connects to the suspension component 12, with a cable 11 connected to its upper end. The cable 11 contains an electrical cable, which is connected to the igniter 17 via a plug, allowing the igniter 17 to be energized and heated. The lower end of the igniter 17 is connected to the combustible material 13, which is placed within the receiving cavity 21 of the support component 14. The heat released by the igniter 17 reaches the ignition point of the combustible material 13, causing it to self-propagate within the receiving cavity 21 of the support component 14. The combustible material 13 here is a powdered magnesium alloy, which also contains flame retardants and binders. By adjusting the ratio between the flame retardant, binder and third metal, the combustion rate and temperature of the combustible material 13 can be effectively controlled, thereby ensuring that the heat generated by the combustion of the combustible material 13 is sufficient to completely melt and detach the metal sealing member 18 on the outside of the support member 14.

[0032] The support member 14 and the metal plug 18 are thermally connected by an adhesive bonding method, with the metal plug 18 connected to the outside of the support member 14. When the combustible material 13 burns, the support member 14 can conduct the heat released by combustion to the outer metal plug 18. Since the metal plug 18 is made of a first metal and the support member 14 is made of a second metal, and the melting point of the first metal is lower than that of the second metal, this characteristic ensures that the heat conducted to the metal plug 18 can completely melt it. The melted metal plug 18 will detach from the outside of the support member 14 and flow into the well shaft 20. At the same time, because the melting point of the support member 14 is higher, it can maintain its structure during the combustion of the combustible material 13, ensuring the stability of the entire conduction and detachment process.

[0033] It should be noted that the thickness of the metal plug 18 surrounding the outer circumferential wall of the support 14 and the thickness at the bottom of the support 14 need to vary depending on the amount of the first metal actually used, and the amount of the first metal must meet the sealing requirements of the wellbore 20 after melting.

[0034] Remove the support 14 from the wellbore 20, leaving the molten metal plug 18 in the enlarged area; After the metal plug 18 cools and solidifies, cement is injected into the wellbore 20 up to 200 meters below the top opening of the wellbore 20, and allowed to set for 48 hours. Annular protective fluid 22 is injected into the top of the cement. Based on the operating pressure of the energy storage tank, the completion wellhead equipment is selected, and pressure gauge 28 is installed to monitor the annular pressure inside the production casing and between the production casing and the outer casing, confirming the long-term stability of the seal. This meets the requirements for pressure monitoring, pressure relief, and fluid replenishment.

[0035] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A device for sealing old brine wells in salt cavern energy storage facilities, characterized in that: include: Casing pretreatment tools are used for wellbore repair and cleaning of old brine discharge wells, and can be used to enlarge the wellbore radially to the original formation at a set position. A wellbore sealing tool, comprising a primary sealing assembly and a secondary sealing assembly, wherein the primary sealing assembly is capable of sealing the cavity of the salt cavern energy storage tank and the opening at one end of the wellbore located below the enlarged area; The secondary plugging assembly is located above the primary plugging assembly and can plug the enlarged area of ​​the wellbore. An annulus is provided near the top opening of the wellbore, and an annulus protection fluid is injected into the annulus. The wellhead device is located at the top opening of the wellbore and is used to periodically observe and monitor pressure changes in the annulus and inside the wellbore.

2. The device for sealing old brine wells in salt cavern energy storage according to claim 1, characterized in that: The casing pretreatment tool includes a well gauge, the inner diameter of which is smaller than the inner diameter of the wellbore, and one end of the well gauge can be connected to the drill pipe. The drill pipe can drive the well gauge into the wellbore and move it up and down along the wellbore to verify the patency of the wellbore.

3. The device for sealing old brine wells in salt cavern energy storage according to claim 2, characterized in that: The casing pretreatment tool also includes a scraper, which includes a scraper body. The upper end of the scraper body can be threaded to the drill pipe. The scraper body is symmetrically arranged with forward and reverse scraper blades. The drill pipe can lower the scraper body below the intended placement position of the primary sealing component inside the wellbore. The scraper body is repeatedly raised and lowered multiple times at the intended placement position of the primary sealing component until the weight of the scraper does not change, so as to achieve 360° full wellbore wall coverage scraping inside the wellbore and remove the deposits on the inner wall of the wellbore.

4. The device for sealing old brine wells in salt cavern energy storage according to claim 3, characterized in that: The casing pretreatment tool also includes a milling machine, which includes a milling machine body. The lower part of the milling machine body has multiple tapered guide shoes arranged circumferentially. The outer side wall of the guide shoes can slide against the wellbore sidewall to provide axial straightening force for the milling machine body. The upper part of the milling machine body has inclined teeth evenly distributed circumferentially. The upper end of the teeth is hinged to the sidewall of the milling machine body. The lower inner side of the teeth is connected to the sidewall of the milling machine body by a hydraulic drive mechanism. The hydraulic drive mechanism can drive the teeth to swing around the hinge point to a set position.

5. The device for sealing old brine wells in salt cavern energy storage according to claim 3, characterized in that: The casing pretreatment tool also includes an reamer, which includes an reamer body with multiple blades symmetrically arranged around its circumference. The upper ends of the blades are hinged to the sidewalls of the reamer body, and the lower inner sidewalls of the blades are connected to the sidewalls of the reamer body via a hydraulic drive mechanism. The hydraulic drive mechanism can drive the blades to swing around the hinge point to a set position. The sidewalls of the blades are provided with alloy teeth, which can radially cut the formation in the wellbore reaming area to ream the wellbore reaming area back to the original formation.

6. The device for sealing old brine wells in salt cavern energy storage according to claim 1, characterized in that: The primary sealing assembly includes a bridge plug located at the junction of the top of the cavity and the bottom of the wellbore to seal and separate the cavity and the wellbore; a cement plug is provided on the top of the bridge plug to form an artificial well bottom; the cement plug is located below the enlarged area of ​​the wellbore.

7. The device for sealing old brine wells in salt cavern energy storage according to claim 1, characterized in that: The secondary sealing assembly includes a metal sealing element made of a low-melting-point alloy. After melting, the metal sealing element can fill the enlarged area and, after cooling and solidification, seal with the original stratum at the enlarged area.

8. The device for sealing old brine wells in salt cavern energy storage according to claim 7, characterized in that: The secondary plugging assembly also includes a support member made of alloy, the support member having a melting point greater than that of the metal plugging member, the metal plugging member being bonded to the outer wall of the support member; the support member has an internal cavity filled with combustible material, a suspension member connected to the top of the support member, a cable connected to the suspension member, the end of the cable away from the suspension member located outside the wellbore; the cable contains an electrical cable connected to an igniter, the igniter being located at the top of the support member and connected to the combustible material, the temperature of the combustible material after ignition being greater than the melting point of the metal plugging member but lower than the melting point of the support member.

9. The device for sealing old brine wells in salt cavern energy storage according to claim 1, characterized in that: The wellhead completion device includes a pressure gauge, a main control valve, a vent valve, a pressure sensor, a flange, and control valves. The bottom of the main channel of the wellhead completion device is connected to the top casing head of the old brine discharge well via a flange. A control valve is connected in series on the main channel as a master switch. A lateral channel is provided on the side wall of the main channel above the control valve. The main control valve is installed in the lateral channel. The pressure gauge, pressure sensor, and vent valve are connected to the area above the lateral channel of the main channel. Cement is filled above the secondary sealing assembly, and the cement filling height reaches near the top opening of the wellbore. The area between the top of the cement and the top opening of the wellbore forms the annulus. The pressure gauge is used to display the dynamic pressure of the wellbore locally. The pressure sensor is used to transmit pressure to the pressure gauge in real time. The main control valve is used to cut off the gas source in an emergency to prevent gas from rising. The vent valve is used to control the release of pressure in the well. The control valve is used to adjust the fluid flow through the annulus pressure monitoring hole.

10. A method for sealing old brine wells in salt cavern energy storage facilities, characterized in that: Includes the following steps: The well was circulated to the bottom opening position of the well using a well gauge and drill pipe to verify the well patency. Use a scraper to repeatedly lift and lower the primary plugging component at the intended placement location multiple times until the suspended weight is stable, ensuring the well wall is clean. Lower the bridge plug to the designed depth, hydraulically set the seal, and then perform a water pressure test to verify the integrity of the primary seal. The corroded section of the wellbore above the bridge plug was subjected to segmented forging and milling and enlargement to remove the damaged wellbore and form a regular wellbore. The secondary sealing component is lowered to the forging and milling section, and the combustible material is ignited by the cable-triggered igniter, causing the metal sealing component to melt and fill the micro-annular gap at the interface between the wellbore and the original formation in the enlarged area, forming a metallurgical-grade permanent seal. Remove the support components from the wellbore, leaving the molten metal plugging components in the enlarged area; After the metal plug has cooled and solidified, cement is injected into the wellbore up to below the top opening of the wellbore, and left to set for 48 hours. Annular protective fluid is injected into the top of the cement, and the wellhead equipment and pressure monitoring system are installed to continuously monitor changes in annular pressure and confirm the long-term stability of the plugging.

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