Salt cavern compressed air energy storage super-large diameter pressureless running-in string method and equipment

Abstract

The application provides a method and equipment for compressing air storage in a salt cave, and the method and equipment are used for a large-diameter pressure-free pipe string lowering device, and the method and equipment adopt an anchor insertion and setting packer, a double-stage sealing cylinder matched with the packer and a two-stage plug, after well completion, when maintenance is needed, the two-stage plug is first lowered and is respectively set and sealed, and the pressure in the upper part of the plug is released to normal pressure, the packer is released, a fault pipe string is pulled out, after a replacement pipe string is replaced, the replacement pipe string is re-lowered, is set and sealed, and is sealed, and then the two-stage plug is pulled out step by step. The application can fundamentally realize pressure-free operation of a large-diameter injection-production well, greatly reduces the material and construction cost of pipe string replacement, and significantly shortens the power station downtime caused by maintenance, thereby providing reliable technical support for safe, efficient and low-cost operation of a large-scale salt cave compressing air storage power station.

Description

Technical Field

[0001] This invention relates to the field of compressed air energy storage injection-production well completion technology, specifically to a method and equipment for running and lowering ultra-large diameter unpressurized tubing strings in a salt cavern compressed air energy storage system. Background Technology

[0002] Driven by the global "dual-carbon" strategic goal, the installed capacity of renewable energy sources, represented by wind and solar power, has grown rapidly. However, their inherent intermittency and volatility pose a severe challenge to the safe and stable operation of the power grid. Compressed air energy storage (CAES), as a large-scale, long-cycle, high-efficiency, and environmentally friendly physical energy storage technology, can effectively solve problems such as renewable energy consumption and peak shaving and valley filling in the power grid, and is one of the key supporting technologies for building a new power system.

[0003] The core principle of CAES (Carbon-Electric Gas Storage) systems is to compress and store air in underground spaces during off-peak hours or when wind and solar power are wasted, and then release the high-pressure air during peak electricity demand to drive turbines for power generation. Salt caverns, due to their large storage capacity, excellent sealing performance, and outstanding economic advantages, have become the preferred geological structure for large-scale CAES gas storage devices.

[0004] Currently, most of the 300MW and above salt cavern compressed air energy storage power plants that have been built or are under construction in China (such as projects in Jintan, Jiangsu; Yingcheng, Hubei; and Tai'an, Shandong) adopt a mature well completion model for their injection and production wells: a tubing system consisting of "large-diameter production casing + suspended injection and production tubing + hydraulic setting packer" is run into the cemented large-diameter production casing (typically φ473.1mm). The core objective of this model is to achieve a large diameter (injection and production tubing typically ≥φ339.7mm) to meet the high-flow-rate injection and production demands of millions of cubic meters per hour.

[0005] The main steps of this traditional well completion process include: 1. Assembly and lowering of the tubing: On the ground, the injection and production tubing is connected in a string with the hydraulic packer, the set-in section, the guide shoe, and other tools, and then slowly lowered into the predetermined position inside the production casing using large equipment (the packer is usually set in a stable salt rock layer 15-30 meters above the top boundary of the salt cavern).

[0006] 2. Fluid circulation and packing preparation: After the tubing is in place, pump in clean water or brine to circulate and clean the wellbore, and then drop the packing ball from the wellhead to the packer ball seat.

[0007] 3. Hydraulic pressure setting: By pressurizing the tubing, the packer setting pins are first cut off, then the slips are pushed to open radially and engage with the casing wall to achieve anchoring, and finally the rubber sleeve is compressed to expand radially and seal the annulus between the casing and the tubing.

[0008] 4. Sealing and Completion: The sealing performance is verified by pressurizing the annulus (V0 standard). Once verified, annular protective fluid (such as saturated brine with corrosion inhibitor) is introduced to complete the well completion operation.

[0009] However, the operating conditions of salt cavern compressed air energy storage power plants are extremely harsh, characterized by high-frequency injection-production cycles (up to 2-4 times per day), huge alternating pressure differentials (fluctuating between 4-5 MPa and 14-21 MPa), and a high-temperature, high-pressure environment rich in oxygen. These conditions far exceed those of traditional natural gas storage facilities, leading to a series of fatal flaws in the aforementioned traditional well completion methods. These flaws are precisely the technical bottlenecks that this invention aims to overcome: 1. Packer Sleeve "High-Frequency Breathing" Fatigue and Micro-Leakage: During the daily "gas injection-power generation" cycle, the packer is subjected to an alternating pressure difference of 8-10 MPa. This causes periodic micro-deformation of the sleeve (breathing effect), accelerating the breakage of rubber molecular chains and permanent compression deformation. After 1-2 years of operation, the sealing pressure decreases, triggering micro-leakage. The leaked oxygen-containing humid air enters the annulus, not only consuming corrosion inhibitors but also forming oxygen concentration cells, leading to pitting corrosion and perforation of the casing coupling, becoming a "chronic disease" in power plant operation. Once the sleeve seal fails, existing well completion methods can only replace the packer through live-line operations, but live-line operations in ultra-large diameter injection-production wells face extremely high safety risks and economic costs.

[0010] 2. Stress Concentration and Casing Damage from Large-Size Slips: To withstand enormous axial loads, the hardness of the packer slip teeth is much higher than that of the casing. Over a 30-year service life, the slip teeth will continuously embed into the casing wall, especially under lateral compression caused by salt rock creep, which will exacerbate the embedment depth. Simultaneously, frequent injection and production vibrations can cause the slip tooth tips to scratch micro-cracks in the casing. If the setting point happens to be at the casing coupling, it can easily lead to thread leakage or longitudinal cracking, causing catastrophic wellbore failure. After casing damage, the injection and production tubing needs to be replaced, which also requires live-line work, further increasing construction risks and costs.

[0011] 3. Risk of coupled thermo-mechanical-chemical corrosion in the wellbore: Traditional packer metal components (such as 35CrMo steel) are difficult to resist strong oxidative corrosion under high pressure (oxygen partial pressure as high as 3-4MPa) and high temperature (90-120℃), easily leading to oxidation weight gain and spalling, resulting in the failure of critical components. In addition, saturated brine in the annular protective fluid is prone to crystallization (NaCl) on the upper part of the packer when the wellbore temperature fluctuates, depositing on the unsealing mechanism, making it impossible to unseal during later major workover operations, forcing high-risk and high-cost milling operations.

[0012] 4. Risks of sediment burial and "deadlock": The packer is fixed near the top of the salt cavern, and insoluble materials that peel off from the roof during operation will continuously settle. Once the sediment height exceeds the injection / production pipe opening, it will bury the packer and the bottom of the tubing, making subsequent gas production profile testing or downhole detection impossible. More seriously, the compaction of the sediment will generate huge external extrusion forces, which may crush the injection / production tubing, causing a paralyzed situation where the power plant can only inject but not produce.

[0013] 5. Lack of emergency shut-off capability: Traditional well completion methods rely solely on surface valves and packers for static sealing as a safety barrier. If the surface gas tree is damaged due to accidents such as earthquakes or external impacts, high-pressure air will rush straight to the surface along the wellbore. At this time, the packer located at the bottom of the well cannot achieve rapid shut-off downhole, lacking a second physical safety barrier, which is far from meeting the extremely high requirements of "intrinsic safety" for new energy storage power stations.

[0014] In summary, existing well completion technologies can no longer meet the stringent requirements of salt cavern compressed air energy storage power stations for safety, economy, and maintainability. There is an urgent need to invent a novel well completion process and device that can fundamentally achieve non-pressurized operation of ultra-large diameter injection and production wells, significantly reduce the material and construction costs of tubing replacement, and substantially shorten power station downtime due to maintenance and repairs. This would provide a reliable technical guarantee for the safe, efficient, and low-cost operation of large-scale salt cavern compressed air energy storage power stations. Summary of the Invention

[0015] In view of this, the present invention provides a method and equipment for raising and lowering ultra-large diameter injection and production wells without pressure in salt cavern compressed air energy storage, which can fundamentally realize the operation of ultra-large diameter injection and production wells without pressure, significantly reduce the material and construction costs of tubing replacement, and significantly shorten the power station downtime caused by maintenance and repair, thereby providing a reliable technical guarantee for the safe, efficient and low-cost operation of large-scale salt cavern compressed air energy storage power stations.

[0016] The technical solution adopted in this invention is as follows: A method for raising and lowering an ultra-large diameter tubing string without pressure in a salt cavern compressed air energy storage system, comprising the following steps: Step 1: Complete the first drilling and first casing cementing in sequence; fix the double-stage sealing cylinder to the inner wall of the end of the second casing string and lower it to the bottom of the well. Step two: Cementing operation is performed on the two-stage casing string; Step 3: The anchored insert packer is fixed to the end of the injection-production tubing and lowered into the well along with the tubing; when lowered to the designed depth, ensure that the anchored insert packer corresponds to the position of the dual-stage sealing cylinder; Step 4: Complete the setting and verification of the anchored insert packer; Step 5: When maintenance is required, send the first-stage plug into the sealing cavity of the double-stage sealing cylinder to complete the setting and sealing verification operations; Step 6: Insert the second-stage plug above the first-stage plug to complete the setting and sealing of the second-stage plug. Step 7: Release the pressure in the wellbore above the second-stage plug to atmospheric pressure; Step 8: Unseal the anchored insert packer and remove the faulty string; Step 9: Reassemble the repaired or replaced injection / production tubing with the anchored insertion packer to form a new tubing string; Step 10: Lower the new tubing into the well. Repeat steps 3 and 4 to reseat the anchored insert packer inside the double-stage sealing cylinder and complete the seal verification. Separately unseal and remove the second-stage and first-stage plugs.

[0017] Furthermore, the dual-stage sealing cylinder is threadedly connected to the inner wall of the end of the two-sleeve pipe column; The anchored insert packer is threaded to the end of the injection / production tubing.

[0018] Furthermore, the internal structure of the dual-stage sealing cylinder is a three-stage stepped structure. The section with the largest inner diameter is the anchoring and mounting section, which is used to cooperate with the anchoring slip assembly of the anchoring insert packer; the middle section is the sealing matching section, which is used to cooperate with the sealing sleeve of the anchoring insert packer; and the section with the smallest inner diameter is the plugging and sealing section, which has two sealing cavities, used to cooperate with the first-stage plug and the second-stage plug respectively.

[0019] Furthermore, in step four, the setting process of the anchored insert packer is as follows: Hydraulic or mechanical force is applied through the oil pipe to drive the insert packer to move, its anchoring slip assembly opens and anchors to the anchoring seat section of the two-stage sealing cylinder; at the same time, the sealing sleeve assembly expands and forms a metal / elastic composite seal with the sealing matching section.

[0020] Furthermore, in step four, the effectiveness of the seal of the anchored insert packer is verified by annular pressure testing.

[0021] Furthermore, in step five, the setting and sealing process of the first-stage blocker is as follows: The first-stage plug is delivered to the lower sealing chamber of the downhole double-stage sealing cylinder via drill pipe or coiled tubing, and mechanically set by rotating and pressurizing it on the surface.

[0022] Furthermore, in step six, the setting operation of the second-stage plug is the same as that of the first-stage plug, sealing and fixing the second-stage plug in the upper sealing cavity of the double-stage sealing cylinder.

[0023] The present invention also provides a device for raising and lowering ultra-large diameter unpressurized tubing for salt cavern compressed air energy storage, which is applied to the above-mentioned method for raising and lowering ultra-large diameter tubing for salt cavern compressed air energy storage. The device includes an anchored insertion packer, a two-stage sealing cylinder, a first-stage plugger, and a second-stage plugger. The anchoring insert packer includes an anchoring slip assembly and a sealing sleeve assembly. The dual-stage sealing sleeve is threaded to the inner wall of the end of the two-stage casing string, serving as the downhole fixed interface for all subsequent setting and plugging operations. The internal structure of the dual-stage sealing sleeve is a three-stage stepped structure. The section with the largest inner diameter is the anchoring and setting section, used to mate with the anchoring slip assembly of the anchoring insert packer. The middle section is the sealing matching section, used to mate with the sealing sleeve. The section with the smallest inner diameter is the plugging and sealing section, which has two sealing cavities for mates with the first-stage plugger and the second-stage plugger, respectively.

[0024] Beneficial effects: 1. The well completion process of this invention enables packer replacement and injection / production tubing tripping operations in ultra-large diameter (≥φ339.7mm) injection-production wells with compressed air energy storage and hydrogen storage in salt caverns under normal pressure. This completely avoids extreme safety accidents such as well blowouts and high-pressure tubing ejection faced by traditional pressurized operations, and solves the long-standing industry problem of low technical maturity and uncontrollable safety in pressurized operations of ultra-large diameter injection-production wells.

[0025] 2. This invention can form two safety barriers underground, enabling rapid shutdown underground in the event of extreme events such as damage to the surface gas production tree, thus significantly improving the inherent safety level of the power plant.

[0026] 3. Because this invention allows for periodic replacement of injection and production tubing under normal pressure, it eliminates the need for expensive nickel-based alloys (such as Inconel 625) or high-cost corrosion protection solutions like laser cladding welding, reducing tubing material costs to 1 / 8 to 1 / 10 of traditional methods. This invention also eliminates the requirement for packer sleeves to maintain a 30-year lifespan under high temperature, high pressure, high salt, and high-frequency cyclic loading. The packer can be replaced along with the tubing at low cost after a certain operating cycle, completely avoiding chronic failures such as micro-leakage and annular corrosion caused by fatigue failure due to the "high-frequency breathing" of the packer sleeve, thus reducing power plant operation and maintenance risks. The cost of live-line operations for traditional small-diameter injection and production wells has reached tens of millions of yuan, and the cost for live-line operations for ultra-large-diameter wells is astronomical. After achieving normal pressure operation with this invention, the construction difficulty and cost are significantly reduced, and the cost of a single tubing replacement can be reduced by more than 80%.

[0027] 4. This invention allows for the installation and removal of tubing and packers under normal pressure conditions, eliminating the need for complex pressurized equipment and lengthy pressure balancing procedures. This simplifies the construction process, significantly reduces construction time, and substantially lowers the economic losses caused by power plant shutdowns due to well maintenance and repairs. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the ultra-large diameter well structure and equipment for salt cavern compressed air energy storage according to the present invention.

[0029] Figure 2 This is a schematic diagram and exploded view of the equipment for ultra-large diameter unpressurized lowering of tubing in salt cavern compressed air energy storage according to the present invention.

[0030] Figure 3 This is a schematic diagram of a normal well completion procedure.

[0031] Figure 4 This is a schematic diagram of the process of running the tubing string without pressure in an ultra-large diameter injection-production gas well.

[0032] Among them, 1-conduit; 2-first opening; 3-second opening; 4-anchored insertion packer; 5-double-stage sealing cylinder; 6-first-stage plug; 7-second-stage plug; 8-third opening; 9-salt cavern gas storage. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] This invention provides a method for setting up and dropping tubing strings for ultra-large diameter compressed air energy storage in salt caverns without pressure. It is particularly suitable for ultra-large diameter injection-production gas wells with injection / production tubing / center tubing dimensions of 339.7 mm and above, applicable to frequent injection / production or severely corroded conditions. Regarding current permanently set packers, this invention employs an anchored insertion packer, a matching two-stage sealing cylinder 5, and a two-stage plug. The steps of this method are as follows: Step 1: Wellbore structure construction and key interface installation A schematic diagram of the wellbore structure of an ultra-large diameter gas injection-production well is shown below. Figure 1 As shown, a three-section wellbore structure is adopted, consisting of guide pipe 1, section 2 (first section), section 3 (second section), and section 8 (third section) / open hole section. Section 8 is connected to the salt cavern gas storage 9. Figure 3 As shown, drilling of guide pipe 1, first-stage casing 2, and cementing of first-stage casing are completed sequentially. Then, second-stage casing 3 is drilled to the designed depth. At the end of the first second-stage casing (i.e., the one at the bottom of the wellhead) in this second-stage (second-stage 3) drilling, a double-stage sealing cylinder 5 is threadedly connected and lowered into the well along with the entire second-stage casing string (composed of several threaded second-stage casings). This double-stage sealing cylinder 5 will serve as a permanent downhole fixed interface for all subsequent setting and plugging operations.

[0035] Step 2, well completion fixing of the fixed interface Conventional cementing operations were performed on the two-stage casing string connected in series with the dual-stage sealing cylinder 5. After cementing, the dual-stage sealing cylinder 5 was permanently fixed at the predetermined depth at the bottom of the well, becoming part of the two-stage casing. Other conventional completion operations were then completed.

[0036] Step 3: The injection / production tubing and anchored insert packer 4 are lowered into the system. Connect the upper connector of the anchoring insert packer 4 (which consists of an anchoring slip assembly and a sealing sleeve assembly) to the threaded end of the injection / production tubing, and lower it into the well along with the entire injection / production tubing string. When lowering to the designed depth, ensure that the anchoring slip assembly of the anchoring insert packer 4 is aligned with part a (anchoring and mounting section) of the downhole dual-stage sealing cylinder 5, and that the sealing sleeve assembly is aligned with part b (sealing and matching section) of the dual-stage sealing cylinder 5.

[0037] Step 4: Setting and verifying the anchored insert packer 4 Hydraulic or mechanical force is applied through the tubing (or dedicated pipeline) to drive the anchored insert packer 4 to actuate. Its anchoring slip assembly expands and anchors at point a of the dual-stage sealing cylinder 5; simultaneously, the sealing sleeve assembly expands, forming a metal / elastic composite seal with point b. After setting, the sealing effectiveness of the anchored insert packer 4 is verified through annular pressure testing to ensure reliable isolation between the injection / production tubing and the second-stage casing annulus. At this point, the wellbore enters normal injection / production production.

[0038] Step 5: Setting and verifying the first-stage plug 6 When maintenance work is required (such as corrosion perforation of the injection / production pipe inner wall, annular pressure, or gas tree malfunction), the first-stage plug 6 is first inserted into the gas tree tubing channel (rotary insertion). Figure 4 As shown, the first-stage plug 6 is delivered to the second-stage sealing chamber of the downhole double-stage sealing cylinder 5 (located below the anchored insert packer 4) via a thin drill pipe or coiled tubing. Using a setting tool, the first-stage plug 6 is mechanically set through surface rotation and pressurization, forming the first barrier, i.e., the first-stage barrier. Subsequently, the tubing above the first-stage plug 6 is pressure tested to verify its sealing performance. Then, the setting tool is hydraulically or mechanically released according to the design. Next, the injection and production tubing cavities and the annulus are pressure tested and maintained step-by-step according to standard procedures to confirm the reliability of the first-stage barrier and its isolation of the lower reservoir pressure.

[0039] Step Six: Second-stage plug 7 sets and provides double protection To address extreme situations (such as unexpected failure of the first-stage plug 6) and provide a redundant safety barrier, this invention employs a dual-stage plugging design. After successful verification in the first step, the second-stage plug 7 is inserted into the shallower part of the same dual-stage sealing cylinder 5 (the first-stage sealing cavity) or through another dedicated setting step. Its setting, verification, pressure testing, and release procedures are consistent with the operation of the first-stage plug 6 in step five. Together, the two-stage plugs constitute a "double insurance" to prevent gas from escaping upwards within the salt cavern gas storage tank 9.

[0040] Step 7: Establishing a depressurized and pressureless environment in the wellbore. After the second-stage plug 7 was set and the upper tubing string passed pressure testing, it was confirmed that the wellbore was completely isolated from the high pressure of the lower reservoir. Through a controlled depressurization procedure, the pressure in the wellbore above the two-stage plugs was safely released to atmospheric pressure. At this point, the injection and production wellbore (up to the top plug, i.e., the first-stage plug 6 in the first-stage sealing chamber) was in a pressureless or atmospheric pressure state, providing a safe environment for subsequent tubing string running operations.

[0041] Step 8: Unseal the anchored insert packer 4 and remove the faulty tubing. After confirming that the wellbore was depressurized, the anchoring and sealing of the anchored packer 4 were released by lifting the tubing string and rotating it. Subsequently, the connected injection and production tubing string, the anchored packer 4, and the gas production tree and other upper components were safely pulled to the surface.

[0042] Step 9: Ground inspection and tubing replacement Inspect, repair, or replace the removed injection and production tubing, anchored packer 4, and gas tree. Reassemble the repaired or brand-new injection and production tubing with the anchored packer 4 into a tubing string.

[0043] Step 10: Re-insert the tubing and restore the wellbore to its original state. Run the new tubing string into the well, and repeat steps three and four to re-set the anchored insert packer 4 within the original double-stage sealing cylinder 5, and complete the seal verification. After confirming that the production channel has been restored to a seal, use specialized tools to sequentially run in and remove the second-stage unsealing plug 7 and the first-stage plug 6. Finally, restore the wellhead equipment, and the wellbore can then regain its injection and production capacity or begin preparations for the next round of operations.

[0044] This invention also provides a device for raising and lowering ultra-large diameter unpressurized tubing strings in salt cavern compressed air energy storage, which enables the gas storage facility to raise and lower tubing strings and packers under normal pressure while in operation. Figure 2 As shown, the device includes an anchored insert packer 4, a two-stage sealing cylinder 5, a first-stage plugger 6, and a second-stage plugger 7.

[0045] The anchored insert packer 4 includes an anchoring slip assembly and a sealing sleeve assembly.

[0046] The double-stage sealing cylinder 5 is threaded to the inner wall of the end of the two-stage casing string, serving as a permanent downhole fixed interface for all subsequent setting and plugging operations. The double-stage sealing cylinder 5 has a three-stage stepped structure inside. The section with the largest inner diameter is the anchoring and setting section, which is used to cooperate with the anchoring slip assembly of the anchoring insert packer 4; the middle section is the sealing matching section, which is used to cooperate with the sealing rubber sleeve; and the section with the smallest inner diameter is the plugging and sealing section, which has two sealing cavities, used to cooperate with the first-stage plugger 6 and the second-stage plugger 7 respectively.

[0047] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for large-diameter pressureless running-in of a string in a salt cavern compressed air energy storage, characterized in that, The steps are as follows: Step 1: Complete the first drilling and first casing cementing in sequence; fix the double-stage sealing cylinder to the inner wall of the end of the second casing string and lower it to the bottom of the well. Step two: Cementing operation is performed on the two-stage casing string; Step 3: The anchored insert packer is fixed to the end of the injection-production tubing and lowered into the well along with the tubing; when lowered to the designed depth, ensure that the anchored insert packer corresponds to the position of the dual-stage sealing cylinder; Step 4: Complete the setting and verification of the anchored insert packer; Step 5: When maintenance is required, send the first-stage plug into the sealing cavity of the double-stage sealing cylinder to complete the setting and sealing verification operations; Step 6: Insert the second-stage plug above the first-stage plug to complete the setting and sealing of the second-stage plug. Step 7: Release the pressure in the wellbore above the second-stage plug to atmospheric pressure; Step 8: Unseal the anchored insert packer and remove the faulty string; Step 9: Reassemble the repaired or replaced injection / production tubing with the anchored insertion packer to form a new tubing string; Step 10: Lower the new tubing into the well. Repeat steps 3 and 4 to reseat the anchored insert packer inside the double-stage sealing cylinder and complete the seal verification. Separately unseal and remove the second-stage and first-stage plugs.

2. The salt cavern compressed air energy storage super large diameter snubbing method of claim 1, wherein, The dual-stage sealing cylinder is threadedly connected to the inner wall of the end of the two-sleeve column. The anchored insert packer is threaded to the end of the injection / production tubing.

3. The method for raising and lowering a large-diameter, pressureless tubing string using salt cavern compressed air energy storage as described in claim 1, characterized in that... The internal structure of the dual-stage sealing cylinder is a three-stage stepped structure. The section with the largest inner diameter is the anchoring and mounting section, which is used to cooperate with the anchoring slip assembly of the anchoring insert packer; the middle section is the sealing matching section, which is used to cooperate with the sealing rubber sleeve of the anchoring insert packer; and the section with the smallest inner diameter is the plugging and sealing section, which has two sealing cavities, used to cooperate with the first-stage plug and the second-stage plug respectively.

4. The method for raising and lowering an ultra-large diameter unpressurized tubing string for salt cavern compressed air energy storage as described in claim 3, characterized in that, In step four, the setting process of the anchored insert packer is as follows: Hydraulic or mechanical force is applied through the oil pipe to drive the insert packer to move, its anchoring slip assembly opens and anchors to the anchoring seat section of the two-stage sealing cylinder; at the same time, the sealing sleeve assembly expands and forms a metal / elastic composite seal with the sealing matching section.

5. The method for raising and lowering an ultra-large diameter unpressurized tubing string for salt cavern compressed air energy storage as described in claim 3, characterized in that, In step four, the effectiveness of the seal of the anchored insert packer is verified by annular pressure testing.

6. The method for raising and lowering an ultra-large diameter unpressurized tubing string for salt cavern compressed air energy storage as described in claim 1 or 3, characterized in that, In step five, the setting process of the first-stage blocker is as follows: The first-stage plug is delivered to the lower sealing chamber of the downhole double-stage sealing cylinder via drill pipe or coiled tubing, and mechanically set by rotating and pressurizing it on the surface.

7. The method for raising and lowering an ultra-large diameter unpressurized tubing string for salt cavern compressed air energy storage as described in claim 6, characterized in that, In step six, the setting operation of the second-stage plug is the same as that of the first-stage plug, and the second-stage plug is sealed and fixed in the upper sealing cavity of the double-stage sealing cylinder.

8. A device for raising and lowering an ultra-large diameter unpressurized tubing string using compressed air energy storage in a salt cavern, characterized in that, The device, which is applied to the method for raising and lowering a large-diameter unpressurized tubing for salt cavern compressed air energy storage as described in any one of claims 1-7, includes an anchored insertion packer, a two-stage sealing cylinder, a first-stage plugger, and a second-stage plugger. The anchoring insert packer includes an anchoring slip assembly and a sealing sleeve assembly. The dual-stage sealing sleeve is threaded to the inner wall of the end of the two-stage casing string, serving as the downhole fixed interface for all subsequent setting and plugging operations. The internal structure of the dual-stage sealing sleeve is a three-stage stepped structure. The section with the largest inner diameter is the anchoring and setting section, used to mate with the anchoring slip assembly of the anchoring insert packer. The middle section is the sealing matching section, used to mate with the sealing sleeve. The section with the smallest inner diameter is the plugging and sealing section, which has two sealing cavities for mates with the first-stage plugger and the second-stage plugger, respectively.

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