Protection structure for neck section of salt cavern rebuilt from existing cavern and construction method of protection structure

Abstract

The invention discloses an existing salt cavern reservoir neck section protection structure and a construction method thereof.The structure comprises a tail pipe and a sealing mechanism, the tail pipe comprises a tail pipe body, a hanging assembly and a lower connecting part, and through the special design and synergistic effect of the tail pipe and the sealing mechanism, the neck section can be protected in all directions. On one hand, the suspension type tail pipe is installed on the neck section, creep shrinkage of the neck section is effectively limited, the risk that the neck is closed or even collapsed is avoided, meanwhile, through the structural design, it is guaranteed that the tail pipe is not snapped under the salt cavern creep stretching effect, the stability of the tail pipe in the injection and production process is improved, and the service life of the tail pipe is prolonged. Safe and stable operation of the salt cavern storage cavern is guaranteed; and on the other hand, through the combined action of the tail pipe and the sealing mechanism, a relatively closed space is formed on the inner side wall of the neck section, the risks of air flow sand carrying and gas leakage caused by the too long neck section are reduced, then abrasion of sand-carrying air flow impact to a shaft is reduced, and the service life of equipment is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of salt cavern storage construction, and in particular to a protective structure for the neck section of a salt cavern storage converted from an existing dissolution cavity and a construction method thereof. Background Art

[0002] As a type of underground energy storage facility, salt caverns are widely used for storing energy sources such as natural gas, compressed air, and hydrogen due to their excellent sealing properties and high gas storage safety. Existing technologies for converting dissolution cavities into salt cavern storage facilities are available, transforming dissolution cavities left behind after salt mining into facilities for storing natural gas and other energy sources. my country has a large number of abandoned old caverns, and conversion can effectively shorten storage construction time and reduce investment. However, due to long-term water injection and outdated mining technology, existing dissolution caverns have complex wellbore structures and poor wellbore stability. During the conversion process, the old wells often need to be sealed and new wells dug for injection and production. During the excavation of the new well, drilling is typically stopped 30-50 meters from the cavern ceiling to complete cementing and prevent drilling mud from entering the salt cavern. After cementing is completed, drilling is resumed until the well is connected to the salt cavern. This operation creates an openhole section between the production casing shoe and the salt cavern ceiling, known as the "neck." In existing salt cavern storage well structural designs, a neck is generally required to isolate the deformation zone at the cavity top from the metal casing to prevent the casing from being damaged. However, in the process of converting existing dissolution cavities into gas storage, the neck section may be longer. While this section plays a certain buffering role, it also increases the possibility of safety hazards:

[0003] 1. Risk of sand carrying during gas production: During the natural gas or compressed air production process, the risk of sand carrying in the airflow will increase significantly, which is very likely to cause wear and tear on production equipment in the wellbore and even cause equipment blockage.

[0004] 2. Risk of neck shrinkage in the neck section: Given the high creep characteristics of salt rock, the neck section, like a cavity, will continue to creep and shrink due to its internal fluid pressure being lower than the formation stress. Neck shrinkage is a common risk in salt rock underground gas storage during operation. Especially in the high temperature and high ground pressure environment of ultra-deep salt cavern storage, the deformation of the neck section will be more severe. During the operation of the storage tank, once the neck section closes, the gas production capacity will decrease, reducing the use value and economic benefits of the storage tank. In severe cases, it may even cause the collapse of the open hole section, ultimately causing the storage tank to fail and resulting in huge economic losses.

[0005] 3. Gas leakage risk in interlayers: Gas leakage is prone to occur in interlayers in the neck section, which not only wastes energy but also poses a safety hazard to the surrounding environment and facilities.

[0006] Current technologies for converting dissolved cavities into gas storage inevitably create neck sections. To effectively prevent the risks of sand carryover, necking, and gas leakage from interlayers in these sections, a new wellbore structure design is urgently needed to provide comprehensive protection for the neck section and ensure the safe and efficient operation of salt cavern storage. Summary of the Invention

[0007] The purpose of the present invention is to overcome the above-mentioned technical deficiencies and propose a protective structure for the neck section of a salt cavern storage converted from an existing dissolution cavity and a construction method thereof, so as to solve the technical problems in the prior art such as sand carried in the neck section during the gas production stage causing wear and blockage of wellbore equipment, necking and closure due to creep of salt rock, thereby reducing gas production capacity and storage efficiency, and gas easily leaking from the interlayer, resulting in energy waste and safety hazards.

[0008] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0009] The present invention provides a protective structure for the neck section of a salt cavern reservoir converted from an existing dissolution cavity, comprising:

[0010] The tail pipe comprises a tail pipe body, a suspension assembly and a lower connecting portion, the suspension assembly being nested and connected to the top end of the tail pipe body, with a sliding space reserved therebetween, and axial displacement can occur when the tensile stress between the two reaches a certain threshold, a first protruding bayonet is provided at the end of the tail pipe to limit the maximum axial displacement of the suspension assembly, the lower connecting portion comprising an extension sleeve, the extension sleeve being nested and connected to the bottom end of the tail pipe body, with a sliding space reserved therebetween, and axial displacement can occur when the tensile stress between the two reaches a certain threshold, a second protruding bayonet is provided at the end of the tail pipe to limit the maximum axial displacement of the extension sleeve, and a plurality of mounting holes are uniformly opened on the side wall of the extension sleeve along the circumferential direction; and,

[0011] The sealing mechanism includes a first sealing ring, a flexible connector and a plurality of clamping components. The flexible connector is annular, an inner ring of which is fixed to the extension sleeve, and an outer ring of which is fixedly connected to the first sealing ring. The plurality of clamping components are respectively fixed to the corresponding mounting holes and are used to press the first sealing ring so that the first sealing ring is sealed and fits tightly against the inner wall of the neck segment.

[0012] In some embodiments, a blocking convex ring is formed at the lower end of the production casing, and a plurality of first fixing holes are formed on the inner side wall of the lower end of the production casing;

[0013] The suspension assembly includes an upper ring body, several first clamping blocks, several first elastic members and a sealing ring, the upper ring body is coaxially fixed to the upper end of the tail pipe body, and the outer side wall of the upper ring body is provided with several first accommodating grooves corresponding to the first fixing holes, the first clamping block is slidably arranged in the corresponding first accommodating grooves, one end of the first elastic member is fixed in the first accommodating groove, the other end of the first elastic member is fixed to one end of the first clamping block, and the other end of the first clamping block is used to be inserted into the corresponding first fixing hole, and the sealing ring is embedded between the upper ring body and the blocking convex ring. When the other end of the first clamping block is inserted into the corresponding first fixing hole, the sealing ring is in a compressed state.

[0014] In some embodiments, a first inclined surface and a first vertical surface are formed on one end of the first clamping block facing the first fixing hole, and the first vertical surface is used to abut against the inner top surface of the first fixing hole.

[0015] In some embodiments, the suspension assembly includes an upper ring body, an air passage is formed in the upper ring body, and the suspension assembly also includes an annular cylinder, several pistons and a one-way valve. The annular cylinder is fixedly sleeved on the upper ring body, and a closed inflation chamber is formed in the annular cylinder. An air inlet connected to the inflation chamber is provided on the upper end surface of the annular cylinder, and the air inlet is connected to the air passage. Several expansion grooves are provided on the side wall of the annular cylinder, and each piston seal is slidably arranged in the corresponding expansion groove and is used to abut against the inner wall of the production casing to be clamped in the production casing. The one-way valve is arranged in the air inlet.

[0016] In some embodiments, the sealing mechanism further includes a second sealing ring, which is fixed to the end of the extension sleeve, and the inner ring of the flexible connector is fixedly connected to the second sealing ring.

[0017] In some embodiments, the flexible connector is a rubber flexible connector.

[0018] In some embodiments, the inner side wall of the mounting hole is further provided with a plurality of second fixing holes;

[0019] The clamping assembly includes a clamping rod, a plurality of second clamping blocks and a plurality of second elastic members, the clamping rod corresponding to the mounting hole one-to-one, the clamping rod being slidably inserted into the corresponding mounting hole, a plurality of second accommodating grooves corresponding to the second fixing holes being opened on the outer side wall of the clamping rod, the second clamping block being slidably arranged in the corresponding second accommodating groove, one end of the second elastic member being fixed in the second accommodating groove, the other end of the second elastic member being fixed to one end of the second clamping block, the other end of the second clamping block being used to be inserted into the corresponding second fixing hole, and when the other end of the second clamping block is inserted into the corresponding second fixing hole, the first sealing ring is in a clamped state.

[0020] In some embodiments, a second inclined surface and a second vertical surface are formed on one end of the second clamping block facing the second fixing hole, and the second vertical surface is used to abut against the inner side wall of the second fixing hole away from the first sealing ring.

[0021] The present invention also provides a construction method for converting an existing dissolution cavity into a salt cavern reservoir neck section protection structure, which is applicable to the construction method for converting an existing dissolution cavity into a salt cavern reservoir neck section protection structure and includes the following steps:

[0022] S1. First, secure the suspension assembly to the upper end of the tail pipe body. Then, install the extension sleeve of the lower connection portion and secure it securely to the lower end of the tail pipe body. Then, install each clamping assembly into the corresponding mounting hole, ensuring that the clamping assembly can move flexibly to prepare for subsequent clamping operations.

[0023] S2. Use a lifting device to hoist the pre-installed liner as a whole and slowly place it into the production casing of the salt cavern reservoir. During the placement process, pay close attention to the position and direction of the liner to ensure that the liner can enter the production casing smoothly. When the liner suspension assembly moves down to the lower end of the production casing, seal and secure the suspension assembly to the lower end of the production casing.

[0024] S3. After the connection between the tail pipe and the production casing is completed, the compression operation of the sealing mechanism is started. Each compression component is operated to expand outward and gradually compress the first sealing ring. As the compression components are continuously compressed, the outer diameter of the first sealing ring gradually increases until the first sealing ring is tightly fitted with the inner side wall of the top neck section of the salt cavern storage cavity, achieving a good sealing effect;

[0025] S4. After completing the tightening operation of the sealing mechanism, conduct a comprehensive inspection of the tail pipe protection structure to check whether the connection between the tail pipe and the production casing is firm and whether the seal is good; check the fit between the first sealing ring and the inner wall of the neck section to ensure that the sealing effect meets the design requirements. After inspection and testing, confirm that the tail pipe protection structure is installed correctly and performs well, and then complete the entire installation work.

[0026] Compared with the prior art, the protective structure for the neck section of a salt cavern reservoir converted from an existing dissolution cavity and the construction method thereof provided by the present invention have the following beneficial effects:

[0027] (1) Reduce the risk of sand carrying during the gas production phase: The tail pipe and the sealing mechanism work together to form a relatively closed space on the inner wall of the neck section. The first sealing ring is in close contact with the inner wall of the neck section, reducing the possibility of sand carrying by the airflow, thereby reducing the wear of the production equipment in the wellbore caused by the impact of the sand-carrying airflow, effectively avoiding equipment blockage and extending the service life of the equipment;

[0028] (2) Avoid the risk of neck shrinkage: The tail pipe has a stronger anti-extrusion capability than the production casing, and a layer of buffer material is provided on the outer wall of the tail pipe. When the neck section creeps and shrinks and contacts the tail pipe, the presence of the buffer material makes the tail pipe more evenly stressed. The strong anti-extrusion capability of the tail pipe itself effectively limits the shrinkage and deformation of the neck section, thereby avoiding the risk of neck section closure and collapse, improving the stability of the salt cavern storage during operation, and ensuring the gas production capacity and economic benefits of the storage;

[0029] (3) Reduce the risk of gas leakage in the interlayer: The first sealing ring fits tightly against the inner wall of the neck section, forming an effective sealing barrier. The setting of the sealing mechanism prevents the gas in the interlayer stratum from leaking through the neck section to the surrounding rock to a certain extent, which not only reduces energy waste but also reduces the safety risks to the surrounding environment and facilities;

[0030] (4) Ensure the stability of the tail pipe: The sealing mechanism at the end of the tail pipe can not only effectively isolate the inner wall of the neck section, but also provide a certain constraint for the tail pipe from a mechanical point of view, avoiding the shaking of the tail pipe under the conditions of injection and production in the salt cavern reservoir, and ensuring the stability of the injection and production process; the tail pipe and the suspension assembly and the lower connection part are all nested, which can allow the entire structure to undergo controllable tensile deformation under the action of salt cavern creep contraction, avoiding the overall tensile fracture of the tail pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a salt cavern storage structure in related technology;

[0032] Figure 2 This is a schematic structural diagram of a protective structure for the neck section of a salt cavern reservoir converted from an existing dissolution cavity, provided by one embodiment of the present invention;

[0033] Figure 3 yes Figure 2 A partial enlarged view of the middle area A;

[0034] Figure 4 yes Figure 2 A partial enlarged view of the middle area B;

[0035] Figure 5 yes Figure 4 A partial enlarged view of the middle area C;

[0036] Figure 6 yes Figure 2 Schematic diagram of the installation process of the protective structure of the neck section of the salt cavern storage converted from an existing dissolution cavity;

[0037] Figure 7 yes Figure 6 A partial enlarged view of the middle area D;

[0038] Figure 8 This is a schematic structural diagram of a protective structure for the neck section of a salt cavern reservoir converted from an existing dissolution cavity, provided by another embodiment of the present invention;

[0039] Figure 9 yes Figure 8 A partial enlarged view of the middle area E;

[0040] Explanation of the accompanying drawings: 1-tail pipe, 11-tail pipe body, 12-suspension assembly, 121-upper ring body, 1211-air duct, 122-first clamping block, 123-first elastic member, 124-sealing ring, 125-annular cylinder, 126-piston, 127-one-way valve, 13-lower connecting part, 131-extension sleeve, 1311-second fixing hole, 2-sealing mechanism, 21-first sealing ring, 22-flexible connecting body, 23-pressing assembly, 231-pressing rod, 232-second clamping block, 233-second elastic member, 24-second sealing ring, 3-production casing, 31-blocking convex ring, 32-first fixing hole, 4-hanging device, 5-pushing mechanism, 51-hanging rod, 52-cone head, 6-injection and production pipe, 7-buffer material. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0042] In order to solve the technical problems in the prior art such as sand carried by the neck section during the gas production stage causing wear and blockage of wellbore equipment, neck shrinkage and closure of the neck section due to salt rock creep, thereby reducing gas production capacity and storage efficiency, and gas leakage from interlayers, the present invention provides a neck section protection structure for salt cavern storage converted from an existing dissolution cavity, which can provide all-round protection for the neck section to ensure the safe and efficient operation of the salt cavern storage.

[0043] See also Figure 2-Figure 8 , Figure 2Schematic diagram of the structure of the neck section protection structure of the salt cavern reservoir converted from an existing dissolution cavity in one embodiment of the present invention. The neck section protection structure of the salt cavern reservoir converted from an existing dissolution cavity includes a tail pipe 1 and a sealing mechanism 2.

[0044] The tail pipe 1 includes a tail pipe body 11, a suspension component 12 and a lower connecting portion 13. The suspension component 12 is nested and connected to the top end of the tail pipe body 11, and a sliding space is reserved between the suspension component 12 and the tail pipe body 11. When the tensile stress applied to the tail pipe body 11 reaches a certain threshold, a certain relative displacement can occur between the suspension component 12 and the upper end of the tail pipe body 11 to prevent damage. The lower connecting portion 13 includes an extension sleeve 131, which is nested and connected to the lower end of the tail pipe body 11. A sliding space is reserved between the extension sleeve 131 and the lower end of the tail pipe body 11. When the tensile stress applied to the tail pipe body 11 reaches a certain threshold, a certain relative displacement can occur between the extension sleeve 131 and the lower end of the tail pipe body 11 to prevent damage. A plurality of mounting holes are evenly opened on the side wall of the extension sleeve 131 along the circumference of the extension sleeve 131. In this embodiment, the inner diameter of the tail pipe 1 is between the production casing 3 and the injection and production pipe 6. A layer of buffer material is provided on the outer wall of the tail pipe 1 to uniformly apply force to the tail pipe 1 when the neck section contracts and contacts the tail pipe 1.

[0045] The sealing mechanism 2 includes a first sealing ring 21, a flexible connector 22 and a plurality of clamping components 23. The flexible connector 22 is annular, its inner ring is fixed to the extension sleeve 131, and its outer ring is fixedly connected to the first sealing ring 21. The plurality of clamping components 23 are respectively fixed to the corresponding mounting holes and are used to press against the first sealing ring 21 so that the first sealing ring 21 is sealed and fits against the inner wall of the neck segment.

[0046] The technical effects of the above solution include:

[0047] (1) Reduce the risk of sand carrying during the gas production phase: The tail pipe 1 and the sealing mechanism 2 work together to form a relatively closed space on the inner wall of the neck section. The first sealing ring 21 is in a sealed fit with the inner wall of the neck section, reducing the possibility of sand carrying by the airflow, thereby reducing the wear of the production equipment in the wellbore caused by the impact of the sand-carrying airflow, effectively avoiding equipment blockage and extending the service life of the equipment;

[0048] (2) Avoiding the risk of neck shrinkage: The tail pipe 1 has a stronger anti-extrusion capability than the production casing, and a layer of buffer material 7 is provided on the outer wall of the tail pipe. When the neck section creeps and shrinks and contacts the tail pipe, the presence of the buffer material 7 makes the tail pipe more evenly stressed. The strong anti-extrusion capability of the tail pipe itself effectively limits the shrinkage and deformation of the neck section, thereby avoiding the risk of neck section closure and collapse, improving the stability of the salt cavern reservoir during operation, and ensuring the reservoir's gas production capacity and economic benefits.

[0049] (3) Reduce the risk of gas leakage in the interlayer: The first sealing ring 21 fits tightly against the inner wall of the neck section, forming an effective sealing barrier. The setting of the sealing mechanism 2 prevents the gas in the interlayer from leaking to the outside through the neck section to a certain extent, which not only reduces energy waste but also reduces safety risks to the surrounding environment and facilities.

[0050] (4) The stability of the tail pipe is ensured: In addition to being able to effectively isolate the inner wall of the neck section, the sealing mechanism 2 also provides a certain constraint on the tail pipe from a mechanical point of view, thereby avoiding the shaking of the tail pipe under the injection and production conditions of the salt cavern reservoir, and ensuring the stability of the injection and production process; the tail pipe body 11 and the suspension assembly 12 and the lower connecting part 13 are all connected in a nested manner, which allows the tail pipe body 11 and the suspension assembly 12 and the lower connecting part 13 to have relative displacement. Under the action of the creep contraction of the salt cavern, the entire structure allows for controllable tensile deformation, thereby avoiding the overall tensile fracture of the tail pipe.

[0051] In one embodiment, see Figure 2-Figure 6 , a blocking convex ring 31 is formed at the lower end of the production casing 3, and a plurality of first fixing holes 32 are further opened on the inner side wall of the lower end of the production casing 3; the suspension assembly 12 includes an upper ring body 121, a plurality of first clamping blocks 122, a plurality of first elastic members 123 and a sealing ring 124. The upper ring body 121 is coaxially fixed to the upper end of the tail pipe body 11, and a plurality of first receiving grooves corresponding to the first fixing holes 32 are opened on the outer side wall of the upper ring body 121. The first clamping block 122 is slidably arranged in the corresponding first receiving groove, one end of the first elastic member 123 is fixed in the first receiving groove, the other end of the first elastic member 123 is fixed to one end of the first clamping block 122, and the other end of the first clamping block 122 is used to be inserted into the corresponding first fixing hole 32. The sealing ring 124 is embedded between the upper ring body 121 and the blocking convex ring 31. When the other end of the first clamping block 122 is inserted into the corresponding first fixing hole 32, the sealing ring 124 is in a compressed state.

[0052] In this embodiment, a lifting device is used to hoist the tail pipe 1 as a whole and slowly place it into the production casing 3 of the salt cavern reservoir. When the suspension assembly 12 of the tail pipe 1 moves down to the lower end of the production casing 3, the first receiving groove on the outer wall of the upper ring body 121 gradually aligns with the first fixing hole 32 on the inner wall of the lower end of the production casing 3. Due to the action of the first elastic member 123, the first clamping block 122 is subjected to an outward elastic force. When the two are aligned, the first clamping block 122 is pushed by the first elastic member 123 and the other end is inserted into the corresponding first fixing hole 32. As the first clamping block 122 is inserted, the distance between the upper ring body 121 and the blocking protrusion 31 gradually decreases, so that the sealing ring 124 embedded between the two is squeezed and finally in a compressed state, completing the sealing and fixed connection between the suspension assembly 12 of the tail pipe 1 and the lower end of the production casing 3. By inserting the first clamping block 122 into the first fixing hole 32, a fixed connection between the suspension assembly 12 of the tail pipe 1 and the lower end of the production casing 3 is achieved. This connection method can withstand a certain amount of tension and pressure, ensuring the stable installation of the tail pipe 1 in the production casing 3, preventing the tail pipe 1 from loosening or falling off during gas production or injection, and improving the overall stability of the salt cavern storage wellbore structure.

[0053] See also Figure 8-Figure 9 The above embodiment is suitable for the case where the lower end of the production casing 3 has a blocking protrusion 31 and a first fixing hole 32. If the production casing 3 does not have the blocking protrusion 31 and the first fixing hole 32, the structure of the suspension assembly 12 adopts the following scheme:

[0054] An air passage 1211 is formed in the upper ring body 121 of the suspension assembly 12. The suspension assembly 12 also includes an annular cylinder 125, several pistons 126 and a one-way valve 127. The annular cylinder 125 is fixedly sleeved on the outside of the upper ring body 121. A closed inflation chamber is formed in the annular cylinder 125. An air inlet connected to the inflation chamber is provided on the upper end surface of the annular cylinder 125. The air inlet is connected to the air passage 1211. Several telescopic grooves are provided on the side wall of the annular cylinder 125. Each piston 126 is sealingly and slidingly arranged in the corresponding telescopic groove and is used to abut against the inner wall of the production casing 3 to be clamped in the production casing 3. The one-way valve 127 is arranged in the air inlet.

[0055] In this embodiment, after the air channel 1211 is connected to the air pump, the tail pipe 1 is slowly lowered into the production casing 3 through the operation of the hoist. During this process, the suspension assembly 12 of the tail pipe 1 gradually moves downward. When the suspension assembly 12 of the tail pipe 1 moves down to the lower end of the production casing 3, the air pump is started for inflation. The gas filled by the air pump enters the air inlet of the annular cylinder 125 through the air channel 1211. Due to the action of the one-way valve 127, the gas can only enter the inflation chamber and cannot flow out in the opposite direction. As the gas pressure in the inflation chamber increases, each piston 126 is pushed to slide and extend in the corresponding telescopic groove. The extended piston 126 abuts against the inner wall of the production casing 3, thereby clamping the suspension assembly 12 in the production casing 3. After the piston 126 is clamped in the production casing 3, the air pump and the corresponding connecting pipes are removed to complete the connection operation between the tail pipe 1 and the production casing 3.

[0056] The technical effects of the above technical solution are as follows: In view of the fact that the production casing 3 does not have the blocking protrusion 31 and the first fixing hole 32, this special suspension assembly 12 structure is designed, so that the tail pipe 1 can be connected to production casings 3 of different structures, thereby improving the versatility and applicability of the tail pipe 1. The piston 126 is extended and clamped in the production casing 3 by inflation through an air pump. This connection method can provide a large clamping force, ensuring that the connection between the tail pipe 1 and the production casing 3 is firm and not easy to loosen or fall off during subsequent production operations, thereby ensuring the safety and stability of production. The entire connection process is mainly completed through air pump inflation and sling operation, without the need for complex installation tools and cumbersome operating steps, reducing the labor intensity of the operator and improving work efficiency.

[0057] In one embodiment, see Figure 2-Figure 6 A first inclined surface and a first vertical surface are formed on one end of the first blocking block 122 facing the first fixing hole 32 , and the first vertical surface is used to abut against the inner top surface of the first fixing hole 32 .

[0058] When in use, the first inclined surface on the first clamping block 122 plays an important role in the connection and installation of the tail pipe 1 suspension assembly 12 and the lower end of the production casing 3. When the tail pipe 1 is hoisted and placed in the production casing 3, the suspension assembly 12 gradually approaches the lower end of the production casing 3, and the first clamping block 122 moves downward with the upper ring body 121 to approach the first fixing hole 32. The first inclined surface first contacts the inner wall of the production casing 3. Due to the guiding effect of the inclined surface, the first clamping block 122 will shrink as the tail pipe 1 continues to descend, which greatly reduces the difficulty of installation and improves the installation efficiency. When the first clamping block 122 is fully inserted into the first fixing hole 32, the first vertical surface abuts against the inner top surface of the first fixing hole 32. This abutment method can withstand large axial tension and avoid affecting the safety and sealing of the entire salt cavern storage wellbore structure due to loose connection.

[0059] In one embodiment, see Figure 2-Figure 6 The sealing mechanism 2 further includes a second sealing ring 24 , which is fixed to the end of the extension sleeve 131 , and the inner ring of the flexible connector 22 is fixedly connected to the second sealing ring 24 .

[0060] In one embodiment, see Figure 2-Figure 6 The flexible connector 22 is a rubber flexible connector. Rubber material has excellent flexibility and elasticity, and has a certain sealing performance, which can effectively prevent gas leakage from the gap between the tail pipe and the neck section, enhance the sealing performance of the entire protective structure, and help reduce the risk of gas leakage in the interlayer.

[0061] In one embodiment, see Figure 2-Figure 6 The inner side wall of the mounting hole is further provided with a plurality of second fixing holes 1311; the clamping assembly 23 includes a clamping rod 231, a plurality of second clamping blocks 232 and a plurality of second elastic members 233, the clamping rod 231 corresponding to the mounting hole one-to-one, the clamping rod 231 being slidably inserted into the corresponding mounting hole, and the outer side wall of the clamping rod 231 is provided with a plurality of second accommodating grooves corresponding one-to-one to the second fixing holes 1311, the second clamping block 232 being slidably arranged in the corresponding second accommodating groove, one end of the second elastic member 233 is fixed in the second accommodating groove, the other end of the second elastic member 233 is fixed to one end of the second clamping block 232, and the other end of the second clamping block 232 is used to be inserted into the corresponding second fixing hole 1311, when the other end of the second clamping block 232 is inserted into the corresponding second fixing hole 1311, the first sealing ring 21 is in a clamped state.

[0062] In this embodiment, when the clamping assembly 23 reaches the clamping position, the second clamping block 232 is inserted into the second fixing hole 1311 to fix the clamping rod 231 in a specific position. At this time, the clamping rod 231 can stably press the first sealing ring 21, putting it in a clamped state. This stable clamping action ensures that the first sealing ring 21 can fit tightly against the inner wall of the neck section, effectively preventing the leakage of gas or liquid between the two, greatly enhancing the sealing performance of the neck section protection structure of the existing dissolution cavity converted into a salt cavern storage, reducing the risk of interlayer gas leakage, avoiding energy waste and possible safety hazards. Multiple clamping assemblies 23 are evenly distributed in the mounting hole along the circumference of the extension sleeve 131. Each clamping assembly 23 can apply pressure to the first sealing ring 21, so that the pressure is evenly distributed on the circumference of the first sealing ring 21. This can avoid the occurrence of sealing failure due to insufficient local pressure, further improving the reliability and stability of the seal.

[0063] In one embodiment, see Figure 2-Figure 6 A second inclined surface and a second vertical surface are formed on the end of the second clamping block 232 facing the second fixing hole 1311. The second vertical surface is configured to abut against the inner sidewall of the second fixing hole 1311 away from the first sealing ring 21. In this embodiment, the abutment of the second vertical surface of the second clamping block against the inner sidewall of the second fixing hole away from the first sealing ring enables precise positioning, ensuring the accurate position of the clamping rod within the mounting hole and preventing it from moving or shaking, thereby ensuring stable compression of the first sealing ring.

[0064] The present invention also provides a construction method for converting an existing dissolution cavity into a salt cavern reservoir neck section protection structure, which is applicable to the construction method for converting an existing dissolution cavity into a salt cavern reservoir neck section protection structure and includes the following steps:

[0065] S1. First, secure the suspension assembly 12 to the upper end of the tail pipe body 11. Then, install the extension sleeve 131 of the lower connecting portion 13 and secure it securely to the lower end of the tail pipe body 11. Then, install each clamping assembly 23 into its corresponding mounting hole, ensuring that the clamping assembly 23 can move flexibly to prepare for subsequent clamping operations.

[0066] S2. Use a lifting device to hoist the pre-installed liner 1 as a whole, and slowly place the liner 1 into the production casing 3 of the salt cavern reservoir. During the placement process, pay close attention to the position and direction of the liner 1 to ensure that the liner 1 can smoothly enter the production casing 3. When the suspension assembly 12 of the liner 1 moves down to the lower end of the production casing 3, perform a sealing and fixed connection operation between the suspension assembly 12 and the lower end of the production casing 3;

[0067] S3. After the connection between the tail pipe 1 and the production casing 3 is completed, the compression operation of the sealing mechanism 2 is started. Each compression component 23 is operated to expand outward and gradually compress the first sealing ring 21. As the compression component 23 is continuously compressed, the outer diameter of the first sealing ring 21 gradually increases until the first sealing ring 21 is tightly fitted with the inner side wall of the neck section of the salt cavern storage cavity, achieving a good sealing effect.

[0068] S4. After completing the tightening operation of the sealing mechanism 2, conduct a comprehensive inspection of the tail pipe protection structure to check whether the connection between the tail pipe 1 and the production casing 3 is firm and whether the seal is good; check the fit of the first sealing ring 21 with the inner wall of the neck section to ensure that the sealing effect meets the design requirements. After inspection and testing to confirm that the tail pipe protection structure is correctly installed and performs well, the entire installation work is completed.

[0069] Please refer to Figure 6 and Figure 7During actual installation, in order to facilitate the clamping assembly 23 to reach the clamping position, a sling 4 and a pushing mechanism 5 are also required. The sling 4 is installed at the wellhead, and the pushing mechanism 5 includes a sling 51 and a cone head 52. The upper end of the sling 51 is connected to the output end of the sling 4, and the cone head 52 is connected to the other end of the sling 51. The maximum outer diameter of the cone head 52 is equal to the inner diameter of the extension sleeve 131, and the conical surface of the cone head 52 is used to abut against each clamping rod 231.

[0070] During use, the assembled tail pipe 1 is hoisted as a whole by the sling 4 and slowly placed into the production casing of the salt cavern reservoir, so that the tail pipe 1 reaches the predetermined position and the extension sleeve 131 of the tail pipe 1 is partially in the neck section. The sling 4 is installed at the wellhead, the upper end of the sling 51 is connected to the output end of the sling 4, and the cone head 52 is connected to the other end of the sling 51, and the maximum outer diameter of the cone head 52 is equal to the inner diameter of the extension sleeve 131. The sling 4 controls the descent of the sling 51 so that the cone head 52 gradually enters the extension sleeve 131. Since the conical surface of the cone head 52 will abut against each clamping rod 231, as the cone head 52 descends, the conical surface will apply an outward thrust to the clamping rod 231, causing the clamping rod 231 to slide outward in the mounting hole. When the clamping rod 231 slides outward to a certain extent, the other end of the second clamping block 232 is inserted into the corresponding second fixing hole 1311 under the action of the second elastic member 233. At this time, the clamping rod 231 is fixed. At the same time, the outer diameter of the first sealing ring 21 increases under the pressure of the clamping rod 231 and fits tightly with the inner wall of the neck section to achieve sealing.

[0071] The technical effects provided by the present invention include:

[0072] (1) Reduce the risk of sand carrying during the gas production phase: The tail pipe 1 and the sealing mechanism 2 work together to form a relatively closed space on the inner wall of the neck section. The first sealing ring 21 is in a sealed fit with the inner wall of the neck section, reducing the possibility of sand carrying by the airflow, thereby reducing the wear of the production equipment in the wellbore caused by the impact of the sand-carrying airflow, effectively avoiding equipment blockage and extending the service life of the equipment;

[0073] (2) Avoiding the risk of neck shrinkage: The tail pipe 1 has a stronger anti-extrusion capability than the production casing, and a layer of buffer material 7 is provided on the outer wall of the tail pipe. When the neck section creeps and shrinks and contacts the tail pipe, the presence of the buffer material 7 makes the tail pipe more evenly stressed. The strong anti-extrusion capability of the tail pipe itself effectively limits the shrinkage and deformation of the neck section, thereby avoiding the risk of neck section closure and collapse, improving the stability of the salt cavern reservoir during operation, and ensuring the reservoir's gas production capacity and economic benefits.

[0074] (3) Reduce the risk of gas leakage in the interlayer: The first sealing ring 21 fits tightly against the inner wall of the neck section, forming an effective sealing barrier. The setting of the sealing mechanism 2 prevents the gas in the interlayer from leaking to the outside through the neck section to a certain extent, which not only reduces energy waste but also reduces safety risks to the surrounding environment and facilities.

[0075] (4) The stability of the tail pipe is ensured: In addition to being able to effectively isolate the inner wall of the neck section, the sealing mechanism 2 also provides a certain constraint on the tail pipe from a mechanical point of view, thereby avoiding the shaking of the tail pipe under the injection and production conditions of the salt cavern reservoir, and ensuring the stability of the injection and production process; the tail pipe body 11 and the suspension assembly 12 and the lower connecting part 13 are all connected in a nested manner, which allows the tail pipe body 11 and the suspension assembly 12 and the lower connecting part 13 to have relative displacement. Under the action of the creep contraction of the salt cavern, the entire structure allows for controllable tensile deformation, thereby avoiding the overall tensile fracture of the tail pipe.

[0076] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A protective structure for the neck section of a salt cavern reservoir converted from an existing dissolution cavity, characterized in that: include: The tail pipe comprises a tail pipe body, a suspension assembly and a lower connecting portion, the suspension assembly being nested and connected to the top end of the tail pipe body, with a sliding space reserved therebetween, and axial displacement can occur when the tensile stress between the two reaches a certain threshold, a first protruding bayonet is provided at the end of the tail pipe to limit the maximum axial displacement of the suspension assembly, the lower connecting portion comprising an extension sleeve, the extension sleeve being nested and connected to the bottom end of the tail pipe body, with a sliding space reserved therebetween, and axial displacement can occur when the tensile stress between the two reaches a certain threshold, a second protruding bayonet is provided at the end of the tail pipe to limit the maximum axial displacement of the extension sleeve, and a plurality of mounting holes are uniformly opened on the side wall of the extension sleeve along the circumferential direction; and, The sealing mechanism includes a first sealing ring, a flexible connector and a plurality of clamping components. The flexible connector is annular, an inner ring of which is fixed to the extension sleeve, and an outer ring of which is fixedly connected to the first sealing ring. The plurality of clamping components are respectively fixed to the corresponding mounting holes and are used to press the first sealing ring so that the first sealing ring is sealed and fits tightly against the inner wall of the neck segment.

2. The protective structure for the neck section of a salt cavern reservoir converted from an existing dissolution cavity according to claim 1 is characterized in that: A blocking convex ring is formed at the lower end of the production casing, and a plurality of first fixing holes are also formed on the inner side wall of the lower end of the production casing; The suspension assembly includes an upper ring body, several first clamping blocks, several first elastic members and a sealing ring, the upper ring body is coaxially fixed to the upper end of the tail pipe body, and the outer side wall of the upper ring body is provided with several first accommodating grooves corresponding to the first fixing holes, the first clamping block is slidably arranged in the corresponding first accommodating grooves, one end of the first elastic member is fixed in the first accommodating groove, the other end of the first elastic member is fixed to one end of the first clamping block, and the other end of the first clamping block is used to be inserted into the corresponding first fixing hole, and the sealing ring is embedded between the upper ring body and the blocking convex ring. When the other end of the first clamping block is inserted into the corresponding first fixing hole, the sealing ring is in a compressed state.

3. The protective structure for the neck section of a salt cavern reservoir converted from an existing dissolution cavity according to claim 2 is characterized in that: A first inclined surface and a first vertical surface are formed on one end of the first clamping block facing the first fixing hole. The first vertical surface is used to abut against the inner top surface of the first fixing hole.

4. The protective structure for the neck section of a salt cavern reservoir converted from an existing dissolution cavity according to claim 1 is characterized in that: The suspension assembly includes an upper ring body, an air passage is formed in the upper ring body, and the suspension assembly also includes an annular cylinder, a plurality of pistons and a one-way valve. The annular cylinder is fixedly sleeved on the upper ring body, and a closed inflation chamber is formed in the annular cylinder. An air inlet connected to the inflation chamber is provided on the upper end surface of the annular cylinder, and the air inlet is connected to the air passage. A plurality of telescopic grooves are provided on the side wall of the annular cylinder, and each piston is seal-slidably set in the corresponding telescopic groove and is used to abut against the inner wall of the production casing to be clamped in the production casing. The one-way valve is set in the air inlet.

5. The protective structure for the neck section of a salt cavern storage converted from an existing dissolution cavity according to claim 1 is characterized in that: The sealing mechanism further includes a second sealing ring, which is fixed to the end of the extension sleeve, and the inner ring of the flexible connecting body is fixedly connected to the second sealing ring.

6. The protective structure for the neck section of a salt cavern reservoir converted from an existing dissolution cavity according to claim 1 is characterized in that: The flexible connector is a rubber flexible connector.

7. The protective structure for the neck section of a salt cavern storage converted from an existing dissolution cavity according to claim 1 is characterized in that: The inner side wall of the mounting hole is further provided with a plurality of second fixing holes; The clamping assembly includes a clamping rod, a plurality of second clamping blocks and a plurality of second elastic members, the clamping rod corresponding to the mounting hole one-to-one, the clamping rod being slidably inserted into the corresponding mounting hole, a plurality of second accommodating grooves corresponding to the second fixing holes being opened on the outer side wall of the clamping rod, the second clamping block being slidably arranged in the corresponding second accommodating groove, one end of the second elastic member being fixed in the second accommodating groove, the other end of the second elastic member being fixed to one end of the second clamping block, the other end of the second clamping block being used to be inserted into the corresponding second fixing hole, and when the other end of the second clamping block is inserted into the corresponding second fixing hole, the first sealing ring is in a clamped state.

8. The protective structure for the neck section of a salt cavern storage converted from an existing dissolution cavity according to claim 7 is characterized in that: A second inclined surface and a second vertical surface are formed on one end of the second clamping block facing the second fixing hole. The second vertical surface is used to abut against an inner sidewall of the second fixing hole away from the first sealing ring.

9. A construction method for converting an existing dissolution cavity into a salt cavern reservoir neck protection structure, characterized in that: The method is applicable to the neck protection structure of a salt cavern storage converted from an existing dissolution cavity as described in any one of claims 1 to 8, and comprises the following steps: S1. First, secure the suspension assembly to the upper end of the tail pipe body. Then, install the extension sleeve of the lower connection portion and secure it securely to the lower end of the tail pipe body. Then, install each clamping assembly into the corresponding mounting hole, ensuring that the clamping assembly can move flexibly to prepare for subsequent clamping operations. S2. Use a lifting device to hoist the pre-installed liner as a whole and slowly place it into the production casing of the salt cavern reservoir. During the placement process, pay close attention to the position and direction of the liner to ensure that the liner can enter the production casing smoothly. When the liner suspension assembly moves down to the lower end of the production casing, seal and secure the suspension assembly to the lower end of the production casing. S3. After the connection between the tail pipe and the production casing is completed, the compression operation of the sealing mechanism is started. Each compression component is operated to expand outward and gradually compress the first sealing ring. As the compression components are continuously compressed, the outer diameter of the first sealing ring gradually increases until the first sealing ring is tightly fitted with the inner side wall of the top neck section of the salt cavern storage cavity, achieving a good sealing effect; S4. After completing the tightening operation of the sealing mechanism, conduct a comprehensive inspection of the tail pipe protection structure to check whether the connection between the tail pipe and the production casing is firm and whether the seal is good; check the fit between the first sealing ring and the inner wall of the neck section to ensure that the sealing effect meets the design requirements. After inspection and testing, confirm that the tail pipe protection structure is installed correctly and performs well, and then complete the entire installation work.

Images