A method for gas injection and production and cavity expansion of a salt cavern gas storage

Abstract

The present application relates to salt cavern gas storage technical field, especially to a kind of salt cavern gas storage injection and method for expanding cavity, comprising: downhole first production pipe and second production pipe, through first halogen pipe, halogen water in the salt cavern gas storage is discharged, and the natural gas in the salt cavern gas storage is injected and mined;The pressure of natural gas in the salt cavern gas storage is reduced to minimum, and the first well and / or the second well are used to inject blocking solvent into the salt cavern gas storage, and any halogen pipe in the first halogen pipe and the second halogen pipe is used to inject water into the salt cavern gas storage, and another halogen pipe is used to discharge halogen, to expand the salt cavern gas storage, and the natural gas in the expanded salt cavern gas storage is injected and mined. Natural gas injection and mining can be carried out in advance before the completion of salt cavern gas storage cavity, that is, production can be carried out in advance, and after injection and mining operation, the salt cavern gas storage can continue to be expanded.

Description

Technical Field

[0001] This invention relates to the field of salt cavern gas storage technology, and more particularly to a method for gas injection and extraction, and cavity construction and expansion of a salt cavern gas storage facility. Background Technology

[0002] Salt cavern gas storage projects suffer from long well construction times and delayed commissioning. Constructing a 200,000 cubic meter cavity at a flow rate of 100 cubic meters per hour takes approximately 2-3 years, while a 400,000 cubic meter cavity requires 5-6 years. While dual-well construction can increase the speed, constructing a 400,000 cubic meter salt cavern still requires 2-3 years. This long construction time and delayed commissioning are detrimental to project development. While increasing wellbore size and flow rate can accelerate construction, this method is limited by brine consumption and concentration. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for gas injection and extraction and cavity expansion of a salt cavern gas storage facility, which addresses the shortcomings of the prior art.

[0004] The technical solution of the method for gas injection and extraction and cavity expansion of a salt cavern gas storage facility according to the present invention is as follows: S1. A first production pipe is installed in the first well of the salt cavern gas storage facility using the dual-well cavity technology for melting and dewatering, and a second production pipe is installed in the second well of the salt cavern gas storage facility. S2. A first brine discharge pipe is lowered into the first production pipe, with the lower end of the first brine discharge pipe extending into the brine of the salt cavern gas storage tank. Natural gas is injected into the salt cavern gas storage tank using at least one of the first well and the second well, so that the brine in the salt cavern gas storage tank is discharged through the first brine discharge pipe until the brine discharge is completed. S3. After the brine is drained, the first brine drain pipe is removed, and the natural gas in the salt cavern gas storage is injected and extracted using the first production pipe and the second production pipe. S4. When expanding the capacity of the salt cavern gas storage, stop the injection and extraction of natural gas in the salt cavern gas storage and extract the natural gas in the salt cavern gas storage until the pressure of the natural gas in the salt cavern gas storage is reduced to the minimum. S5. The first brine discharge pipe is lowered into the first production pipe, and the second brine discharge pipe is lowered into the second production pipe. The solvent inhibitor is injected into the salt cavern gas storage tank through the first annular gap between the first production pipe and the first brine discharge pipe and the second annular gap between the second production pipe and the second brine discharge pipe. Water is injected into the salt cavern gas storage tank using either the first brine discharge pipe or the second brine discharge pipe, and brine is discharged using the other brine discharge pipe. S6. Repeat S5 to expand the capacity of the salt cavern gas storage tank; S7. Repeat steps S2 and S3 for the expanded salt cavern gas storage to inject and extract natural gas within the expanded salt cavern gas storage.

[0005] The beneficial effects of the method for gas injection and extraction and cavity expansion of a salt cavern gas storage facility according to the present invention are as follows: This invention breaks through the conventional construction sequence of gas storage facilities, which involves cavity construction, gas injection and brine discharge, and injection-production operation. Instead, it proposes a rolling process sequence of "cavity construction - gas injection and brine discharge - injection-production operation - cavity construction." This technology meets the requirements for rapid commissioning of newly constructed cavities and the rapid commissioning of existing cavities converted into gas storage facilities. Simultaneously, it allows for continued erosion to expand the volume of new cavities after commissioning, and for continued erosion to repair the morphology of existing cavities after commissioning, thereby increasing the cavity volume, storage capacity, and working gas volume.

[0006] Based on the above scheme, the method for gas injection and extraction and cavity expansion of a salt cavern gas storage facility of the present invention can be further improved as follows.

[0007] Furthermore, the extraction process of natural gas from the salt cavern storage facility until the pressure of the natural gas in the salt cavern storage facility is reduced to a minimum includes: S40. Perform initial extraction of natural gas from the salt cavern gas storage facility until the pressure of the natural gas in the salt cavern gas storage facility is reduced to the preset minimum operating pressure. S41. Lower the first brine drain pipe into the first production pipe and / or lower the second brine drain pipe into the second production pipe, and inject water into the salt cavern gas storage tank through the first brine drain pipe and / or the second production pipe, and continue to discharge natural gas through the first annular gap between the first production pipe and the first brine drain pipe and / or the second annular gap between the second production pipe and the second brine drain pipe, until the pressure of the natural gas in the salt cavern gas storage tank is reduced to the minimum.

[0008] Furthermore, before S1, it also includes: The cavity-forming pipes in the first well and the second well of the salt cavern gas storage facility, which employs a dual-well cavity-forming technology for melting and extraction, are removed.

[0009] Furthermore, after S1, it also includes: A first downhole safety valve is installed near the ground in the first production pipe.

[0010] Furthermore, after S1, it also includes: A second downhole safety valve is installed near the ground level in the second production pipe.

[0011] Furthermore, after S1, the method further includes: setting a first packer at the lower end of the first production tube.

[0012] Furthermore, the first packer is a permanent packer.

[0013] Furthermore, after S1, a second packer is provided at the lower end of the second production tube.

[0014] Furthermore, the solvent used to inhibit combustion is either diesel fuel or nitrogen.

[0015] Furthermore, the salt cavern gas storage facility refers to either a newly built salt cavern gas storage facility or an existing well cavity.

[0016] The beneficial effect of adopting the above-mentioned further scheme is that it can maximize the benefits of well construction. Attached Figure Description

[0017] Figure 1 This is a schematic flowchart illustrating a method for gas injection and extraction and cavity expansion in a salt cavern gas storage facility according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure for the first gas injection and brine discharge. Figure 3 This is a schematic diagram of the injection and production structure for the first time. Figure 4 A schematic diagram of the cavity expansion structure; Figure 5 This is a schematic diagram of the secondary production injection and extraction structure; The attached diagram lists the components represented by each number as follows: 1. First well; 2. First production pipe; 3. First brine drain pipe; 4. First packer; 5. Second well; 6. Second production pipe; 7. Second packer; 8. Brine; 9. Pit; 10. First annular gap; 11. Second annular gap; 12. Second brine drain pipe. Detailed Implementation

[0018] like Figure 1 As shown, an embodiment of the present invention provides a method for gas injection and extraction, and cavity expansion of a salt cavern gas storage facility, comprising the following steps: S1. A first production pipe 2 is installed in the first well 1 of the salt cavern gas storage facility using the dual-well cavity technology, and a second production pipe 6 is installed in the second well 5 of the salt cavern gas storage facility. The production pipe can also be called a gas production pipe, namely the first gas production pipe and the second gas production pipe.

[0019] S2. A first brine pipe 3 is lowered into the first production pipe 2, with its lower end extending into the brine 8 of the salt cavern gas storage tank. Natural gas is injected into the salt cavern gas storage tank using at least one of the first well 1 and the second well 5, so that the brine 8 in the salt cavern gas storage tank can be discharged through the first brine pipe 3 until the brine discharge is completed. Figure 2 As shown, at this point, the salt cavern gas storage facility still has a bottom pit 9, which includes silt, gravel, and remaining brine.

[0020] The specific process of injecting natural gas into the salt cavern gas storage using at least one of the first well 1 and the second well 5 is as follows: natural gas is injected into the salt cavern gas storage using the "annular gap between the first brine discharge pipe 3 and the first production pipe 2" or the "second production pipe 6".

[0021] S3. After the brine discharge is completed, remove the first brine discharge pipe 3, and use the first production pipe 2 and the second production pipe 6 to inject and extract natural gas from the salt cavern gas storage tank. Figure 3 As shown; S4. When expanding the capacity of the salt cavern gas storage, stop the injection and extraction of natural gas in the salt cavern gas storage and extract the natural gas in the salt cavern gas storage until the pressure of the natural gas in the salt cavern gas storage is reduced to the minimum. S5. A first brine discharge pipe 3 is lowered into the first production pipe 2, and a second brine discharge pipe 12 is lowered into the second production pipe 6. An inhibitor is injected into the salt cavern gas storage tank through the first annular gap between the first production pipe 2 and the first brine discharge pipe 3, and the second annular gap between the second production pipe 6 and the second brine discharge pipe 12. Water is injected into the salt cavern gas storage tank using either the first brine discharge pipe 3 or the second brine discharge pipe 12, and brine is discharged using the other brine discharge pipe. S6. Repeat S5 to expand the salt cavern gas storage capacity; after lowering the first brine pipe 3 and the second brine pipe 124, water is injected through one of the brine pipes, and brine is discharged through the other, circulating and dissolving the salt rock in the salt cavern gas storage capacity, thereby expanding the volume of the salt cavern gas storage capacity. Figure 4 As shown.

[0022] S7. Repeat steps S2 and S3 on the expanded salt cavern gas storage facility to inject and extract natural gas within the expanded facility, such as... Figure 5 As shown. That is to say, the first row of brine pipes 3 and the second row of brine pipes 12 are removed, and the first production pipe 2 and the second production pipe 6 are used to perform secondary injection and extraction of natural gas in the salt cavern gas storage.

[0023] It can inject and produce natural gas before the cavity construction of the salt cavern gas storage is completed, that is, put it into production in advance. After the injection and production is in operation, it can continue to build and expand the cavity of the salt cavern gas storage to increase the volume of the salt cavern gas storage, so that the salt cavern gas storage can switch between gas injection and cavity construction until the volume of the salt cavern gas storage reaches the preset design volume.

[0024] This invention breaks through the conventional construction sequence of gas storage facilities, which involves cavity construction, gas injection and brine discharge, and injection-production operation. Instead, it proposes a rolling process sequence of "cavity construction - gas injection and brine discharge - injection-production operation - cavity construction." This technology meets the requirements for rapid commissioning of newly constructed cavities and the rapid commissioning of existing cavities converted into gas storage facilities. Simultaneously, it allows for continued erosion to expand the volume of new cavities after commissioning, and for continued erosion to repair the morphology of existing cavities after commissioning, thereby increasing the cavity volume, storage capacity, and working gas volume.

[0025] Optionally, in the above technical solution, the natural gas in the salt cavern gas storage is extracted until the pressure of the natural gas in the salt cavern gas storage is reduced to a minimum, including: S40. Perform initial extraction of natural gas from the salt cavern gas storage facility until the pressure of the natural gas in the salt cavern gas storage facility is reduced to the preset minimum operating pressure. The minimum operating pressure is the lower limit of the operating pressure at which the natural gas in the salt cavern gas storage facility can be safely and stably injected and extracted. S41. A first brine pipe 3 is lowered into the first production pipe 2 and / or a second brine pipe 12 is lowered into the second production pipe 6. Water is injected into the salt cavern gas storage tank through the first brine pipe 3 and / or the second production pipe 6. Natural gas is then discharged through the first annular gap 10 between the first production pipe 2 and the first brine pipe 3 and / or the second annular gap 1 between the second production pipe 6 and the second brine pipe 12 until the pressure of the natural gas in the salt cavern gas storage tank is reduced to the minimum.

[0026] Optionally, in the above technical solution, the step before S1 further includes: The cavity-forming pipes from the first well 1 and the second well 5 of the salt cavern gas storage facility, which were dissolved using the dual-well cavity-forming technology, were removed.

[0027] Optionally, in the above technical solution, after S1, the following is also included: A first downhole safety valve is installed near the ground in the first production pipe 2.

[0028] Optionally, in the above technical solution, after S1, the following is also included: A second downhole safety valve is installed near the ground in the second production pipe 6.

[0029] Optionally, in the above technical solution, after S1, a first packer 4 is provided at the lower end of the first production pipe 2.

[0030] Optionally, in the above technical solution, the first packer 4 is a permanent packer.

[0031] Optionally, in the above technical solution, after S1, a second packer 7 is provided at the lower end of the second production pipe 6.

[0032] Optionally, in the above technical solution, the solvent is diesel or nitrogen.

[0033] Optionally, in the above technical solution, the salt cavern gas storage facility can be: a newly built salt cavern gas storage facility, or an existing well cavity. Currently, existing salt cavern gas storage facilities often suffer from irregular cavity shapes and insufficient dissolution of the upper salt layer. After conversion into a gas storage facility, the irregular cavity shape necessitates depressurization operation, and the undissolved upper salt layer results in wasted construction resources, failing to maximize the benefits of existing well cavity gas storage. Specifically: The construction time for new wells in salt cavern gas storage facilities is long, resulting in a late commissioning time. At a flow rate of 100 cubic meters per hour, constructing a 200,000 cubic meter cavity takes approximately 2-3 years, while constructing a 400,000 cubic meter cavity takes 5-6 years. While dual-well construction can increase the construction speed, constructing a 400,000 cubic meter salt cavern still requires 2-3 years. This long construction time and late commissioning time are detrimental to project construction. Increasing well size and flow rate can accelerate construction, but this method is limited by brine consumption and concentration. Therefore, other methods must be adopted to expedite the commissioning process. Furthermore, existing salt cavern gas storage facilities often suffer from irregular cavity shapes and insufficient dissolution of the upper salt layer. After conversion, these facilities must operate at reduced pressure due to their irregular shapes, and the undissolved upper salt layer leads to wasted construction resources, failing to maximize the benefits of existing cavern gas storage. This invention aims to maximize the benefits of constructing gas storage facilities using existing wells.

[0034] The following embodiment illustrates in detail the method for gas injection and extraction and cavity expansion of a salt cavern gas storage facility according to the present invention. Specifically: S100. When the volume of the salt cavern gas storage facility eroded using the dual-well cavity-making technology does not reach the preset design volume, the cavity-making pipe in the first well 1 and the cavity-making pipe in the second well 5 of the salt cavern gas storage facility eroded using the dual-well cavity-making technology shall be removed. The salt cavern gas storage facility is either a newly built salt cavern gas storage facility or an old cavity formed by well erosion using the well erosion technology. Specifically, it can be either a newly built salt cavern gas storage facility using the dual-well cavity-making technology or an old cavity formed by well erosion using the well erosion technology. S101. A first production pipe 2 is installed in the first well 1 of the salt cavern gas storage facility using the dual-well cavity technology for dissolution, and a second production pipe 6 is installed in the second well 5 of the salt cavern gas storage facility. The installation depth of the first production pipe 2 and the second production pipe 6 is designed according to the final top depth of the salt cavern gas storage facility to be reached by dissolution, and is generally located 15-20m above the top depth of the salt cavern gas storage facility. That is to say, the lower end of the first production pipe 2 and the lower end of the second production pipe 6 are located 15-20m above the final designed top depth of the salt cavern gas storage facility. S102. A first downhole safety valve is installed at the position of the first production pipe 2 near the ground, and a second downhole safety valve is installed at the position of the second production pipe 6 near the ground. A first packer 4 is installed at the lower end of the first production pipe 2, and a second packer 7 is installed at the lower end of the second production pipe 6. The first packer 4 and the second packer 7 can be permanent packers.

[0035] S103. A first brine discharge pipe 3 is lowered into the first production pipe 2, with the lower end of the first brine discharge pipe 3 extending into the brine 8 of the salt cavern gas storage. The lower end of the first brine discharge pipe 3 is specifically the maximum brine discharge depth. Natural gas is injected into the salt cavern gas storage using at least one of the first well 1 and the second well 5 to discharge the brine 8 from the salt cavern gas storage through the first brine discharge pipe 3 until the brine discharge is completed. The specific implementation method for injecting natural gas into at least one of the first well 1 and the second well 5 is as follows: Natural gas is injected into the salt cavern gas storage through the gap between the first well 1 and the first production pipe 2, natural gas is injected into the salt cavern gas storage through the gap between the second well 5 and the second production pipe 6, natural gas is injected into the salt cavern gas storage through the second production pipe 6, natural gas is injected into the salt cavern gas storage through the first annular gap 10 between the first production pipe 2 and the first brine discharge pipe 3, and natural gas is injected into the salt cavern gas storage through the second annular gap 1 between the second production pipe 6 and the second brine discharge pipe 12, etc.

[0036] The process begins when the volume of the salt cavern gas storage reaches 30% of the preset design volume. After the cavity-forming pipe is removed and the production pipe and safety valve packer are installed, the initial gas injection and brine discharge are carried out.

[0037] When no brine 8 is discharged through the first brine pipe 3, the brine discharge is considered to be over; or when the flow rate of brine discharged through the first brine pipe 3 is less than the preset flow rate, the brine discharge is considered to be over. S104. After the brine is drained, the first brine drain pipe 3 is removed, and the first production pipe 2 and the second production pipe 6 are used to inject and extract natural gas in the salt cavern gas storage. Injection and extraction is the daily production process, which includes injecting natural gas into the salt cavern gas storage using a ground compressor and extracting natural gas by opening the wellhead of the salt cavern gas storage.

[0038] S105. After a period of operation of the salt cavern gas storage facility, if gas injection and production are suspended according to production needs, and cavity construction continues to expand the volume of the salt cavern gas storage facility, then when expanding the capacity of the salt cavern gas storage facility, the injection and production of natural gas in the salt cavern gas storage facility shall be stopped, and the natural gas in the salt cavern gas storage facility shall be extracted until the pressure of the natural gas in the salt cavern gas storage facility is reduced to the minimum; specifically: The natural gas in the salt cavern storage is initially extracted until the pressure of the natural gas in the salt cavern storage is reduced to a preset minimum operating pressure; that is, the natural gas in the salt cavern storage is extracted to the maximum extent possible until the pressure of the natural gas in the salt cavern storage is reduced to the preset minimum operating pressure. The first brine drain pipe 3 is lowered into the first production pipe 2 and / or the second brine drain pipe 12 is lowered into the second production pipe 6. Water is injected into the salt cavern storage through the first brine drain pipe 3 and / or the second production pipe 12. Natural gas continues to be discharged through the first annular gap 10 between the first production pipe 2 and the first brine drain pipe 3 and / or the second annular gap 11 between the second production pipe 6 and the second brine drain pipe 12 until the pressure of the natural gas in the salt cavern storage is reduced to the minimum.

[0039] S106. Injecting solvent into the salt cavern gas storage using the first well 1 and / or the second well 5, specifically injecting it from the wellhead of the first well 1 and / or the second well 5 into the annulus between the first production pipe 2 and the first brine discharge pipe 3, i.e., the first annular gap 10, or injecting it into the annulus between the second production pipe 6 and the second brine discharge pipe 12, i.e., the second annular gap 11. Water is injected into the salt cavern gas storage using the first brine discharge pipe 3 and any one of the brine discharge pipes 3, and brine is discharged using the other brine discharge pipe. Specifically: For example, according to the cavity-building design scheme of a salt cavern gas storage facility, the brine discharge pipe 11 is lowered into the second well (5) to the designed position, and the original brine discharge pipe 3 in the first well (1) is adjusted to the designed position. Diesel or nitrogen is injected into both wells as a solvent inhibitor. One well is injected with water, while the other well discharges brine, creating a circulating cavity to repair its shape and expand its volume. This involves adjusting the lowering depth of the two brine discharge pipes periodically according to the cavity-building design to control the shape and progress of the cavity building.

[0040] S107. Repeat S106 to expand the capacity of the salt cavern gas storage and repair its shape.

[0041] S108. Repeat S103 and S104 for the expanded salt cavern gas storage to inject and extract natural gas in the expanded salt cavern gas storage, so as to put the salt cavern gas storage back into operation. The process of S103 to S108 is repeated to achieve the following steps: cavity construction, initial gas injection and brine discharge, initial injection and extraction operation, water injection and venting, secondary cavity construction, secondary gas injection and brine discharge, and secondary injection and extraction operation, until the cavity reaches the preset design volume in the cavity construction design scheme.

[0042] This invention breaks through the conventional construction sequence of salt cavern gas storage, which involves cavity construction, gas injection and brine removal, and injection-production operation. Instead, it proposes a rolling process sequence of "cavity construction - gas injection and brine removal - injection-production operation - cavity construction." This technology meets the requirements for rapid commissioning of newly constructed cavities and the rapid commissioning of existing cavities converted into gas storage facilities. Simultaneously, it allows for continued dissolution and volume expansion of new cavities after commissioning, and for morphological repair of existing cavities after commissioning, thereby increasing the volume of the salt cavern gas storage facility and improving its storage capacity and working gas volume.

[0043] The beneficial effects of the method for gas injection and extraction and cavity expansion of a salt cavern gas storage facility according to the present invention are illustrated by the following data: The geological formation in a certain mining area is designed to create a cavity in the 1500m-1700m section, with a designed effective cavity volume of 400,000 cubic meters. This means the pre-designed volume of the salt cavern gas storage is 400,000 cubic meters. The dual-well cavity-creating technology is used for dissolution, and the construction is carried out using a 7”+7” tubing string for convection cavity creation. The total cavity-creating dissolution time is designed to be 3 years, meaning the calculation takes three years to achieve the salt cavern gas storage volume of 400,000 cubic meters. The cavity-building process for the salt cavern gas storage facility commenced. Cavity building ceased when the effective volume of the cavity reached 120,000 cubic meters (one-third of the total cavity volume). In other words, cavity building stopped when the salt cavern gas storage facility reached its 120,000 cubic meter volume. The 7” cavity-building tubing from both wells was removed, and a 7” production tubing was installed. A downhole safety valve and permanent packer were then installed at a depth of 1480m. In Well 1, a 4” production tubing was installed. 1 / 2” gas-tight brine drain pipe, lowered to the maximum brine draining depth of the salt cavern gas storage (2m above the bottom pit), to carry out gas injection and brine draining operations. Natural gas is injected into the second well 5, and brine 8 is discharged from the brine drain pipe of the first well 1 until the brine draining is completed.

[0044] The brine discharge pipe 3 of Well 1 was removed, and the salt cavern gas storage facility entered the production and operation phase. Gas extraction and injection were carried out through the 57” production pipe of Well 2 and the 7” production pipe of Well 1.

[0045] After several years of operation, the salt cavern gas storage facility will be re-enhanced according to production requirements. This includes repairing the cavity shape and expanding the cavity volume. First, natural gas will be extracted from the salt cavern storage facility until the pressure drops to the lower limit pressure. That is, until the pressure of the natural gas in the salt cavern storage facility is reduced to the preset minimum operating pressure, fresh water will be injected from well 1, and gas extraction will continue from well 5 until most of the natural gas has been extracted. Well 1 will then be re-inserted with 4... 1 / 2” brine drain pipe, 4” simultaneously lowered into the second well 5” 1 / 2” brine discharge tubing, through the first well 14 1 / 2” tubing string and second well 54 1The / 2” tubing string was used for circulation cavity creation, and the 4” tubing in both wells was adjusted according to the cavity creation design. 1 The / 2” tubing is lowered to a depth to dissolve and control the cavity morphology of the salt cavern gas storage facility until the volume of the salt cavern gas storage facility reaches the designed volume of 400,000 cubic meters.

[0046] Gas injection and brine removal were carried out again in both wells. 1 The 2” tubing string was lowered to the maximum depth, and natural gas was injected from the annulus of both wells. From 4… 1 / 2” tubing discharges 8g of brine until the aeration and brine discharge are completed, then 4g is removed under pressure. 1 The / 2” tubing and salt cavern gas storage facility have been put back into operation.

[0047] Those skilled in the art will know that this invention can be implemented as a system, method, or computer program product.

[0048] In this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0049] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0050] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for gas injection and extraction and cavity expansion in a salt cavern gas storage facility, characterized in that, include: When the volume of the salt cavern gas storage facility using the dual-well cavity-making technology for melting and leaching does not reach the preset design volume, the cavity-making pipe in the first well and the cavity-making pipe in the second well of the salt cavern gas storage facility using the dual-well cavity-making technology for melting and leaching are removed. S1. A first production pipe is installed in the first well of the salt cavern gas storage facility using the dual-well cavity technology for melting and dewatering, and a second production pipe is installed in the second well of the salt cavern gas storage facility. S2. A first brine discharge pipe is lowered into the first production pipe, with the lower end of the first brine discharge pipe extending into the brine of the salt cavern gas storage tank. The lower end of the first brine discharge pipe is lowered to the maximum brine discharge depth. Natural gas is injected into the salt cavern gas storage tank using at least one of the first well and the second well, so that the brine in the salt cavern gas storage tank can be discharged through the first brine discharge pipe until the brine discharge is completed. S3. After the brine is drained, the first brine drain pipe is removed, and the natural gas in the salt cavern gas storage is injected and extracted using the first production pipe and the second production pipe. S4. After a period of operation of the salt cavern gas storage facility, gas injection and production are suspended according to production needs. Cavity building continues to expand the volume of the salt cavern gas storage facility. When expanding the capacity of the salt cavern gas storage facility, gas injection and production within the facility are stopped, and the natural gas is extracted until the pressure of the natural gas within the facility is reduced to a minimum, including: S40. Perform initial extraction of natural gas from the salt cavern gas storage facility until the pressure of the natural gas in the salt cavern gas storage facility is reduced to the preset minimum operating pressure. S41. Insert the first brine discharge pipe into the first production pipe and / or insert the second brine discharge pipe into the second production pipe, and inject water into the salt cavern gas storage through the first brine discharge pipe and / or the second production pipe, and continue to discharge natural gas through the first annular gap between the first production pipe and the first brine discharge pipe and / or the second annular gap between the second production pipe and the second brine discharge pipe until the pressure of the natural gas in the salt cavern gas storage is reduced to the minimum. S5. The first brine discharge pipe is lowered into the first production pipe, and the second brine discharge pipe is lowered into the second production pipe. An inhibitor is injected into the salt cavern gas storage tank through the first annular gap between the first production pipe and the first brine discharge pipe and the second annular gap between the second production pipe and the second brine discharge pipe. The inhibitor is injected from the wellhead of the first well and / or the second well, specifically into the first annular gap or the second annular gap. Water is injected into the salt cavern gas storage tank using either the first brine discharge pipe or the second brine discharge pipe, and brine is discharged using the other brine discharge pipe. S6. Repeat S5 to expand the capacity of the salt cavern gas storage and to repair the shape of the salt cavern gas storage. S7. Repeat S2 and S3 on the expanded salt cavern gas storage to inject and extract natural gas in the expanded salt cavern gas storage. The process of S2 to S7 is repeated to realize the process of cavity creation, initial gas injection and brine discharge, initial injection and production operation, water injection and venting, secondary cavity creation, secondary gas injection and brine discharge, and secondary injection and production operation, until the volume of the salt cavern gas storage reaches the preset design volume in the cavity creation design scheme.

2. The method for gas injection, extraction, cavity construction, and expansion of a salt cavern gas storage facility according to claim 1, characterized in that, Before S1, the following also applies: The cavity-forming pipes in the first well and the second well of the salt cavern gas storage facility, which employs a dual-well cavity-forming technology for melting and extraction, are removed.

3. The method for gas injection, extraction, and cavity expansion of a salt cavern gas storage facility according to claim 1, characterized in that, Following S1, the following also includes: A first downhole safety valve is installed near the ground in the first production pipe.

4. The method for gas injection, extraction, cavity construction, and expansion of a salt cavern gas storage facility according to claim 1, characterized in that, Following S1, the following also includes: A second downhole safety valve is installed near the ground level in the second production pipe.

5. The method for gas injection, extraction, and cavity expansion of a salt cavern gas storage facility according to claim 1, characterized in that, The step S1 further includes: setting a first packer at the lower end of the first production pipe.

6. The method for gas injection, extraction, cavity construction, and expansion of a salt cavern gas storage facility according to claim 5, characterized in that, The first packer is a permanent packer.

7. The method for gas injection, extraction, and cavity expansion of a salt cavern gas storage facility according to claim 1, characterized in that, The process after S1 also includes: setting a second packer at the lower end of the second production pipe.

8. The method for gas injection, extraction, and cavity expansion of a salt cavern gas storage facility according to claim 1, characterized in that, The solvent used to inhibit solvents is diesel or nitrogen.

9. A method for gas injection, production, and cavity expansion in a salt cavern gas storage facility according to any one of claims 1 to 8, characterized in that, The salt cavern gas storage facility refers to either a newly built salt cavern gas storage facility or an existing well cavern.

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