High-pressure gas synergistic induction salt cavern self-sealing system and construction method thereof

Abstract

The invention relates to the technical field of salt cavern sealing, in particular to a high-pressure gas synergistic induction salt cavern self-sealing system and a construction method of the high-pressure gas synergistic induction salt cavern self-sealing system. One end of the production sleeve, one end of the brine collection outer pipe and one end of the brine collection inner pipe are all communicated with the interior of the salt cavern, one end of the brine collection inner pipe and one end of the brine collection outer pipe can extend to the salt cavern, and the salt cavern is provided with gas injection and brine discharge trees which are respectively communicated with the production sleeve, the brine collection outer pipe and the brine collection inner pipe. Self-sealing of the salt cavern is achieved through the synergistic effect of the high-pressure carbon dioxide and the methane ethanol gas in combination with gas injection and exhaust and liquid injection and drainage operation, the salt cavern sealing method has the advantages of being efficient in sealing, easy and convenient to construct, environmentally friendly, capable of effectively solving the problems that a traditional salt cavern sealing method is complex in construction, high in cost, limited in sealing effect and the like, and has wide application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of salt cavern sealing, and in particular to a high-pressure gas cooperatively induced salt cavern self-sealing system and a construction method thereof. Background Art

[0002] Salt-cavern gas storage (SCS) utilizes cavities in underground salt formations to store natural gas or other gases. Due to their excellent sealing, stability, and large storage capacity, SCSs are widely used in the natural gas storage field. However, over the long term, SCSs may experience gas leakage due to factors such as dissolution of the cavern walls and crack expansion, compromising their safety and stability.

[0003] Traditional salt cavern sealing methods rely primarily on injecting heavy oil or other sealing materials to seal cracks in the cavern walls. However, this approach presents challenges such as complex construction, high costs, and limited sealing effectiveness. Furthermore, traditional methods struggle to achieve uniform sealing across the cavern walls, with the sealing effect being particularly poor at the cavern's bottom and top. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: in order to solve the problem that traditional salt cavern sealing methods mainly rely on injecting heavy oil or other sealing materials to seal cracks in the salt cavern walls, but this method has the disadvantages of complex construction, high cost, limited sealing effect, and difficulty in achieving uniform sealing of the salt cavern walls, especially poor sealing effect at the bottom and top of the salt cavern. A high-pressure gas synergistically induced salt cavern self-sealing system and its construction method are now provided.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a high-pressure gas synergistically induced salt cavern self-sealing system, comprising:

[0006] A salt cavern is provided with a production casing, a brine extraction outer pipe, and a brine extraction inner pipe, which are sequentially sleeved from the outside to the inside. One end of the production casing, one end of the brine extraction outer pipe, and one end of the brine extraction inner pipe are all connected to the interior of the salt cavern. One end of the brine extraction inner pipe and one end of the brine extraction outer pipe can extend into the salt cavern. The salt cavern is provided with a gas injection and brine drainage tree, which is respectively connected to the production casing, the brine extraction outer pipe, and the brine extraction inner pipe.

[0007] An injection and exhaust module is connected to the salt cavern, and the injection and exhaust module includes a carbon dioxide gas storage tank, a gas compressor, a first heat exchanger, a first valve and a first port of a gas injection and brine drainage tree which are connected in sequence. The first port of the gas injection and brine drainage tree is connected to the brine production inner pipe. A bypass is connected in parallel to the first valve. A second valve and an ejector are connected in series along the gas transmission direction on the bypass. The suction port of the ejector is connected to the output end of the ethanol storage tank. A first cavity is formed between the production casing and the brine production outer pipe and is connected to the second port of the gas injection and brine drainage tree. The second port of the gas injection and brine drainage tree is connected to a pressure reducing skid, a cyclone separator, a gas buffer tank, a gas pressure pump and a pressure swing adsorption device in sequence. The first outlet of the pressure swing adsorption device is connected to the natural gas pipeline network, and the second outlet of the pressure swing adsorption device is connected to the carbon dioxide gas storage tank;

[0008] An injection and drainage module is connected to the salt cavern. The injection and drainage module includes a brine tank, a pipeline mixer, a brine pump and a third valve connected in sequence. The dosing port of the tubular mixer is connected in sequence with a thickening pump 24 and a thickening liquid tank. The thickening liquid tank contains a thickening liquid for increasing the viscosity of the brine and promoting the stability of salt precipitation, reducing the salt precipitation rate, promoting the strength of the crystallized salt, and enhancing the sealing of the salt cavern. The injection and drainage module also includes a heavy oil tank, a heavy oil pump and a fourth valve connected in sequence. The heavy oil tank contains a sealing interface for protecting the bottom of the salt cavern, promoting the stability of the salt crystals, and preventing the crystallized salt protective layer from being consumed in subsequent operations. The third valve and the fourth valve are both connected to the third port of the gas injection and brine drainage tree. A second cavity is formed between the brine production outer pipe and the brine production inner pipe and is connected to the salt cavern. The third port of the gas injection and brine drainage tree is connected to the second cavity. Compared with the existing technology, this solution increases the solubility of sodium chloride by introducing carbon dioxide into saturated brine, promotes the brine to further dissolve the sodium chloride on the inner wall of the salt cavern, and introduces a mixed gas of methane and ethanol into the saturated brine to reduce the solubility of sodium chloride. At the same time, the continuous introduction of methane gas will replace the carbon dioxide gas in the solution, further reducing the saturation of the brine. The addition of a small amount of ethanol will also cause the supersaturated brine to precipitate salt crystals and preferentially adsorb on the salt wall. Continuous crystallization will eventually play a role in plugging leaks and reinforcing the brine. The addition of thickening and recombinant liquid will increase the viscosity of the brine, promote the stability of salt precipitation, reduce the salt precipitation rate, further promote the strength of the crystallized salt, enhance the sealing of the salt cavern, protect the sealing interface at the bottom of the salt cavern, promote the stability of the salt crystals, and prevent the crystallized salt protective layer from being consumed in subsequent operations.

[0009] In some preferred embodiments, a fifth valve is connected in parallel on the pipeline of the pipeline mixer, the brine pump and the third valve, a sixth valve is connected in parallel on the pipeline of the heavy oil pump and the fourth valve, and a one-way valve is connected in series between the ethanol storage tank and the suction port of the injector.

[0010] In some preferred embodiments, a first dehydration device is connected in series between the outlet of the carbon dioxide storage tank and the inlet of the gas compressor, a second dehydration device is connected in series between the outlet of the cyclone separator and the gas buffer tank, a pressure sensor is provided between the first valve and the first port of the gas injection and brine removal tree, the natural gas pipeline network is connected to the input end of the gas compressor, and a seventh valve is connected in series between the natural gas pipeline network and the input end of the gas compressor.

[0011] In some preferred embodiments, the carbon dioxide gas storage tank is connected to an external carbon dioxide gas source.

[0012] A construction method of the high-pressure gas synergistically induced salt cavern self-sealing system as described above comprises the following steps:

[0013] S1. Fill the salt cavern to be constructed with saturated brine;

[0014] S2. Continuously pump carbon dioxide gas into the salt cavern through a gas compressor, discharge part of the brine, and then control the brine level, carbon dioxide pressure range, and pressure holding time;

[0015] S3. After the brine is introduced and the carbon dioxide gas is discharged, the methane alcohol mixed gas is continuously blown into the bottom of the salt cavern through the gas compressor. After part of the brine is discharged, the brine liquid level, the upper gas pressure range and the pressure holding time are controlled;

[0016] S4. Inject heavy component liquid to seal the bottom interface of the salt cavern for protection;

[0017] S5. Repeat S2-S4 until the sealing protection of the entire salt wall is completed.

[0018] In some preferred embodiments, carbon dioxide gas is pumped into the salt cavern from the bottom to discharge part of the brine. The pressure maintaining range of carbon dioxide is 10-12 MPa, and the pressure maintaining time at the pressure maintaining pressure is 48 hours.

[0019] In some preferred embodiments, a methane and ethanol mixed gas is pumped into the salt cavern from the bottom to discharge part of the brine, the carbon dioxide pressure is maintained in the range of 10-12 MPa, and the pressure holding time at the pressure holding pressure is 72 hours.

[0020] In some preferred embodiments, the amount of saturated brine discharged is no more than 1% of the physical volume of the salt cavern.

[0021] In some preferred embodiments, the heavy component liquid is high-density mineral oil.

[0022] In some preferred embodiments, the thickening liquid is one or more of xanthan gum, guar gum, sodium carboxymethyl cellulose, sodium alginate, and polyglutamic acid, and the viscosity of the thickening liquid is 3000-5000 mPa·s.

[0023] The beneficial effects of the present invention are as follows: when in use, the high-pressure gas synergistically induced salt cavern self-sealing system and its construction method of the present invention increase the solubility of sodium chloride by introducing carbon dioxide into saturated brine, promote the brine to further dissolve the sodium chloride on the inner wall of the salt cavern, introduce methane and ethanol mixed gas into the saturated brine, and reduce the solubility of sodium chloride. At the same time, the continuous introduction of methane gas will replace the carbon dioxide gas in the solution, further reducing the saturation of the brine. The addition of a small amount of ethanol will also cause the supersaturated brine to precipitate salt crystals, which will be preferentially adsorbed on the salt wall. The continuous crystallization finally plays the role of plugging and reinforcing, and cooperates with the thickening heavy component to The addition of liquid increases the viscosity of the brine, which will promote the stability of salt precipitation, reduce the salt precipitation rate, further promote the strength of the crystallized salt, enhance the sealing of the salt cavern, protect the sealing interface at the bottom of the salt cavern, promote the stability of the salt crystals, and prevent the crystallized salt protective layer from being consumed in subsequent operations. It has the advantages of efficient sealing of the salt cavern, simple construction, environmental protection and energy saving, and avoids the traditional salt cavern sealing method that mainly relies on injecting heavy oil or other sealing materials to seal the cracks on the salt cavern wall. However, this method has the problems of complex construction, high cost, limited sealing effect, and difficulty in achieving uniform sealing of the salt cavern wall, especially the poor sealing effect at the bottom and top of the salt cavern. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below with reference to the accompanying drawings and examples.

[0025] Figure 1 It is a structural schematic diagram of the present invention;

[0026] Figure 2 This is a flow chart of sealing a salt cavern during construction of the present invention.

[0027] In the figure: 1. Carbon dioxide storage tank, 2. First dehydration device, 3. Gas compressor, 4. First heat exchanger, 5. Pressure sensor, 6. Ethanol storage tank, 7. Ejector, 8. One-way valve, 9. Gas injection brine tree, 10. Pipeline, 11. Pressure reducing skid, 12. Cyclone separator, 13. Second dehydration device, 14. Gas buffer tank, 15. Gas booster pump, 16. Pressure swing adsorption device, 17. Heavy oil pump, 18. Heavy oil tank, 19. Heavy oil bypass, 20. Brine pump, 21. Brine tank, 22. Brine bypass, 23. Thickening liquid tank, 24. Thickening pump, 25. Tubular mixer, 26. Production casing, 27. Brine production outer pipe, 28. Brine production inner pipe, 29. Salt cavern. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with the embodiments:

[0029] The present invention is not limited to the following specific embodiments. Based on the disclosure of the present invention, a person skilled in the art may adopt a variety of other specific embodiments to implement the present invention. Any simple changes or modifications made to the design structure and concept of the present invention fall within the scope of protection of the present invention. It should be noted that the embodiments and features of the embodiments of the present invention may be combined with each other unless they conflict.

[0030] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0031] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0032] like Figure 1-2 As shown, a high-pressure gas synergistically induced salt cavern self-sealing system comprises:

[0033] A salt cavern 29 is provided with a production casing 26, a brine extraction outer pipe 27 and a brine extraction inner pipe 28, which are sequentially sleeved from the outside to the inside. One end of the production casing 26, one end of the brine extraction outer pipe 27 and one end of the brine extraction inner pipe 28 are all connected to the interior of the salt cavern 29. One end of the brine extraction inner pipe 28 can extend to the bottom of the salt cavern 29, and one end of the brine extraction outer pipe 27 can be located at the top of the salt cavern 29. After the pressure in the salt cavern 29 is relieved, the brine extraction outer pipe 27 and the brine extraction inner pipe 28 can be relatively extended into or retracted into the positions in the salt cavern 29. Depending on the user's usage scenario, a gas injection and brine discharge tree 9 is provided on the salt cavern 29, which is respectively connected to the production casing 26, the brine extraction outer pipe 27 and the brine extraction inner pipe 28. The salt cavern 29 serves as the core part of the system and is used to store gas and brine.

[0034] An injection and exhaust module is connected to the salt cavern 29. The injection and exhaust module includes a carbon dioxide storage tank 1, a gas compressor 3, a first heat exchanger 4, a first valve and a first port of a gas injection and brine removal tree 9 which are connected in sequence. The first port of the gas injection and brine removal tree 9 is connected to the brine production inner pipe 28. A bypass is connected in parallel to the first valve. A second valve and an injector 7 are connected in series along the gas transmission direction on the bypass. The suction port of the injector 7 is connected to the output end of the ethanol storage tank 6. A first cavity is formed between the production casing 26 and the brine production outer pipe 27 and is connected to the second port of the gas injection and brine removal tree 9. The second port of the gas injection and brine removal tree 9 is connected in sequence to a pressure reducing skid 11, a cyclone separator 12, a gas buffer tank 14, a gas pressure pump 15 and a pressure swing adsorption device 16. The first outlet of the pressure swing adsorption device 16 is connected to the natural gas pipeline network, and the second outlet of the pressure swing adsorption device 16 is connected to the carbon dioxide storage tank 1;

[0035] The injection and drainage module is connected to the salt cavern 29. The injection and drainage module includes a brine tank 21, a tubular mixer 25, a brine pump 20 and a third valve connected in sequence. The dosing port of the tubular mixer 25 is connected in sequence with a thickening pump 24 and a thickening liquid tank 23. The thickening liquid tank 23 contains a thickening liquid. The thickening liquid is used to increase the viscosity of the brine and promote the stability of salt precipitation, reduce the salt precipitation rate, promote the strength of the crystallized salt, and enhance the sealing of the salt cavern. The injection and drainage module also includes a heavy oil tank 18, a heavy oil pump 17 and a fourth valve connected in sequence. The heavy oil tank There is a heavy component liquid in 18, which is used to protect the sealing interface at the bottom of the salt cavern, promote the stability of the salt crystals, and prevent the crystalline salt protective layer from being consumed in subsequent operations. The third valve and the fourth valve are both connected to the third port of the gas injection and brine drainage tree 9. A second cavity is formed between the brine extraction outer pipe 27 and the brine extraction inner pipe 28 and is connected to the salt cavern 29. The third port of the gas injection and brine drainage tree 9 is connected to the second cavity. The brine pump 20 and the heavy oil pump 17 are both provided with a bypass to receive the corresponding reflux brine or heavy component liquid.

[0036] The brine bypass 22 is connected in parallel to the pipelines of the tubular mixer 25, the brine pump 20 and the third valve, and the fifth valve is provided on the brine bypass 22. The heavy oil pump 17 and the pipeline of the fourth valve are connected in parallel to the heavy oil bypass 19, and the sixth valve is provided on the heavy oil bypass 19.

[0037] A one-way valve 8 is connected in series between the ethanol storage tank 6 and the suction port of the injector 7 .

[0038] A first dehydration device 2 is connected in series between the outlet of the carbon dioxide storage tank 1 and the inlet of the gas compressor 3 , and a second dehydration device 13 is connected in series between the outlet of the cyclone separator 12 and the gas buffer tank 14 .

[0039] A pressure sensor 5 is provided between the first valve and the first port of the gas injection and brine removal tree 9 .

[0040] The natural gas pipeline network is connected to the input end of the gas compressor 3. A seventh valve is connected in series between the natural gas pipeline network and the input end of the gas compressor 3. The carbon dioxide storage tank 1 is connected to an external carbon dioxide gas source.

[0041] In this embodiment, the density of the heavy component liquid is greater than that of water and is an organic substance that is immiscible with water, preferably a high-density mineral oil. The thickening liquid in the thickening liquid barrel 23 is a solution of one or more of xanthan gum, guar gum, sodium carboxymethyl cellulose, sodium alginate, and polyglutamic acid, and the viscosity of the thickening liquid is 3000-5000 mPa·s.

[0042] Salt dissolving effect of carbon dioxide: By introducing carbon dioxide into saturated brine, the solubility of sodium chloride can be increased, which promotes the brine to further dissolve the sodium chloride on the inner wall of the salt cavern;

[0043] Salting-out effect of methane and ethanol mixed gas: By introducing methane and ethanol mixed gas into saturated brine, the solubility of sodium chloride can be reduced. At the same time, the continuous introduction of methane gas will replace the carbon dioxide gas in the solution, further reducing the saturation of the brine. The addition of trace ethanol will also cause the salt crystals precipitated from the supersaturated brine to be preferentially adsorbed on the salt wall. Continuous crystallization will eventually play a role in plugging leaks and strengthening the brine.

[0044] The addition of thickening liquid increases the viscosity of the brine, which will promote the stability of salt precipitation, reduce the salt precipitation rate, further promote the strength of crystallized salt, and enhance the sealing of salt caverns.

[0045] Sealing protection: By injecting heavy component liquid, the sealing interface at the bottom of the salt cave 29 is protected, the stability of the salt crystals is promoted, and the crystallized salt protective layer is prevented from being consumed in subsequent operations.

[0046] The above-mentioned high-pressure gas synergistically induced salt cavern self-sealing system and construction method, when in use, can effectively achieve self-sealing of the salt cavern through the synergistic effect of high-pressure carbon dioxide and methane ethanol gas, combined with the injection and exhaust module and the injection and drainage module, thereby improving the sealing and long-term stability of the salt cavern 29. It is easy to operate, can effectively reduce construction costs, improve construction efficiency, recover gas through the pressure swing adsorption device 16, reduce gas emissions, and has good environmental benefits and energy conservation.

[0047] Example 2

[0048] Example 2 is a construction method of Example 1, specifically: a construction method of a high-pressure gas synergistically induced salt cavern self-sealing system as described above, comprising the following steps:

[0049] S1, fill the salt cavern 29 to be constructed with saturated brine through the injection and drainage module;

[0050] S2. Carbon dioxide gas is continuously pumped into the salt cavern 29 through the gas compressor 3. Then, after part of the brine is discharged, the brine liquid level, carbon dioxide pressure range and pressure holding time are controlled. When carbon dioxide gas is pumped into the salt cavern 29 from the bottom and part of the brine is discharged, the pressure holding range of carbon dioxide is 10-12 MPa, and the pressure holding time at the pressure holding pressure is 48 hours. When methane and ethanol mixed gas is pumped into the salt cavern 29 from the bottom and part of the brine is discharged, the pressure holding range of carbon dioxide is 10-12 MPa, and the pressure holding time at the pressure holding pressure is 72 hours. The amount of saturated brine discharged is not more than 1% of the physical volume of the salt cavern 29, preferably 0.2 -0.5%, that is, the outlet of the natural gas network and the outlet of the carbon dioxide storage tank 1 output gas to the inlet of the first dehydration device 2, and the water inside the gas is dehydrated. The dehydrated gas enters the compressor, is compressed to a certain pressure, and then is transported to the first heat exchanger 4 for heat exchange. The gas after heat exchange passes through the pressure sensor 5 and then enters the brine inner pipe 28 connected to the gas injection and brine production tree 9 to realize the injection of gas into the bottom of the salt cavern 29. At the same time, when the gas is input, ethanol can be output from the outlet of the ethanol storage tank 6 and enter the suction port of the injector 7 through the one-way valve 8. The injector 7 injects the ethanol to the inlet of the pressure sensor 5;

[0051] S3, after the brine is introduced and the carbon dioxide gas is discharged, the methane alcohol mixed gas is continuously pumped into the bottom of the salt cavern 29 through the gas compressor 3. After part of the brine is discharged, the brine liquid level, the upper gas pressure range and the pressure holding time are controlled. That is, the brine pump 20 inputs the brine in the brine pool 21 through the tubular mixer 25 into the second cavity where the annulus of the brine production outer pipe 27 and the brine production inner pipe 28 is introduced, so that the brine enters the interior of the salt cavern 29. At the same time, the first cavity between the production casing 26 and the brine production outer pipe 27 is connected to the brine through the gas injection and brine discharge tree. The carbon dioxide enters the pressure reducing skid 11 through the bypass for pressure reduction, and is then transported to the cyclone separator 12 for separation treatment. The treated gas enters the second dehydration device 13 for dehydration again, and the dehydrated gas enters the gas buffer tank 14. The gas buffer tank 14 transports the gas to the pressure pump 17 for pressurization, and then transports the gas to the adsorption device. The first outlet of the pressure swing adsorption device 16 outputs natural gas and is connected to the natural gas pipeline network. The second outlet of the pressure swing adsorption device 16 outputs carbon dioxide and is transported to the carbon dioxide gas storage tank 1;

[0052] S4. Inject the heavy component liquid to protect the sealed interface at the bottom of the salt cavern 29. That is, the heavy oil pump 17 transports the heavy oil in the heavy oil tank 18 into the second cavity of the brine extraction outer pipe 27 and the brine extraction inner pipe 28, thereby transporting the heavy oil into the salt cavern 29.

[0053] S5. Repeat S2-S4 until the sealing protection of the entire salt wall is completed.

[0054] The above description of the preferred embodiments of the present invention is intended to serve as a guide. Based on the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A high-pressure gas synergistically induced salt cavern self-sealing system, characterized in that: include: A salt cavern is provided with a production casing, a brine extraction outer pipe, and a brine extraction inner pipe, which are sequentially sleeved from the outside to the inside. One end of the production casing, one end of the brine extraction outer pipe, and one end of the brine extraction inner pipe are all connected to the interior of the salt cavern. One end of the brine extraction inner pipe and one end of the brine extraction outer pipe can extend into the salt cavern. The salt cavern is provided with a gas injection and brine drainage tree, which is respectively connected to the production casing, the brine extraction outer pipe, and the brine extraction inner pipe. An injection and exhaust module is connected to the salt cavern, and the injection and exhaust module includes a carbon dioxide gas storage tank, a gas compressor, a first heat exchanger, a first valve and a first port of a gas injection and brine drainage tree which are connected in sequence. The first port of the gas injection and brine drainage tree is connected to the brine production inner pipe. A bypass is connected in parallel to the first valve. A second valve and an ejector are connected in series along the gas transmission direction on the bypass. The suction port of the ejector is connected to the output end of the ethanol storage tank. A first cavity is formed between the production casing and the brine production outer pipe and is connected to the second port of the gas injection and brine drainage tree. The second port of the gas injection and brine drainage tree is connected to a pressure reducing skid, a cyclone separator, a gas buffer tank, a gas pressure pump and a pressure swing adsorption device in sequence. The first outlet of the pressure swing adsorption device is connected to the natural gas pipeline network, and the second outlet of the pressure swing adsorption device is connected to the carbon dioxide gas storage tank; An injection and drainage module is connected to the salt cavern. The injection and drainage module includes a brine tank, a tubular mixer, a brine pump and a third valve connected in sequence. The dosing port of the tubular mixer is connected in sequence with a thickening pump and a thickening liquid tank. The thickening liquid tank contains a thickening liquid for increasing the viscosity of the brine and promoting the stability of salt precipitation, reducing the salt precipitation rate, promoting the strength of the crystallized salt, and enhancing the sealing of the salt cavern. The injection and drainage module also includes a heavy oil tank, a heavy oil pump and a fourth valve connected in sequence. The heavy oil tank contains a sealing interface for protecting the bottom of the salt cavern, promoting the stability of the salt crystals, and preventing the crystallized salt protective layer from being consumed in subsequent operations. The third valve and the fourth valve are both connected to the third port of the gas injection and brine drainage tree. A second cavity is formed between the brine production outer tube and the brine production inner tube and is connected to the salt cavern. The third port of the gas injection and brine drainage tree is connected to the second cavity.

2. The high-pressure gas synergistically induced salt cavern self-sealing system according to claim 1, characterized in that: The pipelines of the tubular mixer, the brine pump and the third valve are connected in parallel with a fifth valve, the pipelines of the heavy oil pump and the fourth valve are connected in parallel with a sixth valve, and a one-way valve is connected in series between the ethanol storage tank and the suction port of the injector.

3. The high-pressure gas synergistically induced salt cavern self-sealing system according to claim 1, characterized in that: A first dehydration device is connected in series between the outlet of the carbon dioxide storage tank and the inlet of the gas compressor, a second dehydration device is connected in series between the outlet of the cyclone separator and the gas buffer tank, a pressure sensor is provided between the first valve and the first port of the gas injection and brine removal tree, the natural gas pipeline network is connected to the input end of the gas compressor, and a seventh valve is connected in series between the natural gas pipeline network and the input end of the gas compressor.

4. The high-pressure gas synergistically induced salt cavern self-sealing system according to claim 1, characterized in that: The carbon dioxide gas storage tank is communicated with an external carbon dioxide gas source.

5. A construction method of a high-pressure gas synergistically induced salt cavern self-sealing system according to any one of claims 1 to 4, characterized in that: The steps are as follows: S1. Fill the salt cavern to be constructed with saturated brine; S2. Continuously pump carbon dioxide gas into the salt cavern through a gas compressor, discharge part of the brine, and then control the brine level, carbon dioxide pressure range, and pressure holding time; S3. After the brine is introduced and the carbon dioxide gas is discharged, the methane alcohol mixed gas is continuously blown into the bottom of the salt cavern through the gas compressor. After part of the brine is discharged, the brine liquid level, the upper gas pressure range and the pressure holding time are controlled; S4. Inject heavy component liquid to seal the bottom interface of the salt cavern for protection; S5. Repeat S2-S4 until the sealing protection of the entire salt wall is completed.

6. The construction method of a high-pressure gas synergistically induced salt cavern self-sealing system according to claim 5, characterized in that: Carbon dioxide gas is pumped into the salt cavern from the bottom to discharge part of the brine. The pressure maintaining range of carbon dioxide is 10-12Mpa, and the pressure maintaining time is 48h under the pressure maintaining pressure.

7. The construction method of a high-pressure gas synergistically induced salt cavern self-sealing system according to claim 5, characterized in that: A mixed gas of methane and ethanol is pumped into the salt cavern from the bottom to discharge part of the brine. The pressure maintaining range of carbon dioxide is 10-12Mpa, and the pressure maintaining time is 72h under the pressure maintaining pressure.

8. The construction method of a high-pressure gas synergistically induced salt cavern self-sealing system according to claim 5, characterized in that: The amount of saturated brine discharged shall not exceed 1% of the physical volume of the salt cavern.

9. The construction method of a high-pressure gas synergistically induced salt cavern self-sealing system according to claim 5, characterized in that: The heavy component liquid is high-density mineral oil.

10. The construction method of a high-pressure gas synergistically induced salt cavern self-sealing system according to claim 5, characterized in that: The thickening liquid is one or more of xanthan gum, guar gum, sodium carboxymethyl cellulose, sodium alginate, and polyglutamic acid, and the viscosity of the thickening liquid is 3000-5000 mPa·s.

Images