Method and system for regulating the freezing circle of the fractured surrounding rock of an underground natural gas reservoir

Abstract

The application provides a kind of underground natural gas reservoir crack surrounding rock freezing circle regulation and control method and system, the method comprises: selecting rock mass excavation roadway to form liquefied natural gas storage cavern, and freezing circle formed by surrounding rock fissure water freezing is used as sealing structure;Set the storage pressure in the hole and the storage temperature of liquefied natural gas under pressurized storage state, and set the temperature of the outer contact surface of the heat preservation layer, and determine the thickness of the heat preservation layer based on the evaporation loss requirement through thermodynamic calculation;Water supply tunnel and water supply hole are arranged above the storage cavern, and drainage tunnel and drainage hole are arranged below the reservoir and the storage cavern;Through multi-stage drainage test, the efficiency of groundwater control process is calculated, and the drilling arrangement of low-efficiency area is optimized;Control drainage until the crack water is drained to the target state;Liquefied natural gas is stored, and the freezing circle is expanded to the target isotherm, the drainage is stopped, and the freezing circle is formed.The application promotes gas storage and abandoned underground space utilization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-temperature liquefied natural gas (LNG) storage, in particular to a method and system for regulating a frozen circle of fractured surrounding rock of an underground natural gas storage. BACKGROUND

[0002] The use of natural gas is growing worldwide, and there is currently a strong demand for the number of gas storage facilities. The construction of gas storage facilities mainly adopts two forms of depleted oil and gas reservoirs and salt caverns, but their site selection is severely limited by geological conditions, and the suitability of site selection is poor, and the construction of gas storage facilities is slow. Only by rapidly promoting gas storage projects can the gap in gas supply be adjusted, and the supply of natural gas can be ensured. In particular, there is a lack of liquefied natural gas security capacity, and new liquefied natural gas storage urgently needs to reduce construction costs. Based on the current development of storage tank construction technology, the trend of large-scale liquefied natural gas storage tanks is becoming more and more obvious, and the single-tank capacity of low-temperature underground liquefied natural gas storage as a new technology can reach one million cubic meters.

[0003] Compared with the above-ground and in-ground storage tank forms, the liquefied natural gas underground low-temperature hole tank is safer, more environmentally friendly, and occupies less land. With the increase in storage capacity, its economic advantage is more obvious: the investment in ground liquefied natural gas storage is about 10 yuan per cubic meter; the investment in gas reservoir type storage is about 8 yuan per cubic meter; and the investment in underground liquefied natural gas storage is expected to be reduced to 6 yuan per cubic meter. With the increasing number of liquefied natural gas receiving stations in coastal areas, the available port resources are becoming more and more limited, while the low-temperature underground liquefied natural gas storage has a wide range of site selection and broad development prospects.

[0004] At present, the technical details of the control of the frozen circle range of the underground low-temperature liquefied natural gas storage (especially at the 0℃ isotherm) are not mature. Therefore, it is urgent to create a scheme that can realize the dynamic evolution and regulation of the frozen circle of the fractured surrounding rock of the low-temperature liquefied natural gas storage, which can provide support for the construction of gas storage facilities in areas where gas consumption is concentrated and the construction of gas storage facilities is difficult, which will have great significance for natural gas reserves and energy structure transformation. SUMMARY

[0005] The present application proposes a method and system for regulating the frozen circle of the fractured surrounding rock of an underground natural gas storage, which is used to solve the defects of the prior art.

[0006] According to a first aspect of an embodiment of the present application, a method for regulating the frozen circle of the fractured surrounding rock of an underground natural gas storage is provided, comprising:

[0007] Selecting a rock body to excavate a roadway to form a storage cavern for liquefied natural gas, and taking the frozen circle formed by the freezing of the fissure water of the surrounding rock as a sealing structure;

[0008] Setting the storage pressure in the hole under the pressurized storage state and the storage temperature of the liquefied natural gas, and setting the temperature of the outer contact surface of the thermal insulation layer, and determining the thickness of the thermal insulation layer based on the evaporation loss requirement through thermodynamic calculation;

[0009] A water supplementing tunnel and water supplementing holes are arranged above the storage hole, and a drainage tunnel and drainage holes are arranged below the storage and the storage hole;

[0010] The efficiency of the groundwater control process is calculated through a multi-stage drainage test, and the drilling arrangement in the low-efficiency area is optimized;

[0011] The drainage is controlled until the fissure water is dewatered to the target state;

[0012] The liquefied natural gas is stored, and the freezing circle is expanded to the target isotherm, the drainage is stopped, and the freezing circle is formed.

[0013] In some embodiments, the selection of the rock mass excavation tunnel to form the liquefied natural gas storage hole comprises:

[0014] The storage site is selected according to the distribution of natural gas users, the gas pipeline network or the location of the liquefied natural gas terminal;

[0015] The geology of the storage site is ensured to meet the geological conditions of no regional fault zone, rock mass uniaxial compressive strength ≥ 30 MPa, and permeability coefficient < 10 -7 m / s;

[0016] The tunnel is excavated in the rock mass of the storage site meeting the geological conditions, and a sealing layer, a thermal insulation layer and a concrete lining layer are layered and lined for forming the storage hole for storing the liquefied natural gas.

[0017] In some embodiments, the water supplementing tunnel and water supplementing holes arranged above the storage hole comprise:

[0018] At least two water supplementing tunnels and a plurality of water supplementing holes are arranged in a range of 15-25 meters above the storage hole, wherein,

[0019] The diameter of each water supplementing hole is in a range of 90-110 mm, and the depth of each water supplementing hole is in a range of less than or equal to 100 meters; a plurality of water supplementing holes are arranged in a staggered manner with a spacing of 10-15 meters, and a rock mass blank area with a range greater than or equal to 2 meters is reserved between adjacent water supplementing holes.

[0020] In some embodiments, the drainage tunnel and drainage holes arranged below the storage and the storage hole comprise:

[0021] At least two external drainage tunnels are arranged in a range of 10-15 meters below the storage;

[0022] An internal drainage gallery is arranged below the storage chamber;

[0023] The external drainage gallery and the internal drainage gallery are communicated by a plurality of drainage holes, and the plurality of drainage holes communicate the internal drainage gallery and the two external drainage galleries at a slope greater than or equal to 1%.

[0024] In some embodiments, the method further comprises:

[0025] A plurality of up-and-down drainage holes are arranged within a range of 10 meters around the storage chamber, wherein,

[0026] Each of the up-and-down drainage holes comprises an upper drainage hole and a lower drainage hole, the upper drainage hole is drilled from the water supply gallery, and the lower drainage hole is drilled from the drainage gallery, and the spatial overlap depth of the plurality of up-and-down drainage holes is greater than or equal to 5 meters.

[0027] In some embodiments, the efficiency of the groundwater control process is calculated by a multi-stage drainage test, comprising:

[0028] The initial water head of the groundwater is measured by controlling to close all the drill holes, and the measurement period is 3-4 days;

[0029] Part of the drill holes are opened for drainage and the drainage efficiency is tested, wherein the upward drill holes are controlled to use self-flow drainage, and the downward drill holes are controlled to use submersible pumps;

[0030] All the drill holes are opened for drainage and the drainage capacity is verified;

[0031] The maximum drainage capacity is tested by performing a simulated rainstorm condition through water injection in the water supply gallery.

[0032] In some embodiments, the drainage is controlled until the fissure water is dewatered to a target state, comprising:

[0033] The drainage is controlled until the fissure water is dewatered to a state in which the groundwater level is lowered to a predetermined depth below the chamber floor, wherein the predetermined depth is in a range of 8-10 meters.

[0034] In some embodiments, the liquefied natural gas is stored and the freezing circle is expanded to a target isotherm, the drainage is stopped, and the freezing circle is formed, comprising:

[0035] The liquefied natural gas is stored;

[0036] After the liquefied natural gas is stored, azimuth detection of the position of the freezing circle is performed, and the drainage is stopped after the freezing circle is expanded to the target isotherm, for recovering the groundwater and forming the freezing circle.

[0037] According to the second aspect of the present application, a regulation system of a frozen circle of a fissure surrounding rock of an underground natural gas reservoir is provided, comprising:

[0038] A reservoir construction module is configured to select a rock mass excavation tunnel to form a liquefied natural gas storage chamber, and to form a frozen circle of fissure water of surrounding rock as a sealing structure;

[0039] A parameter setting module is configured to set a storage pressure in the chamber and a storage temperature of liquefied natural gas in a pressurized storage state, and to set an outer contact surface temperature of the thermal insulation layer, and to determine a thickness of the thermal insulation layer based on a requirement of evaporation loss and through thermodynamic calculation;

[0040] A flow layout module is configured to set a water supplement tunnel and a water supplement hole above the storage chamber, and to set a drainage tunnel and a drainage hole below the reservoir and the storage chamber;

[0041] An efficiency checking module is configured to check the efficiency of a groundwater control process through a multi-stage drainage test, and to optimize the drilling arrangement in an inefficient area;

[0042] A construction preparation module is configured to control drainage until the fissure water is dewatered to a target state;

[0043] A dynamic regulation module is configured to store liquefied natural gas and to expand the frozen circle to a target isotherm, to stop drainage, and to form the frozen circle.

[0044] In some embodiments, the storage chamber comprises, from the inside to the outside, a sealing layer, a thermal insulation layer, a concrete lining layer, the frozen circle, and the surrounding rock;

[0045] The storage pressure in the chamber of the storage chamber is in a range of 1 MPa to 3 MPa, the storage temperature of liquefied natural gas is in a range of -120℃ to -100℃, and the outer contact surface temperature of the thermal insulation layer is in a range of -50℃ to -30℃.

[0046] The regulation method and system of the frozen circle of the fissure surrounding rock of the underground natural gas reservoir according to the embodiments of the present application have at least the following beneficial effects:

[0047] This application embodiment forms a natural sealing barrier through rock tunnels and utilizes the self-expansion property of fracture water upon freezing to create an adaptive freezing zone, significantly improving the structural stability of the storage facility. Simultaneously, it reduces sensitivity to geological conditions, allowing for flexible site selection in stable rock strata areas, overcoming the geographical limitations of traditional storage facilities. By combining pressurized storage with optimized temperature gradient settings, the temperature difference between the inside and outside of the tunnel is effectively reduced, minimizing cold energy loss. The insulation layer thickness is dynamically calculated based on evaporation loss requirements, precisely balancing insulation performance and economy, reducing long-term operational energy consumption from the source. A highly efficient hydraulic control network is formed through upper and lower partitioned water supply and drainage tunnels and boreholes (upper water supply, lower drainage). The staggered borehole design ensured the integrity of the rock mass structure, and spatial collaborative control enabled the directional flow of fissure water, providing a foundation for the dynamic evolution of the frozen zone. Multi-stage pumping and drainage tests accurately identified inefficient areas, and targeted drilling increased system reliability. Dynamic optimization design ensured efficient groundwater drainage during construction and precise replenishment during operation, balancing engineering safety and long-term sealing requirements. Phased drainage control enabled gradual drainage of fissure water, creating a dry environment for cavern construction. After storage, combined with frozen end monitoring data, the replenishment and drainage system was activated and deactivated according to location, promoting the directional infiltration of groundwater into the cooling rock mass to form a complete frozen zone, achieving dynamic and precise control of the sealing structure. Attached Figure Description

[0048] Figure 1 This is a flowchart illustrating the method for controlling the frozen zone of fractured surrounding rock in an underground natural gas storage facility according to an embodiment of this application.

[0049] Figure 2 This is a schematic diagram of the structure of an underground cryogenic liquefied natural gas storage facility according to an embodiment of this application;

[0050] Figure 3 This is a graph showing the boiling point and pressure of liquefied natural gas in a saturated state according to an embodiment of this application.

[0051] Figure 4 This is a temperature field simulation cloud map of cryogenic storage of liquefied natural gas at ambient pressure, according to an embodiment of this application.

[0052] Figure 5 This is a temperature field simulation cloud map of liquefied natural gas stored at low temperature and pressure, as described in an embodiment of this application.

[0053] Figure 6 This is a schematic diagram of the structure of the groundwater control system for a cryogenic liquefied natural gas storage facility according to an embodiment of this application;

[0054] Figure 7 This is a schematic diagram of the first step of freeze zone control in an embodiment of this application;

[0055] Figure 8The third step schematic diagram for the frozen circle regulation of the embodiment of the present application;

[0056] Figure 9 The fourth step schematic diagram for the frozen circle regulation of the embodiment of the present application;

[0057] Figure 10 The fifth step schematic diagram for the frozen circle regulation of the embodiment of the present application;

[0058] Figure 11 The sixth step schematic diagram for the frozen circle regulation of the embodiment of the present application;

[0059] Figure 12 The sixth step schematic diagram for the frozen circle regulation of the embodiment of the present application;

[0060] Figure 13 The structure schematic diagram of the regulation system of the frozen circle of the underground natural gas reservoir fissure surrounding rock of the embodiment of the present application. DETAILED DESCRIPTION

[0061] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0062] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0063] It should be noted that similar reference numerals and letters indicate similar items in the following drawings, and therefore, once an item is defined in one drawing, it need not be further defined and explained in subsequent drawings.

[0064] In the description of the embodiments of the present application, it should be noted that the directions or position relationships indicated by the terms “inner”, “outer”, “upper”, etc. are based on the directions or position relationships shown in the drawings, or the directions or position relationships in which the products of the present application are usually placed, and are only for the convenience of describing the present application and simplifying the description, and therefore, cannot be understood as indicating or implying that the indicated devices or elements must have a particular direction, be constructed and operated in a particular direction, and therefore, cannot be understood as limiting the present application.

[0065] The embodiment of the present application discloses a kind of underground natural gas reservoir fissure surrounding rock freezing circle's regulation and control method, this method is based on the regulation and control method of underground natural gas reservoir fissure surrounding rock freezing circle execution.Referring to the drawings shown in Figure 1 The method includes steps 110-160.

[0066] Step 110, select the rock mass excavation roadway to form the storage cavern of liquefied natural gas (hereinafter referred to as cavern), and the freezing circle formed by the freezing of fissure water in surrounding rock as a sealing structure.

[0067] Wherein, the storage cavern of the present application is the basic physical structure of the reservoir, and the direct containing space of liquefied natural gas is formed by lining the sealing and heat preservation material in the rock mass roadway; and the reservoir of the present application is a complete engineering system including the cavern main body, groundwater control system and freezing circle regulation and control system.

[0068] One of the purposes of this step is to select a suitable site for the underground low-temperature liquefied natural gas reservoir. The conditions for determining whether it is suitable include, for example, whether it meets user demand, geological conditions and support conditions, etc. For example, a roadway can be excavated in the rock mass, the surface of the roadway can be lined with heat insulation, sealing and other materials, and the low-temperature liquid natural gas (also known as liquefied natural gas) can be stored underground.

[0069] In addition, when selecting the site of the underground low-temperature liquefied natural gas reservoir, the location of the reservoir can be determined comprehensively according to the demand of natural gas users, the source of liquefied natural gas and the transportation conditions, etc. Generally, it is selected to be built in an area near a user-concentrated region, a gas pipeline network or a large liquefied natural gas terminal.

[0070] In some embodiments, the step of selecting the rock mass excavation roadway to form the storage cavern of liquefied natural gas includes: selecting the site of the reservoir according to the distribution of natural gas users, the location of a gas pipeline network or a liquefied natural gas terminal; ensuring that the geology of the site of the reservoir meets the geological conditions of no regional fault zone, rock mass uniaxial compressive strength ≥ 30 MPa and permeability coefficient < 10 -7 m / s; excavating the roadway in the rock mass of the site of the reservoir that meets the geological conditions and lining the sealing layer, heat preservation layer and concrete lining layer in layers, for forming the storage cavern for storing the liquefied natural gas.

[0071] For example, the geological conditions for selecting the site of the underground low-temperature liquefied natural gas reservoir generally need to meet the following requirements: there is no regional fault zone through the site of the reservoir, there are few fault fracture zones, the fault throw is small and has no impact on the safety of the reservoir; the rock stratum is stably distributed, the seismic intensity is less than 7 degrees; the rock strength is high, and the uniaxial compressive strength of most of the land is usually higher than 30 MPa; the permeability of the rock mass is low, and the permeability coefficient of most of the land is usually less than 10 -7 m / s. Referring to the drawings shown in Figure 2The figure shows the construction of the underground low-temperature LNG storage, and the excavated cavity is sequentially provided with a sealing layer, a heat preservation layer, a concrete lining layer, a freezing circle and surrounding rock from inside to outside.

[0072] In some embodiments, the freezing circle of the present application is an important sealing structure of the low-temperature LNG. Since the low-temperature LNG is stored in the cavity, even if the heat preservation layer is provided in the tank wall structure, the groundwater will continue to flow from the place with high temperature to the place with low temperature under the action of temperature gradient and freeze, and the volume of the frozen water in the fissure will increase by 1.09 times and cause frost heaving, which will expand the fissure and form the freezing circle, which is an important sealing structure of the underground low-temperature LNG storage.

[0073] In step 120, the storage pressure in the cavity in the pressurized storage state and the storage temperature of the LNG are set, and the temperature of the outer contact surface of the heat preservation layer is set, and the thickness of the heat preservation layer is determined based on the requirement of evaporation loss through thermodynamic calculation.

[0074] In some embodiments, in order to reduce the cold energy consumption power and improve the construction benefit of the underground low-temperature LNG storage, the storage pressure in the cavity of the underground low-temperature LNG storage is set to 1-3 MPa, the storage temperature of the LNG in the cavity is set to -120 to -100℃, and the temperature of the outer contact surface of the heat preservation layer is set to -50 to -30℃. Based on the requirement of the evaporation loss rate (BOR), the thickness of the heat preservation layer is finally determined through the thermodynamic calculation of balancing the leakage and the adiabatic performance. It is worth noting that the above parameters can be calculated and determined according to the energy consumption limit value in actual application to determine the working pressure, storage temperature, contact surface temperature and thickness of the heat preservation layer of the LNG cavity.

[0075] According to the related research of the embodiments of the present application, if the underground low-temperature LNG storage adopts the low-temperature normal-pressure storage mode, the storage temperature of the LNG in the cavity is -162℃, and the storage pressure is basically atmospheric pressure. Due to the effect of convective heat transfer, the cold energy dissipation of the freezing circle is relatively serious, and even reaches 12 kW / d in the initial stage, and the range of the freezing circle is very large, and the diameter even exceeds 8 meters.

[0076] The embodiments of the present application realize the safe storage of the low-temperature LNG at a higher temperature by adopting the pressurized storage mode, thereby significantly reducing the system energy consumption. The theoretical basis of the design lies in the physical property that the boiling point of the main component of the low-temperature LNG, i.e. methane, increases with the increase of the pressure, and the relationship is as follows: Figure 3The boiling point of methane is about -162°C at normal pressure (about 0.1 MPa), which is the conventional cryogenic liquefied natural gas storage temperature. According to the graph, when the storage pressure in the hole is increased to 3 MPa, the boiling point of methane is correspondingly increased to about -100°C. This means that at this pressure, the low-temperature liquefied natural gas only needs to be maintained at -100°C and above to effectively prevent boiling. Therefore, the present application sets the storage temperature to -100°C, so that the temperature difference between the low-temperature liquefied natural gas and the surrounding rock environment is reduced from more than 160°C to about 100°C. The reduction of the temperature difference directly reduces the heat flux density into the cavern through the thermal insulation layer, and fundamentally reduces the evaporation loss (BOR) of the low-temperature liquefied natural gas. This not only reduces the limit requirement for the heat insulation performance of the thermal insulation layer, but also greatly reduces the re-liquefaction energy consumption required for processing the evaporated gas, while reducing the cold energy loss of the surrounding rock cooling due to the controllable freezing circle range, thereby improving the overall energy efficiency and the economy of the construction of the repository from multiple dimensions.

[0077] Referring to the accompanying drawings Figures 4-5 The present application embodiment further models and compares the temperature distribution of the repository under different storage conditions. As can be seen from the graph, the 0°C isotheral of the freezing circle extends to about 8 meters after 90 days of low-temperature storage at normal pressure, and the 0°C isotheral of the freezing circle extends to about 3 meters after 90 days of low-temperature storage at pressure.

[0078] After the present application embodiment is stored at a pressure of 3 MPa, the liquefied natural gas in the hole is stored at a temperature of -100°C. Considering the frost heaving damage of the concrete lining layer and the surrounding rock layer, the temperature of the outer contact surface of the thermal insulation layer is further set to -40°C.

[0079] In an exemplary embodiment, based on the requirement of the evaporation loss rate, the heat leakage and the heat receiving performance are balanced through thermodynamic calculation to finally determine the thickness of the thermal insulation layer.

[0080] For example, in a specific embodiment, the requirement of the evaporation loss rate of the underground low-temperature liquefied natural gas repository can be determined first. Generally, the evaporation loss rate requirement interval of the ground liquefied natural gas tank is 0.05% to 0.15%, and the requirement can also be determined according to the construction scale and economic requirement of the underground low-temperature liquefied natural gas repository. The present embodiment is designed according to the evaporation loss rate limit of 0.1% (i.e. the daily evaporation amount is not more than 0.1% of the volume of the repository), and the heat leakage limit is calculated accordingly, and the thickness of the thermal insulation layer is derived. The specific calculation process includes: first, calculating the volume V of the low-temperature liquefied natural gas repository (V=10×10 4 m 3 ); second, setting the contact surface temperature T 接触面 to -40°C and setting the liquefied natural gas temperature T 液化天然气 in the hole to -100°C, measuring the density p 液化天然气 of the liquefied natural gas (p 液化天然气=450kg / m 3 ) and determination of latent heat of vaporization L v (L) v =510kJ / kg= 51×10 4 J / kg); and then the thickness of the insulation layer is obtained based on the calculated mass flow rate and heat leakage limit.

[0081] For example, calculating mass flow rate includes calculating daily evaporation and converting daily evaporation into mass flow rate Q. evap For example, daily evaporation = BOR × V / 100 = 100m³ 3 / d; converted to mass flow rate is Q. evap = 100m 3 / d×450kg / m 3 =45000kg / d.

[0082] For example, calculating the heat leakage limit includes:

[0083] Calculate the heat input Q corresponding to the evaporation rate. in =Q evap ×L v =45000 kg / d × 510000 J / kg;

[0084] After further standardizing the time unit to seconds, Q in =45000×510000 / 86400≈265625W.

[0085] For example, the insulation layer thickness d is derived based on the following formula:

[0086] ;

[0087] Where d is the thickness of the insulation layer, in meters; The temperature difference between the inside and outside of the insulation layer of a cryogenic liquefied natural gas storage facility; The unit is K, which is 60K in this embodiment; k is the thermal conductivity, with the unit being W / (m·K). The polyurethane foam insulation structure used in this embodiment has a thermal conductivity of 0.015 W / (m·K); A is the surface area of ​​the underground cavern, which is also the total heat dissipation area, with the unit being m². 2 In this embodiment, it is approximately 50,000m 2 Q in This represents the heat input corresponding to the evaporation rate, in W. In this embodiment, it is calculated to be 265625 W.

[0088] In one exemplary embodiment, ,in, These are the contact surface temperature and the liquefied natural gas temperature, respectively.

[0089] In summary, the insulation layer thickness d in this embodiment is calculated as follows:

[0090] .

[0091] In addition, this embodiment of the application also considers the uncertainties such as material aging and construction errors, and the preferred safety margin is 1.2. Finally, the thickness of the insulation layer in this embodiment is 200 mm.

[0092] Step 130: A water replenishment tunnel and water replenishment hole are provided above the storage cavern, and a drainage tunnel and drainage hole are provided below the storage tank and the storage cavern.

[0093] In some embodiments, setting up water replenishment tunnels and water replenishment holes above the storage cavern includes: setting up at least two water replenishment tunnels and multiple water replenishment holes within a range of 15-25 meters above the storage cavern, wherein the diameter of each water replenishment hole is in the range of 90-110 mm, and the depth of each water replenishment hole is less than or equal to 100 meters; the multiple water replenishment holes are staggered at intervals of 10-15 meters, and a rock mass blank area of ​​more than or equal to 2 meters is maintained between adjacent water replenishment holes.

[0094] In some embodiments, the provision of drainage tunnels and drainage holes below the storage tank and the storage cavern includes: providing at least two external drainage tunnels within a range of 10-15 meters below the storage tank (see attached diagram). Figures 6-12 (As shown in the attached diagram); an internal drainage tunnel is constructed below the storage chamber (see attached diagram). Figures 6-12 (As shown in the diagram), the external drainage tunnel and the internal drainage tunnel are connected by multiple drainage holes, which connect one internal drainage tunnel and two external drainage tunnels with a slope of ≥1%. The connection between the internal and external drainage tunnels is a systematic hydraulic connection achieved through a network of drainage holes. Specifically, the drainage hole arrangement logic includes, for example, one internal drainage tunnel located below the storage cavern primarily for directly collecting seepage water from the cavern foundation, while two external drainage tunnels located around the storage area collect regional groundwater; multiple drainage holes are arranged radially (slope ≥1%), extending from the internal drainage tunnel in different directions and connecting to the two external drainage tunnels, forming a branching network of "center-to-periphery flow". Water flow path design includes, for example, the construction of drainage holes in the rock mass by inclined drilling (the slope ensures gravity flow), so that water in the internal tunnels can be naturally guided to the external tunnels through the boreholes; the borehole connection points adopt a branching or manifold design (such as setting up a water collection pit in the internal tunnels and connecting each external tunnel through the borehole branches) to ensure that there are no dead corners in hydraulic coverage.

[0095] In some embodiments, the method further includes: setting up a plurality of upper and lower drainage holes within a 10-meter radius around the storage cavern, wherein each upper and lower drainage hole includes an upper drainage hole and a lower drainage hole, the upper drainage hole being drilled from the water replenishment tunnel, the lower drainage hole being drilled from the drainage tunnel, and the spatial overlap depth of the plurality of upper and lower drainage holes being greater than or equal to 5 meters.

[0096] In one exemplary embodiment, the cryogenic liquefied natural gas storage facility utilizes a groundwater control system to regulate the freezing zone. (See attached diagram.) Figure 6 As shown, based on engineering experience and considering drainage efficiency, at least two water replenishment tunnels are typically installed at an elevation of 15-25 meters above the cryogenic liquefied natural gas (LNG) cavern. Water replenishment holes are drilled between the replenishment tunnels, with a diameter of 90-110 mm and a length not exceeding 100 meters. The spacing between the water replenishment holes is usually between 10-15 meters, and they should be staggered. A minimum of 2 meters of rock mass clearance should be left between adjacent water replenishment holes to avoid excessive rock mass damage caused by complete penetration. At least two drainage tunnels are installed at an elevation of 10-15 meters below the cryogenic LNG storage, and one internal drainage tunnel is installed below the cryogenic LNG cavern to divert groundwater outside the concrete lining layer of the cavern to the internal drainage tunnel. Simultaneously, one external drainage tunnel is constructed on each side of the cryogenic liquefied natural gas (LNG) cavern. The internal and external drainage tunnels are connected by drainage holes with a slope of no less than 1%, the final slope of which can be calculated based on the specific tunnel elevation. Additionally, upper and lower drainage holes are installed within a 10-meter radius around the cryogenic LNG storage facility. The upper drainage holes are drilled from the upper water replenishment tunnel, and the lower drainage holes are drilled from the lower drainage tunnel. The spatial overlap depth of the upper and lower drainage holes should preferably exceed 5 meters to achieve efficient groundwater drainage during construction.

[0097] Step 140: Verify the efficiency of the groundwater control process through multi-stage pumping and drainage tests, and optimize the borehole layout in inefficient areas.

[0098] In some implementations, the efficiency of the groundwater control process is verified through a multi-stage pumping and drainage test, which includes: controlling the closure of all boreholes to measure the initial water head of the groundwater for a period of 3 to 4 days, the purpose of which is to measure during the period of stable seepage; controlling the opening of some boreholes to drain water and verify the drainage efficiency, wherein the upward boreholes are controlled to use gravity drainage and the downward boreholes are controlled to use submersible pumps; controlling the opening of all boreholes to drain water and verify the drainage capacity; and controlling the injection of water into the water replenishment tunnel to simulate heavy rain conditions and test the maximum drainage capacity.

[0099] For example, in a specific implementation, the efficiency of the groundwater control process is calculated by the pumping test, and then the double goals of dewatering the groundwater during construction and replenishing the groundwater during operation are ensured. The areas with low efficiency are suitable for the layout of drainage holes, and the final layout of the groundwater control system is determined. The groundwater control process of the present application also fully considers the seepage characteristics of the natural groundwater system, and combines numerical simulation, theoretical calculation and engineering practice experience, adopts dynamic design and dynamic construction mode, and the final groundwater control system scheme should be finally determined according to the pumping test of the drainage system.

[0100] For example, the pumping test of the groundwater control process of the present application meets the following requirements: verifying the hydraulic connectivity of the groundwater control system, detecting the possible uncontrolled hydrogeological area, deciding whether to add additional pumping holes to improve the system efficiency, and ensuring the double goals of dewatering the groundwater during construction and replenishing the groundwater during operation.

[0101] For example, as shown in Table 1 below, the pumping test method of the drainage system consists of four stages. The first stage is to measure the initial water head to determine the water head change of each hole; the second and third stages are to check the pumping efficiency, and the fourth stage is to simulate the drainage during the rainstorm to evaluate the maximum drainage capacity of the drainage system.

[0102] Table 1: Pumping test stage table of the drainage system

[0103]

[0104] In the test as in Table 1 above, the efficiency of the groundwater control process is judged according to the amount of seepage water in the low-temperature liquefied natural gas tank, the pressure and flow change of each hole, and the change of the seepage point in the tank, and the groundwater control process is optimized according to the need, and the seepage prevention and reduction means such as grouting sealing can also be appropriately supplemented.

[0105] Exemplarily, the staged water drainage process test of the application meets the following comprehensive judgments of multiple principles: the pressure of the second stage closed drainage hole is lower than that of the first stage, which indicates that the working efficiency of the opened drainage hole is high and the hole is not needed to be added temporarily; otherwise, the working efficiency of the opened drainage hole is low and the hole needs to be added to improve the local drainage efficiency; the pressure of each drainage hole in the third stage is reduced to zero, which indicates that the working efficiency is high and the hole is not needed to be added temporarily; otherwise, the hole needs to be added near the drainage hole with pressure to improve the local drainage efficiency; the pressure of each drainage hole in the fourth stage is reduced to zero, which indicates that the working efficiency is high and the hole is not needed to be added temporarily; otherwise, the hole needs to be added near the drainage hole with pressure to improve the local drainage efficiency; if the flow of a certain recharge hole above the reservoir in the fourth stage is significantly lower than the average recharge flow, a recharge hole needs to be added nearby to improve the local recharge capacity; after the completion of each drilling hole, a simple local water drainage system test is performed to check the local water drainage efficiency. The above steps can complete the layout of the underground water control system (for performing the underground water control process of the underground low-temperature liquefied natural gas reservoir) of the underground low-temperature liquefied natural gas reservoir.

[0106] Step 150, controlling water drainage until the fissure water is dewatered to a target state.

[0107] In some embodiments, the controlling water drainage until the fissure water is dewatered to a target state includes: controlling water drainage until the fissure water is dewatered to a state of lowering the underground water level to a predetermined depth below the chamber bottom plate, wherein the predetermined depth is in a range of 8-10 meters.

[0108] Step 160, storing liquefied natural gas and expanding the freezing circle to a target isotherm, stopping water drainage and forming the freezing circle.

[0109] In some embodiments, the storing liquefied natural gas and expanding the freezing circle to a target isotherm, stopping water drainage and forming the freezing circle includes: storing the liquefied natural gas; performing azimuth detection on the position of the freezing circle after storing the liquefied natural gas, until the stopping water drainage is performed after expanding the freezing circle to the target isotherm, for recovering underground water and forming the freezing circle.

[0110] Specifically, the application regulates the freezing circle through the underground water control system, starts water drainage at the beginning of construction to dewater the fissure water in the rock mass, and creates a dry environment for construction; when the low-temperature liquefied natural gas is stored in the cavern tank and the freezing circle has been expanded to the vicinity of the 0°C isotherm, the water drainage is stopped and the underground water is recovered to form the freezing circle.

[0111] Exemplarily, the construction steps of the underground water control system regulating the freezing circle can be divided into steps 151-156 as follows.

[0112] Step 151, referring to the attached Figure 7As shown, before the construction of the low-temperature liquefied natural gas cavern, the underground water in the surrounding rock of the low-temperature liquefied natural gas cavern is dewatered, and the underground water level is lowered to 8-10 meters below the bottom plate of the cavern. The dewatering means can be achieved by setting a dewatering well on the ground, or by converting the functions of the upper water supplementing tunnel and water supplementing hole into water pumping, and discharging the fissure water in the surrounding rock outside through a water pump.

[0113] Step 152, refer to the attached Figure 8 As shown, during the excavation of the low-temperature liquefied natural gas cavern, the underground water in the surrounding rock of the low-temperature liquefied natural gas cavern is continuously dewatered to reduce the risk of cavern excavation.

[0114] Step 153, refer to the attached Figure 9 As shown, after the completion of the construction of the low-temperature liquefied natural gas cavern, the installation of the tank wall sealing system and the access shaft pipeline is carried out, and during this period, the underground water in the surrounding rock of the low-temperature liquefied natural gas cavern is still maintained to reduce the damage of the underground water static pressure to the surrounding rock and the supporting structure.

[0115] Step 154, refer to the attached Figure 10 As shown, the low-temperature liquefied natural gas starts to be stored in the cavern, and from the inside of the cavern, the freezing end continues to conduct outward, combined with the monitoring data of the surrounding temperature monitoring sensor, until the freezing end reaches the vicinity of the preset 0°C isotherm. During this period, the underground water in the surrounding rock of the low-temperature liquefied natural gas cavern is still maintained to lay the foundation for the formation of the subsequent frozen circle.

[0116] Step 155, refer to the attached Figure 11 As shown, due to the unevenness of heat conduction, when the monitoring data of each direction around the low-temperature liquefied natural gas storage shows that the freezing end has reached the vicinity of the 0°C isotherm in this direction, the drainage system in this direction is stopped, and the water supplementing hole above is opened. The local underground water in this direction slowly infiltrates into the cooled rock mass and forms a frozen circle.

[0117] Step 156, refer to the attached Figure 12 As shown, after the underground water level in each direction has been restored and a frozen circle surrounding the cavern has been formed, the frozen circle is finally formed, and the entire drainage system is stopped.

[0118] During the liquefied natural gas storage period, the drainage stage may last for several months or a year, depending on the thermal properties of the surrounding rock and the hydrogeological properties of the local area.

[0119] The application embodiment forms a natural sealing barrier through a rock roadway, forms a self-adaptive freezing circle by using the characteristics of self-expansion of fissure water freezing, significantly improves the stability of the storage structure, and reduces the sensitivity to geological conditions. The application embodiment can be flexibly selected in a stable rock layer area, breaks through the geographical limitations of the traditional storage, and effectively reduces the temperature difference range inside and outside the hole by combining the pressurized storage state with the optimized temperature gradient setting, thereby reducing the loss of cold energy diffusion. The application embodiment dynamically calculates the thickness of the insulation layer based on the evaporation loss requirement, accurately balances the heat insulation performance and economy, and reduces the long-term operation energy consumption from the source. The application embodiment forms a high-efficiency hydraulic regulation network through the upper and lower partitioned water supply and drainage tunnels and boreholes (water supply above and drainage below). The application embodiment guarantees the integrity of the rock structure through the staggered hole design, realizes the directional flow guiding of fissure water through the space coordination control, and provides the basic conditions for the dynamic evolution of the freezing circle. The application embodiment accurately identifies the low-efficiency area through the multi-stage drainage test, and improves the system reliability by targeted drilling. The application embodiment ensures efficient dewatering during the construction period and accurate replenishment during the operation period, and takes into account the engineering safety and long-term sealing requirements. The application embodiment realizes the progressive dewatering of fissure water through the phased drainage control, creates a dry environment for the construction of the hole, and enables the underground water to seep into the cooling rock mass to form a complete freezing circle in the direction of starting and stopping the water supply and drainage system according to the monitoring data at the freezing end after storage, thereby realizing the dynamic and accurate regulation and control of the sealing structure.

[0120] The application embodiment further discloses a regulation and control system for the freezing circle of the fissure surrounding rock of an underground natural gas storage. Referring to FIG. 13, the system comprises a storage construction module 1310, a parameter setting module 1320, a flow distribution module 1330, an efficiency verification module 1340, a construction preparation module 1350, and a dynamic regulation and control module 1360. Figure 13 The storage construction module 1310 is used to select a rock excavation roadway to form a liquefied natural gas storage chamber, and to take the freezing circle formed by the freezing of fissure water in the surrounding rock as a sealing structure.

[0121] The storage construction module 1310 is used to select a rock excavation roadway to form a liquefied natural gas storage chamber, and to take the freezing circle formed by the freezing of fissure water in the surrounding rock as a sealing structure.

[0122] The parameter setting module 1320 is used to set the storage pressure and the storage temperature of the liquefied natural gas in the hole under the pressurized storage state, to set the temperature of the outer contact surface of the insulation layer, and to determine the thickness of the insulation layer through thermodynamic calculation based on the evaporation loss requirement.

[0123] The flow distribution module 1330 is used to set a water supply tunnel and a water supply hole above the storage chamber, and to set a drainage tunnel and a drainage hole below the storage chamber.

[0124] The efficiency verification module 1340 is used to verify the efficiency of the underground water control process through a multi-stage drainage test, and to optimize the drilling arrangement in the low-efficiency area.

[0125] The construction preparation module 1350 is configured to control drainage until the fissure water is dewatered to a target state.

[0126] The dynamic control module 1360 is configured to store liquefied natural gas and expand the freezing circle to a target isotherm, stop the drainage, and form the freezing circle.

[0127] In some embodiments, the storage cavern comprises, from the inside to the outside, a sealing layer, an insulation layer, a concrete lining layer, the freezing circle, and the surrounding rock.

[0128] In some embodiments, the in-cavern storage pressure of the storage cavern ranges from 1 MPa to 3 MPa, the storage temperature of the liquefied natural gas ranges from -120°C to -100°C, and the temperature of the outer contact surface of the insulation layer ranges from -50°C to -30°C.

[0129] The embodiment of the present application is mainly concentrated on the construction types of the existing reserve technology, such as the ground film tank, salt cave gas storage, depleted gas reservoir gas storage, etc. The ground film tank has high construction cost and small scale, and the salt cave gas storage and the depleted gas reservoir gas storage have great limitations in geological structure, geographical resources and location, which are difficult to meet the demand of large-scale underground gas storage construction in the serious gas shortage areas of East China and South China. Therefore, it is of great significance to create a low-temperature liquefied natural gas storage fracture surrounding rock freezing circle dynamic evolution and regulation system, which has great advantages in time scale and space scale and is the best way for long-term large-scale gas storage. The embodiment of the present application solves the problems of small scale, high cost, great limitations in geological conditions and geographical location of the existing gas storage and low-temperature liquefied natural gas storage mode, effectively solves the problems of low-temperature liquefied natural gas storage sealing and stability caused by the difficulty in effectively controlling the 0℃ isotherm of the low-temperature liquefied natural gas storage, and invents a low-temperature liquefied natural gas storage fracture surrounding rock freezing circle dynamic evolution and regulation system. The system solution is complete, which includes the function design of different monomers such as low-temperature liquefied natural gas storage site selection, working pressure and temperature setting, insulation layer calculation, freezing circle control system, efficiency test and construction steps of the underground water control system and important auxiliary design. The system only needs to select a moderate strength and high stability underground space to meet all construction requirements, has high tolerance to geological conditions and wide application range. The embodiment of the present application optimizes important parameters such as storage pressure in the hole, liquefied natural gas storage temperature and contact surface temperature, shortens the range of 0℃ isotherm, reduces cold energy consumption and improves the benefit of gas storage. The underground water control system is set to regulate the freezing circle in six steps to achieve the purpose of accurately regulating the dynamic evolution of the freezing circle. The problems of low-temperature liquefied natural gas storage sealing and stability caused by the difficulty in effectively controlling the 0℃ isotherm of the low-temperature liquefied natural gas storage are effectively solved. The device parameters can be adjusted according to the actual working condition, and the optimization space is large. The embodiment of the present application can not only be applied to liquefied natural gas storage, but also be applied to low-temperature liquefied petroleum gas (LPG storage). It has important value for the space comprehensive utilization of natural gas reserves and energy structure transformation. The embodiment of the present application has the advantages of large scale, strong pertinence, high reliability, convenient operation, low cost and wide application range through the comprehensive use of various underground structures, monomers and materials. It can be quickly applied to the construction of liquefied natural gas storage and liquefied petroleum gas storage and other underground space comprehensive utilization, effectively reduces the storage cost of low-temperature liquefied natural gas, improves the economic benefit of gas storage, and further promotes the healthy development of the industry chain of gas storage and underground space comprehensive utilization.

[0130] The embodiment of the present application also discloses an electronic device integrating the regulation system of the above underground natural gas storage fracture surrounding rock freezing circle, which is used to realize the regulation method of the above underground natural gas storage fracture surrounding rock freezing circle.

[0131] The application has the advantages of high pertinence, high reliability, convenient operation, low cost, wide application range, etc., solves the problems of small scale, high cost and large geographical location limitation of existing liquefied natural gas storage, and invents a complete system solution from the functional design of different monomers such as low-temperature liquefied natural gas storage site selection, working pressure and temperature setting, insulation layer calculation, frozen circle control system, to the efficiency test and construction steps of the underground water control system and other important auxiliary designs, which only needs to select a moderate strength and high stability underground space to meet all construction requirements, has a high tolerance to geological conditions, and has a wide application range. The application provides a complete technology and solution for the dynamic evolution and regulation of the frozen circle of the fractured surrounding rock of the low-temperature liquefied natural gas storage, promotes the long-term and large-scale storage of natural gas and liquefied natural gas, and ensures energy security. According to the construction principle of the low-temperature liquefied natural gas storage and the functional requirements of the frozen circle of the low-temperature liquid storage, the application provides a complete system solution from the functional design of different monomers such as low-temperature liquefied natural gas storage site selection, working pressure and temperature setting, insulation layer calculation, frozen circle control system, to the efficiency test and construction steps of the underground water control system and other important auxiliary designs, which only needs to select a moderate strength and high stability underground space to meet all construction requirements, has a high tolerance to geological conditions, and is suitable for different engineering geology, different hydrogeology, different underground engineering layout and other scenes. Through the integration of various underground monomers, structures and devices, a large-scale, strongly targeted, highly reliable, convenient to operate, low-cost and widely applicable method is provided for the dynamic evolution and regulation of the frozen circle of the fractured surrounding rock of the low-temperature liquefied natural gas storage, which can be quickly applied to various natural gas storage and liquefied natural gas industry chain construction, effectively reduces the storage cost of natural gas and liquefied natural gas, improves economic efficiency, and further promotes the healthy development of the gas storage and abandoned underground space utilization industry chain.

[0132] It can be understood that the above embodiments are only exemplary embodiments adopted to illustrate the principles of the application, but the application is not limited thereto. Various modifications and improvements can be made by those skilled in the art without departing from the spirit and essence of the application, and these modifications and improvements are also considered within the protection scope of the application.

Claims

1. A method of regulating the frozen zone of a fracture surrounding rock of an underground natural gas reservoir, characterized in that, The method comprises the following steps: The rock mass is excavated to form a liquefied natural gas storage cavern, and a freezing circle formed by freezing of fissure water in surrounding rock is used as a sealing structure, wherein the rock mass is excavated to form the liquefied natural gas storage cavern, which comprises: selecting a site according to distribution of natural gas users, a gas pipeline network or a liquefied natural gas terminal location; ensuring that the site has geological conditions of no regional fault zone, rock mass uniaxial compressive strength ≥ 30 MPa and permeability coefficient < 10 -7 m / s; excavating the rock mass at the site to form the cavern and lining the cavern with a sealing layer, a thermal insulation layer and a concrete lining layer in layers to form the liquefied natural gas storage cavern. Setting the storage pressure in the hole and the storage temperature of the liquefied natural gas in the pressurized storage state, and setting the temperature of the outer contact surface of the thermal insulation layer, and determining the thickness of the thermal insulation layer based on the evaporation loss requirement through thermodynamic calculation, wherein the thickness of the thermal insulation layer is derived based on the following formula: ； wherein, is the thickness of the insulation layer; is the temperature difference between the inside and outside of the insulation layer; is the thermal conductivity; is the surface area of the cavity; is the heat input corresponding to the evaporation amount; A water supplementing tunnel and water supplementing holes are arranged above the storage chamber, and a drainage tunnel and drainage holes are arranged below the storage chamber and the storage chamber; The efficiency of the groundwater control process is calculated through a multi-stage drainage test, and the drilling arrangement in the low-efficiency area is optimized; The drainage is controlled until the fissure water is dewatered to a target state; The liquefied natural gas is stored, and the freezing circle is expanded to a target isotherm, the drainage is stopped, and the freezing circle is formed.

2. The method of claim 1, wherein, The water supplementing tunnel and water supplementing holes arranged above the storage chamber comprise: At least two water supplementing tunnels and a plurality of water supplementing holes are arranged in a range of 15-25 meters above the storage chamber, wherein The diameter of each water supplementing hole is in a range of 90-110 mm, and the depth of each water supplementing hole is less than or equal to 100 meters; a plurality of water supplementing holes are arranged in a staggered manner at a spacing of 10-15 meters, and a rock mass blank area with a range greater than or equal to 2 meters is reserved between adjacent water supplementing holes.

3. The method of claim 1, wherein, The drainage tunnel and drainage holes arranged below the storage chamber and the storage chamber comprise: At least two external drainage tunnels are arranged in a range of 10-15 meters below the storage chamber; One internal drainage tunnel is arranged below the storage chamber; The external drainage tunnels and the internal drainage tunnel are connected through a plurality of drainage holes, and the plurality of drainage holes are connected to one internal drainage tunnel and two external drainage tunnels at a slope greater than or equal to 1%.

4. The method of claim 1, wherein, The method further comprises: A plurality of up-and-down drainage holes are arranged in a range of 10 meters around the storage chamber, wherein Each up-and-down drainage hole comprises an upper drainage hole and a lower drainage hole, the upper drainage hole is drilled from the water supplementing tunnel, and the lower drainage hole is drilled from the drainage tunnel, and the spatial overlap depth of a plurality of up-and-down drainage holes is greater than or equal to 5 meters.

5. The method of claim 1, wherein, The efficiency of the groundwater control process is calculated through a multi-stage drainage test, and the drilling arrangement in the low-efficiency area is optimized; The initial water head of the groundwater is measured by controlling to close all the drill holes, and the measurement period is 3-4 days; Part of the drill holes are opened for drainage, and the drainage efficiency is verified, wherein the upward drill holes are controlled to adopt self-flow drainage, and the downward drill holes are controlled to use submersible pumps; All the drill holes are opened for drainage, and the drainage capacity is verified; A control simulation of a rainstorm working condition is performed by water injection through the water supplementing tunnel, and the maximum drainage capacity is tested.

6. The method of claim 1, wherein, The drainage is controlled until the fissure water is dewatered to a target state, which comprises: The drainage is controlled until the fissure water is dewatered to a state in which the groundwater level is lowered to a predetermined depth below the chamber bottom plate, wherein the predetermined depth is in a range of 8-10 meters.

7. The method of claim 1, wherein, The liquefied natural gas is stored, and the freezing circle is expanded to a target isotherm, the drainage is stopped, and the freezing circle is formed. The liquefied natural gas is stored, and the freezing circle is expanded to a target isotherm, the drainage is stopped, and the freezing circle is formed. After the liquefied natural gas is stored, the azimuth detection of the position of the frozen circle is performed until the stop of the drainage after the frozen circle is expanded to the target isotheral line for recovering the underground water and forming the frozen circle.

8. A control system for the frozen zone of fractured surrounding rock in an underground natural gas storage facility, characterized in that, Comprise: The application discloses a method for constructing a liquefied natural gas (LNG) storage cavern, which comprises the following steps: selecting a rock mass to excavate a roadway to form the LNG storage cavern, and taking a frozen circle formed by freezing of fissure water in surrounding rock as a sealing structure, wherein the step of selecting the rock mass to excavate the roadway to form the LNG storage cavern comprises the following steps: selecting a site of the storage cavern according to distribution of natural gas users, a gas pipeline network or a location of an LNG terminal; ensuring that geology of the site meets geological conditions of no regional fault zone, rock mass uniaxial compressive strength ≥ 30 MPa and permeability coefficient < 10 -7 m / s; excavating the roadway in the rock mass of the site meeting the geological conditions and layer by layer lining a sealing layer, a heat preservation layer and a concrete lining layer to form the storage cavern for storing the LNG. The application further discloses a method for constructing a liquefied natural gas (LNG) storage cavern, which comprises the following steps: selecting a rock mass to excavate a roadway to form the LNG storage cavern, and taking a frozen circle formed by freezing of fissure water in surrounding rock as a sealing structure, wherein the step of selecting the rock mass to excavate the roadway to form the LNG storage cavern comprises the following steps: selecting a site of the storage cavern according to distribution of natural gas users, a gas pipeline network or a location of an LNG terminal; ensuring that geology of the site meets geological conditions of no regional fault zone, rock mass uniaxial compressive strength ≥ 30 MPa and permeability coefficient < 10 -7 m / s; excavating the roadway in the rock mass of the site meeting the geological conditions and layer by layer lining a sealing layer, a heat preservation layer and a concrete lining layer to form the storage cavern for storing the LNG. The parameter setting module is used for setting the in-hole storage pressure and the storage temperature of the liquefied natural gas in the pressurized storage state, setting the outer contact surface temperature of the thermal insulation layer, and determining the thickness of the thermal insulation layer based on the thermodynamic calculation according to the evaporation loss requirement, wherein the thickness of the thermal insulation layer is derived based on the following formula: ； wherein, is the thickness of the insulation layer; is the temperature difference between the inside and outside of the insulation layer; is the thermal conductivity; is the surface area of the cavity; is the heat input corresponding to the evaporation amount; The flow layout module is used for setting the water supplementing roadway and the water supplementing hole above the storage cavern, and setting the drainage roadway and the drainage hole below the storage cavern and the storage cavern; The efficiency checking module is used for checking the efficiency of the underground water control process through the multi-stage drainage test, and optimizing the drilling arrangement in the low-efficiency area; The construction preparation module is used for controlling the drainage until the fissure water is drained to the target state; The dynamic regulation and control module is used for storing the liquefied natural gas and expanding the frozen circle to the target isotheral line, stopping the drainage, and forming the frozen circle.

9. The regulation and control system of the frozen circle of the surrounding rock of the underground natural gas storage cavern according to claim 8, characterized in that, The storage cavern comprises a sealing layer, a thermal insulation layer, a concrete lining layer, the frozen circle and the surrounding rock arranged from inside to outside; The in-hole storage pressure of the storage cavern is valued in the range of 1 MPa to 3 MPa, the storage temperature of the liquefied natural gas is valued in the range of -120℃ to -100℃, and the outer contact surface temperature of the thermal insulation layer is -50℃ to -30℃.

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