Membrane-free sealing structure of underground ultralow-temperature storage cavern and construction method of membrane-free sealing structure

Abstract

The invention discloses a membrane-free sealing structure of an underground ultralow-temperature storage cavern and a construction method of the membrane-free sealing structure. The membrane-free sealing structure of the underground ultra-low temperature storage cavern comprises a sealing heat preservation layer, a lining layer, a surrounding rock grouting strengthening belt and a freezing ring which are all of ring layer structures, the outer layer sequentially wraps the inner layer structure, the lining layer wraps the sealing heat preservation layer, the surrounding rock grouting strengthening belt wraps the lining layer, and the freezing ring wraps the sealing heat preservation layer. And a low-temperature-resistant surrounding rock grouting material is injected into the rock-soil body of the surrounding rock grouting strengthening zone and is solidified to block the leakage channel, the surrounding rock grouting strengthening zone is coated with the freezing ring, and the leakage channel is blocked through water in pores and cracks of the low-temperature freezing rock-soil body. According to the method, relevant parameters are adopted, cold energy dissipation is combined, the sealing heat preservation layer is calculated, and the material parameters and the structure thickness with the most excellent economic performance are obtained. The membrane-free structure of the underground low-temperature storage cavern is achieved, harm caused by a metal lining is reduced, meanwhile, cold energy consumption is reduced, the operation cost is reduced, and feasibility in engineering and economy is achieved.

Description

Technical Field

[0001] The present invention relates to the field of underground energy storage technology, and in particular to a membrane-free sealing structure for underground storage of ultra-low temperature media such as liquefied natural gas (LNG) and liquid hydrogen (LH2) and a construction method thereof. Background Art

[0002] Driven by the goal of carbon neutrality, underground storage of clean energy such as liquid hydrogen and liquefied natural gas has become the core infrastructure of energy transformation. Such storage needs to maintain an ultra-low temperature environment below -150°C for a long time. However, the polymer flexible membranes relied on by traditional sealing solutions have fatal defects at extremely low temperatures: the membrane material becomes brittle and shrinks, resulting in a decrease in tensile strength, and the leakage rate increases exponentially with decreasing temperature. Even more serious is that existing technologies separate sealing and energy consumption: to compensate for leakage losses, the energy consumption of the refrigeration system accounts for more than 30% of the total cost, forming a vicious cycle of "leakage → cooling → energy consumption surge". The industry urgently needs a membrane-free sealing technology that can resist low-temperature deformation and coordinate energy consumption control.

[0003] Currently, membraneless sealing technology primarily focuses on single-dimensional improvements, failing to overcome the dual bottlenecks of "low-temperature adaptability" and "energy efficiency." Consequently, safety and cost constraints hinder the widespread application of underground ultra-low-temperature storage in large-scale energy storage projects.

[0004] As underground gas storage develops towards ultra-low temperatures and high pressures, its structural safety faces even more severe challenges. Despite continuous advancements in underground space development technology, research on the long-term safety of storage facilities under complex conditions during the cyclic charging and discharging of high-pressure working fluids remains severely insufficient. Existing technologies lack a systematic understanding of the synergistic mechanism of storage seals and energy consumption. This technological gap has led to an over-reliance on empirical formulas in storage design, making it difficult to predict the seal degradation laws under multi-field coupling, further restricting the large-scale safe application of ultra-low temperature storage facilities.

[0005] Therefore, it is necessary to design a membrane-free sealing structure and method for an underground ultra-low temperature storage to solve the above technical problems. Summary of the Invention

[0006] (1) Technical issues to be solved

[0007] The purpose of the present invention is to provide a membrane-free sealing structure and method for an underground ultra-low temperature storage, which not only overcomes the fatal defect of the membrane material embrittlement and shrinkage in the structure causing the leakage rate to increase exponentially, but also provides a method for recycling the dissipated cold energy, realizes the combination of sealing and energy consumption, improves the safety performance and economic benefits of the underground ultra-low temperature storage, and provides a method for the application of the underground ultra-low temperature storage.

[0008] (2) Technical solution

[0009] In order to solve the above technical problems, the first aspect of the present invention proposes a membrane-less sealing structure for an underground ultra-low temperature storage tank, wherein the sealing structure is a ring structure covering the ultra-low temperature storage tank, and comprises a sealing insulation layer, a lining layer, a surrounding rock grouting reinforcement belt and a freezing ring from the inside to the outside; the lining layer is a complete artificially constructed low-permeability shell, which is used for sealing and pressure maintenance, and serves as a pressure vessel for the storage tank; the surrounding rock grouting reinforcement belt is formed by pressurized injection of ultra-low temperature resistant surrounding rock grouting material into the rock and soil, and is used to reduce the escape of internal gas; the freezing ring is formed by freezing groundwater, and is used to reduce the infiltration of groundwater and the escape of internal gas.

[0010] According to a preferred embodiment of the present invention, the sealing and thermal insulation layer is composed of foam concrete.

[0011] According to a preferred embodiment of the present invention, the surrounding rock grouting reinforcement zone is formed by injecting ultra-low temperature resistant surrounding rock grouting material into the rock and soil of the surrounding rock grouting reinforcement zone and solidifying it to block the leakage channel.

[0012] According to a preferred embodiment of the present invention, the sealing structure also includes pipelines, including pipelines for an exhalation safety valve, an inhalation safety valve, and an air supply system. These pipelines penetrate the sealing and insulation layer, the lining layer, the surrounding rock grouting reinforcement zone, and the top of the freezing ring, connecting the ultra-low temperature storage tank with other surface facilities and equipment.

[0013] Another aspect of the present invention provides a construction method for membrane-free sealing of an underground ultra-low temperature storage, comprising the following steps:

[0014] S1. Determine the dimensions and construction materials of each part of the underground ultra-low temperature storage through physical model tests;

[0015] S2. The cavern, sealing and insulation layer, lining layer and surrounding rock grouting reinforcement zone of the ultra-low temperature storage at the construction site;

[0016] S3. Installing a cryogenic storage tank in the cavern and installing pipes and pipelines connecting the cryogenic storage tank and the ground, and debugging the pipes and pipelines;

[0017] S4. Injecting ultra-low temperature liquid into the ultra-low temperature storage tank, thereby forming a freezing zone around the surrounding rock grouting reinforcement zone.

[0018] According to a preferred embodiment of the present invention, the method further comprises step S5, monitoring the internal pressure of the storage tank in the reservoir and the temperature in the membraneless sealing structure to ensure that the pressure is maintained within a safe range.

[0019] According to a preferred embodiment of the present invention, step S1 includes:

[0020] S1.1. Create a physical model of the underground ultra-low temperature storage facility and use it to determine the material type and ratio of the sealing and insulation layer;

[0021] S1.2. Establish a numerical model of the underground ultra-low temperature storage, input the obtained material type and ratio of the sealing and thermal insulation layer into the numerical model, and calculate the temperature field based on the conservation of energy;

[0022] S1.3. Calculate the size of the freezing zone based on the predetermined freezing zone permeability requirements and temperature field.

[0023] According to a preferred embodiment of the present invention, in step S1.2,

[0024] The position of the temperature line that reaches the required permeability of the freezing zone is calculated using the following permeability calculation formula:

[0025]

[0026] Where w u is the unfrozen water content, w u =e 2(T-0) ;k r0 is the permeability of the grouting-reinforced zone of the unfrozen surrounding rock;

[0027] By publishing the temperature field calculated by S1.2, the range of the freezing zone that meets the requirements can be directly obtained.

[0028] According to a preferred embodiment of the present invention, the sealing and heat-insulating layer is a single layer or multiple layers.

[0029] (3) Beneficial effects

[0030] The membrane-free sealing structure and construction method of the underground ultra-low temperature storage system proposed in this invention eliminate the traditional metal membrane layer, eliminating the risk of leakage caused by metal embrittlement and shrinkage in ultra-low temperature environments. Furthermore, by combining energy consumption calculations and utilizing the storage material, thickness, and dissipated cold energy, cryosphere regulation is achieved, improving storage safety and energy utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a front view schematic diagram of an embodiment of the reservoir system structure of the present invention;

[0032] Figure 2 A schematic three-dimensional cross-sectional view of an embodiment of a reservoir system structure of the present invention;

[0033] Figure 3 This is a construction flow chart of an embodiment of the ultra-low temperature underground storage of the present invention.

[0034] Flowchart of a method for testing the evolution of a cryosphere model of a low-temperature energy underground storage reservoir according to an embodiment of the present invention

[0035] In the figure: 101, sealing and insulation layer; 102, lining layer; 103, surrounding rock grouting reinforcement belt; 104, freezing circle; 105, air supply system; 106, intake safety valve; 107, exhalation safety valve. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0037] The embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0038] Figure 1 and Figure 2 They are respectively a front view schematic diagram and a three-dimensional cross-sectional schematic diagram of an embodiment of the storage system structure of the present invention. Figures 1 to 2 As shown, the ultra-low temperature storage system is set in the soil stratum and built below the groundwater level. It can be used to store low-temperature liquefied gases such as liquefied natural gas (LNG), liquid hydrogen (LH2), and liquid nitrogen (LN2).

[0039] In this embodiment, the reservoir is specifically located in underground rock formations or mountains, and avoids adverse geological areas such as fault fracture zones. Figure 1 and Figure 2 As shown, the outside of the cavern of the storage system structure is composed of a sealing and thermal insulation layer 101, a lining layer 102, a surrounding rock grouting reinforcement zone 103 and a freezing ring 104 from the inside to the outside.

[0040] In this embodiment, the sealing and thermal insulation layer 101 is made of foam concrete, which can be sulphoaluminate cement-based + hollow glass microspheres, which has low thermal conductivity and good thermal insulation performance. At the same time, a gradient setting can also be used to meet different needs.

[0041] The sealing and insulating layer 101 is located inside the space enclosed by the lining layer 102. The lining layer 102 includes but is not limited to concrete, steel grid, reinforced concrete, and steel lining. The surrounding rock grouting materials injected into the surrounding rock and soil in the surrounding rock grouting reinforcement belt 103 include but are not limited to mortar and chemical slurry.

[0042] In this embodiment, the sealing and insulation layer 101 serves as the primary insulation structure. It ensures that the temperature transferred to the lining layer 102 is appropriate, preventing low temperatures from damaging the structure. The lining layer 102 is a complete, artificially constructed low-permeability shell, serving as the first barrier. The surrounding rock grouting reinforcement band 103 is the second barrier, using artificial slurry pressurized and injected into the surrounding rock and soil to fill cracks in the rock and soil, improving its integrity and blocking leakage channels. The freezing ring 104 is the third barrier, using low temperatures to freeze water in the pores and cracks of the rock and soil, thereby blocking leakage channels. Underground rock and soil, due to its low ground temperature fluctuations and low thermal conductivity, is a natural cold-insulating material. The thick rock and soil layer composed of the lining layer 102, surrounding rock grouting reinforcement band 103, and freezing ring 104 serves as the second cold-insulating barrier.

[0043] In this embodiment, the freezing circle 104 is formed by groundwater freezing under the influence of escaping cold energy. In order to solve the problems of long formation time and cold energy dissipation of the freezing circle 104, it is necessary to slow down the groundwater flow rate to ensure the stability of the freezing circle 104.

[0044] like Figure 1 and Figure 2 As shown, the sealing structure also includes pipelines, including an exhalation safety valve, an inhalation safety valve, and an air supply system pipeline. The exhalation safety valve 107, the inhalation safety valve 106, and the air supply system pipeline 105 pass through the sealing and insulation layer 101, the lining layer 102, the surrounding rock grouting reinforcement belt 103, and the top of the freezing ring 104, connecting the sealing and insulation layer 101 with other facilities and equipment on the ground.

[0045] In this embodiment, the buried depth and cross-sectional area of ​​the reservoir cavern can be determined comprehensively based on the specific conditions of the construction location, such as topography, geology, groundwater, surrounding rock parameters, ground stress, and reservoir pressure.

[0046] The second aspect of the present application provides a construction method for a membrane-free sealing structure of an underground ultra-low temperature storage, which adopts the above-mentioned membrane-free sealing structure for an underground ultra-low temperature storage. In general, the present invention first determines the material ratio through physical experiments to ensure that the material still has the required physical performance indicators in an ultra-low temperature environment; then, the parameters obtained from the physical experiment are input into the numerical model, and based on the principle of conservation of energy, the dissipation range of cold energy within a set time range (i.e., the boundary of the 0°C isotherm) is calculated, and this range can be controlled by adjusting the thickness of the insulation layer; and then the permeability of the cryosphere is calculated to determine its scale (i.e., the thickness of the cryosphere); the formation time and scale of the cryosphere are calculated through simulation, thereby determining the required thickness of the insulation layer; finally, the actual storage is constructed according to the structural dimensions of each layer obtained by simulation. The following is still explained through specific embodiments.

[0047] Figure 3 The following is a flow chart of the construction method of the underground ultra-low temperature storage of the present invention. Figure 3 As shown, the construction method includes the following steps:

[0048] Step S1: Determine the dimensions and construction materials of each part of the underground ultra-low temperature storage.

[0049] This step is the design step before formal construction, which includes the following sub-steps:

[0050] S1.1. Create a physical model of the underground ultra-low temperature storage tank and use this physical model to determine the material type and ratio of the sealing and insulation layer.

[0051] This step requires a physical model of the cryogenic reservoir, which is then used to conduct sealing tests on the insulation layer. During the physical model test, the physical and mechanical properties of the surrounding rock and engineering structure, as well as similarity theory, are used to determine the physical and mechanical properties of the similar materials used in the sealing test. The appropriate type and proportion of similar materials are then determined through testing.

[0052] S1.2. Establish a numerical model of the underground ultra-low temperature storage, input the material type and ratio of the sealing and thermal insulation layer obtained in step S1.1 into the numerical model, and use the numerical model to calculate the temperature field.

[0053] The temperature field is calculated using the energy conservation equation:

[0054]

[0055] Where, (ρC) eff is the equivalent heat capacity; ρ ω is the density of water; C ω is the specific heat capacity of water; u is the Darcy velocity vector; is the temperature gradient; q is the heat conduction flux.

[0056] S1.3. Calculate the size of the freezing zone based on the predetermined freezing zone permeability requirements and temperature field.

[0057] The calculated isothermal zone is used to calculate the size of the freezing zone.

[0058] In this embodiment, the lining layer is constructed of low-temperature resistant reinforced concrete, the relevant material parameters of which are well known in the art, and the thickness is set to 20 cm; the thickness of the surrounding rock grouting reinforcement zone is determined based on the thickness of the freezing circle plus 1 m, and the remaining parameters are pre-set according to engineering requirements.

[0059] In this embodiment, the freezing zone permeability is required to be less than 10 -4 mD, from which the scale of the frozen zone, that is, its thickness, can be determined.

[0060] Specifically, the thicker the freezing zone, the more significant the decrease in rock permeability. The position of the temperature line that reaches the freezing zone permeability requirement is calculated using the following permeability calculation formula:

[0061]

[0062] Where k r is the permeability of the frozen zone, w u is the unfrozen water content, w u =e 2(T-0) ;k r0 It is the permeability of the grouting reinforcement zone of the unfrozen surrounding rock.

[0063] The above formula can be used to calculate the temperature range that meets the freezing zone permeability requirements. Then, using the temperature field calculated in S1.2, the freezing zone range that meets the requirements can be directly obtained.

[0064] Determine the appropriate formation time of the freezing ring 104, determine the thickness of the sealing and thermal insulation layer according to the determined thickness of the freezing ring, and find the optimal thickness of the sealing and thermal insulation layer 101;

[0065] For example, in this embodiment, based on the physical and mechanical properties of the surrounding rock and engineering structure and similarity theory, the material of the sealing and thermal insulation layer 101 is determined to be sulfoaluminate cement-based + hollow glass microspheres; based on the determined size of the reservoir cavern, the material ratio of the sealing and thermal insulation layer 101 and the working conditions, the temperature field is calculated in combination with numerical simulation to determine the temperature isothermal range; based on the surrounding rock grouting reinforcement zone 103, the sealing performance of the freezing circle 104 and the isothermal range of the temperature field, the scale of the freezing circle 104 is determined to be 1.5m; and the appropriate formation time of the freezing circle 104 is determined, and finally the thickness of the sealing and thermal insulation layer 101 is determined to be 50cm.

[0066] S2. Construction site of the ultra-low temperature storage cavern, sealing insulation layer, lining layer and surrounding rock grouting reinforcement zone.

[0067] This step first involves excavating a vertical shaft and a cavern. In one embodiment, the vertical shaft and the main cavern are excavated in stable rock formations at selected locations, and temporary support is implemented simultaneously to ensure stability during the construction period.

[0068] Next, a low-temperature resistant grout is injected into the rock mass surrounding the cavern under high pressure to fill the rock cracks and form a surrounding rock grouting reinforcement zone 103. This step also includes placing temperature sensors in the surrounding rock grouting reinforcement zone 103 and the area where the freezing zone 104 is expected to form.

[0069] Then, a lining layer 102 is constructed on the inner wall of the cavern.

[0070] Finally, the thermal insulation layer 101 is installed on the inner side of the lining layer 102 .

[0071] S3. Install ultra-low temperature storage tanks in the cavern and install pipes and pipelines connecting the ultra-low temperature storage tanks and the ground, and debug the pipes and pipelines.

[0072] In this embodiment, the storage tank containing the cryogenic liquid is installed in the cavern. Next, the pipes and pipelines connecting the tank to the surface are installed. These pipelines include the air supply system 105, the inhalation safety valve 106, and the exhalation safety valve 107. After installation, the exhalation safety valve 107, the inhalation safety valve 106, and the air supply system 105 pipeline are debugged to ensure that the valves in the pipelines meet the required response.

[0073] S4. Injecting ultra-low temperature liquid into the ultra-low temperature storage tank, thereby forming a freezing zone around the surrounding rock grouting reinforcement zone.

[0074] In this embodiment, the injected ultra-low temperature liquid is liquefied natural gas. In this step, liquid nitrogen is first injected into the sealing and insulating layer 101 for pre-cooling to ensure that the temperature drop rate is not too fast, and then the liquefied natural gas is injected into the storage tank.

[0075] Since the present invention utilizes anti-seepage, the flow rate of groundwater is slowed down, and the cold energy required to form the freezing circle 104 is reduced.

[0076] Step S5: Monitor the internal pressure of the storage tank in the reservoir and the temperature in the membraneless sealing structure to ensure that the pressure is maintained within a safe range.

[0077] During this step, the internal pressure of the storage tank in the reservoir is maintained by the exhalation safety valve 107 , the inhalation safety valve 106 , and the air supply system 105 .

[0078] At the same time, the temperature of the surrounding rock grouting reinforcement zone 103 and the freezing circle 104 is monitored by using the arranged temperature monitoring points to maintain the temperature at a predetermined temperature, and emergency treatment is carried out in time when an abnormality occurs.

[0079] The pressure changes in the reservoir caused by the injection and extraction of low-temperature liquefied gas and the daily generation of boil-off gas in the reservoir are regulated by the gas supply system 105. When the pressure in the reservoir drops, the long tube of the gas supply system 105 is used to replenish gas. When the pressure in the reservoir rises, the short tube of the gas supply system 105 is used to recover the boil-off gas, which is then recondensed into low-temperature liquefied gas and injected back into the interior of the reservoir 101. At the same time, the recovery of boil-off gas can not only reduce the damage caused by internal pressure to the reservoir, but also cool the boil-off gas back to liquid form, reducing the waste of liquid energy when leaving the reservoir. If an abnormal situation occurs during the operation of the reservoir, causing the reservoir pressure to be lower than or higher than the design pressure, the suction safety valve 106 or the exhalation safety valve 107 is triggered to start, ensuring that the reservoir operates under a safe pressure.

[0080] In the description of this application, the specific material selection of the structure is only an example and can be replaced according to specific requirements during implementation.

[0081] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An underground ultra-low temperature storage membrane-free sealing structure, characterized by: The sealing structure is a ring structure covering the ultra-low temperature storage tank, which includes a sealing insulation layer, a lining layer, a surrounding rock grouting reinforcement belt and a freezing ring from the inside out; The lining layer is a complete artificial low-permeability shell used for sealing and pressure maintenance, and serves as a pressure vessel for the reservoir; The surrounding rock grouting reinforcement zone is formed by pressurizing and injecting ultra-low temperature resistant surrounding rock grouting material into the rock and soil to reduce the escape of internal gas; The freezing circle is formed by freezing groundwater and is used to reduce the infiltration of groundwater and the escape of internal gas.

2. The membrane-free sealing structure of the underground ultra-low temperature storage according to claim 1 is characterized in that: The sealing and heat-insulating layer is made of foam concrete.

3. The membrane-free sealing structure of the underground ultra-low temperature storage according to claim 2 is characterized in that: The surrounding rock grouting reinforcement zone is formed by injecting ultra-low temperature resistant surrounding rock grouting material into the rock and soil of the surrounding rock grouting reinforcement zone and solidifying it to block the leakage channel.

4. The membrane-less sealing structure of the underground ultra-low temperature storage according to claim 2 is characterized in that: The sealing structure also includes pipelines, which include pipelines for an exhalation safety valve, an inhalation safety valve, and an air supply system. Each pipeline connects the ultra-low temperature storage tank with other facilities and equipment on the ground by passing through the sealing insulation layer, the lining layer, the surrounding rock grouting reinforcement belt, and the top of the freezing circle.

5. A construction method for membrane-free sealing of underground ultra-low temperature storage, characterized in that: The following steps are involved: S1. Determine the dimensions and construction materials of each part of the underground ultra-low temperature storage through physical model tests; S2. The cavern, sealing and insulation layer, lining layer and surrounding rock grouting reinforcement zone of the ultra-low temperature storage at the construction site; S3. Installing a cryogenic storage tank in the cavern and installing pipes and pipelines connecting the cryogenic storage tank and the ground, and debugging the pipes and pipelines; S4. Injecting ultra-low temperature liquid into the ultra-low temperature storage tank, thereby forming a freezing zone around the surrounding rock grouting reinforcement zone.

6. The membrane-free sealing construction method for underground ultra-low temperature storage according to claim 5, characterized in that: Also includes: Step S5: Monitor the internal pressure of the storage tank in the reservoir and the temperature in the membraneless sealing structure to ensure that the pressure is maintained within a safe range.

7. The membrane-free sealing construction method for underground ultra-low temperature storage according to claim 5 or 6, characterized in that: Step S1 includes: S1.

1. Create a physical model of the underground ultra-low temperature storage facility and use it to determine the material type and ratio of the sealing and insulation layer; S1.

2. Establish a numerical model of the underground ultra-low temperature storage, input the obtained material type and ratio of the sealing and thermal insulation layer into the numerical model, and calculate the temperature field based on the conservation of energy; S1.

3. Calculate the size of the freezing zone based on the predetermined freezing zone permeability requirements and temperature field.

8. The membrane-free sealing construction method for underground ultra-low temperature storage according to claim 7, characterized in that: In step S1.2, The temperature field is calculated using the energy conservation equation: Where, (ρC) eff is the equivalent heat capacity; ρ ω is the density of water; C ω is the specific heat capacity of water; u is the Darcy velocity vector; is the temperature gradient; q is the heat conduction flux.

9. The membrane-free sealing construction method for underground ultra-low temperature storage according to claim 8, characterized in that: In step S1.3, The position of the temperature line that reaches the required permeability of the freezing zone is calculated using the following permeability calculation formula: Where k r is the permeability of the frozen zone, w u is the unfrozen water content, w u =e 2(T-0) , k r0 The permeability of the unfrozen, grouting-reinforced zone of the surrounding rock; By publishing the temperature field calculated by S1.2, the range of the freezing zone that meets the requirements can be directly obtained.

10. The membrane-free sealing construction method for underground ultra-low temperature storage according to claim 9, characterized in that: The sealing and heat-insulating layer is a single layer or multiple layers.

Images