A method for designing a lower limit operating pressure of a salt cavern storage and related equipment

Abstract

The application discloses a salt cavern storage lower limit operation pressure design method and related equipment, comprising the following steps: obtaining the stratum mechanical parameter of the rock layer where the salt cavern is located and the geometric characteristic parameter of the salt cavern; based on the stratum mechanical parameter and the geometric characteristic parameter, respectively calculating a first pressure threshold value meeting a strength stability condition, a second pressure threshold value meeting a dilatancy sealing condition, and a third pressure threshold value meeting a volume shrinkage economy condition; selecting the maximum value in the first pressure threshold value, the second pressure threshold value and the third pressure threshold value as the lower limit operation pressure of the salt cavern storage; under the premise of ensuring design safety, the application realizes the rapid, economic and accurate design of the lower limit operation pressure of the salt cavern storage by replacing numerical simulation with analytical calculation, and provides an efficient and reliable technical solution for the engineering practice of the salt cavern gas storage.

Description

Technical Field

[0001] This application relates to the field of salt cavern storage technology, and in particular to a method for designing the lower limit operating pressure of a salt cavern storage facility and related equipment. Background Technology

[0002] Salt cavern gas storage facilities are artificial caverns formed by water-soluble extraction from underground salt rock layers, used for strategic reserves of energy sources such as natural gas and compressed air. During the operation of salt cavern storage facilities, the upper limit of operating pressure is limited by the stress of the overlying strata and the formation fracture pressure (usually not exceeding 80%), while the determination of the lower limit of operating pressure directly affects the long-term stability and sealing security of the storage facility. If the lower limit pressure is too low, the salt cavern wall may experience strength failure (collapse), expansion failure (a surge in permeability leading to sealing failure), or excessive creep shrinkage (volume reduction affecting economic efficiency).

[0003] Currently, the mainstream method for determining the lower limit operating pressure in engineering practice is numerical simulation. This method requires establishing a complex three-dimensional geological model, inputting a large number of constitutive parameters, and performing nonlinear iterative solutions. It is not only time-consuming and labor-intensive, with high computational costs, but also heavily reliant on the professional experience of engineers, making it difficult to quickly conduct multi-scheme comparisons in the early stages of a project. Therefore, there is an urgent need for a simple, fast, and engineering-accurate lower limit operating pressure design method that can directly obtain a reasonable design value through analytical calculations, taking into account the three key constraints of strength, expansion, and volume shrinkage, without relying on numerical simulation. Summary of the Invention

[0004] To address the aforementioned issues, this application provides a method and related equipment for designing the lower limit operating pressure of salt cavern storage facilities. While ensuring design safety, it replaces numerical simulation with analytical calculations, achieving rapid, economical, and accurate design of the lower limit operating pressure of salt cavern storage facilities. This provides an efficient and reliable technical solution for the engineering practice of salt cavern gas storage facilities. The technical solution is as follows: This application provides a method for designing the lower limit operating pressure of a salt cavern reservoir, comprising the following steps: obtaining the formation mechanical parameters of the rock strata where the salt cavern is located and the geometric characteristic parameters of the salt cavern; based on the formation mechanical parameters and geometric characteristic parameters, calculating a first pressure threshold satisfying the strength stability condition, a second pressure threshold satisfying the expansion and sealing condition, and a third pressure threshold satisfying the volume shrinkage economy condition; selecting the maximum value among the first, second, and third pressure thresholds as the lower limit operating pressure of the salt cavern reservoir. According to the above embodiment, by decomposing the problem of determining the lower limit operating pressure into three independent constraints—strength stability, expansion and sealing, and volume shrinkage economy—and calculating the corresponding pressure thresholds for each, and finally taking the maximum value of the three as the design value, the effect is to transform the complex multiphysics coupling problem into three independently solvable analytical subproblems. This method avoids the tedious iteration of numerical simulation, achieves rapid analytical calculation of the lower limit pressure, and the "maximum value" logic of the three conditions ensures that the design result simultaneously meets the triple objectives of safety, sealing, and economy.

[0005] For example, in one embodiment of the salt cavern storage lower limit operating pressure design method, the acquisition of formation mechanical parameters and geometric characteristic parameters includes: obtaining the uniaxial compressive strength, triaxial compressive strength, expansion boundary equation parameters, and creep parameters of the salt rock through uniaxial compression tests, triaxial compression tests, and creep tests; obtaining the salt cavern volume through sonar cavity measurement, and calculating the equivalent radius based on the volume. According to the above embodiment, by limiting the specific experimental means (uniaxial / triaxial compression, creep) for acquiring formation mechanical parameters and the specific measurement means (sonar cavity) for acquiring geometric characteristics, the effect is to provide a standardized input data acquisition path for subsequent analytical calculations. These experimental and measurement methods are mature technologies in the field of geotechnical engineering, ensuring the reliability and repeatability of the input parameters, thus enabling this method to... It is engineering-feasible and does not rely on empirical assumptions.

[0006] For example, in one embodiment of the salt cavern storage lower limit operating pressure design method, the strength stability condition is: the stress on the salt cavern wall does not exceed the uniaxial compressive strength of the salt rock; the first pressure threshold is determined based on the difference between the formation stress and the uniaxial compressive strength. According to the above embodiment, by quantifying the strength stability condition as "the wall stress does not exceed the uniaxial compressive strength," and calculating the first pressure threshold accordingly, the effect is to establish a direct linear relationship between strength constraints and internal pressure. This relationship avoids the complex calculations of nonlinear strength criteria; only the difference between the formation stress and the uniaxial compressive strength is needed to quickly obtain the minimum internal pressure that meets the strength requirements, reflecting the engineering simplification of the "safety" design principle.

[0007] For example, in one embodiment of the salt cavern storage lower limit operating pressure design method, the expansion sealing condition is: the stress state of the salt cavern cavity wall is within the safe region defined by the expansion boundary equation of the salt rock; the second pressure threshold is obtained by substituting the cavity wall stress into the expansion boundary equation. According to the above embodiment, by quantifying the expansion sealing condition as "the cavity wall stress state is within the safe region defined by the expansion boundary equation", and calculating the second pressure threshold accordingly, the effect is to transform the physical threshold of expansion failure (leading to a sharp increase in permeability and sealing failure) into a calculable stress boundary. This boundary is based on the expansion equation obtained from triaxial compression tests, which can accurately reflect the transition point of the salt rock from compression to shear dilatation, ensuring that sealing failure will not occur when the internal pressure is not lower than this value.

[0008] For example, in one embodiment of the salt cavern storage lower limit operating pressure design method, the volume shrinkage economic condition is: the volume shrinkage rate after a predetermined number of years of operation does not exceed a preset threshold; the third pressure threshold is calculated based on the salt rock creep constitutive equation and the salt cavern equilibrium equation. According to the above embodiment, by quantifying the volume shrinkage economic condition as "the volume shrinkage rate after a predetermined number of years of operation does not exceed a preset threshold," and calculating the third pressure threshold based on the creep constitutive equation, the effect is to transform the economic requirement of long-term creep shrinkage into a constraint of initial internal pressure. This method considers the time-dependent deformation characteristics of salt rock, enabling the design results to meet the volumetric economic requirements of the entire life cycle of the storage facility, avoiding the loss of usable storage capacity due to excessive shrinkage.

[0009] For example, in one embodiment of the salt cavern storage lower limit operating pressure design method, the predetermined lifespan is 30 years, and the preset threshold is 30%. According to the above embodiment, by further limiting the predetermined lifespan to 30 years and the preset threshold to 30%, the effect is to provide specific engineering quantification indicators. These indicators originate from the conventional design standards of the salt cavern gas storage industry, enabling this method to directly connect with engineering practice. Designers do not need to determine the threshold themselves, thus improving the method's usability.

[0010] For example, in the design method for the lower limit operating pressure of a salt cavern reservoir provided in one embodiment, when the salt cavern is a spherical cavity, the relationship between the volume shrinkage rate and the internal pressure is established using the equilibrium equation and boundary conditions for a spherical cavity; when the salt cavern is a cylindrical cavity, the corresponding equation for a cylindrical cavity is used for solving. According to the above embodiment, by distinguishing between spherical cavities (layered salt caverns) and cylindrical cavities (salt domes) and using the corresponding equilibrium equations respectively, the method's adaptability to different geological conditions and salt cavern morphologies is enhanced. Layered salt caverns in China are mostly spherical / ellipsoidal, while salt dome caverns abroad are mostly cylindrical. This distinction allows the method to be applicable to both mainstream domestic scenarios and typical foreign scenarios, expanding its application scope.

[0011] A second aspect of this application provides a design system for the lower limit operating pressure of a salt cavern reservoir, comprising: a parameter acquisition module for acquiring the formation mechanical parameters of the rock strata where the salt cavern is located and the geometric characteristic parameters of the salt cavern; a pressure calculation module for calculating, based on the formation mechanical parameters and geometric characteristic parameters, a first pressure threshold satisfying the strength stability condition, a second pressure threshold satisfying the expansion sealing condition, and a third pressure threshold satisfying the volume shrinkage economic condition; and a lower limit pressure determination module for selecting the maximum value among the first, second, and third pressure thresholds as the lower limit operating pressure of the salt cavern reservoir. According to the above embodiments, by constructing a system including a parameter acquisition module, a pressure calculation module, and a lower limit pressure determination module, the effect is to solidify the analytical calculation process into a programmable modular architecture. The collaborative work of each module realizes automated processing from raw data input to design result output, eliminating the need for manual intervention in the calculation steps, and providing a technical foundation for subsequent development of dedicated design software or embedding into a reservoir management system.

[0012] For example, in one embodiment of the salt cavern storage lower limit operating pressure design system, the parameter acquisition module includes: a mechanical parameter testing unit for acquiring the mechanical parameters of the salt rock through uniaxial compression tests, triaxial compression tests, and creep tests; and a cavity geometry measurement unit for acquiring the salt cavern volume and calculating the equivalent radius through sonar cavity measurement. According to the above embodiment, by further subdividing the parameter acquisition module into a mechanical parameter testing unit and a cavity geometry measurement unit, the specific method for the system to acquire input data is clarified. This design ensures clear interfaces between the system and external testing equipment and cavity measurement instruments, facilitating integration into actual engineering design processes and improving the system's integrity and practicality.

[0013] A third aspect of this application provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the above-described method. According to the above embodiments, by limiting the storage of the program executing the above method on a computer-readable storage medium, the effect is to extend the scope of protection of the present invention to the software product level. This method program can be pre-installed in engineering computing devices or provided through cloud services, enabling designers to obtain design results without understanding the underlying algorithms, further lowering the technical application threshold.

[0014] This application provides a method and related equipment for designing the lower limit operating pressure of a salt cavern storage facility through some embodiments. By decomposing the complex multiphysics problem into three independent constraints—strength stability, expansion sealing performance, and volume shrinkage economy—and employing a technical approach that combines analytical calculation with a "maximum value" decision-making mechanism, it has the following significant beneficial effects: (1) Significantly improves design efficiency and reduces time and manpower costs: This application abandons the cumbersome process of establishing a three-dimensional geological model, inputting a large number of constitutive parameters, and performing nonlinear iterative solutions in the traditional method. Instead, it directly calculates the pressure threshold corresponding to each constraint through three analytical formulas, and finally takes the maximum value to obtain the lower limit operating pressure. This shortens the numerical simulation work that originally required several hours or even days to minutes of calculation, significantly reducing the design cycle and dependence on the experience of professional personnel. It is especially suitable for rapid comparison of multiple schemes in the early stage of a project.

[0015] (2) Balancing safety, sealing, and economy to ensure the reliability of the storage facility throughout its entire lifecycle: This application sets constraints from three dimensions: strength failure (preventing cavity wall collapse), expansion failure (preventing a sharp increase in permeability leading to sealing failure), and creep shrinkage (preventing volume shrinkage exceeding 30% within 30 years). It also employs a "maximum value" logic to ensure that the design pressure simultaneously meets the most stringent requirement among the three. This multi-condition comprehensive decision-making mechanism avoids the potential shortcomings of single-indicator design, enabling the storage facility to maintain structural stability and sealing integrity while ensuring sufficient economic storage capacity during operation.

[0016] (3) The project is highly operable and the input parameters are standardized: The formation mechanical parameters (uniaxial / triaxial compressive strength, expansion boundary equation parameters, and creep parameters) required by this application can all be obtained through conventional indoor tests, and the geometric characteristic parameters can be obtained through sonar cavity measurement. All inputs are supported by standardized testing methods, which avoids the subjectivity of empirical values ​​and ensures the repeatability and comparability of design results in different projects.

[0017] (4) High adaptability, covering different salt cavern morphologies: This application provides equilibrium equations and solution paths for spherical cavities (suitable for layered salt caverns) and cylindrical cavities (suitable for salt dome salt caverns). This morphological adaptive design enables this method to meet the engineering needs of both domestic and international markets, and has wide applicability. Attached Figure Description

[0018] none Detailed Implementation

[0019] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0020] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0021] This application provides a method for designing the lower limit operating pressure of a salt cavern storage facility: without using numerical simulation, the minimum internal pressure that satisfies each condition is calculated by utilizing the expansion boundary equation of salt rock, the volume shrinkage rate constraint (not exceeding 30% after 30 years of operation), and the strength failure condition. Then, the maximum value among the three is taken as the lower limit operating pressure of the salt cavern storage facility.

[0022] Specifically, the following steps are included: Obtain the mechanical parameters of the strata where the salt cave is located and the equivalent radius of the salt cave; Calculate the minimum internal pressure required to meet the volume shrinkage rate requirement; Calculate the minimum internal pressure required to meet the strength failure requirement; Calculate the minimum internal pressure required to satisfy the expansion boundary requirements; Compare the three minimum internal pressures mentioned above, and take the maximum value as the lower limit operating pressure of the salt cavern storage.

[0023] The formation mechanical parameters were obtained through laboratory rock mechanics tests, and specifically included: Uniaxial compression test: to obtain the uniaxial compressive strength of salt rock (Chinese salt rock is usually about 20 MPa).

[0024] Triaxial compression test: The triaxial compression strength under different confining pressures was obtained, and the expansion boundary equation of the salt rock was obtained by fitting the results.

[0025] Creep test: to obtain the creep parameters of salt rock.

[0026] Geometric feature parameter acquisition: The volume of the salt cavern is measured using sonar cavity measurement technology. For spherical salt caverns, the equivalent radius is calculated by inversely using the formula for the volume of a sphere.

[0027] When the salt cavern is spherical (radius a): List the constitutive equations for a spherical salt cave: (If the salt cave is cylindrical, the corresponding formulas can also be used to solve it) (1) (2) (3) (4) In the formula, u represents displacement, r is radial distance, and A* and n are creep parameters. It is radial stress. It is circumferential stress. It is the polar stress, T is the temperature, R is the gas constant, and Q is the corresponding activation energy.

[0028] The equilibrium equation for the spherical cavity is: (5) This represents the derivative of radial stress with respect to radial distance.

[0029] Considering the stress at infinity to be constant as the formation stress, and the stress on the cavity wall to be the applied stress, the boundary conditions for the spherical cavity are: (6) (7) It is the radial stress located on the cavity wall. Indicates the intracavitary pressure. Represents the radial stress at infinity. This indicates formation stress.

[0030] Considering spherical symmetry, we can obtain: (8) (9) J2 is the second invariant of the deviatoric stress tensor.

[0031] Salt rock undergoes creep shrinkage, leading to a reduction in the volume of the salt cavern. To meet economic requirements, the volume shrinkage rate is typically required to be no less than 30% after 30 years of operation. This application uses the constitutive and equilibrium equations of a spherical salt cavern to calculate the minimum internal pressure required to satisfy this volume shrinkage rate. The solution yields the volume shrinkage rate and stress characteristics of the salt cavern: (10) V is the volume of the salt cavern. It is the derivative of the salt cavern volume with time. It is the difference between the ground stress at a distance and the pressure inside the cavity: (11) (12) This represents the time derivative of the displacement on the wall of the salt cavern.

[0032] (13) (14) (15) (16) (17) (18) Strength failure requirement: The internal pressure of the salt cavern must not fall below a certain minimum value; otherwise, the rock will break down, causing the salt cavern to collapse and threatening its stability. For spherical salt caverns, the stress state at the cavity wall under the action of formation stress at infinity and internal pressure can be solved using elasticity mechanics.

[0033] Stress expression on the wall of the salt cavern: (19) (20) I1 is the first invariant of the principal stresses.

[0034] The strength failure condition requires that the maximum principal stress does not exceed the uniaxial compressive strength of the salt rock, and the minimum internal pressure is calculated from this.

[0035] Expansion refers to the critical point at which the volume of salt rock changes from compression to expansion under deviatoric stress. Once expansion occurs, the rock permeability will increase sharply, leading to the failure of the salt cavern's seal. Therefore, the internal pressure of the salt cavern must not be less than the minimum value corresponding to the expansion boundary.

[0036] The formula derivation in this application is based on the assumption of a spherical cavity and is applicable to layered salt caves (approximately spherical in shape). If the salt cave is cylindrical (such as the salt caves in a salt dome), a similar solution can be obtained using the corresponding equilibrium equations and boundary conditions for cylindrical cavities.

[0037] Application Cases 1. Obtain the mechanical parameters of the strata where the salt cave is located and the equivalent radius of the salt cave. Through indoor experiments, uniaxial compression, triaxial compression, and creep tests were conducted to obtain the formation mechanical parameters of the salt rock, including uniaxial compressive strength (the uniaxial compressive strength of salt rock is typically around 20 MPa, which is taken as 20 MPa for convenience), and triaxial compression dilatation point (according to the domestic dilatation boundary equation). The creep parameter A* = 9.8 × 10⁻⁶ -6 MPa -n / a -1n=4. The volume of the salt cavern is obtained by sonar measurement (assuming the cavity depth is 1000m and the equivalent radius is a=30m), and then the equivalent radius is calculated.

[0038] 2. Calculate the minimum internal pressure that satisfies the volume shrinkage rate requirement.

[0039] The required minimum internal pressure can be calculated by back-calculating the formation mechanical parameters. It can be calculated using the following formula (10). Minimum internal pressure.

[0040] (10) Solving this problem yields the following results: Therefore, the minimum internal pressure must not be less than 2.6 MPa.

[0041] 3. Calculate the minimum internal pressure that does not meet the failure requirements. The required minimum internal pressure is calculated by back-calculating the formation mechanical parameters.

[0042] The ground stress at 1000m is approximately 23MPa. Considering the uniaxial compressive strength is 20MPa, the internal pressure is not... It should be less than 3 MPa.

[0043] 4. Calculate the minimum internal pressure that does not meet the expansion requirements. By conducting triaxial compression tests under different confining pressures, the expansion equation for salt rock can be obtained, and the following can be calculated in reverse: Minimum internal pressure required.

[0044] (19) (20) Substituting the solutions, we get: The pressure must not be lower than 4.83 MPa.

[0045] 5. Select the minimum pressure that meets the requirements. The maximum value among the three was selected as 4.83 MPa, which meets the requirements for the salt cavern gas storage facility. The minimum internal pressure is 4.83 MPa.

[0046] This application uses analytical calculations instead of numerical simulations to quickly and economically determine the salt cavern storage capacity. Lower limit operating pressure. In application cases, only the formation mechanical parameters and equivalent radius need to be substituted, and the design result can be obtained through a few algebraic calculations, avoiding the complex modeling and long-term iterative calculations of numerical simulation, thus significantly improving design efficiency. At the same time, this method considers the constraints of strength, sealing, and economy, ensuring the safety and economy of the design result.

[0047] To implement the above method, a design system for the lower limit operating pressure of a salt cavern storage facility can be constructed, including: Parameter acquisition module: used to acquire the mechanical parameters of the strata where the salt cave is located and the equivalent radius of the salt cave; Pressure calculation module: used to calculate the minimum internal pressure that meets the strength failure condition, expansion boundary condition, and volume shrinkage rate condition respectively; Lower limit pressure determination module: used to select the maximum value among the three as the lower limit operating pressure.

[0048] The system can be deployed in computer equipment and run as software to achieve automated design.

[0049] Although the embodiments of this application have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for this application. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, this application is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A method for designing the lower limit operating pressure of a salt cavern storage facility, characterized in that, Includes the following steps: Obtain the stratigraphic mechanical parameters of the rock strata where the salt cave is located and the geometric characteristic parameters of the salt cave; Based on the aforementioned formation mechanical parameters and geometric characteristic parameters, the first pressure threshold satisfying the strength stability condition, the second pressure threshold satisfying the expansion and sealing condition, and the third pressure threshold satisfying the volume shrinkage economy condition are calculated respectively. The maximum value among the first pressure threshold, the second pressure threshold, and the third pressure threshold is selected as the lower limit operating pressure of the salt cavern storage.

2. The method for designing the lower limit operating pressure of a salt cavern storage facility according to claim 1, characterized in that, The acquisition of formation mechanical and geometric parameters includes: obtaining the uniaxial compressive strength, triaxial compressive strength, expansion boundary equation parameters, and creep parameters of the salt rock through uniaxial compression tests, triaxial compression tests, and creep tests; obtaining the salt cavern volume through sonar cavity measurement, and calculating the equivalent radius based on the volume.

3. The method for designing the lower limit operating pressure of a salt cavern storage facility according to claim 1, characterized in that, The strength stability condition is: the stress on the wall of the salt cavern does not exceed the uniaxial compressive strength of the salt rock; the first pressure threshold is determined based on the difference between the formation stress and the uniaxial compressive strength.

4. The method for designing the lower limit operating pressure of a salt cavern storage facility according to claim 1, characterized in that, The expansion sealing condition is: the stress state of the salt cavern wall is within the safe area defined by the expansion boundary equation of the salt rock; the second pressure threshold is obtained by substituting the wall stress into the expansion boundary equation for back calculation.

5. The method for designing the lower limit operating pressure of a salt cavern storage facility according to claim 1, characterized in that: The economic condition for volume shrinkage is: the volume shrinkage rate after the salt cavern has been in operation for a predetermined number of years does not exceed a preset threshold; the third pressure threshold is calculated based on the salt rock creep constitutive equation and the salt cavern equilibrium equation.

6. The method for designing the lower limit operating pressure of a salt cavern storage facility according to claim 5, characterized in that: The predetermined period is 30 years, and the preset threshold is 30%.

7. The method for designing the lower limit operating pressure of a salt cavern storage facility according to claim 1, characterized in that: When the salt cavern is a spherical cavity, the relationship between the volume shrinkage rate and the internal pressure is established using the equilibrium equation and boundary conditions for a spherical cavity; when the salt cavern is a cylindrical cavity, the corresponding equation for a cylindrical cavity is used for solving.

8. A design system for the lower limit operating pressure of a salt cavern storage facility, characterized in that, include: The parameter acquisition module is used to acquire the stratigraphic mechanical parameters of the rock strata where the salt cave is located and the geometric characteristic parameters of the salt cave. The pressure calculation module is used to calculate, based on the formation mechanical parameters and geometric characteristic parameters, a first pressure threshold that satisfies the strength stability condition, a second pressure threshold that satisfies the expansion and sealing condition, and a third pressure threshold that satisfies the volume shrinkage economy condition. The lower limit pressure determination module is used to select the maximum value among the first pressure threshold, the second pressure threshold, and the third pressure threshold as the lower limit operating pressure of the salt cavern storage.

9. The system according to claim 8, characterized in that, The parameter acquisition module includes: The mechanical parameter testing unit is used to obtain the mechanical parameters of salt rock through uniaxial compression tests, triaxial compression tests, and creep tests. The cavity geometry measurement unit is used to obtain the salt cave volume and calculate the equivalent radius by measuring the cavity with sonar.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the program implements the steps of the method according to any one of claims 1 to 7.

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