Method for evaluating water seal safety of multi-stage adjacent caverns

Abstract

The application relates to the technical field of groundwater sealed caverns, in particular to a water sealing safety evaluation method for multi-period adjacent caverns. The water sealing safety evaluation method for multi-period adjacent caverns mainly comprises engineering geological feature and hydrogeological feature analysis, multi-period adjacent cavern water sealing safety influence parameter inversion, multi-period adjacent cavern multi-working condition numerical analysis and multi-period adjacent cavern water sealing safety influence evaluation and the like, realizes comprehensive evaluation on the water sealing safety of multi-period adjacent caverns under various different working conditions, and improves the reliability, actual value, reference and guidance value of the water sealing safety evaluation method.

Description

Technical Field

[0001] This application relates to the field of underground water-sealed cavern technology, and in particular to a method for evaluating the water-sealed safety of multiple adjacent caverns. Background Technology

[0002] Currently, my country's dependence on imported oil has reached as high as 70%, highlighting the urgent need to increase oil reserves. Underground water-sealed oil depots have become the primary method of oil storage due to their advantages of safety, economy, and high land utilization. However, these depots have stringent site requirements, needing to be built within crystalline rock formations in areas with abundant groundwater. Suitable sites in China are limited. To fully utilize geological conditions and reduce investment costs, expansion near existing caverns can be considered. However, construction near already operational caverns inevitably impacts the water seal safety of those caverns. Furthermore, underground water-sealed oil depots generally employ the "gap storage with water replenishment" principle for underground oil storage, effectively preventing oil leakage. However, ensuring the safety of the water seal is crucial for the safe operation of these depots. While research on the water seal safety of underground caverns under equivalent continuous media is relatively mature, there is limited research on water seal safety evaluation systems considering discrete network models for adjacent caverns. Such evaluation systems, however, offer more practical guidance. Summary of the Invention

[0003] The purpose of this application is to provide a method for evaluating the water seal safety of adjacent caverns in multiple phases, so as to improve the reliability of the water seal safety evaluation of adjacent caverns and its practical reference and guidance value.

[0004] The water seal safety evaluation method for multiple adjacent caverns provided in this application includes:

[0005] Step 100: Engineering geological and hydrogeological feature analysis, including collecting and analyzing engineering geological and hydrogeological feature information of the existing cavern and the surrounding area of ​​the proposed expansion site.

[0006] Step 200: Inversion of water seal safety impact parameters of adjacent caverns in multiple phases, including randomly selecting a verification area for verification within the proposed expansion site area; establishing a three-dimensional random fracture network model based on the engineering geological and hydrogeological characteristics of the verification area; determining water seal safety impact parameters from the engineering geological and hydrogeological characteristics; and performing trial calculations on the three-dimensional random fracture network model based on the water seal safety impact parameters and seepage index; using machine learning to fit the relationship curve between the water seal safety impact parameters and the seepage index based on the trial calculation model results; and then combining the seepage of the hydrological test project in the field to invert and verify the water seal safety impact parameters.

[0007] Step 300: Numerical analysis of multiple phases of adjacent caverns under multiple working conditions. First, a three-dimensional model of multiple phases of adjacent caverns is established based on the engineering geological features and hydrogeological features of the existing caverns and the site selection area to be expanded. Then, numerical simulation calculation of water seal safety impact parameters is performed on the different working conditions of the existing caverns and the caverns to be expanded under multiple phases of adjacent caverns.

[0008] Step 400: Evaluation of the impact of water seal safety on adjacent caverns in multiple phases. Based on the numerical analysis results of the water seal safety impact parameters, the water seal safety of the adjacent caverns in multiple phases is evaluated according to the water seal safety evaluation standard.

[0009] Furthermore, the engineering geological feature information includes stratigraphic lithology information, geological structural information, and joint and fracture information.

[0010] The hydrogeological characteristics include groundwater level distribution characteristics, groundwater occurrence conditions, and groundwater distribution patterns.

[0011] The collection of the lithological information of the strata includes collecting information on the types of strata and surrounding rocks, as well as collecting information on the physical and mechanical parameters of strata and surrounding rocks through field testing;

[0012] The collection of geological structural information includes collecting and analyzing the development of fault and fracture zones and joint fracture zones within the existing cavern and its surrounding area within the proposed expansion site. The information on the development of fault and fracture zones includes their distribution location, scale, strike, dip and dip angle.

[0013] Information on the development of the joints and fissures is collected, including their distribution location, size, orientation, dip, dip angle, and density.

[0014] Furthermore, the water seal safety impact parameters include fracture density, fracture size, fracture tendency, and fracture dip angle;

[0015] Step 200 includes randomly generating joint groups that conform to statistical parameters based on the water seal safety impact parameters, forming a fracture network model by mutual intersecting, establishing the three-dimensional random fracture network model, and performing trial calculations on each fracture network model; combining the seepage volume, inverting the water seal safety impact parameters, and verifying the feasibility of numerical simulation of water seal safety in adjacent caverns over multiple periods.

[0016] Furthermore, in step 300, the three-dimensional model of the multi-phase adjacent cavern is established using 3DEC discrete element numerical simulation software, the parameters of the fault and joint fracture zone are set separately, and the random fracture network model of the rock mass is generated using the DFN model.

[0017] Furthermore, the constitutive model of the block of the multi-phase adjacent cave three-dimensional model is selected as an elastoplastic model, and the constitutive model of the joints of the multi-phase adjacent cave three-dimensional model is selected as the joint surface contact Coulomb slip model.

[0018] Furthermore, in step 300, the operating conditions of the different chambers of the multi-phase adjacent caverns are divided into four types: the first type is that the previous phase was an oil storage and operation cavern, and the current phase is an oil storage and operation cavern; the second type is that the previous phase was an oil storage and operation cavern, and the current phase is a fully excavated cavern; the third type is that the previous phase was an oil-free cavern, and the current phase is a fully excavated cavern; and the fourth type is that the previous phase was an oil-free cavern, and the current phase is an oil storage and operation cavern.

[0019] Furthermore, in step 300, before performing numerical calculations for different working conditions of the multiple adjacent caverns, disconnected micro-isolated dead fractures are eliminated.

[0020] Before performing numerical calculations for different working conditions of the multiple adjacent caverns, pressure boundary conditions are set for the caverns under different working conditions of the multiple adjacent caverns.

[0021] The pressure boundary condition sets the grid nodes around the fully excavated cavern to 0 pressure and the grid nodes around the oil-free cavern to 0 pressure.

[0022] Furthermore, the oil storage section pressure P0 of the operating cavern conforms to the formula:

[0023] P0 = P g +(30-za)*8722*10 -6 ;

[0024] The groundwater pressure P in the operating cavern w Conforms to the formula:

[0025] P w =P g +[(30-ab)*8722+(bz)*9800]*10 -6 ;

[0026] Among them, P g For the nitrogen section pressure, P g =0.1~0.3MPa; z is the height of the cavern;

[0027] a represents the height of the nitrogen section, a = 0.1–0.3 m; b represents the height of the groundwater, b = 0.1–0.5 m.

[0028] Furthermore, in step 400, the safety impact assessment of the water seal in the multi-phase adjacent cavern includes selecting water seal safety assessment indicators. Based on the discrete network model, the groundwater level, fissure water pressure, instantaneous flow rate, seepage volume, and seepage flow line are selected as the water seal safety assessment indicators.

[0029] The groundwater level includes the thickness of the water cap layer and the groundwater level drawdown funnel above the cavern. The evaluation criteria for the thickness of the water cap layer are: the thickness of the water cap layer in the oil storage and operation cavern is greater than 40m, and the thickness of the water cap layer in the fully excavated cavern is greater than 20m.

[0030] The evaluation criterion for the fissure water pressure is: the water pressure in each fissure around the cavern is greater than the pressure inside the cavern.

[0031] The evaluation criteria for the instantaneous flow rate and seepage volume are as follows: the total seepage volume of the cavern per 1 million m³ 3 Storage capacity less than or equal to 200m 3 / d;

[0032] The seepage flow lines include the seepage direction and seepage velocity of groundwater in the fissures. The evaluation criteria for the seepage flow lines are: the seepage direction of the fissures connected to the cavern is towards the interior of the cavern, and each fissure connected to the cavern has a certain seepage velocity.

[0033] Furthermore, the water seal safety evaluation method also includes step 500, analysis of the mutual influence of multiple adjacent caverns, which analyzes the influence of the current cavern in fully excavated or oil-storage operation conditions on the surrounding fissure water pressure of the previous cavern in oil-free or oil-storage operation conditions based on the tendency, dip angle, and tangential relationship between the fissure and the cavern, as well as the connectivity factors of the fissure.

[0034] Compared with existing technologies, this application considers a three-dimensional random fracture network model and uses machine learning to fit the relationship curves between water seal safety impact parameters and seepage volume of a large number of trial models. Combined with the seepage volume of the field hydrological test project, it inverts the water seal safety impact parameters of multiple adjacent caverns, providing a strong reference for the inversion of water seal safety impact parameters of underground caverns considering three-dimensional random fractures. It can be used to invert the water seal safety impact parameters of underground caverns considering three-dimensional random fractures, improving the reliability of the three-dimensional random fracture model. Multiple water seal safety evaluation indicators are selected as evaluation criteria to comprehensively evaluate the water seal safety of multiple adjacent caverns under various working conditions, providing a more practically valuable method for the construction design of actual cavern expansion. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0036] Figure 1 This is an overall flowchart of the water seal safety evaluation method for multiple adjacent caverns provided in the embodiments of this application;

[0037] Figure 2 This is a flowchart of step 100 of the water seal safety evaluation method provided in the embodiments of this application;

[0038] Figure 3 This is a flowchart of step 200 of the water seal safety evaluation method provided in the embodiments of this application;

[0039] Figure 4 This is a flowchart of step 300 of the water seal safety evaluation method provided in the embodiments of this application;

[0040] Figure 5 This is a flowchart of step 400 of the water seal safety evaluation method provided in the embodiments of this application;

[0041] Figure 6 This is a flowchart of step 500 of the water seal safety evaluation method provided in the embodiments of this application;

[0042] Figure 7 This is a diagram illustrating the cavern oil storage operation mode provided in the embodiments of this application;

[0043] Figure 8 The curve showing the relationship between tunnel wall pressure and tunnel wall height provided in the embodiments of this application;

[0044] Figure 9for Figure 8 A magnified curve of point A in the middle;

[0045] Figure 10 for Figure 8 A magnified curve of point B in the middle. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0047] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0048] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0049] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this application is in use. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0050] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0051] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0052] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0053] like Figures 1 to 6 As shown in the embodiment of this application, a method for evaluating the water seal safety of multiple adjacent caverns is provided, which may include:

[0054] Step 100: Engineering geological and hydrogeological characteristics analysis, including collecting and analyzing engineering geological and hydrogeological characteristics information of the existing cavern and the surrounding area of ​​the proposed expansion site.

[0055] Among them, such as Figure 2 As shown, the engineering geological features include stratigraphic lithology, geological structure, and joint and fracture information; the hydrogeological features include groundwater level distribution characteristics, groundwater occurrence conditions, and groundwater distribution patterns; the stratigraphic lithology information collected includes the classification of strata and surrounding rocks and the physical and mechanical parameters of strata and surrounding rocks obtained through field testing; the geological structure information collected includes the collection, analysis, and statistical analysis of the development of fault and fracture-dense zones and joint-fracture zones within the proposed expansion site area surrounding the existing cavern; the information on the development of fault and fracture-dense zones includes their distribution location, scale, strike, dip, and dip angle; the information on the development of joints and fractures includes their distribution location, scale, strike, dip, dip angle, and density.

[0056] The method provided in this application takes into account and collects a large amount of feature information, which makes the simulation of the subsequently established three-dimensional random fracture network model and the three-dimensional model of multiple adjacent caverns more accurate and the evaluation results more valuable.

[0057] Step 200: Inversion of water seal safety impact parameters in adjacent caverns across multiple phases. This includes randomly selecting verification areas within the proposed expansion site area, establishing a three-dimensional stochastic fracture network model based on the engineering geological and hydrogeological characteristics of the verification areas, determining water seal safety impact parameters from the engineering geological and hydrogeological characteristics, and performing trial calculations on the three-dimensional stochastic fracture network model based on the water seal safety impact parameters and seepage rate index. Based on the trial calculation model results, a machine learning method is used to fit the relationship curve between the water seal safety impact parameters and the seepage rate index. Finally, the water seal safety impact parameters are inverted and verified by combining the seepage rate of the hydrological test project tested on-site.

[0058] Among them, such as Figure 3 As shown, based on the basic principles of the Monte Carlo method, considering the mean, probability, and variance of the structural surface linear density and the direction, dip, and inclination angle of fractures, the fracture density, fracture size, fracture dip, and fracture inclination angle are selected as the water seal safety influence parameters in this embodiment. Joint groups that conform to statistical parameters are randomly generated and intersected to form a fracture network model. A three-dimensional random fracture network model is established, and a large number of fracture network models are tested. Based on the results of a large number of test models, machine learning is used to fit the relationship curve between the water seal safety influence parameters and the seepage index. Combined with the seepage volume of the hydrological test project in the field, the water seal safety influence parameters are inverted to verify the feasibility of numerical simulation of the water seal safety of adjacent caverns in multiple periods.

[0059] Before establishing a large-scale three-dimensional model of adjacent caverns in multiple phases and conducting numerical simulation calculations of water seal safety impact parameters, a relatively simple three-dimensional stochastic fracture network model is first developed for the planned area of ​​adjacent existing caverns in a relatively small range, and the model is then inverted and verified to confirm the feasibility of the model and the selected water seal safety impact parameters. Subsequent large-scale numerical analysis of adjacent caverns in multiple phases under multiple working conditions is then carried out to reduce the probability of trial and error and improve efficiency.

[0060] Step 300: Numerical analysis of multiple phases of adjacent caverns under multiple working conditions. First, a three-dimensional model of multiple phases of adjacent caverns is established based on the engineering geological and hydrogeological characteristics of the existing caverns and the site selection area for expansion. Then, numerical simulation calculations of water seal safety impact parameters are performed on the different working conditions of the existing caverns and the caverns to be expanded.

[0061] Preferably, the three-dimensional model of the multi-phase adjacent cavern is established using 3DEC discrete element numerical simulation software. The parameters of the fault and joint fracture zone are set separately, and a random fracture network model of the rock mass is generated using the DFN model. This DFN model is affected by the independent statistical distribution of each parameter. Based on random seed values, any number of DFN models are generated. The constitutive model of the block of the aforementioned three-dimensional model of the multi-phase adjacent cavern is selected as an elastoplastic model, and the constitutive model of the joints of the three-dimensional model of the multi-phase adjacent cavern is selected as the joint surface contact Coulomb slip model.

[0062] Among them, such as Figure 4 As shown, the working conditions of different chambers in multiple adjacent underground caverns can be divided into four types: the first type is that the previous period was an oil storage and operation cavern, and the current period is an oil storage and operation cavern; the second type is that the previous period was an oil storage and operation cavern, and the current period is a fully excavated cavern; the third type is that the previous period was an oil-free cavern, and the current period is a fully excavated cavern; the fourth type is that the previous period was an oil-free cavern, and the current period is an oil storage and operation cavern. Here, the previous period refers to the caverns of the existing underground caverns, and the current period refers to the caverns of the underground caverns to be expanded in this phase.

[0063] Preferably, before performing numerical calculations for different working conditions in multiple adjacent caverns, disconnected micro-isolated dead fractures can be eliminated to improve computational efficiency. Pressure boundary conditions are set for the caverns under different working conditions in multiple adjacent caverns. The pressure boundary conditions set the grid nodes surrounding fully excavated caverns to 0 pressure, and the grid nodes surrounding oil-free caverns to 0 pressure, such as... Figures 7 to 10 As shown, Figure 7 It can intuitively describe the cavern wall pressure under the operational status of oil storage in caverns, and intuitively simulate the additional cavern wall pressure on the cavern model. Figure 8 This represents the relationship curve between cavern wall pressure and cavern height. Figure 9 and Figure 10 They are Figure 8 Enlarged details of point A (gas storage) above the central cavern and point B (water storage) below the cavern, providing a more comprehensive and realistic depiction of the oil storage conditions under additional pressure on the cavern walls during oil storage operations. Figure 10 In this context, "oil storage extension" refers to the cavern wall pressure if the water cushion portion is oil, and "water cushion" refers to the cavern wall pressure if the water cushion is water. Preferably, the pressure-related values ​​surrounding the oil storage operating cavern are set as follows:

[0064] The oil storage section pressure P0 of the oil storage operating cavern conforms to the formula:

[0065] P0 = P g +(30-za)*8722*10 -6 ;

[0066] Groundwater pressure P in oil storage and operation caverns w Conforms to the formula:

[0067] Pw =P g +[(30-ab)*8722+(bz)*9800]*10 -6 ;

[0068] Among them, P g For the nitrogen section pressure, P g =0.1~0.3MPa, P is preferred g =0.2MPa; z is the cavern height; a is the nitrogen section height, a = 0.1~0.3m, preferably a = 0.2m; b is the groundwater height, b = 0.1~0.5m, preferably b = 0.5m, where “8722” is the oil specific weight and “9800” is the water specific weight.

[0069] Step 400: Evaluation of the impact of water seal safety on multiple adjacent caverns. Based on the numerical analysis results of the water seal safety impact parameters, the water seal safety of multiple adjacent caverns, including existing caverns and caverns to be expanded, is evaluated according to the water seal safety evaluation standard.

[0070] Among them, such as Figure 5 As shown, the multi-phase adjacent cavern water seal safety impact assessment includes selecting water seal safety evaluation indicators, comparing the similarities and differences between the equivalent continuous medium model and the discrete network model in the underground cavern water seal safety assessment, and, based on the characteristics of the discrete network model, excluding inapplicable evaluation indicators such as vertical hydraulic gradient, selecting groundwater level, fissure water pressure, instantaneous flow rate, seepage volume, and flow lines as water seal safety evaluation indicators; the groundwater level includes the overall water cap thickness and the groundwater level drawdown funnel above the cavern, and the evaluation standard for groundwater level is: the water cap thickness of the oil storage and operation cavern. The depth of the water cover layer in a fully excavated tunnel should be greater than 40m, and the depth should be greater than 20m. The smaller the drawdown cone above the tunnel, the better, to prevent the formation of a drainage zone. The fissure water pressure refers to the water pressure in each fissure surrounding the tunnel. The evaluation criterion is that the water pressure in each fissure around the tunnel is greater than the pressure inside the tunnel, and the nearest pressure contour above the tunnel should not show a significant drawdown cone to prevent the formation of a low-pressure interconnection zone. The evaluation criteria for instantaneous flow rate and seepage volume are: each fissure connected to the tunnel must have a certain flow rate, and the total seepage volume of the tunnel should be less than 1 million m³. 3 The storage capacity should not exceed 200m³. 3 / d; The flow line includes the direction and velocity of groundwater seepage in the fissure. The evaluation criteria for the flow line are: the flow direction of the fissure connected to the cavern must be towards the interior of the cavern, and each fissure connected to the cavern must have a certain flow velocity.

[0071] Step 500: Analysis of the mutual influence of adjacent caverns in multiple phases. Unlike the equivalent continuous medium model, this step requires considering factors such as the tendency, dip angle, tangential relationship between the spatial fractures and the cavern, and the connectivity of the fractures. Based on these factors, the analysis examines the impact of the current cavern in fully excavated or oil-storage operation conditions on the surrounding fissure water pressure of the previous cavern in oil-free or oil-storage operation conditions. The analysis also examines the impact of the previous cavern in oil-free or oil-storage operation conditions on the surrounding fissure water pressure of the current cavern in fully excavated or oil-storage operation conditions.

[0072] This application's embodiments consider a three-dimensional random fracture network model and employ machine learning to fit the relationship curves between water seal safety impact parameters and seepage volume of a large number of trial models. Combined with the seepage volume of the field hydrological test project, the water seal safety impact parameters of multiple adjacent caverns were inverted. This provides a strong reference for the inversion of water seal safety impact parameters of underground caverns considering three-dimensional random fractures, and can be used to invert the water seal safety impact parameters of underground caverns considering three-dimensional random fractures, thereby improving the reliability of the three-dimensional random fracture model. The water seal safety of multiple adjacent caverns under various working conditions was comprehensively evaluated using groundwater level, fracture water pressure, instantaneous flow rate, seepage volume, and seepage streamlines, providing a more practically valuable method for the construction design of actual cavern expansion.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for evaluating the water seal safety of multi-phase adjacent caverns, characterized in that, include: Step 100: Engineering geological and hydrogeological feature analysis, including collecting and analyzing engineering geological and hydrogeological feature information of the existing cavern and the surrounding area of ​​the proposed expansion site. Step 200: Inversion of water seal safety impact parameters of adjacent caverns in multiple phases, including randomly selecting a verification area for verification within the proposed expansion site area; establishing a three-dimensional random fracture network model based on the engineering geological and hydrogeological characteristics of the verification area; determining water seal safety impact parameters from the engineering geological and hydrogeological characteristics; and performing trial calculations on the three-dimensional random fracture network model based on the water seal safety impact parameters and seepage index; using machine learning to fit the relationship curve between the water seal safety impact parameters and the seepage index based on the trial calculation model results; and then combining the seepage of the hydrological test project in the field to invert and verify the water seal safety impact parameters. Step 300: Numerical analysis of multiple phases of adjacent caverns under multiple working conditions. First, a three-dimensional model of multiple phases of adjacent caverns is established based on the engineering geological features and hydrogeological features of the existing caverns and the site selection area to be expanded. Then, numerical simulation calculation of water seal safety impact parameters is performed on the different working conditions of the existing caverns and the caverns to be expanded under multiple phases of adjacent caverns. Step 400: Evaluation of the impact of water seal safety on adjacent caverns in multiple phases. Based on the numerical analysis results of the water seal safety impact parameters, the water seal safety of the adjacent caverns in multiple phases is evaluated according to the water seal safety evaluation standard.

2. The water seal safety evaluation method according to claim 1, characterized in that, The engineering geological features include stratigraphic lithology information, geological structure information, and joint and fracture information. The hydrogeological characteristics include groundwater level distribution characteristics, groundwater occurrence conditions, and groundwater distribution patterns. The collection of the lithological information of the strata includes collecting information on the types of strata and surrounding rocks, as well as collecting information on the physical and mechanical parameters of strata and surrounding rocks through field testing; The collection of geological structural information includes collecting and analyzing the development of fault and fracture zones and joint fracture zones within the existing cavern and its surrounding area within the proposed expansion site. The information on the development of fault and fracture zones includes their distribution location, scale, strike, dip and dip angle. Information on the development of the joints and fissures is collected, including their distribution location, size, orientation, dip, dip angle, and density.

3. The water seal safety evaluation method according to claim 2, characterized in that, The parameters affecting water seal safety include fracture density, fracture size, fracture tendency, and fracture dip angle; Step 200 includes randomly generating joint groups that conform to statistical parameters based on the water seal safety impact parameters, forming a fracture network model by mutual intersecting, establishing the three-dimensional random fracture network model, and performing trial calculations on each fracture network model; combining the seepage volume, inverting the water seal safety impact parameters, and verifying the feasibility of numerical simulation of water seal safety in adjacent caverns over multiple periods.

4. The water seal safety evaluation method according to claim 2, characterized in that, In step 300, the three-dimensional model of the multi-phase adjacent cavern is established using 3DEC discrete element numerical simulation software. The parameters of the fault and joint fracture zone are set separately, and the random fracture network model of the rock mass is generated using the DFN model.

5. The water seal safety evaluation method according to claim 4, characterized in that, The constitutive model of the block in the multi-phase adjacent cave three-dimensional model is an elastoplastic model, and the constitutive model of the joints in the multi-phase adjacent cave three-dimensional model is a joint surface contact Coulomb slip model.

6. The water seal safety evaluation method according to claim 1, characterized in that, In step 300, the operating conditions of different chambers in the multi-phase adjacent caverns are divided into four types: the first type is that the previous phase was an oil storage and operation cavern, and the current phase is an oil storage and operation cavern; the second type is that the previous phase was an oil storage and operation cavern, and the current phase is a fully excavated cavern; the third type is that the previous phase was an oil-free cavern, and the current phase is a fully excavated cavern; and the fourth type is that the previous phase was an oil-free cavern, and the current phase is an oil storage and operation cavern.

7. The water seal safety evaluation method according to claim 6, characterized in that, In step 300, before performing numerical calculations for different working conditions of the multiple adjacent caverns, disconnected micro-isolated dead fractures are eliminated. Before performing numerical calculations for different working conditions of the multiple adjacent caverns, pressure boundary conditions are set for the caverns under different working conditions of the multiple adjacent caverns. The pressure boundary condition sets the grid nodes around the fully excavated cavern to 0 pressure and the grid nodes around the oil-free cavern to 0 pressure.

8. The water seal safety evaluation method according to claim 7, characterized in that, The oil storage section pressure P0 of the operating cavern conforms to the formula: P0=P g +(30-za)*8722*10 -6 ; The groundwater pressure P in the operating cavern w Conforms to the formula: P w =P g +[(30-a-b)*8722+(b-z)*9800]*10 -6 ; Among them, P g For the nitrogen section pressure, P g =0.1~0.3MPa; z is the height of the cavern; a represents the height of the nitrogen section, a = 0.1–0.3 m; b represents the height of the groundwater, b = 0.1–0.5 m.

9. The water seal safety evaluation method according to claim 6, characterized in that, In step 400, the safety impact assessment of the water seal in the multi-phase adjacent cavern includes selecting water seal safety assessment indicators. Based on the discrete network model, the groundwater level, fissure water pressure, instantaneous flow rate, seepage volume, and seepage flow line are selected as the water seal safety assessment indicators. The groundwater level includes the thickness of the water cap layer and the groundwater level drawdown funnel above the cavern. The evaluation criteria for the thickness of the water cap layer are: the thickness of the water cap layer in the oil storage and operation cavern is greater than 40m, and the thickness of the water cap layer in the fully excavated cavern is greater than 20m. The evaluation criterion for the fissure water pressure is: the water pressure in each fissure around the cavern is greater than the pressure inside the cavern. The evaluation criteria for the instantaneous flow rate and seepage volume are as follows: the total seepage volume of the cavern per 1 million m³ 3 Storage capacity less than or equal to 200m 3 / d; The seepage flow lines include the seepage direction and seepage velocity of groundwater in the fissures. The evaluation criteria for the seepage flow lines are: the seepage direction of the fissures connected to the cavern is towards the interior of the cavern, and each fissure connected to the cavern has a certain seepage velocity.

10. The water seal safety evaluation method according to claim 6, characterized in that, It also includes step 500, an analysis of the mutual influence of adjacent caverns in multiple phases. Based on the dip direction and angle of the spatial fractures, the tangential relationship between the fractures and the caverns, and the connectivity factors of the fractures, it analyzes the influence of the current cavern in fully excavated or oil-storage operation conditions on the surrounding fracture water pressure of the previous cavern in oil-free or oil-storage operation conditions; and analyzes the influence of the previous cavern in oil-free or oil-storage operation conditions on the surrounding fracture water pressure of the current cavern in fully excavated or oil-storage operation conditions.

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