A method and system for optimal cavern construction for salt cavern small molecule gas storage

Abstract

The application discloses a salt cave small-molecule gas storage cavity construction and cavity distribution preferred method and system, comprising the following steps: obtaining basic geological data of a target salt layer, screening the target salt layer according to a preset storage constraint condition, and reserving a salt layer area meeting the constraint condition; dividing a plurality of candidate cavity construction horizons in the screened salt layer area; establishing a hierarchical analysis evaluation index system for the small-molecule gas storage, and determining the weight of each evaluation index; for each candidate cavity construction horizon, constructing a geomechanics model under a unified target cavity volume and operation pressure system; mapping geological indexes and geomechanics response parameters into standardized evaluation scores through a continuous function; according to the weight and the standardized evaluation scores, calculating a comprehensive suitability index of each candidate cavity construction horizon, and determining a preferred cavity construction horizon; dividing a plurality of candidate cavity distribution units in the preferred cavity construction horizon, and repeating the geomechanics calculation and evaluation steps for each candidate cavity distribution unit to determine an optimal cavity distribution position.

Description

Technical Field

[0001] This application relates to the field of underground gas storage site selection and geological engineering technology, and in particular to a method and system for optimizing the cavity layout of a salt cavern small molecule gas storage facility. Background Technology

[0002] Salt cavern underground storage facilities are widely used in the natural gas storage field due to their advantages such as good sealing performance, high injection and production efficiency, and strong peak-shaving capacity. With the increasing demand for hydrogen energy development and utilization, and strategic reserves of rare gases such as helium, the use of salt caverns to store small-molecule gases such as hydrogen and helium is gradually becoming an important development direction. Compared with conventional natural gas, small-molecule gases such as hydrogen and helium have characteristics such as small molecular size, strong diffusion ability, and high leakage sensitivity, which places higher demands on the sealing performance of the surrounding rock, the degree of interlayer development, the integrity of the roof and floor plates, and the long-term stability of the cavity in salt cavern storage facilities.

[0003] Existing suitability evaluation technologies for salt cavern storage are mostly aimed at conventional natural gas, and commonly use the analytic hierarchy process (AHP), fuzzy comprehensive evaluation, or expert scoring method to evaluate regional site selection based on factors such as burial depth, thickness, faults, and transportation conditions. However, the above methods have the following obvious shortcomings: (1) They lack evaluation indicators for leakage risk and long-term stability of small molecule gases; (2) The scores of many indicators rely on expert experience, are highly subjective, and lack support from objective engineering response parameters such as leakage rate, plastic zone, and volume shrinkage rate; (3) The evaluation scale is relatively coarse, mostly staying at the block level, and it is difficult to delve into the fine optimization of different cavity layers and different cavity locations within the same salt layer; (4) It is difficult to reflect the control effect of interlayers on the leakage of small molecule gases, while in reality, a large number of interlayers often develop inside the salt layer, and interlayers are usually important channels for potential leakage; (5) They lack a mechanism for quantitative mechanical comparison of different layers under a unified target cavity volume and operating system.

[0004] Therefore, there is an urgent need for an evaluation method that can target small molecule gases, be precise down to the stratigraphic level and cavity location, and integrate objective geomechanical response parameters, in order to improve the scientific rigor and engineering applicability of the selection of reservoir construction schemes for small molecule gases such as hydrogen and helium in salt caverns. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a method for optimizing the cavity site and location of salt cavern hydrogen and helium storage facilities based on hierarchical analysis and geomechanical response mapping. This method solves the problems of existing technologies, such as strong subjectivity, insufficient specificity, difficulty in reflecting leakage control characteristics of interlayers, and difficulty in precisely optimizing the cavity site and location within salt layers. The technical solution is as follows: The first aspect of this application provides a method for optimizing the cavity layout of a salt cavern small molecule gas reservoir, comprising the following steps: acquiring basic geological data of the target salt layer and screening the target salt layer according to preset reservoir construction constraints, retaining salt layer areas that meet the constraints; dividing the screened salt layer areas into multiple candidate cavity-building layers; establishing a hierarchical analysis evaluation index system for small molecule gas reservoirs and determining the weight of each evaluation index; for each candidate cavity-building layer, constructing a geomechanical model under a unified target cavity volume and operating pressure regime, and calculating geomechanical response parameters including at least leakage rate, volume shrinkage rate, plastic zone volume ratio, and safety factor; mapping the geological indicators in the basic geological data and the geomechanical response parameters into standardized evaluation scores through continuous functions; calculating the comprehensive suitability index of each candidate cavity-building layer according to the weights and standardized evaluation scores, and determining the preferred cavity-building layer; dividing multiple candidate cavity-layout units within the preferred cavity-building layer, repeating the above geomechanical calculation and evaluation steps for each candidate cavity-layout unit, and determining the optimal cavity-layout location. According to the above embodiments, by sequentially performing constraint screening, stratigraphic division, hierarchical analysis weighting, geomechanical model calculation of response parameters (leakage rate, volume shrinkage rate, plastic zone volume ratio, safety factor), continuous function mapping score, comprehensive suitability index evaluation, and re-optimization of cavity locations within the stratigraphic layers, the effect is to construct a multi-level, progressive quantitative decision-making system from regional screening to stratigraphic optimization and then to precise location positioning. Compared with existing evaluation methods that rely solely on experience or single factors, this method, for the first time, directly uses objective engineering response parameters (such as leakage rate, plastic zone, etc.) obtained from geomechanical numerical simulation as evaluation input, making the optimization results directly related to the long-term safety and sealing of small molecule gas storage facilities. This solves the problem that traditional methods cannot reflect interlayer leakage control and cannot distinguish subtle differences within salt layers, achieving a fair and objective comparison of different stratigraphic layers and cavity locations under a unified cavity volume and operating system.

[0006] For example, in one embodiment of the preferred method for constructing and arranging small molecule gas storage chambers in salt caverns, the preset construction constraints include at least one of the following: minimum effective salt layer thickness threshold, minimum safe distance from faults, requirements for the integrity of the top and bottom plates, salt layer continuity index, upper limit of tectonic activity, restrictions on groundwater or high-permeability channels, and minimum feasible chamber space threshold. According to the above embodiment, by limiting the constraints to at least salt layer thickness, fault distance, top and bottom plate integrity, salt layer continuity, tectonic activity, groundwater / high-permeability channels, and minimum feasible chamber space, the effect is to establish a strict engineering entry "threshold," quickly eliminating areas with significant safety hazards or those unable to meet basic construction requirements. For example, insufficient salt layer thickness cannot form effective gas storage space, excessively close fault distances may create leakage channels, and incomplete top and bottom plates can easily lead to gas upwelling or downwelling. These constraints take into account geological safety, sealing, and feasibility, ensuring that subsequent optimization work is only carried out within the effective area where a chamber can be constructed, thus improving evaluation efficiency and result reliability.

[0007] For example, in the optimal method for constructing and arranging small molecule gas reservoirs in salt caverns provided in one embodiment, the hierarchical analysis evaluation index system includes a target layer, a criterion layer, and an index layer. The criterion layer includes at least one of geological reservoir construction conditions, sealing safety conditions, cavity stability conditions, engineering implementation conditions, and locational economic conditions. The geomechanical response parameters also include at least one of roof settlement, creep convergence, and stress concentration coefficient. According to the above embodiment, by constructing a three-layer structure of target layer, criterion layer (geological reservoir construction conditions, sealing safety conditions, cavity stability conditions, engineering implementation conditions, and locational economic conditions), and index layer, the effect is that it realizes the systematic and organized organization of multi-dimensional factors affecting the suitability of small molecule gas reservoirs. The division of the criterion layer covers the entire chain from underground geological characteristics to above-ground economic location, avoiding the omission of key influencing factors; the hierarchical structure provides a clear logical framework for subsequently using the analytic hierarchy process (AHP) to determine the weights of each index, enabling subjective judgment and objective data to be organically combined, improving the scientificity and interpretability of the evaluation system. By further defining auxiliary parameters such as calculable roof settlement, creep convergence, and stress concentration factor, the effect is to provide richer quantitative indicators for evaluating the long-term stability of the cavity. Small molecule gas reservoirs are more sensitive to the creep and deformation of the surrounding rock; excessive roof settlement can lead to sealing failure, excessively rapid creep convergence can reduce the effective gas storage volume, and an excessively high stress concentration factor may cause local rupture. These indicators can be corroborated with basic parameters such as leakage rate and plastic zone, providing redundant judgment criteria when encountering data noise or model uncertainty, and enhancing the robustness of the optimization results.

[0008] For example, in the preferred cavity layout method for salt cavern small molecule gas reservoirs provided in one embodiment, for each candidate cavity layout unit U kEstablish a geomechanical model and calculate its leakage rate η. l,k Volume shrinkage rate η v,k η, volume ratio of the plastic zone p,k Safety factor F s,k The score S was obtained by standardizing the result using a mapping function. ik ;No. The overall suitability index of the candidate cavity units is: satisfy: Candidate cavity unit U k,* This is the optimal cavity placement position.

[0009] For example, in the optimal method for constructing and arranging small molecule gas storage chambers in a salt cavern provided in one embodiment, the continuous function includes at least one of a decreasing continuous function, an increasing continuous function, and a peak-type continuous function; wherein: the decreasing continuous function is used for leakage rate, volume shrinkage rate, and plastic zone volume ratio indicators; the increasing continuous function is used for safety factor, minimum effective thickness of the salt layer, and distance from the fault indicator; and the peak-type continuous function is used for burial depth indicator. According to the above embodiment, by using decreasing, increasing, and peak-type continuous functions respectively to handle the three types of indicators of "smaller is better," "larger is better," and "interval optimal," the effect is that it achieves standardized and dimensionless unified scoring of indicators with different dimensions and physical meanings. Leakage rate, volume shrinkage rate, etc., should be as small as possible; safety factor, effective thickness, etc., should be as large as possible; and burial depth, etc., has an optimal range. By constructing continuous functions (such as linear normalization and membership functions), the "step effect" caused by subjective segmentation can be avoided, so that subtle differences in indicators can still be reflected in the score. Moreover, the scoring process is entirely based on mathematical mapping, eliminating the bias of human experience and improving the objectivity and precision of the evaluation.

[0010] For example, in one embodiment of the method for optimizing the cavity layout of a salt cavern small molecule gas storage facility, a comprehensive risk characterization step for interlayers is included: constructing a comprehensive risk index for interlayers based on the total thickness of the interlayers, the number of interlayers, and the influence coefficient of interlayer distribution, and mapping it to a standardized evaluation score through a continuous function. According to the above embodiment, by constructing a comprehensive risk index for interlayers based on the total thickness of the interlayers, the number of interlayers, and the influence coefficient of distribution, and mapping it to a score, the effect is to quantitatively characterize the key control role of interlayers as potential leakage channels for small molecule gases. Hydrogen and helium molecules have small diameters and easily diffuse along the interlayer interface or penetrate the interlayer. This method integrates interlayer development characteristics (thickness, number of layers, distribution uniformity) into a single risk index and incorporates it into the evaluation system, allowing candidate layers to automatically decrease in score based on interlayer risk. This effectively avoids cavity construction in densely developed interlayer areas, significantly reducing leakage risk during long-term operation. This is a unique indicator lacking in existing conventional natural gas storage evaluation methods.

[0011] The second aspect of this application provides a system for optimizing the construction and layout of small molecule gas reservoirs in salt caverns, comprising: a data acquisition module for acquiring basic geological data of the target salt layer; a constraint screening module for screening the target salt layer according to preset construction constraints; a stratigraphic division module for dividing multiple candidate construction strata within the screened salt layer area; a hierarchical analysis module for establishing a hierarchical analysis evaluation index system and determining the weight of each evaluation index; a geomechanical calculation module for constructing a geomechanical model under a unified target cavity volume and operating pressure regime, and calculating the geomechanical response parameters of each candidate construction stratum; a mapping and scoring module for mapping geological indicators and geomechanical response parameters into standardized evaluation scores through continuous functions; a comprehensive evaluation module for calculating a comprehensive suitability index and determining the preferred construction strata; a cavity location optimization module for dividing candidate cavity units within the preferred construction strata and determining the optimal cavity location; and an output module for outputting the optimization results. According to the above embodiments, by integrating modules such as data acquisition, constraint screening, stratigraphic division, hierarchical analysis, geomechanical calculation, mapping scoring, comprehensive evaluation, optimal cavity location selection, and output, the effect is that the methodology is solidified into a programmable and automated computational system. The modules are connected through standardized data interfaces, enabling collaboration with geological modeling software, finite element numerical simulation software, and databases. This achieves fully automated processing from raw geological data input to optimal result output, significantly reducing manual labor intensity and improving the efficiency of comparing multiple candidate schemes. It is suitable for batch calculations and scheme optimization in actual salt cavern reservoir site selection projects.

[0012] For example, in the optimal cavity layout system for a salt cavern small molecule gas storage provided in one embodiment, the geomechanical calculation module is configured to calculate at least one response parameter among leakage rate, volume shrinkage rate, plastic zone volume ratio, and safety factor. According to the above embodiment, by limiting the geomechanical calculation module to calculate at least one of leakage rate, volume shrinkage rate, plastic zone volume ratio, and safety factor, the effect is to: clarify the output index type of the core calculation unit of the system, ensuring the objectivity and engineering relevance of the evaluation data. The leakage rate directly reflects the sealing performance, the volume shrinkage rate characterizes the long-term volume retention capacity, the plastic zone volume ratio indicates the extent of surrounding rock damage, and the safety factor comprehensively assesses structural stability. These indicators can all be obtained through finite element numerical simulation under unified boundary conditions, unaffected by subjective experience, making the system output results reproducible.

[0013] For example, in the cavity layout optimization system for salt cavern small molecule gas storage provided in one embodiment, the optimization results output by the output module include the comprehensive suitability index and ranking results of candidate cavity construction layers, the preferred cavity construction layer, the comprehensive suitability index and ranking results of candidate cavity layout units, the optimal cavity layout location, and the suitability level classification results. According to the above embodiment, by limiting the optimization results output by the output module to include the comprehensive suitability index and ranking of candidate layers, the preferred layer, the ranking of candidate cavity layout units, the optimal cavity layout location, and the suitability level classification, the effect is that it provides complete decision support information from coarse to fine, from general to specific. Operators can not only see the finally recommended optimal cavity layout location, but also understand the relative superiority and inferiority order and suitability level of each candidate layer (such as highly suitable, reasonably suitable, etc.), facilitating flexible selection or reserve of alternative solutions based on the actual situation of the project (such as cost, construction difficulty). At the same time, the ranking and level information can be directly used as an appendix to the design report, improving the transparency of decision-making.

[0014] 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-described method steps on a computer-readable storage medium, the effect is to extend the scope of protection of this application to the software product level. This program can be pre-installed in a professional geological engineering workstation or provided to authorized users via a network, allowing engineers to operate automatically and output optimized results simply by importing basic geological parameters, without needing a professional background in analytic hierarchy process (AHP) and geomechanical simulation. This lowers the technical application threshold and facilitates large-scale promotion in the industry.

[0015] The method and system for optimizing the cavitation sites and locations of small molecule gas reservoirs in salt caverns based on hierarchical analysis and geomechanical response mapping provided in some embodiments of this application, through steps such as constraint screening, hierarchical analysis weighting, geomechanical numerical simulation, and standardized scoring of continuous function mapping, have the following significant beneficial effects: (1) Targeted evaluation of small molecule gas storage facilities has been achieved. This application is specifically designed for small molecule gases such as hydrogen and helium, and introduces response parameters that directly reflect sealing performance and long-term stability, such as leakage rate, plastic zone volume, volume shrinkage rate, and safety factor. This overcomes the shortcomings of conventional natural gas storage facility evaluation methods that ignore the high diffusion and high leakage risk of small molecules, and makes the optimization results more in line with the actual operation requirements of small molecule gas storage facilities.

[0016] (2) The subjectivity in the evaluation process has been greatly reduced. This application uses objective values ​​such as leakage rate, volume shrinkage rate, plastic zone volume ratio, and safety factor calculated by the geomechanical model as the core input for evaluation, and standardizes them into scores through continuous function mapping. This avoids the arbitrariness and inconsistency caused by the heavy reliance on expert experience in traditional methods, and makes the evaluation results reproducible and verifiable.

[0017] (3) A three-level fine optimization from region to stratigraphy to cavity location was achieved. This application first conducts constraint screening, then divides candidate cavity-building strata for comprehensive evaluation; after determining the preferred strata, the strata are further divided into multiple cavity-building units, and the geomechanical calculation and scoring process is repeated to finally output the optimal cavity location. This three-level progressive structure can identify the differences in sealing and stability caused by interlayer development and physical property differences within the same salt layer, significantly improving the refinement level of reservoir construction scheme design.

[0018] (4) The interlayer plays a crucial role in controlling the leakage of small molecule gases. This application specifically constructs a comprehensive risk index for interlayers, incorporating the total thickness of the interlayer, the number of interlayers, and the distribution influence coefficient into the evaluation system. Since hydrogen and helium can easily penetrate or diffuse along the interlayer interface, this method can effectively screen out layers and locations with lighter interlayer development and lower leakage risk, thereby reducing the long-term operational leakage risk from the source and making up for the shortcomings of existing technologies that ignore the influence of interlayers.

[0019] (5) Provides a unified quantitative comparison basis. In the comparison of all candidate layers and cavity units, this application sets the same target cavity volume and operating pressure system to ensure the fairness of the evaluation; at the same time, through continuous function mapping, indicators with different dimensions and different physical meanings are transformed into comparable scores, realizing the full quantitative ranking of multiple candidate schemes, which makes it easier for decision-makers to directly obtain the optimal scheme and the order of candidates.

[0020] (6) The system has a high degree of integration and strong engineering operability. This application integrates the hierarchical analysis module, geomechanical calculation module, mapping scoring module, cavity location optimization module, etc. into one, which can be connected to geological modeling and numerical simulation software to realize automated processing from basic geological data input to optimization result output, significantly improving site selection efficiency. It is suitable for the design and approval of actual salt cavern hydrogen storage, helium storage and other small molecule gas storage facilities. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 Flowchart of the preferred method for constructing and arranging the cavity of the salt cavern small molecule gas storage in this application; Figure 2 This is a schematic diagram of the hierarchical analysis evaluation index system structure of this application; Figure 3 This is a schematic diagram of the candidate cavity construction layer division in this application. Detailed Implementation

[0023] 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. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] 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.

[0025] like Figure 1-3 As shown, this application presents a method for optimizing the strata and location of salt cavern hydrogen and helium storage reservoirs based on hierarchical analysis and geomechanical response mapping, relying on methods such as... Figure 3 The geological profile of the target block shown was implemented, and the annotations and feature descriptions of each element of the profile are as follows: Figure 3This paper presents a typical vertical geological profile of the target salt rock mining area. The uppermost layer is the top rock layer 1, and the lowermost layer is the bottom rock layer 7. Together, these two layers form the macroscopic closed boundary for reservoir construction, acting as the regional caprock and floor. The main middle section consists of a thick salt rock layer 3, interspersed with several interlayers 2 whose mechanical properties differ significantly from those of the salt rock. The core optimization work of this application is carried out within the salt rock layer 3. Three preliminary candidate reservoir construction layers, L14, L25, and L36, are marked in the figure. These three layers exhibit objective differences in salt layer thickness, top and bottom plate integrity, and interlayer development. This method aims to optimize the most suitable reservoir construction layers and specific cavity locations for long-term safe operation of hydrogen and helium storage through coupled calculations of hierarchical analysis and mechanical response mapping.

[0026] This application provides a method for optimizing the cavity construction and layout of a salt cavern small molecule gas storage facility, which specifically includes the following steps: Step S1: Acquisition of basic data and expression of parameters Obtain basic data on the target salt layer, including: salt layer burial depth H; minimum effective salt layer thickness T. e Salt rock purity P s Minimum distance D from the fault f Top and bottom plate integrity parameter R r Construct activity parameter A s Porosity distribution Permeability distribution k(x,y,z); Total thickness of interlayer I t Number of mezzanine layers I n ;Mezzanine distribution characterization parameter I d ; Target cavity volume V0; Operating pressure regime p(t).

[0027] Where (x,y,z) represents spatial coordinates, and p(t) represents the function of the pressure inside the cavity changing with time during the operating cycle.

[0028] Step S2: Database construction constraint screening For any candidate object within the target salt layer range, if the following constraints are met, it is retained; otherwise, it is discarded: Wherein: T min D is the minimum effective thickness threshold for the salt layer. min R is the minimum safe distance threshold from the fault; min Minimum requirements for the integrity of the top and bottom slabs; C s C is an indicator of salt layer continuity. min A is the threshold for salt layer continuity. max To construct the upper limit of activity; K h K represents the risk characterization value for underground water channels or high-permeability channels. maxIts maximum allowable limit; V a For the effective space for cavity creation; K min This is the minimum feasible cavity space threshold. The threshold can be preset or adaptively set according to the target gas storage capacity, operating pressure, and formation conditions.

[0029] Step S3: Candidate cavity construction layer division The salt layers that passed the constraint screening were divided into m candidate cavity-forming layers, denoted as: The parameter set corresponding to each candidate cavity-building layer Lj can be represented as: Different candidate cavity formation sites were compared under the same cavity volume V0 and operating pressure regime p(t).

[0030] Step S4: Establish an evaluation index system for hierarchical analysis. Construct a hierarchical model of target layer - criterion layer - indicator layer.

[0031] The target layer, G, represents the overall suitability of the cavity site and placement for small molecule gas reservoirs in salt caverns. The criterion layer can be represented as: Among them, B1: geological conditions for reservoir construction; B2: sealing and safety conditions; B3: cavity stability conditions; B4: engineering implementation conditions; B5: location and economic conditions.

[0032] The indicator layer can be represented as: Where n is the total number of evaluation indicators. Preferably, the indicators include at least the salt layer burial depth, minimum effective thickness of the salt layer, salt rock purity, interlayer thickness and distribution, porosity, permeability, distance from the fault, integrity of the top and bottom plates, leakage rate, volume shrinkage rate, volume of the plastic zone, and safety factor.

[0033] Step S5: Calculation of weights using the Analytic Hierarchy Process (AHP) (1) Construct the judgment matrix For pairwise importance comparisons of indicators within the same tier, a judgment matrix is ​​constructed: Among them, a ij To indicate the importance of index i relative to index j, satisfying: (2) Calculate the geometric mean The geometric mean of the i-th indicator is: (3) Weight normalization The weight of the i-th indicator is: This yields the weight vector: (4) Consistency check Calculate the approximate value of the largest eigenvalue of the judgment matrix: The consistency index is: The consistency ratio is: Wherein, RI is the random consistency index. When CR < 0.1, the judgment matrix is ​​considered to have satisfactory consistency; if not, the judgment matrix is ​​adjusted and recalculated.

[0034] In this application, the analytic hierarchy process (AHP) is used to determine the weights of each evaluation index, rather than for subjective scoring. The index scores are preferably obtained by function mapping from basic data and geomechanical response parameters.

[0035] Step S6: Calculation of Geomechanical Response of Candidate Cavity-Building Lattices For each candidate cavity construction layer L j Under the same cavity volume V0 and operating pressure regime p(t), a geomechanical model can be established, and its response parameters within the operating period T can be calculated using mature commercial software such as FLAC3D or Abaqus.

[0036] 1. Leakage rate Candidate cavity construction layer L j The cumulative leakage rate is defined as: Where: M l,j To evaluate the cumulative mass of leaked gas within the evaluation period; M 0,j This represents the total mass of the initially injected gas.

[0037] If we use the boundary mass flux integral form, then we have: Among them, Γ j M represents the potential leakage boundary outside the candidate layer. j (t) represents the gas mass flux per unit boundary area.

[0038] 2. Volume shrinkage rate Candidate cavity construction layer L jThe volume shrinkage rate at the end of the operating cycle is: Among them, V T,j To evaluate the cavity volume corresponding to this layer at the end of the cycle.

[0039] 3. Plastic zone volume ratio To facilitate comparison of different candidates, the volume ratio of the plastic zone is used: Among them, V p,j For candidate cavity construction layer L j The total volume of the plastic zone of the surrounding rock.

[0040] 4. Safety factor Candidate cavity construction layer L j The safety factor is expressed as: Among them, R j S represents the characterization value of the surrounding rock's resistance to instability. j This represents the load-bearing effect on the surrounding rock. The safety factor can be directly output from the geomechanical model or calculated based on the selected strength criterion.

[0041] 5. Optional auxiliary response parameters If necessary, the following auxiliary response parameters can be further calculated: Roof settlement: in, This represents the vertical displacement of the top plate.

[0042] Creep convergence amount: Where R0 is the initial equivalent cavity radius, R T,j To evaluate the equivalent cavity radius at the end of the cycle.

[0043] Stress concentration factor: Where, σ max,j For the local maximum equivalent stress, σ 0,j This refers to the original geostress or reference stress.

[0044] Step S7: Continuous Function Mapping and Score Calculation of Evaluation Indicators To eliminate the dimensional differences between different indicators, the original indicator values ​​are converted into standardized scores. Let x be the original value of the j-th candidate on the i-th indicator. ij The score is s ij .

[0045] (1) Smaller is better type of index For indicators such as leakage rate, volumetric shrinkage rate, plastic zone volume ratio, top plate settlement, creep convergence, and stress concentration factor, a decreasing continuous function is used: (2) The larger the better type of index For indicators such as safety factor, minimum effective thickness of salt layer, distance from fault, integrity of top and bottom plates, continuity of salt layer, and purity of salt rock, an increasing continuous function is adopted: (3) Interval-optimal index There exists an optimal range for burial depth, etc. The index uses a peak-type function: In the formula, and These are the lower and upper limits of the optimal interval, respectively. and These represent the lower and upper limits of the acceptable range, respectively.

[0046] (4) Comprehensive characterization of mezzanine risk Considering that interlayers are one of the important channels for the leakage of small molecule gases, a comprehensive risk index for interlayers can be constructed: in: These represent the total thickness of the interlayer, the number of interlayers, and the influence coefficient of the interlayer distribution, respectively. A higher interlayer risk value indicates a more unfavorable outcome; therefore, its score can be expressed as: Step S8: Comprehensive suitability calculation and optimal selection of cavity construction site Let m be the number of candidate cavity-forming layers and n be the number of evaluation indicators. Then the comprehensive suitability index of the j-th candidate cavity-forming layer is: The candidate cavity-building layers are ranked according to the magnitude of the comprehensive suitability index, satisfying the following conditions: Candidate cavity construction layer L j,* This is the preferred cavity construction layer.

[0047] Step S9: Divide candidate cavity units within the preferred layer The preferred cavity construction layer L j,* The corresponding region is divided into r candidate cavity units, denoted as: Each candidate cavity unit Uk The corresponding set of local parameters is: Each candidate cavity unit is compared under a unified target cavity volume V0 and a unified operating pressure regime p(t).

[0048] For each candidate cavity unit U k Establish a geomechanical model and calculate its leakage rate η. l,k Volume shrinkage rate η v,k η, volume ratio of the plastic zone p,k Safety factor F s,k In addition to other optional indicators, the score S is obtained by standardizing the results using the mapping function described in step S7. ik .

[0049] No. The overall suitability index of the candidate cavity units is: satisfy: Candidate cavity unit U k,* This is the optimal cavity placement position.

[0050] Step S10: Appropriate Level Classification According to the comprehensive suitability index G k Candidates are categorized into different levels. A four-level classification is preferred: highly suitable, reasonably suitable, moderately suitable, and unsuitable. An example configuration could be: Step S11: Output the optimal result The output should include at least: the comprehensive suitability index of candidate cavity construction sites. and its sorting results; optimal cavity construction layer L j,* Comprehensive suitability index of candidate cavity units and its sorting results; optimal cavity location U k,* Appropriate risk classification results; information on interlayer risk, leakage risk, and stability risk.

[0051] Through the above steps, within the salt layer range that meets the basic conditions for reservoir construction, the reservoir construction layer and reservoir location with lower leakage rate and better stability under the same target reservoir volume and operating regime can be selected.

[0052] In another embodiment of this application, different continuous function mapping methods can be used for different types of evaluation indicators.

[0053] For indicators where "smaller is better," such as leakage rate, volume shrinkage rate, and plastic zone volume ratio, a decreasing linear normalization function is used; for indicators where "larger is better," such as safety factor, minimum effective salt layer thickness, and distance from fault, an increasing linear normalization function is used; and for indicators that are "optimal in an interval," such as burial depth, a peak-type membership function is used. Through these methods, indicators from different sources and with different dimensions can be uniformly mapped to standardized scores for comprehensive evaluation.

[0054] 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 optimal cavity construction and layout of a salt cavern small molecule gas storage tank, characterized in that, Includes the following steps: Obtain basic geological data of the target salt layer, and screen the target salt layer according to the preset reservoir construction constraints, retaining the salt layer areas that meet the constraints; Multiple candidate cavity-building layers were delineated within the screened salt layer area; Establish a hierarchical analysis evaluation index system for small molecule gas storage and determine the weight of each evaluation index; For each candidate cavity-forming layer, a geomechanical model is constructed under a unified target cavity volume and operating pressure regime, and geomechanical response parameters including at least leakage rate, volume shrinkage rate, plastic zone volume ratio and safety factor are calculated. The geological indicators and geomechanical response parameters in the basic geological data are mapped into standardized evaluation scores through continuous functions. Based on the weights and standardized evaluation scores, the comprehensive suitability index of each candidate cavity-building layer is calculated, and the preferred cavity-building layer is determined. Within the preferred cavity-forming stratum, multiple candidate cavity-laying units are divided. The above-mentioned geomechanical calculation and evaluation steps are repeated for each candidate cavity-laying unit to determine the optimal cavity location.

2. The preferred method for constructing and arranging the cavity of a salt cavern small molecule gas storage tank according to claim 1, characterized in that, The preset constraints for reservoir construction include at least one of the following: minimum effective thickness threshold of salt layer, minimum safe distance from fault, integrity requirements of top and bottom plates, salt layer continuity index, upper limit of tectonic activity, limitation of groundwater or high-permeability channels, and minimum cavity space threshold.

3. The preferred method for constructing and arranging the cavity of a salt cavern small molecule gas storage tank according to claim 1, characterized in that, The hierarchical analysis and evaluation index system includes a target layer, a criterion layer, and an index layer; the criterion layer includes at least one of geological reservoir construction conditions, sealing safety conditions, cavity stability conditions, engineering implementation conditions, and locational economic conditions; the geomechanical response parameters also include at least one of roof settlement, creep convergence, and stress concentration factor.

4. The preferred method for constructing and arranging the cavity of a salt cavern small molecule gas storage tank according to claim 1, characterized in that, For each candidate cavity unit U k Establish a geomechanical model and calculate its leakage rate η. l,k Volume shrinkage rate η v,k η, volume ratio of the plastic zone p,k Safety factor F s,k The score S was obtained by standardizing the result using a mapping function. ik ; No. The overall suitability index of the candidate cavity units is: satisfy: Candidate cavity unit U k,* This is the optimal cavity placement position.

5. The preferred method for constructing and arranging the cavity of a salt cavern small molecule gas storage tank according to claim 1, characterized in that, The continuous function includes at least one of a decreasing continuous function, an increasing continuous function, and a peak continuous function; wherein: the decreasing continuous function is used for leakage rate, volume shrinkage rate, and plastic zone volume ratio indicators; the increasing continuous function is used for safety factor, minimum effective thickness of salt layer, and distance from fault indicators; and the peak continuous function is used for burial depth indicators.

6. The preferred method for constructing and arranging the cavity of a salt cavern small molecule gas storage tank according to claim 1, characterized in that, It also includes a comprehensive risk characterization step for interlayers: constructing a comprehensive risk index for interlayers based on the total thickness of the interlayer, the number of interlayers, and the influence coefficient of the interlayer distribution, and mapping it to a standardized evaluation score through a continuous function.

7. A system for optimizing the construction and layout of small molecule gas storage chambers in salt caverns, characterized in that, include: The data acquisition module is used to acquire basic geological data of the target salt layer; The constraint screening module is used to screen target salt layers according to preset database construction constraints. The layer division module is used to divide multiple candidate cavity-building layers within the screened salt layer area; The Hierarchical Analysis module is used to establish a hierarchical analysis evaluation index system and determine the weight of each evaluation index. The geomechanical calculation module is used to construct a geomechanical model under a unified target cavity volume and operating pressure regime, and to calculate the geomechanical response parameters of each candidate cavity-forming layer. The mapping and scoring module is used to map geological indicators and geomechanical response parameters into standardized evaluation scores through continuous functions; The comprehensive evaluation module is used to calculate the comprehensive suitability index and determine the optimal cavity construction layer. The cavity location optimization module is used to divide candidate cavity units within the preferred cavity construction layer and determine the optimal cavity location; The output module is used to output the optimal results.

8. The optimal system for constructing and arranging salt cavern small molecule gas storage chambers according to claim 7, characterized in that, The geomechanical calculation module is configured to calculate at least one of the following response parameters: leakage rate, volume shrinkage rate, plastic zone volume ratio, and safety factor.

9. The optimal system for constructing and arranging salt cavern small molecule gas storage chambers according to claim 7, characterized in that, The output module outputs the following optimal results: the comprehensive suitability index and ranking of candidate cavity construction sites, the preferred cavity construction site, the comprehensive suitability index and ranking of candidate cavity placement units, the optimal cavity placement location, and the suitability level classification results.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps of the method as described in any one of claims 1 to 6.

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