Method for evaluating sealing performance of caprock in underground compressed flue gas energy storage system

Abstract

A method for evaluating the sealing performance of caprock in an underground compressed flue gas energy storage system. The method comprises: acquiring basic properties corresponding to caprock in an underground compressed flue gas energy storage system and sub-properties; acquiring parameters corresponding to all the sub-properties; on the basis of the basic properties and all the sub-properties, constructing a sealing performance evaluation index system table of the caprock in the underground compressed flue gas energy storage system; on the basis of the sealing performance evaluation index system table of the caprock in the underground compressed flue gas energy storage system, constructing a corresponding determination matrix, so as to determine basic property weights and sub-property weights; on the basis of the parameters, determining scores corresponding to the sub-properties; on the basis of the basic property weights, the sub-property weights and the scores corresponding to the sub-properties, calculating a total score of the sealing capability of the caprock in the underground compressed flue gas energy storage system; and on the basis of the total score, determining a sealing performance level of the caprock in the underground compressed flue gas energy storage system, thereby making the evaluation of the sealing performance of the caprock more accurate.

Description

Evaluation method for cap layer sealing of underground compressed flue gas energy storage system

[0001] This application claims priority to Chinese Patent Application No. 2024111950730, filed on August 28, 2024, entitled “Method, System, Apparatus, Equipment and Storage Medium for Evaluating the Sealing Performance of a Saline Aquifer Compressed Flue Gas Energy Storage System”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of geological space utilization, and in particular to a method for evaluating the sealing performance of the caprock of an underground compressed flue gas energy storage system. Background Technology

[0003] Against the backdrop of the "dual carbon" strategic goals and the ongoing and in-depth fight against pollution, the treatment of polluting flue gas is of particular importance. Flue gas can be compressed and injected underground, simultaneously achieving geological treatment of CO2 and other air pollutants within the flue gas. Furthermore, highly enclosed underground compressed flue gas energy storage systems can be constructed, utilizing inert gases such as N2 for energy storage. This promotes synergistic effects in pollution reduction and carbon reduction, expands flue gas treatment pathways, and facilitates the resource utilization of underground resources.

[0004] Currently, Chinese patent application CN110764159A discloses a method for evaluating the effectiveness of caprocks, and Chinese patent application CN114047547A discloses a quantitative evaluation method for the sealing capacity of gypsum-salt rock caprocks. These two methods are combined to conduct breakthrough pressure tests on the caprock using a single component, CO2 or methane gas, and evaluate the sealing performance of the caprock in underground compressed flue gas energy storage systems based on parameters such as the tested breakthrough pressure, caprock lithology, caprock thickness, caprock-to-ground ratio, and formation water chemistry characteristics.

[0005] However, in the existing technology, the evaluation of the caprock sealing of underground compressed flue gas energy storage systems only considers the general characteristics of the caprock, single gas breakthrough, and mechanical indicators such as caprock damage caused by increased reservoir pressure due to external fluid injection, which results in a large error in the evaluation of caprock sealing. Summary of the Invention

[0006] This application provides a method for evaluating the sealing performance of the caprock in an underground compressed flue gas energy storage system. This method addresses the problem that existing caprock sealing performance evaluations only consider mechanical indicators such as the general characteristics of the caprock, single gas breakthrough, and caprock damage caused by increased reservoir pressure due to external fluid injection, resulting in large errors in caprock sealing performance evaluation. This method increases the accuracy of caprock sealing performance evaluation.

[0007] In a first aspect, this application provides a method for evaluating the sealing performance of the caprock of an underground compressed flue gas energy storage system, applied to computer equipment, including:

[0008] Obtain the basic attributes corresponding to the cap layer of the underground compressed flue gas energy storage system, and determine the sub-attributes corresponding to each basic attribute;

[0009] Get all parameters corresponding to all sub-attributes;

[0010] Based on the aforementioned basic attributes and all the aforementioned sub-attributes, construct the evaluation index system table for the cap layer sealing performance of the underground compressed flue gas energy storage system.

[0011] Construct a corresponding judgment matrix based on the evaluation index system table of the sealing performance of the cap layer of the underground compressed flue gas energy storage system, and determine the weights of each basic attribute and each sub-attribute based on the judgment matrix.

[0012] All sub-attributes are scored according to the parameters corresponding to all sub-attributes to determine the score corresponding to each sub-attribute.

[0013] The total score of the capping capacity of the underground compressed flue gas energy storage system is calculated based on the weights of each basic attribute, the weights of each sub-attribute, and the scores corresponding to each sub-attribute.

[0014] The sealing performance level of the cap layer of the underground compressed flue gas energy storage system is determined based on the total score.

[0015] Based on the above technical content, the following steps are taken: First, determine the sub-attributes and parameters corresponding to each basic attribute of the caprock of the underground compressed flue gas energy storage system. Then, construct an evaluation index system table for the caprock's sealing performance and a corresponding judgment matrix based on the basic attributes and all sub-attributes. Next, determine the weights of each basic attribute and sub-attribute based on the judgment matrix. Finally, assign scores to all sub-attributes based on their corresponding parameters to determine their respective scores. Finally, calculate the total score for the caprock's sealing capacity based on the weights of each basic attribute, the weights of each sub-attribute, and the scores of each sub-attribute to determine the caprock's sealing performance level. By constructing the evaluation index system table for the caprock's sealing performance of the underground compressed flue gas energy storage system, the evaluation indicators are clearly defined, making the caprock's sealing performance evaluation more accurate.

[0016] In one possible design, the basic attributes include basic physical properties, wettability parameters, mechanical parameters, flue gas breakthrough parameters, and formation water permeability parameters; all sub-attributes include caprock lithology, clay content, caprock thickness, porosity, absolute helium permeability, average pore size, most probable pore size, median pore size, formation water-flue gas-rock contact angle, formation water-flue gas interfacial tension, shear strength, tensile strength, flue gas breakthrough pressure, flue gas cutoff pressure, formation water initiation pressure, and formation water permeability; correspondingly, determining each sub-attribute corresponding to each basic attribute includes: determining the... The basic physical properties are defined as follows: the caprock lithology, clay content, caprock thickness, porosity, absolute helium permeability, average pore size, most probable pore size, and median pore size. The wettability parameters are defined as follows: the formation water-flue gas-rock contact angle and the formation water-flue gas interfacial tension. The mechanical parameters are defined as follows: the shear strength and tensile strength. The flue gas breakthrough parameters are defined as follows: the flue gas breakthrough pressure and the flue gas cutoff pressure. The formation water permeability parameters are defined as follows: the formation water initiation pressure and the formation water permeability.

[0017] Furthermore, by providing a breakthrough pressure test method using a mixture of helium and flue gas, the problem of traditional underground gas storage facilities and CO2 geological sealing cap layer sealing performance evaluations only targeting a single gas was solved.

[0018] In one possible design, obtaining the parameters corresponding to all the sub-attributes includes: obtaining rock samples corresponding to the caprock of the underground compressed flue gas energy storage system, and determining the caprock lithology, clay content, caprock thickness, porosity, average pore size, most probable pore size, and median pore size based on the rock samples; decomposing the rock samples into a first rock sample, a second rock sample, a third rock sample, and a fourth rock sample; processing the first rock sample to obtain a processed first rock sample, and determining the formation water-flue gas-rock contact angle and formation water-flue gas interfacial tension corresponding to the caprock based on the processed first rock sample; processing the second rock sample to obtain a processed second rock sample, and determining the shear strength and tensile strength corresponding to the caprock based on the processed second rock sample; processing the third rock sample to obtain... The processed third rock sample was used to determine its steady-state flow rate under different helium injection pressures, as well as its inlet and outlet pressures at both ends. Helium permeability at different pressures was calculated based on the inlet pressure, outlet pressure, and steady-state flow rate. The helium permeability and average pore pressure at different pressures were linearly fitted to obtain the absolute helium permeability of the caprock. The fourth rock sample was then processed to obtain a processed fourth rock sample. The flue gas breakthrough pressure and cutoff pressure corresponding to the caprock were determined based on the processed fourth rock sample. The formation water flow rate and initiation pressure gradient corresponding to the caprock were determined based on the processed fourth rock sample. Formation water permeability was calculated based on the inlet pressure, outlet pressure, and formation water flow rate. The formation water initiation pressure was calculated based on the caprock thickness and the initiation pressure gradient.

[0019] Furthermore, by equally decomposing the rock sample into a first rock sample, a second rock sample, a third rock sample, and a fourth rock sample for different calculations, the subsequent evaluation of the caprock sealing of the underground compressed flue gas energy storage system becomes more accurate and comprehensive.

[0020] In one possible design, the formula for calculating the helium permeability at different pressures based on the inlet pressure, the outlet pressure, and the steady-state flow rate is as follows:

[0021] In the formula, k g Q represents the helium permeability. g The steady-state flow rate; p1 and p2 are the inlet and outlet pressures at both ends of the processed third rock sample, respectively; μ g Z is the gas dynamic viscosity under experimental conditions; Z is the gas compressibility factor under experimental conditions; Z a For the experimental temperature and p aGas compressibility factor under the given conditions; L and A are the length and cross-sectional area of ​​the processed third rock sample, respectively;

[0022] Accordingly, the formula for calculating the absolute helium permeability of the caprock after linearly fitting the helium permeability and average pore pressure under different pressures is as follows:

[0023] In the formula: k ∞ k represents the absolute permeability of the helium gas. g b is the helium permeability; b is the slip coefficient; The average pore pressure is denoted as .

[0024] Furthermore, by calculating the absolute helium permeability of the caprock, the accuracy of the caprock sealing evaluation for subsequent underground compressed flue gas energy storage systems was improved.

[0025] In one possible design, the formula for calculating formation water permeability based on the inlet pressure, the outlet pressure, and the formation water flow rate is as follows:

[0026] In the formula: k w Q represents the formation water permeability. w The formation water flow rate is given; P1 and P2 are the inlet and outlet pressures of the processed fourth rock sample, respectively; L is the length of the processed fourth rock sample; A is the cross-sectional area of ​​the processed fourth rock sample; μ is the viscosity.

[0027] Accordingly, the formula for calculating the formation water initiation pressure based on the caprock thickness and the initiation pressure gradient is: P q =TPG×h

[0028] In the formula, P q is the formation water initiation pressure; TPG is the initiation pressure gradient; and h is the caprock thickness.

[0029] Furthermore, by calculating the initiation pressure of formation water, the accuracy of the caprock sealing evaluation for subsequent underground compressed flue gas energy storage systems was improved.

[0030] In one possible design, constructing the caprock sealing evaluation index system table for the underground compressed flue gas energy storage system based on the basic attributes and all sub-attributes includes: determining the basic attributes as the criterion layer and all sub-attributes as the index layer; constructing the caprock sealing evaluation index system table for the underground compressed flue gas energy storage system based on the preset target layer, the criterion layer, and the index layer; correspondingly, constructing a corresponding judgment matrix based on the caprock sealing evaluation index system table for the underground compressed flue gas energy storage system, and determining the weights of each basic attribute and each sub-attribute based on the judgment matrix includes: constructing a first judgment matrix based on the criterion layer in the caprock sealing evaluation index system table for the underground compressed flue gas energy storage system; constructing a second judgment matrix based on the index layer and according to the division of each basic attribute; and determining the weights of each basic attribute and each sub-attribute based on the first judgment matrix and the second judgment matrix.

[0031] Furthermore, by constructing an evaluation index system table for the cap layer sealing of underground compressed air energy storage systems and applying the analytic hierarchy process (AHP), a quantitative evaluation of the cap layer sealing of underground compressed air energy storage systems was achieved. This evaluation is highly operable and scientific, laying the foundation for subsequent design of underground compressed air energy storage systems, optimization of flue gas injection parameters, and ensuring stable system operation.

[0032] Secondly, this application provides a capping sealing evaluation system for an underground compressed flue gas energy storage system, applied to computer equipment, comprising:

[0033] The first determining module is used to obtain the basic attributes corresponding to the cap layer of the underground compressed flue gas energy storage system, and to determine the sub-attributes corresponding to each basic attribute.

[0034] The retrieval module is used to retrieve the parameters corresponding to all sub-attributes;

[0035] The construction module is used to construct the evaluation index system table for the cap layer sealing of the underground compressed flue gas energy storage system based on the basic attributes and all the sub-attributes.

[0036] The second determining module is used to construct a corresponding judgment matrix based on the evaluation index system table of the sealing performance of the underground compressed flue gas energy storage system cap layer, and to determine the weight of each basic attribute and the weight of each sub-attribute based on the judgment matrix.

[0037] The processing module is used to assign scores to all sub-attributes based on the parameters corresponding to all sub-attributes, so as to determine the score corresponding to each sub-attribute;

[0038] The calculation module is used to calculate the total score of the capping capacity of the underground compressed flue gas energy storage system based on the weights of each basic attribute, the weights of each sub-attribute, and the scores corresponding to each sub-attribute.

[0039] The third determining module is used to determine the sealing performance level of the cap layer of the underground compressed flue gas energy storage system based on the total score.

[0040] Thirdly, this application provides a device for evaluating the sealing performance of the caprock of an underground compressed flue gas energy storage system, comprising: a simulated flue gas cylinder, a helium cylinder, a gas booster pump, a gas storage tank, a gas storage tank pressure gauge, a water tank, a constant speed and constant pressure pump, a water storage tank, a vacuum pump, an inlet pressure gauge, a core holder, an outlet pressure gauge, a ring pressure tracking pump, a ring pressure gauge, a gas flow meter, a breakthrough pressure bubble detector, a capillary flow meter, and a constant temperature chamber;

[0041] The simulated flue gas cylinder and the helium cylinder are connected to the gas booster pump via pipelines.

[0042] The gas booster pump is connected to the gas storage tank via a pipeline.

[0043] The water tank is connected to the constant speed and constant pressure pump via a pipeline.

[0044] The constant speed and constant pressure pump is connected to the water storage tank by a pipeline.

[0045] The gas storage tank, the water storage tank, and the vacuum pump are connected by pipelines to the core holder.

[0046] The pressure gauge for the gas storage tank is installed on the gas storage tank and is used to measure the pressure of the gas storage tank.

[0047] The annular pressure tracking pump is connected to the core holder via a pipeline.

[0048] The annular pressure gauge is installed on the pipeline between the annular pressure tracking pump and the core holder, and is used to measure the annular pressure.

[0049] The inlet pressure gauge is installed at the inlet of the core holder and is used to measure the inlet pressure;

[0050] The core holder is connected by a pipeline to the gas flow meter, the breakthrough pressure bubble detector, and the capillary flow meter.

[0051] The outlet pressure gauge is installed at the outlet of the core holder and is used to measure the outlet pressure.

[0052] The constant temperature chamber is used to maintain the temperature of the gas storage tank, the water storage tank, the core holder, the gas flow meter, the breakthrough pressure bubble detector, and the capillary flow meter to a constant state.

[0053] Fourthly, this application provides a computer device, comprising: at least one processor and a memory;

[0054] The memory stores computer-executed instructions;

[0055] The at least one processor executes computer execution instructions stored in the memory, causing the at least one processor to perform the method for evaluating the capping closure of the underground compressed flue gas energy storage system as described in the first aspect and various possible designs of the first aspect.

[0056] Fifthly, this application provides a computer storage medium storing computer execution instructions. When a processor executes the computer execution instructions, it implements the method for evaluating the sealing performance of the cap layer of an underground compressed flue gas energy storage system as described in the first aspect and various possible designs of the first aspect.

[0057] Sixthly, this application provides a computer program product, including a computer program that, when executed by a processor, implements the method for evaluating the caprock sealing of an underground compressed flue gas energy storage system as described in the first aspect above.

[0058] The method for evaluating the sealing performance of the caprock of an underground compressed flue gas energy storage system provided in this application involves: acquiring the basic attributes corresponding to the caprock of the underground compressed flue gas energy storage system and determining the sub-attributes and parameters corresponding to each basic attribute; constructing an evaluation index system table for the sealing performance of the caprock of the underground compressed flue gas energy storage system based on the basic attributes and all sub-attributes, and constructing a corresponding judgment matrix; determining the weights of each basic attribute and each sub-attribute based on the judgment matrix; assigning scores to all sub-attributes based on the parameters corresponding to all sub-attributes to determine the score corresponding to each sub-attribute; and calculating the total score of the caprock's sealing capacity based on the weights of each basic attribute, the weights of each sub-attribute, and the scores corresponding to each sub-attribute to determine the sealing performance level of the caprock. By constructing an evaluation index system table for the sealing performance of the caprock of the underground compressed flue gas energy storage system, the evaluation indicators are clearly defined, making the sealing performance evaluation of the caprock more accurate. Attached Figure Description

[0059] Figure 1 is a schematic flowchart of the method for evaluating the sealing performance of the cap layer of an underground compressed flue gas energy storage system provided in an embodiment of this application.

[0060] Figure 2 is a schematic diagram of the method for evaluating the sealing performance of the cap layer of an underground compressed flue gas energy storage system provided in an embodiment of this application.

[0061] Figure 3 is a schematic diagram of the structure of the underground compressed flue gas energy storage system cap layer sealing evaluation system provided in the embodiment of this application;

[0062] Figure 4 is a schematic diagram of the structure of the underground compressed flue gas energy storage system sealing evaluation device provided in the embodiment of this application;

[0063] Figure 5 is a schematic diagram of the hardware structure of the computer device provided in the embodiment of this application. Detailed Implementation

[0064] 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, 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.

[0065] Combustion flue gas typically consists of N2, O2, CO2, sulfides, nitrogen oxides, VOCs, and trace amounts of heavy metals, contributing to both the greenhouse effect and environmental pollution. Under the strategic goals of "dual carbon" (carbon reduction and emission reduction) and the ongoing battle against pollution, flue gas treatment is particularly important. Flue gas can be compressed and injected underground, simultaneously achieving geological disposal of CO2 and other air pollutants. Furthermore, highly enclosed underground compressed flue gas energy storage systems can be constructed, utilizing inert gases such as N2 for energy storage. This promotes synergistic effects in pollution and carbon reduction, expands flue gas treatment pathways, and facilitates underground resource utilization. Chinese patent application CN110764159A discloses a method for evaluating the effectiveness of caprocks, and Chinese patent application CN114047547A discloses a quantitative evaluation method for the sealing capacity of gypsum-salt rock caprocks. These two methods combine the methods of conducting breakthrough pressure tests on the caprock using a single component of CO2 or methane gas, and evaluating the sealing performance of the caprock in underground compressed flue gas energy storage systems based on parameters such as the tested breakthrough pressure, caprock lithology, caprock thickness, caprock-to-land ratio, and formation water chemistry characteristics. However, in existing technologies, the evaluation of the sealing performance of the caprock in underground compressed flue gas energy storage systems only considers the general characteristics of the caprock, the breakthrough pressure of a single gas, and mechanical indicators such as caprock damage caused by increased reservoir pressure due to the injection of external fluids, resulting in a large error in the evaluation of caprock sealing performance.

[0066] To address the aforementioned technical problems, this application proposes the following technical concept: Considering the basic attributes and all sub-attributes corresponding to the caprock of an underground compressed flue gas energy storage system, the inventors construct a caprock sealing performance evaluation index system table based on these attributes. The weights of each basic attribute and sub-attribute are calculated using this index system. After determining the scores for all sub-attributes, the total score for the caprock's sealing capacity is calculated based on the weights of each basic attribute, sub-attribute, and their corresponding scores. The corresponding sealing performance level is then determined based on the total score. By constructing this caprock sealing performance evaluation index system table, the evaluation indicators are clearly defined, making the caprock sealing performance evaluation more accurate. Detailed embodiments are described below.

[0067] Figure 1 is a schematic flowchart of the caprock sealing evaluation method for an underground compressed flue gas energy storage system provided in this embodiment. The executing entity in this embodiment can be a computer device; however, no special limitations are imposed here. As shown in Figure 1, the method includes:

[0068] S101: Obtain the basic attributes corresponding to the cap layer of the underground compressed flue gas energy storage system, and determine the sub-attributes corresponding to each basic attribute.

[0069] In this embodiment, each basic attribute includes basic physical property parameters, wettability parameters, mechanical parameters, flue gas breakthrough parameters, and formation water permeability parameters; all sub-attributes include caprock lithology, clay content, caprock thickness, porosity, absolute helium permeability, average pore size, most probable pore size, median pore size, formation water-flue gas-rock contact angle, formation water-flue gas interfacial tension, shear strength, tensile strength, flue gas breakthrough pressure, flue gas cutoff pressure, formation water initiation pressure, and formation water permeability; correspondingly, step S101, "determining each sub-attribute corresponding to each basic attribute," specifically involves:

[0070] Determine the basic physical properties corresponding to the caprock lithology, clay content, caprock thickness, porosity, absolute helium permeability, average pore size, most probable pore size, and median pore size; determine the wettability parameters corresponding to the formation water-flue gas-rock contact angle and formation water-flue gas interfacial tension; determine the mechanical parameters corresponding to the shear strength and tensile strength; determine the flue gas breakthrough parameters corresponding to the flue gas breakthrough pressure and flue gas cutoff pressure; determine the formation water initiation pressure and formation water permeability parameters corresponding to the formation water permeability parameters.

[0071] S102: Get all parameters corresponding to all sub-attributes.

[0072] In this embodiment, the parameters corresponding to all sub-attributes can be obtained by conducting on-site measurements of the capping layer, or by conducting sampling experiments on the capping layer.

[0073] For example, by conducting sampling experiments on the capping layer, the parameters corresponding to all sub-attributes are obtained as follows:

[0074] Table 1 shows the parameters corresponding to all sub-attributes.

[0075] S103: Construct an evaluation index system table for the sealing performance of the cap layer of an underground compressed flue gas energy storage system based on each basic attribute and all sub-attributes.

[0076] Specifically, step S103 includes:

[0077] S1031: Define each basic attribute as the criterion layer and all sub-attributes as the indicator layer.

[0078] For example, basic physical properties, wettability parameters, mechanical parameters, flue gas breakthrough parameters, and formation water permeability parameters are determined as criterion layers; caprock lithology, clay content, caprock thickness, porosity, absolute helium permeability, average pore size, most probable pore size, median pore size, formation water-flue gas-rock contact angle, formation water-flue gas interfacial tension, shear strength, tensile strength, flue gas breakthrough pressure, flue gas cutoff pressure, formation water initiation pressure, and formation water permeability are determined as indicator layers.

[0079] S1032: Construct an evaluation index system table for the capping closure of underground compressed flue gas energy storage system based on the preset target layer, criterion layer, and index layer.

[0080] In this embodiment, the preset target layer is the evaluation index of the sealing performance of the cap layer of the underground compressed flue gas energy storage system.

[0081] For example, the evaluation index system table for the cap layer sealing of an underground compressed flue gas energy storage system is constructed based on the preset target layer, criterion layer, and index layer as follows:

[0082] Table 2 Evaluation Index System for the Sealing Performance of the Cap Layer of Underground Compressed Flue Gas Energy Storage System

[0083] S104: Construct the corresponding judgment matrix based on the evaluation index system table of the sealing performance of the cap layer of the underground compressed flue gas energy storage system, and determine the weight of each basic attribute and the weight of each sub-attribute based on the judgment matrix.

[0084] Specifically, step S104 includes:

[0085] S1041: Construct the first judgment matrix based on the criteria layer in the evaluation index system table for the sealing performance of the cap layer of the underground compressed flue gas energy storage system.

[0086] Specifically, the hierarchical structure model in the evaluation index system table of the cover layer sealing of the underground compressed flue gas energy storage system is analyzed using the analytic hierarchy process (AHP), and the first judgment matrix is ​​constructed based on the criteria layer.

[0087] For example, the first judgment matrix is:

[0088] In the formula, A is a 5th order judgment matrix.

[0089] S1042: Construct a second judgment matrix based on the indicator layer and according to the division of each basic attribute.

[0090] Specifically, a second judgment matrix is ​​constructed based on the indicator layer and according to the division of five basic attributes.

[0091] The second judgment matrix consists of five corresponding sub-judgment matrices.

[0092] For example, the sub-judgment matrix corresponding to the basic physical property parameters in the index layer is as follows:

[0093] In the formula, B is an 8th-order judgment matrix.

[0094] S1043: Determine the weights of each basic attribute and each sub-attribute based on the first judgment matrix and the second judgment matrix.

[0095] Specifically, the corresponding parameters are compared pairwise based on the first judgment matrix and the second judgment matrix to determine the weights of each basic attribute and each sub-attribute.

[0096] For example, the correspondence table for the weights of each basic attribute and the weights of each sub-attribute, determined based on the first judgment matrix and the second judgment matrix, is as follows:

[0097] Table 3. Correspondence between the weights of each basic attribute and the weights of each sub-attribute.

[0098] In addition, the weights of the target layer (Wij,i=1,2,3,4,5;j=1,2,3,…,8) can be obtained by multiplying the weights of the criterion layer and the weights of the indicator layer.

[0099] S105: Assign scores to all sub-attributes based on the parameters corresponding to each sub-attribute to determine the score for each sub-attribute.

[0100] Specifically, step S105 includes steps a to b:

[0101] Step a: Obtain historical data on assigning scores to all sub-attributes.

[0102] Historical data can include engineering experience data from underground gas storage facilities, CO2 geological sequestration, and compressed air energy storage, or other data.

[0103] Step b: Based on the parameters corresponding to all sub-attributes and according to historical data, assign scores to all sub-attributes to determine the score corresponding to each sub-attribute.

[0104] The scoring intervals are (0, 2], (2, 4], (4, 6], (6, 8] and (8, 10], which are five intervals.

[0105] For example, the scores corresponding to each sub-attribute are:

[0106] Table 4: Score Table for Each Sub-Attribute

[0107] In addition, the scoring process can be further refined by assigning and quantifying the parameters corresponding to all sub-attributes to obtain quantified score values ​​(Pij, i = 1, 2, 3, 4, 5; j = 1, 2, 3, ..., 8).

[0108] S106: Calculate the total score of the sealing capacity of the cap layer of the underground compressed flue gas energy storage system based on the weights of each basic attribute, the weights of each sub-attribute, and the scores corresponding to each sub-attribute.

[0109] Specifically, step S106 includes steps c to d:

[0110] Step c: Calculate the evaluation value of the corresponding basic attribute based on the weight of each sub-attribute and the score of each sub-attribute.

[0111] The evaluation value of the corresponding basic attribute is calculated based on the weight of each sub-attribute and the score corresponding to each sub-attribute. The calculation formula is: p=∑W i ×P i

[0112] In the formula, p is the evaluation value of the corresponding basic attribute; W i P represents the weights corresponding to each sub-attribute i; i The score is the score corresponding to each sub-attribute i.

[0113] Furthermore, if the total score of the target layer is calculated by multiplying the weights of the criterion layer and the weights of the indicator layer, then it is: P = ∑W ij ×P ij

[0114] In the formula, P is the total score of the target layer; Wij is the weight of the target layer; and Pij is the quantitative score.

[0115] Step d: Calculate the total score of the capping capacity of the underground compressed flue gas energy storage system based on the evaluation values ​​and weights of each basic attribute.

[0116] For example, the product of the evaluation values ​​of each basic attribute and the weights of each basic attribute is summed to obtain a total score of 8.12 for the sealing capacity of the cap layer of the underground compressed flue gas energy storage system.

[0117] S107: Determine the sealing performance level of the cap layer of the underground compressed flue gas energy storage system based on the total score.

[0118] In this embodiment, the sealing performance level is divided as follows: if the total score is [10, 8), it indicates that the capping layer has strong sealing performance; if the total score is [8, 6), it indicates that the capping layer has average sealing performance; if the total score is [6, 0], it indicates that the capping layer has poor sealing performance.

[0119] For example, if P = 8.12 ∈ [10, 8), it indicates that the cap layer has strong sealing properties, good quality, and high safety of the energy storage system.

[0120] In summary, the method for evaluating the sealing performance of the caprock of an underground compressed flue gas energy storage system provided in this embodiment obtains the basic attributes corresponding to the caprock of the underground compressed flue gas energy storage system and determines the sub-attributes and parameters corresponding to each basic attribute; constructs an evaluation index system table for the sealing performance of the caprock of the underground compressed flue gas energy storage system based on each basic attribute and all sub-attributes, and constructs a corresponding judgment matrix, and determines the weights of each basic attribute and each sub-attribute based on the judgment matrix; assigns scores to all sub-attributes based on the parameters corresponding to all sub-attributes to determine the score corresponding to each sub-attribute; calculates the total score of the caprock's sealing capacity based on the weights of each basic attribute, the weights of each sub-attribute, and the scores corresponding to each sub-attribute, to determine the sealing performance level of the caprock. By constructing an evaluation index system table for the sealing performance of the caprock of the underground compressed flue gas energy storage system, the evaluation indicators are clearly defined, making the sealing performance evaluation of the caprock more accurate.

[0121] Furthermore, this embodiment achieves a quantitative evaluation of the cap layer sealing performance of the underground compressed air energy storage system by constructing an evaluation index system table for the cap layer sealing performance and applying the analytic hierarchy process. This approach is highly operable and scientific, laying the foundation for subsequent design of the underground compressed air energy storage system, optimization of flue gas injection parameters, and ensuring stable system operation.

[0122] Furthermore, this embodiment provides a method for testing the breakthrough pressure of mixed gases, which solves the problem that traditional evaluations of the sealing of underground gas storage facilities and CO2 geological sealing caps only target a single gas.

[0123] Figure 2 is a schematic flowchart of the caprock sealing evaluation method for an underground compressed flue gas energy storage system provided in this application embodiment. In this application embodiment, based on the embodiment provided in Figure 1, the specific implementation method for obtaining the parameters corresponding to all sub-attributes in step S102 is described in detail. As shown in Figure 2, the method includes:

[0124] S201: Obtain rock samples corresponding to the caprock of the underground compressed flue gas energy storage system, and determine the caprock lithology, clay content, caprock thickness, porosity, average pore size, most probable pore size, and median pore size based on the rock samples.

[0125] Specifically, rock samples corresponding to the caprock of the underground compressed flue gas energy storage system were obtained, and based on drilling and seismic technologies and analytical methods such as XRD and XRF, the lithology, clay content, caprock thickness, porosity, average pore size, most probable pore size, and median pore size of the rock samples were obtained.

[0126] S202: The rock sample is decomposed into four rock samples: the first rock sample, the second rock sample, the third rock sample, and the fourth rock sample.

[0127] S203: The first rock sample is processed to obtain the processed first rock sample, and the contact angle of formation water-flue gas-rock and the interfacial tension of formation water-flue gas corresponding to the caprock are determined based on the processed first rock sample.

[0128] In this embodiment, the first rock sample after processing is a thin cylindrical sample with parallel and smooth end faces.

[0129] Specifically, a contact angle analyzer was used to determine the contact angle between formation water, flue gas, and rock, as well as the interfacial tension between formation water and flue gas, of thin cylindrical samples in a formation water-simulated flue gas environment.

[0130] In addition, based on the experimental conditions, the contact angle of rocks under ambient temperature and pressure and formation temperature and pressure can also be tested.

[0131] S204: The second rock sample is processed to obtain a processed second rock sample, and the shear strength and tensile strength of the caprock are determined based on the processed second rock sample.

[0132] In this embodiment, the processed second rock sample is a cylindrical sample of two sizes: 50 mm in diameter and 50 mm in length, and 50 mm in diameter and approximately 35 mm in length. The number of samples of the same size is no less than 5.

[0133] Specifically, the shear strength and tensile strength of cylindrical samples of two different sizes were obtained using instruments or methods such as rock mechanics testing machines and the Brazilian splitting method, in order to determine the shear strength and tensile strength of the corresponding cap layer.

[0134] In addition, for rock samples with an error of less than 10%, the average value is taken as the shear strength and tensile strength of the caprock.

[0135] S205: The third rock sample is processed to obtain the processed third rock sample. The steady-state flow rate of the processed third rock sample under different helium injection pressures, as well as the inlet and outlet pressures at both ends, are measured. The helium permeability under different pressures is calculated based on the inlet pressure, outlet pressure, and steady-state flow rate. The absolute helium permeability of the caprock is obtained by linear fitting of the helium permeability and average pore pressure under different pressures.

[0136] In this embodiment, the processed third rock sample is a cylindrical sample with a diameter of 25 mm and a length between 20 and 30 mm.

[0137] In this embodiment, the different helium injection pressures can be any number of helium injection pressures, such as 3, 6 or 8, or they can be a range of helium injection pressures.

[0138] For example, after drying at 105°C, the steady-state flow rate at 6 to 8 different helium injection pressures was determined using the steady-state method based on the gas flow meter in the underground compressed flue gas energy storage system cap cover sealing evaluation device in Figure 4.

[0139] The inlet and outlet pressures at both ends are obtained from the inlet and outlet pressure gauges in the underground compressed flue gas energy storage system capping sealing evaluation device.

[0140] In this embodiment, the helium permeability at different pressures is calculated based on the inlet pressure, outlet pressure, and steady-state flow rate. The calculation formula is as follows:

[0141] In the formula, k g Q represents helium permeability. g The steady-state flow rate; p1 and p2 are the inlet and outlet pressures at both ends of the processed third rock sample, respectively; μ g Z is the gas dynamic viscosity under experimental conditions; Z is the gas compressibility factor under experimental conditions; Z a For the experimental temperature and p a The gas compressibility factor under the given conditions; L and A are the length and cross-sectional area of ​​the processed third rock sample, respectively.

[0142] Accordingly, after linearly fitting the helium permeability and average pore pressure under different pressures, the formula for calculating the absolute helium permeability of the caprock is as follows:

[0143] In the formula: k ∞ k is the absolute permeability of helium. g b is the helium permeability; b is the slip coefficient. The average pore pressure is denoted as .

[0144] S206: The fourth rock sample is processed to obtain the processed fourth rock sample, and the flue gas breakthrough pressure and cut-off pressure corresponding to the caprock are determined based on the processed fourth rock sample.

[0145] In this embodiment, the processed fourth rock sample is a cylindrical sample with a diameter of 25 mm and a length of 10 mm.

[0146] In this embodiment, after the simulated formation water is saturated, the breakthrough pressure of the simulated flue gas is measured by using the breakthrough pressure bubble detector in the caprock sealing evaluation device of the underground compressed flue gas energy storage system in Figure 4, and by gradually increasing the pressure from low pressure to high pressure using a stepwise method.

[0147] The simulated flue gas was prepared based on the main components of real flue gas (content >1%), and the simulated formation water was prepared based on the main anions and cations of real formation water.

[0148] Specifically, after the flue gas breaks through the cylindrical sample under high pressure, the pressurization is stopped, and the flue gas flows under the residual gas pressure. When no gas flows out of the outlet, the inlet gas pressure at the inlet pressure gauge is the cut-off pressure.

[0149] S207: Determine the formation water flow rate and initiation pressure gradient corresponding to the caprock based on the processed fourth rock sample, and calculate the formation water permeability based on the inlet pressure, outlet pressure and formation water flow rate; calculate the formation water initiation pressure based on the caprock thickness and initiation pressure gradient.

[0150] Specifically, a cylindrical sample with a diameter of 25 mm and a length of 10 mm was used and then saturated with simulated formation water. Using the capillary flow meter, inlet pressure gauge, and outlet pressure gauge in the underground compressed flue gas energy storage system caprock sealing evaluation device shown in Figure 4, the inlet pressure, outlet pressure, and formation water flow rate of the core holder were measured. The formation water permeability and starting pressure gradient of the caprock were obtained by using the method of "high-pressure displacement + step-by-step pressure reduction + non-steady-state pressure reduction". Combined with the caprock thickness, the formation water starting pressure of the caprock was finally obtained.

[0151] High-pressure displacement is used to remove residual air from the core, stepwise depressurization is used to determine the flow rate and calculate the permeability under different injection pressures, and unsteady-state depressurization is used to determine the starting pressure gradient of the caprock corresponding to the cylindrical sample.

[0152] In this embodiment, the formation water permeability is calculated based on the inlet pressure, outlet pressure, and formation water flow rate using the following formula:

[0153] In the formula: k w Q represents the formation water permeability. w denoted as formation water flow rate; P1 and P2 are the inlet and outlet pressures of the processed fourth rock sample, respectively; L is the length of the processed fourth rock sample; A is the cross-sectional area of ​​the processed fourth rock sample; μ is the viscosity.

[0154] Accordingly, the formula for calculating the formation water initiation pressure based on the caprock thickness and initiation pressure gradient is: P q =TPG×h

[0155] In the formula, P q is the formation water initiation pressure; TPG is the initiation pressure gradient; h is the caprock thickness.

[0156] In summary, the caprock sealing evaluation method for underground compressed flue gas energy storage systems provided in this embodiment obtains rock samples corresponding to the caprock of the underground compressed flue gas energy storage system and determines the caprock lithology, clay content, caprock thickness, porosity, average pore size, most probable pore size, and median pore size based on the rock samples. The rock samples are then decomposed into four rock samples: a first rock sample, a second rock sample, a third rock sample, and a fourth rock sample. The contact angle between formation water and flue gas and the interfacial tension between formation water and flue gas are measured based on the processed first rock sample. The shear strength and tensile strength of the caprock are measured based on the processed second rock sample. The absolute helium permeability is measured based on the processed third rock sample. Finally, the flue gas breakthrough pressure and cutoff pressure, formation water permeability, and formation water initiation pressure of the caprock are measured based on the processed fourth rock sample. By defining specific caprock sealing evaluation indicators, the sealing evaluation of the caprock becomes more accurate.

[0157] Furthermore, this embodiment decomposes the rock sample into a first rock sample, a second rock sample, a third rock sample, and a fourth rock sample for different calculations, making the subsequent evaluation of the caprock sealing of the underground compressed flue gas energy storage system more accurate and comprehensive.

[0158] Furthermore, this embodiment improves the accuracy of the caprock sealing evaluation for subsequent underground compressed flue gas energy storage systems by calculating the absolute helium permeability of the caprock.

[0159] Furthermore, this embodiment improves the accuracy of the caprock sealing evaluation of the underground compressed flue gas energy storage system by calculating the activation pressure of the formation water.

[0160] It should be noted that the determination of parameters corresponding to all sub-attributes in step S202 of this application also includes: determining the chemical composition parameters of the reservoir formation water, specifically: using water quality analysis methods such as ICP-MS to analyze the main chemical composition of the reservoir formation water at the proposed site, including pH, conductivity, total salinity, redox potential, and main anions and cations; determining the flue gas composition parameters, specifically: using methods such as Fourier transform infrared spectroscopy to analyze the main gas composition of the flue gas to be injected at the site, including CO2, N2, O2, SOx, and NOx; and determining the characteristics of the caprock pore structure. The determination of the characteristic parameters is as follows: Given that the pores of the caprock are mainly micro- and nano-pores, the pore size distribution of the caprock was systematically characterized using high-pressure mercury intrusion porosimetry, low-pressure nitrogen adsorption, and low-pressure carbon dioxide adsorption methods, based on the obtained caprock samples. High-pressure mercury intrusion porosimetry used pore data ranging from 50 nm to 10 μm, low-pressure nitrogen adsorption used pore data ranging from 2 to 50 nm, and low-pressure carbon dioxide adsorption used pore data ranging from 0.37 to 2 nm. Combining the measured pore data, pore size-pore volume and pore size-cumulative pore volume curves were plotted, and the porosity and average pore size (D) of the caprock were obtained accordingly. A (i.e., the average aperture) and the most probable aperture (D) MP (i.e., the aperture value with the highest probability) and the median aperture (D) M (This refers to the pore size when the cumulative pore volume accounts for 50% of the total pore volume).

[0161] Figure 3 is a schematic diagram of the structure of the underground compressed flue gas energy storage system cap cover sealing evaluation system provided in an embodiment of this application. As shown in Figure 3, the underground compressed flue gas energy storage system cap cover sealing evaluation system includes: a first determination module 301, an acquisition module 302, a construction module 303, a second determination module 304, a processing module 305, a calculation module 306, and a third determination module 307.

[0162] The first determining module 301 is used to obtain the basic attributes corresponding to the cap layer of the underground compressed flue gas energy storage system and determine the sub-attributes corresponding to each basic attribute.

[0163] Module 302 is used to retrieve the parameters corresponding to all sub-attributes;

[0164] Construction module 303 is used to construct the evaluation index system table of the cap layer sealing performance of the underground compressed flue gas energy storage system based on the basic attributes and all the sub-attributes;

[0165] The second determining module 304 is used to construct a corresponding judgment matrix based on the evaluation index system table of the sealing performance of the underground compressed flue gas energy storage system cap layer, and to determine the weight of each basic attribute and the weight of each sub-attribute based on the judgment matrix.

[0166] Processing module 305 is used to assign scores to all sub-attributes according to the parameters corresponding to all sub-attributes, so as to determine the score corresponding to each sub-attribute;

[0167] Calculation module 306 is used to calculate the total score of the capping capacity of the underground compressed flue gas energy storage system based on the weights of each basic attribute, the weights of each sub-attribute, and the scores corresponding to each sub-attribute.

[0168] The third determining module 307 is used to determine the sealing performance level of the cover layer of the underground compressed flue gas energy storage system based on the total score.

[0169] In one possible implementation, the basic attributes include basic physical properties, wettability parameters, mechanical parameters, flue gas breakthrough parameters, and formation water permeability parameters; all sub-attributes include caprock lithology, clay content, caprock thickness, porosity, absolute helium permeability, average pore size, most probable pore size, median pore size, formation water-flue gas-rock contact angle, formation water-flue gas interfacial tension, shear strength, tensile strength, flue gas breakthrough pressure, flue gas cutoff pressure, formation water initiation pressure, and formation water permeability; correspondingly, the first determining module 301 is specifically used to: determine the... The basic physical properties include the caprock lithology, clay content, caprock thickness, porosity, absolute helium permeability, average pore size, most probable pore size, and median pore size; the wettability parameters include the formation water-flue gas-rock contact angle and formation water-flue gas interfacial tension; the mechanical parameters include the shear strength and tensile strength; the flue gas breakthrough parameters include the flue gas breakthrough pressure and flue gas cutoff pressure; and the formation water permeability parameters include the formation water initiation pressure and formation water permeability.

[0170] In one possible implementation, the acquisition module 302 specifically includes:

[0171] The determination unit 3021 is used to obtain rock samples corresponding to the caprock of the underground compressed flue gas energy storage system, and determine the caprock lithology, clay content, caprock thickness, porosity, average pore size, most probable pore size and median pore size based on the rock samples.

[0172] The decomposition unit 3022 is used to decompose the rock sample into a first rock sample, a second rock sample, a third rock sample, and a fourth rock sample on an average basis;

[0173] The first measuring unit 3023 is used to process the first rock sample to obtain a processed first rock sample, and to measure the formation water-flue gas-rock contact angle and formation water-flue gas interfacial tension corresponding to the caprock based on the processed first rock sample.

[0174] The second measuring unit 3024 is used to process the second rock sample to obtain a processed second rock sample, and to measure the shear strength and tensile strength of the cover layer based on the processed second rock sample.

[0175] The first calculation unit 3025 is used to process the third rock sample to obtain a processed third rock sample, measure the steady-state flow rate of the processed third rock sample under different helium injection pressures, as well as the inlet pressure and outlet pressure at both ends, and calculate the helium permeability under different pressures based on the inlet pressure, the outlet pressure, and the steady-state flow rate; and obtain the absolute helium permeability of the caprock by linearly fitting the helium permeability and the average pore pressure under different pressures.

[0176] The third measuring unit 3026 is used to process the fourth rock sample to obtain a processed fourth rock sample, and to measure the flue gas breakthrough pressure and cut-off pressure corresponding to the cap layer based on the processed fourth rock sample.

[0177] The second calculation unit 3027 is used to determine the formation water flow rate and initiation pressure gradient corresponding to the caprock based on the processed fourth rock sample, and to calculate the formation water permeability based on the inlet pressure, the outlet pressure and the formation water flow rate; and to calculate the formation water initiation pressure based on the caprock thickness and the initiation pressure gradient.

[0178] In one possible implementation, the formula for calculating the helium permeability at different pressures based on the inlet pressure, the outlet pressure, and the steady-state flow rate is as follows:

[0179] In the formula, k g Q represents the helium permeability. g The steady-state flow rate; p1 and p2 are the inlet and outlet pressures at both ends of the processed third rock sample, respectively; μ g Z is the gas dynamic viscosity under experimental conditions; Z is the gas compressibility factor under experimental conditions; Z a For the experimental temperature and p a Gas compressibility factor under the given conditions; L and A are the length and cross-sectional area of ​​the processed third rock sample, respectively;

[0180] Accordingly, the formula for calculating the absolute helium permeability of the caprock after linearly fitting the helium permeability and average pore pressure under different pressures is as follows:

[0181] In the formula: k ∞k represents the absolute permeability of the helium gas. g b is the helium permeability; b is the slip coefficient; The average pore pressure is denoted as .

[0182] In one possible implementation, the formula for calculating formation water permeability based on the inlet pressure, the outlet pressure, and the formation water flow rate is as follows:

[0183] In the formula: k w Q represents the formation water permeability. w The formation water flow rate is given; P1 and P2 are the inlet and outlet pressures of the processed fourth rock sample, respectively; L is the length of the processed fourth rock sample; A is the cross-sectional area of ​​the processed fourth rock sample; μ is the viscosity.

[0184] Accordingly, the formula for calculating the formation water initiation pressure based on the caprock thickness and the initiation pressure gradient is: P q =TPG×h

[0185] In the formula, P q is the formation water initiation pressure; TPG is the initiation pressure gradient; and h is the caprock thickness.

[0186] In one possible implementation, the construction module 303 specifically includes:

[0187] The determining unit 3031 is used to determine each basic attribute as a criterion layer and all sub-attributes as an indicator layer;

[0188] Construction unit 3032 is used to construct the evaluation index system table of the cover layer sealing of the underground compressed flue gas energy storage system according to the preset target layer, the criterion layer and the index layer;

[0189] Accordingly, the second determining module 304 specifically includes:

[0190] The first construction unit 3041 is used to construct a first judgment matrix based on the criteria layer in the evaluation index system table of the cover layer sealing performance of the underground compressed flue gas energy storage system.

[0191] The second construction unit 3042 is used to construct a second judgment matrix based on the index layer and according to the division of each basic attribute;

[0192] The determining unit 3043 is used to determine the weights of each basic attribute and each sub-attribute based on the first judgment matrix and the second judgment matrix.

[0193] The apparatus provided in this embodiment can be used to execute the technical solutions of the above method embodiments. Its implementation principle and technical effects are similar, and will not be described again here.

[0194] Figure 4 is a schematic diagram of the structure of the caprock sealing evaluation device for the underground compressed flue gas energy storage system provided in this embodiment of the application. As shown in Figure 4, the caprock sealing evaluation device for the underground compressed flue gas energy storage system includes: a simulated flue gas cylinder 101, a helium cylinder 102, a gas booster pump 103, a gas storage tank 104, a gas storage tank pressure gauge 105, a water tank 106, a constant speed and constant pressure pump 107, a water storage tank 108, a vacuum pump 109, an inlet pressure gauge 110, a core holder 111, an outlet pressure gauge 112, a ring pressure tracking pump 113, a ring pressure gauge 114, a gas flow meter 115, a breakthrough pressure bubble detector 116, a capillary flow meter 117, and a constant temperature chamber 118.

[0195] The simulated flue gas cylinder 101 and helium cylinder 102 are connected by pipes to the gas booster pump 103.

[0196] In this embodiment, valves are installed on the simulated flue gas cylinder 101 and helium cylinder 102.

[0197] The gas booster pump 103 is connected to the gas storage tank 104 by a pipeline.

[0198] In this embodiment, a valve is installed on the pipeline between the gas booster pump 103 and the gas storage tank 104.

[0199] In addition, a safety valve is installed at the end of the pipeline.

[0200] Water tank 106 is connected to constant speed and constant pressure pump 107 by a pipeline.

[0201] A constant speed and constant pressure pump 107 is connected to a water storage tank 108 via a pipeline.

[0202] In this embodiment, a valve is installed on the pipeline between the constant speed and constant pressure pump 107 and the water storage tank 108.

[0203] The gas storage tank 104, water storage tank 108, and vacuum pump 109 are connected by pipes to the core holder 111.

[0204] In this embodiment, three valves are installed on the pipeline between the gas storage tank 104, the water storage tank 108, the vacuum pump 109, and the core holder 111, and are controlled by another valve.

[0205] The pressure gauge 105 is installed on the gas tank 104 and is used to measure the pressure of the gas tank.

[0206] The ring pressure tracking pump 113 is connected to the core holder 111 by a pipeline.

[0207] The ring pressure gauge 114 is installed on the pipeline between the ring pressure tracking pump 113 and the core holder 111 to measure the ring pressure.

[0208] In this embodiment, a valve is installed on the pipeline between the ring pressure gauge 114 and the ring pressure tracking pump 113.

[0209] An inlet pressure gauge 110 is installed at the inlet of the core holder 111 to measure the inlet pressure;

[0210] The core holder 111 is connected by a pipeline to the gas flow meter 115, the breakthrough pressure bubble detector 116 and the capillary flow meter 117.

[0211] In this embodiment, three valves are installed on the pipeline between the gas flow meter 115, the breakthrough pressure bubble detector 116, and the capillary flow meter 117.

[0212] In this embodiment, the gas flow meter 115 is used to test the gas flow rate during helium permeation, and its range is 20 mL / min-200 mL / min.

[0213] In this embodiment, the capillary flow meter 117 is used to test the formation water flow rate of the caprock, with an accuracy of 10⁻⁸ mL / s.

[0214] In this embodiment, the breakthrough pressure bubble detector 116 indicates the breakthrough time and the corresponding breakthrough pressure based on the generation and movement of bubbles in the U-tube.

[0215] The outlet pressure gauge 112 is installed at the outlet of the core holder 111 and is used to measure the outlet pressure.

[0216] The constant temperature chamber 118 is used to maintain the temperature of the gas storage tank 104, water storage tank 108, core holder 111, gas flow meter 115, breakthrough pressure bubble detector 116 and capillary flow meter 117 to a constant state.

[0217] In summary, the underground compressed flue gas energy storage system caprock sealing evaluation device provided in this embodiment consists of a simulated flue gas cylinder 101, a helium cylinder 102, a gas booster pump 103, a gas storage tank 104, a gas storage tank pressure gauge 105, a water tank 106, a constant speed and constant pressure pump 107, a water storage tank 108, a vacuum pump 109, an inlet pressure gauge 110, a core holder 111, an outlet pressure gauge 112, an annular pressure tracking pump 113, an annular pressure gauge 114, a gas flow meter 115, a breakthrough pressure bubble detector 116, and a capillary flow meter 117 connected by pipelines. A constant temperature chamber 118 maintains the temperature of the gas storage tank 104, the water storage tank 108, the core holder 111, the gas flow meter 115, the breakthrough pressure bubble detector 116, and the capillary flow meter 117 at a constant state, enabling the underground compressed flue gas energy storage system caprock sealing evaluation device to measure various data, thus solving the problem of the current single-function devices based on testing requirements.

[0218] Figure 5 is a schematic diagram of the hardware structure of the computer device provided in this embodiment. As shown in Figure 5, the computer device in this embodiment includes: a processor 501 and a memory 502; the memory stores computer execution instructions; at least one processor executes the computer execution instructions stored in the memory, causing at least one processor to execute the above-mentioned method for evaluating the sealing performance of the cap layer of an underground compressed flue gas energy storage system.

[0219] Alternatively, the memory 502 can be either standalone or integrated with the processor 501.

[0220] When the memory 502 is set up independently, the computer device also includes a bus 503 for connecting the memory 502 and the processor 501.

[0221] This application embodiment also provides a computer storage medium storing computer execution instructions. When the processor executes the computer execution instructions, it implements the above-described method for evaluating the sealing performance of the cap layer of an underground compressed flue gas energy storage system.

[0222] This application also provides a computer program product, including a computer program, which, when executed by a processor, implements the above-described method for evaluating the sealing performance of the cap layer of an underground compressed flue gas energy storage system.

[0223] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or modules, and may be electrical, mechanical, or other forms.

[0224] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to implement the solution of this embodiment according to actual needs.

[0225] Furthermore, the functional modules in the various embodiments of this application can be integrated into one processing unit, or each module can exist physically separately, or two or more modules can be integrated into one unit. The unit composed of the above modules can be implemented in hardware or in the form of hardware plus software functional units.

[0226] The integrated modules implemented as software functional modules described above can be stored in a computer-readable storage medium. These software functional modules, stored in a storage medium, include several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute some steps of the methods described in the various embodiments of this application.

[0227] It should be understood that the aforementioned processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. A general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this invention can be directly manifested as being executed by a hardware processor, or executed by a combination of hardware and software modules within the processor.

[0228] The memory may include high-speed RAM, and may also include non-volatile storage (NVM), such as at least one disk storage device, and may also be a USB flash drive, external hard drive, read-only memory, disk or optical disc, etc.

[0229] The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of illustration, the buses shown in the accompanying drawings are not limited to a single bus or a single type of bus.

[0230] The aforementioned storage media can be implemented from any type of volatile or non-volatile storage device or a combination thereof, such as Static Random-Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read-Only Memory (EPROM), Programmable Read-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The storage media can be any available medium accessible to general-purpose or special-purpose computers.

[0231] An exemplary storage medium is coupled to a processor, enabling the processor to read information from and write information to the storage medium. Alternatively, the storage medium can be an integral part of the processor. Both the processor and the storage medium can reside in an Application Specific Integrated Circuit (ASIC). Alternatively, the processor and storage medium can exist as discrete components in an electronic device or host device.

[0232] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0233] 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 sealing performance of the caprock of an underground compressed flue gas energy storage system, characterized in that, Applied to computer equipment, including: Obtain the basic attributes corresponding to the cap layer of the underground compressed flue gas energy storage system, and determine the sub-attributes corresponding to each basic attribute; Get all parameters corresponding to all sub-attributes; Based on the aforementioned basic attributes and all the aforementioned sub-attributes, construct the evaluation index system table for the cap layer sealing performance of the underground compressed flue gas energy storage system. Construct a corresponding judgment matrix based on the evaluation index system table of the sealing performance of the cap layer of the underground compressed flue gas energy storage system, and determine the weights of each basic attribute and each sub-attribute based on the judgment matrix. All sub-attributes are scored according to the parameters corresponding to all sub-attributes to determine the score corresponding to each sub-attribute. The total score of the capping capacity of the underground compressed flue gas energy storage system is calculated based on the weights of each basic attribute, the weights of each sub-attribute, and the scores corresponding to each sub-attribute. The sealing performance level of the cap layer of the underground compressed flue gas energy storage system is determined based on the total score.

2. The method according to claim 1, characterized in that, The basic properties include basic physical properties, wettability parameters, mechanical parameters, flue gas breakthrough parameters, and formation water permeability parameters; the sub-properties include caprock lithology, clay content, caprock thickness, porosity, absolute helium permeability, average pore size, most probable pore size, median pore size, formation water-flue gas-rock contact angle, formation water-flue gas interfacial tension, shear strength, tensile strength, flue gas breakthrough pressure, flue gas cutoff pressure, formation water initiation pressure, and formation water permeability. Accordingly, determining the sub-attributes corresponding to each basic attribute includes: Determine the caprock lithology, clay content, caprock thickness, porosity, absolute helium permeability, average pore size, most probable pore size, and median pore size corresponding to the basic physical property parameters; determine the formation water-flue gas-rock contact angle and formation water-flue gas interfacial tension corresponding to the wettability parameters. Determine the shear strength and tensile strength corresponding to the mechanical parameters; determine the flue gas breakthrough pressure and flue gas cutoff pressure corresponding to the flue gas breakthrough parameters; determine the formation water initiation pressure and formation water permeability corresponding to the formation water permeability parameters.

3. The method according to claim 2, characterized in that, The step of obtaining the parameters corresponding to all the sub-attributes includes: Obtain rock samples corresponding to the caprock of the underground compressed flue gas energy storage system, and determine the caprock lithology, clay content, caprock thickness, porosity, average pore size, most probable pore size, and median pore size based on the rock samples. The rock sample was decomposed into a first rock sample, a second rock sample, a third rock sample, and a fourth rock sample; The first rock sample is processed to obtain a processed first rock sample, and the formation water-flue gas-rock contact angle and formation water-flue gas interfacial tension corresponding to the caprock are determined based on the processed first rock sample. The second rock sample is processed to obtain a processed second rock sample, and the shear strength and tensile strength of the cap layer are determined based on the processed second rock sample. The third rock sample is processed to obtain a processed third rock sample. The steady-state flow rate of the processed third rock sample under different helium injection pressures, as well as the inlet and outlet pressures at both ends, are measured. The helium permeability under different pressures is calculated based on the inlet pressure, the outlet pressure, and the steady-state flow rate. The absolute helium permeability of the caprock is obtained by linearly fitting the helium permeability and the average pore pressure under different pressures. The fourth rock sample is processed to obtain a processed fourth rock sample, and the flue gas breakthrough pressure and cut-off pressure corresponding to the cap layer are determined based on the processed fourth rock sample. The formation water flow rate and initiation pressure gradient corresponding to the caprock were determined based on the processed fourth rock sample, and the formation water permeability was calculated based on the inlet pressure, the outlet pressure, and the formation water flow rate; the formation water initiation pressure was calculated based on the caprock thickness and the initiation pressure gradient.

4. The method according to claim 3, characterized in that, The formula for calculating the helium permeability at different pressures based on the inlet pressure, the outlet pressure, and the steady-state flow rate is as follows: In the formula, k g Q represents the helium permeability. g The steady-state flow rate; p1 and p2 are the inlet and outlet pressures at both ends of the processed third rock sample, respectively; μ g Z is the gas dynamic viscosity under experimental conditions; Z is the gas compressibility factor under experimental conditions; Z a For the experimental temperature and p a The gas compressibility factor under the given conditions; L and A are the length and cross-sectional area of ​​the processed third rock sample, respectively.

5. The method according to claim 3 or 4, characterized in that, The formula for calculating the absolute helium permeability of the caprock after linearly fitting the helium permeability and average pore pressure under different pressures is as follows: In the formula: k ∞ k represents the absolute permeability of the helium gas. g b is the helium permeability; b is the slip coefficient. The average pore pressure is denoted as .

6. The method according to any one of claims 3 to 5, characterized in that, The formula for calculating formation water permeability based on the inlet pressure, the outlet pressure, and the formation water flow rate is as follows: In the formula: k w Q represents the formation water permeability. w P1 is the formation water flow rate; P2 and P1 are the inlet and outlet pressures of the processed fourth rock sample, respectively; L is the length of the processed fourth rock sample; A is the cross-sectional area of ​​the processed fourth rock sample; μ is the viscosity.

7. The method according to any one of claims 3 to 6, characterized in that, The formula for calculating the formation water initiation pressure based on the caprock thickness and the initiation pressure gradient is: P q =TPG×h In the formula, P q is the formation water initiation pressure; TPG is the initiation pressure gradient; and h is the caprock thickness.

8. The method according to any one of claims 1 to 7, characterized in that, The table describing the evaluation index system for the caprock sealing of the underground compressed flue gas energy storage system, constructed based on the basic attributes and all sub-attributes, includes: Each of the basic attributes is defined as the criterion layer, and all the sub-attributes are defined as the indicator layer; Based on the preset target layer, the criterion layer, and the index layer, construct the evaluation index system table for the cap layer sealing performance of the underground compressed flue gas energy storage system; Accordingly, the step of constructing a corresponding judgment matrix based on the evaluation index system table for the sealing performance of the cap layer of the underground compressed flue gas energy storage system, and determining the weights of each basic attribute and each sub-attribute based on the judgment matrix, includes: A first judgment matrix is ​​constructed based on the criteria layer in the evaluation index system table for the sealing performance of the cap layer of the underground compressed flue gas energy storage system. Based on the aforementioned indicator layer, and according to the division of each basic attribute, a second judgment matrix is ​​constructed; The weights of each basic attribute and each sub-attribute are determined based on the first judgment matrix and the second judgment matrix.

9. A capping layer sealing evaluation system for an underground compressed flue gas energy storage system, characterized in that, Applied to computer equipment, including: The first determining module is used to obtain the basic attributes corresponding to the cap layer of the underground compressed flue gas energy storage system, and to determine the sub-attributes corresponding to each basic attribute. The retrieval module is used to retrieve the parameters corresponding to all sub-attributes; The construction module is used to construct the evaluation index system table for the cap layer sealing of the underground compressed flue gas energy storage system based on the basic attributes and all the sub-attributes. The second determining module is used to construct a corresponding judgment matrix based on the evaluation index system table of the sealing performance of the underground compressed flue gas energy storage system cap layer, and to determine the weight of each basic attribute and the weight of each sub-attribute based on the judgment matrix. The processing module is used to assign scores to all sub-attributes based on the parameters corresponding to all sub-attributes, so as to determine the score corresponding to each sub-attribute; The calculation module is used to calculate the total score of the capping capacity of the underground compressed flue gas energy storage system based on the weights of each basic attribute, the weights of each sub-attribute, and the scores corresponding to each sub-attribute. The third determining module is used to determine the sealing performance level of the cap layer of the underground compressed flue gas energy storage system based on the total score.

10. A device for evaluating the sealing performance of the cap layer of an underground compressed flue gas energy storage system, characterized in that, include: Simulated flue gas cylinders, helium cylinders, gas booster pumps, gas storage tanks, gas storage tank pressure gauges, water tanks, constant speed and constant pressure pumps, water storage tanks, vacuum pumps, inlet pressure gauges, core holders, outlet pressure gauges, ring pressure tracking pumps, ring pressure gauges, gas flow meters, breakthrough pressure bubble detectors, capillary flow meters, and constant temperature chambers. The simulated flue gas cylinder and the helium cylinder are connected to the gas booster pump via pipelines. The gas booster pump is connected to the gas storage tank via a pipeline. The water tank is connected to the constant speed and constant pressure pump via a pipeline. The constant speed and constant pressure pump is connected to the water storage tank by a pipeline. The gas storage tank, the water storage tank, and the vacuum pump are connected by pipelines to the core holder. The pressure gauge for the gas storage tank is installed on the gas storage tank and is used to measure the pressure of the gas storage tank. The annular pressure tracking pump is connected to the core holder via a pipeline. The annular pressure gauge is installed on the pipeline between the annular pressure tracking pump and the core holder, and is used to measure the annular pressure. The inlet pressure gauge is installed at the inlet of the core holder and is used to measure the inlet pressure; The core holder is connected by a pipeline to the gas flow meter, the breakthrough pressure bubble detector, and the capillary flow meter. The outlet pressure gauge is installed at the outlet of the core holder and is used to measure the outlet pressure. The constant temperature chamber is used to maintain the temperature of the gas storage tank, the water storage tank, the core holder, the gas flow meter, the breakthrough pressure bubble detector, and the capillary flow meter to a constant state.

11. A computer device, characterized in that, include: At least one processor and memory; The memory stores computer-executed instructions; The at least one processor executes computer execution instructions stored in the memory, causing the at least one processor to perform the method for evaluating the capping seal of an underground compressed flue gas energy storage system as described in any one of claims 1 to 8.

12. A computer storage medium, characterized in that, The computer storage medium stores computer execution instructions. When the processor executes the computer execution instructions, it implements the method for evaluating the sealing performance of the cap layer of the underground compressed flue gas energy storage system as described in any one of claims 1 to 8.

13. A computer program product, characterized in that, The system includes a computer program that, when executed by a processor, implements the method for evaluating the caprock sealing of an underground compressed flue gas energy storage system as described in any one of claims 1 to 8.

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