Calculation methods and systems for using carbon dioxide as a cushion gas in underground salt caverns / hydrogen reservoirs

Abstract

This invention provides a calculation method and system for using carbon dioxide as the cushion gas in underground salt cavern gas storage / hydrogen reservoirs. The method first acquires wellbore and cavity parameters, and then uses a data analysis platform to calculate the physical properties of carbon dioxide at different temperatures and pressures. Based on the wellbore and cavity parameters, a physical simulation model of the gas / hydrogen reservoir is established. The physical model is solved according to the physical properties and set boundary conditions to determine effective salt cavern temperature and pressure data. Based on the salt cavern temperature and pressure data and the physical properties of natural gas / hydrogen, a dynamic injection / production gas calculation model for the gas / hydrogen reservoir is determined. By setting different boundary conditions to simulate the mixing degree of the cushion gas, the injection / production boundary conditions that meet the requirements are selected as the target injection / production parameters. This scheme can accurately model the operating status of gas / hydrogen reservoirs using carbon dioxide as the cushion gas, calculate reliable dynamic injection / production gas volumes in real time, and optimize the injection / production rate based on the mixing degree, thus providing assistance for gas / hydrogen reservoir injection and production on-site.

Description

Technical Field

[0001] This invention relates to the field of energy storage and optimization technology, and in particular to a calculation method and system for using carbon dioxide as underground salt cavern gas storage / hydrogen reservoir cushion gas. Background Technology

[0002] Underground salt cavern gas / hydrogen storage has advantages such as high injection and production efficiency and low requirement for cushion gas, thus it has been vigorously developed. Salt cavern gas / hydrogen storage can also be applied to carbon dioxide storage, including the use of carbon dioxide as cushion gas in underground salt cavern gas / hydrogen storage. In the energy storage field, to ensure the stability of the salt cavern morphology during operation and to provide the necessary pressure for natural gas extraction, a certain amount of gas must always remain in the salt cavern; this gas is called cushion gas. Cushion gas is a part of the gas stored in the underground gas storage facility; it is not extracted during peak-shaving injection and production operations and is called "dead gas." The construction of cushion gas plays a very important role in the construction of the overall gas storage facility. In practical applications, using conventional cushion gas construction methods, the investment in cushion gas can reach as high as 28% of the total investment in building the gas storage facility, which is quite costly and not conducive to large-scale application and sustainable development.

[0003] Based on this, using carbon dioxide as the cushion gas for gas storage facilities can save significant funds and contribute to the development of carbon neutrality optimization goals. Furthermore, carbon dioxide's high compressibility can increase the injectable and recoverable ratio of natural gas, thus improving the economic efficiency of salt cavern gas storage facilities to some extent. However, the use of carbon dioxide as cushion gas for gas / hydrogen storage facilities is still in the feasibility study stage, and related research suffers from numerous technical shortcomings. For example, the patent document "Method for storing natural gas using CO2 as cushion gas in salt cavern underground gas storage facilities" proposes placing gasbags inside the gas storage facility and filling them with carbon dioxide as cushion gas. While this method addresses to some extent the high investment costs associated with existing natural gas cushion gas technology and the problem of increased extracted natural gas and decreased calorific value due to the mixing of injected and extracted natural gas with cushion gas or residual brine in the cavity, its practical operability is limited. It remains in the conceptual stage, lacks feasible technical guidance, and the manufacture and operation of the gasbags are difficult to realize. Another patent document, "A Novel Physical Model for Using Carbon Dioxide as a Subbase Gas in a Gas Storage Facility," proposes a physical model that includes a physical model device body, an experimental chamber, an operating table, and a leak detection chamber. It uses a physical experiment approach to explore carbon dioxide as a subbase gas. The experimental chamber is fixedly connected to the middle of the physical model device body. However, using a physical model for experiments involves many interfering factors and deviates significantly from actual production conditions.

[0004] Furthermore, although existing researchers have conducted theoretical calculations on the parameters of cushion gas and natural gas storage, such as the literature "Simulation Study on Mixing Cushion Gas and Working Gas in Underground Natural Gas Storage," which uses numerical simulation to establish a two-phase seepage model and a gas diffusion model, uses a jump-type solution method to determine the transient pressure distribution at various points within the storage, then determines the velocity distribution according to Darcy's law, and finally solves the gas diffusion numerical model to determine the demand for cushion gas and the optimal storage pressure required for natural gas injection and production, this method does not consider the changes in gas physical parameters with pressure and temperature, nor the coupling factors between multiple physical fields. Therefore, it cannot provide reliable data for practical engineering applications and cannot meet the requirements of actual process implementation.

[0005] Therefore, there is an urgent need to provide a scientific and accurate method for calculating gas storage parameters to support the development of technology for using carbon dioxide as underground salt cavern gas storage / hydrogen reservoir cushion gas.

[0006] The information disclosed in the background section of this invention is intended only to enhance the understanding of the general background of this invention, and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a calculation method for using carbon dioxide as a cushion gas in underground salt cavern gas storage / hydrogen reservoirs. This invention proposes a gas volume calculation method based on an integrated thermo-coupling model of underground salt cavern gas storage, which can be used to simulate the mixing degree and injectable / recoverable gas volume under different injection and production rates. This is of great significance for the early realization of using carbon dioxide as a cushion gas in underground salt cavern gas storage. In a preferred embodiment, the method includes:

[0008] Data acquisition steps: Obtaining associated wellbore parameters based on well completion data, and using sonar cavity measurement technology to obtain multi-directional cavity parameters of the salt cavity;

[0009] The gas property analysis steps involve using a matching data analysis platform to calculate the physical property parameters of carbon dioxide at different temperatures and pressures, and storing the combined physical property parameters of natural gas and hydrogen.

[0010] The simulation calculation steps are as follows: a physical simulation model of the salt cavern gas storage is established based on wellbore parameters and cavity parameters; the physical model is solved according to the physical property parameters of carbon dioxide and the set boundary conditions to determine the effective salt cavity temperature and pressure data.

[0011] The gas storage parameter calculation steps, and the dynamic gas injection and production calculation model for the gas storage / hydrogen reservoir based on the salt cavity temperature and pressure data and the corresponding natural gas / hydrogen physical property parameters;

[0012] The steps for optimizing injection and production parameters include: simulating the mixing degree of carbon dioxide in the cushion gas by setting different boundary conditions; adjusting the injection and production boundary conditions based on the simulation results and the set mixing degree requirements, and using these as the target injection and production parameters.

[0013] Preferably, in one embodiment, the process of acquiring multi-directional cavity parameters using sonar cavity measurement technology in the data acquisition step includes:

[0014] Sonar cavity measurement technology is used to measure relevant sonar parameters, including measurement point, well depth, cross-sectional radius, cross-sectional area, depth range, segmented volume and cumulative volume;

[0015] Then, based on the analysis of relevant sonar parameters, the sonar cavity data is determined, including the shape of the salt cave, the total volume of the salt cave, the burial depth of the top of the salt cave, and the burial depth of the bottom of the salt cave.

[0016] Furthermore, in one embodiment, in the gas property analysis step, the set temperature and pressure data are imported into MATLAB, and MATLAB is used to calculate the real-time gas property parameters of carbon dioxide at different temperatures and pressures based on a carbon dioxide database.

[0017] In one optional embodiment, the simulation calculation step includes:

[0018] The calculated carbon dioxide physical property parameters are imported into a multiphysics simulation system. Combined with one or more preset boundary conditions, the physical simulation model of the salt cavern gas / hydrogen reservoir is used for simulation to obtain the corresponding real-time temperature and pressure data of the gas / hydrogen reservoir, which are used as the effective salt cavern temperature and pressure.

[0019] Specifically, in a preferred embodiment, the gas storage parameter calculation step involves determining the dynamic gas injection volume calculation model for the gas storage facility as described in the following formula:

[0020] G in =G max -G r

[0021] Determine the dynamic gas extraction calculation model for the gas storage / hydrogen reservoir as described in the following formula.

[0022] G out =G r -G min

[0023] in, G in It refers to the dynamic gas injection rate of the gas storage / hydrogen reservoir, G. out It is the active gas production rate of the gas storage / hydrogen reservoir, G r This is the real-time storage capacity of natural gas / hydrogen, P. r T r Z rρ r These are the real-time pressure, temperature, compressibility factor, and density within the salt cavity, respectively; V is the volume of the salt cavity; and M is the density of the salt cavity. g It is the relative molecular mass of natural gas / hydrogen, G max This refers to the natural gas / hydrogen storage capacity at the maximum operating pressure and temperature of the salt chamber, G. min It represents the natural gas / hydrogen storage capacity at the minimum operating pressure and minimum operating temperature of the salt chamber.

[0024] Furthermore, in one embodiment, in the step of optimizing injection and production parameters, different gas injection rate boundary conditions and gas production rate boundary conditions are set for different effective salt cavity temperatures and pressures. The gas storage operation process is simulated using a simulation physical model to analyze the mixing of carbon dioxide in the cushion gas and to determine the gas injection rate and gas production rate that meet the process requirements.

[0025] In a preferred embodiment, in the simulation calculation step, the process of importing the calculated carbon dioxide physical property parameters into the multiphysics simulation system is carried out by calling MATLAB. The temperature and pressure data are used as tags to call MATLAB for calculation, and the physical property parameters are returned to the multiphysics simulation system.

[0026] Furthermore, in one embodiment, in the simulation calculation step, the process of importing the calculated carbon dioxide physical property parameters into the multiphysics simulation system is to generate a text document of the carbon dioxide physical property parameters and directly import it into the multiphysics simulation system.

[0027] Based on other aspects of the methods described in any one or more of the foregoing embodiments, the present invention also provides a storage medium storing program code capable of implementing the methods described in any one or more of the foregoing embodiments.

[0028] On the other hand, based on the application of the methods described in any one or more of the above embodiments, the present invention also provides a computational system for using carbon dioxide as underground salt cavern gas storage / hydrogen reservoir cushion gas, the system performing the methods described in any one or more of the above embodiments.

[0029] Compared with the closest prior art, the present invention also has the following beneficial effects:

[0030] This invention provides a calculation method and system for using carbon dioxide as a subgrade gas in underground salt caverns / hydrogen reservoirs. The method first acquires associated wellbore parameters and salt cavity size parameters, then uses a data analysis platform to calculate the physical properties of carbon dioxide at different temperatures and pressures. Based on the wellbore and cavity parameters, a physical simulation model of the salt cavern gas storage is established. The physical model is then solved according to the carbon dioxide's physical properties and set boundary conditions to determine effective salt cavity temperature and pressure data. By simulating and solving for the salt cavity temperature and pressure data based on the physical simulation model and considering the carbon dioxide's physical properties, the obtained temperature and pressure data can accurately reflect the actual gas production situation of using carbon dioxide as a subgrade gas in underground salt caverns / hydrogen reservoirs, providing a realistic and accurate data foundation for subsequent calculation models and decisions regarding gas storage / hydrogen parameters.

[0031] By setting different boundary conditions to simulate the mixing degree of carbon dioxide in the cushion gas, and adjusting the injection and production boundary conditions according to the simulation results, the injection and production boundary conditions that meet the requirements are selected as the target injection and production parameters. The embodiments of the present invention take into account the different mixing degrees of natural gas / hydrogen and carbon dioxide under different injection and production conditions. By comprehensively simulating the mixing degree of carbon dioxide in the cushion gas, the mixing degree of the gas under the injection and production conditions is kept within an acceptable range. High-quality operation injection and production parameters are selected, which has positive and important guiding significance for the stable operation of underground gas storage facilities using carbon dioxide as cushion gas.

[0032] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0033] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0034] Figure 1 This is a schematic diagram of the underground salt cavern gas / hydrogen storage structure according to an embodiment of the present invention;

[0035] Figure 2 This is a flowchart illustrating the calculation method for using carbon dioxide as underground salt cavern gas storage / hydrogen reservoir cushion gas provided in the embodiments of the present invention;

[0036] Figure 3 This is a schematic diagram illustrating the implementation principle of the calculation method for using carbon dioxide as underground salt cavern gas storage / hydrogen reservoir cushion gas provided in the embodiments of the present invention;

[0037] Figure 4This is a schematic diagram of the calculation system for using carbon dioxide as underground salt cavern gas storage / hydrogen reservoir cushion gas provided in the embodiments of the present invention. Detailed Implementation

[0038] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples. Those skilled in the art will then fully understand how the present invention uses technical means to solve technical problems and achieve technical effects, and will be able to implement the present invention specifically based on the above-described implementation process. It should be noted that, as long as there is no conflict, the various embodiments and features of the present invention can be combined with each other, and the resulting technical solutions are all within the protection scope of the present invention.

[0039] Although the flowchart describes the operations as sequential processes, many of these operations can be performed in parallel, concurrently, or simultaneously. The order of the operations can be rearranged. A process can terminate when its operation is complete, but it may also have additional steps not included in the diagram. A process can correspond to a method, function, procedure, subroutine, subroutine, etc.

[0040] Computer equipment includes user equipment and network equipment. User equipment or clients include, but are not limited to, computers, smartphones, PDAs, etc.; network equipment includes, but is not limited to, a single network server, a server group consisting of multiple network servers, or a cloud based on cloud computing consisting of a large number of computers or network servers. Computer equipment can operate independently to implement this invention, or it can connect to a network and implement this invention through interaction with other computer equipment in the network. The network in which the computer equipment is located includes, but is not limited to, the Internet, wide area network, metropolitan area network, local area network, VPN network, etc.

[0041] The terms “first,” “second,” etc., may be used herein to describe various units, but these units should not be limited by these terms; they are used merely to distinguish one unit from another. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items. When a unit is referred to as “connected” or “coupled” to another unit, it may be directly connected or coupled to said other unit, or there may be intermediate units present.

[0042] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments. Unless the context clearly indicates otherwise, the singular forms “a” and “an” as used herein are also intended to include the plural. It should also be understood that the terms “comprising” and / or “including” as used herein specify the presence of the stated features, integers, steps, operations, units, and / or components, without excluding the presence or addition of one or more other features, integers, steps, operations, units, components, and / or combinations thereof.

[0043] In the field of energy storage, to ensure the stability of the salt cavity morphology during operation and to provide the necessary pressure for the extraction of natural gas / hydrogen, a certain amount of gas must always remain in the salt cavity. This gas is called cushion gas. Cushion gas is part of the gas storage in underground gas / hydrogen storage facilities. It is not extracted during the peak-shaving injection and extraction operations of the gas storage facility and is called "dead gas." The construction of cushion gas plays a very important role in the construction of the overall gas storage facility. In practical applications, using conventional cushion gas construction methods, the investment in cushion gas can even reach about 28% of the total investment in the construction of the gas storage facility, which is quite costly and not conducive to large-scale application and sustainable development.

[0044] Carbon dioxide is the most important greenhouse gas. Using carbon dioxide as the cushion gas for salt cavern gas storage can reduce the amount of carbon dioxide in the air, give full play to the role of underground gas storage in the energy field, and support the early realization of the carbon neutrality optimization goal. In addition, carbon dioxide is highly compressible, which can also increase the injectable and recoverable ratio of natural gas, thereby improving the economic benefits of salt cavern gas storage to a certain extent.

[0045] However, the use of carbon dioxide as a cushion gas in gas storage facilities is still in the feasibility study stage, and related research has many technical shortcomings. For example, the patent document "Method for storing natural gas using CO2 as cushion gas in underground gas storage facilities with salt caverns" proposes placing gasbags in the gas storage facility and filling them with carbon dioxide as cushion gas. While this method solves to some extent the problems of high investment costs caused by existing natural gas cushion gas technology and the problem of increased extracted natural gas and reduced calorific value due to the mixing of injected and extracted natural gas with cushion gas or residual brine in the cavity, this method is not very practical and remains at the conceptual stage. It lacks feasible technical guidance, and the manufacturing and operation of the gasbags are difficult to realize. Another patent document, "A novel physical model for using carbon dioxide as cushion gas in gas storage facilities," proposes a physical model including a main body of the physical model device, an experimental chamber, an operating table, and a leak detection chamber. It explores the use of carbon dioxide as a cushion gas using a physical experiment approach. The experimental chamber is fixedly connected to the middle of the main body of the physical model device. However, experiments using physical models have many interfering factors and deviate significantly from actual production conditions.

[0046] Furthermore, although existing researchers have conducted theoretical calculations on the parameters of cushion gas and natural gas storage, such as the literature "Simulation Study on Mixing Cushion Gas and Working Gas in Underground Natural Gas Storage," which uses numerical simulation to establish a two-phase seepage model and a gas diffusion model, uses a jump-type solution method to determine the transient pressure distribution at various points within the storage, then determines the velocity distribution according to Darcy's law, and finally solves the gas diffusion numerical model to determine the demand for cushion gas and the optimal storage pressure required for natural gas injection and production, this method does not consider the changes in gas physical parameters with pressure and temperature, nor the coupling factors between multiple physical fields. Therefore, it cannot provide reliable data for practical engineering applications and cannot meet the requirements of actual process implementation.

[0047] The researchers of this invention considered that the main problem with carbon dioxide as a cushion gas is the gas mixing problem, the injectable and recoverable gas volume of natural gas / hydrogen, and the injection and production rate. An excessively fast injection and production rate can lead to increased gas mixing. To address these problems and overcome the aforementioned shortcomings, this invention provides a calculation method and system for using carbon dioxide as a cushion gas in underground salt cavern storage / hydrogen reservoirs.

[0048] A gas volume calculation method based on an integrated thermo-coupling model of underground salt cavern gas / hydrogen storage is proposed. Based on commonly used parameters during the construction and operation of salt cavern gas storage facilities, software is used to simulate real-time parameters within the salt cavern, simulating the degree of carbon dioxide mixing under different injection and extraction conditions. Combined with a carbon dioxide database, the injectable and extractable gas volumes within the storage / hydrogen reservoir are calculated. This method can be used to simulate the degree of mixing and the injectable / extractable gas volume under different injection and extraction rates, solving the problem of using carbon dioxide as a cushion gas in underground salt cavern gas / hydrogen storage. This provides a basis for the implementation and configuration of carbon dioxide as a cushion gas in underground salt cavern gas / hydrogen storage, which is of great significance for the early realization of carbon dioxide as a cushion gas in underground salt cavern gas / hydrogen storage. Based on this, using carbon dioxide as a cushion gas in storage / hydrogen storage can save significant funds and contribute to supporting the development of carbon neutrality optimization goals.

[0049] The following describes the detailed flow of the method according to an embodiment of the present invention with reference to the accompanying drawings, the steps of which can be executed in a computer system containing, for example, a set of computer-executable instructions. Although the logical order of the steps is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than that shown here.

[0050] Example 1:

[0051] Underground salt cavern gas / hydrogen storage facilities consist of three parts: surface gas injection and production facilities, wellbore, and cavity. Figure 1 As shown, the upper space inside the cavity is used to store natural gas / hydrogen, and the lower space is used to store carbon dioxide as a cushion gas. The carbon dioxide at the bottom maintains the pressure inside the salt cavity during the gas extraction process, extracting as much natural gas as possible.

[0052] Figure 2 This diagram illustrates a flowchart of the calculation method for using carbon dioxide as a subsurface gas in underground salt caverns / hydrogen reservoirs, as provided in Embodiment 1 of the present invention. (Refer to...) Figure 2 As can be seen, the method includes the following steps.

[0053] Data acquisition steps: Obtaining associated wellbore parameters based on well completion data, and using sonar cavity measurement technology to obtain multi-directional cavity parameters of the salt cavity;

[0054] The gas property analysis steps include using a matching data analysis platform to calculate the physical property parameters of carbon dioxide at different temperatures and pressures, and storing the physical property parameters of natural gas.

[0055] The simulation calculation steps involve establishing a physical simulation model of the salt cavern gas storage tank based on wellbore parameters and cavity parameters, solving the physical model according to the physical properties of carbon dioxide and the set boundary conditions, and determining the effective salt cavity temperature and pressure data; wherein the boundary conditions preferably use the gas injection rate and gas production rate data of the gas storage / hydrogen operation.

[0056] The gas storage parameter calculation steps, and the dynamic gas injection and production calculation model for the gas storage / hydrogen reservoir based on the salt cavity temperature and pressure data and the corresponding natural gas / hydrogen physical property parameters;

[0057] The steps for optimizing injection and production parameters include: simulating the mixing degree of carbon dioxide in the cushion gas by setting different boundary conditions; adjusting the injection and production boundary conditions based on the simulation results and the set mixing degree requirements, and using these as the target injection and production parameters.

[0058] Salt cavern gas / hydrogen storage is relatively deep, and the temperature and pressure inside the cavity will cause carbon dioxide to be in a supercritical state. In the supercritical state, the density and viscosity of carbon dioxide are much greater than those of natural gas / hydrogen. However, different degrees of gas mixing will also occur during the injection and production stages. The above embodiments of the present invention provide a strategy for simulating the degree of gas mixing in the cavity under different injection and production rates and adjusting the injection and production rates based on the simulation results.

[0059] Figure 3 This diagram illustrates the implementation principle of the computational decision-making method for using carbon dioxide as a gas storage in underground salt caverns / hydrogen reservoir cushion layer according to an embodiment of the present invention. Figure 3 As shown, in a preferred embodiment, the data acquisition step involves obtaining associated wellbore parameters based on the well completion design scheme data, including: the outer diameter of the completion string, the wall thickness of the completion string, the inner diameter of the completion string, the bottom depth of the completion string, the outer diameter of the injection / production string, the wall thickness and inner diameter of the injection / production string, and the bottom depth of the injection / production string.

[0060] In practical applications, wellbore parameters, cavity parameters, and gas / hydrogen storage operation parameters are obtained according to the following method, wherein the gas / hydrogen storage operation parameters are used as model boundary conditions.

[0061] Based on the well completion design scheme, obtain the outer diameter of the well completion string, the wall thickness of the well completion string, the inner diameter of the well completion string, the bottom depth of the well completion string, the outer diameter of the injection and production gas string, the wall thickness of the injection and production gas string, the inner diameter of the injection and production gas string, and the bottom depth of the injection and production gas string.

[0062] The shape, total volume, top depth, and bottom depth of the salt cavern are obtained using sonar cavity data. The sonar data includes measurement points, well depth, cross-sectional radius, cross-sectional area, depth range, segmented volume, and cumulative volume.

[0063] In a preferred embodiment, the data acquisition step, which involves acquiring multi-directional cavity parameters using sonar cavity measurement technology, includes:

[0064] Sonar cavity measurement technology is used to measure relevant sonar parameters, including measurement point, well depth, cross-sectional radius, cross-sectional area, depth range, segmented volume and cumulative volume;

[0065] Then, based on the analysis of relevant sonar parameters, the sonar cavity data is determined, including the shape of the salt cave, the total volume of the salt cave, the burial depth of the top of the salt cave, and the burial depth of the bottom of the salt cave.

[0066] Furthermore, the physical properties of carbon dioxide at different temperatures and pressures are calculated using a matching data analysis platform through gas property analysis steps, and the physical properties of natural gas / hydrogen are combined and stored.

[0067] In an optional embodiment, in the gas property analysis step, the set temperature and pressure data are imported into MATLAB, and MATLAB is used to calculate the real-time gas property parameters of carbon dioxide at different temperatures and pressures based on the carbon dioxide database; including: density, viscosity, thermal conductivity, isobaric heat capacity, and isocapacitive heat capacity of carbon dioxide at different temperatures and pressures.

[0068] In practical applications, the physical properties of carbon dioxide at specified temperatures and pressures are calculated based on a carbon dioxide database.

[0069] The specified temperature and pressure are imported into MATLAB. Real-time gas physical properties are calculated within MATLAB based on a carbon dioxide database. The density D, thermal conductivity L, isobaric heat capacity C, viscosity V, and isovolic heat capacity O of natural gas / hydrogen at different temperatures and pressures are as follows:

[0070] D(i,j)=py.COOLPROP.COOLPROP.PropsSI('D','T',T(i),'P',P(j),'CO2')

[0071] L(i,j)=py.COOLPROP.COOLPROP.PropsSI('L','T',T(i),'P',P(j),'CO2')

[0072] C(i,j)=py.COOLPROP.COOLPROP.PropsSI('C','T',T(i),'P',P(j),'CO2')

[0073] V(i,j)=py.COOLPROP.COOLPROP.PropsSI('V','T',T(i),'P',P(j),'CO2')

[0074] O(i,j)=py.COOLPROP.COOLPROP.PropsSI('O','T',T(i),'P',P(j),'CO2').

[0075] Where T represents temperature, P represents pressure, i represents the i-th count in the temperature cycle, j represents the j-th count in the pressure cycle, and CO2 represents carbon dioxide.

[0076] Furthermore, simulation calculation steps can be performed to establish a physical simulation model of the salt cavern gas / hydrogen reservoir based on wellbore parameters and cavity parameters. The physical model is then solved according to the physical properties of carbon dioxide and the set boundary conditions to determine the effective salt cavern temperature and pressure data.

[0077] In a preferred embodiment, the simulation calculation step involves establishing a physical simulation model of the salt cavern gas storage / hydrogen reservoir using a multiphysics simulation system, including:

[0078] The calculated carbon dioxide physical property parameters are imported into the multiphysics simulation system COMSOL. Combined with one or more preset boundary conditions, the physical simulation model of the salt cavern gas storage is used for simulation to obtain the corresponding real-time temperature and pressure data of the gas / hydrogen storage, which are used as the effective salt cavern temperature and pressure.

[0079] There are two ways to import the calculated carbon dioxide physical property parameters into the multiphysics simulation system COMSOL. The first is to use COMSOL WITH MATLAB. When COMSOL needs the physical property parameters at a certain temperature and pressure, it calls MATLAB to perform the calculation and returns the physical property parameters to COMSOL. The second is to generate a text document containing the carbon dioxide physical property parameters and then import it into COMSOL.

[0080] Next, the dynamic gas injection and production calculation model of the gas storage facility is determined based on the salt cavity temperature and pressure data and the corresponding natural gas / hydrogen physical properties, using the gas storage parameter calculation steps.

[0081] Based on the temperature and pressure within the salt chamber, and the physical properties under those pressure and temperature conditions, substitute them into the real gas law:

[0082] PV=nZRT (1)

[0083] Where P represents gas pressure, V represents gas volume, n represents gas molar mass, R is gas constant, T represents gas temperature, and Z represents gas compressibility factor.

[0084] The amount of natural gas / hydrogen in this state can be calculated. Further deformation of the real gas state yields:

[0085]

[0086] make Substituting into the above formula, we get:

[0087]

[0088] In the formula, G r This is the real-time storage capacity of natural gas / hydrogen, P. r T r Z r ρ r It represents the real-time pressure, temperature, compressibility factor, and density within the salt cavity; V is the volume of the salt cavity; and M is the volume of the salt cavity. g It represents the relative molecular mass of natural gas / hydrogen. In actual calculations, the dynamic salt cavity pressures Pr and Tr are obtained in advance using the injection-production rate boundary simulation, and then substituted into the formula for calculation. This allows us to obtain the corresponding calculation results based on the real influencing factors of the injection-production rate boundary.

[0089] Based on the maximum operating pressure and maximum operating temperature of the salt chamber, substituting them into the true equation of state for the gas, we can obtain:

[0090]

[0091] Based on the minimum operating pressure and minimum operating temperature of the salt chamber, we can obtain:

[0092]

[0093] The volume of the salt cavity that can be injected or extracted is calculated based on the data obtained from S5 and S6. When injecting gas, the injectable volume within the salt cavity is...

[0094] G in =G max -G r (6)

[0095] The recoverable gas volume is

[0096] G out =G r -G min (7)

[0097] in, G in It refers to the dynamic gas injection rate of the gas storage / hydrogen reservoir, G. out It is the active gas production rate of the gas storage / hydrogen reservoir, G r This is the real-time storage capacity of natural gas / hydrogen, P. r T r Z r ρ r These are the real-time pressure, temperature, compressibility factor, and density within the salt cavity, respectively; V is the volume of the salt cavity; and M is the density of the salt cavity. g It is the relative molecular mass of natural gas / hydrogen, G max This refers to the natural gas / hydrogen storage capacity at the maximum operating pressure and temperature of the salt chamber, G. min It represents the natural gas / hydrogen storage capacity at the minimum operating pressure and minimum operating temperature of the salt chamber.

[0098] Under different injection and production conditions, the temperature and pressure changes within the cavity, as well as the gas velocity, vary, resulting in different degrees of mixing between natural gas / hydrogen and carbon dioxide. Excessively rapid injection and production rates can increase the degree of mixing, and rapid changes in temperature and pressure within the cavity can also affect the physical properties of carbon dioxide, thus impacting the degree of mixing.

[0099] By setting different boundary conditions to simulate the degree of carbon dioxide disturbance in the cushion gas, the injection and production boundary conditions are adjusted according to the simulation results to ensure that the degree of gas mixing under injection and production conditions is within an acceptable range.

[0100] Furthermore, preferably, in one embodiment, the degree of mixing of different gases is represented by gas concentration. Therefore, the injection and production parameter optimization step is performed by setting different gas concentration boundary conditions to simulate the degree of mixing of carbon dioxide in the cushion gas. The injection and production boundary conditions are adjusted according to the simulation results and the set degree of mixing requirements as the target injection and production parameters.

[0101] In a preferred embodiment, in the step of optimizing injection and production parameters, different gas injection rate boundary conditions and gas production rate boundary conditions are set for different effective salt cavity temperatures and pressures. The gas storage operation process is simulated using a simulation physical model to analyze the mixing of carbon dioxide in the cushion gas and to determine the gas injection rate and gas production rate that meet the process requirements.

[0102] In an optional embodiment, the degree of gas mixing in the simulation results can be compared with the set conditions. If the requirements are not met, the injection and production boundary parameters are adjusted to re-simulate the degree of gas mixing of carbon dioxide in the cushion gas until the simulated degree of gas mixing meets the set requirements. The injection and production boundary parameters corresponding to different temperature and pressure data are associated and recorded as a list of gas storage / hydrogen reservoir injection and production parameters, providing implementation assistance for the actual gas storage operation of carbon dioxide as underground gas storage / hydrogen reservoir cushion gas.

[0103] The embodiments of this invention can be used for operational guidance of carbon dioxide as a cushion gas in underground gas storage / hydrogen reservoirs. It can accurately model the operational status of gas storage / hydrogen reservoirs using carbon dioxide as cushion gas, and can calculate the injectable gas volume and the mixing degree of carbon dioxide cushion gas at different injection and extraction rates in real time. It can be used for field injection and extraction in gas storage / hydrogen reservoirs.

[0104] This invention can simulate the gas mixing degree of the cushion layer gas in a salt cavern gas / hydrogen storage reservoir under different injection or production rates, and the temperature and pressure changes within the reservoir during injection and production. It then combines these simulations with a carbon dioxide database to calculate the dynamic gas storage capacity. In addition to fluid analysis, it can further perform solid mechanics analysis based on the simulation results of gas flow and temperature changes, conducting mechanical analysis of the surrounding rock, especially the casing shoe, to ensure the stability of the gas / hydrogen storage reservoir during injection and production. The calculation steps are clearly defined and can meet practical engineering requirements.

[0105] Taking a certain salt cavern gas storage facility as an example, the cavity volume is 260,000 m³. 3 The operating temperature is 47℃ and the operating pressure is 6MPa-17MPa. The compressibility factors of carbon dioxide and natural gas at different temperatures and pressures calculated in MATLAB are shown in the table below.

[0106]

[0107] If carbon dioxide is used as the cushion gas, at the lower operating pressure of 6 MPa, the volume of carbon dioxide in the gas storage facility under standard ground conditions is:

[0108]

[0109] If natural gas is used as the cushion gas, at the lower operating pressure of 6 MPa, the volume of natural gas in the gas storage facility under standard ground conditions is:

[0110]

[0111] At the upper operating pressure of 17 MPa, the volume of carbon dioxide cushion gas in the salt chamber of the gas storage facility is:

[0112]

[0113] At the upper operating pressure of 17 MPa, the volume of natural gas in the salt chamber of the gas storage facility is:

[0114] V = 26 × 10 4 -4.74×10 4 =21.26×10 4 m 3 (11)

[0115] If carbon dioxide is used as the cushion gas, at the upper working pressure limit of 17 MPa, the volume of natural gas / hydrogen in the gas storage facility under standard conditions is:

[0116]

[0117] If natural gas is used as the cushion gas, at the upper working pressure limit of 17 MPa, the volume of natural gas in the gas storage facility under standard ground conditions is:

[0118]

[0119] If carbon dioxide is used as the cushion gas, the working gas volume of the gas storage facility, which can be the gas extraction volume, is:

[0120]

[0121] If natural gas is used as the cushion gas, the working gas volume of the gas storage facility, which can be harvested, is:

[0122]

[0123] This shows that, under the same gas storage conditions, using carbon dioxide as the cushion gas can result in a larger volume of gas injected and extracted.

[0124] For the foregoing method embodiments, in order to simplify the description, they are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0125] It should be noted that, in other embodiments of the present invention, the method can also combine one or more of the above embodiments to obtain a new computational decision-making method for using carbon dioxide as a cushion gas in underground salt cavern gas storage / hydrogen storage, so as to achieve precise optimization and development support for the process of using carbon dioxide as a cushion gas in underground salt cavern gas storage.

[0126] It should be noted that, based on the methods in any one or more embodiments of the present invention described above, the present invention also provides a storage medium storing program code that can implement the methods described in any one or more embodiments. When the program code is executed by the operating system, it can implement the calculation method for using carbon dioxide as underground salt cavern gas storage / hydrogen reservoir cushion gas as described above.

[0127] Example 2:

[0128] The methods described in the above-disclosed embodiments of the present invention are detailed. These methods can be implemented using various forms of devices or systems. Therefore, based on other aspects of the methods described in any one or more of the above embodiments, the present invention also provides a computational system for using carbon dioxide as underground salt cavern gas storage / hydrogen reservoir cushion gas. This system is used to execute the computational method for using carbon dioxide as underground salt cavern gas storage / hydrogen reservoir cushion gas as described in any one or more of the above embodiments. Specific embodiments are given below for detailed description.

[0129] Specifically, Figure 4 The diagram shows a schematic representation of the computational system for using carbon dioxide as a gas storage layer in underground salt caverns / hydrogen reservoirs, as provided in an embodiment of the present invention. Figure 4 As shown, the system includes:

[0130] The data acquisition module is configured to acquire associated wellbore parameters based on well completion data and to acquire multi-directional cavity parameters of the salt cavity using sonar cavity measurement technology.

[0131] The gas property analysis module is configured to use a matching data analysis platform to calculate the physical property parameters of carbon dioxide at different temperatures and pressures, and to store the physical property parameters of natural gas / hydrogen.

[0132] The simulation module is configured to establish a physical simulation model of the salt cavern gas storage tank based on wellbore parameters and cavity parameters. It solves the physical model according to the physical properties of carbon dioxide and the set boundary conditions to determine the effective salt cavern temperature and pressure data.

[0133] The gas storage parameter calculation module is configured to determine the dynamic gas injection and production calculation model of the gas storage / hydrogen reservoir based on the temperature and pressure data of the salt chamber and the corresponding natural gas / hydrogen physical property parameters.

[0134] The injection and production parameter optimization module is configured to simulate the mixing degree of carbon dioxide in the cushion gas by setting different boundary conditions, and adjust the injection and production boundary conditions according to the simulation results and the set mixing degree requirements as the target injection and production parameters.

[0135] Preferably, in one embodiment, the data acquisition module is configured to use sonar cavity measurement technology to measure relevant sonar parameters as multi-directional cavity parameters, including measurement point, well depth, cross-sectional radius, cross-sectional area, depth range, segmented volume and cumulative volume.

[0136] Then, based on the analysis of relevant sonar parameters, the sonar cavity data is determined, including the shape of the salt cave, the total volume of the salt cave, the burial depth of the top of the salt cave, and the burial depth of the bottom of the salt cave.

[0137] Furthermore, in one embodiment, the gas property analysis module is configured to: import the set temperature and pressure data into MATLAB, and use MATLAB based on a carbon dioxide database to calculate the real-time gas property parameters of carbon dioxide at different temperatures and pressures.

[0138] Optionally, in one embodiment, the simulation calculation module is configured to perform the following operations:

[0139] The calculated carbon dioxide physical property parameters are imported into a multiphysics simulation system. Combined with one or more preset boundary conditions, the physical simulation model of the salt cavern gas / hydrogen reservoir is used for simulation to obtain the corresponding real-time temperature and pressure data of the gas / hydrogen reservoir, which are used as the effective salt cavern temperature and pressure.

[0140] Furthermore, in an optional embodiment, the gas storage parameter calculation module determines the dynamic gas injection volume calculation model of the gas storage tank according to the following formula:

[0141] G in =G max -G r

[0142] Determine the dynamic gas extraction calculation model for the gas storage / hydrogen reservoir as described in the following formula.

[0143] G out =G r -G min

[0144] in, G in It refers to the dynamic gas injection rate of the gas storage / hydrogen reservoir, G. out It is the active gas production rate of the gas storage / hydrogen reservoir, G r This is the real-time storage capacity of natural gas / hydrogen, P. r T r Z r ρ r These are the real-time pressure, temperature, compressibility factor, and density within the salt cavity, respectively; V is the volume of the salt cavity; and M is the density of the salt cavity. g It is the relative molecular mass of natural gas / hydrogen, G max This refers to the natural gas / hydrogen storage capacity at the maximum operating pressure and temperature of the salt chamber, G. min It represents the natural gas / hydrogen storage capacity at the minimum operating pressure and minimum operating temperature of the salt chamber.

[0145] In a preferred embodiment, the injection and production parameter optimization module is configured to: set different gas injection rate boundary conditions and gas production rate boundary conditions for different effective salt cavity temperatures and pressures, simulate the gas storage operation process using a simulation physical model, analyze the mixing of carbon dioxide in the cushion gas, and decide on the gas injection rate and gas production rate that meet the process requirements.

[0146] Furthermore, in an optional embodiment, the simulation calculation module is specifically configured to import the calculated carbon dioxide physical property parameters into the multiphysics simulation system using MATLAB invocation, calling MATLAB to perform calculations with temperature and pressure data as labels, and returning the physical property parameters to the multiphysics simulation system.

[0147] Specifically, in a preferred embodiment, the simulation calculation module is configured to import the calculated carbon dioxide physical property parameters into the multiphysics simulation system by generating a text document of the carbon dioxide physical property parameters and directly importing it into the multiphysics simulation system.

[0148] In the computational system for using carbon dioxide as underground salt cavern gas storage / hydrogen reservoir cushion gas provided in this embodiment of the invention, each module or unit structure can operate independently or in combination according to actual data setting requirements and simulation computation requirements to achieve the corresponding technical effects.

[0149] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should be extended to equivalent substitutions of these features as understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0150] The phrase "an embodiment" in the specification means that a specific feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, the phrase "an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0151] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and variations in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection for this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A calculation method for using carbon dioxide as a gas storage layer in underground salt caverns / hydrogen reservoirs, characterized in that, The method includes: Data acquisition steps: Obtain relevant wellbore parameters based on well completion data, and use sonar cavity measurement technology to obtain multi-directional cavity parameters of the salt cavity; Gas property analysis steps: Calculate the physical property parameters of carbon dioxide at different temperatures and pressures using a matching data analysis platform, and store the combined physical property parameters of natural gas and hydrogen; The simulation calculation steps are as follows: a physical simulation model of the salt cavern gas storage is established based on wellbore parameters and cavity parameters; the physical model is solved according to the physical property parameters of carbon dioxide and the set boundary conditions to determine the effective salt cavity temperature and pressure data. Gas storage parameter calculation steps: Based on the salt chamber temperature and pressure data and the corresponding natural gas / hydrogen physical property parameters, determine the dynamic gas injection and production calculation model for the gas storage / hydrogen reservoir; Injection and production parameter optimization steps: Simulate the mixing degree of carbon dioxide in the cushion gas by setting different boundary conditions, and adjust the injection and production boundary conditions according to the simulation results and the set mixing degree requirements as the target injection and production parameters.

2. The method according to claim 1, characterized in that, In the data acquisition step, the process of obtaining multi-directional cavity parameters using sonar cavity measurement technology includes: Sonar cavity measurement technology is used to measure relevant sonar parameters, including measurement point, well depth, cross-sectional radius, cross-sectional area, depth range, segmented volume and cumulative volume; Then, based on the analysis of relevant sonar parameters, the sonar cavity data is determined, including the shape of the salt cave, the total volume of the salt cave, the burial depth of the top of the salt cave, and the burial depth of the bottom of the salt cave.

3. The method according to claim 1, characterized in that, In the gas property analysis step, the set temperature and pressure data are imported into MATLAB, and MATLAB is used to calculate the real-time gas property parameters of carbon dioxide at different temperatures and pressures based on the carbon dioxide database.

4. The method according to claim 1, characterized in that, The simulation calculation steps include: The calculated carbon dioxide physical property parameters are imported into a multiphysics simulation system. Combined with one or more preset boundary conditions, the physical simulation model of the salt cavern gas / hydrogen reservoir is used for simulation to obtain the corresponding real-time temperature and pressure data of the gas / hydrogen reservoir, which are used as the effective salt cavern temperature and pressure.

5. The method according to claim 1, characterized in that, In the gas storage parameter calculation steps, the dynamic gas injection volume calculation model of the gas storage tank is determined by the following formula: Determine the dynamic gas extraction calculation model for the gas storage / hydrogen reservoir as described in the following formula: in, G in It refers to the dynamic gas injection rate of the gas storage / hydrogen reservoir, G. out It is the dynamic gas production volume of the gas storage / hydrogen reservoir, G r This is the real-time storage capacity of natural gas / hydrogen, P. r T r Z r ρ r These are the real-time pressure, temperature, compressibility factor, and density within the salt cavity, respectively; V is the volume of the salt cavity; and M is the density of the salt cavity. g It is the relative molecular mass of natural gas / hydrogen, G max This refers to the natural gas / hydrogen storage capacity at the maximum operating pressure and temperature of the salt chamber, G. min It represents the natural gas / hydrogen storage capacity at the minimum operating pressure and minimum operating temperature of the salt chamber, where R represents the gas constant.

6. The method according to claim 1, characterized in that, In the step of optimizing injection and production parameters, different gas injection rate boundary conditions and gas production rate boundary conditions are set for different effective salt cavity temperatures and pressures. The gas storage operation process is simulated using a simulation physical model to analyze the mixing of carbon dioxide in the cushion gas and to determine the gas injection rate and gas production rate that meet the process requirements.

7. The method according to claim 1, characterized in that, In the simulation calculation process, the process of importing the calculated carbon dioxide physical property parameters into the multiphysics simulation system is carried out by calling MATLAB. The temperature and pressure data are used as labels to call MATLAB for calculation, and the physical property parameters are returned to the multiphysics simulation system.

8. The method according to claim 1, characterized in that, In the simulation calculation steps, the process of importing the calculated carbon dioxide physical property parameters into the multiphysics simulation system is to generate a text document of the carbon dioxide physical property parameters and directly import it into the multiphysics simulation system.

9. A storage medium, characterized in that, The storage medium stores program code capable of implementing the method as described in any one of claims 1 to 8.

10. A computational system for using carbon dioxide as a gas storage layer in underground salt caverns / hydrogen reservoirs, characterized in that, The system performs the method as described in any one of claims 1 to 8.

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