Carbon dioxide replacement hydrate exploitation and geological sequestration numerical simulation method and system and readable medium

Abstract

The invention belongs to the technical field of hydrate exploitation, and relates to a carbon dioxide replacement hydrate exploitation and geological sequestration numerical simulation method which comprises the following steps: establishing a natural gas hydrate generation and decomposition kinetic model; establishing a CH4 and CO2 natural gas hydrate mass conservation equation, an energy conservation equation, a relative permeability model, a porosity and permeability relation and a reaction equilibrium value calculation model; establishing a heat-flow-force-chemical multi-field coupling natural gas hydrate replacement exploitation and storage mathematical model; and analyzing the mining and geological sequestration characteristics of the carbon dioxide replacement hydrate in combination with the model. The method is used for coupling carbon dioxide replacement hydrate exploitation and geological sequestration processes and accurately predicting the influence of different parameters on CH4 production and CO2 sequestration.

Description

Technical Field

[0001] This invention relates to a numerical simulation method, system, and readable medium for the extraction and geological storage of carbon dioxide displacement hydrates, belonging to the field of hydrate extraction technology. Background Technology

[0002] With the continuous development of science and technology, human society's demand for energy is constantly increasing, and the development of natural gas hydrates is of great significance in alleviating the severe situation of energy depletion. In recent years, hydrate trial production work has been carried out successively in terrestrial permafrost and marine areas. With the improvement of engineering technology, both the trial production time and gas production have been significantly increased. However, when solid hydrates depressurize and decompose, the mechanical properties of the reservoir will change. Improper development methods of natural gas hydrate reservoirs may cause serious environmental and geological disasters. Compared with other traditional methods, the CO2 replacement method utilizes the difference in phase equilibrium between CO2 hydrates and CH4 hydrates. By injecting CO2 into the hydrate reservoir, methane is obtained and CO2 hydrates are regenerated, maintaining the mechanical stability of the reservoir and thus reducing damage to the formation medium.

[0003] In recent years, CO2 capture, utilization, and storage (CCUS) technology has been considered a highly promising method for reducing CO2 emissions, and scholars from various countries have conducted extensive research on this technology. Geological utilization and storage of CO2 is a crucial component of CCUS technology. Currently, my country has made significant progress from "exploratory pilot production" to "experimental pilot production" in order to industrialize natural gas hydrates. However, there is still a gap to bridge before achieving commercial production capacity, and CO2 sequestration in deep-sea sediments is still in the early stages of theoretical research and simulation experiments. Many challenges remain in achieving the goal of CO2 replacement mining and storage of natural gas hydrates in marine areas. The CO2 replacement mining and storage process of natural gas hydrates involves four coupled physicochemical processes: heat transfer (temperature field T), multiphase seepage (seepage field H), formation deformation (mechanical field M), and hydrate decomposition and formation (chemical field C). The multiphase, multi-component, and multi-field coupled seepage characteristics accompanying phase changes have become a significant challenge in hydrate research. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a numerical simulation method, system, and readable medium for carbon dioxide replacement hydrate extraction and geological storage, which can accurately predict the hydrate extraction and carbon dioxide storage process under multi-field coupling conditions and can simulate and analyze the dynamics of large-scale hydrate reservoirs.

[0005] To achieve the above objectives, this invention proposes the following technical solution: a numerical simulation method for the exploitation and geological storage of carbon dioxide replacement hydrates, comprising the following steps: establishing a kinetic model for the formation and decomposition of natural gas hydrates; establishing mass conservation equations, energy conservation equations, relative permeability models, porosity-permeability relationships, and reaction equilibrium value calculation models for CH4 and CO2 natural gas hydrates; establishing a multi-field coupled mathematical model for the exploitation and storage of natural gas hydrates using a thermo-fluid-mechanical-chemical approach; combining the kinetic model for the formation and decomposition of natural gas hydrates, the mass conservation equations, energy conservation equations, relative permeability models, porosity-permeability relationships, and reaction equilibrium value calculation models to form a multi-field coupled mathematical model for the exploitation and storage of natural gas hydrates using a thermo-fluid-mechanical-chemical approach; numerically solving the mathematical model to obtain pressure, temperature, hydrate concentration, and strain values ​​at different times and spaces; and analyzing the characteristics of the exploitation and geological storage of carbon dioxide replacement hydrates.

[0006] Furthermore, the calculation formula for the natural gas hydrate formation kinetic model is as follows:

[0007] Among them, among them, It is the concentration of hydrates formed. It is time. It is the surface area of ​​the spherical particles that make up hydrates in a porous medium. It is the density of water. It is porosity. It is the water saturation in porous media. It is the hydrate saturation in porous media. Here, E is the equilibrium pressure, E is the activation energy of the reaction, R is the gas constant, and T is the temperature. It is the equilibrium value of hydrates under certain pressure and temperature.

[0008] Furthermore, the calculation formula for the natural gas hydrate formation kinetic model is as follows:

[0009] in, It is the concentration of decomposed hydrates. It is the frequency factor of hydrate decomposition reaction. It is the density of hydrates.

[0010] Furthermore, the mass conservation equation for the natural gas hydrate is: Gas phase CO2:

[0011] Gas phase CH4:

[0012] Liquid phase:

[0013] Solid CO2 hydrate:

[0014] Solid CH4 hydrate:

[0015] in, It is the density of carbon dioxide. It refers to the saturation level of carbon dioxide. It is the volumetric flow rate of carbon dioxide. It is the mass of carbon dioxide. It is a source and sink phase of carbon dioxide. It is the density of methane. It is the saturation level of methane. It is the volumetric flow rate of methane. yes quality It is a methane source-sink phase. It is the volumetric flow rate of the aqueous phase. It is the mass of the aqueous phase. It is a water phase source and confluence phase.

[0016] Furthermore, the mass conservation equation for the natural gas hydrate is:

[0017] in, It is the effective thermal conductivity. It is the density of the gas. It is the relative volumetric velocity of the gas phase. It is vapor phase enthalpy. It is the relative volumetric velocity of the water phase. It is the enthalpy of the aqueous phase. It is the heat required for the formation or decomposition of hydrates. It is the density of the rock skeleton. It refers to the saturation of hydrates. It is the enthalpy of the rock skeleton. It is the density of the hydrate. It is the enthalpy of hydrate. It refers to the saturation of the aqueous phase. It refers to the saturation of the gas phase.

[0018] Furthermore, the relative penetration rate model is:

[0019]

[0020]

[0021] in:

[0022]

[0023] in, It is the relative permeability of the aqueous phase. It is the relative permeability of the gas phase. It is bound water saturation. It is the residual gas saturation. , All are power-law coefficients. For capillary pressure, The initial capillary pressure, It is the VanGenuchten index; Furthermore, the relative penetration rate model is:

[0024] Where K is the equilibrium value of the reaction. , , , and These are all fitted parameters. This is the current gas phase pressure.

[0025] Furthermore, the mathematical model for the thermal-fluid-mechanical-chemical multi-field coupled natural gas hydrate replacement exploitation and storage is as follows:

[0026] in, It is the original porosity of the reservoir considering the deformation of the medium. It is fluid density. It is the internal energy of the fluid phase. It is the density of solid particles. It is the internal energy of the rock phase. It's viscosity. It's pressure, in kPa. It is a volume force. It is the enthalpy of fluid. It is thermal conductivity. It is external heat.

[0027] This invention also discloses a numerical simulation system for the exploitation and geological storage of carbon dioxide replacement hydrates, comprising: a kinetic model establishment module for establishing a kinetic model of natural gas hydrate formation and decomposition; a natural gas hydrate reaction-related model establishment module for establishing the mass conservation equation, energy conservation equation, relative permeability model, porosity-permeability relationship, and reaction equilibrium value calculation model for CH4 and CO2 natural gas hydrates; a multi-field coupling model establishment module for establishing a thermal-fluid-mechanical-chemical multi-field coupled mathematical model for the exploitation and storage of natural gas hydrates; and a model fusion module for combining the natural gas hydrate formation and decomposition kinetic model, the CH4 and CO2 natural gas hydrate mass conservation equation, energy conservation equation, relative permeability model, porosity-permeability relationship, and reaction equilibrium value calculation model, and the thermal-fluid-mechanical-chemical multi-field coupled mathematical model for the exploitation and storage of natural gas hydrates to analyze the characteristics of carbon dioxide replacement hydrate exploitation and geological storage.

[0028] The present invention also discloses a computer-readable storage medium storing a computer program, which is executed by a processor to implement the numerical simulation method for carbon dioxide replacement hydrate mining and geological storage as described in any of the preceding claims.

[0029] The technical solution of the present invention has at least the following technical effects or advantages: it is difficult to adapt to complex multi-field coupling in the prior art, it clarifies the physical and chemical processes of mutual coupling of the four fields of heat, fluid, force and chemistry, it can accurately predict the hydrate mining and carbon dioxide storage process under multi-field coupling conditions, and it can simulate and analyze the dynamics of large-scale hydrate reservoirs. Attached Figure Description

[0030] Figure 1 This is a flowchart of the numerical simulation solution for CO2 replacement extraction and storage of natural gas hydrate in one embodiment of the present invention; Figure 2 This is a schematic diagram of a reservoir in a numerical simulation of natural gas hydrate depressurization extraction and CO2 replacement extraction according to an embodiment of the present invention; Figure 3 This is a numerical simulation result of the cumulative gas production and gas production rate of pressure drop mining and replacement mining in one embodiment of the present invention. Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention is described in detail through specific embodiments. However, it should be understood that the specific embodiments are provided only for a better understanding of the present invention and should not be construed as limiting the present invention. In the description of the present invention, it should be understood that the terminology used is for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] To address the lack of research on the multiphase, multicomponent, and multi-field coupled seepage characteristics associated with phase transitions in existing technologies, this invention proposes a numerical simulation method, system, and readable medium for the exploitation and geological storage of carbon dioxide replacement hydrates. This includes: establishing kinetic models for the formation and decomposition of CH4 and CO2 natural gas hydrates; establishing mass conservation equations, energy conservation equations, relative permeability models, porosity-permeability relationships, and reaction equilibrium calculation models for CH4 and CO2 natural gas hydrates; establishing a multi-field coupled mathematical model for the exploitation and storage of natural gas hydrates based on thermo-fluid-mechanical-chemical fields; and solving the multi-field coupled numerical simulation model to analyze the mechanism of carbon dioxide replacement hydrate exploitation and geological storage. This invention analyzes the physicochemical characteristics based on the mutual coupling of thermo-fluid-mechanical-chemical fields, and establishes a multi-field coupled numerical simulation method and system for coupling the exploitation and geological storage processes of carbon dioxide replacement hydrates, accurately predicting the impact of different parameters on CH4 production and CO2 storage. The invention is described in detail below with reference to the accompanying drawings.

[0033] Example 1 This embodiment discloses a numerical simulation method for the extraction and geological storage of carbon dioxide replacement hydrates, including the following steps: S1 establishes a kinetic model for the formation and decomposition of natural gas hydrates.

[0034] The kinetic model for the formation and decomposition of natural gas hydrates satisfies the following conditions: the kinetic model consists of three phases: an aqueous phase, a gas phase, and a hydrate phase, with the hydrate phase being the solid phase; the kinetic model can be set as three-phase or five-phase, with the three components being CO2, water, and CO2 hydrate, or the five components being water, CO2, CO2 hydrate, CH4, and CH4 hydrate. The flow of the aqueous and gas phases in the porous medium conforms to Darcy's law of permeability; the solubility of CO2 and CH4 gases in water and the volatility of water are not considered; hydrates begin to decompose when the pressure is below or the temperature is above the equilibrium condition; hydrates begin to form when the pressure is above or the temperature is below the equilibrium condition; the formation and decomposition of hydrates lead to changes in formation porosity; the velocity of the solid hydrate relative to the reservoir is 0.

[0035] In this embodiment, the Kim-Bishnoi model is used to describe the kinetics of hydrate formation, which can be expressed as:

[0036] in, It is the concentration of hydrates formed, mol·m -3 , It is time. It is the hydrate formation rate constant, mol·m -2 ·Pa -1 ·s -1 , It is the specific surface area of ​​hydrate formation, which can represent the effective contact area between the hydrate and the fluid, in meters (m). 2 ·m -3 ; This is the current gas phase pressure, in Pa; It is the balancing pressure, Pa.

[0037] Rate constant of hydrate formation The calculation formula is:

[0038] in, The frequency factor for hydrate formation reaction, mol·m -2 ·Pa -1 ·s -1 .

[0039] When hydrates are at saturation When present in porous media, hydrates have a surface area of If the composition is spherical particles, then the specific surface area of ​​hydrate formation per unit volume is:

[0040] The calculation formula for the natural gas hydrate formation kinetic model is as follows:

[0041] in, It is the surface area of ​​the spherical particles that make up hydrates in a porous medium, m 2 ·m -3 , It is the density of water. It is porosity. It is the water saturation in porous media. It is the hydrate saturation in the porous medium, and E is the activation energy of the reaction, J·mol⁻¹. -1 R is the gas constant, with a value of 8.314 J·mol⁻¹. -1 ·K -1 T is temperature, K. It is the equilibrium value of hydrates under certain pressure and temperature, equal to .

[0042] The kinetics of hydrate decomposition reactions can be described as follows:

[0043] in, It is the concentration of decomposed hydrates, mol·m -3 , It is the rate constant of hydrate decomposition, mol·m -2 ·Pa-1 ·s -1 , It is the specific surface area of ​​hydrate decomposition, in m 2 ·m -3 .

[0044] Rate constant of hydrate decomposition The calculation formula is:

[0045] When hydrates are at saturation When present in porous media, hydrates have a surface area of If the hydrate is composed of spherical particles, then the specific surface area of ​​the hydrate per unit volume is:

[0046] The calculation formula for the natural gas hydrate formation kinetic model is as follows:

[0047] in, It is the concentration of decomposed hydrates. It is the frequency factor of hydrate decomposition reaction, mol·m -2 ·Pa -1 ·s -1 , It is the density of the hydrate, kg·m -3 .

[0048] S2 establishes the mass conservation equation, energy conservation equation, relative permeability model, porosity-permeability relationship, and reaction equilibrium value calculation model for CH4 and CO2 natural gas hydrates.

[0049] In numerical simulations, the smallest discrete element is the control volume element. The formation and decomposition of hydrates obey the law of conservation of mass, and the fundamental equation of this conservation law can be expressed as:

[0050] in, It controls the amount of substance in a volume unit. It controls the inflow and outflow of substances within a volume unit. This is due to changes in the quantity of matter caused by injection, production, or decomposition.

[0051] Therefore, the mass conservation equation for natural gas hydrates is: Gas phase CO2:

[0052] Gas phase CH4:

[0053] Liquid phase:

[0054] Solid CO2 hydrate:

[0055] Solid CH4 hydrate:

[0056] in, It is the density of carbon dioxide. It refers to the saturation level of carbon dioxide. It is the volumetric flow rate of carbon dioxide. It is the mass of carbon dioxide. It refers to the amount of carbon dioxide injected or produced. It is the density of methane. It is the saturation level of methane. It is the volumetric flow rate of methane. yes quality It is a methane source-sink phase. It is the volumetric flow rate of the aqueous phase. It is the mass of the aqueous phase. It is a water phase source and confluence phase.

[0057] The mass conservation equation for natural gas hydrates is: The mass conservation equation for natural gas hydrates is:

[0058] in, It is the effective thermal conductivity. It is the density of the gas. It is the relative volumetric velocity of the gas phase. It is vapor phase enthalpy. It is the relative volumetric velocity of the water phase. It is the enthalpy of the aqueous phase. It is the heat required for the formation or decomposition of hydrates. It is the density of the rock skeleton. It refers to the saturation of hydrates. It is the enthalpy of the rock skeleton. It is the density of the hydrate. It is the enthalpy of hydrate. It refers to the saturation of the aqueous phase. It refers to the saturation of the gas phase.

[0059] The relative penetration model is:

[0060]

[0061]

[0062] in:

[0063]

[0064] in, It is the relative permeability of the aqueous phase. It is the relative permeability of the gas phase. It is bound water saturation. It is the residual gas saturation. , All are power-law coefficients. For capillary pressure, The initial capillary pressure, It is the VanGenuchten index; The effective thermal conductivity is calculated using the volume average method:

[0065] in, It is the thermal conductivity of the rock skeleton, J·m -1 ·s -1 ·K -1 , It is the thermal conductivity of hydrates. It is the thermal conductivity of the gas phase. It is the thermal conductivity of the aqueous phase.

[0066] During the formation or decomposition of hydrates, the porosity of the reservoir changes first, leading to a corresponding change in the effective permeability. There is a dynamic relationship between effective permeability and porosity. Based on the Carmen-Kozeny model, the relationship between porosity and permeability is as follows:

[0067] in, It is the effective penetration rate. It is the initial permeability of the formation. It is the initial porosity of the formation; It is a penetration rate decline index.

[0068] The stability or equilibrium of gas hydrates in porous media depends primarily on pressure, temperature, the composition of the coexisting phases, and sediment characteristics. Therefore, in this embodiment, the phase equilibrium of the hydrate is determined based on the K value, which is obtained from measured three-phase equilibrium data of pressure and temperature using thermodynamic models such as the Peng-Robinson equation of state (PR-EOS). Specifically, the permeability model is as follows:

[0069] Where K is the reaction equilibrium value, controlling the activation of the hydrate formation and decomposition reactions. Decomposition of hydrates, Hydrates are formed at this time; , , , and These are all fitting parameters.

[0070] S3 establishes a mathematical model for the thermal-fluid-mechanical-chemical multi-field coupled extraction and storage of natural gas hydrates through replacement.

[0071] The calculations in the geomechanics module are primarily based on three key parameters: stress, strain, and displacement. The equilibrium equations can be expressed as follows:

[0072] in, It is the total stress tensor, in kPa.

[0073] The relationship between effective stress and stress:

[0074] in,

[0075] in, It is the effective stress; It refers to the stresses other than thermal stress in the total stress. It is the Biot number, a factor used to describe the form of fluid-structure interaction; It is the identity matrix; It is thermal stress.

[0076] The mathematical model for the thermal-fluid-mechanical-chemical multi-field coupled extraction and storage of natural gas hydrates is:

[0077] in, It is the original porosity of the reservoir considering the deformation of the medium. It is fluid density. It is the internal energy of the fluid phase. It is the density of solid particles. It is the internal energy of the rock phase. It's viscosity. It's pressure, in kPa. It is a volume force. It is the enthalpy of fluid. It is thermal conductivity. It is external heat.

[0078] S4 combines the kinetic model of natural gas hydrate formation and decomposition, the mass conservation equations and energy conservation equations of CH4 and CO2 natural gas hydrates, the relative permeability model, the porosity-permeability relationship and reaction equilibrium value calculation model, and the thermo-fluid-mechanical-chemical multi-field coupled mathematical model of natural gas hydrate replacement mining and storage to analyze the characteristics of carbon dioxide replacement hydrate mining and geological storage.

[0079] An iterative coupled solution is used to solve the kinetic model of natural gas hydrate formation and decomposition, the mass conservation equations and energy conservation equations of CH4 and CO2 natural gas hydrates, the relative permeability model, the porosity-permeability relationship and reaction equilibrium value calculation model, and the thermo-fluid-mechanical-chemical multi-field coupled mathematical model of natural gas hydrate replacement exploitation and storage. The geomechanical calculation is not performed simultaneously with reservoir flow, but one time step later. The reservoir simulation and the calculation in the geomechanical module exchange information with each other. The reservoir flow is simultaneously affected by the geomechanical response. The solution is used to analyze the exploitation and geological storage characteristics of carbon dioxide replacement hydrates.

[0080] Example 2 Based on the same inventive concept, this embodiment discloses a numerical simulation system for carbon dioxide replacement hydrate extraction and geological storage, including: The kinetic model building module is used to build kinetic models for the formation and decomposition of natural gas hydrates; The module for establishing reaction-related models of natural gas hydrates is used to establish the mass conservation equation, energy conservation equation, relative permeability model, porosity-permeability relationship, and reaction equilibrium value calculation model for CH4 and CO2 natural gas hydrates. The multi-field coupling model establishment module is used to establish a mathematical model for the thermal-fluid-mechanical-chemical multi-field coupling of natural gas hydrate replacement extraction and storage; The model fusion module combines the kinetics model of natural gas hydrate formation and decomposition, the mass conservation equations and energy conservation equations for CH4 and CO2 natural gas hydrates, the relative permeability model, the porosity-permeability relationship and reaction equilibrium calculation model, and the thermo-fluid-mechanical-chemical multi-field coupled mathematical model of natural gas hydrate replacement exploitation and storage. It analyzes the characteristics of carbon dioxide replacement hydrate exploitation and geological storage. The numerical simulation solution process is as follows: Figure 1 , where n is the time step.

[0081] Example 3 This embodiment compares the numerical simulation results of gas production from natural gas hydrate depressurization extraction and CO2 replacement extraction. A reservoir model based on the original hydrate reservoir at the GMGS2-8 site is established in this embodiment. Figure 2 The model is 560 m long, 560 m wide, and 105 m high, with a grid of 28 × 28 × 26. The model consists of an impermeable overlying layer and an underlying overlying layer (water layer), discretized into 1 and 13 layers respectively. In the middle are three hydrate layers with different hydrate saturation levels, discretized into 2, 1, and 7 layers respectively. Other basic geological parameters are shown in Table 1, and the kinetic parameters of CO2 hydrate formation and decomposition are shown in Table 2. Numerical simulations were performed to solve for parameters such as pressure, temperature, hydrate concentration, and strain at each time step.

[0082] Table 1. Geological parameters of each foundation layer

[0083] The model includes an injection well for CO2 injection and a production well for depressurization of the hydrates, producing free water vapor. The production well penetrates the hydrate layer 3, maintaining a minimum bottomhole pressure of 4000 kPa. An injection well is located 300 m away from the production well. Once the formation pressure drops to 6000 kPa, CO2 is injected into the reservoir to restore formation pressure at an injection rate of 1000 m / s. 3 ·d -1 The injection temperature is 10 ℃ to ensure that hydrates do not clog the wellbore.

[0084] Table 2 Kinetic parameters of hydrate formation and decomposition

[0085] As a control, the injection wells in the model were shut down to simulate the depressurization characteristics of natural gas extraction in GMGS2-8, and compared with the CO2 replacement extraction case. Figure 3 This section compares the cumulative gas production and production rate of the two methods. Because the reservoir conditions do not contain free natural gas, the gas production rate is extremely low during the initial depressurization phase of production wells. During depressurization, the decomposition of solid hydrates takes time; as pressure propagates, hydrates decompose over a wider area, and CH4 gas is also dissociated, leading to a continuous increase in the gas production rate. The gas production rate increased steadily over the first three years, reaching its peak at approximately 1155 days of production, at 24505.86 m³ / s. 3 ·d -1Subsequently, due to the complete decomposition of natural gas hydrates near the wellbore, free CH4 gas could not be replenished, and with the decrease in formation pressure, the production well's own productivity decreased, leading to a rapid decline in the gas production rate. After five years of additional production, specifically on the 3165th day of cumulative production, the gas production rate rapidly decreased to 5000 m³ / h. 3 ·d -1 At this point, the total gas production is 2.8 × 10⁻⁶. 7 m 3 The output over those 8 years accounted for 37.8% of the total output over 50 years. Over the next nearly 42 years of simulation, the gas production rate remained stable, decreasing slowly over a long period, eventually reaching 2270 m³ / s. 3 ·d -1 The cumulative gas production over 50 years is 7.44 × 10⁻⁶. 7 m 3 Compared to depressurization extraction, CO2 injection into the formation for displacement gas production also initially shows a continuously increasing gas production rate. However, the peak gas production rate of displacement production occurs slightly later than that of depressurization production, reaching 22016.11 m³ on day 1247. 3 ·d -1 The gas production rate was lower than the maximum production rate of depressurization production. Since the majority of natural gas comes from the decomposition of solid hydrates caused by depressurization, with a small amount from CO2 replacing CH4, the injection well increases the reservoir pressure to some extent during CO2 replacement, thus reducing the gas production from depressurization decomposition. Therefore, the maximum injection rate of the replacement production process is slightly lower than that of the depressurization production case. After the gas production rate of replacement production began to decline, it exceeded that of depressurization production on day 1277. After 50 years of simulation, the gas production rate was 3074.43 m³ / s. 3 ·d -1 The cumulative gas production is 9.06 × 10⁻⁶ 7 m 3 This exceeds the cumulative gas production from pressure reduction production by 21.78%.

[0086] Example 4 Based on the same inventive concept, this embodiment discloses a computer-readable storage medium storing a computer program, which is executed by a processor to implement the numerical simulation method for carbon dioxide replacement hydrate mining and geological storage as described above.

[0087] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0088] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0089] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0090] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific embodiments of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention. The above content is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims

1. A numerical simulation method for the extraction and geological storage of carbon dioxide replacement hydrates, characterized in that, Includes the following steps: Establish a kinetic model for the formation and decomposition of natural gas hydrates; Establish the mass conservation equation, energy conservation equation, relative permeability model, porosity-permeability relationship, and reaction equilibrium value calculation model for CH4 and CO2 natural gas hydrates; Establish a mathematical model for the thermal-fluid-mechanical-chemical multi-field coupled extraction and storage of natural gas hydrates; By combining the kinetic model of natural gas hydrate formation and decomposition, the mass conservation equations and energy conservation equations of CH4 and CO2 natural gas hydrates, the relative permeability model, the porosity-permeability relationship and reaction equilibrium value calculation model, and the thermo-fluid-mechanical-chemical multi-field coupled mathematical model of natural gas hydrate replacement exploitation and storage, the mathematical model is numerically solved to obtain the pressure, temperature, hydrate concentration and strain values ​​at different times and spaces, thereby analyzing the characteristics of carbon dioxide replacement hydrate exploitation and geological storage.

2. The numerical simulation method for carbon dioxide replacement hydrate extraction and geological storage as described in claim 1, characterized in that, The calculation formula for the natural gas hydrate formation kinetic model is as follows: in, It is the concentration of hydrates formed. It is time. It is the surface area of ​​the spherical particles that make up hydrates in a porous medium. It is the density of water. It is porosity. It is the water saturation in porous media. It is the hydrate saturation in porous media. Here, E is the equilibrium pressure, E is the activation energy of the reaction, R is the gas constant, and T is the temperature. It is the equilibrium value of hydrates under certain pressure and temperature.

3. The numerical simulation method for carbon dioxide replacement hydrate extraction and geological storage as described in claim 2, characterized in that, The calculation formula for the natural gas hydrate formation kinetic model is as follows: in, It is the concentration of decomposed hydrates. It is the frequency factor of hydrate decomposition reaction. It is the density of hydrates.

4. The numerical simulation method for carbon dioxide replacement hydrate extraction and geological storage as described in claim 2, characterized in that, The mass conservation equation for the natural gas hydrate is: Gaseous CO2: Gas phase CH4: Liquid phase: Solid CO2 hydrate: Solid CH4 hydrate: in, It is the density of carbon dioxide. It refers to the saturation level of carbon dioxide. It is the volumetric flow rate of carbon dioxide. It is the mass of carbon dioxide. It is a source and sink phase of carbon dioxide. It is the density of methane. It is the saturation level of methane. It is the volumetric flow rate of methane. yes quality It is a methane source-sink phase. It is the volumetric flow rate of the aqueous phase. It is the mass of the aqueous phase. It is a water phase source and confluence phase.

5. The numerical simulation method for carbon dioxide replacement hydrate extraction and geological storage as described in claim 2, characterized in that, The mass conservation equation for the natural gas hydrate is: in, It is the effective thermal conductivity. It is the density of the gas. It is the relative volumetric velocity of the gas phase. It is vapor phase enthalpy. It is the relative volumetric velocity of the water phase. It is the enthalpy of the aqueous phase. It is the heat required for the formation or decomposition of hydrates. It is the density of the rock skeleton. It refers to the saturation of hydrates. It is the enthalpy of the rock skeleton. It is the density of the hydrate. It is the enthalpy of hydrate. It refers to the saturation of the aqueous phase. It refers to the saturation of the gas phase.

6. The numerical simulation method for carbon dioxide replacement hydrate extraction and geological storage as described in claim 5, characterized in that, The relative penetration rate model is: in: in, It is the relative permeability of the aqueous phase. It is the relative permeability of the gas phase. It is bound water saturation. It is the residual gas saturation. , All are power-law coefficients. For capillary pressure, The initial capillary pressure, It is the Van Genuchten index; The relationship between porosity and permeability is as follows: in, It is the effective penetration rate. It is the initial permeability of the formation. It is the initial porosity of the formation; It is a penetration rate decline index.

7. The numerical simulation method for carbon dioxide replacement hydrate extraction and geological storage as described in claim 5, characterized in that, The relative penetration rate model is: Where K is the equilibrium value of the reaction. , , , and These are all fitted parameters. This is the current gas phase pressure.

8. The numerical simulation method for carbon dioxide replacement hydrate extraction and geological storage as described in claim 5, characterized in that, The mathematical model for the thermal-fluid-mechanical-chemical multi-field coupled natural gas hydrate replacement exploitation and storage is as follows: in, It is the original porosity of the reservoir considering the deformation of the medium. It is the fluid density. It is the internal energy of the fluid phase, J·kg -1 , It is the density of solid particles, kg·m -3 , It is the internal energy of the rock phase. It's viscosity. It's pressure, in kPa. It is a volume force, m·s -2 , It is the enthalpy of fluid. It is thermal conductivity. It is external heat.

9. A numerical simulation system for the extraction and geological storage of carbon dioxide replacement hydrates, characterized in that, include: The kinetic model building module is used to build kinetic models for the formation and decomposition of natural gas hydrates; The module for establishing reaction-related models of natural gas hydrates is used to establish the mass conservation equation, energy conservation equation, relative permeability model, porosity-permeability relationship, and reaction equilibrium value calculation model for CH4 and CO2 natural gas hydrates. The multi-field coupling model establishment module is used to establish a mathematical model for the thermal-fluid-mechanical-chemical multi-field coupling of natural gas hydrate replacement exploitation and storage; The model fusion module is used to combine the kinetic model of natural gas hydrate formation and decomposition, the mass conservation equation of CH4 and CO2 natural gas hydrate, the energy conservation equation, the relative permeability model, the porosity, permeability relationship and reaction balance value calculation model, and the thermo-fluid-mechanical-chemical multi-field coupled mathematical model of natural gas hydrate replacement mining and storage to analyze the characteristics of carbon dioxide replacement hydrate mining and geological storage.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that is executed by a processor to implement the numerical simulation method for carbon dioxide displacement hydrate mining and geological storage as described in any one of claims 1-8.

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