Prediction Method of Multiphysics Field Coupling Process of Natural Hydrogen Flow-Heat Transfer-Rock Thermal Strain in Subsurface Pores
By establishing a multiphysics coupling model of phase field variables, the problem of predicting natural hydrogen flow and rock thermal strain at the pore scale was solved, enabling accurate assessment and stability analysis of the natural hydrogen accumulation process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN UNIV OF TECH
- Filing Date
- 2025-11-19
- Publication Date
- 2026-06-30
AI Technical Summary
Existing technologies lack multi-physics field coupling prediction models for natural hydrogen flow, heat transfer, and rock thermal strain at the pore scale, resulting in limited understanding of the multi-field response mechanisms during hydrogen accumulation and affecting the accurate assessment of resource reserves and accumulation stability.
A multiphysics coupling model based on phase field variables was established, including mass conservation, momentum conservation, energy conservation, and thermal strain equations. The model was then meshed based on the actual underground pore structure to predict the dynamic evolution characteristics of hydrogen flow, heat transfer, and rock thermal strain.
This study enabled a more accurate and systematic assessment of the natural hydrogen accumulation mechanism and its stability, and revealed the dynamic evolution characteristics of fluid flow, heat transfer, and rock thermal strain in porous media.
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Figure CN121543491B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of natural hydrogen resource exploration, and specifically discloses a method for predicting the multi-physics field coupling process of natural hydrogen flow-heat transfer-rock thermal strain in underground pores. Background Technology
[0002] Natural hydrogen, as an emerging clean energy source, possesses abundant reserves and sustainable development potential, and is considered an important component of future energy structure transformation. Compared to fossil fuels, natural hydrogen produces almost no carbon dioxide upon combustion, effectively reducing greenhouse gas emissions. Furthermore, natural hydrogen is found in underground geological systems, exhibiting high purity and continuous recharge capacity, resulting in low energy consumption and minimal environmental impact during its development and utilization. In-depth research into the formation, migration, and accumulation mechanisms of natural hydrogen is of significant scientific and strategic value for promoting its commercial exploitation, ensuring energy security, and building a low-carbon energy system.
[0003] Natural hydrogen is generated in deep formations at depths of over 10,000 meters, and its formation process is controlled by multiple factors, including temperature and pressure. After generation, the hydrogen migrates along seepage channels within the formation, and its flow path and migration rate directly determine the accumulation mode and final reservoir state, necessitating research into the microscopic migration mechanisms at the pore scale. Furthermore, since deep formation temperatures can reach up to 300°C, the generation and migration of hydrogen are often accompanied by strong thermal strain effects. This not only alters the reservoir's pore structure and permeability but may also induce formation deformation or even fracturing, thus affecting reservoir safety and stability. Therefore, establishing predictive models at the pore scale that can simultaneously couple multi-physics processes such as heat transfer, flow, and thermal strain is crucial for revealing the formation process and stability of deep natural hydrogen. However, the current lack of multi-physics coupled predictive models at the pore scale limits our understanding of the multi-field response mechanisms during hydrogen accumulation, thus hindering accurate assessments of resource reserves and reservoir stability. Summary of the Invention
[0004] To address the challenge of predicting the dynamic spatiotemporal evolution of natural hydrogen flow, heat transfer, and rock thermal strain within underground pores, and to achieve a more accurate and systematic assessment of the natural hydrogen accumulation mechanism and its stability, a multiphysics coupling process prediction method for natural hydrogen flow-heat transfer-rock thermal strain within underground pores, as described in some embodiments of this application, includes the following steps:
[0005] A multiphysics coupling model describing the flow of natural hydrogen gas, heat transfer, and thermal strain of rocks within formation pores is established based on phase field variables.
[0006] A porous medium geometric model is established based on the underground pore structure of the rock. The porous medium geometric model is then meshed to obtain several mesh elements representing the different spatial distribution locations of natural hydrogen gas in the underground pore structure of the rock. Initial conditions and boundary conditions of the porous medium geometric model are then set.
[0007] Based on the multiphysics coupling model, the spatiotemporal evolution characteristics of hydrogen volume fraction, water volume fraction, fluid temperature, rock matrix temperature, and rock matrix thermal strain values of each grid cell in the porous medium geometric model are solved to obtain their distribution in time and space.
[0008] According to the multi-physics coupling process prediction method of natural hydrogen flow-heat transfer-rock thermal strain in underground pores in some embodiments of this application, a multi-physics coupling model describing natural hydrogen flow-heat transfer-rock thermal strain in formation pores is established based on the mass conservation equation, momentum conservation equation, energy conservation equation and thermal strain equation of phase field variables.
[0009] According to the multiphysics coupling process prediction method of natural hydrogen flow-heat transfer-rock thermal strain in underground pores in some embodiments of this application, the porous medium geometric model includes a rock skeleton matrix and fluid channels.
[0010] According to the multiphysics coupling process prediction method for natural hydrogen flow-heat transfer-rock thermal strain in underground pores in some embodiments of this application, the construction process of the multiphysics coupling model includes:
[0011] The mass conservation equation for the phase field variables of the hydrogen-water two-phase fluid is constructed as follows:
[0012]
[0013] In the formula, For phase field variables, =1 represents the hydrogen phase. =-1 indicates the liquid phase; For time; For fluid velocity; For gradient operators; It is a divergence operator; For phase interface thickness control parameters; The interfacial tension coefficient; This is the kinetic energy adjustment parameter in the phase field equation; Chemical potential;
[0014] Chemical potential Controlled by phase field variables and interface thickness, it is expressed as:
[0015]
[0016] The momentum conservation equation for the phase field variables of the hydrogen-water two-phase fluid is constructed as follows:
[0017]
[0018] In the formula, For fluid density; [ ] is the divergence operator; For fluid pressure; Unit tensor; For fluid viscosity; This is the volume force term for surface tension;
[0019] Among them, fluid density Fluid viscosity Specific heat capacity of fluids and fluid thermal conductivity Controlled by phase field variables, it is expressed as:
[0020]
[0021]
[0022]
[0023]
[0024] In the formula, The density of hydrogen gas; The density of water; The viscosity of hydrogen gas; The viscosity of water; The specific heat capacity of hydrogen; This refers to the specific heat capacity of water. The thermal conductivity of hydrogen; The thermal conductivity of water;
[0025] The fluid volume fraction is controlled by the phase field variable and is expressed as:
[0026]
[0027]
[0028] In the formula, The integral number of hydrogen gas. This represents the volume fraction of water.
[0029] The energy conservation equation for the phase field variables of the hydrogen-water two-phase fluid is constructed as follows:
[0030]
[0031] In the formula, For fluid temperature;
[0032] Based on the fact that only heat conduction occurs in the rock skeleton matrix within the underground pore structure of the rock, the temperature of the rock skeleton matrix... , is represented as:
[0033]
[0034] In the formula, The temperature of the rock matrix; The density of the rock matrix; Specific heat capacity of the rock matrix; Thermal conductivity of the rock matrix;
[0035] Based on the principle that the temperature of the fluid at the surface of the rock matrix in the underground pore structure of rock is equal to the temperature of the surface of the rock matrix, the temperature of the surface of the rock matrix in the underground pore structure of rock is... , is represented as:
[0036]
[0037] In the formula, the thermal strain equation for constructing the rock skeleton matrix is expressed as:
[0038]
[0039]
[0040] In the formula, The value represents the thermal strain of the rock. The thermal strain coefficient varies with rock temperature; The initial temperature of the rock matrix.
[0041] According to the multiphysics coupling process prediction method of natural hydrogen flow-heat transfer-rock thermal strain in underground pores in some embodiments of this application, the initial conditions of the porous medium geometric model include the initial volume fraction of the fluid, the initial flow velocity of the fluid, the initial temperature of the fluid, the initial temperature of the rock skeleton matrix, and the thermal strain value of the rock skeleton matrix.
[0042] According to the multiphysics coupling process prediction method for natural hydrogen flow-heat transfer-rock thermal strain in underground pores in some embodiments of this application, the boundary conditions of the porous medium geometric model include the volume fraction of the fluid at the lower boundary, the volume fraction of the fluid at the upper boundary, the flow velocity at the lower boundary, the pressure at the upper boundary, the temperature at the lower boundary, and the temperature at the upper boundary.
[0043] According to the multiphysics field coupling process prediction method of natural hydrogen flow-heat transfer-rock thermal strain in underground pores in some embodiments of this application, the mesh division method includes free triangular mesh division.
[0044] According to the multiphysics field coupling process prediction method for natural hydrogen flow-heat transfer-rock thermal strain in underground pores in some embodiments of this application, the size of the largest grid cell is 5 times the size of the smallest grid cell.
[0045] According to the multiphysics field coupling process prediction method of natural hydrogen flow-heat transfer-rock thermal strain in underground pores in some embodiments of this application, the simulation domain of the underground pore structure of the rock has a width of 650 nm and a height of 320 nm.
[0046] Based on the multiphysics field coupling process prediction method for natural hydrogen flow-heat transfer-rock thermal strain in underground pores in some embodiments of this application, the spatiotemporal evolution characteristics are illustrated in the figure.
[0047] Beneficial Effects: The multi-physics coupling process prediction method for natural hydrogen flow-heat transfer-rock thermal strain in underground pores of this invention can reveal the dynamic evolution characteristics of fluid flow, heat transfer, and rock thermal strain processes during the migration of natural hydrogen in porous media, achieving effective prediction of the multi-field coupling process of natural hydrogen flow-heat transfer-rock thermal strain in underground pores. Compared with existing technologies, this invention fully considers the fluid-rock heat transfer effects accompanying hydrogen flow and the rock thermal strain caused by temperature changes in the model, overcoming the limitation of existing studies that can only characterize fluid migration processes at the pore scale, and achieving a more accurate and systematic assessment of the natural hydrogen accumulation mechanism and accumulation stability. Attached Figure Description
[0048] Figure 1 This is a flowchart of a method for predicting the multiphysics coupling process of natural hydrogen flow-heat transfer-rock thermal strain in underground pores, as described in an embodiment of the present invention.
[0049] Figure 2 This is a geometrical schematic diagram of the underground porous medium structure used in the embodiments of the present invention.
[0050] Figure 3The diagrams are as follows: (a) is a schematic diagram of the evolution of the natural hydrogen gas fraction in the porous medium within 50 seconds calculated in the embodiment of the present invention; (b) is a schematic diagram of the evolution of the liquid water volume fraction in the porous medium within 50 seconds calculated in the embodiment of the present invention; (c) is a schematic diagram of the evolution of the fluid temperature in the porous medium within 50 seconds calculated in the embodiment of the present invention; (d) is a schematic diagram of the evolution of the rock skeleton matrix temperature in the porous medium within 50 seconds calculated in the embodiment of the present invention; and (e) is a schematic diagram of the evolution of the thermal strain of the rock skeleton matrix in the porous medium within 50 seconds calculated in the embodiment of the present invention. Detailed Implementation
[0051] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.
[0052] like Figure 1 As shown, this embodiment of the invention provides a method for predicting the multiphysics coupling process of natural hydrogen flow-heat transfer-rock thermal strain within underground pores, comprising the following steps:
[0053] S1. Based on the mass conservation equation, momentum conservation equation, energy conservation equation, and thermal strain equation of phase field variables, establish a multiphysics coupled model describing the flow of natural hydrogen gas, heat transfer, and thermal strain of rocks within formation pores, including:
[0054] Construct the mass conservation equation for the phase field variables of the hydrogen-water two-phase fluid:
[0055]
[0056] in, For phase field variables ( =1 represents the hydrogen phase. =-1 represents the liquid phase); For time; For fluid velocity; For gradient operators; It is a divergence operator; For phase interface thickness control parameters; The interfacial tension coefficient; This is the kinetic energy adjustment parameter in the phase field equation; Chemical potential Controlled by phase field variables and interface thickness:
[0057]
[0058] Construct the momentum conservation equation for the phase field variables of the hydrogen-water two-phase fluid:
[0059]
[0060] in, For fluid density; [ ] is the divergence operator; For fluid pressure; Unit tensor; For fluid viscosity; This is the volume force term of surface tension.
[0061] Among them, fluid density Fluid viscosity Specific heat capacity of fluids and fluid thermal conductivity Controlled by phase field variables, it is expressed as:
[0062]
[0063]
[0064]
[0065]
[0066] In the formula, The density of hydrogen gas; The density of water; The viscosity of hydrogen gas; The viscosity of water; The specific heat capacity of hydrogen; This refers to the specific heat capacity of water. The thermal conductivity of hydrogen; is the thermal conductivity of water.
[0067] The fluid volume fraction is controlled by the phase field variable and is expressed as:
[0068]
[0069]
[0070] In the formula, The integral number of hydrogen gas. This represents the volume fraction of water.
[0071] Considering heat conduction and convection processes, construct the energy conservation equation for a two-phase fluid:
[0072]
[0073] In the formula, The fluid temperature.
[0074] The energy conservation equation for a rock skeleton matrix that only undergoes thermal conduction is as follows:
[0075]
[0076] in, The temperature of the rock matrix; The density of the rock matrix; Specific heat capacity of the rock matrix; The thermal conductivity of the rock matrix is given by [reference].
[0077] In the underground porous structure of rock, the temperature of the rock matrix wall and the fluid at the wall are equal. Only the temperature of the rock matrix wall in the underground porous structure is considered during heat conduction. , is represented as:
[0078]
[0079] Constructing the thermal strain equation for the rock matrix framework:
[0080]
[0081]
[0082] in, The value represents the thermal strain of the rock. The thermal strain coefficient varies with rock temperature; The initial temperature of the rock matrix.
[0083] S2. Establish a porous medium geometric model based on the actual underground pore structure of rock. The porous medium geometric model includes a rock skeleton matrix and fluid channels. Set initial conditions and boundary conditions for the geometric model and perform mesh generation.
[0084] Specifically, the initial conditions of the porous media geometric model of the underground pore structure include: setting the initial fluid volume fraction, initial flow velocity, initial temperature of the fluid and the rock matrix, and initial strain degree of the rock matrix. The boundary conditions of the porous media geometric model of the underground pore structure include: setting the lower boundary fluid volume fraction, upper boundary fluid volume fraction, lower boundary flow velocity, upper boundary pressure, lower boundary temperature, and upper boundary temperature of the geometric model. Figure 2As shown, the simulation domain has a width of 650 nm and a height of 320 nm. Initially, the volume fraction of liquid water within the pores is 100%, the initial flow velocity is 0 m / s, the initial temperature of the fluid and the rock matrix is 293.15 K, and the initial strain is 0. The volume fraction of gas at the lower boundary is 100%, the volume fraction of gas at the upper boundary is 0, the flow velocity at the lower boundary is 0.01 m / s, the pressure at the upper boundary is 101325 Pa, the temperature at the lower boundary is 333.15 K, and the temperature at the upper boundary is 293.15 K.
[0085] S3. The multi-physics coupling model constructed in step S1 is used to solve the volume fraction of hydrogen and water, fluid and rock matrix temperature, and rock matrix thermal strain value in each grid cell of the geometric model constructed in step S2, so as to realize the effective prediction of the multi-field coupling process of natural hydrogen flow-heat transfer-rock thermal strain in underground rock pores.
[0086] In this embodiment, as Figure 3 As shown, (a) is a schematic diagram of the calculated evolution of the natural hydrogen gas volume fraction in the porous medium over 50 seconds; (b) is a schematic diagram of the calculated evolution of the liquid water volume fraction in the porous medium over 50 seconds; (c) is a schematic diagram of the calculated evolution of the fluid temperature in the porous medium over 50 seconds; (d) is a schematic diagram of the calculated evolution of the rock matrix temperature in the porous medium over 50 seconds; and (e) is a schematic diagram of the calculated evolution of the thermal strain of the rock matrix in the porous medium over 50 seconds. Figure 3 As shown, hydrogen gas flows in from below the formation, displacing formation water and moving upwards, occupying part of the pore water channels. Influenced by the flow of high-temperature natural hydrogen gas, the fluid temperature in some areas within the channels increases significantly, correspondingly raising the temperature of the surrounding rock skeleton. This increase in rock skeleton temperature leads to thermal strain, with the maximum thermal strain reaching approximately 1% after 50 seconds.
[0087] This invention belongs to the field of natural hydrogen resource exploration and proposes a multi-physics coupling method for predicting the flow, heat transfer, and rock thermal strain of natural hydrogen within underground pores. This method includes establishing a multi-physics coupling model describing the flow, heat transfer, and rock thermal strain of natural hydrogen within formation pores based on the mass conservation equation, momentum conservation equation, energy conservation equation, and thermal strain equation of phase field variables. A porous medium geometric model is established based on the actual underground pore structure, initial and boundary conditions are set for the geometric model, and a mesh is generated. The constructed multi-physics coupling model is used to solve for the volume fractions of hydrogen and water, the temperatures of the fluid and rock matrix, and the thermal strain values of the rock matrix within each mesh cell of the geometric model, thus achieving effective prediction of the multi-field coupling process of natural hydrogen flow, heat transfer, and rock thermal strain within pores. This invention fully considers the fluid-rock heat transfer effects accompanying hydrogen flow and the rock thermal strain caused by temperature changes, overcoming the limitations of existing studies that can only characterize fluid transport processes at the pore scale. This enables a more accurate and systematic assessment of the natural hydrogen accumulation mechanism and its stability.
[0088] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.
Claims
1. A method for predicting the multiphysics coupling process of natural hydrogen flow-heat transfer-rock thermal strain in underground pores, characterized in that, Includes the following steps: A multiphysics coupling model describing the flow of natural hydrogen gas, heat transfer, and thermal strain of rocks within formation pores is established based on phase field variables. A porous medium geometric model is established based on the underground pore structure of the rock. The porous medium geometric model is then meshed to obtain several mesh elements representing the different spatial distribution locations of natural hydrogen gas in the underground pore structure of the rock. Initial conditions and boundary conditions of the porous medium geometric model are then set. Based on the multiphysics coupling model, the spatiotemporal evolution characteristics of hydrogen volume fraction, water volume fraction, fluid temperature, rock skeleton matrix temperature, and rock skeleton matrix thermal strain values of each grid cell of the porous medium geometric model are solved to obtain their distribution in time and space. The construction process of the multiphysics coupling model includes: The mass conservation equation for the phase field variables of the hydrogen-water two-phase fluid is constructed as follows: In the formula, For phase field variables, =1 represents the hydrogen phase. =-1 indicates the liquid phase; For time; For fluid velocity; For gradient operators; For divergence operators; For phase interface thickness control parameters; The interfacial tension coefficient; This is the kinetic energy adjustment parameter in the phase field equation; Chemical potential; Chemical potential Controlled by phase field variables and interface thickness, it is expressed as: The momentum conservation equation for the phase field variables of the hydrogen-water two-phase fluid is constructed as follows: In the formula, For fluid density; For divergence operators; For fluid pressure; Unit tensor; For fluid viscosity; This is the volume force term for surface tension; Among them, fluid density Fluid viscosity Specific heat capacity of fluids and fluid thermal conductivity Controlled by phase field variables, it is expressed as: In the formula, The density of hydrogen gas; The density of water; The viscosity of hydrogen gas; The viscosity of water; The specific heat capacity of hydrogen; The specific heat capacity of water; The thermal conductivity of hydrogen; The thermal conductivity of water; The fluid volume fraction is controlled by the phase field variable and is expressed as: In the formula, The integral number of hydrogen gas. This represents the volume fraction of water. The energy conservation equation for the phase field variables of the hydrogen-water two-phase fluid is constructed as follows: In the formula, For fluid temperature; Based on the fact that only heat conduction occurs in the rock skeleton matrix within the underground pore structure of the rock, the temperature of the rock skeleton matrix... , is represented as: In the formula, The temperature of the rock matrix; The density of the rock matrix; Specific heat capacity of the rock matrix; Thermal conductivity of the rock matrix; Based on the principle that the temperature of the fluid at the surface of the rock matrix in the underground pore structure of rock is equal to the temperature of the surface of the rock matrix, the temperature of the surface of the rock matrix in the underground pore structure of rock is... , is represented as: In the formula, the thermal strain equation for constructing the rock skeleton matrix is expressed as: In the formula, The value represents the thermal strain of the rock. The thermal strain coefficient varies with rock temperature; The initial temperature of the rock matrix.
2. The method for predicting the multiphysics coupling process of natural hydrogen flow-heat transfer-rock thermal strain in underground pores according to claim 1, wherein, Based on the mass conservation equation, momentum conservation equation, energy conservation equation, and thermal strain equation of phase field variables, a multiphysics field coupling model is established to describe the flow of natural hydrogen gas, heat transfer, and thermal strain of rocks within the pores of the formation.
3. The method for predicting the multiphysics coupling process of natural hydrogen flow-heat transfer-rock thermal strain in underground pores according to claim 1, wherein, The porous media geometric model includes a rock skeleton matrix and fluid channels.
4. The method for predicting the multiphysics coupling process of natural hydrogen flow-heat transfer-rock thermal strain in underground pores according to claim 1, characterized in that, in, The initial conditions of the porous media geometric model include the initial volume fraction of the fluid, the initial flow rate of the fluid, the initial temperature of the fluid, the initial temperature of the rock skeleton matrix, and the thermal strain value of the rock skeleton matrix.
5. The method for predicting the multiphysics coupling process of natural hydrogen flow-heat transfer-rock thermal strain in underground pores according to claim 1, characterized in that, in, The boundary conditions of the porous medium geometric model include the volume fraction of the fluid at the lower boundary, the volume fraction of the fluid at the upper boundary, the flow velocity at the lower boundary, the pressure at the upper boundary, the temperature at the lower boundary, and the temperature at the upper boundary.
6. The method for predicting the multiphysics coupling process of natural hydrogen flow-heat transfer-rock thermal strain in underground pores according to claim 1, characterized in that, in, The meshing method includes free triangle meshing.
7. The method for predicting the multiphysics coupling process of natural hydrogen flow-heat transfer-rock thermal strain in underground pores according to claim 1, characterized in that, in, The size of the largest grid cell is 5 times the size of the smallest grid cell.
8. The method for predicting the multiphysics coupling process of natural hydrogen flow-heat transfer-rock thermal strain in underground pores according to claim 1, characterized in that, in, The simulated domain of the underground pore structure of the rock has a width of 650 nm and a height of 320 nm.
9. The method for predicting the multiphysics coupling process of natural hydrogen flow-heat transfer-rock thermal strain in underground pores according to claim 1, characterized in that, The spatiotemporal evolution characteristics are illustrated in the diagram.