A method for predicting recoverable resources of an underground hydrogen reservoir

Abstract

The present application belongs to the field of natural hydrogen resource exploration, and proposes a method for predicting the exploitable resource quantity of underground hydrogen reservoirs, comprising: establishing a multi-process and multi-physical field coupling model describing the generation-migration-dissolution-biological consumption processes of natural hydrogen; establishing a reservoir geological model of the area where the natural hydrogen reservoir is located according to real geological exploration data, setting the initial conditions and boundary conditions of the reservoir geological model, and performing grid division on the reservoir geological model; inputting the constructed reservoir geological model into the established multi-physical field coupling model to obtain the dynamic spatio-temporal evolution law of the generation-migration-dissolution-accumulation-biological consumption process of natural hydrogen, quantifying the proportion of generated hydrogen among free state, dissolved state, accumulation and biological consumption, and realizing effective prediction of the exploitable resource quantity of hydrogen reservoirs. The present application can effectively predict the dynamic spatio-temporal evolution law of natural hydrogen accumulation, and quantitatively represent the synergistic control effect of multiple mass transfer processes on the evolution of hydrogen accumulation.

Description

Technical Field

[0001] This invention belongs to the field of natural hydrogen resource exploration, and specifically discloses a method for predicting the exploitable resources of underground hydrogen reservoirs. Background Technology

[0002] In recent years, an increasing number of countries have adopted carbon neutrality as a national strategy, proposing visions for a low-carbon future. Currently, anthropogenic carbon dioxide emissions mainly come from the consumption of fossil fuels. Therefore, developing new energy sources and achieving energy transition are crucial measures to reduce carbon dioxide emissions. Hydrogen, when burned, only produces water vapor, without pollutants or greenhouse gases such as carbon dioxide, and is considered the most promising non-fossil energy resource in the current context of carbon neutrality. Electrolysis of water to produce green hydrogen is considered a potential future method of hydrogen production. However, currently, this method is relatively expensive, and its output accounts for only 0.1% of total hydrogen production, far below the hydrogen demand target set in the International Energy Agency's roadmap. Therefore, abundant underground natural hydrogen reserves have become a mainstay of the future energy revolution.

[0003] Geological and geochemical exploration data from natural hydrogen reservoirs in Mali indicate that underground hydrogen primarily originates from the reaction of fir olivine with water in deep strata, i.e., serpentinization. The hydrogen released during this process migrates under gravity along fault zones and permeable strata, accumulating in shallow reservoirs (<1000 m) under the capping effect of overlying tight igneous layers, forming a gas cap with a certain degree of saturation. Simultaneously, hydrogen exists in large quantities in dissolved form in the underlying aquifer. These processes indicate that the formation and evolution of natural hydrogen reservoirs involves multiple mass migration processes, including hydrogen generation, hydrogen migration and capture, pore water dissolution, and biological consumption. The final reservoir state is determined by the coupling effects between these processes. Existing research only addresses the generation process of natural hydrogen, lacking descriptions of its subsequent migration-dissolution-consumption processes. This hinders an effective understanding of the dynamic formation and evolution of hydrogen reservoirs and the contribution and role of each process in hydrogen accumulation, affecting the effective assessment of exploitable hydrogen resources. Summary of the Invention

[0004] This invention proposes a method for predicting the exploitable resources of underground hydrogen reservoirs, based on the dynamic spatiotemporal evolution of natural hydrogen accumulation and the quantitative characterization of the synergistic control effect of multiple hydrogen mass migration processes on accumulation evolution.

[0005] This invention provides a method for predicting the exploitable resources of underground hydrogen reservoirs, comprising the following steps:

[0006] S1. Establish a multi-physics coupling model to describe the processes of natural hydrogen generation, migration, dissolution and biological consumption, including the reaction kinetics model of natural hydrogen generation through water-rock reaction, the mass conservation equation of hydrogen and water, the dissolution and diffusion equation of hydrogen in the aqueous phase, the microbial consumption equation of hydrogen, and the energy conservation equation of fluid-rock skeleton.

[0007] S2. Establish a reservoir geological model of the area where the natural hydrogen reservoir is located based on real geological exploration data, including the reaction layer, reservoir and caprock system; set the initial conditions and boundary conditions of the reservoir geological model, and divide the reservoir geological model into grids;

[0008] S3. Input the reservoir geological model constructed in step S2 into the multiphysics coupling model obtained in step S1, calculate the hydrogen content of each process of natural hydrogen generation, migration without reservoir formation, dissolution, migration into reservoir formation and biological consumption, obtain the proportion of generated hydrogen among free non-reservoir formation, dissolution, reservoir formation and biological consumption, and finally realize the effective prediction of the exploitable resources of underground hydrogen reservoirs based on the amount of hydrogen reservoir formation and its proportion.

[0009] According to some embodiments of this application, a method for predicting the exploitable resources of an underground hydrogen reservoir, wherein step S1, the method for establishing a multiphysics coupling model includes:

[0010] Construct the mass conservation equation for the aqueous phase:

[0011]

[0012] in, Indicates the porosity of the formation. Indicates the saturation of the water phase. This indicates the density of the aqueous phase. Indicates the flow velocity of the water phase. This indicates the rate of change in the mass of the aqueous phase consumed due to the water-rock reaction; Indicates divergence;

[0013] Construct the mass conservation equation for hydrogen:

[0014]

[0015] in, Indicates the saturation level of hydrogen gas. This indicates the density of hydrogen gas. Indicates the flow rate of hydrogen gas. This indicates the rate of mass change of hydrogen gas produced by the water-rock reaction. This indicates the rate of mass change due to hydrogen consumption by microorganisms. This indicates the rate of mass loss due to hydrogen dissolution;

[0016] Construct the reaction kinetic equation for hydrogen production:

[0017]

[0018]

[0019]

[0020] in, Indicates the mass of the rock solid; This indicates the rate of rock mass loss caused by the water-rock reaction; Indicates the molar mass of hydrogen gas; Indicates the molar mass of water; Indicates the molar mass of the rock; The reaction rate coefficient can be expressed as:

[0021]

[0022] in, This indicates the optimal reaction temperature for the water-rock reaction; Indicates formation temperature; Indicates the reaction constant;

[0023] Construct equations for the solubility and diffusion of hydrogen in the aqueous phase:

[0024]

[0025] in, This indicates the molar concentration of dissolved hydrogen in the aqueous phase. This represents the diffusion coefficient of hydrogen in the aqueous phase; The rate of mass consumption due to hydrogen dissolution can be expressed as:

[0026]

[0027] in, Represents the solubility constant. This represents the specific surface area of ​​the hydrogen-water interface. This indicates the equilibrium concentration of hydrogen gas at dissolution.

[0028] Constructing the microbial consumption equation for hydrogen:

[0029]

[0030] in, Biological consumption coefficient;

[0031] Constructing the energy conservation equation for the fluid-rock skeleton:

[0032]

[0033]

[0034] in, Indicates rock mass. Indicates the specific heat capacity of rocks. This indicates the specific heat capacity of hydrogen. This indicates the specific heat capacity of water. Indicates the thermal conductivity of the rock. Indicates the thermal conductivity of water phase. This represents the thermal conductivity of hydrogen. This represents the enthalpy value.

[0035] According to some embodiments of this application, a method for predicting the exploitable resources of an underground hydrogen reservoir, in step S2, the geological exploration data includes the underground depth of the reaction layer, reservoir, and caprock system and their horizontal extension width along the surface. The thickness of each layer is determined based on its underground depth, and the width of each layer is determined based on its horizontal extension width along the surface.

[0036] According to some embodiments of this application, a method for predicting the exploitable resources of an underground hydrogen reservoir, in step S2, setting the initial conditions of the reservoir geological model includes: setting the content of fir olivine, water saturation, initial formation pressure, and initial formation temperature within the reservoir geological model.

[0037] According to some embodiments of this application, a method for predicting the exploitable resources of an underground hydrogen reservoir, in step S2, setting the boundary conditions of the reservoir geological model includes setting the left boundary pressure, upper boundary pressure, lower boundary pressure, right boundary pressure, upper boundary temperature, lower boundary temperature, left boundary temperature, and right boundary temperature of the reservoir geological model.

[0038] According to some embodiments of this application, a method for predicting the exploitable resources of an underground hydrogen reservoir is provided. In step S2, the grid division adopts a mapped grid division method; wherein the horizontal grid spacing is set to 1~2 m, and the vertical grid spacing is set to 1~2 m.

[0039] According to some embodiments of this application, a method for predicting the exploitable resources of an underground hydrogen reservoir, step S3 includes:

[0040] The reservoir geological model constructed in step S2 is input into the multiphysics coupling model obtained in step S1 to calculate the hydrogen saturation. Molar concentration of hydrogen dissolved in water and the volume fraction of hydrogen consumed by organisms The hydrogen saturation is further divided into reservoir-forming saturation and non-reservoir-forming saturation based on the location of hydrogen in the formation after migration. Subsequently, within the entire reservoir geological model space, the obtained hydrogen saturation, dissolved molar concentration in water, and biological consumption volume fraction are spatially integrated to finally obtain the contents of free hydrogen, dissolved hydrogen in water, reservoir-forming hydrogen, and biologically consumed hydrogen in the entire reservoir geological model, and then the proportion of each part is calculated.

[0041] The beneficial effects of this invention are as follows: This invention proposes a method for predicting the exploitable resources of underground hydrogen reservoirs. It reveals the dynamic spatiotemporal evolution of the natural hydrogen generation-migration-dissolution-accumulation-biological consumption process, quantifies the proportions of generated hydrogen in the free, dissolved, accumulated, and biologically consumed states, and achieves effective prediction of the hydrogen reservoir formation and evolution process. Compared with existing technologies, this invention, for the first time, effectively correlates the hydrogen generation process with the migration-dissolution-biological consumption process required for accumulation, achieving effective prediction of the dynamic process of hydrogen reservoir formation and evolution. Furthermore, this invention also quantifies the specific proportions of hydrogen in different occurrence states (free, dissolved, accumulated, and biologically consumed), providing an effective method for assessing the exploitability of natural hydrogen reservoirs. Attached Figure Description

[0042] Figure 1 This is a flowchart illustrating a method for predicting the exploitable resources of an underground hydrogen reservoir according to an embodiment of the present invention.

[0043] Figure 2 This is a schematic diagram of the simulation domain of the reservoir geological model used in the embodiments of the present invention.

[0044] Figure 3 (a) is a schematic diagram of the evolution of free hydrogen saturation over 50 years calculated in the embodiment of the present invention; (b) is a schematic diagram of the evolution of dissolved hydrogen molar concentration over 50 years calculated in the embodiment of the present invention; (c) is a schematic diagram of the evolution of the integral number of hydrogen gas consumed by microorganisms over 50 years calculated in the embodiment of the present invention.

[0045] Figure 4 The content and proportion of hydrogen under different occurrence states within 50 years are calculated in this embodiment of the invention; where (a) is the content of hydrogen under different occurrence states within 50 years, and (b) is the proportion of hydrogen under different occurrence states within 50 years. Detailed Implementation

[0046] 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.

[0047] like Figure 1As shown in the figure, this invention provides a method for predicting the exploitable resources of underground hydrogen reservoirs, including the following steps:

[0048] S1. Establish a multiphysics coupling model to describe the processes of natural hydrogen generation, migration, dissolution, and biological consumption, including:

[0049] Construct the mass conservation equation for the aqueous phase:

[0050]

[0051] in, Indicates the porosity of the formation. Indicates the saturation of the water phase. This indicates the density of the aqueous phase. Indicates the flow velocity of the water phase. This indicates the rate of change in the mass of the aqueous phase consumed due to the water-rock reaction; Indicates divergence;

[0052] Construct the mass conservation equation for hydrogen:

[0053]

[0054] in, Indicates the saturation level of hydrogen gas. This indicates the density of hydrogen gas. Indicates the flow rate of hydrogen gas. This indicates the rate of mass change of hydrogen gas produced by the water-rock reaction. This indicates the rate of mass change due to hydrogen consumption by microorganisms. This indicates the rate of mass loss due to hydrogen dissolution;

[0055] Construct the reaction kinetic equation for hydrogen production:

[0056]

[0057]

[0058]

[0059] in, Indicates the mass of the rock solid; This indicates the rate of rock mass loss caused by the water-rock reaction; Indicates the molar mass of hydrogen gas; Indicates the molar mass of water; Indicates the molar mass of the rock; The reaction rate coefficient can be expressed as:

[0060]

[0061] in, This indicates the optimal reaction temperature for the water-rock reaction; Indicates formation temperature; Indicates the reaction constant;

[0062] Construct equations for the solubility and diffusion of hydrogen in the aqueous phase:

[0063]

[0064] in, This indicates the molar concentration of dissolved hydrogen in the aqueous phase. This represents the diffusion coefficient of hydrogen in the aqueous phase; The rate of mass consumption due to hydrogen dissolution can be expressed as:

[0065]

[0066] in, Represents the solubility constant. This represents the specific surface area of ​​the hydrogen-water interface. This indicates the equilibrium concentration of hydrogen gas at dissolution.

[0067] Constructing the microbial consumption equation for hydrogen:

[0068]

[0069] in, Biological consumption coefficient;

[0070] Constructing the energy conservation equation for the fluid-rock skeleton:

[0071]

[0072]

[0073] in, Indicates rock mass. Indicates the specific heat capacity of rocks. This indicates the specific heat capacity of hydrogen. This indicates the specific heat capacity of water. Indicates the thermal conductivity of the rock. Indicates the thermal conductivity of water phase. This represents the thermal conductivity of hydrogen. This represents the enthalpy value.

[0074] S2. Based on real geological exploration data, establish a reservoir geological model of the area where the natural hydrogen reservoir is located, including the reaction layer, reservoir and caprock system, set the initial conditions and boundary conditions of the reservoir geological model, and divide the reservoir geological model into grids.

[0075] Specifically, the initial conditions for setting the reservoir geological model include: setting the content of fir olivine, water saturation, initial formation pressure, and initial formation temperature; the boundary conditions for setting the reservoir geological model include: setting the left boundary pressure, upper boundary pressure, lower boundary pressure, right boundary pressure, upper boundary temperature, lower boundary temperature, left boundary temperature, and right boundary temperature. The reservoir geological model includes a reaction layer, a reservoir, and a caprock. In this embodiment, as... Figure 2 As shown, the simulation domain has a width of 1000 m and a height of 6200 m, with a reaction layer thickness of 200 m, a reservoir thickness of 5450 m, and a caprock thickness of 550 m. Initially, the fir olivine content in the reaction layer is 100%, and the water saturation throughout the formation is 1. The initial formation pressure satisfies hydrostatic pressure, and the initial formation temperature is determined by the surface temperature and geothermal gradient. The boundary temperature and pressure of the reservoir geological model are set to constant values. An unstructured triangular mesh is used to divide the simulation domain of the reservoir model into 11218 grids.

[0076] S3. Input the reservoir geological model constructed in step S2 into the multiphysics coupling model obtained in step S1, calculate the hydrogen content of each process of natural hydrogen generation, migration without reservoir formation, dissolution, migration into reservoir formation and biological consumption, obtain the proportion of generated hydrogen among free non-reservoir formation, dissolution, reservoir formation and biological consumption, and finally realize the effective prediction of the exploitable resources of underground hydrogen reservoirs based on the amount of hydrogen reservoir formation and its proportion.

[0077] In this embodiment, as Figure 3 As shown, (a) is a schematic diagram of the evolution of free hydrogen saturation over 50 years, (b) is a schematic diagram of the evolution of dissolved hydrogen molar concentration over 50 years, and (c) is a schematic diagram of the evolution of the integral number of hydrogen gas consumed by microorganisms over 50 years. Figure 4 This represents the content and proportion of hydrogen under different occurrence conditions over a 50-year period. For example... Figure 3 and Figure 4 As shown, (1) after hydrogen flows in from underground, it accumulates in the caprock above it within 10 years; after about 30 years, it begins to escape from the caprock, but is effectively captured by the caprock, forming a hydrogen reservoir; the saturation of the hydrogen reservoir can reach 0.7, and the thickness exceeds 250 m. (2) Free hydrogen dissolves along the flow path, and the main hydrogen dissolution is located in the middle and lower part of the sandstone storage, that is, the water-rich area below the free hydrogen in this area; after 50 years, the molar concentration of dissolved hydrogen in this area is about 1200 mol / m. 3 The concentration was much higher than in other regions (< 500 mol / m³). 3(3) The biological consumption process of hydrogen mainly occurs in the hydrogen reservoir area. After 30 years, the biological consumption process of hydrogen is significantly intensified, but the biological consumption process is orders of magnitude different from the reservoir formation and dissolution process. (4) In the first year, hydrogen exists only as a free gas. In the third year after the hydrogen inflow, the strata contain three states of hydrogen: non-reserved, reservoir-formed, and dissolved. The volume of hydrogen in all three states increases over time. However, it is worth noting that the proportion of free gas eventually stabilizes at about 10%, while the proportions of dissolved and reservoir-formed gas remain at 25% and 65%, respectively. These results indicate that hydrogen reservoir formation is accompanied by multiple processes of migration, dissolution, and biological consumption. Not all generated hydrogen can be mined, and its actual exploitable resources are about 65%.

[0078] 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 exploitable resources of underground hydrogen reservoirs, characterized in that, Includes the following steps: S1. Establish a multi-physics coupling model to describe the processes of natural hydrogen generation, migration, dissolution and biological consumption, including the reaction kinetics model of natural hydrogen generation through water-rock reaction, the mass conservation equation of hydrogen and water, the dissolution and diffusion equation of hydrogen in the aqueous phase, the microbial consumption equation of hydrogen, and the energy conservation equation of fluid-rock skeleton. The process of constructing a multiphysics coupling model includes: Construct the mass conservation equation for the aqueous phase: in, Indicates the porosity of the formation. Indicates the saturation of the water phase. This indicates the density of the aqueous phase. Indicates the flow velocity of the water phase. This indicates the rate of change in the mass of the aqueous phase consumed due to the water-rock reaction; Indicates divergence; Construct the mass conservation equation for hydrogen: in, Indicates the saturation level of hydrogen gas. This indicates the density of hydrogen gas. Indicates the flow rate of hydrogen gas. This indicates the rate of mass change of hydrogen gas produced by the water-rock reaction. This indicates the rate of mass change due to hydrogen consumption by microorganisms. This indicates the rate of mass loss due to hydrogen dissolution; Construct the reaction kinetic equation for hydrogen production: in, Indicates the mass of the rock solid; This indicates the rate of rock mass loss caused by the water-rock reaction; Indicates the molar mass of hydrogen gas; Indicates the molar mass of water; Indicates the molar mass of the rock; The reaction rate coefficient is expressed as: in, This indicates the optimal reaction temperature for the water-rock reaction; Indicates formation temperature; Indicates the reaction constant; Construct equations for the solubility and diffusion of hydrogen in the aqueous phase: in, This indicates the molar concentration of dissolved hydrogen in the aqueous phase. This represents the diffusion coefficient of hydrogen in the aqueous phase; The rate of mass loss due to hydrogen dissolution is expressed as: in, Represents the solubility constant. This represents the specific surface area of ​​the hydrogen-water interface. This indicates the equilibrium concentration of hydrogen gas at dissolution. Constructing the microbial consumption equation for hydrogen: in, Biological consumption coefficient; Constructing the energy conservation equation for the fluid-rock skeleton: in, Indicates rock mass. Indicates the specific heat capacity of rocks. This indicates the specific heat capacity of hydrogen. This indicates the specific heat capacity of water. Indicates the thermal conductivity of the rock. Indicates the thermal conductivity of water phase. This represents the thermal conductivity of hydrogen. Indicates enthalpy value; S2. Establish a reservoir geological model of the area where the natural hydrogen reservoir is located based on real geological exploration data, including the reaction layer, reservoir and caprock system; set the initial conditions and boundary conditions of the reservoir geological model, and divide the reservoir geological model into grids; S3. Input the reservoir geological model constructed in step S2 into the multiphysics coupling model obtained in step S1, calculate the hydrogen content of each process of natural hydrogen generation, migration without reservoir formation, dissolution, migration into reservoir formation and biological consumption, obtain the proportion of generated hydrogen among free non-reservoir formation, dissolution, reservoir formation and biological consumption, and finally realize the effective prediction of the exploitable resources of underground hydrogen reservoirs based on the amount of hydrogen reservoir formation and its proportion.

2. The method for predicting the exploitable resources of underground hydrogen reservoirs according to claim 1, characterized in that, In step S2, the geological exploration data includes the underground depth of the reaction layer, reservoir, and caprock system and their horizontal extension width along the surface. The thickness of each layer is determined based on its underground depth, and the width of each layer is determined based on its horizontal extension width along the surface.

3. The method for predicting the exploitable resources of underground hydrogen reservoirs according to claim 1, characterized in that, In step S2, the initial conditions of the reservoir geological model include the content of fir olivine, water saturation, initial formation pressure, and initial formation temperature.

4. The method for predicting the exploitable resources of underground hydrogen reservoirs according to claim 1, characterized in that, In step S2, the boundary conditions of the reservoir geological model include left boundary pressure, upper boundary pressure, lower boundary pressure, right boundary pressure, upper boundary temperature, lower boundary temperature, left boundary temperature, and right boundary temperature.

5. The method for predicting the exploitable resources of underground hydrogen reservoirs according to claim 1, characterized in that, In step S2, the mesh division adopts the mapping mesh division method; wherein, the horizontal mesh spacing is set to 1~2 m, and the vertical mesh spacing is set to 1~2 m.

6. The method for predicting the exploitable resources of underground hydrogen reservoirs according to claim 2, characterized in that, Step S3 includes: The reservoir geological model constructed in step S2 is input into the multiphysics coupling model obtained in step S1 to calculate the hydrogen saturation. Molar concentration of hydrogen dissolved in water and the volume fraction of hydrogen consumed by organisms The hydrogen saturation is further divided into reservoir-forming saturation and non-reservoir-forming saturation based on the location of hydrogen in the formation after migration. Subsequently, within the entire reservoir geological model space, the obtained hydrogen saturation, dissolved molar concentration in water, and biological consumption volume fraction are spatially integrated to finally obtain the contents of free hydrogen, dissolved hydrogen in water, reservoir-forming hydrogen, and biologically consumed hydrogen in the entire reservoir geological model, and then the proportion of each part is calculated.

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