Method for predicting geothermal energy production performance during hydrogen storage in saline aquifer

Abstract

The application discloses a method for predicting the performance of geothermal energy exploitation in a geological hydrogen storage process, belongs to the field of geothermal energy development and utilization, and is used for solving the problems of predicting the formation temperature evolution characteristics and the production well heat production characteristics in the geological hydrogen storage process.The method is characterized by the following steps: establishing a flow-heat coupling model for describing the geological hydrogen storage process based on an energy conservation equation, a momentum conservation equation and a mass conservation equation; establishing a reservoir geological model according to underground saline aquifer geological exploration data, dividing the grid of the geological model, obtaining a plurality of grid units reflecting different spatial distribution positions of the underground saline aquifer, and setting initial conditions and boundary conditions of the reservoir geological model; and solving the formation temperature in each grid unit in the reservoir geological model and the heat flow density of the production well by using the established flow-heat coupling model, so as to realize effective prediction of the formation exploitation performance in the geological hydrogen storage process.

Description

Technical Field

[0001] This invention belongs to the field of geothermal energy development and utilization, and specifically discloses a method for predicting the geothermal energy extraction performance during the hydrogen storage process in saline aquifers. Background Technology

[0002] Against the backdrop of "dual-carbon" goals and the high proportion of renewable energy integration, geological hydrogen storage is considered an important technological means to achieve large-scale, long-term hydrogen energy regulation and storage. Compared with surface hydrogen storage, underground hydrogen storage has advantages such as large storage capacity, small land area, and flexible operating cycles, which can effectively alleviate the mismatch between the fluctuation of renewable energy output and end-use hydrogen demand. At the same time, deep strata generally have high temperature conditions, containing considerable geothermal energy potential in the hydrogen storage and production process, making geological hydrogen storage not only an energy carrier storage process, but also a possible important component of multi-energy synergistic utilization. Therefore, a systematic understanding of the characteristics of hydrogen migration and stratum temperature evolution in geological hydrogen storage is of great significance for improving the overall utilization efficiency of underground energy storage systems.

[0003] Existing research primarily focuses on the migration patterns and flow prediction of hydrogen in porous media during geological hydrogen storage. Related work emphasizes the controlling effects of pore structure, permeability characteristics, and injection / production pressure on hydrogen distribution. In contrast, insufficient attention has been paid to the evolution of formation temperature during hydrogen storage and production. Temperature changes are often simplified or considered as secondary factors, failing to reflect the coupling characteristics of heat-flow processes under actual injection and production conditions. Furthermore, quantitative prediction tools for geothermal energy release and exploitation potential in production wells are still lacking, and the understanding of heat migration and energy production during geological hydrogen storage is not systematic. These shortcomings limit a comprehensive characterization of geological hydrogen storage processes and constrain in-depth assessment of its potential for synergistic development with geothermal energy. Summary of the Invention

[0004] This invention proposes a method for predicting the geothermal energy extraction performance during geological hydrogen storage in saline aquifers, in order to predict the formation temperature evolution characteristics and production well heat generation characteristics during geological hydrogen storage.

[0005] A method for predicting geothermal energy extraction performance during hydrogen storage in saline aquifers, according to some embodiments of this application, includes the following steps:

[0006] Establish a flow-heat transfer coupling model to describe the geological hydrogen storage process;

[0007] A reservoir geological model is established based on geological exploration data of the underground saline aquifer. The geological model is then divided into grids to obtain several grid cells that reflect the different spatial distribution locations of the underground saline aquifer. Initial conditions and boundary conditions of the reservoir geological model are then set.

[0008] Based on the flow-heat coupling model, the formation temperature and heat flux density of the production well in each grid cell of the reservoir geological model are solved to obtain the temporal and spatial distribution of formation temperature and the temporal evolution of the heat flux density of the production well.

[0009] According to a method for predicting geothermal energy extraction performance in saline aquifer geological hydrogen storage process according to some embodiments of this application, a flow-heat transfer coupling model describing the geological hydrogen storage process is established based on the energy conservation equation, momentum conservation equation and mass conservation equation.

[0010] Based on a method for predicting geothermal energy extraction performance during saline aquifer geological hydrogen storage in some embodiments of this application, a flow-heat transfer coupled model describing the geological hydrogen storage process is established, including:

[0011] Calculation of formation temperature based on the energy conservation equation:

[0012]

[0013]

[0014] In the formula, Porosity; Density of the rock; Specific heat capacity of the rock; Hydrogen saturation; The density of hydrogen gas; The specific heat capacity of hydrogen; Water saturation; The density of water; is the specific heat capacity of water; T is the temperature; For time; It is a divergence operator; The thermal conductivity of the rock; The thermal conductivity of hydrogen; The thermal conductivity of water; The flow rate of hydrogen gas; The water flow velocity; For gradient operators;

[0015] Calculate the fluid velocity in the energy conservation equation based on the momentum conservation equation:

[0016]

[0017]

[0018] In the formula, This refers to the pressure of hydrogen gas. Unit tensor; The viscosity of hydrogen gas; It is the acceleration due to gravity; Water pressure; The viscosity of water;

[0019] Calculate the fluid saturation in the energy conservation equation based on the mass conservation equation:

[0020]

[0021]

[0022] The heat flux density of a production well includes both conductive heat flux density and convective heat flux density:

[0023]

[0024] In the formula, The heat flux density of the production well; It is the thermal conductivity heat flux density; The convective heat flux density is calculated as follows:

[0025]

[0026]

[0027] In the formula, For the thermal conductivity of the fluid:

[0028]

[0029] According to a method for predicting geothermal energy extraction performance during hydrogen storage in a saline aquifer, as described in some embodiments of this application, the underground reservoir geological model includes the width and height of the underground saline aquifer.

[0030] According to a method for predicting geothermal energy extraction performance during hydrogen storage in saline aquifers according to some embodiments of this application, the initial conditions of the reservoir geological model include water saturation, initial hydrogen saturation, initial hydrogen flow rate, initial water flow rate, and initial formation temperature.

[0031] According to a method for predicting geothermal energy extraction performance during hydrogen storage in saline aquifers according to some embodiments of this application, the boundary conditions of the reservoir geological model include the extraction pressure of the production well and the temperature of the right boundary of the reservoir geological model.

[0032] According to a method for predicting geothermal energy extraction performance during hydrogen storage in saline aquifers according to some embodiments of this application, the grid division method includes adaptive triangular grid division.

[0033] According to a method for predicting geothermal energy extraction performance during hydrogen storage in saline aquifers according to some embodiments of this application, the size of the largest grid cell is twice the size of the smallest grid cell.

[0034] The beneficial effects of this invention are as follows: Compared with the prior art, the method for predicting the geothermal energy extraction performance during the geological hydrogen storage process in saline aquifers proposed in this invention can reveal the evolution characteristics of formation temperature during the geological hydrogen storage process and quantify the heat flow density of production wells at different times. This provides an effective prediction method for predicting the geothermal energy extraction performance during the geological hydrogen storage process and overcomes the limitation of existing research in the field of geological hydrogen storage, which can only predict the hydrogen flow process. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating a method for predicting geothermal energy extraction performance during hydrogen storage in saline aquifers, as described in an embodiment of the present invention.

[0036] Figure 2 This is a geometric schematic diagram of the saline reservoir geological model used in the embodiments of the present invention.

[0037] Figure 3 This is a schematic diagram of the evolution of hydrogen saturation and formation temperature over 180 days calculated in an embodiment of the present invention, where a represents the evolution of hydrogen saturation over 180 days and b represents the evolution of formation temperature over 180 days.

[0038] Figure 4 This is a schematic diagram of the heat flux density of the production well over 180 days calculated in an embodiment of the present invention. Detailed Implementation

[0039] 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.

[0040] like Figure 1 As shown in the figure, this invention provides a method for predicting the geothermal energy extraction performance during hydrogen storage in saline aquifers, comprising the following steps:

[0041] S1. Based on the energy conservation equation, momentum conservation equation, and mass conservation equation, establish a flow-heat transfer coupled model to describe the geological hydrogen storage process, including:

[0042] Calculation of formation temperature based on the energy conservation equation:

[0043]

[0044]

[0045] In the formula, Porosity; Density of the rock; Specific heat capacity of the rock; Hydrogen saturation; The density of hydrogen gas; The specific heat capacity of hydrogen; Water saturation; The density of water; is the specific heat capacity of water; T is the temperature; For time; It is a divergence operator; The thermal conductivity of the rock; The thermal conductivity of hydrogen; The thermal conductivity of water; The flow rate of hydrogen gas; The water flow velocity; This is the gradient operator.

[0046] Calculate the fluid velocity in the energy conservation equation based on the momentum conservation equation:

[0047]

[0048]

[0049] In the formula, This refers to the pressure of hydrogen gas. Unit tensor; The viscosity of hydrogen gas; It is the acceleration due to gravity; Water pressure; This refers to the viscosity of water.

[0050] Calculate the fluid saturation in the energy conservation equation based on the mass conservation equation:

[0051]

[0052]

[0053] The heat flux density of a production well includes both conductive heat flux density and convective heat flux density:

[0054]

[0055] In the formula, The heat flux density of the production well; It is the thermal conductivity heat flux density; The convective heat flux density is calculated as follows:

[0056]

[0057]

[0058] In the formula, The thermal conductivity of the fluid can be calculated as follows:

[0059]

[0060] S2. Establish a reservoir geological model based on geological exploration data of underground saline aquifers, and divide the geological model into grids and set initial and boundary conditions;

[0061] Specifically, the initial conditions of the underground saline aquifer reservoir geological model include: setting the initial conditions of the reservoir model, including initial water saturation, initial hydrogen saturation, initial hydrogen flow rate, initial water flow rate, and initial formation temperature; the boundary conditions of the underground saline aquifer reservoir geological model include: setting the production pressure of the production well of the reservoir model and the temperature of the right boundary of the reservoir geological model. For example... Figure 2 As shown, the width of the underground saline aquifer is 4000m and the height is 180m. Initially, the initial water saturation is 1, the initial hydrogen saturation is 0, the initial hydrogen flow rate is 0, the initial water flow rate is 0, and the initial formation temperature is 345K. The production well's extraction pressure is 15MPa, and the right boundary temperature of the reservoir geological model is 345K.

[0062] S3. Using the flow and heat transfer coupling model constructed in step S1, solve the formation temperature and production well heat flux density in each grid cell of the geological model in step S2, so as to realize the effective prediction of formation extraction performance in the geological hydrogen storage process.

[0063] In this embodiment, hydrogen is first continuously injected into the formation for one year, and then the injected underground hydrogen is extracted. Figure 3 'a' is a schematic diagram of the calculated evolution of hydrogen saturation over 180 days. Figure 3 b is a schematic diagram of the formation temperature evolution over 180 days, obtained from calculations. Figure 4 This is a schematic diagram illustrating the calculated heat flux density of the production well over 180 days. Figure 3 and Figure 4 As shown, after hydrogen extraction began, the hydrogen content in the saline aquifer decreased significantly, and after six months, the lower part of the aquifer was completely devoid of hydrogen. Correspondingly, the temperature in the low-temperature zone of the formation recovered. Three months after extraction, the formation temperature in the lower part of the aquifer had fully recovered to its initial temperature, and after 180 days, the formation temperature of the aquifer, except for the upper third, had almost completely recovered. The heat flux density of the production well rapidly exceeded 10,000 W / m² in a short period (<50 days), and further reached 20,000 W / m² after 180 days.

[0064] 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 geothermal energy extraction performance during hydrogen storage in saline aquifers, characterized in that, Includes the following steps: Establish a flow-heat transfer coupling model to describe the geological hydrogen storage process; A reservoir geological model is established based on geological exploration data of the underground saline aquifer. The geological model is then divided into grids to obtain several grid cells that reflect the different spatial distribution locations of the underground saline aquifer. Initial conditions and boundary conditions of the reservoir geological model are then set. Based on the flow-heat coupling model, the formation temperature and heat flux density of the production well in each grid cell of the reservoir geological model are solved to obtain the temporal and spatial distribution of formation temperature and the temporal evolution of heat flux density of the production well. A flow-heat transfer coupled model describing the geological hydrogen storage process was established based on the energy conservation equation, momentum conservation equation, and mass conservation equation. Establish a flow-heat transfer coupled model to describe the geological hydrogen storage process, including: Calculation of formation temperature based on the energy conservation equation: In the formula, Porosity; Density of the rock; Specific heat capacity of the rock; Hydrogen saturation; The density of hydrogen gas; The specific heat capacity of hydrogen; Water saturation; The density of water; is the specific heat capacity of water; T is the temperature; For time; For divergence operators; The thermal conductivity of the rock; The thermal conductivity of hydrogen; The thermal conductivity of water; The flow rate of hydrogen gas; The water flow velocity; For gradient operators; Calculate the fluid velocity in the energy conservation equation based on the momentum conservation equation: In the formula, This refers to the pressure of hydrogen gas. Unit tensor; The viscosity of hydrogen gas; It is the acceleration due to gravity; Water pressure; The viscosity of water; Calculate the fluid saturation in the energy conservation equation based on the mass conservation equation: The heat flux density of a production well includes both conductive heat flux density and convective heat flux density: In the formula, The heat flux density of the production well; It is the thermal conductivity heat flux density; The convective heat flux density is calculated as follows: In the formula, For the thermal conductivity of the fluid: 。 2. The method for predicting geothermal energy extraction performance during hydrogen storage in saline aquifers according to claim 1, characterized in that, The geological model of the underground reservoir includes the width and height of the underground saline aquifer.

3. The method for predicting geothermal energy extraction performance during hydrogen storage in saline aquifers according to claim 1, characterized in that, The initial conditions of the reservoir geological model include water saturation, initial hydrogen saturation, initial hydrogen flow rate, initial water flow rate, and initial formation temperature.

4. The method for predicting geothermal energy extraction performance during hydrogen storage in saline aquifers according to claim 1, characterized in that, The boundary conditions of the reservoir geological model include the production pressure of the production well and the temperature of the right boundary of the reservoir geological model.

5. The method for predicting geothermal energy extraction performance during hydrogen storage in saline aquifers according to claim 1, characterized in that, Mesh generation methods include adaptive triangular mesh generation.

6. The method for predicting geothermal energy extraction performance during hydrogen storage in saline aquifers according to claim 1, characterized in that, in, The size of the largest grid cell is twice the size of the smallest grid cell.

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