A method for predicting the scale of induced sand production in a geological hydrogen storage process

Abstract

A method for predicting the scale of induced formation sand production in a geological hydrogen storage process belongs to the field of underground hydrogen storage and development and utilization, and is used for solving the problem of predicting the dynamic space-time evolution characteristics of formation sand production in a geological hydrogen storage process, and the key points are to establish a mathematical model for describing the sand production process induced by the geological hydrogen storage, to establish a reservoir geological model of the underground saline aquifer according to the geological characteristics of the underground saline aquifer, to divide the reservoir geological model into grids, to obtain a plurality of grid units reflecting different spatial distribution positions of sand particles in the underground saline aquifer, and to set initial conditions and boundary conditions of the reservoir geological model. The method realizes effective characterization of the space-time evolution characteristics of the migration and output of formation sand particles in the geological hydrogen storage process, and also realizes effective prediction of the scale of formation sand production in the geological hydrogen storage process.

Description

Technical Field

[0001] This invention belongs to the field of underground hydrogen storage and development, and specifically discloses a method for predicting the scale of sand production induced in the geological hydrogen storage process. Background Technology

[0002] As a novel energy storage technology for large-scale, long-term applications, artificial geological hydrogen storage is crucial for achieving a closed-loop hydrogen energy industry chain and enabling cross-seasonal allocation of renewable energy. Compared to above-ground hydrogen storage facilities, geological hydrogen storage offers significant advantages, including enormous storage capacity, small footprint, high safety factor, and low overall cost. It can effectively address the mismatch between green hydrogen production and consumption in time and space, providing a vital energy buffer for building a high-proportion renewable energy power system. However, under the cyclical operation mode of "summer injection and winter extraction" or "storage during abundant periods and extraction during dry periods," the reservoir will experience repeated pressure fluctuations and fluid scouring. This dynamic process can easily disrupt the micromechanical equilibrium of the reservoir rocks, inducing the risk of sand production and directly restricting the operational efficiency, safe lifespan, and economic feasibility of the storage facility.

[0003] The sand production problem induced by the cyclical extraction of geological hydrogen storage stems from the drastic changes in reservoir pressure and fluid flow. During the production phase, a sudden drop in reservoir pressure increases the effective stress acting on the rock skeleton, potentially causing shear failure in weakly cemented reservoirs and generating new mobile particles. Simultaneously, the high-speed outflowing hydrogen exerts a strong drag force on the pore walls, sufficient to scour and transport the already damaged microparticles. This coupled effect of "stress failure-fluid scour" accumulates and intensifies in each injection-production cycle, ultimately leading to sand production. Formation sand production triggers a series of serious practical consequences: First, it causes reservoir pore blockage and decreased permeability, significantly reducing the injection / production capacity of the hydrogen reservoir; second, the produced solid particles severely wear downhole equipment and valves, increasing maintenance costs and safety risks; most seriously, large-scale sand production may damage the integrity of the reservoir caprock, even triggering formation collapse, leading to hydrogen leakage and posing a fatal threat to the overall airtightness and safety of the reservoir. However, the lack of effective sand production prediction models in geological hydrogen storage processes has led to a lack of effective understanding of the scale of sand production in formations during seasonal hydrogen storage, which seriously restricts the assessment of the aforementioned engineering risks. Summary of the Invention

[0004] This invention proposes a method for predicting the scale of sand production induced in geological hydrogen storage processes, in order to predict the dynamic spatiotemporal evolution characteristics of formation sand production during geological hydrogen storage.

[0005] The method for predicting the scale of formation sand production induced during geological hydrogen storage, as described in some embodiments of this application, includes the following steps:

[0006] Establish a mathematical model to describe the process of sand production induced by geological hydrogen storage;

[0007] Based on the geological characteristics of the underground saline aquifer, a reservoir geological model of the underground saline aquifer is established. The reservoir geological model is then divided into grids to obtain several grid cells representing the different spatial distribution locations of reactive sand grains in the underground saline aquifer. Initial conditions and boundary conditions of the reservoir geological model are then set.

[0008] Based on the mathematical model, the spatiotemporal evolution characteristics of the volume fraction of flowing sand particles in each grid unit of the reservoir geological model are solved to obtain the distribution of flowing sand particles in time and space.

[0009] Based on the prediction method for the scale of sand production induced in geological hydrogen storage in some embodiments of this application, a mathematical model describing the sand production process induced by geological hydrogen storage is established based on Darcy's law, fluid erosion criterion and mass conservation equation.

[0010] Based on the prediction method for the scale of formation sand production induced during geological hydrogen storage in some embodiments of this application, a mathematical model describing the process of sand production induced by geological hydrogen storage is established, including:

[0011] Calculation of fluid flow velocity based on Darcy's law for fluids:

[0012]

[0013] In the formula, For fluid velocity; Rock permeability; The relative permeability of the fluid; For fluid viscosity; For fluid pressure; For fluid density; It is the acceleration due to gravity;

[0014] Calculation of rock skeleton particle detachment rate based on fluid erosion criterion:

[0015]

[0016] In the formula, The volume fraction of the rock skeleton; For time; The shedding coefficient; Rock porosity;

[0017] Calculate the volume fraction of flowing sand particles based on the mass conservation equation of the detached rock skeleton particles:

[0018]

[0019] in, This represents the volume fraction of flowing sand grains in the formation. It is a divergence operator;

[0020] in:

[0021]

[0022] In the formula, The velocity of the sand and gravel.

[0023] The method for predicting the scale of sand production induced in the geological hydrogen storage process according to some embodiments of this application also includes solving for the sand production of underground saline aquifers.

[0024] Based on the prediction method for the scale of formation sand production induced during geological hydrogen storage in some embodiments of this application, a mathematical model describing the process of sand production induced by geological hydrogen storage is established, which further includes:

[0025] Based on the volume fraction of the rock skeleton, rock porosity, and the volume fraction of flowing sand grains in the formation, the sand yield of the underground saline aquifer is calculated:

[0026] -

[0027] in, The amount of sand produced by the underground saline aquifer; It is a space integral operator.

[0028] According to the method for predicting the scale of sand production induced in the geological hydrogen storage process in some embodiments of this application, the underground reservoir geological model includes the width and height of the underground saline aquifer.

[0029] According to the prediction method for the scale of sand production induced in the geological hydrogen storage process in some embodiments of this application, the initial conditions of the reservoir geological model include the initial rock skeleton volume fraction and the initial formation flow sand grain volume fraction.

[0030] According to the method for predicting the scale of sand production induced in geological hydrogen storage processes in some embodiments of this application, the boundary conditions of the reservoir geological model include the volume fraction of flowing sand particles at the production well.

[0031] According to the method for predicting the scale of sand production induced in geological hydrogen storage processes in some embodiments of this application, the grid division method includes adaptive triangular grid division.

[0032] According to the prediction method for the scale of sand production induced in geological hydrogen storage process in some embodiments of this application, the size of the largest grid cell is 3-5 times the size of the smallest grid cell.

[0033] The beneficial effects of this invention are as follows: Compared with the prior art, the method for predicting the scale of sand production induced in the geological hydrogen storage process proposed in this invention can reveal the spatiotemporal evolution characteristics of flowing sand grains in the formation during the geological hydrogen storage process, and can quantify the sand production at different times. It provides an effective prediction method for predicting the sand production problem induced by geological hydrogen storage, overcomes the limitations of existing research in the field of geological hydrogen storage, and realizes the effective prediction of the scale of sand production induced in the geological hydrogen storage process. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating a method for predicting the scale of sand production induced in geological hydrogen storage processes, as described in an embodiment of the present invention.

[0035] Figure 2 This is a geometric schematic diagram of the saline reservoir geological model used in the embodiments of the present invention.

[0036] Figure 3 This is a schematic diagram of the evolution of the volume fraction of sand particles in the formation flow over 3 days, calculated in an embodiment of the present invention.

[0037] Figure 4 This is a schematic diagram of the cumulative sand production over 3 days calculated in an embodiment of the present invention. Detailed Implementation

[0038] 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.

[0039] like Figure 1 As shown in the figure, this invention provides a method for predicting the scale of sand production induced in geological hydrogen storage processes, comprising the following steps:

[0040] S1. A mathematical model describing the geological hydrogen storage and sand-producing process is established based on Darcy's law, fluid erosion criterion, and mass conservation equation, including:

[0041] Calculation of fluid flow velocity based on Darcy's law:

[0042]

[0043] in, For fluid velocity; Rock permeability; The relative permeability of the fluid; For fluid viscosity; For fluid pressure; For fluid density; This is the acceleration due to gravity.

[0044] Calculation of rock skeleton particle detachment rate based on fluid erosion criterion:

[0045]

[0046] in, The volume fraction of the rock skeleton; For time; The shedding coefficient; This refers to the porosity of the rock.

[0047] Calculate the volume fraction of flowing sand particles based on the mass conservation equation of the detached skeleton particles:

[0048]

[0049] in, This represents the volume fraction of flowing sand grains in the formation. It is a divergence operator; The relationship between the flow velocity of the sand and gravel and the flow velocity of the fluid is as follows:

[0050]

[0051] The method for calculating formation sand yield is as follows:

[0052] -

[0053] in, This refers to the amount of sand produced. It is a space integral operator.

[0054] S2. Establish a reservoir geological model based on the actual geological characteristics of underground saline aquifers, and perform grid division and set initial and boundary conditions for the geological model.

[0055] Specifically, the initial conditions of the underground saline aquifer reservoir geological model include: setting the initial rock skeleton volume fraction and the initial flowable sand grain volume fraction of the reservoir model; the boundary conditions of the underground saline aquifer reservoir geological model include: setting the flowable sand grain volume fraction at the production well of the reservoir model. Figure 2 As shown, the underground saline aquifer is 1000 m wide and 180 m high. Initially, the rock skeleton volume fraction is 0.7, and the flow sand volume fraction is 0. The flow sand volume fraction at the production well is set to 0.

[0056] S3. Using the mathematical model constructed in step S1, solve the volume fraction of flowing sand particles and the amount of sand produced in each grid cell of the geological model in step S2, so as to realize the effective prediction of the sand production scale of the formation during the geological hydrogen storage process.

[0057] In this embodiment, hydrogen is first continuously injected into the formation for one year, and then the injected underground hydrogen is extracted. Figure 3 This is a schematic diagram illustrating the evolution of sand grain volume fraction in formation flow over 3 days. Figure 4 This is a diagram illustrating the calculated cumulative sand production over three days. Figure 3 and Figure 4 As shown, a large amount of mobile sand particles are accumulated in the strata within a 50m radius around the production well, with a maximum volume fraction of approximately 2.3 × 10⁻⁶. -5 m 3 The flowing sand particles in the formation are being transported towards the production well and produced there. After 3 days, the cumulative sand production is approximately 2.7 m³. 3 .

[0058] This invention belongs to the field of underground hydrogen storage and development, and proposes a method for predicting the scale of sand production induced in geological hydrogen storage. The method includes establishing a mathematical model describing the sand production process induced by geological hydrogen storage based on Darcy's law, fluid erosion criteria, and the mass conservation equation; establishing a reservoir geological model based on the actual geological characteristics of underground saline aquifers, and dividing the geological model into grids, setting initial and boundary conditions; and using the constructed mathematical model to solve for the volume fraction of flowing sand particles and the sand production rate within each grid cell of the geological model, thereby achieving effective prediction of the scale of sand production in geological hydrogen storage. This invention not only effectively characterizes the spatiotemporal evolution of sand particle migration and production in geological hydrogen storage, but also achieves quantitative prediction of sand production during geological hydrogen storage.

[0059] 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 scale of sand production induced in geological hydrogen storage processes, characterized in that, Includes the following steps: Establish a mathematical model to describe the process of sand production induced by geological hydrogen storage; Based on the geological characteristics of the underground saline aquifer, a reservoir geological model of the underground saline aquifer is established. The reservoir geological model is then divided into grids to obtain several grid cells that reflect the different spatial distribution locations of flowing sand particles in the underground saline aquifer. The initial conditions and boundary conditions of the reservoir geological model are then set. Based on the mathematical model, the spatiotemporal evolution characteristics of the volume fraction of mobile sand particles in each grid unit of the reservoir geological model are solved to obtain the distribution of mobile sand particles in time and space. Among them, a mathematical model describing the process of sand production induced by geological hydrogen storage was established based on Darcy's law of fluids, fluid erosion criteria and mass conservation equation; A mathematical model describing the process of sequestration induced by geological hydrogen storage was established, including: Calculation of fluid flow velocity based on Darcy's law for fluids: In the formula, For fluid velocity; Rock permeability; The relative permeability of the fluid; For fluid viscosity; For fluid pressure; For fluid density; It is the acceleration due to gravity; Calculation of rock skeleton particle detachment rate based on fluid erosion criterion: In the formula, The volume fraction of the rock skeleton; For time; The shedding coefficient; Rock porosity; Calculation of the volume fraction of flowing sand particles based on the mass conservation equation of detached rock skeleton particles: in, This represents the volume fraction of flowing sand particles. It is a divergence operator; in: In the formula, The velocity of the flowing gravel; It also includes determining the sand production of underground saline aquifers.

2. The method for predicting the scale of formation sand production induced during geological hydrogen storage as described in claim 1, characterized in that, The establishment of a mathematical model describing the process of sequestration induced by geological hydrogen storage also includes: Calculate the sand yield of the underground saline aquifer based on the volume fraction of the rock skeleton, rock porosity, and volume fraction of mobile sand grains: - in, The amount of sand produced by the underground saline aquifer; It is a space integral operator.

3. The method for predicting the scale of formation sand production induced during geological hydrogen storage as described in claim 1, characterized in that, The reservoir geological model includes the width and height of the underground saline aquifer.

4. The method for predicting the scale of formation sand production induced during geological hydrogen storage as described in claim 1, characterized in that, The initial conditions of the reservoir geological model include the initial rock skeleton volume fraction and the initial fluid sand grain volume fraction.

5. The method for predicting the scale of formation sand production induced during geological hydrogen storage as described in claim 1, characterized in that, The meshing method includes adaptive triangular meshing.

6. The method for predicting the scale of formation sand production induced during geological hydrogen storage as described in claim 1, characterized in that, in, The size of the largest grid cell is 3-5 times the size of the smallest grid cell.

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