Rock mechanics dynamic analysis method, system and equipment based on numerical simulation

Abstract

The invention provides a rock mechanics dynamic analysis method, system and equipment based on numerical simulation, and relates to the technical field of rock mechanics analys.The method comprises the steps that a three-dimensional geologic model and a three-dimensional geomechanical attribute model of a target sequestration body are constructed; based on the three-dimensional geologic model, establishing an oil reservoir numerical simulation model of the CO2 injection and storage process, and simulating to obtain a reservoir pressure field and a CO2 saturation field under different time steps; carrying out dynamic rock mechanics calculation to obtain dynamic fracture pressure fields of the cover layer under different time steps; and coupling the reservoir pressure field, the CO2 saturation field and the dynamic fracture pressure field, and carrying out transverse and longitudinal leakage risk dynamic evaluation. The technical problems that in the prior art, a simplified geologic model or a coarse mesh model is generally adopted, complex geologic and mechanical characteristics cannot be accurately described, the long-term stability of the storage body cannot be accurately evaluated, and the safety and long-term stability of storage are affected are solved.

Description

Technical Field

[0001] This invention relates to the field of rock mechanics analysis technology, and specifically to rock mechanics dynamic analysis methods, systems and equipment based on numerical simulation. Background Technology

[0002] CO2 sequestration technology, especially in low-permeability reservoirs, not only helps reduce atmospheric CO2 concentration but also has the potential to improve oil and gas recovery. However, the success of CO2 sequestration depends not only on the effectiveness of the technology but also on risk management during the sequestration process. Particularly during long-term sequestration, uncertainties remain regarding the risk of CO2 leakage, reservoir stability, and caprock fracturing. Currently, most CO2 sequestration studies rely on simplified geological models or coarse-grid models, which cannot accurately describe the complex geological and mechanical properties of the sequestration body. Consequently, simulation results cannot fully reflect the real situation. This problem prevents effective monitoring of CO2 injection and sequestration processes, leading to an inability to accurately assess the long-term stability of the sequestration body. Summary of the Invention

[0003] This application provides a method, system, and equipment for dynamic analysis of rock mechanics based on numerical simulation, which aims to solve the technical problem that existing technologies typically use simplified geological models or coarse grid models, which cannot accurately describe complex geological and mechanical properties, resulting in the inability to accurately assess the long-term stability of the sealed body and affecting the safety and long-term stability of the sealed body.

[0004] The first aspect disclosed in this application provides a dynamic rock mechanics analysis method based on numerical simulation. The method includes: constructing a three-dimensional geological model and a three-dimensional geomechanical property model of the target storage body; establishing a reservoir numerical simulation model of the CO2 injection and storage process based on the three-dimensional geological model, and simulating the reservoir pressure field and CO2 saturation field at different time steps; performing dynamic rock mechanics calculations based on the three-dimensional geomechanical property model and the reservoir pressure field to obtain the dynamic fracture pressure field of the caprock at different time steps; and coupling the reservoir pressure field, CO2 saturation field, and dynamic fracture pressure field to perform dynamic evaluation of lateral and vertical leakage risks.

[0005] The second aspect of this application discloses a rock mechanics dynamic analysis system based on numerical simulation. The system is used in the aforementioned rock mechanics dynamic analysis method based on numerical simulation. The system includes: a model building module for constructing a three-dimensional geological model and a three-dimensional geomechanical property model of the target reservoir; a numerical simulation module for establishing a reservoir numerical simulation model of the CO2 injection and storage process based on the three-dimensional geological model, and simulating the reservoir pressure field and CO2 saturation field at different time steps; a mechanical calculation module for performing dynamic rock mechanics calculations based on the three-dimensional geomechanical property model and the reservoir pressure field to obtain the dynamic fracture pressure field of the caprock at different time steps; and a risk assessment module for coupling the reservoir pressure field, CO2 saturation field, and dynamic fracture pressure field to perform dynamic assessment of lateral and vertical leakage risks.

[0006] The third aspect disclosed in this application provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the rock mechanics dynamic analysis method based on numerical simulation in the first aspect.

[0007] One or more technical solutions provided in this application have at least the following beneficial effects: By establishing a three-dimensional geological model and a three-dimensional geomechanical property model of the target storage body, and combining this with reservoir numerical simulation, the dynamic changes of the pressure field and CO2 saturation field over time after CO2 injection into the storage body can be simulated, thus providing decision support for actual storage operations. By combining the concepts of fluid potential and potential gradient from hydrocarbon migration theory, the migration direction and accumulation zone of CO2 can be analyzed. This method can identify the flow path and accumulation zone of CO2 within the storage body, providing a reliable basis for predicting lateral CO2 leakage risks and avoiding potential CO2 leakage risks. Furthermore, by using reservoir pressure field and three-dimensional geological model... Dynamic rock mechanics calculations based on the geomechanical property model can obtain the dynamic changes in the fracture pressure field of the caprock of the sealed body. This calculation method, combined with reservoir pressure field data at time steps, assesses the fracture pressure of the caprock and further identifies potential vertical leakage risk zones during the sealing process. By coupling the reservoir pressure field, CO2 saturation field, and caprock dynamic fracture pressure field, a dynamic evaluation system for lateral and vertical leakage risks is established, making the risk assessment during the sealing process more comprehensive. It can simultaneously consider different scenarios of lateral and vertical leakage and conduct a more accurate assessment of the stability of the sealed body through spatiotemporal correlation.

[0008] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the rock mechanics dynamic analysis method based on numerical simulation provided in the embodiments of this application.

[0010] Figure 2 A schematic diagram of the structure of a rock mechanics dynamic analysis system based on numerical simulation provided in this application embodiment.

[0011] Figure 3 This is a schematic diagram of the structure of an exemplary computer device provided in an embodiment of this application.

[0012] Figure labeling: Model building module 10, numerical simulation module 20, mechanical calculation module 30, risk assessment module 40, bus 300, receiver 301, processor 302, transmitter 303, memory 304, bus interface 305. Detailed Implementation

[0013] This application provides a method, system, and device for dynamic analysis of rock mechanics based on numerical simulation. It solves the technical problem that the existing technology usually uses simplified geological models or coarse grid models, which cannot accurately describe complex geological and mechanical properties, resulting in the inability to accurately assess the long-term stability of the sealed body, thus affecting the safety and long-term stability of the sealed body.

[0014] After introducing the basic principles of this application, various non-limiting embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0015] Example 1, as Figure 1 As shown in the embodiments of this application, a dynamic rock mechanics analysis method based on numerical simulation is provided, the method comprising: Construct a three-dimensional geological model and a three-dimensional geomechanical property model of the target sealed body.

[0016] Information on the lithology (e.g., sandstone, shale), thickness, and geological structure (e.g., faults, folds) of the target reservoir body is obtained. This data is typically derived from seismic exploration, drilling data, and geological studies. Mechanical properties such as elastic modulus, Poisson's ratio, and compressive strength of different lithologies within the target reservoir body are measured. Based on the stratigraphic distribution data, a three-dimensional mesh is generated from the target reservoir body using a meshing method, with each mesh cell corresponding to a small region within the reservoir. Based on the three-dimensional geological model and combined with the measured mechanical parameters, the finite element method is used to simulate and initialize the geostress field, ultimately completing the construction of a three-dimensional geomechanical property model. This model reflects the mechanical properties, deformation characteristics, and stress state of the reservoir and caprock.

[0017] Based on the aforementioned three-dimensional geological model, a reservoir numerical simulation model of the CO2 injection and storage process was established, and the reservoir pressure field and CO2 saturation field at different time steps were simulated.

[0018] Based on a three-dimensional geological model, a reservoir numerical simulation model is established to simulate the entire process of CO2 injection and sequestration. This process is based on fluid dynamics equations and a multiphase flow model, simulating the migration, distribution, and changes of CO2 within the reservoir. Multiple monitoring points are set up in the reservoir numerical simulation model, evenly distributed across different regions of the reservoir. The depth and location of each monitoring point must match the reservoir thickness. These monitoring points are used to record pressure values ​​and CO2 content data at various times during the simulation. The reservoir numerical simulation model is started and simulation calculations are performed according to the set time steps. After each time step, the reservoir pressure and CO2 content data at each monitoring point are recorded. Kriging interpolation is used to interpolate the pressure data across the entire reservoir to generate a reservoir pressure field. Inverse distance weighted interpolation, combined with the CO2 content and reservoir pore volume data at each monitoring point, is used to generate a CO2 saturation field.

[0019] Based on the three-dimensional geomechanical property model and the reservoir pressure field, dynamic rock mechanics calculations are performed to obtain the dynamic fracture pressure field of the caprock at different time steps.

[0020] Mechanical property parameters were extracted from a three-dimensional geomechanical property model, and reservoir pressure field data were extracted from the reservoir pressure field. A three-dimensional mechanical calculation model of the caprock was established. The boundary conditions of the model were set as follows: the pressure of the overlying strata was applied to the top of the caprock, and the reservoir pressure at the contact point with the reservoir at the bottom was applied. The lateral boundaries were set as displacement constraint boundaries. Stress-strain calculations were performed through finite element analysis to obtain the stress distribution of the caprock. Using the Mohr-Coulomb strength criterion and combined with the compressive strength parameters of the caprock rocks, the fracture pressure of the caprock at different locations was calculated, and a dynamic fracture pressure field of the caprock was generated. Through this process, the risk and changes of caprock fracture can be dynamically analyzed.

[0021] By coupling the reservoir pressure field, CO2 saturation field, and dynamic fracture pressure field, a dynamic assessment of lateral and longitudinal leakage risks is performed.

[0022] Spatial coordinates of the reservoir pressure field, CO2 saturation field, and dynamic fracture pressure field are unified to establish spatiotemporal correlations among them, ensuring that data from these three fields can be coupled and compared within the same coordinate system. Based on these spatiotemporal correlations, horizontal and vertical coupling trends are established, including horizontal and vertical coupling trends. A pre-defined horizontal leakage assessment mechanism is invoked to dynamically evaluate horizontal leakage risk based on the horizontal three-field coupling trends. This mechanism relies on factors such as reservoir pressure, CO2 saturation, and caprock fracture pressure to determine the existence of horizontal leakage risk. Similarly, a pre-defined vertical leakage assessment mechanism is invoked to dynamically evaluate vertical leakage risk based on the vertical three-field coupling trends. This mechanism focuses on caprock fracture pressure; if the fracture pressure exceeds the actual reservoir pressure, a vertical leakage risk exists.

[0023] Furthermore, the construction of a three-dimensional geological model and a three-dimensional geomechanical property model of the target sealed body includes: Acquire stratigraphic distribution data including the lithology, thickness, and geological structure of the target deposit body; determine mechanical parameters including the elastic modulus, Poisson's ratio, and compressive strength of rocks of different lithologies in the target deposit body; combine the stratigraphic distribution data to perform three-dimensional meshing of the target deposit body using a meshing method to generate a three-dimensional geological model of the target deposit body; based on the three-dimensional geological model and the mechanical parameters, perform three-dimensional geostress field simulation and initialization using the finite element method to complete the construction of the three-dimensional geomechanical property model.

[0024] Stratigraphic lithology includes rock types such as sandstone, shale, and carbonate rocks. This information helps determine the physical properties and porosity of each rock layer. Stratigraphic thickness affects subsequent mesh generation, as thicker strata require more detailed meshing to improve model accuracy. Geological structures include structural information such as faults, folds, and fracture zones around the target containment body. These geological structures affect the CO2 migration path and the integrity of the caprock.

[0025] The elastic modulus measures the ability of a rock to deform under stress. It is directly related to the rock's stiffness and resistance to deformation. It is typically measured using uniaxial compression tests or triaxial tests to obtain the rock's strain response under different stress conditions and calculate the elastic modulus. Poisson's ratio is the ratio of lateral deformation to longitudinal deformation of a rock under compression or tension, reflecting the rock's deformation characteristics under stress. It is calculated using stress-strain curves and is usually determined in conjunction with the elastic modulus. Compressive strength is the maximum stress a rock can withstand under compression and is a key parameter for assessing the risk of rock fracture. It is determined using uniaxial compression tests or triaxial tests to measure the rock's fracture strength under different pressures. These mechanical parameters are used in subsequent mechanical simulations to ensure that the physical response of the rock strata is accurately reflected in the three-dimensional geomechanical property model.

[0026] Based on data such as stratigraphic lithology, stratigraphic thickness, and structural features, a meshing strategy for different regions was determined. For complex geological areas, such as fault zones or areas with drastic lithological changes, smaller mesh cells are needed to capture details; for areas with gentle lithological changes or no obvious structural features, larger mesh cells can improve computational efficiency. A meshing method was adopted to divide the target reservoir area into multiple mesh cells, each representing a small block of the reservoir. The size of the mesh cells is inversely proportional to the geological complexity; the mesh is finer in complex areas and larger in simple areas, thus balancing computational accuracy and efficiency. Through meshing, a three-dimensional geological model of the target reservoir was generated, including information such as stratigraphic interfaces and lithological distribution. This model provides a foundation for subsequent rock mechanics calculations and reservoir numerical simulations.

[0027] Based on a three-dimensional geological model and combined with measured rock mechanical parameters, a three-dimensional geostress field simulation is performed using the finite element method. The simulation results can reflect the stress distribution of the target reservoir under natural conditions and identify potential stress concentration areas and stress anomaly areas. After the geostress field simulation is completed, initialization is performed, i.e., setting the initial stress state of the model to ensure that the stress changes reflected in the simulation are based on real geological conditions. During initialization, it is necessary to ensure that the reservoir pressure and caprock pressure are consistent with the actual situation, and that all mechanical parameters are consistent with the measured experimental data. By combining the geostress field with lithology and mechanical parameters, a complete three-dimensional geomechanical property model is finally constructed. This model will provide important data support for subsequent dynamic rock mechanics calculations, especially for evaluating the deformation and fracture behavior of rock strata during CO2 injection.

[0028] Furthermore, the target sealed body is subjected to three-dimensional mesh partitioning using a meshing method, including: The geological complexity of different regions of the target sealed body is identified, and geological complexity distribution information is established; the grid size is dynamically adjusted based on the geological complexity distribution information, wherein the grid size is inversely proportional to the geological complexity.

[0029] The geological complexity of different regions is assessed based on their geological characteristics (such as lithological variations and structural features). Geological complexity is quantified through changes in lithological variation rates, geological structural features, and physical properties such as porosity and permeability. For example, geological structural features such as faults, folds, fractures, and mineral differentiation increase the complexity of underground reservoirs, requiring finer grid division. Specifically, based on drilling data, seismic inversion data, and core analysis, the distribution of lithological variations, porosity, and permeability in different regions is analyzed to identify the complexity of different regions and establish geological complexity distribution information, which serves as input data for subsequent grid division.

[0030] Based on the geological complexity distribution information, the grid size is dynamically adjusted. For example, for areas with high geological complexity, the grid size can be reduced and a finer grid can be set, while for areas with low complexity, the grid size can be increased and a coarser grid can be set. By combining geological complexity analysis with dynamic adjustment of grid generation, the computational load can be reduced and simulation efficiency improved while ensuring simulation accuracy.

[0031] Furthermore, based on the aforementioned three-dimensional geological model, a reservoir numerical simulation model of the CO2 injection and storage process is established, and the reservoir pressure field and CO2 saturation field at different time steps are simulated, including: Multiple monitoring points are set up in the reservoir numerical simulation model. The monitoring points are evenly distributed in different regions of the reservoir, and the depth of each monitoring point matches the reservoir thickness. The reservoir numerical simulation model is started and simulation calculations are performed according to the set time steps. After each time step, the pressure values ​​and CO2 content data of each monitoring point are recorded. Based on the pressure values ​​of all monitoring points at each time step, the pressure data of the entire reservoir is interpolated using the Kriging interpolation method to generate the reservoir pressure field. Based on the CO2 content data of all monitoring points at each time step, the CO2 saturation of each monitoring point is calculated in combination with the reservoir pore volume. Then, the CO2 saturation data of the entire reservoir is interpolated using the inverse distance weighted interpolation method to generate the CO2 saturation field.

[0032] In reservoir numerical simulation, appropriate monitoring points are set up to accurately capture physical changes in the reservoir. The monitoring points are evenly distributed in different areas of the entire reservoir to ensure coverage of all important areas of the reservoir, such as the central area, edge area, top, bottom, and potential leakage channels. The uniformity of distribution ensures that full-area data of the reservoir can be obtained, avoiding distortion of local data. The depth of each monitoring point is matched with the thickness of the reservoir, that is, each monitoring point should be set in different segments of the reservoir to cover the entire reservoir thickness. This ensures that pressure and CO2 saturation data at each depth can be accurately monitored.

[0033] The simulation is performed at a set time step. The choice of time step affects the accuracy and computational efficiency of the simulation results. A shorter time step can provide higher simulation accuracy but also increases the computational burden, while a longer time step may ignore some short-term detailed changes. After each time step, the pressure and CO2 content data of each monitoring point are recorded. The pressure and CO2 content values ​​of each monitoring point reflect the reservoir state at that location.

[0034] Kriging interpolation is a spatial interpolation technique for geological data, primarily used to estimate the values ​​at unknown points. By considering the spatial correlation, or spatial autocorrelation, of measurement data points, Kriging interpolation generates estimated interpolation results. In reservoir simulation, Kriging interpolation is used to estimate the pressure distribution of the entire reservoir based on known monitoring point data, ensuring that the pressure value at each location can be reasonably estimated. Based on the monitoring point pressure values ​​at each time step, the pressure value of each grid point in the entire reservoir is calculated, thereby generating the reservoir pressure field at that moment.

[0035] CO2 saturation is calculated by dividing the CO2 content by the pore volume, which is based on the reservoir's physical parameters. Inverse distance weighted interpolation (IRW) weights data based on the distance between spatial points; closer points have higher weights, and farther points have lower weights. This simple and effective method is widely used for spatial data interpolation. In CO2 saturation interpolation, using known CO2 saturation values ​​and locations of monitoring points, IWW interpolates the CO2 saturation across the entire reservoir area, generating a complete CO2 saturation field.

[0036] Furthermore, based on the aforementioned three-dimensional geomechanical property model and the reservoir pressure field, dynamic rock mechanics calculations are performed to obtain the dynamic fracture pressure field of the underlying strata at different time steps, including: Mechanical property parameters are extracted from the three-dimensional geomechanical property model, and reservoir pressure field data are extracted from the reservoir pressure field. A three-dimensional mechanical calculation model of the caprock is established through mechanical calculation simulation, and the mechanical property parameters and reservoir pressure field data are applied to the three-dimensional mechanical calculation model. Stress and strain are calculated through finite element analysis. Based on the calculated caprock stress distribution results and combined with the compressive strength parameters of the caprock rock, the Mohr-Coulomb strength criterion is used to calculate the fracture pressure at different locations of the caprock, thereby generating the dynamic fracture pressure field.

[0037] The three-dimensional geomechanical property model contains parameters related to rock mechanics, including elastic modulus, Poisson's ratio, and compressive strength. In this step, these mechanical property parameters closely related to mechanical behavior are extracted from the three-dimensional geomechanical property model. Reservoir pressure field data is extracted from the reservoir pressure field; this pressure field data will be used as input for mechanical calculations to assess the stress state in the reservoir.

[0038] Based on the geological structural characteristics of the reservoir, a three-dimensional finite element model of the caprock is established. The physical boundary conditions, lithological distribution, and contact relationship between the caprock and the underlying reservoir need to be reflected in the model. The finite element method is a numerical method that divides a continuum into many small elements, calculates the stress and strain response of each element, and finally obtains the stress distribution of the entire structure. Here, the finite element method is used to calculate the stress and strain state of the caprock under different pressure conditions, especially the influence of reservoir pressure changes on the caprock during CO2 injection. Through finite element analysis, the stress state of each point in the caprock is obtained, including tensile stress, compressive stress, and the deformation caused by these stresses. The calculation results provide a basis for subsequent fracture analysis.

[0039] The caprock stress distribution data obtained through finite element analysis can reveal the stress state at different locations within the caprock, with particular attention paid to areas of stress concentration, which may be potential locations for caprock fracturing. High-stress areas typically correspond to weak points in the rock strata, such as faults, fractures, or areas of lithological inhomogeneity, and these areas have a higher risk of fracturing. The Mohr-Coulomb strength criterion is a commonly used criterion in rock mechanics to determine the fracturing conditions of rocks under external forces. Based on the stress distribution data obtained from finite element calculations, the Mohr-Coulomb strength criterion is applied to each calculation point to calculate the fracturing pressure. When the pressure exceeds a certain critical value, the caprock may fracture. Based on the calculation results, a dynamic fracturing pressure field map covering the entire reservoir is generated, reflecting fracturing risk zones at different locations within the reservoir and helping to identify areas where vertical CO2 leakage may occur.

[0040] Furthermore, when establishing a three-dimensional mechanical calculation model of the caprock, the boundary conditions of the model are set according to the lithological distribution characteristics of the caprock. The overlying strata pressure is applied to the top boundary of the caprock, the reservoir pressure at the time step is applied to the bottom boundary of the caprock at the contact point with the reservoir, and the side boundary of the caprock is set as a displacement constraint boundary.

[0041] The lithological distribution characteristics of the caprock include rock types, elastic modulus, compressive strength, and other mechanical parameters in different regions. Since these properties vary spatially, these variations must be considered when setting boundary conditions to ensure calculation accuracy. Boundary conditions in the three-dimensional mechanical calculation model determine the simulation method of mechanical behavior. Setting reasonable boundary conditions ensures that the simulation reflects the actual geomechanical processes. Boundary conditions include top, bottom, and lateral boundary conditions. The top boundary of the caprock applies pressure from the overlying strata. This pressure can be calculated using the gravity pressure of the strata or estimated based on known geological data. A common calculation method is to obtain the pressure value at the top based on the thickness and density of the overlying strata. The pressure at the bottom boundary is based on the reservoir pressure field data, which varies with time steps. Reservoir pressure data at different time steps are obtained through reservoir numerical simulation. In each time step simulation, the pressure value at the bottom boundary should be consistent with the reservoir pressure. In the finite element model, the lateral boundaries are set as displacement constraints, meaning that the nodes of these boundaries cannot undergo relative displacement. This constraint is set based on actual geological conditions, such as the contact mechanical characteristics between the caprock and adjacent strata.

[0042] Furthermore, by coupling the reservoir pressure field, CO2 saturation field, and dynamic fracture pressure field, a dynamic assessment of lateral and vertical leakage risks is performed, including: Spatial coordinates of the reservoir pressure field, CO2 saturation field, and dynamic fracture pressure field are unified to establish a spatiotemporal correlation among them. Based on the spatiotemporal correlation, lateral three-field coupling trends and longitudinal three-field coupling trends are established for the reservoir pressure field, CO2 saturation field, and dynamic fracture pressure field, respectively. A preset lateral leakage judgment mechanism is invoked to evaluate the lateral three-field coupling trends, completing a dynamic evaluation of lateral leakage risk. A preset longitudinal leakage judgment mechanism is invoked to evaluate the longitudinal three-field coupling trends, completing a dynamic evaluation of longitudinal leakage risk.

[0043] Spatial coordinate unification means ensuring that the coordinate systems used for the reservoir pressure field, CO2 saturation field, and dynamic fracture pressure field are consistent. For example, all data points should be aligned according to the same three-dimensional grid system to facilitate comparison and analysis. In dynamic simulations, reservoir pressure, CO2 saturation, and fracture pressure change over time. Therefore, in addition to spatial coordinate alignment, it is also necessary to correlate the data for each field with the corresponding time step.

[0044] Lateral coupling refers to how three fields (pressure field, CO2 saturation field, and fracture pressure field) interact in the horizontal plane (lateral direction) of the reservoir. Specifically, it involves analyzing the changing trends of the three fields in the lateral direction. For example, in areas with higher pressure, CO2 will migrate to these areas, leading to an increase in CO2 saturation. Areas with higher CO2 saturation will exert greater pressure on the caprock, and stress concentration may lead to fracture. By combining the changes in these three fields, trends in gas migration, reservoir pressure changes, and fracture potential in the lateral direction of the reservoir can be predicted.

[0045] Vertical coupling focuses on the interactions within the reservoir along the vertical direction (from bottom to top). The fracture pressure of the caprock is closely related to the reservoir pressure and CO2 saturation vertically. Therefore, the interaction of these fields also needs to be analyzed vertically. Specifically, vertical analysis focuses on the relationship between the upper and lower boundaries of the reservoir and the caprock. Vertically, reservoir pressure affects the stress state of the caprock. After CO2 injection, pressure changes may lead to caprock fracture, especially in thinner caprocks or areas with excessively high pressure. CO2 saturation may also change vertically, which is directly related to CO2 accumulation or leakage paths. By coupling these vertical data, possible vertical leakage paths and fracture zones can be identified, thereby assessing the fracture risk.

[0046] Lateral leakage risk typically occurs when gas leaks from the reservoir into the surrounding rock formations through lateral fractures or uneven areas. A pre-set lateral leakage assessment mechanism can identify areas with high lateral leakage risk by analyzing the coupling trend of reservoir pressure, CO2 saturation, and fracture pressure. Specifically, by analyzing the lateral coupling trend, high-risk areas are identified, such as areas with excessively high pressure, excessively high CO2 saturation, or fracture pressure close to the actual pressure. The lateral leakage assessment mechanism is then applied, including setting critical pressure, CO2 saturation threshold, and fracture pressure threshold, to evaluate whether leakage risk exists. This process helps predict whether CO2 will leak laterally from the reservoir.

[0047] Vertical leakage typically occurs between the reservoir and caprock. CO2 can enter the upper strata or surrounding rock formations through fractured or heterogeneous caprock. Vertical leakage assessment mechanisms determine potential leakage paths based on the coupling trend of the reservoir's pressure field, CO2 saturation field, and fracture pressure field. For example, if the caprock is highly likely to fracture, CO2 may migrate upwards along the fracture path. In the vertical direction, based on the dynamic changes in fracture pressure, potential caprock fracture locations are identified, and CO2 migration paths are analyzed. Combined with existing fracture pressure fields, this allows for an assessment of areas prone to vertical leakage, enabling the development of appropriate sequestration strategies.

[0048] Furthermore, the spatial coordinate unification of the reservoir pressure field, CO2 saturation field, and dynamic fracturing pressure field also includes: If there is a mismatch between the three-dimensional grid nodes of the reservoir pressure field, CO2 saturation field and dynamic fracture pressure field, the grid re-subdivision technique is used to adjust the grid so that the error of the adjusted grid nodes does not exceed the preset error threshold.

[0049] When grid mismatches exist among these fields, grid re-division is performed to ensure spatial coordinate uniformity. Grid re-division refers to readjusting the grid division within a certain error range so that data from different fields can match at the same grid nodes. Specifically, the grids of reservoir pressure field, CO2 saturation field, and dynamic fracture pressure field are compared. By comparing the depth, position, and size of grid nodes, specific mismatched grid regions are identified. For mismatched grid regions, grid re-division technology is used to re-divide the data. During this process, the adjustment range is determined according to a preset error threshold, which is typically determined by the simulation accuracy requirements, ensuring that the error of the adjusted grid nodes does not exceed the set range. To smoothly connect the grids of different regions, interpolation methods are used to ensure a smooth transition of data from each field. By accurately adjusting the grid division of different fields, the consistency and reliability of data can be ensured when performing dynamic assessments of lateral and vertical leakage risks.

[0050] Example 2, based on the same inventive concept as the numerical simulation-based dynamic analysis method for rock mechanics in the preceding examples, such as... Figure 2 As shown in the embodiment of this application, a dynamic rock mechanics analysis system based on numerical simulation is provided. The system includes: The model building module 10 is used to construct a three-dimensional geological model and a three-dimensional geomechanical property model of the target storage body; the numerical simulation module 20 is used to establish a reservoir numerical simulation model of CO2 injection and storage process based on the three-dimensional geological model, and simulate the reservoir pressure field and CO2 saturation field at different time steps; the mechanical calculation module 30 is used to perform dynamic rock mechanics calculations based on the three-dimensional geomechanical property model and the reservoir pressure field to obtain the dynamic fracture pressure field of the caprock at different time steps; the risk assessment module 40 is used to couple the reservoir pressure field, CO2 saturation field and the dynamic fracture pressure field to perform dynamic assessment of lateral and vertical leakage risks.

[0051] Furthermore, the model building module 10 is used to perform the following operation steps: Acquire stratigraphic distribution data including the lithology, thickness, and geological structure of the target deposit body; determine mechanical parameters including the elastic modulus, Poisson's ratio, and compressive strength of rocks of different lithologies in the target deposit body; combine the stratigraphic distribution data to perform three-dimensional meshing of the target deposit body using a meshing method to generate a three-dimensional geological model of the target deposit body; based on the three-dimensional geological model and the mechanical parameters, perform three-dimensional geostress field simulation and initialization using the finite element method to complete the construction of the three-dimensional geomechanical property model.

[0052] Furthermore, the model building module 10 is used to perform the following operation steps: The geological complexity of different regions of the target sealed body is identified, and geological complexity distribution information is established; the grid size is dynamically adjusted based on the geological complexity distribution information, wherein the grid size is inversely proportional to the geological complexity.

[0053] Furthermore, the numerical simulation module 20 is used to perform the following operation steps: Multiple monitoring points are set up in the reservoir numerical simulation model. The monitoring points are evenly distributed in different regions of the reservoir, and the depth of each monitoring point matches the reservoir thickness. The reservoir numerical simulation model is started and simulation calculations are performed according to the set time steps. After each time step, the pressure values ​​and CO2 content data of each monitoring point are recorded. Based on the pressure values ​​of all monitoring points at each time step, the pressure data of the entire reservoir is interpolated using the Kriging interpolation method to generate the reservoir pressure field. Based on the CO2 content data of all monitoring points at each time step, the CO2 saturation of each monitoring point is calculated in combination with the reservoir pore volume. Then, the CO2 saturation data of the entire reservoir is interpolated using the inverse distance weighted interpolation method to generate the CO2 saturation field.

[0054] Furthermore, the mechanical calculation module 30 is used to perform the following operation steps: Mechanical property parameters are extracted from the three-dimensional geomechanical property model, and reservoir pressure field data are extracted from the reservoir pressure field. A three-dimensional mechanical calculation model of the caprock is established through mechanical calculation simulation, and the mechanical property parameters and reservoir pressure field data are applied to the three-dimensional mechanical calculation model. Stress and strain are calculated through finite element analysis. Based on the calculated caprock stress distribution results and combined with the compressive strength parameters of the caprock rock, the Mohr-Coulomb strength criterion is used to calculate the fracture pressure at different locations of the caprock, thereby generating the dynamic fracture pressure field.

[0055] Furthermore, when establishing a three-dimensional mechanical calculation model of the caprock, the boundary conditions of the model are set according to the lithological distribution characteristics of the caprock. The overlying strata pressure is applied to the top boundary of the caprock, the reservoir pressure at the time step is applied to the bottom boundary of the caprock at the contact point with the reservoir, and the side boundary of the caprock is set as a displacement constraint boundary.

[0056] Furthermore, the risk assessment module 40 is used to perform the following operational steps: Spatial coordinates of the reservoir pressure field, CO2 saturation field, and dynamic fracture pressure field are unified to establish a spatiotemporal correlation among them. Based on the spatiotemporal correlation, lateral three-field coupling trends and longitudinal three-field coupling trends are established for the reservoir pressure field, CO2 saturation field, and dynamic fracture pressure field, respectively. A preset lateral leakage judgment mechanism is invoked to evaluate the lateral three-field coupling trends, completing a dynamic evaluation of lateral leakage risk. A preset longitudinal leakage judgment mechanism is invoked to evaluate the longitudinal three-field coupling trends, completing a dynamic evaluation of longitudinal leakage risk.

[0057] Furthermore, the risk assessment module 40 is used to perform the following operational steps: If there is a mismatch between the three-dimensional grid nodes of the reservoir pressure field, CO2 saturation field and dynamic fracture pressure field, the grid re-subdivision technique is used to adjust the grid so that the error of the adjusted grid nodes does not exceed the preset error threshold.

[0058] Through the foregoing detailed description of the rock mechanics dynamic analysis method based on numerical simulation, those skilled in the art can clearly understand the rock mechanics dynamic analysis system based on numerical simulation in this embodiment. Since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and relevant parts can be referred to the method section.

[0059] Example 3, as Figure 3 The diagram shown is a structural schematic of an exemplary computer device according to this application. Figure 3In this document, the bus architecture is represented by bus 300. Bus 300 may include any number of interconnected buses and bridges, and bus 300 connects various circuits including one or more processors represented by processor 302 and memory represented by memory 304. Bus 300 may also connect various other circuits such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and therefore will not be described further herein. Bus interface 305 provides an interface between bus 300 and receiver 301 and transmitter 303. Receiver 301 and transmitter 303 may be the same element, i.e., a transceiver, providing a unit for communicating with various other devices over a transmission medium. Processor 302 is responsible for managing bus 300 and general processing, while memory 304 can be used to store data used by processor 302 during operation.

[0060] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0061] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for dynamic analysis of rock mechanics based on numerical simulation, characterized by, The method comprises: constructing a three-dimensional geological model and a three-dimensional geomechanical attribute model of the target seal body; based on the three-dimensional geological model, establishing a reservoir numerical simulation model of the CO2 injection and storage process, and simulating to obtain the reservoir pressure field and the CO2 saturation field at different time steps; based on the three-dimensional geomechanical attribute model and the reservoir pressure field, performing dynamic rock mechanics calculation to obtain the dynamic fracture pressure field of the cap rock at different time steps; coupling the reservoir pressure field, the CO2 saturation field and the dynamic fracture pressure field, performing dynamic evaluation of the horizontal and vertical leakage risk.

2. The numerical simulation-based rock mechanics dynamic analysis method of claim 1, wherein, Constructing a three-dimensional geological model and a three-dimensional geomechanical attribute model of the target seal body comprises: obtaining stratum distribution data including the lithology, thickness and geological structure of the target seal body; determining the mechanical measurement parameters including the elastic modulus, Poisson's ratio and compressive strength parameters of rocks of different lithology of the target seal body; combining the stratum distribution data, performing three-dimensional grid division on the target seal body in a grid division manner to generate a three-dimensional geological model of the target seal body; based on the three-dimensional geological model and the mechanical measurement parameters, performing three-dimensional stress field simulation and initialization by using the finite element method to complete the construction of the three-dimensional geomechanical attribute model.

3. The numerical simulation-based rock mechanics dynamic analysis method of claim 2, wherein, Performing three-dimensional grid division on the target seal body in a grid division manner comprises: identifying the geological complexity of different regions of the target seal body to establish geological complexity distribution information; based on the geological complexity distribution information, dynamically adjusting the grid size, wherein the grid size is inversely proportional to the geological complexity.

4. The numerical simulation-based rock mechanics dynamic analysis method of claim 1, wherein, Based on the three-dimensional geological model, a reservoir numerical simulation model of the CO2 injection and storage process is established, and the reservoir pressure field and the CO2 saturation field at different time steps are simulated, comprising: setting multiple monitoring points in the reservoir numerical simulation model, the monitoring points being uniformly distributed in different regions of the reservoir, and the depth of each monitoring point matching the thickness of the reservoir; starting the reservoir numerical simulation model, performing simulation calculation according to the set time step, and recording the pressure value and CO2 content data of each monitoring point after each time step; based on the pressure value of each monitoring point at each time step, performing pressure data interpolation calculation on the whole reservoir by using the Kriging interpolation method to generate the reservoir pressure field; based on the CO2 content data of each monitoring point at each time step, calculating the CO2 saturation of each monitoring point in combination with the reservoir pore volume, and then performing CO2 saturation data interpolation calculation on the whole reservoir by using the inverse distance weighted interpolation method to generate the CO2 saturation field.

5. The numerical simulation-based rock mechanics dynamic analysis method of claim 1, wherein, Based on the three-dimensional geomechanical attribute model and the reservoir pressure field, dynamic rock mechanics calculation is performed to obtain the dynamic fracture pressure field of the cap rock at different time steps, comprising: extracting the mechanical attribute parameters in the three-dimensional geomechanical attribute model, and extracting the reservoir pressure field data in the reservoir pressure field; through mechanical calculation simulation, establishing a three-dimensional mechanical calculation model of the cap rock, and applying the mechanical attribute parameters and the reservoir pressure field data to the three-dimensional mechanical calculation model for stress and strain calculation by finite element analysis; According to the calculated caprock stress distribution results, in combination with the compressive strength parameters of the caprock, the dynamic fracture pressure field of the caprock at different positions is generated by using the Mohr-Coulomb strength criterion.

6. The numerical simulation-based rock mechanics dynamic analysis method of claim 5, wherein, When establishing the three-dimensional mechanical calculation model of the caprock, the boundary conditions of the model are set according to the lithological distribution characteristics of the caprock, wherein the overburden pressure is applied to the top boundary of the caprock, the reservoir pressure at the time step is applied to the bottom boundary of the caprock in contact with the reservoir, and the displacement constraint boundary is set to the side boundary of the caprock.

7. The numerical simulation-based rock mechanics dynamic analysis method of claim 1, wherein, The reservoir pressure field, the CO2 saturation field and the dynamic fracture pressure field are coupled to perform dynamic evaluation of the horizontal and vertical leakage risks, including: The spatial coordinates of the reservoir pressure field, the CO2 saturation field and the dynamic fracture pressure field are unified, and the time-space correlation relationship among the three fields is established; Based on the time-space correlation relationship, the horizontal three-field coupling trend and the vertical three-field coupling trend are respectively established for the reservoir pressure field, the CO2 saturation field and the dynamic fracture pressure field; The preset horizontal leakage judgment mechanism is called to evaluate the horizontal three-field coupling trend, and the dynamic evaluation of the horizontal leakage risk is completed; The preset vertical leakage judgment mechanism is called to evaluate the vertical three-field coupling trend, and the dynamic evaluation of the vertical leakage risk is completed.

8. The numerical simulation-based rock mechanics dynamic analysis method of claim 7, wherein, The spatial coordinates of the reservoir pressure field, the CO2 saturation field and the dynamic fracture pressure field are unified, and the time-space correlation relationship among the three fields is established; If there is a mismatch among the three-dimensional grid nodes of the reservoir pressure field, the CO2 saturation field and the dynamic fracture pressure field, the grid is adjusted by using the grid re-meshing technology, so that the error of the adjusted grid nodes is not greater than the preset error threshold.

9. A rock mechanics dynamic analysis system based on numerical simulation, characterized by, The system for implementing the rock mechanics dynamic analysis method based on numerical simulation according to any one of claims 1-8, the system comprising: a model construction module for constructing a three-dimensional geological model and a three-dimensional geomechanical attribute model of a target seal; a numerical simulation module for establishing a reservoir numerical simulation model of a CO2 injection and storage process based on the three-dimensional geological model, and simulating to obtain a reservoir pressure field and a CO2 saturation field at different time steps; a mechanical calculation module for performing dynamic rock mechanics calculation based on the three-dimensional geomechanical attribute model and the reservoir pressure field to obtain a dynamic fracture pressure field of the caprock at different time steps; a risk evaluation module for coupling the reservoir pressure field, the CO2 saturation field and the dynamic fracture pressure field to perform dynamic evaluation of horizontal and vertical leakage risks. 10.A computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the computer device is configured to perform the method according to any one of claims 1-9. The processor executes the computer program to implement the steps of the rock mechanics dynamic analysis method based on numerical simulation according to any one of claims 1-8.

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