A Modeling Method for CFD Computational Domain in Complex Terrain and a System for Simulating Carbon Dioxide Leakage and Risk Assessment in Geological Storage

Abstract

The present invention belongs to the technical field of carbon peak and carbon neutrality, and specifically relates to a method for modeling a CFD calculation domain in complex terrain and a simulation and risk assessment system for CO2 leakage in geological storage. The modeling method can simply achieve three-dimensional modeling of complex terrain such as loess hillock and ridge areas through data conversion. The simulation and risk assessment system includes a CO2 exposure concentration acquisition module, a CO2 exposure reference concentration module, a health risk assessment module, and a visualization module for the spatio-temporal distribution of health risks. The simulation and risk assessment system based on this modeling has good visualization characteristics and realizes rapid, highly operable, high-precision, and highly visual CCUS potential leakage risk assessment.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon peak and carbon neutrality, and specifically relates to a method for modeling a CFD calculation domain in complex terrain and a system for simulating CO2 leakage and risk assessment in geological storage. Background Art

[0002] Carbon capture, utilization, and storage (CCUS) is an economical and effective measure to address global climate change. However, due to the lack of understanding of the potential hazards of its potential leakage, it is likely to trigger public panic and rejection of CCUS, becoming one of the main obstacles to the large-scale promotion of CCUS. A certain oilfield in the northwest region, one of the CCUS pilot demonstration bases in China, belongs to the typical loess hill and gully landform. It is of great significance to comprehensively describe the route, the scope of potential carbon dioxide leakage, and the hazard level in the demonstration project area for the promotion of CCUS technology.

[0003] 69.1% of the terrain in China is mountainous, and the reservoir storage areas where CCUS pilot demonstration projects are located mostly belong to the loess hill and gully landform. This complex terrain will significantly affect the diffusion of leaked gas, resulting in an increase in the data uncertainty of the risk assessment concentration source. There are several major problems in the risk assessment of CCUS leakage in the loess hill and gully landform: there is no available threshold data and evaluation model for CO2; it is difficult to model the CFD calculation domain for gas diffusion simulation under complex terrain; the public awareness of the risk characterization method is poor. Therefore, developing a CO2 health risk assessment method, a complex terrain calculation domain method, and a risk characterization method closer to the actual scenario is of great significance for the safe and efficient implementation of CCUS pilot projects and large-scale promotion and application.

[0004] At present, there are the following ways for CFD simulation and risk assessment of gas diffusion in complex terrain / landform: (1) Importing scanned point cloud data into SURFER software and outputting it to ANSYS GAMBIT software, and generating a somewhat simplified mountainous terrain by point / line / surface / volume editing in ANSYS GAMBIT; (2) Using SKETCH UP to assist in establishing a three-dimensional model of buildings and docking with ICEM to generate a CFD calculation domain, and realizing the visualization of the diffusion simulation results in ARCGIS by using the coordinate data conversion method; (3) Using the risk matrix method to carry out semi-quantitative risk assessment of potential leakage and hazard risks of CCUS-sequestered CO2.

[0005] Although the above methods can achieve the risk assessment of CCUS for CO2 sequestration to a certain extent and may provide reference for the simulation of CO2 leakage and diffusion, the pre-processing software GAMBIT has been deactivated in the new version of the ANSYS system; the single SKETCH UP software can only draw a small number of buildings or software with low complexity; the risk matrix method is based on the factor weight matrix and can provide risk levels under simple conditions. However, the subjective judgment is too rich, the risk classification range is limited, and it cannot respond appropriately to the actual environmental parameters, with extremely low accuracy. Moreover, none of the above methods have yet achieved the CFD three-dimensional computational domain modeling for complex terrains such as the loess hill and gully area, as well as the simulation and risk assessment of geological sequestration of CO2 leakage.

[0006] Therefore, developing a series of convenient CO2 health risk assessment methods, complex terrain computational domain methods, highly visual and popular risk characterization methods, systematically identifying various leakage sources and leakage scenarios from the overall perspective of CCUS projects, constructing CFD three-dimensional computational domain modeling, as well as the simulation and risk assessment of geological sequestration of CO2 leakage, are important measures to solve the current CCUS risk management problems in China. Summary of the Invention

[0007] The object of the present invention is to provide a complex terrain CFD computational domain modeling method and a simulation and risk assessment system for geological sequestration of CO2 leakage in view of the problems of complex diffusion simulation modeling, lack of objectivity in risk assessment criteria, and low visualization and popularity of risk characterization in the existing CCUS sequestration leakage risk assessment and management for complex terrains, especially the loess hill and gully landform. The modeling method can simply achieve three-dimensional modeling of complex terrains such as the loess hill and gully area through data conversion. The simulation and risk assessment system based on this modeling has good visualization characteristics, and realizes the CCUS potential leakage risk assessment with high speed, high operability, high accuracy and high visualization.

[0008] The technical solution of the present invention is: a complex terrain CFD computational domain modeling method, comprising the following steps:

[0009] (1) Import the digital terrain elevation model image source data of the area to be studied into the Global Mapper software, set the model coordinate system and projection standard according to the regional longitude and latitude and the coordinate system of the image source data, and use the "Draw" command to delineate the outer boundary of the study area; use the "Analysis" and "Generate Contours Based on TIN" commands to generate the three-dimensional contour model of the area to be studied; use the "Export" and "Vector Radar Format" to output the primary digital graphics of the three-dimensional contour.

[0010] (2) Open the primary digital graph of the 3D contour lines exported in step (1) using AUTO CAD software. Use the "3D View" and "Dynamic Constraint Rotation" commands to view and delete unclosed lines and single points that are not at the highest / lowest elevation. Use the "Output" command to generate a smooth and closed 3D contour line digital graph.

[0011] (3) Import the 3D contour line digital graph exported in step (2) using SketchUp software. Use the "Sandbox" and "Surface Undulation" commands to convert the 3D contour line digital graph into a terrain 3D surface model. Use Auto CAD software to perform simple 3D modeling according to the preset buildings and structures, and export the 3D solid model of the buildings and structures.

[0012] (4) Import the terrain 3D surface model and the 3D solid model of the buildings and structures in step (3) using Rhinoseros software. Use the "Boolean Split", "Boolean Difference", and "Boolean Intersection" commands to cut the non-computation domain part of the 3D solid model to achieve seamless docking of the 3D solid model of the buildings and structures and the terrain 3D surface model, and generate a real 3D surface model including the terrain and the buildings and structures. Use the "Plumb Line" command to generate the four-direction boundaries of the study area, use the "Cap" command to close the top of the model to form a hollow 6-sided combined model, and use the "Solid" command to solidify the hollow 6-sided combined model to generate a 3D solid computation domain model.

[0013] In step (1), the image source data of the digital terrain elevation model of the area to be studied uses the ASTER GDEM remote sensing satellite data version V3. The spatial resolution of this data is 30m, and the format is tiff. The model coordinate system and projection standard are Mercator projection, using the World Geodetic System 1984 projection coordinate system and the Beijing80 coordinate system. The 3D contour line model is generated based on the same elevation base point.

[0014] In step (3), the 3D solid model of the buildings and structures is formed by stretching the plane wireframe model drawn according to the actual coordinate positions of the buildings and structures, and its size is consistent with the measured size of the buildings and structures.

[0015] The primary digital graph of the 3D contour lines is in dxf format; the 3D contour line digital graph is in dwg format; the terrain 3D surface model is in skp format; the 3D solid model of the buildings and structures is in dxf format; the 3D solid computation domain model is in prasolid format.

[0016] A geological storage CO2 leakage simulation and risk assessment system based on the obtained three-dimensional entity computational domain model includes a CO2 exposure concentration acquisition module, a CO2 exposure reference concentration module, a health risk assessment module, and a health risk spatio-temporal distribution visualization module. Among them, the CO2 exposure concentration acquisition module is used to obtain the CO2 exposure concentration at each receptor point under different leakage scenarios based on the three-dimensional entity computational domain model. The CO2 exposure reference concentration module is used to obtain the CO2 exposure concentration reference value based on toxicological analysis. The health risk assessment module is used to obtain the point cloud data of the CO2 exposure health risk coefficient at each spatial point under different leakage scenarios. The health risk spatio-temporal distribution visualization module is used to obtain a highly visualized image integrating terrain, landform, land use, and receptor health risk information.

[0017] The CO2 exposure concentration acquisition module first imports the three-dimensional entity computational domain model into ANSYS ICEM for mesh division, and then imports the divided mesh into ANSYS FLUENT for gas diffusion simulation, so as to obtain the CO2 exposure concentration at each receptor point under different leakage scenarios.

[0018] The mesh division uses hexahedral meshes, and the "local refinement" command of ANSYS ICEM software is used to refine the spatial units within a range of 200 m around the buildings. The gas diffusion simulation of ANSYS FLUENT uses the k-ε turbulence model.

[0019] The CO2 exposure concentration reference value obtained by the CO2 exposure reference concentration module based on toxicological analysis is shown in Table 1.

[0020] Table 1 CO2 exposure concentration reference value

[0021] 。

[0022] The health risk assessment module uses the quotient method to batch calculate the ratio of the CO2 exposure concentration at the receptor points obtained by the CO2 exposure concentration acquisition module to the CO2 exposure concentration reference value obtained by the CO2 exposure reference concentration module through EXCEL software, that is, to obtain the point cloud data of the CO2 exposure health risk coefficient at each spatial point under different leakage scenarios.

[0023] The spatio-temporal distribution visualization module of the health risk uses SURFER software to perform Kriging interpolation on the XY coordinates of the receptor point spatial plane and the CO2 exposure health risk coefficient, that is, to obtain the spatial distribution map of the receptor health risk caused by different CO2 leakage scenarios. The "Export" command is used to export the spatial distribution map of the receptor health risk as a kml format file. Opening the kml format file with GOOGLEEARTH software will obtain a highly visualized image integrating information such as terrain, landform, land use, and receptor health risk. The "Fly" command can be used to browse the details of the risk distribution and the spatial distribution trend, and thus the potential hazard risk of CO2 leakage in the loess hilly and gully geologic sequestration can be studied. The coordinate system of the kml file is WGS1984.

[0024] The beneficial effect of the present invention is that the complex terrain CFD computational domain modeling method of the present invention aims at the problem of difficult three-dimensional computational domain modeling for complex terrain at present. Based on four general commercial software, namely GLOBAL MAPPER, AUTO CAD, SKETCH UP, and RHINOCEROS, a three-dimensional modeling method for complex terrain is established. Only 1-2 steps of operation are required for a single software, and rapid and accurate modeling of complex terrain can be achieved through simple graphic editing, which has high applicability and popularization.

[0025] The geological sequestration CO2 leakage simulation and risk assessment system based on the three-dimensional solid computational domain model aims at the problem that there is no publicly available exposure concentration threshold and risk calculation model for the current CO2 human health risk assessment. Based on toxicological analysis, international literature retrieval and data analysis methods are adopted to establish the threshold data of CO2 exposure concentration and exposure duration at different hazard levels, and on this basis, a mathematical model for CO2 exposure human health risk assessment is established using the generally recognized quotient method in health risk assessment. The risk level of the receptor can be judged through simple concentration comparison. The data is reliable and the calculation is simple. It can be used not only for CCUS risk assessment, but also for the assessment of other potential CO2 exposure risks.

[0026] The above-mentioned assessment system also aims at the problem that the current method for visualizing the large-area risk of the engineering site uses the engineering drawing as the base map and simply superimposes the risk spatial distribution. This method makes the residents unclear about the risk assessment conclusion and cannot effectively relieve the panic psychology of the residents about the inability to cope with potential leakage. This system innovatively adopts the spatial data superposition method, directly imports the risk assessment results into the general earth system visualization software GOOGLEEARTH through the conversion of point cloud coordinate data, and forms a risk distribution map with highly visualized representation of the risk assessment results, which can greatly promote the residents' understanding of the spatio-temporal distribution and evolution of potential leakage and associated risks of CCUS, enhance their ability to respond to risks, and completely eliminate the panic psychology of the residents about CCUS.

[0027] In summary, the modeling method of the present invention can achieve rapid three-dimensional modeling of complex terrains such as loess hill and gully regions; the simulation and risk assessment system integrates the quantitative assessment of the leakage risk of geological CO2 storage and the visual representation of the risk level, realizing rapid, highly operable, highly accurate, and highly visual CCUS potential leakage risk assessment. It is not only convenient for engineering design and risk prevention and control, but also can improve the residents' identification and awareness of potential risks, and has high applicability and popularization potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the overall framework of the modules and model development included in the embodiments of the present invention.

[0029] Figure 2 It is the topographic image data map box within the preset range of the storage area and its vicinity in the embodiments of the present invention.

[0030] Figure 3 It is a smooth and closed three-dimensional contour digital image in dwg format in the embodiments of the present invention.

[0031] Figure 4 It is a three-dimensional surface model in skp format in the embodiments of the present invention.

[0032] Figure 5 It is a real three-dimensional surface model of the terrain and buildings and structures in the embodiments of the present invention.

[0033] Figure 6 It is the ANSYS FLUENT receptor point CO2 exposure concentration image in the embodiments of the present invention.

[0034] Figure 7 It is the risk index spatio-temporal visualization image in GOOGLE EARTH in the embodiments of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The present invention will be described in detail below with reference to the accompanying drawings.

[0036] The modeling method for the CFD calculation domain of the complex terrain includes the following steps:

[0037] (1) Obtain the topographic image data within the preset range of the storage area and its vicinity. The source data of the topographic image is the ASTER GDEM remote sensing satellite data version V3. The spatial resolution of this data is 30 m, and the format is tiff. Refer to Figure 2Import the topographic image source data into the Global Mapper (Blue Marble Geographic Inc. v.19) software. Set the model coordinate system and projection standard according to the regional longitude and latitude and the coordinate system of the image source data. Use the "Draw" command to delineate the outer boundary of the study area. Use the "Analysis" and "Generate Contours Based on TIN" commands to generate a three-dimensional contour model of the area to be studied. Use the "Export" and "Vector Radar Format" commands to output the primary digital graphics of the three-dimensional contours. The model coordinate system and projection standard are Mercator projection, using the World Geodetic System 1984 projection coordinate system and the Beijing80 coordinate system. The three-dimensional contour model is generated based on the same elevation base point.

[0038] (2) Open the primary digital graphics of the three-dimensional contours in dxf format exported in step (1) using AUTO CAD software. Use the "3D View" and "Dynamic Constraint Rotation" commands to view and delete unclosed lines and single points that are not at the highest / lowest elevation. Use the "Output" command to generate smooth and closed three-dimensional contour digital graphics. Figure 3 .

[0039] (3) Import the three-dimensional contour digital graphics in dwg format exported in step (2) into SketchUp software (Trimble Inc. v.2018). Use the "Sandbox" and "Surface Undulation" commands to convert the three-dimensional contour digital graphics into a terrain three-dimensional surface model in skp format. Figure 4 ; Use Auto CAD software to perform simple three-dimensional modeling according to the preset buildings and structures, and export a three-dimensional solid model of the buildings and structures in dxf format. The three-dimensional solid model of the buildings and structures is formed by stretching a plane wireframe model drawn according to the actual coordinate positions of the buildings and structures, and its size is consistent with the measured size of the buildings and structures.

[0040] (4) Import the terrain three-dimensional surface model in skp format and the three-dimensional solid model of the buildings and structures in dxf format exported in step (3) into Rhinoseros (v6.0) software. Use the "Boolean Split", "Boolean Difference" and "Boolean Intersection" commands to cut the non-computation domain part of the three-dimensional solid model to achieve seamless docking of the three-dimensional solid model of the buildings and structures and the terrain three-dimensional surface model, and generate a real three-dimensional surface model containing the terrain and the buildings and structures. Figure 5 ; Use the "Plumb Line" command to generate the four-direction boundaries of the study area. Use the "Cap" command to close the top of the model to form a hollow 6-sided combined model. Use the "Solid" command to solidify the hollow 6-sided combined model to generate a three-dimensional solid computation domain model in parasolid format.

[0041] A geological sequestration CO2 leakage simulation and risk assessment system based on the obtained three-dimensional solid computational domain model, including a CO2 exposure concentration acquisition module, a CO2 exposure benchmark concentration module, a health risk assessment module, and a health risk spatio-temporal distribution visualization module.

[0042] The CO2 exposure concentration acquisition module: First, import the three-dimensional solid computational domain model in parasolid format into ANSYS ICEM for mesh generation, and then import the generated mesh into ANSYS FLUENT for gas diffusion simulation, so as to obtain the CO2 exposure concentration at each receptor point under different leakage scenarios. Refer to Figure 6 . Among them, hexahedral meshes are used for mesh generation, and the "local refinement" command of ANSYS ICEM software is used to refine the spatial units within a range of 200 m around the buildings; the k-ε turbulence model is used for the gas diffusion simulation in ANSYS FLUENT.

[0043] The CO2 exposure benchmark concentration module: Obtain the CO2 exposure concentration benchmark value based on the collation of literature experimental data and toxicological analysis.

[0044] The literature experimental data are the data published in domestic and foreign authoritative journals during the period from 2001 to 2020. The list of directly cited references is shown in Tables 2 and 3 below.

[0045] Table 2 CO2 exposure concentration benchmark value and references

[0046] .

[0047] Table 3 Details of references

[0048] .

[0049] The health risk assessment module: Adopt the quotient method, and batch calculate the ratio of the CO2 exposure concentration at the receptor points obtained by the CO2 exposure concentration acquisition module to the CO2 exposure concentration benchmark value obtained by the CO2 exposure benchmark concentration module through EXCEL software, that is, obtain the point cloud data of the CO2 exposure health risk coefficients at each spatial point under different leakage scenarios.

[0050] The health risk spatio-temporal distribution visualization module: Use SURFER software to perform Kriging interpolation on the XY coordinates of the receptor point spatial plane and the CO2 exposure health risk coefficient, that is, obtain the spatial distribution map of receptor health risks caused by different CO2 leakage scenarios. Use the "Export" command to export the spatial distribution map of receptor health risks as a kml format file. Open the kml format file using GOOGLEEARTH software to obtain a highly visualized image integrating information such as terrain, landform, land use, and receptor health risks. Use the "Fly" command to browse the details of the risk distribution and the spatial distribution trend, and then be able to study the potential hazard risks of CO2 leakage in the loess hill and gully geomorphic geological storage, refer to Figure 7 ; where the coordinate system of the kml file is WGS1984.

Claims

1. A method for modeling a CFD calculation domain in complex terrain, characterized in that, It includes the following steps: (1) Import the digital terrain elevation model image source data of the area to be studied into the Global Mapper software. Set the model coordinate system and projection standard according to the regional longitude and latitude and the coordinate system of the image source data. Use the "Draw" command to delineate the outer boundary of the study area; use the "Analysis" and "Generate Contours Based on TIN" commands to generate the three-dimensional contour model of the area to be studied; use the "Export" and "Vector Radar Format" commands to output the primary digital graphics of the three-dimensional contours. (2) Use the AUTO CAD software to open the primary digital graphics of the three-dimensional contours exported in step (1). Use the "3D View" and "Dynamic Constraint Rotation" commands to view and delete the unclosed lines and single points that are not at the highest / lowest elevation; use the "Output" command to generate smooth and closed three-dimensional contour digital graphics. (3) Use the SketchUp software to import the three-dimensional contour digital graphics exported in step (2). Use the "Sandbox" and "Surface Undulation" commands to convert the three-dimensional contour digital graphics into a terrain three-dimensional surface model; use the Auto CAD software to perform simple three-dimensional modeling according to the preset buildings and structures, and export the three-dimensional solid model of the buildings and structures. (4) Use the Rhinoseros software to import the terrain three-dimensional surface model and the three-dimensional solid model of the buildings and structures in step (3). Use the "Boolean Split", "Boolean Difference" and "Boolean Intersection" commands to cut the non-computation domain part of the three-dimensional solid model to achieve seamless docking of the three-dimensional solid model of the buildings and structures and the terrain three-dimensional surface model, and generate a real three-dimensional surface model including the terrain and the buildings and structures; use the "Plumb Line" command to generate the four-direction boundaries of the study area, use the "Cap" command to close the top of the model to form a hollow six-sided combined model, and use the "Solid" command to solidify the hollow six-sided combined model to generate a three-dimensional solid computation domain model.

2. The CFD calculation domain modeling method for complex terrain according to claim 1, wherein In step (1), the digital terrain elevation model image source data of the area to be studied uses the ASTER GDEM remote sensing satellite data version V3. The spatial resolution of this data is 30m, and the format is tiff; the model coordinate system and projection standard are Mercator projection, using the World Geodetic System 1984 projection coordinate system and the Beijing 80 coordinate system; the three-dimensional contour model is generated based on the same elevation base point.

3. The CFD calculation domain modeling method for complex terrain according to claim 1, characterized in that In step (3), the three-dimensional solid model of the buildings and structures is formed by stretching the plane wireframe model drawn according to the actual coordinate positions of the buildings and structures, and its size is the same as the measured size of the buildings and structures.

4. The CFD calculation domain modeling method for complex terrain according to claim 1, wherein The primary digital graphics of the three-dimensional contours are in dxf format; the three-dimensional contour digital graphics are in dwg format; the terrain three-dimensional surface model is in skp format; the three-dimensional solid model of the buildings and structures is in dxf format; the three-dimensional solid computation domain model is in prasolid format.

5. A geological storage CO2 leakage simulation and risk assessment system based on the three-dimensional solid computational domain model obtained from claim 1, characterized in that, The system includes a CO2 exposure concentration acquisition module, a CO2 exposure benchmark concentration module, a health risk assessment module, and a health risk spatio-temporal distribution visualization module; among them, the CO2 exposure concentration acquisition module is used to obtain the CO2 exposure concentration at each receptor point under different leakage scenarios based on the three-dimensional solid computational domain model; the CO2 exposure benchmark concentration module is used to obtain the CO2 exposure concentration benchmark value based on toxicological analysis; The health risk assessment module is used to obtain the point cloud data of the CO2 exposure health risk coefficient at each spatial point under different leakage scenarios; the health risk spatio-temporal distribution visualization module is used to obtain a highly visualized image integrating terrain, landform, land use, and receptor health risk information.

6. The geological sequestration CO2 leakage simulation and risk assessment system according to claim 5, characterized in that, The CO2 exposure concentration acquisition module first imports the three-dimensional solid computational domain model into ANSYS ICEM for mesh division, and then imports the divided mesh into ANSYS FLUENT for gas diffusion simulation, so as to obtain the CO2 exposure concentration at each receptor point under different leakage scenarios.

7. The geological sequestration CO2 leakage simulation and risk assessment system according to claim 6, characterized in that, The mesh division uses hexahedral meshes, and the "local encryption" command of ANSYS ICEM software is used to encrypt the spatial units within a range of 200 m around the buildings; the gas diffusion simulation of ANSYS FLUENT uses the k-ε turbulence model.

8. The geological CO2 storage leakage simulation and risk assessment system according to claim 5, characterized in that The CO2 exposure concentration benchmark value obtained by the CO2 exposure benchmark concentration module based on toxicological analysis is shown in Table 1: Table 1 CO2 exposure concentration benchmark value 9. The geological CO2 sequestration leakage simulation and risk assessment system according to claim 5, characterized in that The health risk assessment module uses the quotient method to batch calculate the ratio of the CO2 exposure concentration at the receptor points obtained by the CO2 exposure concentration acquisition module to the CO2 exposure concentration benchmark value obtained by the CO2 exposure benchmark concentration module through EXCEL software, that is, to obtain the point cloud data of the CO2 exposure health risk coefficient at each spatial point under different leakage scenarios.

10. The geological CO2 storage leakage simulation and risk assessment system according to claim 5, wherein The health risk spatio-temporal distribution visualization module uses SURFER software to perform Kriging interpolation on the XY coordinates of the receptor point spatial plane and the CO2 exposure health risk coefficient, that is, to obtain the spatial distribution map of the receptor health risk caused by different CO2 leakage scenarios. The "export" command is used to export the spatial distribution map of the receptor health risk as a kml format file. Using GOOGLE EARTH software to open the kml format file, a highly visualized image integrating terrain, landform, land use, and receptor health risk and other information can be obtained. The "fly" command can be used to browse the details of the risk distribution and the spatial distribution trend, and thus the potential hazard risk of CO2 leakage in the loess hill and gully geologic sequestration can be studied; among them, the coordinate system of the kml file is WGS1984.

Images