| Title | CREATING AN UNSTRUCTURED 2.5D TOUGH2 GRID GEOMETRY CONSTRAINED TO A GEOLOGICAL MODEL |
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| Authors | R. Pearson, B. Williams, J. OBrien, T. Mitchell, T. McLennan |
| Year | 2018 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Leapfrog Geothermal, TOUGH2, AUTOUGH2, unstructured gridding, Voronoi, Delaunay |
| Abstract | Flow simulation models aim to accurately forecast the flow through porous material, enabling subsurface teams to investigate a range of possible development scenarios. The simulation provides a spatially and temporally varying model of flow over a grid. Accuracy is dependent on how well the system is described by the governing equations of the flow model, how well the grid conforms to the geology of the system, the relative resolution of the grid compared to the spatial variations in flow over the system, and how well the connections between individual grid blocks adhere to the assumptions implicit in the numerical method. TOUGH2 allows for the simulation of coupled transport of water, vapour, non-condensable gas and heat in porous material (Pruess et al., 1999). Given its application to an appropriate system, related accuracy concerns include the generation, population and visualisation of a grid that aims to conform to the underlying geology of the system. Flow simulations are also computationally intensive, which practically limits the grid resolution to ensure the model converges in a timely manner. We present tools and a workflow for creating and using an unstructured Voronoi 2.5D grid geometry in a TOUGH2 model in an attempt to better enable the reservoir simulation grid to conform to the geological units and features such as faults and well perforations within the system of interest. A Voronoi grid is used to increase the flexibility of the volume centroid locations while still adhering to the requirements of the TOUGH2’s governing equations, namely, that the connections between adjacent volumes are orthonormal (Pruess et al., 1999, Croucher et al., 2013). The workflow allows for interactively creating and iteratively refining the grid geometry. Rock types from the geological model including fault rock types are evaluated on to the grid. The TOUGH2 model created is then exported to a Mulgraph geometry file and a TOUGH2 .DAT file. |