3D Voronoi Pre- and Post- Processing Tools for Using the Tough2 Family of Numerical Simulator for Hydrocarbon Gas Migration

The TOUGH family of multi-component, multiphase numerical reservoir simulators have a well know and a long history of applications in different fields of mass and heat transport in porous media. The use a full three-dimensional (3D) unstructured grid permits a great degree of flexibility to reproduce the geometry of complex geological formations and performs accurate reservoir numerical simulations. The full 3D Voronoi tessellation approach also allows reproducing the geometry of geological formations (useful, for example, in directional drilling). In this work, we present some applications of the 3D Voronoi pre- and post-processing software tools dedicated to the TOUGH family of codes (developed at the DICAM Department of the University of Bologna by the Geothermal research group), to study problems of gas migration in hydrocarbon reservoirs. In particular, a small set of 3D grids of a deep sedimentary formation has been created with VORO2MESH, and the simulation results analysed with TOUGH2Viewer. VORO2MESH is a software coded in C++ able to rapidly compute the 3D Voronoi tessellation for a given domain and to create a ready-to-use TOUGH2 MESH file, up to million blocks. It is based on the well-known and powerful open source voro++ library. The new extended version of the TOUGH2Viewer post-processor was used to easily inspect the 3D Voronoi discretization and to better manage the numerical simulation results. The software, written in Java, handles the visualization of both 3D grids (structured and unstructured) and simulation results. This study shows the effectiveness of these tools, and that the use of unstructured grids, instead of structured grids, substantially improve both the reproduction of the geological model and the TOUGH simulation results.