ORIGINAL ARTICLE MeshIt—a software for three dimensional volumetric meshing of complex faulted reservoirs Mauro Cacace 1 • Guido Blo ¨cher 1 Received: 2 December 2014 / Accepted: 13 May 2015 Ó Springer-Verlag Berlin Heidelberg 2015 Abstract Flow, mass and energy transport processes in natural reservoirs are controlled to a large degree by the presence of geological heterogeneities including structures such as fractures and fault zones embedded in a spatially varying three-dimensional (3D) porous matrix of the reservoir. Despite recent advances, currently, state-of-the- art models rely on a number of simplifications partly re- lated to our inability to represent heterogeneities as ob- served in the field into dynamic model realizations. In this respect, an adequate geometric representation of the dis- crete system is a basic requirement. In this study, we show how fundamental concept from computational geometry can be assembled and used to bridge the gap between geological and dynamic forward models. The result is an automated, open source software solution (MeshIt) to generate quality 3D meshes suitable for the study of flow and transport processes in faulted and fractured reservoirs. The software enables us to integrate into a 3D volumetric representation dipping structures, comprising fault zones and fractures as well as inclined well paths. This permits us to correctly simulate interactions between discrete flow paths along these interacting components and the 3D flow within the reservoir matrix. The crucial factor that makes the approach applicable to real case reservoirs is that all algorithms are local and scalable parallel and have com- puting times increasing approximately linearly with data volumes. We test the performance and the robustness of the software against three different scenarios of increasing complexity and further discuss current limitations and range of applicability of the software. Although all exam- ples describe geothermal applications, it is worth men- tioning that the approach is equally valid for other applications in geoscience from oil and gas industry to carbon capture and sequestration issues. Keywords Delaunay triangulation and tetrahedralization  3D meshing  Faulted and fractured reservoirs Introduction Many petroleum, gas, geothermal and water supply reser- voirs form in fractured and faulted rock systems (Com- mittee on Fracture Characterization and Fluid Flow, National Research Council 1996). Understanding the dy- namics of processes occurring in these discrete hetero- geneities is of crucial importance for geoenergy-related applications. Depending on their geometry and orientation with respect to the in situ stress field, fault and fractures act either as preferentially hydraulic conductors or as hydraulic barriers (e.g. Davatzes and Aydin 2005). Therefore, these structures exert a primary control on the origin and de- velopment of georesources and on the flow and transport of chemical contaminants into and through the subsurface (Berkowitz 2002). As an example, reservoir management requires detailed knowledge of the reservoir behaviour and of the overall system including geological units of interest, major fault zones, natural and induced fractures and production and injection wells (e.g. Ahmed and Meehan 2011). Numerical simulations of processes occurring in such systems provide useful tools for basic process understanding and for & Mauro Cacace mauro.cacace@gfz-potsdam.de 1 Helmholtz Centre Potsdam (GFZ) German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany 123 Environ Earth Sci DOI 10.1007/s12665-015-4537-x