Modelling of the stress field: from regional to reservoir scale

Because of its rifting setting, the Upper Rhine Graben (URG) shows great potential for implementing Enhanced/Engineered Geothermal Systems (EGS). Based on structural observations (GeORG team, 2013), a fault zone north of Vendenheim, among other structures, could be an interesting target. However, this first estimate must be validated prior to any drilling, and numerical simulations can provide arguments within this context. In this study, we focus on this first step by assessing the stresses around the fault, before any anthropic perturbation are added. The URG is an intraplate area with low deformation (e.g. Nocquet, 2012). We have few information on the stress field at the local scale. To overcome this barrier, we model the stress field at the regional scale to get information at the reservoir scale. This regional model is validated by the few stress data available in this region. Modelling of regional stresses deals with large dimensions (length of hundreds of kilometres). When such large scales are considered, the modelled rock masses are cut by major fault zones that affect the overall mechanical behaviour. Because these fault zones must be accounted for in the modelling (Yale, 2003), we choose to use a discrete fracture network approach in our model.