Applied Thermo-Hydro-Mechanical coupled modeling of geothermal prospection in the northern Oberrheingraben

Abstract

Several geothermal power plants are planned for one of the most promising regions in Germany, the Upper Rhine Graben (URG). Induced seismicity can have a strong impact on the viability of such projects. For instance at the Basel/Switzerland Deep Heat Mining site, located at the southern end of the URG, after massive hydraulic fracturing in 2006/2007 several earthquakes with magnitudes of up to 3.4 occurred. An expert report on this seismicity has led to a final stop of the project. To prevent other geothermal projects from this fate a prognostic of possible induced seismicity and measures to limit the maximum magnitude are currently one of the most important geothermal research topics. Based on a geometric GOCAD model of the German federal state Hessen, covering the northern part of the URG, a large scale heat transport model was developed. For regions where geothermal exploration is planned, coupled thermo-hydro-mechanical (THM) models can be computed. The THM modelling is based on a FEFLOW model for the thermo-hydro coupling together with a plug-in for the (linear elastic) mechanical coupling. The approach is demonstrated exemplarily for a site, using literature data