State of Stress at the European HDR Candidate Sites Urach and Soultz

Abstract

The operational costs of long-tern1 HDR operations are determined by energy demand for the underground fluid circulaticn as well as by fluid losses during circulation. both factors are controlled by in-situ stresses at depth. Therefore in-situ stress measurements are important parts of feasibility studies at the locations for a future European HDK prototype Bad Urach and Soultz-sous-Forets. The results of numerous hydrofrac stress measurements yield at Bad Urach a compressive tectonic stress regime, at Soultz-sous-Forets a normal-faulting stress regime. At both sites a N-S to NNW-SSE orientation of the maximum horizontal compression was observed, which is in accordance with the tectonic situation in Central Europe.