Coupled Hydro-Mechanical Modelling of the GPK3 Reservoir Stimulation at the European EGS Site Soultz-sous-ForÍts

Abstract

By reaching the targeted reservoir depth, the European EGS project gets in its decisive state. Currently, three boreholes, (GPK2, GPK3 and GPK4) have been drilled to 5 km depth. The reservoir stimulation represents a primary challenge to all future developments. In this context, the new HEX-S code has been developed to simulate the transient hydro-mechanical response of the rock matrix to massive hydraulic injections. The present paper describes the modelling results to the GPK3 stimulation starting at May 27 2003. Maximum flow rates of >60 l/s have been used, triggering >30'000 microseismic events. The transient simulation intends to obtain a match of both, the microseismic and the hydraulic behavior. Different model calculations demonstrate the capabilities of our new approach that became also possible due to the excellent data quality at the Soultz project. Therewith, the perspectives of performing design calculations can develop in future that helps to optimize cost-intensive hydraulic stimulations. As first attempt, the effect of dual versus single injections in the surroundings of Soultz-sous-ForÍts is evaluated.