The European HDR Project at Soultz Sous Forets: Stimulation of the Second Deep Well and First Circulation Experiments

Abstract

By February 1995 the European HDR project at Soultz was operating 6 boreholes: 2 deep hydraulic test wells (GPK-1,3590 m & GPK-2, 3876 m) and 4 seismic observation wells with depths between 1500 and 2200 m (Fig.1). In 1993 the first section of a deep underground exchanger had been created through massive stimulation (injection of some 45000 m3 of water). Between November 1994 until January 1995 a second deep well, GPK-2, was drilled at the periphery of this exchanger. A complex test programme involving the stimulation of GPK-2 (connecting it to the existing exchanger) and various circulation experiments with different production techniques (flash throttled and unthrottled, submersible pump) and varying injection rates was performed between June and August 1995.