A Comparison of Hydraulic Stimulation Experiments at the Soultz, France and Coso, California Engineered Geothermal Systems

Abstract

Hydraulic stimulation experiments were conducted on tight injection wells at the Soultz-sous-Forets, France and the Coso, California geothermal systems. Significant improvements in injectivity were observed at both reservoirs, although lower stimulation pressures and less fluid were required in order to achieve better injectivity for the Coso well. Following the stimulation experiments, circulation tests were conducted and hydraulic communication was confirmed through tracer testing. The tracer data were analyzed in order to compare the tracer-swept pore volume and the relative degree of dispersion within each stimulated reservoir. The tracer data indicate greater dispersion and therefore a possibly more extensive fracture network at Soultz, although the stimulated-fracture-volume appears to be greater at Coso.