Using Surface SP to Monitor Underground Fluid Flow - an Example from a HDR Stimulation

P113 USING SURFACE SP TO MONITOR UNDERGROUND FLUID FLOW - AN EXAMPLE FROM A HDR STIMULATION Abstract 1 We have carried out monitoring of surface electric potential (SP) variations around the Soultzsous-Forêts Hot Dry Rock (HDR) site (France) during a stimulation experiment where 23 000 m 3 of water were injected at 5 km depth. We have observed a long-period (T > 1 day) SP variation with a maximum amplitude of 4 mV strongly correlated to the injection: this anomalous potential increases during the injection and decreases after shut-in. We interpret this behaviour as being caused by the electrokinetic effect