Geoelectric Survey of Hydraulic Experiments at the German Deep Drilling Site KTB at KM-Scale

One of the major findings of the German Continental Deep Drilling Program was the evidence of free fluids down to a depth of nearly ten kilometres. Furthermore, a series of hydraulic experiments in the pilot borehole focused on the characterization of transport processes of fluids in crystalline crust were carried out. Because of the significant differences of the electrical conductivity between the investigated fluids (natural free saline fluids and artificially inserted fresh water), geoelectrical methods are qualified for a successful detection in the kilometre scale. The Fluid Pump Test (2002/03 – production of about 22,300 cubic metres of saline formation fluids) or the Fluid Injection Test (2004/05 – injection of about 84,600 cubic metres of fresh water) clearly indicate a decreasing respectively an increasing in electrical resistivity. Inhole-logs in the open hole section (3,850 m – 4,000 m) could give a first indication (very closed to the pilot borehole) of consequence of the producing of saline formation fluids respectively of the fluid inflow displaced by injected fresh water last year. Also in greater distances to the pilot borehole, the time course of the decreasing (2003) and of the increasing of the apparent resistivity (2005) could be measured by geoelectrical combined surface-hole-experiments.