The construction of a geothermal power plant requires the exploration of the geothermal reservoir in the subsoil at an early stage. Rarely, geothermal phenomena such as hot springs or fumaroles are found on the earth's surface. Rather, the resource has to be explored using indirect methods and with various geoscientific techniques. In addition to the location of the reservoir in the underground, other characteristics such as, e.g., structure, temperature and geology of the reservoir have to be determined. Once the first wells have been drilled, further exploration of the deposit is pending.
Our research group uses various geophysical exploration methods:

• Magnetotelluric measurements use the natural electromagnetic field to detect subsurface electrical conductivity anomalies. These allow statements about the fluid movement in the underground as well as the occurrence of impermeable clay formations.
• The monitoring of induced micro seismicity during stimulation or drilling measures allows the evaluation of the reservoir volume. In addition, statements about the tectonic stresses in the reservoir can be made.
• Various well logging methods allow the calculation and determination of reservoir characteristics through indirect access to the reservoir. This allows an understanding of the processes taking place in the reservoir in order to optimize the management of the resource. Among other things, the fracture network, the structure of individual fractures, the permeability and geomechanical parameters can be determined.
• The interpretation of seismic datasets allows the determination of layer thicknesses and the location of fault zones.
• Hydraulic tests provide information on the permeability, the storage capacity and possibly also on the extent and nature of the reservoir.

In addition to geophysical methods, we use geochemical methods in close collaboration with the Institute of Mineralogy and Geochemistry. For this purpose, rock or fluid samples are chemically analyzed to identify processes in the reservoir. The dissolved substances can be used to determine the temperatures in the reservoir and to investigate the water-rock interaction. Isotope geochemical studies support the reservoir characterization and provide indication on the source of the waters and the degree of mixing between meteoric and deep waters. Our exploration activities are carried out in different geological regions. Amongst other, we are active in rift systems (Upper Rhine Graben), in the granitic basement (Black Forest), and in high-enthalpy regions.