Cost effective geothermal reservoir property prediction with legacy seismic and well data

Summary To reduce the risks of encountering unexpected poor reservoir properties in exploration for geothermal reservoirs, geophysics and in particular quantitative interpretation of legacy seismic and well data is proposed. Five seismic lines and thirty-two wells from the 80s are used to characterize the Dogger formation over, a small area of the north-east of the Paris Basin (France). The applied processing sequence is standard and aims at keeping only the amplitude variations that are related to the reservoir properties. After editing and conditioning of the logs from the geothermal and oil wells, statistical relationships are derived between impedance and porosity. Clear trends for the limestone and marl facies are identified. This combination of the seismic inversion and statistical relationships, has highlighted high porosity convex oolitic lenses characteristic of the producing geothermal bodies of the Dogger. Despite the uncertainties inherent to the use of relatively old legacy data, the workflow allows reducing exploration risks for a limited cost compared to the acquisition of new seismic data.