Use of Exploration Wells to Improve Geothermal Reservoir Models

Abstract

The large sedimentary basins and graben structures in Germany are regions of general interest for geothermal heat use. In our study we focus on two target areas: the eastern part of the Molasse Basin in Southern Germany and the southern and western part of North Rhine Westphalia (Niederrheinische Bucht / Rheinisches Schiefergebirge). A major obstacle in geothermal energy development lies in the high risk of failure due to the unknown thermal and hydraulic properties of the target rocks at depth. In order to improve this situation, we systematically analyze data sets from different exploration wells (oil, gas, carbon and research boreholes) and core samples. Our aim is to develop methods for rock property mapping on the reservoir scale and thus to obtain better models for geothermal installations in the planning stage. For this purpose, we apply a combination of laboratory measurements and well log interpretation. Petrophysical properties measured in the laboratory on a representative collection of samples obtained from boreholes and outcrops comprise thermal conductivity and specific heat capacity as well as porosity and permeability. Additionally, we consider the effects due to temperature and pressure increase with depth. Logging data add information with respect to spatial variations, on the one hand through relationships between core and wireline measurements, on the other hand by delineating regions of different petrophysical facies types.