Rock Property Mapping for Improved Planning of Geothermal Installations

Abstract

A major hindrance for the exploration of geothermal energy is the high risk of failure due to the unknown properties of the target rocks at depth. Usually, con-servative assumptions are made about these proper-ties, resulting in larger drilling depths and increased exploration costs. We systematically study hydraulic and thermal properties for the Molasse Basin, a re-gion in Southern Germany, in order to improve this situation. This should allow building of better models of geothermal installations in the planning stage.

For this purpose a combination of laboratory meas-urements and well log interpretation is used. Labora-tory data provides the basis of the study by providing the petrophysical properties, measured on a represen-tative collection of samples obtained from outcrops and boreholes in that area. Measured properties en-compass thermal conductivity and diffusivity as well as porosity and permeability. Variations arising from temperature and pressure increase with depth are studied. Logging data add knowledge about the prob-lem by developing relationships linking core and wireline measurements as well as delineating geo-graphical regions of different petrophysical facies type. A major aspect is the use of data from aban-doned hydrocarbon exploration wells, establishing an additional data source to constrain the problem.