Pre-drilling geothermal assessment of porosity and permeability of the Bunter Sandstone Formation, onshore Denmark

Denmark constitutes a low-enthalpy geothermal area. Current geothermal production takes place from two sandstone-rich formations: the Bunter Sandstone and Gassum Formations. These formations form major potential geothermal reservoirs, but information about the permeability of the potential sandstone reservoirs is difficult to obtain. This may be explained by deposition in a variety of environments under different climatic conditions, and by variable diagenetic overprint (Olivarius et al. 2015). Thus, the sandstone characteristics and properties are diverse, and in areas where wells are scarce, the assessment of the extent and reservoir properties of sandstone layers is associated with much uncertainty. In order to reduce exploration risk it is therefore essential to develop a robust method for prediction of porosity and permeability prior to drilling.