A model of permeability and porosity in the different type of basement of the Upper Rhine Graben inferred from outcropping analogues rocks

Abstract

To reach to suitable temperature for electricity production with geothermal fluids in non-volcanic areas, many EGS projects are bought to target the basement rocks of continental rifts as the Upper Rhine Graben. Unconfortunately these basements and their reservoir properties are not well known and investigations from the surface cannot currently detect important parameters like the basement lithology or faults barrier/conduit behaviour. This study proposes an analysis of the reservoir properties of outcropping analogues of different basement rocks of the URG in order to characterize their reservoir potential. Thus, different petrophysical measurements have been performed on “fresh”, meteoric weathered or weathered in damaged zones and fault cores samples for the different lithologies outcropping in the Northern Vosges Mountains. These analysis allow the classification of the basement’s reservoirs in different groups: from the most interesting with a high potential of development, characterized by high matrix permeability and porosity due to weathering to the low matrix porosity reservoir rock but high permeability in the fault zones.