Geothermal potential of Sedimentary Basins, especially of the Swiss Molasse Basin

Abstract

Sedimentary basins usually have significant geothermal potential. Deep aquifers are key components. The factors, conditions, and processes that define and control the potential are: processes during basin formation like sedimentation, karstification, fracturing; rock porosity, permeability/fluid content; depth/temperature; hydrogeology; production sustainability. They are demonstrated on selected examples: USA basins, Paris Basin, Molasse Basin. Of the latter, the French, German and Austrian parts are treated first and then the Swiss Molasse Basin (SMB) in more detail.The various efforts undertaken to assess and quantify the SMB potential are described, example maps presented. The realizations of the SMB potential so far are really modest: of 10 deep drilling projects performed in various locations to date only one is successful, two are a partial success. The official Swiss energy strategy EN2050 includes electricity supply in the future; this assigns 4.4 TWh to geothermal sources in 2050. This would be delivered from geothermal power plants, foreseen are 250 MWe installed capacity from hydrothermal reservoirs and another 250 MWe from petrothermal (EGS) sources. Only the SMB could host hydrothermal resources; the current data don’t make much hope. In principle, EGS plants could take heat (and convert it to electricity) from below the SMB. The EGS technology itself has great potential but it is still in the proof of concept stage. Intensive R&D is ongoing in several countries, however, very substantial funding will be needed to answer the many questions still open.