Development of a regional geothermal resource atlas

Increased interest in geothermal energy has led to the need for more sophisticated analyses of available geothermal resources for heating and power production. The evaluation methods have traditionally used 1D models, but progress in computing power allows us now to perform joint interpretations that include large-scale effects of geological, topographical and hydrogeological structures. This paper describes the steps taken in such an integrated assessment. The evaluation of geothermal potential is actually finalized for one of the most populated areas of Switzerland. The methodology accounts for individual utilization scenarios and is based on various temperature data that have been systematically collected over many years. The state-of-the-art compilation involves comprehensive 3D regional geological and thermal models. An excellent data fit with >20 boreholes in northern Switzerland is achieved using the calculation scheme presented here. Zones of significant convective flow are identified and the flow velocity is quantified. In contrast to the results obtained from earlier geothermal resource assessments, the existing geological, hydrogeological and petrophysical data are included in the full 3D numerical evaluation. The results obtained for a regional scale of a well-documented subsurface area in northern Switzerland are displayed in terms of geothermal productivity and energy. The calculations identify the topmost crystalline basement as a most promising structure for geothermal exploitation with predicted maximum doublet productivities of >100 MWt. The annually extractable energy of 13 PJ km(-3) easily covers a broad range of Swiss energy needs. The atlas can be further expanded to cover utilization schemes not treated here, such as ground-coupled heat pump systems.