| Abstract |
Quantification of technically usable geothermal resources of a nation has got a main factor for the planning of future energy scenarios. In the past, the resource analyses were merely based on measured and forecasted temperature distribution in subsurface. Currently, advances in computing and modeling allows the regional consideration of thermal effects (i.e. topography, 3D geology, transient effects, .) in the calculation of the subsurface temperature fields. In the assessment of the Swiss geothermal resources, the hydrogeological conditions were additionally included into the evaluation scheme. This resulted in a dynamic approach to forecast the possible geothermal productivity over a 30-year life span of a geothermal utilization scenario. Purely on the basis of measured data and numerical interpretation, the temperature field and the hydraulic transmissivity of the most important hydrogeological structures have been regionally assessed. Using these two key parameters the possible geothermal productivities were predicted for the Swiss Plateau, which represents the major populated area in Switzerland. Herein, the following aquifer systems of the Swiss Molasse Basin were considered: Upper Marin Molasse, Upper Malm, Upper Muschelkalk and fractured top crystalline basement. In each of these systems, the fault and fractured zones got special attention. The results from the geothermal resource assessment, elaborated between in the period 2000 and 2006, were now compiled in a uniform procedure to evaluate the possible areal suitability for a geothermal production. The interest of this study was to define areas for possible waste scenarios that will not conflict with future geothermal production. In this integrative approach the economic analysis for geothermal production is only of little interest since the investments required in future production is presently unknown. However, geothermal production will continuously focus on reservoirs that are accessed easier and cheaper than others. To determine possible geothermal utilization at arbitrary locations of the Swiss Molasse Basin for future production a cost model was taken that considers linearly increasing drilling costs with depth. Necessary investments for infrastructure, buildings or heat exchangers were taken to be identical. The results of this investigation are expressed by an areal distribution of a normalized productivity. Especially the areas of Northern Switzerland like the Cantons of Thurgau, Zurich and Aargau seem to be well suited for future production. In the western part of Switzerland elevated values are reached in the Canton of Vaud. |