Natural discharge related geothermal evaluation of carbonate ranges, example of Transdanubian Range, Hungary

Reservoir, heat and fluid should be investigated for the study area during reconnaissance phase of a fluid-based geothermal exploration. Without proper borehole information the determination and evaluation of reservoir, especially heat and fluid are quite complicated. In turn, springs, which are natural discharge points of flow systems, can reflect the subsurface flow and temperature conditions, therefore they can provide information about the groundwater flow pattern and temperature conditions. Namely, characteristics of springs and their areal distribution can be indicative for gravity-driven groundwater flow systems, as well as geothermal potential via their outflowing water volume and temperature. Geothermal potential of the Transdanubian Range, Hungary was examined based on the results of multidimensional data analysis of natural springs. The modifying effect of geological build-up and basin geometry on groundwater flow and heat pattern, with special emphasis of heat accumulation for geothermal utilization, was analyzed by numerical simulations. The geothermal interpretation of the previous studies, statistical data analysis and numerical simulation led to the conclusion that siliciclastic cover is responsible for heat accumulation in carbonates therefore position of unconfined and confined parts is decisive in geothermal heat utilization in carbonates.