Thermal Modeling of an Area West of the Mt. Amiata Geothermal Field, Italy

Abstract

Mount Amiata, a quiescent quaternary volcano located in Tuscany, central Italy, hosts a high enthalpy water-dominated geothermal field which has been exploited for electricity generation since the 60s’. The current Mt. Amiata power-stations installed capacity is 88 MWe. The thermal anomaly, however, extends on an area much wider than that currently exploited: we focused our modeling on a peripheral area, west of the Bagnore geothermal field, where thermal and gravity surveys highlighted a probable continuity of the geothermal features at depth. Numerical simulations of coupled groundwater flow and heat transfer have been performed to define the thermal field and to evaluate the possibility of future development of medium-high enthalpy geothermal applications in an area not yet exploited. The model domain extends over an area 34 (width) by 8 (thickness) km. Gridding specifications are based on interpreted seismic profiles and deep exploratory geothermal wells located in the nearby geothermal field, which allow temperature control down to about 4 km. The numerical modeling was performed considering various boundary conditions, inner geometries and hydraulic permeabilities. Several sets of simulations were carried out, with different bottom boundary temperatures and different hydraulic permeability and thermal conductivity values for the various layers. The aim was to compare the sensitivity of the numerical results to the variation of selected parameters.