Fault Control on a Thermal Anomaly: Conceptual and Numerical Modeling of a Low-Temperature Geothermal System in the Southern Alps Foreland Basin (NE Italy)

The interest on low-temperature geothermal resources is progressively increasing since their renewability and widespread availability. Despite their frequency, these resources and their development have been only partially investigated. This paper unravels the major physical processes driving a low-temperature geothermal resource in NE Italy (Euganean Geothermal System) through conceptual and numerical modeling. Dense fracturing associated to regional fault zones and a relay ramp enhances regional to local flow of thermal waters. Their rapid upwelling in the Euganean Geothermal Field is favored by open extensional fractures deforming the relay ramp. The water (65-86 degrees C) is intensively exploited for balneotherapy, rendering it a profitable resource. Three-dimensional coupled flow and heat transport numerical simulations based on this conceptual model are performed. Despite the presence of a uniform basal heat flow, a thermal anomaly corresponding to field observations develops in the modeling domain reproducing the relay ramp. Intensive fracturing extending across a wide area and a slightly anomalous heat flow favors a local increase in convection that drives the upwelling of deep-seated hot waters. The simulations corroborate and refine the conceptual model, revealing that water of up to 115 degrees C is likely to be found in the unexplored part of the thermal field. This study furthers knowledge on fault-controlled low-temperature geothermal resources where the geological setting could enhance local convection without anomalous heat flows, creating temperatures favorable for energy production. Conceptual and numerical modeling based on solid geological and hydrogeological reconstructions can offer a support tool for further detailed explorations of these prominent resources.