Advancing knowledge of thermo-fluid dynamic processes in Vulcano's geothermal system through numerical simulations

The island of Vulcano, part of the Aeolian Archipelago, is a significant volcanic edifice in Italy. Its active geothermal system and frequent volcanic unrest, particularly the ongoing phase, since September 2021, marked by high fumarole temperatures, changes in gas composition, ground deformation, and micro-seismicity, underscore the importance of understanding the subsurface processes driving volcanic and geothermal phenomena.

The present study, using TOUGH2 code (Pruess et al., 1999), aims to enhance our understanding of the active geothermal system of Vulcano. A highly constrained petrophysical model of the island, derived from a 3D resistivity structure obtained from a magnetotelluric (MT) survey (Di Giuseppe et al., 2023), was used to simulate heat flow and fluid flow (H₂O and CO₂) for the time required to reach the natural thermodynamic state of the system. The numerical modelling results were analyzed by examining the fluid distributions in terms of pressure, temperature and CO₂ partial pressure. Pressure increases linearly with depth, as expected in a hydrostatic system, while temperature and CO₂ partial pressure show more complex distributions. These observations are consistent with a developed heterogeneous model that incorporates structural and petrophysical data from the MT model, providing a more realistic thermodynamic representation of the Vulcano geothermal system. In particular, the simulated temperature and CO₂ partial pressure distributions show a clear differentiation between the central-northern and southern parts of the island, in agreement with literature and empirical data.

These results offer new insights into the system’s behavior, significantly enhancing our understanding of its current dynamics and providing a robust foundation for predicting its future evolution. This could potentially lead to more accurate predictive models and hazard scenarios.