Hydrothermal Alteration at the San Vito Area of the Campi Flegrei Geothermal System in Italy: Mineral Review and Geochemical Modeling

Abstract

The Campi Flegrei geothermal system sets in one of the most famous and hazardous volcanic caldera in the world. The geothermal dynamics is suspected to have a crucial role in the monitored unrest phases and in the eruption triggering as well. Numerical models in the literature do not properly consider the geochemical effects of fluid-rock interaction into the hydrothermal circulation and this gap limits the wholly understanding of the dynamics. This paper focuses on fluid-rock interaction effects at the Campi Flegrei and presents relevant information requested for reactive transport simulations. In particular, we provide: (1) an extensive review of available data and new petrographic analyses of the San Vito cores rearranged in a conceptual model useful to define representative geochemical and petrophysical parameters of rock formations suitable for numerical simulations and (2) the implemented thermodynamic and kinetic data set calibrated for the San Vito 1 well area, central in the geothermal reservoir. A preliminary 0D-geochemical model, performed with a different contribution of CO2 at high (165 °C) and low (85 °C) temperatures, firstly allows reproducing the hydrothermal reactions over time of the Campanian Ignimbrite formation, the most important deposits in the case study area.

Exploring microstructure and petrophysical properties of microporous volcanic rocks through 3D multiscale and super-resolution imaging

“…1 a). This tuff is the most widespread among the caldera-filling deposits 37 , 38 extended up to a depth of ~ 4 km 5 . It was thus investigated for numerous (mainly volcanological, geothermal, civil and material engineering) applications 3 – 5 , 26 , 29 .…”

“…Although attention must be paid to extend our results to all the types of microporous volcanic rocks, this study represents the first effort to systematically explore these “unconventional” digital rocks through digital rock physics, as well as offers a framework to deal with similar microporous structures and innovative imaging challenges (e.g., high-resolution imaging of large samples or materials to be preserved, 4D imaging with large experimental apparatus and/or high temporal resolution). Moreover, Campanian Ignimbrite tuff is thought to be one the most widespread subsurface rock at the Campi Flegrei caldera 37 , 38 , currently in a state of unrest since 2005 28 , 29 . Our findings will be employed in future studies to optimize the 3D investigation of core samples from geothermal drills in this area and time-resolved (4D) imaging during in-situ and/or ex-situ experiments to better constrain the ongoing dynamics at this large active caldera.…”

CO2 Reaction-Diffusion Experiments in Shales and Carbonates

“…The lab analysis and diffusion experiments allowed to: (i) characterize the mineralogy of cores; (ii) describe their changes related to geochemical weathering induced by CO 2 ; (iii) evaluate the velocity of CO 2 penetration into the samples; and (iv) estimate the CO 2 diffusion coefficients. Following our previous methodological approach (e.g., [15]), these results provide information to set and calibrate reliable reactive transport models useful to investigate short-to-long-term consequences of CO 2 storage and to evaluate the effect of trapping mechanisms on fluid flow [16].…”