GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 actvity (e.g., Di Luccio et al., 2022). Regarding these topics, although many structural and geological aspects of the upper and lower crust of this chain are stll unclear (e.g. Improta and Corciulo, 2006), it is overall accepted that the extensional tectonics has a primary role on CO 2 Earth degassing and that CO 2 -rich fuids of mantle-origin is distributed in concomitance of the destructve Apennines seismic sequences (e.g., Chiodini et al., 2020 and references therein). The fuids, including CO 2 , may contribute to the earthquake preparaton, nucleaton and evoluton. In the study area, the fold-and-thrust belt was under tectonic compression untl the Pleistocene and is currently under extension (e.g., Improta et al., 2003). Moreover, the chain is nowadays the site of groundwater fow, natural gas circulaton and seismicity (e.g., Fiorillo et al., 2010; Chiodini, 2014; D’Agostno et al., 2018). In partcular, the fuids migrate across the crust, moving downward and upward through the orogenic wedge, whose upper part is composed by foredeep deposits and sediments formed in shallow, transitonal, and deep-water environments. These sequences overlap with the carbonates of the Apulian Platorm. Gas emissions collected at the Meftniella, Mefte, Malvizza and Telese sites testfy that gas rises from great depths through the complex geological setng (e.g., Minissale, 2004). Moreover, in 1962 and 1980, two earthquakes of magnitude Mw>6 hit the region (Rovida et al., 2020; 2022), leading to the destructon of several municipalites in the provinces of Benevento and Avellino, and resultng in numerous fatalites, homeless people and extensive damages. In the current work, 30 exploraton wells available on open source (VIDEPI website) and drilled between 1961 and 1982 have been analysed. The pore pressures data were initally extracted from the well profles, including mud weight and formaton test pressures. Subsequently, the obtained pressures were normalized to a hydrostatc profle to beter compare the pressure values at varying depths and diferent sites. Finally, observed hydrostatc and abnormal trends were compared to the fuids found at well sites to verify possible correlatons. Approximately half of the analysed wells identfed carbon dioxide levels, either in sandy and calcareous formatons across the hole or at the botom hole reservoirs, such as the carbonates of the Apulian Platorm. Since these boreholes allow us to extract pore pressure measurements up to a depth of 6 km, these wells ofer a unique opportunity to investgate subsurface pore pressures and their interacton with the diferent fuid types (groundwater, hydrocarbons, carbon dioxide). The study unveils that the CO 2 levels found in several wells (e.g., Circello 1 and Benevento 2) within the permeable layers of the Apulian Platorm carbonates are in hydrostatc conditons, thus indicatng that the storage of CO 2 is not necessarily correlated with the overpressures. Similarly, the CO 2 gas cap found in Monte Forcuso 1 and Monte Forcuso 2 wells is in hydrostatc conditons, thus suggestng that the CO 2 rising to the surface can occur without the generaton of overpressures. In additon, moderate to high overpressured gradients are predominantly identfed within allochthonous Miocene shaly-rich sequences, including the Irpinia/Sannio Units and the formatons of the Rapolla Group, also associated with groundwater-fed levels, as evidenced by Panizza 1 and other wells.