GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.2 GNGTS 2023 Insights from well pressure data to understand the interplay among shallow and deep fluids circulation in the Irpinia area (southern Apennines, Italy) E. Vitagliano, L. Improta, L. Pizzino, N. D’Agostino Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy In the field of geothermal energy research, borehole pressure data are an important item to retrieve information on subsurface pressure distribution and thus enable an adequate assessment of reservoir’s geothermal potential and proper planning of development activities. Where possible, this information can be borrowed from the hydrocarbon exploration wells, even in those areas characterised by low petroleum potential and not supported by further scientific investigations targeting to production activities. This is the case of the Irpinia area, located in the central part of the southern Apennines (Italy), where the hydrocarbon exploration has been carried out for several decades since the 1950s, making it possible to gather geological, geochemical and geophysical information, which is nowadays available on opensource portals. The Irpinia area is also characterised by geothermal gradients ranging from 20 °C/km up to over 50° C/km and can be considered an interesting site in terms of geothermal potential, as highlighted by a recent study evaluating the medium enthalpy geothermal resources (Inversi et al., 2013). In the proposed study, indirect and direct pressure data have been collected from 30 exploration wells of the Irpinia area in order to recover pore-pressure profiles. The study aims to define the compartmentalisation of the main tectono-stratigraphic sequences of the region and to better understand the origin, pathways and interactions among the fluids involved in the orogenic belts (sedimentary fluids such as hydrocarbons, meteoric and formation waters, and deep fluids such as CO2). Although some structural and geological aspects of orogenic architecture of the upper and lower crust are still unclear (e.g., Improta & Corciulo, 2006), the presented topic is crucial for understanding the circulation of fluids from the surface to the upper crust (infiltration of meteoric water into regional karst aquifers) and from the lower crust to the surface (deep CO2 degassing, CO2 entrapment in the Apulian reservoir, gas emission at the surface), as fluids migrate across the crust moving downward and upward. Fluid flow is also a key point to clarify several issues that still remain under scientific debate, such as heat transfer, pore pressure variations and seismogenesis (e.g., Chiodini et al., 2004; Chiodini et al., 2014; Improta et al., 2014; D’Agostino et al., 2018). The preliminary results of the study shows that: (I) most of the borehole profiles are characterised by a transition from shallow hydrostatic profiles to overpressure regimes at depth; (II) in the same borehole and