3D geological modelling of a fractured carbonate reservoir for the study of medium enthalpy geothermal resource in the Southern Apennines (Campania Region, Italy)

A characterization of medium enthalpy geothermal resources has been carried out in the Southern Apennines "Guardia Lombardi" site (Campania Region, Italy) within the framework of the Vigor Project. Due to the intense hydrocarbon exploration carried out in Italy since the '50, a wide public dataset of well data and seismic reflection profiles is available for the study site. Moreover, a scientific cooperation with the ENI Italian Oil Company has been established in order to access to more detailed dataset also including wells information and core samples. A three-dimensional geological model of the reservoir-caprock system has been developed through an integrated interpretation of the available geological, geophysical, hydrogeological and geochemical information in the study area. The geothermal reservoir of "Guardia Lombardi" site is constituted by the Cretaceous-Eocene fractured shallow water carbonates belonging to the Apulian platform. Such units have been structured in a buried antiformal stack during the Apennine orogenesis. The reservoir fluids are mainly composed of CO2, which rests above of brackish water in the central part of the deep carbonatic aquifer culmination (i.e., Monte Forcuso 1 well). Conversely along the flanks of the buried anticline (e.g., Bonito 1 Dir, Ciccone 1 wells) the reservoir fluids consist of saline water, not showing any free gas phase. The temperature of this fluids recorded into the reservoir are 120-125°C at the depth of about 3000 m below the ground level (e.g. Bonito 1 well). Given the quite good permeability of the fractured carbonate rocks, numerical simulation performed in this work estimated that a water production of about 13.5-20 kg/s might be achieved according to the chosen technical solution (a single production well vs production- reinjection doublet). Results confirm that the "Guardia Lombardi" site represents an interesting area for the exploitation of this medium enthalpy geothermal resource.