Hydrogeological Characterization of a Geothermal system: the case of the Thermo-mineral area ofMondragone (Campania, Italy)

Abstract

This paper dealswith thermo-mineral groundwater of theMondragone plain (Campania, southern<br />Italy) and the possibility to use this low enthalpy geothermal resource. In the NW sector of this plain, at the<br />bottom of Mt. Pizzuto, near the sea, there are thermo-mineral waters (50 °C) of sodium-chloride type,<br />sulfureous and rich in CO2 whose recharge is from the Mt. Pizzuto groundwater body. In the SE sector of the<br />plain, close to the calcareous Mt. Petrino, a 80 m deep well has intercepted, in the carbonate basement of the<br />plain, thermo-mineral groundwater (33 °C), sulfureous and rich in CO2, as in the NW sector, but displaying a<br />calcium-bicarbonate composition. The chemical and the isotopic analyses allowed to verify that these types<br />of groundwater are due both to meteoric waters infiltration and to enrichment of endogenous CO2 and H2S, at<br />fairly high temperature. In the Petrinum well, the gases involve “connate waters", affecting upwards the<br />groundwater body of Mt. Petrino. Moreover, the rising of the gases increases the dissolution of the carbonate<br />aquifer, determining very high values of HCO3 ions in the thermo-mineral groundwater. In the case of Mt.<br />Pizzuto, the upwelling gas intercepts also evaporitic formation and, probably, causes saltwater intrusion. The<br />upwelling of the gases occurs along the major fault that crosses NE-SW the plain of Mondragone. Finally, the<br />understanding of the mineralization patterns allowed to identify in the plain the best location for a geothermal<br />exploration well.