hydrogeological characterization of a geothermal system: the case of the thermo-mineral area ofmondragone (campania, italy)

this paper dealswith thermo-mineral groundwater of themondragone plain (campania, southernitaly) and the possibility to use this low enthalpy geothermal resource. in the nw sector of this plain, at thebottom of mt. pizzuto, near the sea, there are thermo-mineral waters (50 °c) of sodium-chloride type,sulfureous and rich in co2 whose recharge is from the mt. pizzuto groundwater body. in the se sector of theplain, close to the calcareous mt. petrino, a 80 m deep well has intercepted, in the carbonate basement of theplain, thermo-mineral groundwater (33 °c), sulfureous and rich in co2, as in the nw sector, but displaying acalcium-bicarbonate composition. the chemical and the isotopic analyses allowed to verify that these typesof groundwater are due both to meteoric waters infiltration and to enrichment of endogenous co2 and h2s, atfairly high temperature. in the petrinum well, the gases involve “connate waters”, affecting upwards thegroundwater body of mt. petrino. moreover, the rising of the gases increases the dissolution of the carbonateaquifer, determining very high values of hco3 ions in the thermo-mineral groundwater. in the case of mt.pizzuto, the upwelling gas intercepts also evaporitic formation and, probably, causes saltwater intrusion. theupwelling of the gases occurs along the major fault that crosses ne-sw the plain of mondragone. finally, theunderstanding of the mineralization patterns allowed to identify in the plain the best location for a geothermalexploration well.