The role of hydrogeological conditions and thermophysical properties on the evaluation of geothermal exchange potential in Central Italy

A multidisciplinary investigation aimed at optimising low enthalpy geothermal plants in the Marche Region (Central Italy) is currently in progress. The main goal is to improve the present-day knowledge of the geological structure, the hydogeological setting and the thermophysical characters of the subsoil and to obtain a better picture of the regional geothermal exchange potential. Since the seasonal climatic variation can affect the temperature and moisture content of the shallower portion of the subsoil, we are focusing our attention on the continuous monitoring of the physical properties of groundwater (temperature and electrical conductivity above all). Moreover, recording of undisturbed temperature-depth profiles in available boreholes is underway. Meanwhile, we have started an extensive campaign of laboratory measurements of thermal conductivity, volume heat capacity, thermal diffusivity, porosity, density and permeability of the several lithologies forming the sedimentary deposits of the Umbria-Marche successions. In this paper, we present the first results so far achieved concerning the field monitoring and the laboratory experiments. These data will be fundamental for the subsequent implementations of numerical thermal models of the subsoil, which incorporate conductive and advective heat transfer and which can evaluate the behaviour of borehole heat exchangers under different hydrogeological conditions.