Low-Enthalphy Geothermal Reservoirs Exploration in the Apennines Buried Thrust Front South of Parma (Italy)

In the study area the geothermal reservoir has been recognized in the turbidite Miocene deposits covered by the Pliocene-Quaternary marine and alluvial deposits. These turbidites, here considered the local substrate, are coarse-grained sandstones saturated by saline waters. The heat-flow from the Miocene substrate to the overlying fresh-water saturated sediments varies primarily as a function of the reservoir depth: from ten meters (Monticelli Terme) to a few hundred meters (Collecchio) and several hundred meters (Madregolo) below ground surface. In the culminations of the positive structure the temperatures detected in the Miocene reservoir vary from 40 to 50°C. The temperatures measured in the overlying fresh-water aquifer are highly variable. At Monticelli Terme the alluvial Late Pleistocene aquifer has a temperature around 20°C. Temperature estimates show that the geothermal gradient in the thrust crest zone (4.7°C/100m) is about twice the gradient in the areas south and north (2.2°C/100m). Accordingly, the heat-flow is higher in the saturated alluvial sediments covering the thrust crest and front (0.06-0.07 W/m²) than in the alluvial wedge to the north (0.04 W/m²).