Evaluation of the Geothermal Energy Potential in the Medium-Enthalpy Reservoir Guardia Dei Lombardi, Italy

Abstract

A region in Southern Italy (Guardia dei Lombardi, Province of Avellino) is being explored as a medium-enthalpy geothermal resource. The chosen area (with overall dimensions of 42 km × 28 km) is characterized by a local heat-flux maximum of 90 mW/m2. Based on seismic profiles and hydrocarbon exploration wells, a three-dimensional geological model has been set up. It shows the upper surface of the Cretaceous Apulia shallow-water carbonate platform as a faulted, thrust-related anticline overlain by dense, partly shale-rich sedimentary layers. In previous work, the basal specific heat flow was calibrated to temperature data from six different wells under the assumption of purely conductive heat transport using the simulation code SHEMAT-Suite. The reservoir is characterized by a natural carbon dioxide emanation along natural faults and fractures. Analogously, it is assumed that water flow occurs primarily through fracture and fault networks. The role of advection on the temperature distribution is studied and a reevaluation of the basal specific heat flow at 6 km depth performed. This inversion is carried out using a deterministic Bayesian approach. Thermal conductivity values for the lithological units and their uncertainties are deduced from laboratory measurements on rock samples together with logging interpretation. Maps of geothermal energy potential are set up at various depths within the reservoir with the overall goal of identifying promising geothermal conditions for future exploitation.