Objectif EXTENSION AT DEPTH OF THE GEOTHERMAL FIELD. The Torre Alfina geothermal field is located north of Bolsena Lake in the northern sector of the Volsini Volcanic Complex and corresponds to a structural high of Tuscan Upper Trias to Eocene prevalently carbonate formations underlying the cover made up of clayey Ligurid sequences and volcanic terrains.The well drilling was performed by the Italian Electricity Board (ENEL) National Geothermal Unit in 1987 with a MASS 6000 E rig. The goal consisted of a presumed second deeper reservoir within a depth of 4000 m. Although the objective was not achieved, test hole Alfina 15 supplied new information that, going far beyond the local interest, makes a fundamental contribution to the stratigraphic, structural and thermal knowledge of the whole region. Beneath the Ligurid cover, the well crossed 3 Tuscan tectonic units overlying, from 3545 m, an Umbrian type succession. The drilling then continued to 4826 m, beyond the envisaged depth, with the goal of intercepting the impermaeble regional basement, controlling the temperature trend and acquiring additional tectonic and stratigraphic information. For the first time, the Mesozoic carbonate formations (the main regional geothermal reservoir) were crossed for such a great thickness (approximately 3700 m), above a presumed deeper impermeable basement. The tectonic thickening of the permeable rocks constitutes a single reservoir with extremely low thermal gradients (0.2 to 0.3 C/10 m) and temperatures ranging between 140 C and 210 C. Despite simulation the well proved to be unproductive due to low local permeability. From a drilling technology point of view, the well did not present any difficulties despite the great depth never before reached in geothermal wells in Italy.A BOREHOLE TO THE TARGET DEPTH OF 3500-4000 M WILL BE DRILLED IN THE GEOTHERMAL AREA OF TORRE ALFINA (TUSCANY) IN ORDER TO INVESTIGATE DEEP GEOTHERMAL RESERVOIRS. Champ scientifique natural scienceschemical sciencesinorganic chemistryinorganic compoundsengineering and technologyenvironmental engineeringenergy and fuelsrenewable energygeothermal energy Programme(s) FP1-ENNONUC 3C - Research and development programme (EEC) in the field of Non-Nuclear Energy, 1985-1988 Thème(s) Data not available Appel à propositions Data not available Régime de financement CSC - Cost-sharing contracts Coordinateur Ente Nazionale per l'Energia Elettrica SpA (ENEL) Contribution de l’UE Aucune donnée Adresse Via Andrea Pisano 120 56100 Pisa Italie Voir sur la carte Coût total Aucune donnée
