The Larderello – Travale and Amiata Geothermal fields: history cases of engineered geothermal systems since early 90’s

Abstract

The development of geothermal fields in Tuscany is related to the exploitation of deep reservoirs in metamorphic and granitic rocks. The permeability of fractured zones can be reduced during the well completion by occlusion of fractures with accumulated debris or drilling mud, or during the well production life by salts deposition. Since 1980, in order to increase the productivity of individual wells after drilling and to preserve it during their production life, some stimulation techniques have been developed and are currently being implemented. The aim of these techniques is to improve the permeability of fractured zones and to reduce or eliminate the formation damage (skin factor) by means of acid stimulation (HCl and HF). With the experience gained during the operation and maintenance of the wells, different causes of well damage (formation or wellbore) have been identified and different techniques aimed to the recovery of the original productivity have been studied and implemented; some of these are also based on the injection of water. This paper discusses the criteria used to identify the suitable wells and the different types of well stimulations, moreover some history cases are shown.