Thermal Conductivity Characterization of Larderello and Mt. Amiata Geothermal Fields, Italy

摘要

The determination of the thermal conductivity of rocks (K) is fundamental to obtaining reliable values of the terrestrial heat flow (HF). The availability of samples for K determinations may be a major issue, since wells, and notably deep exploratory geothermal wells (down to depth >3000 m) are not common and generally limited to specific areas of exploration. In several cases, analogous outcropping rock samples may be collected, but obviously, the availability of deep core samples is preferable for the reconstruction of the environmental conditions at depth. We present a total of 27 determinations of K on core samples from 17 deep geothermal wells from the fields of Larderello-Travale and Mount Amiata (Italy), owned and managed by Enel. Twenty-one measurements were carried out with a QTM Showa-Denko transient line-source device, the remaining six with a Divided-Bar steady-state apparatus. Two different methods of correction for the effect of temperature at depth were applied, using experimental data from the same wells logged at depths corresponding to the core sampling. The experimental K data from two wells (one for each field) and their deep temperature dataset, were then combined applying the Interval Method, to obtain HF values that were plotted for comparison on the surface HF map of the area.