The relationship between resistivity and mineralogy at Travale, Italy.

A study on cuttings and cores of geothermal wells was carried out in order to identify the types and abundance of primary and alteration minerals and to compare these data with the measured resistivity values. This study determined that lithology and heterogeneities of reservoir rocks and the alterations affecting them may only account for the small variation observed in the resistivity logs, but not for the main anomaly detected by the magnetotelluric data in the dry-steam geothermal reservoir. The occurrence of brines was suggested by the study of fluid inclusions that have shown that high-salinity fluids have circulated in the reservoir and were trapped in minerals often along healed micro-fractures. Although never highlighted by production tests, the occurrence of brine partially in a liquid phase inside the pore network or the presence of adsorbed water should be considered in further research.