The present study is aimed at attaining an approach of the crust structure at 
Travale area (Tuscany, Italy) by 3D electrical resistivity modelling and forward 
computing, and understanding the differences between the forward computed 
results and measured magnetotelluric resistivity data. Pointing to these 
targets, different 3D models were built including the resistivity of geological 
units from a resistivity log, zones of high temperatures and productive fractures 
from drillholes measurements, bright-spot type horizons identified in seismic 
profiles and estimated resistivity values of the lower crust and mantle. 
Responses from forward modelling were calculated and compared with 
magnetotelluric data obtained in the field. The outcomes of the study point out 
that low resistive bodies are present at the depth of the exploited geothermal 
reservoirs, that cannot be explained only by means of the geological units.

A secondary scope of this study was to establish if MT method is capable to 
distinguish between different porosity structures in geothermal reservoirs, as 
fluids situated within rock pores or within spaced or dense fracture systems. 2D-
3D modelling and forward computing of models containing different porosity-
type reservoirs were developed to achieve this aim.

The study was supported by the IGET EU Project and partly carried out within 
the framework of ICTP Programme for Training and Research in Italian 
Laboratories, Trieste, Italy.

Campus SIAF, SP del Monte Volterrano
Localita' Il Cipresso
Volterra, Italy