Three-Dimensional Magnetotelluric Characterization of the Travale Geothermal Field (Italy)

Francesca Pace,Alessandro Santilano,Anna Martí,Alberto Godio,Adele Manzella,Pilar Queralt,Juanjo Ledo

doi:10.3390/rs14030542

Abstract

The geoelectrical features of the Travale geothermal field (Italy), one of the most productive geothermal fields in the world, have been investigated by means of three-dimensional (3D) magnetotelluric (MT) data inversion. This study presents the first resistivity model of the Travale geothermal field derived from derivative-based 3D MT inversion. We analyzed MT data that have been acquired in Travale over the past decades in order to determine its geoelectrical dimensionality, directionality, and phase tensor properties. We selected data from 51 MT sites for 3D inversion. We carried out a number of 3D MT inversion tests by changing the type of data to be inverted, the inclusion of static-shift correction at some sites where new time-domain electromagnetic soundings (TDEM) were acquired, the grid rotation, as well as the starting model in order to assess the connection between the inversion model and the geology. The final 3D model herein presents deep elongated resistive bodies between the depths of 1.5 and 8 km. They are transverse to the Apennine structures and suggest a correlation with the strike-slip tectonics. Comparison with a seismic velocity model and well log data suggests a highly-fractured volume of rocks with vapor-dominated circulation. The outcome of this study provides new insights into the complex geothermal system of Travale.

Highlights

The magnetotelluric (MT) method is commonly employed to investigate deep geothermal resources as it can characterize the electrical resistivity of deep geothermal system structures [1,2,3,4]
3D MT inversion is of pivotal importance to providing new insights into the distribution of the electrical resistivities encountered in geothermal systems [6,20,21,22,23]
We examined the MT datasets that have been acquired in Travale over the past decades in the frame of research projects and industrial exploration surveys

Summary

Introduction

The magnetotelluric (MT) method is commonly employed to investigate deep geothermal resources as it can characterize the electrical resistivity of deep geothermal system structures [1,2,3,4]. Much research has focused on 3D MT modeling and the development of 3D MT inversion codes (e.g., [5,6,7,8,9,10,11,12,13,14]). Some of these codes and tools have been made available to the electromagnetic academic community (e.g., [8,15]). 3D MT inversion is of pivotal importance to providing new insights into the distribution of the electrical resistivities encountered in geothermal systems [6,20,21,22,23].

Objectives

Findings

Discussion

Conclusion