Contribution of Magneto-Telluric Method to Geothermal Development in El Salvador

Abstract

The Magneto-Telluric method (MT) is used in geothermal exploration programs as the only effective way to map resistivity variations from near surface to depths of several kilometres, given an estimated depth of the reservoir. In El Salvador this method has contributed to the development of the geothermal resources providing reliable information about the location and characterization of the most promising geothermal systems.
The geophysical interpretation for the Ahuachapán geothermal reservoir indicates that deep conductive rocks are present between Ahuachapán and Chipilapa.
The reservoir in the Berlin Geothermal field corresponds to an uplifted resistive layer at depth, corresponding to philitic and propillytic alteration facies, with resistivity values ranging form 40 to 90 ohm-m inside the resistive basement, at higher values, temperature inversion is attempted.
The San Vicente geothermal reservoir was associated with an uplifted resistive layer at depth as well as a positive residual gravity anomaly. The propillytic reservoir was intercepted by the first exploratory well.