Resistivity Imaging of the Santa Maria Sector and the Northern Zone of Las Pailas Geothermal Area, Costa Rica

Abstract

Geophysical exploration surveys were carried out by using MT and TDEM methods in the northeastern sector of Las Pailas Geothermal area. The electrical resistivity of the subsurface was modelled and interpreted for two specific areas located to the north and east of Las Pailas Geothermal Field in Costa Rica. The static shift problem of MT data was solved by inverting jointly both TDEM and MT soundings. Seven geophysical profiles were analysed based on 1D models from 22 MT and 19 TDEM soundings. Resistivity cross sections and iso-resistivity maps were compiled. We were aiming to image anomalies that could help to understand the conceptual model thinking in the future expansion of the actual production field. The different stages of alteration mineralogy were mapped and they are directly associated with the main geothermal signatures of a high temperature geothermal field. It was confirmed the existence of a structure trending probably NW-SE in the northern side of the survey area and in Santa María sector. A low resistivity body (deep conductor) was also mapped to the northern part of the study area which probably represent the heat source for the field.