A Comparison of Electromagneticmethods with the DC Resistivity Multiple-Source Bipole-Dipole Method for Deep Geothermal Exploration

Abstract

An evaluation of the utility of 4 different electromagnetic methods for exploration of the deeper parts of a geothermal reservoir was recently published by Pellerin et (1992). The resistivity multiple-source bipoledipole technique has been used successfully in for the exploration of the deeper levels of the geothermal systems for many years. In this paper, results of a similar evaluation of the resistivity multiple-source technique is presented and compared with the EM techniques. Using 3 dimensional (3D) models the ability of each technique to detect the existence of an geothermal reservoir beneath a highly conductive zone near the compared. The Pellerin et al. study showed that, of the EM techniques, only the Magneto Telluric and Long Offset Time Domain EM (LOTEM) methods will detect the presence of the reservoir. 3D modelling shows that the technique will detect the deeper resource Indeed the electric field response the LOTEM method at late times, where the response of the reservoir is seen, is identical to the resistivity response.