Contribution to Oil Exploration and Development - A Successful Inductive Multi-Frequency EM Survey On-Shore Brazil

In this work we discuss the results of an experimental study performed using a multi-frequency electromagnetic method over a mature oil field in Recôncavo basin, Bahia-Brazil. Five 1.8 km transects, 200 m apart, were surveyed over a selected oil reservoir block. The processed EM data are represented as cross-sections and maps of apparent resistivity and induced polarization parameter, using a consistent plotting procedure. All the sections, controlled by well logging data, allow to recognize the following geological features: (i) the oil sandstone horizons and their trapping shales; (ii) the oil-water interface and some zones of water invasion; and (iii) lateral electric contrasts representing fault zones. These results suggest the real possibility of the use of the spectral EM method in the direct detection of hydrocarbons, as well as for monitoring the efficiency of the artificial fluid injection used for secondary recovery. Also, this experiment brings about a further development in the inductive measurement of IP and introduces, for the first time, the use of this property in oil reservoir exploration and characterization.