Application of an electromagnetic borehole induction logger to groundwater contamination mapping

Although electromagnetic induction loggers have been used by the oil industry for many years their sondes are generally unsuitable for groundwater applications, for which the requirements are 1 . Slim probes (monitoring Wells are often only 5 cm in diameter) 2 . Good vertical resolution, so as to resolve thin contaminant plumes, combined with a moderate radial depth of investigation (of the order of 1m) 3 . Low noise and good stability so as to measure background conductivities as low as 1 mS/m (1000 ohmm ) 4 . Linear response with conductivity to about 3000 mS/m (0 .3 ohmm ) 5 . Modest depth of exploration, seldom in excess of 250 m, and lastly 6 . The overall system (including winch and console) must be compact, lightweight and relatively inexpensive .