As part of preparations to drill the Koonakoo Prospect in the eastern Simpson Desert, 60 km north-west of Goyder Lagoon, PEL 49 joint venturer Hunt Energy and Mineral Company conducted a prior electrotelluric survey of that prospect and others within PELs 49 and 50, to try to remotely detect hydrocarbons present in the deep subsurface, and their depth of occurrence. The geophysical method employed relies on passive detection of very low frequency earth currents induced by natural electromagnetic pulsations of the ionosphere, whereby the discrete electrical properties of individual formations modulate the induced telluric currents in a manner that may relate to their hydrocarbon content. As back-up to this technique, surface sediment electrochemistry was also investigated (conductivity, Eh, pH, plus microbial count) to pick up geochemical indications of any hydrocarbon plumes that might be escaping to surface from a possible buried oil accumulation. The survey was run over the period August-September 1997 by two visiting US-based contractor teams. The resultant EM frequency vs depth analogue data is presented as separate plots for 174 stations read at 1 km intervals along existing seismic lines which pass over the targetted prospects and leads. A brief summary of the complementary surface electrochemical readings is presented separately.