In order to examine the prospectivity of EPP 23, for which they assumed the operatorship by a 65% farm-in in August 1990, BHP Petroleum have examined well palynological and geochemical data in and around the permit and have interpreted over 600 km of recently acquired seismic data. Source rock studies indicate that the Early Cretaceous Eumeralla Formation probably has the greatest potential to generate liquid hydrocarbons, with the peak generation period occurring during the latest Cretaceous. The Late Cretaceous Belfast Mudstone tends towards gas proneness but has the potential to yield up to one billion barrels of accumulatable hydrocarbons. Reservoir qualities of the Late Cretaceous Waarre/Flaxman Formation and the Paaratte Formation above 3 000 metres depth are quite good. However, in the deeper parts of the Voluta Trough where the Waarre/Flaxman reach depths in excess of 4 000 metres, porosities and permeabilities are low. Mapping of the recently acquired seismic data has failed to improve on the potential of any of the existing prospects and leads within EPP 23. Increased faulting and lack of dip closure evident with improved seismic data resolution, plus the very localised nature of roll-over in some leads, have downgraded many of the prospects and leads. None could be recommended for drilling at this stage.