The Gippsland basin in offshore Victoria, Australia, was renowned for its generally simple, hydrocarbon traps: large features where, despite commonly interbedded sequences, the high lateral and vertical sand continuity resulted in simple oil/water contact configurations. It was not considered the place for existence of subtle traps--that is, not until the drilling of a dry hole provided sufficient clues to allow the evaluation of a concept to be one of the objectives in drilling a field-delineation well. The result was a new discovery--a new concept in exploration in the basin. Even so, it took additional delineation wells before it became possible to finally prove the concept. Although the concept was felt to have been proved, it became necessary to justify this new" oil, using techniques of detailed reservoir description including geometry and environments of deposition, paleogeography, geochemistry, and reservoir pressure data.