Petroleum prospectivity could be more favorable than previously believed on the Naturaliste plateau seaward of the Perth basin off south Western Australia, a study by Geoscience Australia, Canberra, concluded.
The 90,000-sq-km area lies 350 km off the Cape Naturaliste-Whicher Range area in 2,000-5,000 m of water. If oil has been generated, it likely migrated to the east where traps could occur in much shallower water, wrote Irina Borissova in the September 2002 issue of Aus-Geo News.
Results of the agency's recent framework study suggest that "basement beneath most of the plateau and the Naturaliste trough contains extensional structures typical of continental margins."
The western Mentelle basin, lying beneath the Naturaliste trough and west of the Perth basin and Vlaming subbasin, is the study area's largest depocenter with 4-5 km of sediment.
It includes about 1 km of Early Cretaceous sediments and at least 1.5 km of Jurassic section, Borissova wrote.
"Based on the southern Perth basin, source rocks are likely to occur in lateral equivalents of Middle-Late Jurassic Yarragadee formation and Early Cretaceous Parmelia formation." Overburden above Cretaceous is insufficient for generation, but Jurassic source rocks may be within the oil window.
