Gregory John Ambrose1
(1) Northern Territory Geological Survey, Darvin, N.T, Australia
Abstract: Oil potential of the Northern Pedirka Basin, Northern Territory, Australia
Regional seismic mapping in the Pedirka (Permian)/Eromanga (Mesozoic) basins in the Northern Territory has renewed interest in the area as a prospective oil province. Regional spatial relationships between generative hydrocarbon “kitchens” and associated structural highs are now available for the first time. Oil reservoired in the Mesozoic and sourced from the Permian/Triassic provides the main target. In the western Pedirka Basin the fault bound Eringa Trough includes 2500 ft. of Early Permian Purni Formation sediments (sandstone, shale and coal) which constitute the main source interval. Late Cretaceous sediment loading facilitated the generative process. The prospective northeastern flank of the trough, where a number of leads have been mapped, is virtually unexplored.
To the east in the Colson Trough the Purni Formation is 2200 ft. thick and subcrops the Triassic – Jurassic sequence facilitating a potential fairway of subcrop plays. Beyond the Triassic zero edge the basal Jurassic could be directly charged from the Permian providing a pinchout play where it onlaps the McDills High. On the eastern flank of the Colson Trough, in Colson #1, the Purni Formation is 600 ft. thick and lies within the oil window. Fluorescence show throughout the Triassic and basal Jurassic sands indicate possible vertical migration from the Permian. To the west, in the center of the Colson Trough, the Purni sequence thickens to about 2200 ft. and is in the oil window. Seismic is sparse in this area but two drillable prospects occur on the eastern margin of this trough and numerous structural leads provide further potential.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana