PASSMORE, VIRGINIA L.¹, DIANE S. EDWARDS², and JOHN M. KENNARD^2
1Bureau of Resource Sciences Canberra, Australia
²Australian Geological Survey Organisation, Canberra, Australia

Abstract: Enhanced Permo-Triassic Prospectivity in the Timor Sea Provided by A New Paleozoic Petroleum System

Numerous oil and gas discoveries in the Timor Sea region (eg. Cornea, Challis, Jabiru, Laminaria, Bayu-Undan), which are sourced from organic-rich facies in Jurassic and Cretaceous source rocks generated in adjacent depressions and troughs, have focussed exploration attention and activity in the Timor Sea region on the Jurassic petroleum system and on highs in proximity to the troughs. Structural features such as the Londonderry High which contain thick Triassic and Paleozoic sequences but lack Jurassic sediments and/or are too distant from the known Jurassic petroleum kitchens were considered to have limited prospectivity.

Recent hydrocarbon analyses on residual oil in the Torrens 1 well on the Londonderry High and Rock-Eval pyrolysis analyses on samples from the same well have demonstrated the presence of an older, active Paleozoic age petroleum system in this area that could source porous pre-Jurassic reservoirs on the high. The Torrens oil was sourced from predominantly terrestrial organic matter similar in age to but geochemically distinct from the hydrocarbon sources in the nearby Paleozoic Petrel Sub-basin. Organic-rich rocks with both gas and liquid hydrocarbon potential may also occur in Triassic marine shales in the Sahul Group and Mount Goodwin Formation. Although the shale samples from wells on the high were immature, these Triassic units are expected to be mature where more deeply buried in the eastern portion of the high. The Permian and Triassic organic-rich lithofacies sampled are widespread across the Londonderry High area.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas