Tectonic Events, Sequence Stratigraphy and Prediction of Petroleum Play Elements in the Cretaceous and Tertiary of the Northern Carnarvon Basin, North West Shelf, Australia

K. K. Romine and J. D. Durrant

The Carnarvon Basin is one of Australia's most prolific oil and gas provinces. A recent Paleocene discovery has initiated a shift in exploration interest from traditional Jurassic/Triassic plays to the younger Cretaceous and Tertiary section. To improve play element prediction, a sequence stratigraphic study has been completed, utilising newly acquired, regional high-resolution seismic data and 80 wells. The occurrence and distribution of the key play elements, reservoir, source and seal, is controlled by the interaction of tectonic subsidence, eustasy and paleogeography, with traps and migration pathways set up and modified by regional tectonic events. For example, a major rifting event commenced in the latest Kimmeridgian-Tithonian that resulted in structuring of older urassic sediments and initiation of seafloor spreading in the adjacent Cuvier-Gascoyne Abyssal Plain in the Valanginian. This event was accompanied by a dramatic fall in eustasy that initiated the deposition of high-quality reservoir sandstones of the Tithonian-Valanginian age Barrow Delta. The post-rift phase of thermal cooling and rapid subsidence resulted in transgression, accompanied by deposition of backstepping parasequences of the Mardie Greensand, a potential thief zone and reservoir, and culminated in maximum transgression and deposition of seal and source facies of the Muderong Shale. The improved sequence stratigraphic framework established in this study provides a predictive tool for the development and assessment of new plays.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California