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Evolution And Petroleum Prospectivity Of The Eyre Sub-Basin, Offshore Western Australia.

Corrie, Glenn David

Honours Degree, 1992

University of Adelaide

Abstract

Regional interpretation and mapping of seismic data over the Eyre Sub-basin, in the western portion of the Great Australian Bight, has resulted in an evaluation of the tectonic framework and stratigraphic development of the area.

The structural evolution of the Eyre Sub-basin has been largely controlled by the rifting of Australia and Antarctica, which began in the Jurassic. Large half-graben morphology, rotational normal faults and smaller, tilted fault blocks form the characteristic architecture. Dissecting accommodation zones offset basement trends and have exerted substantial influence on deposition within the Sub-basin.

Late Jurassic syn-rift sedimentation is interpreted to have occurred mainly in deep lacustrine environments and is overlain by an Early Cretaceous rift fill sequence of fluvio/deltaic sand and shale. A thin marine transgressive sequence of black shale forms the final stage of rift sedimentation. The post breakup sequence consists mainly of shallow marine sands capped by a thick prograding carbonate unit.

The Eyre Sub-basin is considered prospective for the accumulation of hydrocarbons. Only one exploration well has been drilled and, while the entire well section was dry and immature, good-quality reservoirs and moderate quality source rock intervals were penetrated. Through the integration of structural and isochron mapping, potentially mature source rock areas and migration pathways have been identified, whilst large fault-dependent traps are recognised as the main prospective play type.

The main limitations on the petroleum prospectivity of the Eyre Sub-basin are thermal immaturity and seal integrity. The current level of exploration does not preclude the existence of significant hydrocarbon accumulations in the Sub-basin.

Australian School of Petroleum
THE UNIVERSITY OF ADELAIDE

SA 5005 AUSTRALIA

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