Publication Name: The Sedimentary Basins of WA
Authors: J.M. Kennard, I. Deighton, D.S. Edwards, C.J. Boreham & A.G. Barrett
Publication Volume: 3
Date Published: December 2002
Number of Pages: 46
Reference Type: Book Section
Abstract:
Subsidence and thermal history analysis of24 wells and seismically-defined depocentre sites has been undertaken to investigate the generation and expulsion history of the Early Carboniferous and Permian petroleum systems in the Petrel Sub-basin. Younger Mesozoic units are shown to be non-effective source rocks.Modelled oil and gas expulsion from postulated oilprone source units within the Lower Carboniferous
Milligans Formation is restricted to two offshore depocentres immediately north and south of the TurtleBarnett
High. Expulsion commenced in the Late Carboniferous, reached its peak in the Early Permian, and minor expulsion continued throughout the Permian and Early-Middle Triassic prior to the onset of regional uplift
associated with the Late Triassic Fitzroy Movement. Limited gas expulsion is also modelled in the onshore
Carlton Sub-basin, and although this unit is sufficiently mature in this area to have generated oil, the models
suggest that generated volumes are insufficient for expulsion of oil.
Modelled oil and gas expulsion from mudstones and coaly mudstones of the Lower Permian Keyling Formation
is restricted to the central and outer portions of the Petrel Deep. Expulsion from the outer Petrel Deep occurred in the Late Permian-Early Triassic, and expulsion from the central Petrel Deep commenced and peaked in the Early Triassic, with subsequent phases of minor expulsion in the Late Triassic-Cretaceous. Oil expelled from these source units may have migrated to pre-Fitzroy Movement structures and stratigraphic traps within and on the flanks