Authors / CoAuthors
Boreham, C.J. | Blevin, J.E. | Radlinski, A.P. | Trigg, K.R.
Abstract
Few published studies have demonstrated that coals have sourced significant volumes of oil, while none have clearly implicated coals in the Australian context. This paper presents strong geochemical evidence for coals being the source for the sub-economic oil accumulations in the Bass Basin. Oils in the Bass Basin form a single oil population. Biodegradation of Cormorant oil results in a separate oil family compared to Pelican and Yolla crudes. Oil-to-source correlation based on biomarkers and carbon isotopes shows that the Early Eocene to Palaeocene coals are effective source rocks in the Bass Basin. This is in contrast to previous work which favoured disseminated organic matter in claystone as the sole source (Miyazaki, 1995). Potential oil-prone source rocks in the Bass Basin are the early Tertiary coals, mainly concentrated in the Middle to Early Eocene succession. These coals have hydrogen indices (HI) up to 500 mg HC/gTOC) and are associated with disseminated organic matter in claystones that are mainly gas prone. Maturity is sufficient for oil and gas generation with vitrinite reflectance (VR) up to 1.8 % at base of Pelican-5. Igneous intrusions, mainly within Palaeocene, Oligocene and Miocene sediments, produce localised elevated maturity to 5 % VR. The key events in the process of petroleum generation and migration from the effective coaly source rocks in the Bass Basin are: (i) the onset of oil generation at a VR of 0.65 % (2450m in Pelican-5); (ii) the onset of expulsion (primary migration) at a VR of 0.75 % (2700 to 3200m in Bass Basin; 2850m in Pelican-5); (iii) the main oil window between VR of 0.75 % and 0.95 % (2850-3300m in Pelican-5); and, (iv) the main gas window at VR >1.2 % (>3650m in Pelican-5).
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nonGeographicDataset
eCat Id
40635
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Keywords
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- External PublicationScientific Journal Paper
- ( Theme )
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- geochemistry
- ( Theme )
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- hydrocarbons
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
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2003-01-01T00:00:00
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