Authors / CoAuthors
Taylor, D.
Abstract
Petroleum source rocks are found at three levels in the Ordovician sectionin the Canning Basin and appear to be at similar stratigraphic levels and ofsimilar organic facies to the source rocks which have produced the gas andgas-condensate fields in the Amadeus Basin. In both basins shallowintersections in drillholes have yielded material at a low level of thermal maturity.Samples have shown that these immature source rocks contain algal-sourcedType 1 kerogens with a high hydrogen index and a large capacity to generate oil(eg Hoffmann et al., 1987). Deeper wells in both basins encountered sourcerocks at higher levels of maturity associated in some cases with oil fluorescenceand shows of live oil. By comparing the results of Rock-Eval pyrolysis analysisfor these more mature source rocks with those of the immature rocks the degreeof kerogen conversion to hydrocarbon (the Transformation Ratio of Espitalie eta)., 1986) can be estimated. The results from 14 wells along the BroomePlatform show a rapid downward increase in transformation ratio (TR) through theOrdovician section which can be correlated to the rapid downward increase in theconodont alteration index (CAI) previously documented by Nicoll & Gorter (1984).This correlation shows that the zone of peak oil generation lies between the endof CAI Zone 1 and the beginning of CAI Zone 2. The Ordovician in the Canning Basin is known mainly from intersectionsin 22 drillholes. It is thickest in two sub-basins: the Willara, bounded to the northby the Admiral Bay Fault, and a larger unnamed sub-basin (roughly coincidentwith the later Fitzroy Trough), bounded to the north by the Oscar Range-Pinnaclefault system. Both fault systems appear to have been active during thedeposition of the Ordovician. The best known source rocks occur along thesouthern side of the northern sub-basin; they appear to be poorly developed, orabsent, in the Willara Sub-basin. Overmature source beds are locally preservedin fault remnants under the Lennard Shelf and may exist at great depth in theFitzroy Trough.
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document
eCat Id
14552
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
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Keywords
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- GA PublicationRecord
- ( Theme )
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- petroleum geology
- ( Theme )
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- stratigraphy
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- AU-WA
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_External
Publication Date
1992-01-01T00:00:00
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geoscientificInformation
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Record 1992/043
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