Geochemical evaluation of fluid inclusion oils from Flying Foam-1 and Leander Reef-1, offshore northern Perth Basin, Australia

Organic Geochemistry

Ahmed, Manzur ; Volk, Herbert ; Fuentes, David

CSIRO

DOI  :  10.4225/08/58518a32dc379
RP-ID  :  EP114287

学科分类：地球科学(综合)

澳大利亚|英语

来源: CSIRO Research Publications Repository

【 摘 要 】

This report presents an organic geochemical evaluation of fluid inclusion (FI) oils retrieved from three reservoir rock samples of the wells Flying Foam-1 and Leander Reef-1 drilled in the offshore Perth Basin by using the Molecular Composition of Inclusions (MCI) technique (George et al., 2007). A comparison of source and maturity characteristics of the Flying Foam-1 FI oils to other oils and FI oils of the region is also presented. Only the samples from Flying Foam-1 yielded FI oil data above background levels.Secondary alterationThe Flying Foam-1 FI oils do not exhibit any signs of secondary alteration by biodegradation prior to entrapment. However, the absence of gasoline-range hydrocarbons and low relative abundances of C15 n-alkanes may be indicative of their minor alteration by gas or water washing.Source characterisationThe Flying Foam-1 FI oils have been generated from marine sources rocks deposited in suboxic to anoxic environments containing predominantly aquatic algal organic matter with some minor amount of terrestrial higher plant inputs. The most likely source rock for the Flying Foam FI oils is the Early Triassic Kockatea Shale (Hovea Member). However, Flying Foam-1 FI oils have significant source differences from the Cliff Head oils, the Hadda FI oil, the Dongara and Yardarino oils, and the Leander Reef (2837 m) FI oil, all of which are believed to be derived from or to contain a component of the Hovea Member of the Kockatea Shale. These perceived source differences may be due to different maturity levels of the fluids, facies differences of the Kockatea Shale, mixing with oil from other sources, in particular with hydrocarbons from Permian coals, secondary alteration processes such as gas or water washing, or a combination of all these factors.Thermal MaturityMaturity parameters based on biomarker and aromatic hydrocarbons distributions consistently indicate that the Flying Foam-1 FI oils were derived from source rock(s) at early to peak oil window maturities at a vitrinite reflectance equivalent of ca. of 0.7-1.1%.Comparison with other oils of the regionThe statistical analysis of selected source parameters, believed to be largely maturity-independent, divided the offshore Perth Basin oils and FI oils into three genetic groups: Cluster 1 consisting of Flying Foam-1, Leander Reef-1 (2837 m) and Hadda-1 FI oils; Cluster 2 consisting of Yardarino-1, Cliff Head-6 and Dongara-14 oils and Cliff Head-3 FI oil; and Cluster 3 consisting of Houtman-1 and Gage Roads-2 FI oils. All oils of Cluster 1 and 2 contain at least some contribution from the Hovea Member of the Kockatea Shale, and these two clusters are more related to each other than to Cluster 3. Base on a correlation of TMNr versus TeMNr the offshore Perth Basin oils can be arranged in the following order of decreasing thermal maturity: Yardarino-1 oil (most mature) Dongara-14 oilLeander Reef-1 FI oilCliff Head oil and FI oilFlying Foam-1 1320-25 m oilFlying Foam-1 1245-55 m FI oil, Hadda-1 FI oil, Houtman-1 FI oil Gage Roads-2 FI oil (least mature).