This study focuses on the changes in the stable carbon (d13C) isotopic composition of the saturated and aromatic hydrocarbons in western Australian crude oils through time. From this extensive dataset, carbon and hydrogen (dD) isotopic compositions of individual C7+ n-alkanes were obtained for the major genetic oil families. The samples originate from the Arafura, Bonaparte, Browse, Canning and Perth basins, with source ages that span the Cambrian to the Cretaceous. Complementary biomarker analyses provide insights into the type of organisms preserved in the source rock, its lithology and depositional environment, as documented by Geoscience Australia and GeoMark (2005). This study shows that the line used to separate a global set of marine and non-marine oils by Sofer (1984), is not particularly useful for western Australian oils (Figure 1). Using the combination of bulk and n-alkane-specific d13C isotopic profiles, oil families of Palaeozoic and Mesozoic age can be distinguished. From the Early to the Late Palaeozoic, Australian oils have become isotopically more enriched in 13C. The most depleted d13C value of -32.0 is recorded for the saturated hydrocarbon fraction (d13Csat) of a Cambrian oil-stain in the Arafura Basin. d13Csat values of about -31 are recorded for Ordovician oils from the Canning Basin, with slightly more enriched values (mean d13Csat = -29.3) being obtained for Late Devonian marine oils in this basin. Early Carboniferous marine oils from the Bonaparte and Canning basins have mean d13Csat values in the order of -28. Permian terrestrially sourced wet gases/condensates are some of the most 13C-enriched samples from western Australian, with values of around -24.6 being recorded in the Bonaparte Basin and -25.7 in the Perth Basin. Early Triassic Perth Basin oils have extremely depleted saturated hydrocarbon isotopic values of around -32 that are not as pronounced in the aromatic hydrocarbon fraction (mean d13Carom = -29.9), separating them from the Ordovician Canning Basin oils. Jurassic oils from the Bonaparte, Browse and Carnarvon basins exhibit a range in their d13Csat values from -26.1 to -27.8, due to generation from multiple source rocks throughout the oil window. Their source rocks were deposited in fluvio-deltaic to marine systems and contain varying amounts of land-plant material. Early Cretaceous marine oils of the Bonaparte and Browse basins have depleted d13Csat values in the order of -30.2 and -28.6 respectively, and can be differentiated from the Early Carboniferous oils on their n-alkane-specific isotope profiles. The n-alkane-specific d13C isotopic profiles of the Palaeozoic and Mesozoic oils and condensates characteristically follow the same trend as the bulk d13C isotopic values. The n-alkane-specific dD isotopic profiles typically complement those of the carbon isotopic profiles for the oils derived from marine source rocks. The carbon and hydrogen profiles exhibit distinct differences in oils that originate from either non-marine systems, or, in the case of the Triassic aged Perth Basin oils, a restricted anoxic marine environment.

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The oil and gas exploration and development industry is a significant Australian industry. In 2000 the value of oil and gas produced was $10.5 billion. This meant that Australia remained more than self sufficient in petroleum, contributing to economic activity and avoiding the balance of payment pressure that importing that amount of petroleum would represent. There is thus an incentive to maintain a healthy petroleum exploration and production industry. R&D for the upstream petroleum industry however, needs to be targeted to the requirements of the differing facets of the industry under the diverse conditions in which the industry operates or could operate. These conditions include changes in oil prices and perceptions of prospectivity, uncertain access to gas markets and the effects of international agreements such as the United Nations Framework Convention on Climate Change. Different petroleum companies also have differing exploration and production portfolios and different needs. Petroleum service industry companies try to meet industry?s needs. Governments have their own goals in promoting and regulating the industry and derive considerable revenues for economic rent applied to reserves held by the Crown. In the above context, a range of scenarios was considered in a planning process prioritising future needs for petroleum R&D in Australia. In this context two groups of senior petroleum industry, research and government representatives carried out scenario planning workshops in 1998 and 1999 to define scenarios and associated R&D priorities to assist in planning and identifying opportunities for petroleum R&D. The results of this study highlight core areas of R&D that are required under most of the scenarios. These are considered highest priority and high priority areas. Given the long time frame (in the order of 10 years) needed to develop and maintain R&D capability, this highlights for government, academia and industry the sustained effort needed for development and maintenance of capability particularly in these core areas of R&D. In 1998 and 1999 when the workshops that formed the basis of this study were undertaken, Australia was arguably in the `low oil and gas price scenario?. This scenario puts an onus on government to support regional studies to promote exploration and most priority petroleum R&D. Under this scenario support from industry is substantially aimed at reducing cost. Although oil prices have increased, coincident increases in stock market pressures for competitive profits from the industry has arguably left the industry in 2001 still in the low oil and gas price scenario. Thus there remains a strong need to maintain a local petroleum R&D capability to meet Australia?s needs.

In March of this year Mr. A.E. Hawker, of Jindare, forwarded to Canberra a small bottle containing water and a yellowish, oily substance which had formed a coating on the inside of the bottle. Microscopic examination of part of the coating proved the presence of globules of oil and also revealed Desmid algae. It seemed probable that the oil had been derived from the decomposition of algae or other recently dead plants. However, as the locality from which the sample was taken lies within a belt of Cambrian limestone, it was possible that the oil had its origin in this rock. While recently engaged in field work in the Northern Territory, Mr. C.J. Sullivan and the writer examined the localities where oil was said to occur. This report comprises an account of the field observations and geological notes made during the examination.