Abstract
Molecular and isotopic analyses of oils and gases can provide information on the depositional environment, maturation and age of their source rocks, and the post expulsion history of the hydrocarbons generated. Source rock analyses can determine their potential to generate hydrocarbons of varying type over specific thermal ranges, as well as demonstrating the strength of oil- or gas-to-source correlations. Together, this geochemical interpretation can provide insights about the extent of petroleum systems and can help delineate the relationships between hydrocarbon occurrences in a basin and across the continent. Oils that do not fit the well-established framework of oil families and Australian petroleum systems point to new source rock fairways. Examples include vagrant oils with lacustrine affinities found at various locations on the western Australian margin. Other examples are oil occurrences in the Gippsland Basin whose geochemical signatures contrast with the dominant non-marine oils, supporting the existence of a viable marine source rock facies. In under-explored and frontier basins, geochemical analyses of potential source rocks can provide key evidence to underpin new exploration efforts. For example, the recent acreage uptake in the Bight Basin was supported by Geoscience Australia’s recovery and analysis of oil-prone marine source rocks, and in the northern Perth Basin by new geochemical analysis extending the distribution of Lower Triassic Hovea marine source rocks offshore. Geoscience Australia has now embarked on a regional petroleum geological program that includes a national source rock study aimed at identifying and characterising Australia’s hydrocarbon sources, families and systems.
Published Version
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