VGP Technical Report 66 - Elements of the Austral 1 petroleum sub-system, Onshore Otway Basin, Victoria
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Product description:About the Victorian Gas Program: The Victorian Gas Program (VGP) is a comprehensive science-led program, incorporating geoscientific and environmental research to assess the risks, benefits and impacts of potential onshore conventional gas exploration and production. The program is also investigating the potential for further discoveries of onshore conventional and offshore gas in the Otway and Gippsland geological basins and assessing the feasibility of additional onshore underground gas storage in depleted reservoirs around the Port Campbell area. The VGP includes an extensive, proactive and phased community and stakeholder engagement program, through which the results of the scientific studies are being communicated. Executive summary: As part of the Victorian Gas Program (VGP), the Geological Survey of Victoria (GSV) is studying petroleum systems components (reservoir, seal and source), to assess the hydrocarbon prospectivity of the Victorian Otway Basin and estimate the potential for further onshore and offshore discoveries within Victoria’s jurisdiction. This report details an analysis of the distribution and characteristics of Austral 1 petroleum sub-system elements that was completed to support the Otway Basin hydrocarbon prospectivity assessment. The hydrocarbons of the Otway Basin are sourced from the Mesozoic-Cenozoic Austral Petroleum Supersystem (Bradshaw, 1993; Summons et al., 1998). In the Otway Basin, the Austral Petroleum Supersystem is divided into three sub-systems (Edwards et al., 1999; O’Brien et al., 2009) that are differentiated based on the depositional environments of the source rocks for each sub-system. The Austral 1 petroleum sub-system comprises Late Jurassic to Early Cretaceous fluvial and lacustrine source rocks of the Casterton Formation and Crayfish Subgroup. The key reservoir-seal pairs for the Austral 1 sub-system are the sandstones and shales of the Sawpit Formation (Eid et al., 2021) and the Pretty Hill-Laira formations reservoir-seal pair. The Pretty Hill Formation reservoir has been targeted in Victoria with no commercial success while the Sawpit Formation reservoir, which hosts commercial hydrocarbons in South Australia, has not been considered in Victorian basin analysis prior to the VGP. The extent and characteristics of the Sawpit Formation and Pretty Hill-Laira formations reservoir-seal pairs in Victoria have been defined and characterised. The Sawpit Formation reservoir-seal pair is restricted to the Penola Trough, while the Pretty Hill-Laira formations reservoir-seal pair is present across the majority of the Victorian onshore Otway Basin. Reservoir units associated with both reservoir-seal pairs have effective reservoir quality, while sealing units are mappable and have good seal capacity where data exists. Hydrocarbon indicators in several wells suggest that Austral 1 source rocks have sufficient maturity to generate and expel hydrocarbons, with modelling undertaken as part of the VGP (van Aarssen, 2020) supporting the presence of active source kitchens associated with the Austral 1 petroleum sub-system within the Penola Trough and along the Victorian coastline. Bibliographic reference: Eid, R., Herley, S.S. & Revie, D.J., 2021. Elements of the Austral 1 petroleum sub-system, Onshore Otway Basin, Victoria. VGP Technical Report 66. Geological Survey of Victoria. Download: The downloadable version of this report is supplied in PDF format (18 MB), Att A1 (XLSX 134 KB) & Att A2 (XLSX 35 KB). Related products:
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