Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Surprisingly few natural hydrocarbon seeps have been identified in Australia's offshore basins despite studies spanning thirty years. Initial studies of natural hydrocarbon seepage around the Australian margin were generally based around the geochemical analysis of stranded bitumens, water column geochemical `sniffer' sampling, synthetic aperture radar or airborne laser fluorsensor. Later studies involved the integration of these remote sensing and geochemical techniques with mutli-channel and shallow seismic. A review of these earlier studies indicates that many seepage interpretations need to be re-evaluated and that previous data sets, when set in a global context, often represent normal background hydrocarbon levels. Relatively few sites of proven natural hydrocarbon seepage in Australia's offshore sedimentary basins can be reconciled with the dominantly passive margin setting and low recent sedimentation rates, which are not favourable for high rates of seepage, and difficulties in proving seepage on high energy, shallow carbonate shelves, where seabed features may be rapidly reworked and modern marine signatures are overprinted on authigenic seep carbonates. Active thermogenic methane seepage on the Yampi Shelf, the only proven documented occurrence in Australia, is driven by deposition of a thick Late Tertiary carbonate succession and Late Miocene tectonic reactivation. Therefore, to increase the success of detecting and correctly interpreting natural hydrocarbon seepage, data need to be analysed and integrated within the context of the local geological setting, and with an understanding of what is observed globally.

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1. Blevin et al.:Hydrocarbon prospectivity of the Bight Basin - petroleum systems analysis in a frontier basin 2. Boreham et al : Geochemical Comparisons Between Asphaltites on the Southern Australian Margin and Cretaceous Source Rock Analogues 3. Brown et al: Anomalous Tectonic Subsidence of the Southern Australian Passive Margin: Response to Cretaceous Dynamic Topography or Differential Lithospheric Stretching? 4. Krassay and Totterdell : Seismic stratigraphy of a large, Cretaceous shelf-margin delta complex, offshore southern Australia 5. Ruble et al : Geochemistry and Charge History of a Palaeo-Oil Column: Jerboa-1, Eyre Sub-Basin, Great Australian Bight 6. Struckmeyer et al : Character, Maturity and Distribution of Potential Cretaceous Oil Source Rocks in the Ceduna Sub-Basin, Bight Basin, Great Australian Bight 7. Struckmeyer et al: The role of shale deformation and growth faulting in the Late Cretaceous evolution of the Bight Basin, offshore southern Australia 8. Totterdell et al : A new sequence framework for the Great Australian Bight: starting with a clean slate 9. Totterdell and Bradshaw : The structural framework and tectonic evolution of the Bight Basin 10. Totterdell and Krassay : The role of shale deformation and growth faulting in the Late Cretaceous evolution of the Bight Basin, offshore southern Australia

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B.M.R. Maclean No. 1 was a fully cored stratigraphic hole drilled on the eastern margin of the Clarence-Moreton Basin near Evans Head. It reached a total depth of 664.8 m and intersected 590.05 m of Marburg Formation overlying 74.75 m of Ripley Road Sandstone. The lower 42.60 m of the Marburg Formation correlates with the Calamia Member recognised by Etheridge & others (1985). The sequence is mostly multistorey fluvial channel sandstone with only a small proportion of fine grained facies so that potential hydrocarbon source rocks are rare. Porous sandstone is also rare, though parts of the Calamia Member and the Ripley Road Sandstone may be porous and permeable.

A companion volume to 'The geology and petroleum potential of the Clarernce-Moreton Basin, New South Wales and Queensland' compiled and edited by A.T. Wells and P.E. O'Brien, Australian Geological Survey Organisation bulletin 241(1994).

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