Re-evaluation of depositional models for the lower Permian Patchawarra Formation, Cooper Basin, South Australia: implications for petroleum exploration
Carmine Wainman A B and Peter McCabe AA Australian School of Petroleum and Energy Resources, University of Adelaide, Adelaide, SA 5005, Australia.
B Corresponding author. Email: carmine.wainman@adelaide.edu.au
The APPEA Journal 60(2) 794-796 https://doi.org/10.1071/AJ19207
Accepted: 11 February 2020 Published: 15 May 2020
Abstract
The Late Carboniferous–Triassic Cooper Basin is Australia’s most prolific onshore petroleum province. The lower Permian Patchawarra Formation, which is up to 680 m thick and consists of up to 10% coal, is a major exploration target in the basin. Eighteen cores through the formation have been logged to re-evaluate the existing fluviolacustrine depositional model. The siliciclastics form fining- and coarsening-upward sequences that are 1–10 m thick. They are predominately fine-grained with abundant lenticular bedding, wavy bedding and thinly interlaminated siltstones and clays resembling varves. Granules and pebbles, interpreted as dropstones, are present throughout the formation. Coal beds are up to 60 m thick and rich in inertinite. Other than the coal beds, there is little evidence of the establishment of terrestrial conditions: roots are rare and there are no siliciclastic palaeosols. The siliciclastics are interpreted as the deposits of a large glaciolacustrine system, with the fining-upward successions deposited in subaqueous channels cut by hyperpycnal flows and the coarsening-upward successions deposited as overbank splays between those channels. Hyperpycnal flows may have resulted from sediment-laden cold water emanating from glacially-fed rivers, similar to those seen in many large glacial lakes in high latitudes and altitudes today. Much of the coal is interpreted as the accumulation of peats from floating mires that covered large parts of the glaciolacustrine system at certain time intervals. The high inertinite content of many coals is interpreted as the decay of organic matter within the floating mire. These new interpretations have the potential to enhance reservoir characterisation within the basin.
Keywords: floating mires, glaciolacustrine, hyperpycnal flows, inertinite.
Carmine Wainman is a Postdoctoral Fellow at the University of Adelaide in Australia. He completed his PhD in 2018 at the same university and received his MSc (Integrated) Degree in Geology from the University of Southampton, UK, in 2012. Before commencing his PhD, he worked for the RSK Group and Woodside Energy. His research focuses on Permian to Jurassic coal-bearing strata in eastern Australia, and the evolution of Upper Cretaceous strata in the Bight Basin on Australia’s southern margin in collaboration with the International Ocean Discovery Program. |
Peter McCabe obtained his PhD in Geology at the University of Keele in the UK. After graduating he moved to North America where he worked for various organisations including Exxon Production Research Co. in Houston and the Alberta Research Council in Edmonton. He worked for 20 years with the US Geological Survey and headed up the Asia Pacific part of their World Energy Assessment that was released in 2000. In 2007 he moved to Australia and worked with the CSIRO where he headed up their oil and gas exploration team. He joined the Australian School of Petroleum at the University of Adelaide in 2014 as the State Chair in Petroleum Geology and was the Head of School from February 2016 to December 2019. His research interests are in unconventional petroleum resources, stratigraphy and resource assessments. |
References
Alexander, E. M., Sansome, A., and Cotton, T. B. (1996). Lithostratigraphy and environments of deposition. In ‘The Petroleum Geology of South Australia. Vol. 2: Eromanga Basin’. South Australia. Department of Mines and Energy. Report Book 96, 1–129.Buatois, L. A., and Mángano, M. G. (1998). Trace fossil analysis of lacustrine facies and basins. Palaeogeography, Palaeoclimatology, Palaeoecology 140, 367–382.
| Trace fossil analysis of lacustrine facies and basins.Crossref | GoogleScholarGoogle Scholar |
Department of State Development (2019). Prospectivity of the Cooper Basin. Vol. 2017. DEM, Adelaide, South Australia.
Jell, P. A. (Ed) (2013). ‘Geology of Queensland.’ (Geological Survey of Queensland: Brisbane.)
Kobelt, S. J. (2014). ‘Palaeogeographic Mapping and Depositional Trends of the Patchawarra Formation within the Tenappera Region, Cooper Basin.’ (University of Adelaide: Adelaide.)
Lockhart, D., Riel, E., Sanders, M., Walsh, A., Cooper, G., and Allder, M. (2018). Play-based exploration in the Southern Cooper Basin: a systematic approach to exploration in a mature basin. The APPEA Journal 58, 825–832.
| Play-based exploration in the Southern Cooper Basin: a systematic approach to exploration in a mature basin.Crossref | GoogleScholarGoogle Scholar |
Moscariello, A., Arlaud, F., Akhtman, Y., Anselmetti, F. s., and Lemmin, U. (2012). Searching the Rhone Delta Channel in Lake Geneva since François Alphonse Forel. Archives des Sciences 65, 103–118.
Stow, D. A. (2005). ‘Sedimentary Rocks in the Field: A Color Guide.’ (Manson Publishing: London.)
Strong, P., Wood, G., Lang, S. C., Jollands, A., Karalaus, E., and Kassan, J. (2002). High resolution palaeogeographic mapping of the fluvial-lacustrine Patchawarra Formation in the Cooper Basin, South Australia. The APPEA Journal 42, 65–81.
| High resolution palaeogeographic mapping of the fluvial-lacustrine Patchawarra Formation in the Cooper Basin, South Australia.Crossref | GoogleScholarGoogle Scholar |
Zavala, C., and Pan, S. (2018). Hyperpycnal flows and hyperpycnites: origin and distinctive characteristics. Lithologic Reservoirs 30, 1–18.
