Exploration for Unconventional Hydrocarbons in Australia reached a new milestone when Beach Energy announced the first successful flow test of a shale gas target in the Cooper Basin. The ever expanding coal seam gas industry on Australia's east coast in addition to the large resource potential of shale and tight gas in Australia's eastern basins has put Australia firmly on the radar of many local and international exploration companies. Over the next 12 months Geoscience Australia in collaboration with its counterparts in the State and Territory resource and energy departments will begin an assessment of Australia's coal seam gas, shale gas and oil and tight gas resource potential. Capitalising on decades of high quality geological data held by the Commonwealth and the States and Territories, the aim of this collaboration is to develop nationally consistent assessment methodologies and provide robust national resource estimates in an internationally accepted standard. Overall, the programme aims to answer the 'where' and 'how much' questions for government, as well as provide this new industry with pre-competitive data and tools for comparing exploration opportunities. The immediate goal is to provide a first-pass, high level estimate of the likely resource volumes, which will be reported in the second edition of the Australian Energy Resource Assessment (published by RET). The longer term work program aims to assess Australia's onshore basins in terms of their resource potential and provide pre-competitive data to industry. To achieve this, several geological techniques will be applied including, but not limited to, geochemical screening, mapping of source rock occurrences and their distributions as well as physical rock property studies.

Presentation delivered on 9 March 2012 by Marita Bradshaw.

Promotional flyer describing the GA programme in national unconventional hydrocarbon prospectivity and resource assessment commenced in 2011 by the Onshore (Unconventional) Hydrocarbons Section, Basin Resources Group, Energy Division.

Extended abstract version of short abstract accepted for conference presentation GEOCAT# 73701

As part of the Offshore Energy Security Program (2007-2011), Geoscience Australia (GA) undertook an integrated regional study of the deepwater Otway and Sorell basins to improve the understanding of the geology and petroleum prospectivity of the region. Major outputs of this study include: - New interpretations of basement architecture and structural fabric resulting in the recognition of the Avoca-Sorell Fault System as a major control on sedimentary basin development, - Extension of the tectonostratigraphic framework of Krassay et. al. (2004) into the deepwater Otway and Sorell basins, leading to new insights into their structural and accommodation histories of both basins, and - Petroleum systems modelling indicating that these basins are mature for oil and gas generation.

Geoscience Australia has begun a systematic evaluation of the shale gas/oil (unconventional) resource potential of Australia's onshore sedimentary basins. According to the Australian Gas Resource Assessment 2012 [1] Australia's unconventional gas resource endowment is likely to be greater than its estimated total conventional gas resources with some basins likely to have significant unconventional oil potential. An assessment of Australia's unconventional resource potential will use methodology developed by the United States Geological Survey based on statistically derived estimates of hydrocarbon recovery from actual production data, or basin analogues in data-poor areas. The Georgina Basin, containing Proterozoic-Paleozoic age sediments and covering an area of ~325,000 sq. km in south-central Australia, is the first basin to be assessed and since there is no petroleum production history, suitable analogues will be sought. The assessment also relies heavily on the updated stratigraphy, tectonic history, petrography, geochemistry and petroleum systems modelling, with a discussion emphasis on the latter two datasets. The Georgina Basin is host to basin-wide oil staining and contains proven petroleum systems with relative short migration distances from source to trap, which likely represent multiple hybrid unconventional systems and breached conventional reservoirs. For example, the result of localised migration is exemplified in the composition of residual free hydrocarbons from organic-rich mudstones in which light and heavy hydrocarbons were recorded in samples 3 m apart. The most prolific oil-prone effective sources occur in the Middle Cambrian Thorntonia Limestone (early to middle Ordian) and overlying Arthur Creek Formation (latest Ordian to late Boomerangian). These source rocks were diachronously deposited from west to east under marine anoxic bottom waters, which periodically extended into the photic zone, and represent the local expression of a prolonged Middle-Late Cambrian oceanic anoxic event that lead to deposition of organic-rich 'black shales' on a global scale. The oil stains are varyingly altered by biodegradation and are geochemically characterised by a strong isotopic depletion in 13C, high abundance of monomethylalkanes, C15-C23 odd carbon number predominance for n-alkylcyclohexanes, C27 slightly dominant over C29 desmethylsteranes and high content of tricyclic terpanes. Source richness and maturity estimates are derived from Rock Eval, saturated and aromatic hydrocarbons, FAMM and hydrogen isotopic relationships between n-alkanes and isoprenoids. For example, the 'hot shale' unit comprising predominately dolostone at the base of the Arthur Creek Formation, currently the focus of drilling activity for unconventional hydrocarbons, has TOC and HI up to 15.5 % and 500 mg hydrocarbons/g TOC, respectively. Maturity levels range from the early oil to early dry gas windows. This unit appears to have all the geochemical pre-requesites for a significant unconventional hydrocarbon play. Geohistory modelling using formation-specific compositional kinetics indicates petroleum generation and expulsion begins in the latest Cambrian-Early Ordovician due to relatively rapid burial of the Arthur Creek Formation. Deposition ends with the start of the Alice Springs Orogeny and following uplift and erosion during the Devonian, hydrocarbon generation ceases. An unconventional petroleum resource assessment of the Georgina Basin will be undertaken in February 2013 and available for benchmarking and refinement against any future shale gas and shale oil production. [1] Geoscience Australia and Bureau of Resource and Energy Economics, 2012, Australian Gas Resource Assessment 2012, Canberra, 56 p. https://www.ga.gov.au/products/servlet/controller?event=GEOCAT_DETAILS&catno=74032

In this study detailed mapping of seismic data from the 1529 km2 Beagle multi-client 3D seismic survey was undertaken to provide a better understanding of the geological history of the central Beagle Sub-basin. Situated in the Northern Carnarvon Basin, oil discovered at Nebo 1 in 1993 indicated the presence of at least one active petroleum system. The central part of the sub-basin has a N-trending horst-graben architecture. Two rifting events from the Hettangian to Sinemurian and the Callovian to Oxfordian were identified. A series of tilted fault blocks formed by the rifting events were locally eroded and progressively draped and buried by post-rift thermal subsidence sedimentation. Mapping indicated the Post-rift I Lower Cretaceous Muderong Shale regional seal is anomalously thin or absent in the intra-horst graben area. Burial history 1D modelling indicates that at Nebo 1, the most rospective potential source rocks within the Middle-Upper Jurassic section where in the early oil window; however, if present within the Beagle and Cossigny trough depocentres, these sediments would have entered the oil window prior to the deposition of the Muderong Shale regional seal. Upper Jurassic shales provide seal for the oil pool intersected in Nebo 1. The Tertiary section is dominated by a prograding carbonate wedge which has driven a second phase of thermal maturation observed in the Paleogene (Nebo 1) and Miocene (Manaslu 1). Potential source rocks are currently at their maximum depth of burial and maximum thermal maturity. Modest inversion on some faults prior to the Early Cretaceous has created traps and if source rocks retain generative potential, favourable traps could be now actively receiving hydrocarbon charge. Potential plays include compaction folds over tilted horst blocks, drape and small inversion induced anticlines, basin-floor fans and intra-formational traps. Deep faults may act as conduits for hydrocarbons migrating from mature potential source rocks into Jurassic to Cretaceous plays. Younger sediments appear to lack access to migration pathways provided by deeper faults.

Exploration for Unconventional Hydrocarbons in Australia reached a new milestone when Beach Energy announced the first successful flow test of a shale gas target in the Cooper Basin. Significant exploration activity is being seen in the Amadeus, Pedirka and Georgina basins and Beetaloo Sub-basin, while little is known of the potential of many other Central Australian basins. The globally acknowledged large resource potential of coal seam gas, shale and tight gas on the continent in addition to low sovereign risk has put Australia firmly on the radar of many local and international exploration companies. Over the next 12 months Geoscience Australia in collaboration with its counterparts in the State and Territory resource and energy departments will undertake an initial assessment of Australia's unconventional hydrocarbon resource potential. Capitalising on decades of high quality geological data held by the Commonwealth and the States and Territories, the programme aims to compile these data using nationally consistent assessment methodologies that ultimately provide robust figures in an internationally accepted standard. The immediate goal is to provide a first-pass, high level estimate of the likely resource volumes, which will be reported in the second edition of the Australian Energy Resource Assessment (published by RET). The longer term work program aims to assess Australia's onshore basins in terms of their resource potential and provide pre-competitive data to industry. To achieve this, several geological techniques will be applied including, but not limited to, geochemical screening, mapping of source rock occurrences and their distributions as well as physical rock property studies.

A movie flythrough displaying various geological and geophysical data used for petroleum prospectivity assessment of the offshore northern Perth Basin

Full paper version of the short abstract (GEOCAT# 73702) previously submitted and accepted by conference organisers