The 2012 Australian offshore acreage release includes exploration areas in four southern margin basins. Three large Release Areas in the frontier Ceduna Sub-basin lie adjacent to four exploration permits granted in 2011. The petroleum prospectivity of the Ceduna Sub-basin is controlled by the distribution of Upper Cretaceous marine and deltaic facies and a structural framework established by Cenomanian growth faulting. These Release Areas offer a range of plays charged by Cretaceous marine and coaly source rocks and Jurassic lacustrine sediments. In the westernmost part of the gas-producing Otway Basin, a large Release Area offers numerous opportunities to test existing and new play concepts in underexplored areas beyond the continental shelf. Gas and oil shows in the eastern part of the Release Area confirm the presence of at least two working petroleum systems. In the eastern Otway Basin, several Release Areas are offered in shallow water on the eastern flank of the highly prospective Shipwreck Trough and provide untested targets along the eastern basin margin southward into Tasmanian waters. To the south, a large Release Area in the frontier Sorell Basin provides the opportunity to explore a range of untested targets in depocentres that formed along the western Tasmanian transform continental margin. Two Release Areas offer exploration potential in the under-explored eastern deepwater part of the Gippsland Basin. Geological control is provided by several successful wells indicating the presence of both gas and liquids in the northern area, while the southern area represents the remaining frontier of the basin.

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 geological investigation, directed mainly towards the assessment of oil potentialities of the Basin, was commenced in 1948 by the Bureau of Mineral Resources, Geology and Geophysics when a small geological party carried out a reconnaissance of the Minilya River area. Since then up to seven geologists of the Bureau under the direction of M. A. Condon have been mapping the area in some detail each year in order to determine the stratigraphical sequence and its variations, regional structure, and the anticlinal structures and their extent. In addition to the regional mapping the two largest anticlines were mapped in detail. Geophysical work (gravity and seismic) has been carried out by the Geophysical section of the Bureau (see Record 1954/44). More recently, Seismograph Services Ltd. carried out a seismic survey for West Australian Petroleum Pty. Ltd. - mainly for the purpose of checking on the location of its first deep test, which is now being drilled on the Rough Range Anticline with some encouraging results to date. Palaeontological, petrographical and chemical examinations of specimens collected in the field are still continuing by specialists of the Bureau and outside.

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

Release Area W11-18 is a very large block over the offshore northern Perth Basin, covering parts of the Abrolhos, Houtman and Vlaming sub-basins and the Beagle and Turtle Dove ridges. Geoscience Australia (GA) has assessed the petroleum prospectivity of this area as part of the Australian Government's Offshore Energy Security Program. This assessment includes the first published synthesis of data from fourteen new field wildcat wells drilled in this part of the basin since the Cliff Head-1 discovery (2001), and the interpretation of new regional 2D seismic data acquired during GA survey 310 (2008-2009). A refined tectono-stratigraphic model for the offshore basin provides insights into basin evolution and prospectivity. Oil has been produced since 2006 from the Cliff Head oil field in WA-31-L, which is directly adjacent to Release Area W11-18. Three petroleum discoveries are included within the Release Area, with oil and gas in Dunsborough-1, and gas in Frankland-1 and Perseverance-1. These accumulations are reservoired in Permian sandstones and have primarily been sourced from the Hovea Member of the Kockatea Shale, which has also sourced the majority of producing oil and gas fields of the onshore Perth Basin. New seismic data show Permo-Triassic strata that are stratigraphic equivalents of the productive onshore and nearshore Perth Basin petroleum system, also occur within Permian half-graben in the outer Abrolhos and Houtman sub-basins. Source rock, oil stain and fluid inclusion sampling from this interval suggest that the proven onshore-nearshore petroleum system is also effective and widespread in the offshore. There is also evidence for an active Jurassic petroleum system within the Release Area. The Release Area offers a range of plays in a variety of water depths, predominantly less than 200 m, and is highly prospective for oil and gas.

Vertical geochemical profiling of the marine Toolebuc Formation, Eromanga Basin - implications for shale gas/oil potential The regionally extensive, marine, mid-Cretaceous (Albian) Toolebuc Formation, Eromanga Basin hosts one of Australia's most prolific potential source rocks. However, its general low thermal maturity precludes pervasive petroleum generation, although regions of high heat flow and/or deeper burial may make it attractive for unconventional (shale gas and shale oil) hydrocarbon exploration. Previous studies have provided a good understanding of the geographic distribution of the marine organic matter in the Toolebuc Formation where total organic carbon (TOC) contents range to over 20% with approx. half being of labile carbon and convertible to gas and oil. This study focuses on the vertical profiling, at the decimetre to metre scale, of the organic and inorganic geochemical fingerprints within the Toolebuc Formation with a view to quantify fluctuations in the depositional environment and mode of preservation of the organic matter and how these factors influence hydrocarbon generation thresholds. The Toolebuc Formation from three wells, Julia Creek-2 and Wallimbulla-2 and -3, was sampled over an interval from 172 to 360m depth. The total core length was 27m from which 60 samples were selected. Cores from the underlying Wallumbilla Formation (11 samples over 13m) and the overlying Allaru Mudstone (3 samples) completed the sample set. Bulk geochemical analyses included %TOC, %carbonate, %total S, -15N kerogen, -13C kerogen, -13C carbonate, -18O carbonate, and major, minor and tracer elements and quantitative mineralogy. More detailed organic geochemical analyses involved molecular fossils (saturated and aromatic hydrocarbons, and metalloporphyrins), compound specific carbon isotopes of n-alkanes, pyrolysis-gas chromatography and compositional kinetics. etc.

Australia's southern continental margin hosts rich oil and gas resources and offers huge potential for future discoveries. Most of Australia's oil has been produced from the Gippsland Basin, located in the easternmost part of the southern rift system. With all the petroleum system elements and processes in place, the basin contains Australia's only billion barrel oil fields. These giant accumulations are sourced from rich liquid-prone coaly and carbonaceous source rocks. In contrast, the western two-thirds of the southern margin is occupied by one of the largest frontier provinces in Australia - the Bight Basin. The thick sedimentary succession in the Bight Basin (>15 km) and its evolution from local half-graben depocentres during the Jurassic, to an extensive sag basin in the Early Cretaceous and passive margin during the Late Cretaceous to Holocene, suggests that there is significant potential for the presence of multiple petroleum systems across the basin. The Ceduna Sub-basin in the eastern Bight Basin is currently the focus of renewed exploration efforts. The key to its petroleum prospectivity is the distribution of Upper Cretaceous marine and deltaic facies. Dredging of upper Cenomanian-Turonian organic-rich marine rocks has confirmed the presence of high quality potential source rocks in this section. These rocks are mature in the central part of the Ceduna Sub-basin and are likely to have generated and expelled hydrocarbons since the Campanian. Excellent reservoir rocks and potential intraformational seals are present in the Upper Cretaceous deltaic successions, and regional seals could be provided by Upper Cretaceous marine shales.

The under-explored deepwater Otway and Sorell basins lie offshore of southwestern Victoria and western Tasmania in water depths of 100-4,500 m. The basins developed during rifting and continental separation between Australia and Antarctica from the Cretaceous to Cenozoic and contain up to 10 km of sediments. Significant changes in basin architecture and depositional history from west to east reflect the transition from a divergent rifted continental margin to a transform continental margin. The basins are adjacent to hydrocarbon-producing areas of the Otway Basin, but despite good 2D seismic data coverage, they remain relatively untested and their prospectivity is poorly understood. The deepwater (>500 m) section of the Otway Basin has been tested by two wells, of which Somerset 1 recorded minor gas shows within the Upper Cretaceous section. Three wells have been drilled in the Sorell Basin, where minor oil and gas indications were recorded in Maastrichtian rocks near the base of Cape Sorell 1. Building on previous GA basin studies and using an integrated approach, new aeromagnetic data, open-file potential field, seismic and exploration well data have been used to develop new interpretations of basement structure and sedimentary basin architecture. Analysis of potential field data, integrated with interpretation of 2D seismic data, has shown that reactivated north-south Paleozoic structures, particularly the Avoca-Sorell Fault System, control the transition from extension through transtension to a dominantly strike-slip tectonic regime along this part of the southern margin. Depocentres to the west of this structure are large and deep in contrast to the narrow elongate depocentres to its east. Regional-scale mapping of key sequence stratigraphic surfaces across the basins has resulted in the identification of distinct basin phases. Three periods of upper crustal extension can be identified. In the north, one phase of extension in the Early Cretaceous and two in the Late Cretaceous can be mapped. However, to the south, the Late Cretaceous extensional phase extends into the Paleocene, reflecting the diachronous break-up history. Extension was followed by thermal subsidence, and during the Eocene-Oligocene the basin was affected by several periods of compression, resulting in inversion and uplift. The new seismic interpretation shows that depositional sequences hosting active petroleum systems in the producing areas of the Otway Basin are also likely to be present in the southern Otway and Sorell basins. Petroleum systems modelling suggests that if the equivalent petroleum systems elements are present, then they are mature for oil and gas generation, with generation and expulsion occurring mainly in the Late Cretaceous in the southern Otway and northern Sorell basins and during the Paleocene in the Strahan Sub-basin (southern Sorell Basin). The integration of sequence stratigraphic interpretation of seismic data, regional structural analysis and petroleum systems modelling has resulted in a clearer understanding of the tectonostratigraphic evolution of this complex basin system. The results of this study provide new insights into the geological controls on the development of the basins and their petroleum prospectivity.

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.

<p>This data package includes raw (Level 0) and reprocessed (Level 1) HyLogging data from 25 wells in the Georgina Basin, onshore Australia. This work was commissioned by Geoscience Australia, and includes an accompanying meta-data report that documents the data processing steps undertaken and a description of the various filters (scalars) used in the processed datasets. <p>Please note: Data can be made available on request to ClientServices@ga.gov.au