Restricted on advice from A. Barrett

Natural gases from all of Australia's major gas provinces have been examined using their molecular and carbon isotopic compositions in order to define source, maturity and secondary alteration processes.

2002 and 2003 may well prove to be pivotal years for petroleum exploration in Australia as we endeavour to meet our twin imperatives of finding more oil and using gas. Long term gas supply contracts have been signed with China and a number of key oil discoveries have been made both on and offshore. Deep water wells will be drilled that have the potential to usher in another phase of major oil discovery akin to bonanza of the 1960s, when the first steps into the offshore resulted in billion barrel discoveries in Bass Strait. By the close of the first successful cycle of exploration in Australia (1960 to 1972) all currently producing basins were identified as petroliferous, the major play types had been established and over 60% of Australia?s current oil reserves found. The key drivers of this phase were the access to new basins opened up by the move to offshore exploration and the stimulus to further exploration provided by discovery success. The same drivers are apparent now. Recent discoveries in the Perth, Carnarvon, Otway and Browse basins provide strong indications that a significant new cycle of exploration success is already underway. In many cases these finds represent the largest fields yet found in the basin or at least the largest in the last thirty years. The usual discovery history trend of declining field sizes over time has been turned on its head - clearly demonstrating that many of Australia?s currently producing basins still have a long way to run and encouraging further exploration efforts. Perhaps of even more importance to Australia?s long term liquids self sufficiency is the current deepwater drilling campaign which is stepping out beyond former geographic limits. The first wells in major Mesozoic depocentres on the outer margin of the North west Shelf and in the Great Australian Bight are being drilled with the potential to establish entirely new petroleum provinces.

The critical success factors which control hydrocarbon prospectivity in the Otway Basin have been investigated using petroleum systems approaches. Greater than 99% of the hydrocarbon inventory within the Victorian Otway Basin has been sourced from Austral 2 (Albian-Aptian) source rocks and these accumulations are typically located either within, or within approximately 3,000 m of source rock kitchens which are at peak thermal maturity at present day. Importantly, the zones of greatest prospectivity are located where these source rocks have been actively generating and expelling hydrocarbons throughout the Late Tertiary, primarily as a result of sediment loading associated with progradation of the Heytesbury shelfal carbonates. This peak generation window occurs at an average depth of approximately 2,500-3,500 m 'sub-mud' across much of the basin, which has allowed prospective hydrocarbon fairways to be mapped out, thereby highlighting areas of greatest prospectivity. It is believed that the spatial proximity of the actively generating source rocks to the accumulations is due to several factors, which includes overall poor fault seal in the basin (success cases occur where charge rate exceeds leakage rate) and relatively complex and tortuous migration fairways (which means that large volumes of hydrocarbons are only focussed and migrate for relatively short distances). etc

Legacy product - no abstract available

Legacy product - no abstract available

This Oil and Gas Resources of Australia 2008 publication is the successor to Oil and Gas Resources of Australia 2007 and continues as the definitive reference on exploration, development and production of Australia's petroleum resources. The tables describe: - wells drilled - seismic surveys - petroleum discoveries - petroleum reserves - production and development, including forecasts of crude oil and condensate from 2009 to 2025 and a listing of offshore facilities

Molecular and stable isotopic (carbon and hydrogen) analyses are being undertaken on fluid samples from offshore Australian gas accumulations, as part of a Geoscience Australia initiative to understand the origin, thermal maturity and degree of preservation of these economic resources. The geochemical data are available from Geoscience Australia's web site http://www.ga.gov.au/oracle/apcrc. Here, emphasis is placed upon documenting the natural gas compositions of the Exmouth Plateau and Exmouth Sub-basin (Fig. 1). It is apparent from the isotopic signatures of the non-combustible and combustible gases that several sources of gas are mixed within these accumulations, many of which have complex fill histories. These results were presented at the Combined National Conference of the Australian Organic Geochemists and the Natural Organic Matter Interest Group, Rottnest Island, Perth, WA, February 2006 (Edwards et al., 2006).

<p>The Roebuck Basin on Australia’s offshore north-western margin is the focus of a regional hydrocarbon prospectivity assessment being undertaken by the North West Margin Energy Studies Section (NWMES). This offshore program is designed to produce pre-competitive information to assist with the evaluation of the hydrocarbon resource potential of the central North West Shelf and attract exploration investment to Australia. <p>The recent oil and gas discoveries at Phoenix South 1 (2014), Roc 1 (2015-16), Roc 2 (2016), Phoenix South 2 (2016), Phoenix South 3 (2018) and Dorado 1 (2018) in the Bedout Sub-basin demonstrate the presence of a petroleum system in Lower Triassic strata. The current study aims to better understand this new petroleum system and establish its extent. <p>As part of this program, compositional and isotopic analyses were undertaken by Geoscience Australia on gas samples from the wells Roc 1 and Roc 2 and data from these analyses are released in this dataset.

<p>The onshore Canning Basin in Western Australia is the focus of a regional hydrocarbon prospectivity assessment being undertaken by the Exploring for the Future (EFTF) program; an initiative by the Australian Government dedicated to boosting investment in resource exploration in Australia. The four-year program led by Geoscience Australia focusses on the acquisition of new data and information about the potential mineral, energy and groundwater resources concealed beneath the surface in northern Australia and parts of South Australia. As part of this program, significant work has been carried out to deliver new pre-competitive data including new seismic, drilling of a stratigraphic well and the geochemical analysis of petroleum recovered from exploration wells. <p>Current conventional remaining gas resources of the Canning Basin are deemed limited (0.2 TCF; AERA, 2018), whereas unconventional gas resources are inferred to be extremely high, with estimated recoverable resources for shale gas and tight gas being 452.3 TCF (5% of P50,Table 2; AREA, 2018). This disparity arises from the high degree of uncertainty of key geological factors, particularly the poor constraints on source rock volumetrics, the lack of understanding of the volume of gaseous hydrocarbons generated and the origin and degree of thermal maturity of the gases. Carbon isotopic data are scarce and hydrogen isotopic data are non-existent, even though numerous gas discoveries have been made across the Lennard Shelf, Broome Platform and Fitzroy Trough following the initial discovery at Pictor 1 in 1984 by BHP Petroleum (Cadman et al., 1993; Jonasson, 2001). Indeed, gas samples have only been available for analyses since the drilling campaign by Buru Energy in 2010, and more recently, mud gases collected in IsoTubes are routinely sampled during drilling and presented in well completion reports (e.g. Cyrene 1; Nicolay 1, Paradise Deepening 1, Theia 1, Yulleroo 3 and Yulleroo 4). <p>This component of the EFTF program, evaluates the molecular and isotopic composition of natural gases from petroleum wells and a hot-spring seep at Mount Wynne, to constrain the much publicised resource potential inferred in this basin. Interpretation of these data will also assist with in the determination of their origin, and hence increase our understanding of the Larapintine Petroleum Supersystem, as proposed by Bradshaw (1983) and Bradshaw et al. (1984). All gas analyses in this study were undertaken by Geoscience Australia’s Organic Geochemistry Laboratory.