No abstract available

Paper supporting presentation of the 2007 Offshore Petroleum Explroation AReas at the Australian Petroleum Production and Exploration Association (APPEA) Conference, Adelaide, 16th April 2007.

Paper to accompany presentation of teh 2006 Offshore Petroleum Exploraiton Areas, give at the annual Australian Petroleum Production and Exploration Association (APPEA) conference, Gold Caost 7th to 11th May 2006.

The Timor Gap airborne laser fluorosensor (ALF) MkII survey was flown in 1989 by BP over the northern Bonaparte Basin (Sahul Platform, Sahul Syncline and Malita Graben). The MkII system used a 308nm laser wavelength, which is longer than the 266nm used in the later MkIII system. The Raman peak wavelength is 344nm (293nm MkIII) and the fluorescence region is 370nm to 580nm (320nm to 580nm MkIII). 208 lines were acquired at about 1,900m spacing in a NW-SE orientation and a flying height of 100m. A total of 1,860,650 spectra were collected at an average spacing of 16.9m to 28.5m. About 36,000 km of line data were acquired. Each recorded spectrum is the average (or sum) of ten detected spectra. The averaging was done to reduce the data recording rate, which was limited by the available hardware. The survey was interpreted using the ALF_Explorer software that consists of a database linked to a set of data processing, analysis and display modules. A total of 392 fluors were interpreted out of the 439,972 recorded spectra. 68 of these are located in a single patch near the Jabiru Field. This patch contains many very large fluors.

Restricted on advice from A. Barrett

Restricted on advice from A. Barrett

Between 2006 and 2011, Geoscience Australia has acquired deep crustal seismic reflection and magnetotelluric surveys as a major component of the Australian Government's Onshore Energy Security Program (OESP). All surveys have been conducted in collaboration with the relevant state or NT geological survey. The Seismic Acquisition and Processing Project provides precompetitive data for developing new geological frameworks for assessment of onshore hydrocarbon, geothermal and uranium resources. The Onshore Petroleum Project provides interpretation of the seismic data in frontier basins with petroleum potential and an assessment of the petroleum prospectivity of these basins. Seismic data can reveal basin and crustal architecture for potential hydrocarbons, image potential hot rocks (granites), and identify potential uranium deposit settings, such as craton margins and unconformities.

This study focuses on the changes in the stable carbon (d13C) isotopic composition of the saturated and aromatic hydrocarbons in western Australian crude oils through time. From this extensive dataset, carbon and hydrogen (dD) isotopic compositions of individual C7+ n-alkanes were obtained for the major genetic oil families. The samples originate from the Arafura, Bonaparte, Browse, Canning and Perth basins, with source ages that span the Cambrian to the Cretaceous. Complementary biomarker analyses provide insights into the type of organisms preserved in the source rock, its lithology and depositional environment, as documented by Geoscience Australia and GeoMark (2005). This study shows that the line used to separate a global set of marine and non-marine oils by Sofer (1984), is not particularly useful for western Australian oils (Figure 1). Using the combination of bulk and n-alkane-specific d13C isotopic profiles, oil families of Palaeozoic and Mesozoic age can be distinguished. From the Early to the Late Palaeozoic, Australian oils have become isotopically more enriched in 13C. The most depleted d13C value of -32.0 is recorded for the saturated hydrocarbon fraction (d13Csat) of a Cambrian oil-stain in the Arafura Basin. d13Csat values of about -31 are recorded for Ordovician oils from the Canning Basin, with slightly more enriched values (mean d13Csat = -29.3) being obtained for Late Devonian marine oils in this basin. Early Carboniferous marine oils from the Bonaparte and Canning basins have mean d13Csat values in the order of -28. Permian terrestrially sourced wet gases/condensates are some of the most 13C-enriched samples from western Australian, with values of around -24.6 being recorded in the Bonaparte Basin and -25.7 in the Perth Basin. Early Triassic Perth Basin oils have extremely depleted saturated hydrocarbon isotopic values of around -32 that are not as pronounced in the aromatic hydrocarbon fraction (mean d13Carom = -29.9), separating them from the Ordovician Canning Basin oils. Jurassic oils from the Bonaparte, Browse and Carnarvon basins exhibit a range in their d13Csat values from -26.1 to -27.8, due to generation from multiple source rocks throughout the oil window. Their source rocks were deposited in fluvio-deltaic to marine systems and contain varying amounts of land-plant material. Early Cretaceous marine oils of the Bonaparte and Browse basins have depleted d13Csat values in the order of -30.2 and -28.6 respectively, and can be differentiated from the Early Carboniferous oils on their n-alkane-specific isotope profiles. The n-alkane-specific d13C isotopic profiles of the Palaeozoic and Mesozoic oils and condensates characteristically follow the same trend as the bulk d13C isotopic values. The n-alkane-specific dD isotopic profiles typically complement those of the carbon isotopic profiles for the oils derived from marine source rocks. The carbon and hydrogen profiles exhibit distinct differences in oils that originate from either non-marine systems, or, in the case of the Triassic aged Perth Basin oils, a restricted anoxic marine environment.

Brief description of current and forward program in offshore frontier basins.

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 opportunites to test exisiting 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. This year, two Release Areas offer exploration potential in the under-explored eastern deep-water 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.