Using numerous illustrations this comprehensive black and white resource describes the formation, trapping and uses of natural gas as a non-renewable energy source. The exploration and recovery methods of gas are described, as are Australia's natural gas potential and environmental issues such as greenhouse gases. This 110 page booklet includes student activities with suggested answers. Suitable for secondary Years 9-12.

A range of geophysical indicators have been used to infer the presence of shallow gas in the Arafura Sea. The existence of shallow gas has been confirmed by the analysis of core material obtained during the survey. This sampled gas has a microbial origin related to decay of organic matter in Holocene mud-filled channels. However, geophysical data indicates that another source of gas exists in deeper parts of the sedimentary section and this gas appears to be migrating up from depth. Intense pockmark fields (~350/km2) are often developed above the mud-filled channels but they have also been recorded away from these channels. The development and density of the pockmark fields appears to be related to sea bed sediment type, microbial gas production within the mud-filled channels and supply of fluids from deeper within the sedimentary section. Correlation of sub-bottom profile data with conventional seismic data also indicates that there are links between deep first-order Proterozoic faults, second-order Jurassic faults and third-order faults to sea bed observed in sub-bottom profiles. The detailed sea bed mapping carried out during the survey has also shown correlations between habitat and biodiversity of various benthic fauna. Areas of high biodiversity and abundance generally correlated with harder substrates. In these areas, sea whips and fans, soft corals, hydroids, crinoids and octocorals were frequently identified, with sessile benthos extending up to ~50cm in height. The extensive areas of soft substrate commonly exhibited low-relief benthos which often covered less than 5% of the surface area. Such areas were also frequently noted for pockmark fields and the general uniformity of the environment.

Australia has a thriving oil and gas industry with expanding infrastructure and many exploration opportunities. Geologically the country contains potential for large oil and gas discoveries with extensive sedimentary basins. Australia is also one of the world leaders in providing low cost geological data with an open Acreage Release process and competitive taxation regimes. Politically Australia is very stable with a very high standard of living and a long-standing democratic culture based on the rights of the individual and the rule of the law. There is a free market philosophy which welcomes foreign investment - Australia has no mandatory local equity requirements and has no government owned oil companies. Government facilitation of investment includes fast-tracking of approvals processes for major projects. This CD provides some basic Australia data including: Oil and Gas Resources of Australia 2003 This publication is the definitive reference on exploration, development and production of Australia's petroleum resources. It covers exploration, reserves, undiscovered resources, development, coalbed methane resources, production, crude oil and shale oil and supporting information and statistics. It includes a forecast of Australia's crude oil and condensate production up to the year 2020, and sustainability indicators for petroleum resources. Information on Australia's petroleum data availability is also included. An estimate of Australia's undiscovered oil and gas potential and a review of geological sequestration of carbon dioxide in Australia is included. Australian Research and Promotional Material Australian research includes research papers for Australia, Australia regions (Northwest Shelf and the Southern Margin) and CO2 Sequestration. Promotional materials refer to pamphlets which outline geological products available from Geoscience Australia and contacts for obtaining these products. This material is grouped by region with the research papers. Geoscience Australia Online Databases Demonstration The Geoscience Australia Petroleum Databases Demonstration is a Microsoft Powerpoint presentation containing instructions on how to use Geoscience Australia's online Petroleum Databases located at: www.ga.gov.au/oracle/apcrc/ This output represents the data which is considered open file and commercial-in-confidence. Petroleum Databases available at Geoscience Australia include: the Australian Geological Provinces Database, the Petroleum Information Management System (PIMS) GIS , the National Petroleum Wells Database and the National Geoscience GIS

Legacy product - no abstract available

Natural gas is Australia's third largest energy resource after coal and uranium but despite this economic importance, the gas origin is not always recognized. To address this, isotope and geochemistry data have been collated on 850 natural gases from all of Australia's major gas provinces with proposed source ages spanning the earliest Paleozoic to the Cenozoic. Unaltered natural gases have a thermogenic origin ('13C methane ranges between -49 and -27'; 'D methane ranges between -290 and -125'). Microbially altered natural gases were identified primarily on the basis of 13C and D enrichments in propane and/or 13C depletion in methane and/or 13C enrichment in CO2. The carbon isotopic composition of the gas source has been estimated using '13C iso-butane as a surrogate for '13C kerogen while for gases where biodegradation is moderate to severe, '13C neo-pentane provides an alternative measure. The '13C kerogen of gas source rocks range from -47 to -22' with the older Paleozoic sources and marine kerogen amongst the most depleted in 13C. The '13C CO2 also provides an insight into crustal- and mantle-derived components while '15N N2 (-6.0 to 2.3' for N2 up to 47 %) distinguish between organic and inorganic (groundwater) inputs. This dataset provides a better understanding on the source and preservation history of Australian gas accumulations with direct implications on improving exploration success.

Legacy product - no abstract available

Legacy product - no abstract available

The article provides an annula update on Australia's energy scenarion, focussing on offshore oil and gas exploration and production and advertsing the current open acreage release round.

ORIGIN AND USE OF HELIUM IN AUSTRALIAN NATURAL GASES C. Boreham1, D. Edwards1. R. Poreda2, P. Henson1. 1 Geoscience Australia, Canberra, Australia; 2 University of Rochester, NY, USA Over 800 natural gases representative of Australia's hydrocarbon-producing sedimentary basins have been analyzed for their helium (He) content and around 150 gases for their helium isotopic composition, supplemented by isotopic compositions of the higher noble gases. Australian natural gases have helium abundances to over 10%, with the highest values in the Amadeus Basin, in central Australia, while 3He/4He ratios range from around 0.01 to 4.2 Ra (Figure 1). The onshore Gunnedah Basin of southeastern Australia and the offshore Bass and onshore/offshore Otway basins in southern Australia show the highest 3He/4He ratios, indicating a significant mantle contribution. Interestingly, the offshore Gippsland Basin, adjacent to the Bass Basin, has slightly lower 3He/4He ratios. In the Gunnedah Basin, the associated CO2 has a relatively low abundance compared to extreme concentrations of CO2 in some Otway Basin wells, which are associated with recent volcanism. The onshore Bowen and Cooper basins of eastern Australia, where natural gases are predominately sourced from Permian coals, show intermediate 3He/4He ratios with the former having a higher mantle contribution. At the other end of the spectrum, low 3He/4He ratios characterize natural gases of the offshore North West Shelf (Bonaparte, Browse, Carnarvon) and onshore/offshore Perth basins in northwestern and southwestern Australia, respectively, and radiogenic helium predominates. Hence the sometimes extensive volcanic activity and igneous intrusions in these western basins is not expressed in the helium isotopes. The accompanying high CO2 contents (up to 44%) of some of these North West Shelf gases, together with the carbon isotopic composition of CO2, infer an inorganic source most likely from the thermal decomposition of carbonates. The geochemical data suggest that the origin of helium in Australian natural gas accumulations is region specific and complex with the component gases originating from multiple sources. The relative low CO2/3He ratio for many natural gases indicates a systematic loss of CO2 from most basins. The process by which CO2 has been lost from the system is most likely associated with precipitation of carbonates (Prinzhofer, 2013). The age of the source (and/or reservoir) rock has a primary control on the helium content with radiogenic 4He input increasing with residence time (Figure 1). References: Prinzhofer, A., 2013. Noble gases in oil and gas accumulations. The Noble Gases as Geochemical Tracers. Springer. 225-245.

This work is a baseline study used to underpin the role of bacteria in the alteration and mineralisation of CO2 during geological storage following its injection into depleted natural gas reservoirs. In doing so it is paramount to first understand and characterise natural deep-earth biological systems. Here we report the molecular and isotopic signatures of gas, oil and formation waters from the biodegraded Tubridgi gas field. The onshore Tubridgi gas field is thought to lie at the end of a fill-spill chain from the offshore major oil and gas accumulations in the southern Barrow Sub-basin. An initial oil column at Tubridgi has been subsequently displaced by later gas charges. The Tubridgi gas is very dry (%methane/%ethane ~ 1000). Methane is isotopically light (delta13C = -49.2) and is depleted in 13C by ~10 compared to non-biodegraded gases from the Barrow Sub-basin. This, together with an isotopically heavy CO2 (delat13C = +1.8; ~6 enriched in 13C compared to non-biodegraded gas), suggests a major biogenic methane input derived from anaerobic methanogenic bacteria. The carbon isotopic composition of ethane (delta13C = -27) is only slightly enriched in 13C compared to non-biodegraded gas. Much larger enrichments occur in the hydrogen isotopes of ethane (deltaD = +42; ~180 enriched in D compared to non-biodegraded gas), suggesting anaerobic biodegradation has completely removed the higher (C3-C5) wet gases. This is supported by the less severely biodegraded Barrow Sub-basin natural gases, which can show up to 17 and 225 enrichment in 13C and D of propane, respectively, compared to non-biodegraded Barrow gas. Interestingly, the strong biogenic methane input seen in the carbon isotopes is not expressed in the hydrogen isotopes of methane (deltaD = -177 ), which is similar to the non-biodegraded gas. The Tubridgi-2 residual biodegraded heavy oil has a low API gravity of 23.5o and is the most sulphur-rich oil (S= 1.14 %) of all Australian oils. The gas-chromatogram displays an unresolved complex mixture with no n-alkanes. The level of biodegradation is heavy with 25-norhopane being present but no alteration of the sterane distributions are observed. The biomarker distribution of the Tubridgi-2 oil implies derivation from Late Triassic Middle Jurassic calcareous-influenced source rock deposited in a sub-oxic marine environment. Organic material extracted from the Tubridgi formation waters associated with the biodegraded gases mainly reflect the biodegraded oil input since very little low molecular weight `organics' was detected. Thus, the neutral organic compounds extracted at pH 7 are dominated by a homologous series of C19-C30 n-alkanes, while organic compounds extracted from acidified (pH 1) waters include a homologous series of C8-C18 n-alkylmonocarboxylic acids. The mutual exclusion between carbon numbers of the n-alkanes and n-alkylcarboxylic acids suggests a precursor-product relationship mediated by bacteria. However, the major organic components in the "acid" fraction are unidentified N and O containing compounds, most likely metabolic by-products of the biological activity. Cell counting is in progress, which will give an independent measure of the diversity and activity of the biological community within the reservoir.