Restricted on advice from A. Barrett

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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

No product available. Removed from website 25/01/2019

Legacy product - no abstract available

Legacy product - no abstract available

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.

Introduction Australia has a thriving oil and gas industry with expanding infrastructure and many exploration opportunities. Geologically the country has the potential for large oil and gas discoveries within extensive sedimentary basins. Australia is also one of the world leaders in providing open-file geological data at a low cost, and an open Acreage Release process with 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 Australian data including: Oil and Gas Resources of Australia 2002 The Oil and Gas Resources of Australia 2002 (link to Pdf ) publication is the definitive reference on exploration, development and production of Australia's petroleum resources. It covers exploration, reserves, undiscovered resources,development, coal-bed methane resources, production, crude oil and shale oil and supporting information and statistics. An estimate of Australia's undiscovered oil and gas potential and a review of geological sequestration of carbon dioxide in Australia is also included. Australian Research and Promotional Material The Australian Research and Promotional Material section includes selected scientific publications on Australia and CO2 Sequestration. Promotional pamphlets are also included outlining geological products available from Geoscience Australia and contacts for obtaining these products. Research and Promotional material is grouped into regions: 1. Regional Australian Studies 2. North West Shelf 3. Australian Southern Margins 4. Carbon Dioxide Sequestration 5. Geoscience Australia Online Databases Demonstration The Geoscience Australia Petroleum Databases Demonstration is in PDF format and contains instructions on how to use Geoscience Australia's web-based Petroleum Databases located at: www.ga.gov.au/oracle/apcrc/ The Petroluem Databases, available through the Geoscience Australia website, contain open-file data and include: the Australian Geological Provinces Database, the Petroleum Information Management System (PIMS) GIS, the National Petroleum Wells Database and the National Geoscience GIS. Relevant Government and Industry Web Links Including: 1- Key Government Links for Offshore Acreage 2- Key Government Links for Onshore Acreage 3- Industry Links

Genetic relationships, identified using a combination of molecular and isotopic (carbon and hydrogen) compositions, have been found between natural gases, oils, oil stains, bitumens and potential source rocks in the onshore and offshore Otway Basin. The gas-gas, gas-oil and oil-source correlations herein challenge the validity of some previously accepted oil families and re-enforces the strong compartmentalisation of petroleum systems in the Otway Basin. Previous geochemical studies in the Otway Basin, mainly focussed on the oils and oil stains, have established that the Otway Basin hosts the most diverse array of petroleum systems within Australia. Up to five different oil families have previously been identified. These oils are sourced from a wide range of depositional environments from fresh to saline lacustrine, fluvio-lacustrine to peat swamp and marine, with suspected effective source rock ages from Late Jurassic to Late Cretaceous. Such depositional settings are consistent with the progressive development of source rocks facies intimately linked to basin development from initial rifting to thermal sag. It is now concluded that there is no indigenous representation of the saline lacustrine oil population in the Otway Basin. The geochemical signal is attributed to downhole contamination from gilsonite; a solid bitumen from the Eocene Green River Formation, USA. Oils stains are thought to be a result of primary migration from mature source rocks into juxtaposed sands and are not a strong advocate for secondary oil migration fairways. The natural gases show a strong geochemical association with their respective oils, suggesting that both are generated together from the same source. Also the gases and oils and their effective source rocks have a strong stratigraphic and geographic relationship, indicating mainly short- to medium-range migration distances from source to trap. Gas and oil in the western Otway Basin are sourced from the fluvio-lacustrine Casterton Formation?Crayfish Group sediments while in the eastern Otway Basin the gas and oil from the Shipwreck Trough and its onshore extension are from the coaly Eumeralla Formation sediments. Gas and oil in the central Otway Basin have a mixed source but predominantly are of Eumeralla Formation source Multiple charge histories are also evident with the widespread influx of overmature, dry gas focused in the western Otway Basin and more recently magmatic CO2 influx. Successive natural gas charges have the potential to displace and/or alter the composition of the pre-existing reservoired gas and oil. In-reservoir biodegradation of oil is seen in the shallower reservoirs but this is not a significant risk in the Otway Basin since nearly all reservoired petroleum is below the temperature/depth limits for biologically sustainable life.