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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.
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Mineral deposits, although geographically small in extent, are the result of processes-which together form a mineral system-that occur, and can be mapped at, a variety of scales, up to craton-scale and larger. The mineral system approach has the benefit that in it focuses on critical processes and can include larger scales not always considered. Understanding the four-dimensional evolution of the crust, for example, is important, as it can provide critical constraints on the geodynamic history, the lithospheric architecture and development, and potentially identify metallogenic terranes. Constraining the nature and evolution of the crust is not easy, however, given its largely inaccessible nature. Just as the study of basaltic rocks has provided insight into the earth's mantle, granites, provide a window into the middle and lower continental crust. Studies of these rocks are enhanced by the use of isotopic tracers (e.g., U-Pb, Sm-Nd, Lu-Hf), long used to provide constraints on geological processes and components involved in those processes.
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Fugitive methane emissions, in particular relating to coal seam gas (CSG),has become an emerging issue in Australia over the last few years. There has been significant controversy in US regarding the magnitude of fugitive emissions during production from unconventional gas wells, with large differences in emissions reported between studies using different measurement approaches. . Preliminary research into a small number of Australia's unconventional fields suggest the average fugitive emissions per well are lower than that found in the US. The primary challenge is that the techniques for quantifying methane leakages are still at an early stage of development. Current methods for the small to medium scale use chamber based approaches or vehicles installed with fixed sampling lines and high precisions gas analysers. These technologies are promising, but generally have not been ground truthed in field conditions against known emission rates to estimate effectiveness. They also have limited application in environments where vehicle access is not possible. The Ginniderra facility is being upgraded to support a methane controlled release experiment in 2015. This will enable testing of and verifying methods and technologies for measuring and quantifying methane emissions. To address the absence of suitable techniques for emmission measurement at medium scales, several BOREAL lasers will be deployed which work at scales of 20-1000 m. It is also envisaged airborne techniques utilising laser and hyperspectral will be deployed, along with tomography work utilising multiple concurrent concentration measurements.
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The southwest margin is a complex and relatively poorly studied part of Australia's offshore continental region and includes the Southern Carnarvon, Perth and Mentelle basins, as well as the Naturaliste and Wallaby plateaus. A series of seismic profiles are interpreted, in conjunction with potential field data, to reassess the nature of the continent-ocean boundary (COB) across the region. Results highlight how the structural architecture of the margin varies significantly along strike according to the following criteria: a) the relative orientation of the margin with respect to the initial extension direction, b) the nature and extent of break-up related magmatism and c) the nature and width of the continent-ocean transition zone. Margin segmentation is directly linked to the location of major oceanic fracture zones as well as to the location and geometry of the major Palaeozoic to Mesozoic basins. Furthermore, the correlation between margin segmentation and structural trends of underlying Proterozoic Pinjarra Orogen suggests some basement control on margin evolution. The revised COB interpretation is combined with recent Indian Ocean plate reconstructions incorporating potential field data from the abyssal plains of west Australia and east Antarctica, including the Early Cretaceous southwest Australian margin. Comparisons between this model and recent basin scale sequence stratigraphic studies across the region provide new insights into Mesozoic basin evolution, including the relative timing of break-up within each basin. In addition, the model illustrates the possible impacts of Valanginian to Aptian transform margin development on the tectonic and thermal evolution of the northern Perth Basin depocentres.
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The 'River Murray Corridor (RMC) Salinity Mapping Project', provides important new information in relation to salinity hazard and management along in a 20 km-wide swath along a 450 km reach of the River Murray. The project area contains iconic wetlands, national and state forest parks, irrigation and dryland farming assets and the Murray River, significant areas of which are at risk from increasing salinisation of the River, the floodplain, and underlying groundwater resources. The project utilised a hydrogeological systems approach to integrate and analyse data obtained from a large regional airborne electromagnetic (AEM) survey (24,000 line km @ 150m line-spacing in a 20 km-wide swath along the Murray River), field mapping, and lithological and hydrogeochemical data obtained from drilling. New holistic inversions of the AEM data have been used to map key elements of the hydrogeological system and salinity extent in the shallow sub-surface (top 20-50 m). The Murray River is known to display great complexity in surface-groundwater interactions along its course. Electrical geophysical methods (such as AEM) are able to map surface-groundwater interaction due to the contrast between (electrically resistive) fresh water in the river, and (electrically conductive) brackish to saline groundwater in adjacent sediments. The location of significant river flush zones is influenced both by underlying geology and the location of locks, weirs and irrigation districts. The study has also identified significant areas of high salinity hazard in the floodplain and river, and quantified the salt store and salt load across the floodplain. The study has also identified sub-surface factors (including saline groundwater, shrinking flush zones, declining water tables) linked to vegetation health declines.
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Improving techniques for mapping land surface composition at regional- to continental-scale is the next step in delivering the benefits of remote sensing technology to Australia. New methodologies and collaborative efforts have been made as part of a multi-agency project to facilitate uptake of these techniques. Calibration of ASTER data with HyMAP has been very promising, and following an program in Queensland, a mosaic has been made for the Gawler-Curnamona region in South Australia. These programs, undertaken by Geoscience Australia, CSIRO, and state and industry partners, aims to refine and standardise processing and to make them easily integrated with other datasets in a GIS.
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Magnetotelluric (MT) data have been acquired in 2008 and 2009 at 40 broadband (0:01 s to 500 s) and 12 long-period (10 s to 10 000 s) sites along the east-west deep seismic reflection transect of northern Eyre Peninsula, South Australia. The MT survey is a joint project between the University of Adelaide and Geoscience Australia and is funded by the Australian Government as part of the Onshore Energy Security Program. Long-period sites are spaced 20 km apart and broadband sites infill this spacing to 10 km with also some 5 km spacing. This ensures sufficient coverage to map the upper crustal to upper mantle structures beneath northern Eyre Peninsula.
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Abstract for the Asia Oceania Geosciences Society (AOGS) conference on 24-28 June 2013.
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Volcanic ash represents a serious hazard to communities living in the vicinity of active volcanoes in developing countries like Indonesia. Geoscience Australia, the Australia-Indonesia Facility for Disaster Reduction (AIFDR) and the Indonesian Centre for Volcanology and Geohazard Mitigation (CVGHM) have adapted an existing open source volcanic ash dispersion model for use in Indonesia. The core model is the widely used volcanic ash dispersion model FALL3D. A python wrapper has been developed, which simplifies the use of FALL3D for those with little or no background in computational modelling. An application example is described here for Gunung Ciremai in West Java, Indonesia. Scenarios were run using eruptive parameters within the acceptable range of possible future events for this volcano, granulometry as determined through field studies and a meteorological dataset that represented a complete range of possible wind conditions expected during the dry and rainy seasons for the region. Implications for varying degrees of hazard associated with volcanic ash ground loading on nearby communities for dry versus rainy season wind conditions is discussed. Communities located on the western side of Gunung Ciremai are highly susceptible to volcanic ash ground loading regardless of the season whereas communities on the eastern side are found to be more susceptible during the rainy season months than during the dry. This is attributed to prevailing wind conditions during the rainy season that include a strong easterly component. These hazard maps can be used for hazard and impact analysis and can help focus mitigation efforts on communities most at risk.
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Global climate change is putting Australia's infrastructure and in particular coastal infrastructure at risk. More than 80% of Australians live within the coastal zone. Almost 800,000 residences are within 3km of the coast and less than 6m above sea level. Much of Australia's land transport is built around road and rail infrastructure which is within the threatened coastal zone. A significant number of Australia's ports, harbours and airports are under threat. Australia's coastal zone contains several major cities, and supports agriculture, fisheries, tourism, coastal wetlands and estuaries, mangroves and other coastal vegetation, coral reefs, heritage areas and threatened species or habitats. Sea level rise is one physical effect of rising sea temperatures and is estimated at about 0.146m for 2030 (IPCC 2007) and up to 1.1m for 2100 (Antarctic and Climate Ecosystems CRC). The warming is likely to result in increases in intensity of both extra-tropical and tropical storms (spatially dependent) which are predicted to increase storm surge and severe wind hazard. Beaches, estuaries, coastal wetlands, and reefs which have adapted naturally to past changes in climate (storminess) and sea level over long time scales, now are likely to face faster rates of change. In many cases landward migration may be blocked by human land uses and infrastructure. Adaptation options include integrated coastal zone assessments and management; redesign, rebuilding, or relocation of capital assets; protection of beaches, dunes and maritime infrastructure; development zone control; and retreat plans.