Total contribution of six recently discovered submerged coral reefs in northern Australia to Holocene neritic CaCO3, CO2, and C is assessed to address a gap in global budgets. CaCO3 production for the reef framework and inter-reefal deposits is 0.26-0.28 Mt which yields 2.36-2.72 x105 mol yr-1 over the mid- to late-Holocene (<10.5 kyr BP); the period in which the reefs have been active. Holocene CO2 and C production is 0.14-0.16 Mt and 0.06-0.07 Mt, yielding 3.23-3.71 and 5.32-6.12 x105 mol yr-1, respectively. Coral and coralline algae are the dominant sources of Holocene CaCO3 although foraminifers and molluscs are the dominant constituents of inter-reefal deposits. The total amount of Holocene neritic CaCO3 produced by the six submerged coral reefs is several orders of magnitude smaller than that calculated using accepted CaCO3 production values because of very low production, a 'give-up' growth history, and presumed significant dissolution and exports. Total global contribution of submerged reefs to Holocene neritic CaCO3 is estimated to be 0.26-0.62 Gt or 2.55-6.17 x108 mol yr-1, which yields 0.15-0.37 Gt CO2 (3.48-8.42 x108 mol yr-1) and 0.07-0.17 Gt C (5.74-13.99 x108 mol yr-1). Contributions from submerged coral reefs in Australia are estimated to be 0.05 Gt CaCO3 (0.48 x108 mol yr-1), 0.03 Gt CO2 (0.65 x108 mol yr-1), and 0.01 Gt C (1.08 x108 mol yr-1) for an emergent reef area of 47.9 x103 km2. The dilemma remains that the global area and CaCO3 mass of submerged coral reefs are currently unknown. It is inevitable that many more submerged coral reefs will be found. Our findings imply that submerged coral reefs are a small but fundamental source of Holocene neritic CaCO3, CO2, and C that is poorly-quantified for global budgets.

In mid 2011 the Australian Government announced funding of a new four year National CO2 Infrastructure Plan (NCIP) to accelerate the identification and development of sites suitable for the long term storage of CO2 in Australia that are within reasonable distances of major energy and industrial CO2 emission sources. The NCIP program promotes pre-competitive storage exploration and provides a basis for the development of transport and storage infrastructure. The Plan follows on from recommendations from the Carbon Storage Taskforce and the National CCS Council (formerly, the National Low Emissions Coal Council). It builds on the work funded under the National Low Emissions Coal Initiative and the need for adequate storage to be identified as a national priority. Geoscience Australia is providing strategic advice in delivering the plan and will lead in the acquisition of pre-competitive data. Four offshore sedimentary basins (Bonaparte, Browse, Perth and Gippsland basins) and several onshore basins have been identified for pre-competitive data acquisition and study. The offshore Petrel Sub-basin is located in Bonaparte Basin, in NW Australia, has been identified as a potential carbon storage hub for CO2 produced as a by-product from future LNG processing associated with the development of major gas accumulations on the NW Shelf. The aim of the project is to determine if the sub-basin is suitable for long-term storage, and has the potential capacity to be a major storage site. The project began in June 2011 and will be completed by July 2013. As part of the project, new 2D seismic data will be acquired in an area of poor existing seismic coverage along the boundary of the two Greenhouse Gas Assessment Areas, which were released in 2009.

The Australian Government, through the Department of Resources, Energy and Tourism, has supported Geoscience Australia in undertaking a series of regional-scale, geological studies to assess the CO2 storage potential of sedimentary basins, including the Petrel Sub-basin. The studies form part of the National Low Emissions Coal Initiative designed to accelerate the development of CO2 transport and storage infrastructure near the sources of major energy and industrial emissions. The Petrel Sub-basin was identified as a high-priority region for a future pre-competitive work program by the national Carbon Storage Taskforce. The Carbon Storage Taskforce also recommended the release of greenhouse gas assessment permits, which were released within the Petrel Sub-basin in 2009. As a component of the studies at Geoscience Australia, the numerical simulation was hypothetically designed to dynamically model the reservoir behavior and CO2 migration during the injection and post-injection stages using an in-house built 3D geological model of a represented injection site. 14 million tonnes per annum (MTPA) of CO2 was injected into the lower Frigate/Elang/Plover reservoir over 30 years and CO2 plume migration was simulated up to 2,000 years from the initial injection. The injection rate of 14 MTPA of CO2 used in this study was based on the predicted 2020 CO2 emissions of the Darwin Hub, a figure defined by the Carbon Storage Taskforce (2009). The poster highlights the simulation results including CO2 plume migration distance, CO2 trapping mechanisms and reservoir pressure behavior.

The CO2CRC Otway Project in southwestern Victoria, Australia has injected over 17 months 65 445 tonnes of a mixed carbon dioxide-methane fluid into the water leg of a depleted natural gas reservoir at a depth of approximately 2km. Pressurized sub-surface fluids were collected from the Naylor-1 observation well using a tri-level U-tube sampling system located near the crest of the fault-bounded anticline trap, 300 metres up-dip of the CRC-1 gas injection well. Relative to the pre-injection gas-water contact (GWC), only the shallowest U-tube initially accessed the residual methane gas cap. The pre-injection gas cap at Naylor-1 contains CO₂ at 1.5 mol% compared to 75.4 mol% for the injected gas from the Buttress-1 supply well and its CO₂ is depleted in ¹³C by 4.5%₀ VPDB compared to the injected supercritical CO<Sub>2</sub>. Additional assurance of the arrival of injected gas at the observation well is provided by the use of the added tracer compounds, CD₄, Kr and SF₆ in the injected gas stream. Lessons learnt from the CO2CRC Otway Project have enabled us to better anticipate the challenges for rapid deployment of carbon dioxide in a commercial environment at much larger scales.

Multibeam sonar mapping, drill cores and underwater video data have confirmed the existence of a previously unknown reef province in the Gulf of Carpentaria, Australia. Seven reefs, comprised of coral limestone that support living corals have been mapped so far and as many as 50 other reefs may exist in the region. U/Th ages show that reef growth commenced shortly after limestone pedestals were submerged by rising sea level around 10.5 kyr BP, making them the oldest reefs known in Australia. Reef growth persisted for ~2.0 kyr but it had ceased at most locations by ~8.0 kyr BP. Measurements of reef growth rates (0.95 to 4 m kyr-1), indicate that the reefs were unable to keep pace with contemporaneous rapid sea level rise (>10 m kyr-1), which is consistent with a 'give up' reef growth history. Core samples from reef platforms demonstrate that Pleistocene limestone is exposed in depths of 27 and 30 m below present mean sea level. These depths represent regionally significant phases of reef growth during a prolonged sea level still stand. We conclude that the reefs are therefore mostly relict features, whose major phase of growth and development relates to an earlier, pre-Holocene sea level stillstand.

Between March 2008 and August 2009, 65,445 tonnes of ~75 mol% CO2 gas were injected in a depleted natural gas reservoir approximately 2000 m below surface at the Otway project site in Victoria, Australia. Groundwater flow and composition were monitored biannually in 2 near-surface aquifers between June 2006 and March 2011, spanning the pre-, syn- and post-injection periods. The shallow (~0-100 m), unconfined, porous and karstic aquifer of the Port Campbell Limestone and the deeper (~600-900 m), confined and porous aquifer of the Dilwyn Formation contain valuable fresh water resources. Groundwater levels in either aquifer have not been affected by the drilling, pumping and injection activities that were taking place, or by the rainfall increase observed during the project. In terms of groundwater composition, the Port Campbell Limestone groundwater is fresh (electrical conductivity = 801-3900 ?S/cm), cool (temperature = 12.9-22.5 C), and near-neutral (pH 6.62-7.45), whilst the Dilwyn Formation groundwater is fresher (electrical conductivity 505-1473 ?S/cm), warmer (temperature = 42.5-48.5 C), and more alkaline (pH 7.43-9.35). Evapotranspiration and carbonate dissolution control the composition of the groundwaters. Comparing the chemical and isotopic composition of the groundwaters collected before, during and after injection shows either no sign of statistically significant changes or, where they are statistically significant, changes that are generally opposite those expected if CO2 addition had taken place. The monitoring program demonstrates that the physical and chemical properties of the groundwaters at the sampled bores have not been affected by CO2 sequestration.

High-CO2 gas fields serve as important analogues for understanding various processes related to CO2 injection and storage. The chemical signatures, both within the fluids and the solid phases, are especially useful for elucidating preferred gas migration pathways and also for assessing the relative importance of mineral dissolution and/or solution trapping efficiency. In this paper, we present a high resolution study focused on the Gorgon gas field and associated Rankin trend gases on Australia's Northwest Shelf of Australia. The gas data we present here display correlate-able trends for mole %-CO2 and %- C CO2 both areally and vertically. Generally, CO2 mol % decreases and becomes depleted in %- C (lighter) upsection and towards the north; a trend which also holds true for the greater Rankin trend gases in general. The strong spatial variation of CO2 content and %- C and the interrelationship between the two suggests that processes were active to alter the two in tandem. We propose that these variations were driven by the precipitation of a carbonate phase, namely siderite, which is observed as a common late stage mineral. This conclusion is based on Rayleigh distillation modeling together with bulk rock isotopic analyses of core, which confirms that CO2 in gases are genetically related to the late stage carbonate cements. The results from this study have important implications for carbon storage operations and suggest that significant CO2 may be reacted out a gas plume over short migration distances.

Atmospheric tomography is a monitoring technique that uses an array of sampling sites and a Bayesian inversion technique to simultaneously solve for the location and magnitude of a gaseous emission. Application of the technique to date has relied on air samples being pumped over short distances to a high precision FTIR Spectrometer, which is impractical at larger scales. We have deployed a network of cheaper, less precise sensors during three recent large scale controlled CO2 release experiments; one at the CO2CRC Ginninderra site, one at the CO2CRC Otway Site and another at the Australian Grains Free Air CO2 Enrichment (AGFACE) facility in Horsham, Victoria. The purpose of these deployments was to assess whether an array of independently powered, less precise, less accurate sensors could collect data of sufficient quality to enable application of the atmospheric tomography technique. With careful data manipulation a signal suitable for an inversion study can be seen. A signal processing workflow based on results obtained from the atmospheric array deployed at the CO2CRC Otway experiment is presented.

Regional geological properties of sedimentary basins play a significant role in determining the safety of CO2 storage. Four major trapping mechanism have been identified: Structural and stratigraphic trapping is the containment of supercritical CO2 by low permeability / low porosity rocks and is the dominant mechanism during injection and initial storage phase. Residual or capillary trapping is the retention of supercritical CO2 in the pore space between grains and tends to be most relevant on a scale of tens to thousands of years. Solubility trapping is the uptake of CO2 into the formation water, which is considered to be the most important trapping mechanism over hundreds to millions of years (1). Mineral trapping leads to the permanent immobilization of carbon through the precipitation of carbonate minerals. This study assesses the conditions for solubility trapping in major Australian sedimentary basins. The total dissolved solid (TDS) concentration of the formation water has been compiled from over 900 wells as it, along with pressure and temperature, is a key variable controlling CO2 solubility and the associated change in fluid density. Fluid density is a critical factor in driving fluid advection which determines the rate of solubility trapping and downward migration in the formation. This process is vital in reducing the amount of highly mobile supercritical CO2 at the top of the formation and storing it as dissolved CO2 in deeper parts of the formation.

Geological storage of CO₂ requires fundamental knowledge and predictive capabilities on the transport and reactions of injected CO₂ and associated gases to assess the short and long term consequences. CO₂ can be stored in the subsurface through various mechanisms including structural trapping, solubility trapping and by precipitation of carbonate minerals. While mineral strapping is considered to be the safest storage mechanism as it permanently immobilizes the CO₂, the reaction rates and the likely importance for geosequestration is poorly understood. This project has five objectives, which aim to make CO₂ storage more predictable and safer. A range of approaches will be used including desk top studies, laboratory and field experiments and geochemical modelling.