In March and April, 2012, Geoscience Australia undertook a seabed characterisation survey, aimed at supporting the assessment of CO2 storage potential of the Vlaming Sub-basin, Western Australia. The survey, undertaken as part of the National CO2 Infrastructure Plan program was targeted to provide an understanding of the link between the deep geological features of the area and the seabed, and connectivity between them as possible evidence for seal integrity. Data was acquired in two sections of the Rottnest Shelf lying above the regional seal - the South Perth Shale - and the underlying potentially CO2-suitable reservoir, the Gage Sandstone. Seabed samples were taken from 43 stations, and included 89 seabed grab samples. A total of 653 km2 of multibeam and backscatter data was obtained. Chirper shallow sub-bottom profile data was acquired concurrently. 6.65 km2 of side-scan sonar imagery was also obtained. The two surveyed areas, (Area 1 and Area 2), are set within a shallow sediment starved shelf setting. Area 2, situated to the southwest of Rottnest Island, is characterised by coralline red algal (rhodolith) beds, with ridges and mounds having significant rhodolith accumulations. The geomorphic expression of structural discontinuities outcropping at the seabed is evident by the presence of linear fault-like structures notable in Area 1, and north-south trending lineaments in Area 2. North-south trending structural lineaments on the outer section of Area 2 have in places, mounds standing 4-5 m above the seafloor in water depths of 80-85 m. Although there are apparent spatial correlations between seabed geomorphology and the structural geology of the basin, the precise relationship between ridges and mounds that are overlain by rhodolith accumulations, fluid seepage, and Vlaming Sub-basin geology is uncertain, and requires further work to elucidate any links.

The presence of abundant bedded sulfate deposits before 3.2 Ga and after 1.8 Ga, the peak in iron formation abundance between 3.2 and 1.8 Ga, and the aqueous geochemistry of sulfur and iron together suggest that the redox state, and the abundances of sulfur and iron in the hydrosphere varied widely during the Archean and Proterozoic. We propose a layered hyddrosphere prior to 3.2 Ga in which sulfate produced by atmospheric photolytic reactions was enriched in an upper layer, whereas the underlying layer was reduced and sulfur-poor. Between 3.2 and 2.4 Ga, biolotical and/or inorganic sulfate reduction reactions removed sulfate from the upper layer, producing broadly uniform, reduced, sulfur-poor and iron-rich oceans. As a result of increasing atmospheric oxygenation around 2.4 Ga, the flux of sulfate into the hydrosphere by oxidative weathering was greatly enhanced, producing layered oceans, with sulfate-rich, iron-poor surface waters and reduced, sulfur-poor and iron-rich bottom waters. This process continued so that by 1.8 Ga, the hydrosphere was generally oxidized, sulfate-rich and iron-poor throughout. Variations in sulfur and iron abundances suggest that the redox state of the oceans was buffered by iron before 2.4 Ga and by sulfur after 1.8 Ga.

In July 2010 Geoscience Australia and CSIRO Marine & Atmospheric Research jointly commissioned a new atmospheric composition monitoring station (' Arcturus') in central Queensland. The facility is designed as a proto-type remotely operated `baseline monitoring station' such as could be deployed in areas that are likely targets for commercial scale carbon capture and geological storage (CCS). It is envisaged that such a station could act as a high quality reference point for later in-fill, site based, atmospheric monitoring associated with geological storage of CO2. The station uses two wavelength scanned cavity ringdown instruments to measure concentrations of carbon dioxide (CO2), methane (CH4), water vapour and the isotopic signature (?13C) of CO2. Meteorological parameters such as wind speed and wind direction are also measured. In combination with CSIRO's TAPM (The Air Pollution Model), data will be used to understand the local variations in CO2 and CH4 and the contributions of natural and anthropogenic sources in the area to this variability. The site is located in a region that supports cropping, grazing, cattle feedlotting, coal mining and gas production activities, which may be associated with fluxes of CO2 and CH4. We present in this paper some of the challenges found during the installation and operation of the station in a remote, sub-tropical environment and how these were resolved. We will also present the first results from the site coupled with preliminary modelling of the relative contribution of large point source anthropogenic emissions and their contribution to the background.

Within the GEODISC program of the Australian Petroleum Cooperative Research Centre (APCRC), Geoscience Australia (GA) and the University of New South Wales (UNSW) completed an analysis of the potential for the geological storage of CO2. The geological analysis produced an assessment from over 100 potential Environmentally Sustainable Sites for CO2 Injection (ESSCI) by applying a deterministic risk assessment. Out of 100 potential sites, 65 proved to be valid sites for further study. This assessment examined predominantly saline reservoirs which is where we believe Australia?s greatest storage potential exists. However, many of these basins also contain coal seams that may be capable of storing CO2. Several of these coal basins occur close to coal-fired power plants and oil and gas fields where high levels of CO2 are emitted. CO2 storage in coal beds is intrinsically different to storage in saline formations, and different approaches need to be applied when assessing them. Whilst potentially having economic benefit, enhanced coal bed methane (ECBM) production through CO2 injection does raise an issue of how much greenhouse gas mitigation might occur. Even if only small percentages of the total methane are liberated to the atmosphere in the process, then a worse outcome could be achieved in terms of greenhouse gas mitigation. The most suitable coal basins in Australia for CO2 storage include the Galilee, Cooper and Bowen-Surat basins in Queensland, and the Sydney, Gunnedah, and Clarence-Moreton Basins in New South Wales. Brief examples of geological storage within saline aquifers and coal seams in the Bowen and Surat basins, Queensland Australia, are described in this paper to compare and contrast each storage option.

Geological Storage Potential of CO2 & Source to Sink Matching Matching of CO2 sources with CO2 storage opportunities (known as source to sink matching), requires identification of the optimal locations for both the emission source and storage site for CO2 emissions. The choice of optimal sites is a complex process and can not be solely based on the best technical site for storage, but requires a detailed assessment of source issues, transport links and integration with economic and environmental factors. Many assessments of storage capacity of CO2 in geological formations have been made at a regional or global level. The level of detail and assessment methods vary substantially, from detailed attempts to count the actual storage volume at a basinal or prospect level, to more simplistic and ?broad brush? approaches that try to estimate the potential worldwide (Bradshaw et al, 2003). At the worldwide level, estimates of the CO2 storage potential are often quoted as ?very large? with ranges for the estimates in the order of 100?s to 10,000?s Gt of CO2 (Beecy and Kuuskra, 2001; Bruant et al, 2002; Bradshaw et al 2003). Identifying a large global capacity to store CO2 is only a part of the solution to the CO2 storage problem. If the large storage capacity can not be accessed because it is too distant from the source, or is associated with large technical uncertainty, then it may not be possible to reliably predict that it would ever be of value when making assessments. To ascertain whether any potential storage capacity could ever be actually utilised requires analysis of numerous other factors. Within the GEODISC program of the Australian Petroleum Cooperative Research Centre (APCRC), Geoscience Australia (GA) and the University of New South Wales (UNSW) completed an analysis of the potential for the geological storage of CO2. Over 100 potential Environmentally Sustainable Sites for CO2 Injection (ESSCIs) were assessed by applying a deterministic risk assessment (Bradshaw et al, 2002). At a regional scale Australia has a risked capacity for CO2 storage potential in excess of 1600 years of current annual total net emissions. However, this estimate does not incorporate the various factors that are required in source to sink matching. If these factors are included, and an assumption is made that some economic imperative will apply to encourage geological storage of CO2, then a more realistic analysis can be derived. In such a case, Australia may have the potential to store a maximum of 25% of our total annual net emissions, or approximately 100 - 115 Mt CO2 per year.

The economics of the storage of CO2 in underground reservoirs in Australia have been analysed as part of the Australian Petroleum Cooperative Research Centre's GEODISC program. The analyses are based on cost estimates generated by a CO2 storage technical / economic model developed at the beginning of the GEODISC project. They also rely on data concerning the characteristics of geological reservoirs in Australia. The uncertainties involved in estimating the costs of such projects are discussed and the economics of storing CO2 for a range of CO2 sources and potential storage sites across Australia are presented. The key elements of the CO2 storage process and the methods involved in estimating the costs of CO2 storage are described and the CO2 storage costs for a hypothetical but representative storage project in Australia are derived. The effects of uncertainties inherent in estimating the costs of storing CO2 are shown. The analyses show that the costs are particularly sensitive to parameters such as the CO2 flow rate, the distance between the source and the storage site, the physical properties of the reservoir and the market prices of equipment and services. Therefore, variations in any one of these inputs can lead to significant variation in the costs of CO2 storage. Allowing for reasonable variations in all the inputs together in a Monte Carlo simulation of any particular site, then a large range of total CO2 storage costs is possible. The effect of uncertainty for the hypothetical representative storage site is illustrated. The impact of storing other gases together with CO2 is analysed. The other gases include methane, hydrogen sulphide, nitrogen, nitrous oxides and oxides of sulphur, all of which potentially could be captured together with CO2. The effect on storage costs when varying quantities of other gases are injected with the CO2 is shown. Based on the CO2 storage estimates and the published costs capturing CO2 from industrial processes, the econ

This geomechanical analysis of the Browse Basin was undertaken as part of the CO2CRC's Browse Basin Geosequestration Analysis. This study aims to constrain the geomechanical model (in situ stresses), and to evaluate the risk of fault reactivation. The stress regime in the Browse Basin is one of strike-slip faulting i.e. maximum horizontal stress (~ 28.3 MPa/km) > vertical stress (22 MPa/km) > minimum horizontal stress (15.7 MPa/km). Pore pressure is near hydrostatic in all wells except for two, which exhibit elevated pore fluid pressures at depths greater than 3500 m. A maximum horizontal stress orientation of 095' was considered to be most appropriate for the Barcoo sub-basin, which was the area of focus in this study. The risk of fault reactivation was calculated using the FAST (Fault Analysis Seal Technology) technique, which determines fault reactivation risk by estimating the increase in pore pressure required to cause reactivation. Fault reactivation risk was calculated using two fault strength scenarios; cohesionless faults (C = 0; ? = 0.6) and healed faults (C = 5; ? = 0.75). The orientations of faults with high and low reactivation risks is almost identical for healed and cohesionless faults. High angle faults striking N-S are unlikely to reactivate in the current stress regime. High angle faults orientated ENE-WSW and ESE-WNW have the highest fault reactivation risk. Due to the fact that the SH gradient was determined using frictional limits, the most unfavourably oriented cohesionless faults cannot sustain any pore pressure increase without reactivating. By contrast, using a cohesive fault model indicates that those same faults would be able to sustain a pore pressure increase (Delta P) of 9.6 MPa. However, it must be emphasized that the absolute values of Delta P presented in this study are subject to large errors due to uncertainties in the geomechanical model, in particular for the maximum horizontal stress. Therefore, the absolute values of Delta-P presented herein should not be used for planning purposes. Fault reactivation risk was evaluated for 10 faults with known orientations. All faults were interpreted as extending from below the Jurassic target reservoir formation to the surface. The dominant fault in the Barcoo sub-basin is the large fault which extends from Trochus 1 to Sheherazade 1 to Arquebus 1. This deeply penetrating, listric fault initially formed as a normal fault and was subsequently reactivated in thrust mode. Most of the faults in the Barcoo sub-basin trend broadly N-S and are therefore relatively stable with respect to increases in pore pressure. However, there are sections within some individual faults where fault orientation becomes close to optimal. In these sections, small increases in pore pressure (<5 MPa) may be sufficient to cause fault reactivation. If this were to occur, then significant risk of CO2 leakage would exist, as these sections cross-cut the regional seal.

A Bayesian inversion technique to determine the location and strength of trace gas emissions from a point source in open air is presented. It was tested using atmospheric measurements of nitrous oxide (N2O) and carbon dioxide (CO2) released at known rates from a source located within an array of eight evenly spaced sampling points on a 20 m radius circle. The analysis requires knowledge of concentration enhancement downwind of the source and the normalized, three-dimensional distribution (shape) of concentration in the dispersion plume. The influence of varying background concentrations of ~1% for N2O and ~10% for CO2 was removed by subtracting upwind concentrations from those downwind of the source to yield only concentration enhancements. Continuous measurements of turbulent wind and temperature statistics were used to model the dispersion plume. The analysis localized the source to within 0.8 m of the true position and the emission rates were determined to better than 3% accuracy. This technique will be useful in assurance monitoring for geological storage of CO2 and for applications requiring knowledge of the location and rate of fugitive emissions.

This paper briefly summaries how intrinsic uncertainties in reservoir characterization, at the proposed Otway Basin Naylor Field carbon-dioxide geo-sequestration site, were risk managed by a process of creation and evaluation of a series of geo-models (term to describe the geo-cellular geological models created by PETREL software) that cover the range of plausible geological possibilities, as well as extreme case scenarios. Optimization methods were employed, to minimize simulation run time, whilst not compromising the essential features of the basic geo-model. For four different Cases, 7 geo-models of the reservoir were created for simulation studies. The reservoir simulation study relies primarily on production history matching and makes use of all available information to help screen and assess the various geo-models. The results suggest that the bulk reservoir permeability is between 0.5 - 1Darcy, the original gas-water-contact was about 2020 mSS and there is a strong aquifer drive.

Identification of major hydrocarbon provinces from existing world assessments for hydrocarbon potential can be used to identify those sedimentary basins at a global level that will be highly prospective for CO2 storage. Most sedimentary basins which are minor petroleum provinces and many non-petroliferous sedimentary basins will also be prospective for CO2 storage. Accurate storage potential estimates will require that each basin be assessed individually, but many of the prospective basins may have ranges from high to low prospectivity. The degree to which geological storage of CO2 will be implemented in the future will depend on the geographical and technical relationships between emission sites and storage locations, and the economic drivers that affect the implementation for each source to sink match. CO2 storage potential is a naturally occurring resource, and like any other natural resource there will be a need to provide regional access to the better sites if the full potential of the technology is to be realized. Whilst some regions of the world have a paucity of opportunities in their immediate geographic confines, others are well endowed. Some areas whilst having good storage potential in their local region may be challenged by the enormous volume of CO2 emissions that are locally generated. Hubs which centralize the collection and transport of CO2 in a region could encourage the building of longer and larger pipelines to larger and technically more viable storage sites and so reduce costs due to economies of scale.