A question and answer style brochure on geological storage of carbon dioxide. Questions addressed include: - What is geological storage? - Why do we need to store carbon dioxide? - How can you store anything in solid rock? - Could the carbon dioxide contaminate the fresh water supply? - Could a hydrocarbon seal leak? - Are there any geological storage projects in Australia?

Australia has been making major progress towards early deployment of carbon capture and storage from natural gas processing and power generation sources. This paper will review, from the perspective of a government agency, the current state of various Australian initiatives and the advances in technical knowledge up until the 2010 GHGT conference. In November 2008, the Offshore Petroleum and Greenhouse Gas Storage Bill 2006 was passed by the Australian Parliament and established a legal framework to allow interested parties to explore for and evaluate storage potential in offshore sedimentary basins that lie in Australian Commonwealth waters. As a result of this Act, Australia became the first country in the world, in March 2009, to open exploration acreage for storage of greenhouse gases under a system that closely mirrors the well-established Offshore Petroleum Acreage Release. The ten offshore areas offered for geological storage assessment are significantly larger than their offshore petroleum counterparts to account for, and fully contain, the expected migration pathways of the injected GHG substances. The co-incidence of the 2009 Global Financial Crisis may have reduced the number of prospective CCS projects that were reported to be in the 'pipe-line' and the paper examines the implications of this apparent outcome. The Carbon Storage Taskforce has brought together both Australian governments technical experts to build a detailed assessment of the perceived storage potential of Australia's sedimentary basins. This evaluation has been based on existing data, both on and offshore. A pre-competitive exploration programme has also been compiled to address the identified data gaps and to acquire, with state funding, critical geological data which will be made freely available to encourage industrial participation in the search for commercial storage sites.

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

The middle to lower Jurassic sequence in Australia's Surat Basin has been identified as a potential reservoir system for geological CO2 storage. The sequence comprises three major formations with distinctly different mineral compositions, and generally low salinity formation water (TDS<3000 mg/L). Differing geochemical responses between the formations are expected during geological CO2 storage. However, given the prevailing use of saline reservoirs in CCS projects elsewhere, limited data are available on CO2-water-rock dynamics during CO2 storage in such low-salinity formations. Here, a combined batch experiment and numerical modelling approach is used to characterise reaction pathways and to identify geochemical tracers of CO2 migration in the low-salinity Jurassic sandstone units. Reservoir system mineralogy was characterized for 66 core samples from stratigraphic well GSQ Chinchilla 4, and six representative samples were reacted with synthetic formation water and high-purity CO2 for up to 27 days at a range of pressures. Low formation water salinity, temperature, and mineralization yield high solubility trapping capacity (1.18 mol/L at 45°C, 100 bar), while the paucity of divalent cations in groundwater and the silicate reservoir matrix results in very low mineral trapping capacity under storage conditions. Formation water alkalinity buffers pH at elevated CO2 pressures and exerts control on mineral dissolution rates. Non-radiogenic, regional groundwater-like 87Sr/86Sr values (0.7048-0.7066) indicate carbonate and authigenic clay dissolution as the primary reaction pathways regulating solution composition, with limited dissolution of the clastic matrix during the incubations. Several geochemical tracers are mobilised in concentrations greater than found in regional groundwater, most notably cobalt, concentrations of which are significantly elevated regardless of CO2 pressure or sample mineralogy.

The GEODISC Geographic Information System (GIS) Overview and Demonstration With the understanding that "better information leads to better decisions", Geoscience Australia has produced a Geographic Information System (GIS) that showcases the research completed within Projects 1, 2, and 8 of the GEODISC Program (Geological CO2 storage program in the Australian Petroleum Cooperative Research Centre, 1999-2003). The GIS is an interactive archive of Australia-wide regional analysis of CO2 sources and storage potential, incorporating economic modelling (Projects 1 and 8), as well as four site specific studies of the Dongara Gas field, Carnarvon Basin, Petrel Sub-basin and Gippsland Basin (Project 2). One of the major objectives of a collaborative research program such as GEODISC is to share results and knowledge with clients and fellow researchers, as well as to be able to rapidly access and utilise the research in future technical and policy decisions. With this in mind, the GIS is designed as a complete product, with a user-friendly interface developed with mainstream software to maximise accessibility to stakeholders. It combines tabular results, reports, models, maps, and images from various geoscientific disciplines involved in the geological modelling of the GEODISC site specific studies (ie geochemistry, geomechanics, reservoir simulations, stratigraphy, and geophysics) into one media. The GEODISC GIS is not just an automated display system, but a tool used to query, analyse, and map data in support of the decision making process. It allows the user to overlay different themes and facilitates cross-correlation between many spatially-related data sources. There is a vast difference between seeing data in a table of rows and columns and seeing it presented in the form of a map. For example, tabular results such as salinity data, temperature information and pressure tests, have been displayed as point data linked to well locations. These, in turn, have been superimposed on geophysical maps and images, to enable a better understanding of spatial relationships between features of a potential CO2 injection site. The display of such information allows the instant visualisation of complex concepts associated with site characterisation. In addition, the GEODISC GIS provides a tool for users to interrogate data and perform basic modelling functions. Economic modelling results have been incorporated into the regional study so that simple calculations of source to sink matching can be investigated. The user is also able to design unique views to meet individual needs. Digital and hardcopy map products can then be created on demand, centred on any location, at any scale, and showing selected information symbolised effectively to highlight specific characteristics. A demonstration of the GIS product will illustrate all of these capabilities as well as give examples of how site selection for CO2 sources and storage locations might be made.

Covering an area of approximately 247 000km2, the Galilee Basin is a significant feature of central Queensland. Three main depocentres contain several hundred metres of Late Carboniferous to Middle Triassic sediments. Sedimentation in the Galilee Basin was dominated by fluvial to lacustrine depositional systems. This resulted in a sequence of sandstones, mudstones, siltstones, coals and minor tuff in what was a relatively shallow intracratonic basin with little topographic relief. Forty years or more of exploration in the Galilee Basin has failed to discover any economic accumulations of hydrocarbons, despite the presence of apparently fair to very good reservoirs and seals in both the Permian and Triassic sequence. Despite some relatively large distances (upwards of 500km) between sources and sinks, previous and ongoing work on the Galilee Basin suggests that it has potential to sequester a significant amount of Queensland's carbon dioxide emissions. Potential reservoirs include the Early Permian Aramac Coal Measures, the Late Permian Colinlea Sandstone and the Middle Triassic Clematis Sandstone. These are sealed by several intraformational and local seals as well as the regional Triassic Moolayember Formation. With few suitable structural traps and little faulting throughout the Galilee sequence, residual trapping within saline reservoir is the most likely mechanism for storing CO2. The current study is aimed at building a sound geological model of the basin through activities such as detailed mapping, well correlation, and reservoir and seal analysis leading to reservoir simulations to gain a better understanding of the basin.

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.

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.

Between 2009 and 2012, Australia and China successfully completed the first phase of a bilateral project that aimed to build capacity in the area of geological storage of carbon dioxide among Chinese researchers, students, policy makers and professionals from academia, government and industry. This paper details the activities and results of the International CCS CAGS project, Phase I.