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 geomechanical assessment of the Naylor Field, Otway Basin has been undertaken by the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) to investigate the possible geomechanical effects of CO2 injection and storage. The study aims to: - further constrain the geomechanical model (in-situ stresses and rock strength data) developed by van Ruth and Rogers (2006), and; - evaluate the risk of fault reactivation and failure of intact rock. The stress regime in the onshore Victorian Otway Basin is: - strike-slip if maximum horizontal stress is calculated using frictional limits, and; - normal if maximum horizontal stress is calculated using the CRC-1 leak-off test. The NW-SE maximum horizontal stress orientation (142ºN) determined from a resistivity image log of the CRC-1 borehole is broadly consistent with previous estimates and verifies a NW-SE maximum horizontal stress orientation in the Otway Basin. The estimated maximum pore pressure increase (Delta-P) which can be sustained within the target reservoir (Waarre Formation Unit C) without brittle deformation (i.e. the formation of a fracture) was estimated to be 10.9 MPa using maximum horizontal stress determined by frictional limits and 14.5 MPa using maximum horizontal stress determined using CRC-1 extended leak-off test data. The maximum pore pressure increase which can be sustained in the seal (Belfast Mudstone) was estimated to be 6.3 MPa using maximum horizontal stress determined by frictional limits and 9.8 MPa using maximum horizontal stress determined using CRC-1 extended leak-off test data. The propensity for fault reactivation was calculated using the FAST (Fault Analysis Seal Technology) technique, which determines fault reactivation propensity by estimating the increase in pore pressure required to cause reactivation (Mildren et al., 2002). Fault reactivation propensity was calculated using two fault strength scenarios; cohesionless faults (C = 0; ? = 0.60) and healed faults (C = 5.4; ?= 0.78). The orientations of faults with high and low reactivation propensity are similar for healed and cohesionless faults. In addition, two methods of determining maximum horizontal stress were used; frictional limits and the CRC-1 extended leak-off test. Fault reactivation analyses differ as a result in terms of which fault orientations have high or low fault reactivation propensity. Fault reactivation propensity was evaluated for three key faults within the Naylor structure with known orientations. The fault segment with highest fault reactivation propensity in the Naylor Field is on the Naylor South Fault near the crest of the Naylor South sub-structure. Therefore, leakage of hydrocarbons from the greater Naylor structure may have occurred through past reactivation of the Naylor South Fault, thus accounting for the pre-production palaeo-column in the Naylor field. The highest reactivation propensity (for optimally-orientated faults) ranges from an estimated pore pressure increase (Delta-P) of 0.0 MPa to 28.6 MPa depending on assumptions made about maximum horizontal stress magnitude and fault strength. Nonetheless, the absolute values of Delta-P presented in this study are subject to large errors due to uncertainties in the geomechanical model. In particular, the maximum horizontal stress and rock strength are poorly constrained.

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.

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 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.

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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?

Questions often asked by the public in regard to the concept of CO2 storage include; "But won?t it leak?", and "How long will it stay down there?". The natural environment of petroleum systems documents many of the processes which will influence CO2 storage outcomes, and the likely long (geological) timeframes that will operate. Thousand of billions of barrels of hydrocarbons have been trapped and stored in geological formations in sedimentary basins for 10s to 100s of millions of years, as has substantial volumes of CO2 that has been generated through natural processes. Examples from Australia and major hydrocarbon provinces of the world are documented, including those basins with major accumulations that are currently trapped in their primary reservoir, those that have accumulated hydrocarbons in the primary reservoir and then through tectonic activity spilled them to other secondary traps or released the hydrocarbons to the atmosphere, and those that generated hydrocarbons but for which no effective traps were in place for hydrocarbons to accumulate. Some theoretical modelling of the likelihood of meeting stabilisation targets using geological storage are based on leakage rates which are implausibly high when compared to observations from viable storage locations in the natural environment, and do not necessarily account for the likelihood of delay times for leakage to the atmosphere or the timeframe in which geological events will occur. Without appropriate caveats, they potentially place at risk the public perception of how efficient and effective appropriately selected geological reservoirs could be for storage of CO2. If the same rigorous methods, technology and skills that are used to explore for, find and produce hydrocarbon accumulations are now used for finding safe and secure storage sites for CO2, the traps so identified can be expected to contain the CO2 after injection for similar periods of time as that in which hydrocarbons and CO2 have been stored in the natural environment.