Groundwater has been sampled from 21 shallow (Port Campbell Limestone) and 3 deep (Dilwyn Formation) groundwater bores within a radius of 10 km around well CRC-1 between June 2006 and March 2008. The objectives of the study are (1) to establish baseline aquifer conditions prior to CO2 injection at CRC-1, which started in April 2008, and (2) to enable detection monitoring for CO2 leakage, should any occur in the future. In addition to sampling, standing water levels have been monitored continuously in 6 of the bores using barometric loggers. The water samples were analysed for pH, electrical conductivity (EC), temperature (T), dissolved oxygen (DO), redox potential (Eh), reduced iron (Fe2+) and alkalinity (dissolved inorganic carbon, DIC, as HCO3-) in the field, and for a suite of major, minor and trace inorganic species in the laboratory. Stable isotopes of O and H in water, of S in sulfate and of C and O in DIC were also determined. The shallow groundwaters have compositions typical of carbonate aquifer hosted waters, being fresh (EC 800-4000 uS/cm), dominated by Ca, Na, HCO3- and Cl-, cool (T 12-23°C), and near-neutral (pH 6.6-7.5). Most deep groundwater samples are similarly fresh or fresher (EC 400-1600 uS/cm), also dominated by Ca, Na, HCO3- and Cl-, cool (T 15-21°C), but are more alkaline (pH 7.5-9.5). Time-series reveal that parameters measured have been relatively stable over the sampling period, although some shallow bores display increasing EC and T, some show decreasing then increasing alkalinity while others show steadily increasing alkalinity (with or without increasing Cl- and Na, and decreasing Ca). Alkalinity of the deep groundwater tends to decrease slightly over the period. Groundwater levels in some of the shallow bores show a seasonal variation with longer term trends evident in both aquifers.

The Browse Basin is located in the southern Timor Sea region of Australia's North West Shelf and covers an area of ~140,000 km2. It was identified as containing potential Environmentally Suitable Sites for carbon dioxide (CO2) Injection (ESSCI) by the Australian Petroleum CRC's GEODISC program (1999-2003). A regional geological reconnaissance of Cenozoic sandstone and carbonate sequences in the Browse Basin was undertaken in 2007 to determine the potential storage and sealing capacity for geological storage of CO2, the results of which are presented in this report. Methods included the review of available literature and well-completion reports, lithological and mineral analysis of selected well cuttings and interpretation of the wire-line and seismic response of the Cenozoic section.

A geomechanical assessment of the Naylor Field, Otway Basin, Australia has been undertaken to investigate the possible geomechanical effects of CO2 injection and storage. The study aims to evaluate the geomechanical behaviour of the caprock/reservoir system and to estimate the risk of fault reactivation. The stress regime in the onshore Victorian Otway Basin is inferred to be strike-slip if the maximum horizontal stress is calculated using frictional limits and DITF (drilling induced tensile fracture) occurrence, or normal if maximum horizontal stress is based on analysis of dipole sonic log data. The NW-SE maximum horizontal stress orientation (142 degrees N) determined from a resistivity image log is broadly consistent with previous estimates and confirms a NW-SE maximum horizontal stress orientation for the Otway Basin. An analytical geomechanical solution is used to describe stress changes in the subsurface of the Naylor Field. The computed reservoir stress path for the Naylor Field is then incorporated into fault reactivation analysis to estimate the minimum pore pressure increase required to cause fault reactivation (Pp) The highest reactivation propensity (for critically-oriented faults) ranges from an estimated pore pressure increase (Pp) of 1MPa to 15.7MPa (estimated pore pressure of 18.5-233. MPa) depending on assumptions made about maximum horizontal stress magnitude, fault strength,reservoir stress path and Biot's coefficient. The critical pore pressure changes for known faults at Naylor Field range from an estimated pore pressure increase (Pp) of 2MPa to 17MPa (estimated pore pressure of 19.5-34.5 MPa).

This series of cross sections and data show the suitablility of the Sydney Basin for storage of carbon dioxide.Cartography file number 07-1825-1.

The Atmospheric Tomography software is a command line tool written in python to estimate the emission rate of a point source from concentration data. It implements an extension of the Bayesian inversion method. Bhatia, S., Feitz, A. and Francis, A. (2017) Atmospheric Tomography, GitHub repository, https://github.com/GeoscienceAustralia/atmospheric_tomography_laser

The Australian Government is developing enabling legislation that will underpin the development of safe and secure geological storage of greenhouse gases in Australia's offshore waters. The proposed legislation will facilitate the release of acreage for the identification and use of geological storage formations by industry proponents. A current proposal is that the release of the areas will be modelled on Australia's current system for the release of offshore petroleum acreage. This paper addresses the technical, policy, social, commercial, regulatory and economic issues to be considered in selecting areas to be released for geological storage in Australian offshore areas. Prospectivity for geological storage formations is the primary criterion for selection, and release areas will typically be defined on the basis of regional assessments. The paper briefly reviews the GEODISC program and its outcomes, and discusses the availability and limitations of other geological data used to support site selection. Regional examples of possible migration paths will be considered, and their impact on area boundaries, in conjunction with the licensing requirements of the proposed legislation. Source-sink matching is addressed, together with a discussion on the potential interactions with petroleum resources. Please Note: As at the submission date for abstracts, policy for geological storage in areas under the jurisdiction of the Australian Government is awaiting endorsement by the current Government. At this time, the abstract can therefore only consider issues relating to exploration acreage release in a universal manner, rather than specifically. If enabling legislation is passed, more specific examples of acreage selection may be provided, together with details of the legislative and regulatory constraints. The content of the paper is therefore dependent on the status of the legislation and release process at the time the paper is submitted.

Sampling, prior to CO2 injection at the CO2CRC Otway Project, southeastern Victoria at the end of 2007 early 2008, provided a stocktake of the molecular and isotopic (carbon and hydrogen) compositions of the subsurface hydrocarbon and non-hydrocarbon gases (and heavier hydrocarbons) at, and in close proximity to, the injection site. This baseline study is also fundamental to the assessment of present sub-surface petroleum components as natural tracers for injected gases arriving at the monitoring well. The CO2CRC Otway Project will use the CO2-rich natural gas (containing 79% CO2 and 20% methane) from the Buttress-1 well; totalling 100,000 tons of gas injected over 2 years. This gas mixture will be injected supercritically into sandstones of the CRC-1 well below the original gas-water contact at ~2000 m in the Waarre Formation. The depleted natural gas well at Naylor-1 is the monitoring well, situated 300 m updip of the injection well. Gas from the Waarre Formation in Naylor-1 observation well contains <1% CO2, which is isotopically depleted in 13C (13C -15.8) by 9 compared to CO2 (13C -6.8) in Buttress-1. Thus the carbon isotopes of CO2 can act as a primary natural tracer for monitoring purposes. Isotopically, the minimum detection limit would result from an increase of ~20 % in the CO2 concentration at Naylor-1 from the Buttress-derived CO2. On the other hand, the carbon and hydrogen isotopes of methane, wet gases and higher hydrocarbons are very similar between Buttress-1, CRC-1 and Naylor-1, requiring addition of external conservative tracers (Boreham et al., 2007) for the monitoring of hydrocarbon components. Although the content of liquid hydrocarbons in the gases is very low (<1%), there is the potential for supercritical CO2 extraction of these high molecular weight components (e.g. black oil in the Caroline-1 CO2 gas field and solid wax at the Boggy Creek CO2 production plant) that can be either advantageous (lubrication) or detrimental (clogging) to monitoring equipment at Naylor-1. The CRC-1 well provided an opportunity to collect downhole mud gases over many formations. Maximum total hydrocarbon concentration of 0.97 % occurred in the Waarre Formation Unit C. Surprisingly, a free gas zone in the overlying Flaxmans Formation had a lower maximum concentration (0.17 %). Carbon isotopes for the hydrocarbon gases from 1907 to 2249 mRT showed little downhole variation, while the 13C CO2 averaged -16, identical to CO2 at Naylor-1. Interestingly, the condensate recovered from a MDT in the Flaxmans Formation showed depletions in 13C for the C11 to C20 n-alkanes of up to 6 for n-C15 compared to n-alkanes of oils and condensates sourced from the Eumeralla Formation of the eastern Otway Basin (Boreham et al., 2004). Water washing is suspected at CRC-1 but is not expected to be a major factor affecting hydrocarbon compositions in the short term. The results of this subsurface petroleum audit have been pivotal in demonstrating the need for the addition of external tracers, especially for the hydrocarbon components, and provide an integral part of the near-surface, soil gas and atmospheric monitoring activities of the CO2CRC Otway Project. References Boreham, C.J., Hope, J.M., Jackson, P., Davenport, R., Earl, K.L., Edwards, D.S., Logan, G.A., Krassay, A.A., 2004. Gas-oil-source correlations in the Otway Basin, southern Australia. In: Boult, P.J., Johns, D.R., Lang, S.C. (Eds.), Eastern Australasian Basins Symposium II, Petroleum Exploration Society of Australia, Special Publication, pp. 603-627. Boreham, C.J., Underschultz, J., Stalker, L., Freifeld, B., Volk, H., Perkins, E., 2007. Perdeuterated methane as a novel tracer in CO2 geosequestration. In: Farrimond, P. et al. (Eds.), The 23rd International Meeting on Organic Geochemistry, Torquay, England 9th-14th September 2007, Book of Abstracts, 713-714.

Increasing CO2 emissions resulting from the expansion of coal fired power generation capacity and other industry in Queensland suggests that a long-term high capacity storage solution is needed. Despite some relatively large distances (upwards of 500 km) between sources and sinks, a review of the Galilee Basin suggests that it may have the potential to sequester a significant amount of Queensland's stationary CO2 emissions, however a paucity of data in several significant regions do not allow this potential to be fully assessed at the present time. Sandstones with good porosity and permeability characteristics occur within several formations including the Early Permian Aramac Coal Measures, the Late Permian Colinlea Sandstone and the Triassic Clematis Sandstone. Intraformational and local seals as well as a regional seal, the Triassic Moolayember Formation and the Permian Bandanna Formation, appear sufficient although these have not been tested. Stratigraphic and residual/solution trapping are the most likely CO2 storage mechanisms, as low amplitude structures are a feature of the Galilee Basin. Most of the structures targeted by exploration companies are generally too small to store CO2 in the quantities anticipated to be emitted from potential emission nodes such as the Rockhampton-Gladstone region. Regional reconnaissance indicate small 15-20 km2 structures with a 50-125 m net sandstone section are typical for the Clematis Sandstone Formation in the south eastern area of the Galilee Basin. Covering an area of approximately 247,000 km2 and measuring around 700km north-south and 520 east-west, the Galilee Basin is a significant feature of central Queensland. Three main depocentres the Koburra Trough (east), the Lovelle Depression (west) and the Southern Galilee Basin (south) contain several hundred metres of Late Carboniferous to Middle Triassic sediments (up to 3000m, 730m, and 1400m respectively). Most of the low amplitude structures in the basin, generally trending north-easterly to north-westerly, are the result of reactivation of older basement structures in the underlying Drummond and Adavale Basins. Tectonic events were dominantly compressional resulting in uplift and erosion of parts of the basin during the Late Permian and Triassic. A regional south-westerly tilt was later imposed due to downwarping of the overlying Eromanga Basin, which is up to 1200 m thick over the Galilee strata. Sedimentation in the Galilee Basin was dominated by fluvial to lacustrine (and in part glacial) depositional systems. This resulted in a sequence of sandstones, mudstones, siltstones, coals and minor tuff in what was a relatively shallow intracratonic basin. The entire Galilee sequence is saturated with good to excellent quality fresh water in both the Permian and Triassic strata (Hawkins, unpublished) with probable recharge from the north-east into the outcropping Triassic reservoirs. Sediment composition is mixed as a result of a variety of provenances including older sedimentary rock, metasediments and other metamorphic rocks, granites, volcanics and direct volcanic input (tuffs). Climate varied from glacial to warm and humid to temperate. Forty years or more of exploration in the Galilee Basin has failed to discover any economic accumulations of hydrocarbons, despite the presence of apparently good to very good reservoirs and seals in both the Permian and Triassic sequence. Further geological study and in particular the interpretation of seismic data is required to increase the understanding and assess the quality of the basin for CO2 storage including; fully assessing reservoirs, seals and trapping mechanisms; estimating storage capacity; and addressing issues such as the presence of a potentially large fresh water resource.

This report is part of the results of a study into the potential for the geological storage of carbon dioxide within the Triassic Formations of the Galilee Basin in central Queensland carried out in Geoscience Australia on behalf of the CO2CRC. A review of the geological potential of the area has been issued as a separate report (Marsh et al., 2008) and this document describes the construction of a static geological model of one of the potential reservoirs in one area of the basin, while the results of a preliminary dynamic simulation study based on this model will be presented in a separate report by the reservoir engineer Yildiray Cinar of UNSW.

Monitoring is an important aspect in verifying the integrity of the geological storage of greenhouse gases. Geoscience Australia is working with CSIRO, the CO2CRC, the Australian National University, the University of Adelaide and the University of Wollongong to develop and evaluate new techniques to detect and quantify greenhouse gas emissions.