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.

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.

A study of the geological prospectivity for carbon dioxide subsurface storage in selected member economies of the APEC (Asia-Pacific Economic Cooperation) region was recently completed. The study is part of a multi-phase program of the APEC Energy Working Group to promote sustainable energy development within the APEC community. APEC economies considered in this study including the Republic of Korea, China, Indonesia, Malaysia, Philippines, Chinese Taipei and Thailand. The objective of the study is to establish a sound understanding of the relationship between the key emission sources and the prospective basins that may contain potential storage sites, and to derive a qualitative assessment of whether the storage potential available in a specific country will meet its storage requirements through the foreseeable future. China has very high emissions and moderate to high prospectivity for storage and Indonesia, Malaysia and Thailand have moderate emissions and moderate storage prospectivity. The Philippines have low emissions and low storage prospectivity, whereas the Republic of Korea and Chinese Taipei both have high emissions and low storage prospectivity.

There remains considerable uncertainty regarding the location, timing and availability of CO2 storage sites in both southeast Queensland and New South Wales. In New South Wales, the main issues relate to the lack of recent or reliable valid geological information that would permit a complete and comprehensive evaluation. Some sedimentary basins appear to contain potential storage reservoirs although they have low permeabilities, and are therefore likely to have low injection rates. In southeast Queensland, recent work has indicated that in some parts of the Bowen and Surat basins CO2 storage is likely to compete with other resources such as groundwater and hydrocarbons. However, current research on the potential storage in deeper saline formations in the southern and western Bowen Basin has provided encouraging results. Storage in deeper stratigraphic units in the central western part of the basin will rely on injection in low permeability formations, and more correlation work is required to define generally narrow storage targets. The Wunger Ridge, in the southern Bowen Basin, however, has promise with both significant storage potential and relatively low geological risk. One area in which there is some potential in both New South Wales and southeast Queensland is CO2 storage in coal seams, as close technical and economic relationships exist between coal bed methane (CBM) field development and operations and CO2 storage. Substantial collaborative research is still required in this area and is currently a focus of the CO2CRC activities

There are numerous isotopic tracers that have the potential to track the movement of CO2 as it is sequestered underground. Their primary role is in verifying the presence of sequestered CO2. These tracers range from CO2 to 3He to PFT?s to SF6. With such a variety of possible tracers, it is important to identify which tracer(s) are (a) economically viable, (b) can be measured appropriately, (c) fit with the specifics of the geological site, and (d) meet the concerns of the public. Tracers can be used either in a continuous mix with the whole body of sequestered gas as an ownership label or in a pulse to monitor changes in the reservoir characteristics of the body of rock hosting the sequestered gas. Rather than going to the expense of adding a tracer to the stream of sequestered CO2 there may be the opportunity to use natural tracers, such as the very CO2 being injected. In the Weyburn Project, the CO2 injected was isotopically distinct from any CO2 that might have been present in the geological system to which it was being added. The CO2 piped from a gasification plant in North Dakota had an isotopic signature quite depleted in 13C (approx. ?13C -20 to -30?; ref Hirsche et al., 2004). This contrasted with the carbonate minerals and any CO2 present in the hydrocarbon reservoir to which the gas was being sequestered as part of an enhanced oil recovery (EOR) project. Unfortunately, the sequestered CO2 may not be as isotopically different as background sources, for example separating CO2 from natural gas prior to re-injection in the same formation. Costs of tracers per litre can range in orders of magnitude; however the cost should be measured as amount per metric tonne CO2 in order to obtain the true cost. Amounts required tend to be controlled by the background atmospheric presence of any tracer and by the sampling methods and locations. For example, the amount of tracer used to monitor subsurface movement of CO2 from an injection to a monitoring well would potentially be very low if that tracer is not present in deep saline aquifers. However, if shallow water bores or soil or atmospheric level measurements are also being taken, then the presence of the tracer in the soil or atmosphere will strongly control how much additional tracer is required to see changes above background. Addition of 14CO2 to sequestered CO2 may be regarded as a cost effective tracer that will closely mimic CO2. However, it will not advance ahead of the sequestered CO2, it will mask natural differences in 13C/14C variations in the soil and atmosphere, and of course is radiogenic and therefore less favored by the public. By contrast, SF6 (sulphur hexafluoride) is also inexpensive, and has been used in a variety of tracer experiments (Tingey et al., 2000 and references therein). However, SF6 is required in larger volumes (engineering issue for mixing), is increasing in presence in the atmosphere (Maiss and Brenninkmeijer, 1998) and is a highly potent greenhouse gas. As an example of its global warming potential (GWP), 5500 tonnes SF6 is the equivalent of releasing 132 million tons of CO2 (Maiss and Brenninkmeijer, 1998).

Australia's coal-based power-stations produce about 70% of its energy needs and consequently have led, to the adoption of a multi-disciplinary approach to instigating low emission technologies, which include CO2 capture, injection and storage. The onshore Bowen Basin could provide potential multi-scale storage site projects. Storage potential was demonstrated within a 256 square kilometer area on the eastern flank of the 60-km by 20-km Wunger Ridge using a regional model pertaining to a potential commercial-scale 200 megawatt power-station with emission/injection rates of 1.2 million ton/year. Palaeogeography interpretations of the targeted reservoir indicate a dominantly meandering channel system with permeabilities of up to 1 darcy on the ridge's eastern flank, waning to a deltaic system downdip. Seismic interpretation indicates a relatively unfaulted reservoir-to-seal section on the flank with low-relief structures. Depth to reservoir ranges from 2100 to 2700-m. Simulation from a simplified 3-D block model indicates at least two vertical wells are needed to inject at 1.2 million ton/year in permeabilities of 1 darcy, and reservoir thicknesses of about 5-m. The presence of intra-reservoir baffles reduces the injection rate possible, with a subsequent increase in the number of wells required to maintain the project injection rate, also true for a low-permeability trapping scenario. Long-term storage of acceptable volumes would involve intra-reservoir baffle, stratigraphic, residual, and potentially depleted field trapping scenarios along a 10 to 15-km migration route. Trapping success is ultimately a function of optimal reservoir characteristics both estimated from more complex modeling and, ultimately, collection of infill seismic and new wells.

No abstract available

The Petrel Sub-basin Marine Survey GA-0335 (SOL5463) was acquired by the RV Solander during May 2012 as part of the Commonwealth Government's National Low Emission Coal Initiative (NLECI). The survey was undertaken as a collaboration between the Australian Institute of Marine Science (AIMS) and GA. The purpose was to acquire geophysical and biophysical data on shallow (less then 100m water depth) seabed environments within two targeted areas in the Petrel Sub-basin to support investigation for CO2 storage potential in these areas. Underwater video footage and still photographic images (12 megapixel resolution) from towed-video were acquired from 11 stations. The quality of imagery varies among transects and some still images were not of suitable quality for analysis. No still images are available for stations 2, 4 and 7 due to system malfunction. Video and still image files and associated parent folders are named by station number, gear code (CAM = underwater camera system) and then the deployment number. For example 'STN08CAM06' would represent a video transect from Station 08 that was the 6th video transect of the survey. Please note that the Ultra-short Baseline (USBL) acoustic tracking system used to track the towed-camera system failed early in the survey; hence geo-location of video transects and stills could only be linked to the R.V. Solander's ship navigation.

Between 3 May 2012 to 24 June 2012 Geoscience Australia undertook two major surveys off the coast of the Northern Territory in the Petrel Sub-Basin. The data acquisition was funded through the National Low Emissions Coal Initiative (NLECI) and the Petrel Sub-basin was selected in particular as it has been identified as a prospective area for CO2 storage. One of these surveys, GA336 acquired 4091 kilometres of 2D seismic reflection data. Following on from the completion of the seismic processing of this data was further investigative work investigative work such as this analysis. Four prime lines, GA336-107, 110, 205 and 207 along with the well logs, Flat-Top1, Petrel 1A and Petrel 4 were selected for further 2D Simultaneous Inversion and Rock Physics Modelling. Previous Pre Stack Depth Migration had been undertaken on these lines and the PSDM Angle Stacks were imported along with the relevant horizon interpretation into the Jason integration algorithms.

Currently there is no uniform methodology to estimate geological CO2 storage capacity. Each country or organization uses its own evaluation and estimation method. During 2011-2012, the International Energy Agency has convened a process among national geological survey organizations to recommend a common estimation method for countries to use. Such a method should describe a typical process for developing assessments of CO2 storage resources; recommend a sound methodology for arriving at a jurisdictional or national-scale CO2 storage resource assessment that could be applied globally; and recommend a way forward to bridge the gap between such a resource and a policy-makers aspiration to understand what proportion of the resource can be relied on and is likely to be technically accessible at any particular cost. This report will outline a 'roadmap' to address these recommendations in a way that jurisdictions can use extant methodologies or craft their own to assess their CO2 storage endowment in a manner consistent with other jurisdictions. In this way they may be able to fully utilize their endowment as well as make a contribution to the potential realization of a worldwide estimate of storage resource.