There is increasing recognition that minimising methane emissions from the oil and gas sector is a key step in reducing global greenhouse gas emissions in the near term. Atmospheric monitoring techniques are likely to play an important future role in measuring the extent of existing emissions and verifying emission reductions. They can be very suitable for monitoring gas fields as they are continuous and integrate emissions from a number of potential point and diffuse sources that may vary in time. Geoscience Australia and CSIRO Marine & Atmospheric Research have collected three years of continuous methane and carbon dioxide measurements at their atmospheric composition monitoring station ('Arcturus') in the Bowen Basin, Australia. Methane signals in the Bowen Basin are likely to be influenced by cattle production, landfill, coal production, and conventional and coal seam gas (CSG) production. Australian CSG is typically 'dry' and is characterised by a mixed thermogenic-biogenic methane source with an absence of C3-C6+ alkanes. The range of '13C isotopic signatures of the CSG is similar to methane from landfill gas and cattle emissions. The absence of standard in-situ tracers for CSG fugitive emissions suggests that having a comprehensive baseline will be critical for successful measurement of fugitive emissions using atmospheric techniques. In this paper we report on the sensitivity of atmospheric techniques for the detection of fugitive emissions from a simulated new CSG field against a three year baseline signal. Simulation of emissions was performed for a 1-year period using the coupled prognostic meteorological and air pollution model TAPM at different fugitive emission rates (i.e. estimates of <1% to up to 10% of production lost) and distances (i.e. 10 - 50 km) from the station. Emissions from the simulated CSG field are based on well density, production volumes, and field size typical of CSG fields in Australia. The distributions of the perturbed and baseline signals were evaluated and statistically compared to test for the presence of fugitive methane emissions. In addition, a time series model of the methane baseline was developed in order to generate alternative realizations of the baseline signal. These were used to provide measures of both the likelihood of detecting fugitive emissions at various emission levels and of the false alarm rate. Results of the statistical analysis and an indicative minimum fugitive methane emission rate that can be detected using a single monitoring station are presented. Poster presented at the American Geophysical Union meeting, December 2013, San Francisco

As part of the National CO2 Infrastructure Plan, Geoscience Australia is undertaking a three year project to provide a detailed assessment of the Vlaming Sub-basin prospectivity for the geological storage of CO2. An important part of this assessment is an evaluation of the seal quality and integrity, including analysis of fault reactivation, signs of seepage, as well as lithological variability within the seal. Over a large area the Gage reservoir is underlain by the Charlotte reservoir (Figure 1). Based on well data, the two reservoirs are at least partially connected. Due to limited data, the Charlotte reservoir was not considered by the previous studies for additional storage capacity. Even if Charlotte Sandstone is not considered for storage, it presents a base seal issue for CO2 storage in the Gage reservoir, which needs to be addressed. The current study mapped the Charlotte reservoir and analysed its potential impact on the containment of CO2. Initial results of this study are outlined below.

Geological storage of CO₂ requires fundamental knowledge and predictive capabilities on the transport and reactions of injected CO₂ and associated gases to assess the short and long term consequences. CO₂ can be stored in the subsurface through various mechanisms including structural trapping, solubility trapping and by precipitation of carbonate minerals. While mineral strapping is considered to be the safest storage mechanism as it permanently immobilizes the CO₂, the reaction rates and the likely importance for geosequestration is poorly understood. This project has five objectives, which aim to make CO₂ storage more predictable and safer. A range of approaches will be used including desk top studies, laboratory and field experiments and geochemical modelling.

Regional geological properties of sedimentary basins play a significant role in determining the safety of CO2 storage. Four major trapping mechanism have been identified: Structural and stratigraphic trapping is the containment of supercritical CO2 by low permeability / low porosity rocks and is the dominant mechanism during injection and initial storage phase. Residual or capillary trapping is the retention of supercritical CO2 in the pore space between grains and tends to be most relevant on a scale of tens to thousands of years. Solubility trapping is the uptake of CO2 into the formation water, which is considered to be the most important trapping mechanism over hundreds to millions of years (1). Mineral trapping leads to the permanent immobilization of carbon through the precipitation of carbonate minerals. This study assesses the conditions for solubility trapping in major Australian sedimentary basins. The total dissolved solid (TDS) concentration of the formation water has been compiled from over 900 wells as it, along with pressure and temperature, is a key variable controlling CO2 solubility and the associated change in fluid density. Fluid density is a critical factor in driving fluid advection which determines the rate of solubility trapping and downward migration in the formation. This process is vital in reducing the amount of highly mobile supercritical CO2 at the top of the formation and storing it as dissolved CO2 in deeper parts of the formation.

Geoscience Australia is the national mapping agency, providing fundamental geoscientific data in support of mineral and petroleum exploration.

This map is an attractive representation of the relief of Australia with north-west illumination. The elevation image was derived from Geoscience Australia`s GEODATA 9 Second Digital Elevation Model (DEM) with a grid spacing of 9 seconds of latitude and longitude (approximately 250 metres on the ground). Over 5 million spot height values were used in the generation of the DEM.

Poster prepared for International Association of Hydrogeologists Congress 2013 Sonic drilling is a relatively new technology that was used successfully to obtain relatively uncontaminated and undisturbed continuous core samples with excellent (>99%) recovery rates to depths of 206m in unconsolidated fluvio-lacustrine sediments of the Darling River floodplain. However, there are limitations with the standard sonic coring method. Sands, in particular, are disturbed when they are vibrated out of the core barrel into the flexible plastic sampling tube. There can be changes to moisture content, pore fluid chemistry and sediment mineralogy on exposure to the atmosphere, even when the samples are processed and analysed soon after collection. The option exists during sonic drilling to encapsulate the core in rigid polycarbonate lexan tubes. Although this increases costs and reduces drilling rates, atmospheric exposure of the core during drilling is reduced to the ends of the lexan tubes before being capped. In addition, the tubes can be purged with an inert gas such as argon. Lexan coring is best carried out below the watertable as the heat from drilling dry clays can cause the polycarbonate to melt. In the study, 60 sonic holes (4.5 km) and 40 rotary mud holes (2 km) were obtained as part of a program to map and assess potential groundwater resources and managed aquifer recharge (MAR) targets over a large area (7,500 km2) of the Darling River floodplain. Two of the sonic bores were drilled to depths of 60 metres to obtain lexan-encapsulated core samples. These cores were used to obtain less perturbed samples for pore fluid analysis (salinity, major ions, trace metals, stable isotopes), textural analysis, and analysis of mineral phases to help assess aquifer clogging potential (using XRD, XRF, SEM). An additional advantage of the lexan coring was the recovery of encapsulated and intact sediment intervals for determining porosities, effective porosities, hydraulic conductivities, and other geophysical and petrophysical measurements. By painting some tubes black, sand samples were also successfully obtained for optically stimulated luminescence (OSL) dating. Alternatively, opaque black lexan can be made to order by the supplier. Overall, the superior sample integrity obtained from lexan coring enables a greater range of hydrogeological and hydrochemical parameters to be assessed.

To follow

Exhibition/Conference display consisting of 3 new panels (will also be used at Open Day). Panels content includes: water observations from space image and introductory text to this mapping.capability.

The first RSTT model for Australia has been developed based on the Australian Seismological Reference Model (AuSREM) that was released in late 2012. The densely-gridded P and S wave distributions of the crust and upper mantle of AuSREM have been simplified and translated into the 7 layer crustal and upper mantle RSTT model. Travel times computed with this RSTT model are evaluated against travel times computed in full 3D through the AuSREM model to assess the impact of the approximations used by RSTT. Location estimates of 5 ground truth earthquakes (GT1, GT2 and GT5) using the global ak135 reference model, the RSTT model and the full 3D travel times are compared. It is found that the RSTT model can reproduce the 3D travel times fairly accurately within its distance of applicability, thereby improving location estimates compared to using a global travel time model like ak135. However the benefit of using RSTT for locating Australian earthquakes is far less than using full 3D travel times, mainly because most stations tend to be further away from the source than the distance of RSTT applicability.