Aquifer characterisation and groundwater resources of Dili, East Timor

Abstract for indonesian Geophysics Conference (HAGI)

Old, Flat and Red: the Origins of the Australian Landscape Colin Pain, Geoscience Australia, Lisa Worrall, Geoscience Australia, and Brad Pillans, Research School of Earth Science, Australian National University

The use of airborne electromagnetics (AEM) for hydrogeological investigations often requires high resolution data. Optimisation of AEM data therefore requires careful consideration of AEM system suitability, calibration, validation and inversion methods. In the Broken Hill managed Aquifer Recharge (BHMAR) project, the helicopter-borne SkyTEM transient EM system was selected after forward modeling of system responses and assessment of test line data over potential targets. The survey involved acquisition of 31,834 line km of data over an area of 7,500 km2 of the River Darling Floodplain, and was acquired by two systems over a 9-week period.. Initial Fast Approximate Inversions (FAI) provided within 48 hours of acquisition were used to target 100 sonic and rotary mud holes for calibration and validation. A number of different (Laterally and Spatially Constrained) inversions of the AEM data were carried out, with refinements made as additional information on vertical and lateral constraints became available. Finally, a Wave Number Domain Approximate Inversion procedure with a 1D multi-layer model and constraints in 3D, was used to produce a 3D conductivity model. This inversion procedure only takes days to run, enabling the rapid trialing to select the most appropriate vertical and horizontal constraints. Comparison of borehole induction logs with adjacent AEM fiduciary points confirms high confidence levels in the final inversion. Using this approach has produced quantitative estimates of the 3D conductivity structure that provide a reliable platform for identifying new groundwater resources and a range of MAR options, and developing new geological and hydrogeological conceptual models. Integration of the AEM data with borehole lithology, textural, mineralogical, groundwater and pore fluid hydrochemical and borehole NMR data has enabled maps of hydrostratigraphy, hydraulic conductivity, groundwater salinity, salt store and neotectonics to be produced.

Understanding the potential magnitude, severity and impact of future volcanic eruptions on communities living in close proximity to volcanic sources is essential for any attempt to reduce natural disaster risk in Papua New Guinea. Geoscience Australia is working in partnership with the Rabaul Volcanological Observatory (RVO) to build the capacity of volcanologists to undertake volcanic ash dispersal modelling, to interpret the outputs and to incorporate the data where appropriate into a new series of volcanic hazard maps for a pilot province (East New Britain; ENB). A modified procedure for volcanic ash dispersal modelling (PF3D) was developed in 2009 by Geoscience Australia and its regional partners in Indonesia and the Philippines which modify the modelling procedure of FALL3D, a widely used and well validated volcanic ash dispersal model, in line with the needs of government agencies and emergency managers in the Asia-Pacific region. PF3D introduces a number of enhancements to the procedure for FALL3D that do not change the operation or functionality of the core model but increase its accessibility for volcanologists working in developing countries like Papua New Guinea. The three year program, funded by the Australian Agency for International Development (AusAID) provided training in the use and application of PF3D for RVO staff through the development of new volcanic hazard and risk information for ENB. A significant achievement for the program has been the continuous involvement of community groups who, through a series of workshops held in ENB, have been heavily involved in discussions around the kind of volcano science being undertaken, providing feedback on outputs and in driving the design and production of education and public awareness materials (books, posters etc) which will be used for communicating the outputs of the program in local schools and other community centres as part of a larger planning and preparedness campaign.

Abstract for initial submission, pending acceptance by convention technical program committee.

Regional airborne electromagnetic (AEM) data provide valuable information for mapping the shallow crust. Data are particularly useful for mapping buried paleotopography including paleovalleys and paleochannels, showing the depth to conductive geological units (and perhaps related faults), and altered and weathered unconformity surfaces, that may be less evident in other regional datasets. Geoscience Australia (GA) has recently acquired and released regional AEM data in the Paterson area of Western Australia, which is one of the most highly prospective areas in Australia. GA is currently in the process of assessing the potential of basinal fluid-related uranium systems in the area, including unconformity-related, sandstone-hosted and calcrete-hosted systems. Interpretation uses this key dataset, along with other available geological, geophysical and remotely sensed data and publicly available drill hole data, Outputs of this assessment include a number of prospectivity maps for these uranium systems. Preliminary interpretations of the AEM data have identified paleovalleys containing Permian and younger sediments and fluid pathways as aquifers in Permian and younger sediments on-lapping the Rudall Complex, Fortescue Basin and Pilbara Craton. In some places, the AEM data map unconformities of Mesozoic over Permian and Permian over the Neoproterozoic Yeneena and Officer Basins and Mesoproterozoic Rudall Complex. The unconformity surface between the Neoproterozoic Yeneena and Officer Basin sediments over rocks of the Rudall Complex or Pilbara Craton appears poorly defined in the data. The AEM data are opening up new avenues of investigation for uranium systems and have shown the utility of flying regional AEM surveys over highly prospective areas.

Groundwater monitoring around the CO2CRC Otway Project CO2 injection site aims to (1) establish baseline aquifer conditions prior to CO2 injection, and (2) enable detection monitoring for CO2 leakage, in the unlikely event any should occur in the future. The groundwater composition was monitored at 24 bores around the site for nearly 2 years before injection started. The water samples were analysed for standard bulk properties, and inorganic chemical and isotopic compositions. In addition to sampling, standing water levels were monitored continuously in 6 of the bores using barometric loggers. The shallow groundwaters have compositions typical of carbonate aquifer-hosted waters, being fresh (EC 800-4000 S/cm), dominated by Ca2+, Na+, HCO3- and Cl-, cool (T 12-23°C), and near-neutral (pH 6.6-7.5). Most of the deep groundwater samples are fresher (EC 400-1600 S/cm), also dominated by Ca2+, Na+, HCO3- and Cl-, cool (T 15-21°C), but are more alkaline (pH 7.5-9.5). Time-series reveal that most parameters measured have been relatively stable over the sampling period, although some bores display changes that appear to be non-seasonal. Groundwater levels in some of the shallow bores show a seasonal variation with longer term trends evident in both aquifers.

Geological Survey of South Australia SAREIC Technical Day conference 2015

Update on Australia's oil and gas activities with a focus on recent exploration successes and promotion of open offshore acreage