Overview of the Deep Crustal Seismic surveys conducted by Geoscience Australia and funded through the Onshore Energy Security Program since it's commencement in 2006 to September 2009.

Deep seismic reflection profiles collected offshore during a circum-navigation of Tasmania have provided fundamental information on the crustal architecture of the State. In particular, the profiles show the geometry of the boundaries between the major crustal elements, including the offshore continuation of the Arthur Lineament. These crustal element boundaries have apparent dips to the east or southeast and most of them appear to cut through the entire crust to the Moho. In eastern Tasmania, the seismic lines show an old mid-crustal extensional event followed by crustal shortening and duplexing, which probably occurred during the Cambrian-Ordovician Delamerian Orogeny. Thrusts that developed at this time were later reactivated as extensional faults during continental breakup of Pangea in the Cretaceous. Granites off the west coast have the geometry of flat, thin pancakes. In summary, the offshore seismic reflection program around Tasmania has led to a better understanding of the geometry and relationships between the basement elements of Tasmania and younger basins.

Case Study: GeoFrame software helps Geoscience Australia provide quick access to 2D and 3D seismic survey data within newly released license/permit in support of successful Australian Acreage Release bidding rounds

Geoscience Australia is conducting a study under the National Carbon Infrastructure Plan (NCIP) to assess the suitability of the Vlaming Sub-basin for CO2 storage. It involves characterisation of the Valanginian reservoir (Gage Sandstone) and the Early Cretaceous seal (South Perth Shale) by integrating seismic interpretation and well log analysis in a detailed sequence stratigraphic investigation. The Gage Sandstone, comprised of channelised turbidites and mass flows, was the first unit deposited after breakup between India and Australia. Deposited during a sea level lowstand in the palaeo-topographic lows of the breakup unconformity, it is overlain by a thick deltaic to shallow marine succession of the South Perth Shale. The Gage Sandstone is considered one of the best reservoirs in the sub-basin with porosities of 23-30% and permeabilities of 200-1800 mD. It occurs at depths between 1000 and 3000 m below the seafloor, which makes, it an attractive target for the injection and long-term storage of supercritical CO2. The new extent of the Gage Sandstone, based on seismic interpretation and well log correlation, shows that in some of the wells the sandstone unit overlying the Valanginian unconformity belongs to the South Perth Shale and not to the Gage Sandstone. The G. Mutabilis palynological zone used in the past for identifying Gage Sandstone interval appears to be facies controlled and time transgressive. Detailed analysis of the reservoir properties at the wells in conjunction with systematic seismic facies mapping will serve as a basis for a regional reservoir model and storage potential estimation of the Gage Sandstone reservoir.

The Capel and Faust basins lie at water depths of 1,500-3,000 m 800 km east of Brisbane. Geoscience Australia began a petroleum prospectivity study of these remote frontier basins with the acquisition of 2D geophysical data (seismic reflection, refraction, gravity, magnetic, multi-beam bathymetry) across an area of 87,000 km2 during 2006/07. The approach mapped the complex distribution of sub-basins and determined sediment thickness through integration of traditional 2D time-domain seismic interpretation techniques with 3D mapping, visualisation and gravity modelling. Forward and inverse 3D gravity models were used to inform the seismic interpretation process and test the seismic basement pick. Gravity models had three sediment layers with inferred average densities of 1.85, 2.13, 2.31 t/m3 overlying a pre-rift basement of density 2.54 t/m3, itself considered to consist of older basin material evidently intruded by igneous rocks. Conversion of travel times of interpreted seismic horizons to depth domain was achieved using a quadratic function derived from ray-tracing forward modelling of refraction data supplemented by stacking interval velocities, and densities for gravity modelling were inferred from the same velocity models. These models suggest sediment of average velocity 3.5 km/s reaches a thickness exceeding 6 km in the northwest of the area, and for the first time mapped the extent and depth of sediment in these basins. The results of the study have confirmed that sediment thickness in the Capel and Faust basins is sufficient in places for potential petroleum generation.

The granite-greenstone terrains of the Eastern Goldfields Province, Yilgarn Craton, are extremely important as a major Australian gold province. The Kalgoorlie region, in particular, hosts several world class gold deposits. A grid of deep seismic reflection lines was acquired in 1999 to examine the three-dimensional geometry of the major structural features in the region within an area of the Kalgoorlie - Ora Banda region of the Eastern Goldfields Province, Yilgarn Craton. These seismic lines presented an ideal opportunity to further develop our 3D understanding of this highly mineralised granite-greenstone terrain. The seismic grid tied into the earlier 1991 regional deep seismic traverse and the more recent 1997 regional and high-resolution profiles acquired in the region. It covered and area approximately 50 km square that extended to a depth of approximately 35 km (ie the base of the crust in this area). The resulting seismic grid was well suited to the development of a three-dimensional model of the region that could be used to investigate the spatial relationships of the greenstones and the granites. The 3D geological model of this region was built using a 3D modelling software package, GOCAD(r). It was built using surface geological data and geological interpretations of the region's deep and high-resolution seismic reflection profiles. The latter seismic interpretations were constrained by gravity modelling.

This data set consists of processed seismic reflection data for line 01AGS-NY3 from the 2001 Northern Yilgarn seismic survey (L154), Western Australia. Line 01AGS-NY3 was located east of Lake Yeo within the Officer Basin and was acquired with vibratory sources at nominal 60 and 120 fold coverage by the Australian National Seismic Imaging Resource (ANSIR). The seismic data are provided as SEG-Y files of stack and migrated data to 4 seconds and 16 seconds two-way time, at a sample interval of 4 milliseconds. The CDP range is 2080 to 5507 with 15 metre CDP interval. SEG-Y header information, CDP coordinates as eastings and northings, and a pdf image of the migrated 16 second seismic section are also included. The line, migrated section images and further information on this data can be obtained from the <a href="http://www.pmdcrc.com.au" target="_blank">pmd*CRC</a> website.

Initial 2D seismic survey using mini-vibroseis with high frequency band 10 - 150Hz. This seismic survey is part of the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) projects.

Legacy product - no abstract available

Current geological mapping by the Northern Territory Geological Survey is leading to a much better understanding of the surface geology of the Territory. Less well understood is the geometry of the Northern Territory in the third dimension, although this has been predicted by the construction of cross sections (e.g. on recent 1:250 000 geological maps). At shallow depths, the cross sections can be constrained by drilling results, if available, but deeper levels can only be examined by geophysical techniques such as seismic reflection or magnetotelluric profiling, or by modelling of potential field data. Text of paper presented at the NTGS AGES 2002 Workshop, Alice Springs, 26-27 March 2002.