VGP Technical Report 6 - Full Spectrum FALCON® airborne gravity and aeromagnetic survey
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Product description:About the Victorian Gas Program: The Victorian Gas Program (VGP) is a comprehensive science-led program, incorporating geoscientific and environmental research to assess the risks, benefits and impacts of potential onshore conventional gas exploration and production. The program is also investigating the potential for further discoveries of onshore conventional and offshore gas in the Otway and Gippsland geological basins and assessing the feasibility of additional onshore underground gas storage in depleted reservoirs around the Port Campbell area. The VGP includes an extensive, proactive and phased community and stakeholder engagement program, through which the results of the scientific studies are being communicated. Executive summary: A new airborne gravity, gravity gradiometry and magnetic survey has been undertaken as part of the Victorian Gas Program (VGP) using CGG’s FALCON® airborne data acquisition system. The survey was acquired using two small aircraft that were flown out of Warrnambool Airport. The surveyed region includes approximately 16 000 km2 of the Otway Basin in Victoria, stretching from the edge of the Otway Ranges to the South Australian border, and from south of the Grampians to approximately 18 km offshore. As part of the VGP, the Geological Survey of Victoria (GSV) is studying petroleum systems components (reservoir, seal, source) to assess the petroleum prospectivity of the Victorian Otway Basin and estimate the potential for further conventional gas discoveries, onshore and offshore within Victoria’s jurisdiction. This includes studying the underlying shape of geological structures within the Otway Basin. Along the Victorian Otway Basin offshore within the three nautical mile zone, there is a lack of data acquired to understand the underlying geology. The VGP was therefore designed to include an airborne gravity survey that would provide data coverage of the three nautical mile zone and the adjoining area within the basin. Airborne gravity surveys measure extremely small variations in Earth’s gravity field from a moving aircraft. The resulting imagery from an airborne gravity survey can then be interpreted to determine the underlying geometry of a sedimentary basin and the geological structures within a basin. CGG Aviation Australia Pty Ltd was engaged by GSV to acquire and process the airborne gravity and gravity gradiometry survey. The survey was carried out by two small, fixed wing aircraft, carrying gravity and magnetic instrumentation. The planes flew in public airspace at an altitude of 150 metres, increasing to 300 metres over built-up areas. A single engine Cessna Grand Caravan 208B was used to conduct the onshore portion of the survey and a DHC-6-100 (Twin Otter) aircraft was used for the offshore component. Flying commenced in August 2018 and was completed by early January 2019 (12 weeks). The aircraft only operated during daylight hours and only in favourable weather. The planes collected a total of 31 042 line km of gravity, gravity gradiometry (Full Spectrum), magnetic and laser scanner data along 500 m spaced lines in a NW-SE orientation and 15000 m perpendicular tie lines. The survey has resulted in the largest airborne gravity dataset ever collected in Victoria and provides superior quality gravity imagery, compared with pre-existing data. Once the survey data is analysed, the information will assist GSV to refine 3D geological models that have been constructed from seismic and well data, uncovering new structural information. This in turn will assist with GSV’s geoscience understanding of the potential for future conventional gas resources in the Otway Basin, in particular, within the three nautical mile zone. Bibliographic reference: Carter, S., van Galder, C., Mohammed-Nour, J., Reeve-Fowkes, M., Cowey, D., McLean, M.A., Haydon, S.J., Lane, R.J., & Zengerer, M., 2019. Full Spectrum FALCON® airborne gravity and aeromagnetic survey, Otway Basin, Victoria. Victorian Gas Program Technical Report 6. Department of Jobs, Precincts and Regions. Download: The downloadable version of this report is supplied in PDF format (78.7 MB), Attachment A1 ASEGGDF2 format (ZIP 3.8 GB), Attachment A2 Geosoft format (ZIP 4.6 GB), Attachment A3 (XLSX 34KB) and accessible version (DOCX 27.6 MB). | ||||||
