Deep Structure of the Browse Basin Region, North West Shelf Australia: Cruise Proposal

The Browse Basin underlies the outer shelf and upper slope of the central part of Australia'sNorth West Shelf, in water depths of 100-1000 m. Although the North West Shelf is generallyconsidered to be one of Australia's most heavily explored offshore regions, there aresignificant portions of it, such as the offshore Canning and Browse Basins, that remain under-explored. Relatively little is known of the primary structural architecture of the basin systemsof the North West Shelf, and the influence of that architecture on the occurrence ofhydrocarbons. The Browse Basin study (AGSO Project 121.28 - Basin development andhydrocarbon potential of the Browse Basin and adjacent margin) is part of a major AGSOregional research program over the north western Australian margin, and has the following main objectives: 1) Determine the regional structural framework of the Browse Basin and its relationship toadjacent features such as the Vulcan Sub-basin, Rowley Sub-basin, Scott Plateau andKimberley Block; 2) Define the broad deep-crustal structure of the region and develop a model explaining the tectonic, subsidence and thermal history of the basin in relation to the development of thecontinental margin and adjacent ocean basin (the Argo Abyssal Plain); 3) Assess the effects of deep structure and reactivation on the development of knownpetroleum accumulations. To address these objectives it is proposed that RV Rig Seismic be used to acquire about 3200km (up to a maximum of 3600 km depending on contingencies) of deep seismic and othergeophysical data along 11 lines tying 18 exploration wells in the Browse Basin/Scott Plateauregion. The survey will also tie into the 1990 Vulcan Sub-basin survey (98) to the northeast,and the forthcoming survey over the offshore Canning Basin to the southwest. In line with the Marine Geoscience and Petroleum Geology Program's (MGPGP's) most recentdeep seismic surveys over the North West Shelf, the Browse Basin survey will use a 4800 mstreamer, configured with 192 x 25 m active groups; data will be recorded with a 16 secondrecord length, and a 2 millisecond sample interval; the seismic source will be dual airgunarrays with a total capacity of 49 litres, and will be fired every 50 metres to give 48-fold CDPcoverage; and navigation will be by differential GPS. These parameters are the same as usedon two surveys over the northern Carnarvon Basin (SNOWS-1 and SNOWS-2) and threesurveys over the Bonaparte Basin - Timor Sea, and will also be used on the SNOWS-3 surveyover the offshore Canning Basin, following the Browse survey. Using these parametersAGSO has consistently recorded reflections down to 8-12 seconds two-way time (12-20 kmdepth), as well as obtaining good resolution in the upper 6 seconds of data, which is normallythe limit recorded by industry.