Peter Petkovic

Depth to magnetic sources in the offshore northern Perth Basin

Summary During 2009-11 Geoscience Australia completed a petroleum prospectivity study of the offshore northern Perth Basin. Basement in the northern Perth Basin is deep and generally not resolved in the reflection seismic data. Recent improvements to the magnetic ship-track database and magnetic anomaly grid allowed an assessment of depth to magnetic sources, and estimation of sediment thickness, providing new insight into basement depth and trends. 2D models along seismic transects and analysis using spectral methods indicate that penetration of the deepest sediments by highsusceptibility bodies is probable. The reflection seismic evidence for these bodies is not clear, though in some cases they may be associated with faults and structural highs. Where the modelled bodies penetrate the sediments they are mostly below or within the Permian strata. A moderate positive magnetic anomaly (the Turtle Dove Ridge) is modelled by massive bodies whose tops are 5-15 km below sea floor. The depth to magnetic basement map highlights sub-basins and structural highs within the northern Perth Basin, with up to 12 km of sediment in the Zeewyck sub-basin.

Geophysical studies of Australia's remote eastern deep-water frontier: results from the Capel and Faust Basins

Introduction The Capel and Faust basins are located in a frontier part of offshore eastern Australia, about 800 km east of Brisbane in 1000–3000 m of water (Fig. 1). These basins are being evaluated for their petroleum potential as part of the Australian Government’s Offshore Energy Security Program. This article outlines the current status of integrated interpretation of 2D seismic reflection, sonobuoy refraction and potential-field data acquired during Geoscience Australia marine survey GA-302 conducted between late 2006 and early 2007. This survey collected 5920 km of high-quality 106-fold seismic reflection data using an 8 km streamer to 12 s two-way time at 37.5 m shot interval and a line spacing of 20–50 km. A subsequent swath-bathymetry and geological sampling survey (GA-2436), completed in late 2007, also collected potential-field data in the north-west of the study area with a 3–4 km line spacing (Fig. 1). These data have been integrated in 3D to help constrain the geometry and thickness of sediment depocentres in the region.