Crustal Structure of the Bonaparte Basin: Evidence From Deep Seismic Data and Gravity Models

Abstract

Phase 1 of the WestraliaSPAN 2D regional program extended across all basins of Australia's North West Shelf (Carnarvon/Roebuck/Browse/Bonaparte basins) and Arafura regions, although it was restricted to Australian waters. In 2014, an additional 2500 km of new data was collected during Phase 2, which extends the survey to Timor and neighbouring islands. Phase 2 of the survey was designed with long offset and record length (18 sec) acquisition parameters to image the deep crustal and sub crustal architecture and depositional systems across this complex margin. The regional program provides unique, state-of-the-art depth imaging of the deep structure of the Westralian Superbasin, lower crust and Moho. The survey now has multiple transects across the Bonaparte Basin which cross the transition from unextended continental, through hyperextended, transitional and oceanic crust and now includes the Timor accretion complex. An integrated geological and geophysical interpretation encompassing available well, seismic and potential field data was undertaken. Gravity models were developed to aid in seismic depth conversion and the structural interpretation of the deep crust and Moho. A comprehensive model for basin formation provides the context for regional correlation of tectonostratigraphic packages throughout these linked basin systems, highlighting pre-Jurassic basins and their structural controls. Combined seismic velocity and gravity models along the newly acquired Timor data also suggest that there may be essentially no continental crust remaining beneath the Westralian Superbasin and Timor accretion complex. When combined with Phase 1 of the WestraliaSPAN 2D survey, the Phase 2 data provide insight into the distribution of volcanic and originally non-volcanic-hyperextended crust along the entire length of the North West Shelf. While the North West Shelf, Browse and Bonaparte basins are proven and established hydrocarbon provinces, a future step-change in exploration concepts is required, which involves an integrated, margin-scale understanding of these basin systems and their potential resources. Collectively, the new dataset and interpretation will aid explorers in understanding the nature and distribution of key petroleum systems elements (reservoir/source/seal) and processes (heat-flow, timing of source maturity, expulsion, migration and entrapment).

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015