New insights into the deep-water Otway Basin – Part 1. Integrated depth imaging workflows unravelling the subsurface

The Otway Basin is a northwest-southeast trending passive margin rift basin over 500 km long and forms part of the Jurassic-Cretaceous Australian Southern Rift System. Exploration for oil and gas has, to date, focused on the onshore shelfal portions targeting thick early Cretaceous depocentres. Outboard, under deep-water areas, potential hydrocarbon resources in thick late Cretaceous depocentres remain significantly under-explored, with limited sparse legacy 2D seismic lines and no wells drilled to date. As a result, little is known about the potential continuation of the proven hydrocarbon plays, or indeed the presence of new plays, in the outboard areas. The 2020 Otway Basin seismic program was carried out with the key objectives being to infill data gaps outboard through the acquisition of new 2D seismic lines and improve the quality of legacy datasets inboard through reprocessing. A comprehensive broadband processing and depth imaging workflow was designed to address the inherent subsurface challenges that have inhibited legacy imaging campaigns. The results of this seismic program are improving the interpretability of the full stratigraphic sequence whilst also unravelling deeper crustal elements. This is providing a better understanding of the distribution of regional stratigraphic sequences, both laterally across the basin, and from the shelf to deep-water areas for the first time. As a result, new insights are being gained on both the basin evolution and potential for working petroleum systems.