Sequence stratigraphic concepts and techniques provide a powerful tool to analyse and predict stratal architecture and facies patterns within sedimentary basins. The concepts are based on an analysis of cyclic sedimentation patterns in terms of changes in sediment accommodation and sediment supply. Sediment accommodation, the potential space available for sediments to accumulate, is controlled by the combined effects of eustasy and tectonic subsidence or uplift. Sequence stratigraphy involves the analysis of these sediment accommodation cycles within a time-stratigraphic framework, and subdivides sedimentary successions on the basis of key surfaces (unconformities, flooding surfaces) into a systematic and predictable distribution of depositional units or system tracts. The distribution of petroleum systems and key petroleum play elements (e.g., sand-shale ratio, reservoir type and connectivity, organic-rich shales and coals, marine shale seals etc,) can also be shown to be largely controlled by changes in sediment accommodation and sediment supply, Thus, sequence stratigraphic techniques provide a powerful tool to analyse petroleum systems and to predict the distribution of potential reservoirs, sources and seals for hydrocarbon accumulations. The basic principles of sequence stratigraphy are independent of time and scale, such that large-scale sequences can be successively divided into progressively smaller scale or higher order sequences. This notion of sequence hierarchy has important implications for hydrocarbon exploration, since the relative degree of development or dominance of depositional systems tracts (and their constituent play elements) is determined by the position of a particular sequence within a lower order sequence. These lower order sequences thereby determine source-prone or reservoir-prone fairways. Sequence stratigraphic concepts are now routinely applied to hydrocarbon exploration in Australia, including: the prediction of regional hydrocarbon systems, the search for specific depositional systems and reservoir-seal plays, and the hig h-resolution analysis of reservoirs for field development purposes, A review of recent applications to regional and specific hydrocarbon systems in the onshore Canning and offshore Carnarvon Basins highlights the potential of these techniques to influence future exploration strategy and mitigate exploration risk in Australias onshore and offshore basins.
