AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Seismic Stratigraphy and Reservoir Sedimentology of Wave-Dominated Delta and Slope-Basinal Turbidite Reservoirs, Cretaceous Lower Barrow Group, Wa-390-P, North Carnarvon Basin, Western Australia
(1) Hess Exploration Australia, Perth, WA, Australia.
(2) Hess Exploration Technology, Houston, TX.
Exploration for gas accumulations in the Exmouth Plateau, Western Australia relied heavily upon analysis of 3D seismic, well logs, core data and biostratigraphy. Exceptional resolution of structural, stratigraphic and seismic geomorphological details have fostered the construction of a robust view of the depositional and stratigraphic evolution of a linked wave-dominated delta and slope-to-basin-floor turbidite system.
The shape and orientation of the delta front shorelines, which are revealed by seismic amplitude slices, show that littoral drift was locally to the east. Core from topset strata indicate shallowing upward parasequences made up wave and storm-generated structures with lower-upper shoreface ichnogenera. Clinoform geometries reveal rising and falling trajectories associated with variations in accommodation and sediment supply. During falling trajectories, the slope was demarcated by gullies that serve as the main delivery systems for sediment-gravity flows into the basin. High-quality sand was fed from the delta shoreface to the slope and basin floor and deposited as coalescing fans and aprons. Deposition on the slope and the basin floor was strongly influenced by antecedent rift topography, as indicated by onlap and downlap relationships observed at the depocenter
margins.
Numerous wells have been drilled through the slope and basin floor succession encountering sediment gravity flow deposits at different morphologic positions and under contrasting stratigraphic conditions. With the use of detailed biostratigraphic markers, the deposits could be constrained revealing their sub-seismic stacking patterns and variability in reservoir quality facies. Cored intervals indicate the presence of coarse grained, high density turbidites and to a lesser extent cohesive debris flows and low density turbidites.
The Lower Barrow Group is an excellent example of a wave-dominated delta and slope-to-basin floor turbidite system illustrated within a holistic data set. Variations in accommodation and sediment supply are manifested in the architecture and distribution of reservoir quality facies within the depositional environments.