--> Abstract: Dryland Fluvial-Lacustrine Reservoir Analogues from the Lake Eyre Basin, Australia, by Simon C. Lang, Tobias Payenberg, Mark Reilly, Carmen Krapf, Victor Waclawik, Jochen Kassan, and Saju Menacherry; #90039 (2005)

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Dryland Fluvial-Lacustrine Reservoir Analogues from the Lake Eyre Basin, Australia

Simon C. Lang1, Tobias Payenberg1, Mark Reilly1, Carmen Krapf1, Victor Waclawik1, Jochen Kassan2, and Saju Menacherry3
1 Australian School of Petroleum, University of Adelaide, Adelaide, Australia
2 Whistler Research, Brisbane, Australia
3 Australian School of Petroleum, Adelaide, Australia

Dryland fluvial systems and their associated terminal splays and lacustrine deltas are increasingly recognised as important petroleum reservoirs (e.g. northern and central Africa, the North Sea and the South Caspian Sea). The Lake Eyre Basin of central Australia provides excellent modern analogues to improve our understanding of depositional processes and sedimentary architecture of dryland successions in arid to hyper-arid, low-accommodation intracratonic basin settings. Useful insights are gained from observations of rare flood events, and from detailed mapping, trenching, GPR surveys, coring and dating of sand-prone Quaternary sandy dryland deposits around the fringes of Lake Eyre.

Typical reservoir elements include low-sinuosity sandy in-channel fluvial barforms, and heterolithic floodplain deposits. Characteristic reservoir elements, however, include narrow distributive avulsion channels and terminal splay sheet sands built over desiccated floodplain or playas. True lacustrine deltas may build sheetlike fining-upward mouthbar deposits if the flow enters a shallow body of standing water. Sedimentation occurs during rapidly decelerating flows from high-, transitional- to low-flow regime conditions producing parallel lamination, upward convex parallel lamination, climbing ripples and small-scale 2D and 3D dunes. Vegetation-related sediment trapping, and aeolian deflation are significant processes with important reservoir quality implications. The main controls on sedimentary architecture include the low-accommodation setting and climate-controlled major lake-filling events that can be out-of-phase with individual river flows around the playa lake. Depositional products are either high-net-to gross fluvial-terminal splay sheet sands or lower net-to-gross fluvial-terminal splay-lacustrine delta sand sheets or stringers. Playa muds, floodplain fines and abandoned channel mud-plugs are the main baffles and seals.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005