Abstract

Reservoir characterization in fluvio-lacustrine successions is significantly improved by the use of appropriate modern and ancient analogues to understand reservoir architecture and to help build scaled reservoir models. We document here the use of modern and ancient analogues for a coal-measure fluvial system (Toolachee Formation) and a lacustrine delta succession (Epsilon Formation). Both units are from the Permian sequence of the Cooper Basin in Queensland and South Australia, and occur entirely in the subsurface, making detailed outcrop study of these important reservoir formations impossible.

The Upper Permian Toolachee Formation comprises fluvial, crevasse-splay and crevasse-delta reservoirs. Modern depositional examples from the Ob River in western Siberia are used to illustrate the relative scale of fluvial channels and crevasse splays within avulsion belts in a peat-forming environment. The South Blackwater coal mine in the Permian Bowen Basin is used as an analogue to quantify the 3-D geometry, and reservoir architecture of crevasse splays and lacustrine deltas, to determine likely subsurface reservoir heterogeneity.

Shallow water lacustrine delta deposits of the Lower Permian Epsilon Formation form important reservoirs with significant potential for stratigraphic traps. Little data is available in the literature documenting such depositional settings and the resulting sediment geometries. A field study of the modern Neales Delta in Lake Eyre provides a modern analogue for the depositional processes and depositional geometries in such a setting. The subsurface Tertiary lacustrine deltaic complex of the Sirikit Field from the Phitsanulok Basin, central Thailand, is selected as an ancient analogue for the multistory reservoirs developed within amalgamated mouth bar complexes intersected in the Lower Epsilon Formation.