APPLICATIONS OF MODERN AND ANCIENT GEOLOGICAL ANALOGUES IN CHARACTERISATION OF FLUVIAL AND FLUVIAL-LACUSTRINE DELTAIC RESERVOIRS IN THE COOPER BASIN

Abstract

Reservoir characterisation in fluvial and fluvial- lacustrine delta successions is enhanced by the use of appropriate modern and ancient analogues to understand subsurface reservoir architecture and to help build appropriately scaled reservoir models. Two case studies of reservoir characterisation in the Cooper Basin are used to illustrate the value of analogues. Firstly the Late Permian Toolachee Formation crevasse splay reservoirs of the Cooper Basin, southwest Queensland are outlined, and analogues from the Ob River in Western Siberia illustrate the relative scale of crevasse splay deposits within avulsion belts in a cool-temperate peat-forming environment. The South Blackwater coal mine in the Permian Bowen Basin is used as an analogue to quantify the 3D geometry and reservoir architecture of crevasse splays and to highlight subsurface reservoir heterogeneity.

Secondly, the Early Permian Epsilon Formation shallow water lacustrine delta reservoirs are outlined, and analogues from the extant geometry of the distributary channels and relict mouth bar deposits from the fluvial dominated Neales Delta in Lake Eyre are used to interpret flow rate decline trends and probable reservoir architecture. The subsurface Tertiary lacustrine deltaic complex of the Sirikit Field from the Phitsanulok Basin, central Thailand, is selected as an ancient analogue for the multistorey reservoirs developed within amalgamated mouth bar complexes intersected in the lower Epsilon Formation.