Correlation and sequence stratigraphic interpretation of the lithostratigraphic Snake Cave Interval: Implications for hydrocarbon reservoir prospectivity between the southeast Blantyre and northwestern Neckarboo Sub-basins, Darling Basin, southeastern Australia

Abstract

Correlation and sequence stratigraphic interpretation was conducted on the upper Lower through upper Middle Devonian sandstones of the Snake Cave Interval succession between the southeast Blantyre and northwestern Neckarboo sub-basins across the central Darling Basin. This article necessitated the definition and use of many sedimentary lithotypes related to different facies associations and depositional environment criteria for the purpose of establishing the sequence stratigraphy to aid hydrocarbon exploration of the studied areas. The data set used a combination of wireline logs, core/cutting data and analysis of the paleo-environments of sedimentary facies from three wells. The sedimentological analysis showed that the Snake Cave Interval section presents three different facies associations, which are visible in both vertical and lateral successions, and are characterised as: meandering and braided fluvial facies associations with minor fluvio-shallow lacustrine complex facies associations. The Snake Cave Interval section in the studied areas is consistently defined by six third-order depositional sequences informally named SCS1, SCS2, SCS3, SCS4, SCS5 and SCS6 in the Nyngynderry-1 and Mount Emu-1 exploration wells, and the Kewell East-1 stratigraphic well. All the stratal patterns in the internal sequence stratigraphic units are asymmetric and marked by lowstand, transgressive and highstand systems tracts separated by sequence boundaries, maximum flooding surfaces and transgression surfaces with unique gamma-ray log response characteristics calibrated by particular lithologic aspects. These are all incorporated within the sequence stratigraphic approach to hydrocarbon reservoir prediction. The stratigraphic architecture of the third-order depositional sequences presented here in our study has implications for the hydrocarbon potential of sandstone reservoirs in the southeastern Darling Basin including the Snake Cave Interval succession targets.