An integrated petrophysical analysis to evaluate sequence stratigraphy of the Winduck Interval in the Neckarboo Sub-basin, Darling Basin, NSW

The latest Silurian to Early Devonian Winduck Interval of the extensive but poorly exposed Neckarboo Sub-basin, consists of several thousands of metres of a quartzose siliciclastic sandstone succession that has been divided into three sequence divisions called (in ascending parasequence order) parasequence A (coarse-grained quartz sandstone), parasequence B (fining-upward succession of sandstone with siltstone and sandstone beds thicken upward) and parasequence C (coarse-grained quartz sandstone with siltstone and interbedded calcareous sandstones). These three geophysically defined parasequences are separated by slightly discordant erosion surfaces. The erosion surfaces are characterised by abrupt breaks at the top of parasequences A and B and the surface at the top of parasequence B represents relatively local erosion. The top of parasequence C is marked by a major unconformity with the Snake Cave Interval. Gamma ray and self-potential signatures within the parasequences can be correlated throughout the Neckarboo Sub-basin. The three sequence divisions are further subdivided into depositional parasequences, which are readily recognised from core sedimentology and electrofacies analysis. The parasequences provide the framework for a detailed sedimentological analysis, which focuses on the identification of lithofacies successions and parasequences. Petrophysical data are recorded and their relationships to the depositional parasequences are discussed. This paper presents a predictive reservoir effectiveness model that has been developed to aid exploration of the Winduck Interval. The aim is to find the distribution of parasequences (based on variations in porosity, net effective thickness and lithofacies with burial depth) and to provide a dataset for lithostratigraphic units within the Winduck Interval and parameter input for exploration prospect evaluation. Parasequence stratigraphic analyses were obtained where there is good lithofacies control. The porosity and permeability results have been analyzed in a number of parasequences and poor reservoir quality may be due to the effects of structure and fluid flow. This approach provides for better and more precise stratigraphic trap analysis.