Evaluation of the Carynginia formation as a potential gas shale reservoir at Perth Basin, Western Australia

There are several formations that have been considered to be potential gas shale at the Perth Basin. The early Permian Carynginia formation that extensively covers Perth Basin and has formed under restricted circulation is an overmature and gas-prone formation in most of the studied areas. Geochemical analysis showed high TOC values at the basal marine shales of the formation which makes the formation suitable for being a shale gas reservoir. Tectonically, the formation is deposited within a north-west inclining trough across the basin, and is formed by marine transgression during the Late Artinskian. To study the lateral variation of Carynginia formation, it is very important to define various members within this formation and examine their changes over the study area. Considering that shale sections suffer from high heterogeneity in small-scale observations, it is necessary to determine shale's rock types and their depositional environment based on stratigraphic context, rock composition and texture. The lateral variations in terms of thickness, brittleness, and lithofacies as well as geochemical parameters which can express the potential of shale gas within the formation throughout the basin have been studied. General trend of these changes in the depositional environment are detected in this study by mapping Carynginia formation in different wells, highlighting various members and correlating identified rock types in shale section of the formation. Lateral correlation shows a good match with lithological variability of intervals and the environment changes within shale layers which is controlled with changes in their constituent rock types.