Well log data analysis and interpretation on the pre-Carboniferous succession in Waukarlycarly 1, Canning Basin, Western Australia

Waukarlycarly 1 is a stratigraphic well drilled in the southern part of the Canning Basin’s Waukarlycarly Embayment under Geoscience Australia’s Exploring for the Future program in collaboration with the Geological Survey of Western Australia to provide stratigraphic data for this poorly understood tectonic component. The well intersects a thin Cenozoic section, overlying Permian–Carboniferous fluvial clastics and glacial diamictites, with a thick pre-Carboniferous succession (855–2585 mRT) unconformably overlying the Neoproterozoic metasediments. Three informal siliciclastic intervals were defined based on the data from core lithology, well logs, fluid inclusions, chemical and mineral compositions; an Upper Sandstone (855–1348.1 mRT), a Middle Interval (1348.1–2443.4 mRT) and a Lower Sandstone (2443.4 –2585 mRT). The Middle Interval was further divided into six internal zones. Conventional methods were applied to interpret effective porosity, water saturation and elastic properties (Poisson’s ratio and Young’s modulus). Artificial neural network technology was employed on well logs to interpret the total organic carbon (TOC) content, pyrolysis products from the cracking of organic matter (S2), permeability, and mineral compositions. In the Upper Sandstone, average sandstone porosity and permeability are 17.9% and 464.5 mD and, 6.75 % and 10 mD in the Lower Sandstone. The Middle Interval claystone has an average porosity and permeability of 4.17 % and 0.006 mD, and average TOC content and S2 of 0.17 wt% and 0.047 mg HC/g rock with maximum values of 0.66 wt% and 0.46 mg HC/g rock. Average Poisson’s ratio and Young’s modulus of the claystone are 0.154 and 9.81 GPa. Correlations of mineral compositions, petrophysical, geomechanical and geochemical properties of the Middle Interval have been conducted. Young’s modulus and Poisson’s ratio are well correlated with the contents of key minerals, including Quartz, carbonates and TotalClay. Although TOC content is low at Waukarlycarly 1, hydrocarbon generation and migration have occurred elsewhere in the Waukarlycarly Embayment. The helium response just above the Neoproterozoic basement in the FIS profile is not associated with the hydrocarbon responses implying that these fluids have different sources.