Determination of water saturation in shaly petroleum reservoirs is a challenging task that has a significant impact on total gas in place estimations. The early Permian Murteree shale is one of the unconventional gas reservoirs in the Cooper Basin, South Australia. The cumulative effect and interaction of rocks, minerals, fluids and organic content of this formation has not been investigated and incorporated when using Archie�s equation or other resistivity models for water saturation estimation. The Murteree shale has conductive brine, natural gas and highly resistant organic matter kerogen adsorbed on clays platelets. No comprehensive investigation has been performed on the overall impact of these resistive and conductive phases on the estimated brine saturation in resistivity models. This study focuses on the calculation of the most important properties of this shaly formation including clay content, porosity and mineralogy using different techniques including FIBSEM, QEMSCAN and wireline-based log data. The wireline logs have been compared and calibrated with FIB/SEM images, QEMSCAN, XRD and found that shale content in Murteree Formation is around 50. Similarly using Wyllie formula for sonic porosity with Hilchie's correction factor, the porosity was also determined close to 2. In addition, only the Indonesian and Simandoux model resulted significant saturation values while the others resulted insignificant values. © 2022 American Institute of Physics Inc.. All rights reserved.