Comparative study of resistivity models and waxman smits model in cooper basin south australia-murteree shale: Case study

Murteree organic shale are one of most rich unconventional gas reservoirs in Cooper Basin, South Australia. In shale gas reservoirs, estimation of water saturation and porosity are very erroneous when calculated from the well logs. In Roseneath and Murteree shales of Copper Basin in South Australia, we investigated their fluids contents using Archie model, Simandoux, Indonesian and Dual water model. Later, brine estimation fromWaxman-Smits was correlated with Archie, Simandox, Indonesian and Dual water model results. Due to presence of high amount of clay minerals, conductivity and clay bound water are very high, the changes in salinity level of the brine due to post depositional features, followed by physical and chemical changes effect the determination of water saturation consequently. High clay volume in shale gas reservoirs cause over estimation of water saturation when determined by Archie and other resistivity models. Waxmans-Smiths equation gives more reliable results because it accounts the cation exchange capacity and conductance of clay minerals present in the formation. Also it is noticed that as the clay mineralogy percentage, clay bound water also increases with same pattern respectively. In this paper, description of Waxmans-smith equation in determination of water saturation has been presented and also relation between clay minerals and clay bound water has been discussed. Form our analysis, it has been estimated that, Waxmans-Smit conductivity model gives estimation of water more reliable as compare to resistivity models like Archie, Simandoux and Indonesian in unconventional shale gas reservoir. Hydrocarbon potential are present with respect to water saturation and resistivity logs. © 2023 The Authors.