Effects of Clay Minerals and Pore-Water Conductivity on Saturation Exponent of Clay- Bearing Sandstones Based on Digital Rock

The calculation of water saturation from resistivity logs relies on the saturation exponent of Archie’s equation. The accurate determinations of the water saturation in clay-bearing sand reservoirs have been found to be very complicated due to the additional conductivity of the clay minerals, which tend to increase with the increase of porewater conductivity in a nonlinear relationship. Therefore, the aim of this study is to investigate the effects of porewater conductivity and clay minerals on the saturation exponent in different water saturation ranges. A number of digital rock analyses on clay-bearing sandstone were performed in this study using the finite element method. The results indicated that the I-Sw relationship was generally a nonlinear relationship, which changed with the water saturation on a log-log plot. It was observed that the clay volume fractions, as well as the clay minerals in which the conductivity varied with the pore-water conductivity, had displayed significant effects on the saturation exponent.