The presence of shale in reservoir does not only effect the porosities. It will also influence the resistivity of the reservoir. Its resistivity will be controlled by free and bound formation water, and it will increase the conductivity. This conductivity excess can be evaluated by the value of Cation Exchange Capacity (CEC). CEC is a key parameter in resistivity-based water saturation models of shaly sand reservoirs.
Analysis of CEC of clay minerals in shale will help us to calculate more accurate value of Sw. This presentation also explores the characterization of petrophysical parameters such as shale volume, effective porosity, formation water and matrix resistivity, and free water saturation as well as bound water saturation.