This crossplot is used to estimate the volume of clay bound water (VCBW) when other mesurements are not available (NMR, Dielectric, Elemental and XRD). An understanding of caly types within the reservoir is required.
Start by entering relative volumes of smectite, illite, chlorite and kaolinite (these inputs must sum to 1.00). The associated E value is displayed as an output and can be used in the VCBW custom equation, VCBWcustom=VCLAY/E. Next enter total clay volume and read the VCBW output value.
The theory behind this crossplot is based on Dick Merkel's presntation titled Electrical Properties of Clays. The presentation was put together for SPWLA's Nuggets of Wisdom video series and can be viewed using SPWLA's member portal.