Source: Coates, G., 1992, Core data and the MRIL show a new approach to formation factor: SPWLA Transactions.
The Lower Frio Sandstone is examined using a PfEFFER analysis from the same article as Example #1. The zone has a MBVI of 14% at the top of the section, decreasing to about 7% at the base. The MPHI (effective porosity) is fairly constant at about 30%. The interval is interpreted as wet.
PfEFFER was used to create Pickett cross plots with points
annotated in color with depth, gamma ray, and MBVI. The BVW is
about 20% at the top, decreasing to a minimum of 8% at the base
and Sw ranges between 70 and 90%. Both PfEFFER analysis and the
interpretation of the MRIL data indicate that this sandstone is
wet.