This crossplot is used to fit Lucia's permeability equation by adjusting the rock fabric number input. Typically core data are used.
Start by inputting porosity-permeability data series, (green, blue and orange cells). Each data series allows an unlimited number of rows, and cut and paste functionality is available. Next, adjust the rock fabric number input until the equation ouput (red line) matches the data. K-PHI parameter inputs (a0, a1, b0 and b1) can also be adjusted, but generally the default values should be used. Once the equation is calibrated, record the RF number value and use with a continuous interpartical porosity input (sonic porosity should be used if micro porosity is present).
Jennings, James W., and Lucia, Jerry F., “Predicting Permeability From Well Logs In Carbonates With A Link To Geology For Interwell Permeability Mapping.” SPE Reservoir Evaluation & Engineering August 2003: 215-225.