This crossplot is used to fit an exponential equation, Perm=10^(a*PHI-b), to estimate permeability from porosity - a permeability index. Typically discontinuous 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 a and b constants (yellow cells) until the equation ouput (red line) fits the desired data series. Once the equation is calibrated, record the a and b values and use with a continuous porosity input (a porosity input which is corrected for clay bound water is recommended).
The matrix permeability index does not include fracture permeability or permeability generated by stimulation techniques, and should only be used qualitatively.