This crossplot is used to determine shale resistivity.
Start by inputting resistivity-volume shale 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 shale resistivity until the shale line fits the desired data series. Although slope (m) can be adjusted, it should generally equal 1.00 (acts like a fracture in an Archie rock). Once you have a match, record the shale resistivity value for petrophysical analysis work.
The theory behind this crossplot is based on Dick Merkel's presentation 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.