This crossplot is used to graphically determine a cementaion exponent (m) value for a set of core data representing a particular rock type.
Formation factor (FF) is measured in the lab and is equal to the ratio of the 100% water saturated rock to the resistivity of the water with which it is saturated. Formation factor can also be determined with the equation FF=a/PHI^m, where the slope equals cementation exponent (m) and the intercept at PHI=1.00 is equal to the tortuosity exponent (a).
Start by inputting porosity-FF 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 cementation exponent value untill the line fits the desired data series. The tortuosity exponent input is often pinned at 1.00 for core work.