Kansas Geological Survey
Open-file Report 2003-31

Calculator for Wellington West

To facilitate simulator modification and history matching an Excel worksheet was constructed that contained all relevant equations linked to porosity and/or permeability. With this worksheet, if the simulator required an adjustment of the permeability, the corresponding capillary pressure and relative permeability properties could be calculated and input. This kept all petrophysical properties “coupled.” This worksheet also provided easy changes to relative permeability and immediate feed-back of the effect of a change on flow at a given saturation.

Archie Cementation Exponent

Traditional wireline log calculation of saturations use the Archie equation and cementation (m) and saturation exponent (n) values of 2. Formation resistivity factors (Ro/Rw) measured at Rw=0.045 ohm-m (Figure) indicate that the Archie cementation exponent (assuming an Archie intercept of 1.0) averages m=1.97+0.09 for all facies. Echinoderm-rich facies can exhibit cementation exponents between 2.0 and 2.1. Vuggy cherts can exhibit cementation exponents between 2.1 and 2.2.

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Last updated July 2003