Stress Dependence of Sandstone Electrical Properties and Deviations From Archie’s Law

The resistivity index (RI) of Fontainebleau and Bentheimer sandstones was investigated at ambient and reservoir pressures down to low water saturations. The RI measurements show that both sandstones display Archie behavior at elevated pressure. However, at ambient pressure, the RI for Fontainebleau sandstone deviates from Archie behavior at low water saturations. The pore-space images suggest that the deviation from Archie behavior is attributable to the presence of conductive percolating grain-contact regions.

Introduction

Deviations from Archie’s law are known to occur, particularly at low water saturations, even for clean sandstones.