Parameters affecting bulk resistivity in Athabasca sandstone


Mr Tom Kotzer ( - Cameco Corporation), Mr Clint Keller ( - Cameco Corporation)

Cameco Exploration uses surface DC resistivity techniques in the Athabasca Basin, northern Saskatchewan, as a proxy for fluid-rock interaction to highlight favourable exploration targets related to uranium mineralization. In this study, bulk rock resistivity and fluid resistivity were compared with intensity of clay alteration in rocks of the Athabasca Basin to verify the validity of applying Archie’s Law to resistive sandstones. When analyzed it was shown that Archie’s Law is not an applicable model for determining the resistivity of the Athabasca Group sandstone. A major factor driving bulk resistivity is total clay content, where an increase in clay content results in a decrease in bulk resistivity. Fluid chemistry was also compared with bulk resistivity, and it was shown that fluid resistivity has less impact on bulk rock resistivity compared to clay content, until relatively high salinity fluids are introduced into the rock. Overall this study has provided empirical and fundamental insights into the dominant parameters affecting the transmission of electrical currents into resistive sandstone rocks and reaffirmed that bulk rock resistivity is a valuable tool for delineating areas of fluid-rock interaction and favorable exploration targets.