Streaming potentials and conductivities of reservoir rock cores in aqueous and non-aqueous liquids

New data relating to the electrokinetics of reservoir rock cores are reported. The data were obtained from the measurements of streaming potentials and conductivities of different sandstone core samples in aqueous and non-aqueous liquids. Zeta potentials determined by streaming potential experiments can be considerably in error as a result of surface conductivity K-S. The overall electric conductivity K-P of electrolytes inside the rock pores has been estimated from the ratio of pores' area cross-section A to length L of the effective rock core capillaries, and then this is used to correct the zeta potential values. The AIL ratio of the effective capillaries was estimated by coupling streaming current and potential measurements. Plots of the core total electric conductivity as a function of the conductivity of KCl solutions exhibit two parallel linear behaviours. In a low electrolytes region, the first slope (non-zero intercept) is proportional to the surface conductivity, whereas the second slope (zero intercept) is independent of surface conductivity as K-P becomes equal to the bulk conductivity K-L at electrolyte concentration greater than 0.6 S/m. The difference between the two slopes, in a low electrolytes region, is believed to be due to the occurrence of surface conduction behind the shear plane in consolidated rock cores. The influence of core porosity and pore pressure on streaming potentials and conductivities was also investigated. (c) 2006 Elsevier B.V. All rights reserved.