Measurement of streaming potential coupling coefficient in sandstones saturated with high salinity NaCl brine

We present measurements of the streaming potential coupling coefficient in intact sandstone samples saturated with NaCl brines at concentrations up to 5.5 molL^-1. The values we record at low salinity are consistent with those reported previously. As brine salinity increases, the coupling coefficient decreases in magnitude, but is still measureable up to the saturated concentration limit. The magnitude of the zeta potential also decreases with increasing salinity, but approaches a constant value at high salinity. This behaviour is not captured by current models of the electrical double layer. Our results suggest that streaming potential measurements may be used to monitor flow in saline subsurface environments such as deep saline aquifers and hydrocarbon reservoirs. However, they were obtained at laboratory temperature. Future work will focus on the effect of elevated temperatures at high salinity.