This study reports measurements of the zeta potential of intact carbonate samples obtained using the streaming potential method. This method allows us to directly link zeta potential and oil recovery in the same coreflooding experiments. We use single-phase (brine only) and multiphase (brine displacing oil) experiments to determine the correlation between injection brine composition, zeta potential, and oil recovery. We find that typical formation brine yields a positive zeta potential, whilst seawater yields a negative zeta potential. This affects fluid-rock interactions which in turn affects oil recovery. Dilution of injected seawater and an increase in SO4 2- concentration both yield a more negative zeta potential compared to the seawater reference case. The magnitude of the zeta potential increases in the presence of an oil phase after aging and similar increase was observed on diluting the injection brine. In the experiments reported here, incremental oil production was not observed. Incremental oil production was also not observed. We suggest that the increase in the zeta potential, and consequent increase in the electrostatic repulsion between the similarly charged mineral-brine and oil-brine interfaces, explains why most of the oil is produced during first brine injection.

This study reports measurements of the zeta potential of intact carbonate samples obtained using the streaming potential method. This method allows us to directly link zeta potential and oil recovery in the same coreflooding experiments. We use single-phase (brine only) and multiphase (brine di...