Dynamic Interactions of Water Ions at Carbonate/Brine Interfaces: Electrokinetic Studies II

In carbonates, dissolved ions in the injection water play a key role on altering rock-fluid interactions and influencing rock wettability. Emphasis in this study is given to the direct measurements of carbonates zeta potential at different ionic compositions and reaction times. A disturbance at interfaces was observed for all the brine recipes within the first hour of interactions. The zeta potential became steady with time as a result of attaining an initial chemical equilibrium at interfaces. Individual ions altered carbonate zeta potential and interacted differently at interfaces, in spite of having an identical salinity. The hardness ions reversed the zeta potential of carbonate particles towards the positive side. The electrical properties were found to be affected by the ionic content, ions ratio in the injection water. Additionally the dissolved divalent cations can play a role in the interactions at the Stern layer boundary, which can eventually impact the zeta potential at interfaces. In view of these zeta potential results, only SmartWater, and other salt solutions were able to create electrical repulsions between oil/water and carbonate particles/water interfaces. As a result, wettability of the rock will be altered to water-wet and therefore can enhance the oil recovery in carbonate reservoirs.