Electrokinetics of Carbonate/Brine Interface in Low-Salinity Waterflooding: Effect of Brine Salinity, Composition, Rock Type, and pH on ?-Potential and a Surface-Complexation Model

A comparative study of carbonate rocks reveals that surface charge behavior is consistent across different rock types, with ζ-potential becoming more negative as brine salinity decreases. This finding suggests that low-salinity waterflooding can alter wettability in carbonate reservoirs, reducing oil-wetting tendencies. The research used Iceland spar calcite and three reservoir-related rocks—Middle Eastern limestone, Stevns Klint chalk, and Silurian dolomite—to measure ζ-potential across a range of salinities, brine compositions, and pH values. A new surface-complexation model (SCM) was developed to explain the observed increase in ζ-potential with pH, highlighting the influence of surface species like >CaSO4−, >CO3Ca+, and >CO3Mg+. Notably, chalk particles exhibited the most negative surface charges and highest reactivity to changes in pH and salinity, while dolomite showed the least.

Mahani, H., Keya, A. L., Berg, S., & Nasralla, R. (2016). Electrokinetics of Carbonate/Brine Interface in Low-Salinity Waterflooding: Effect of Brine Salinity, Composition, Rock Type, and pH on ?-Potential and a Surface-Complexation Model. SPE Journal, 22(01), 53–68. https://doi.org/10.2118/181745-pa