Interactions between rock/brine and oil/brine interfaces within thin brine film wetting carbonates: a molecular dynamics simulation study

The thin brine film that wets rock surfaces governs the wettability of underground reservoirs. The ionic composition and salinity of this nanosized brine film influence the wetting preference of the rock pore space occupied by hydrocarbons. Despite numerous investigations over the last decades, a unanimous fundamental understanding that concerns the contribution of ions in the original wetting state of the reservoir is lacking and hence the mechanisms responsible for the wettability reversal of the mineral are still unclear. This wettability reversal is the main consequence of ion-tuned waterflooding. Although the method is widely accepted in practice, there is no universal consensus on the underlying mechanisms involved. Molecular dynamics simulation is an excellent choice to remove such ambiguities. This method can capture an atomic-level picture of the phenomena that affect reservoir wettability upon injecting low-salinity water. For the purpose, we performed simulations of brine films confined between...