Significance of Capillary Forces during Low-Rate Waterflooding

During the past decade, several experimental studies have confirmed that Smart Water injection in sandstone reservoirs could significantly improve oil recovery. Most reported enhanced oil recovery effects are described as wettability alteration creating changes in capillary forces improving the displacement efficiency. Spontaneous imbibition (SI) is one of the main recovery mechanisms in porous media, where positive capillary pressure causes brine invasion into fractional and water-wet oil-containing pores. Numerical models for fluid flow in reservoirs are based on Darcy’s law, describing the viscous forces involved, however not accounting for oil displacement by spontaneous imbibition of water. To demonstrate the importance of capillary forces in oil displacement by wettability alteration induced by Smart Water injection, a series of experimental low-rate oil recovery tests were performed. A low flooding rate was chosen to facilitate wettability alteration and allow capillary forces to contribute in the ...