Review and experimental studies to evaluate the impact of salinity and wettability on oil recovery efficiency

Abstract

Oil recovery efficiency is influenced by a myriad of interacting variables such as pore geometry, wettability, rock mineralogy, brine salinity, oil composition, etc. Reservoir wettability is known to have very significant influence on pore scale displacement and hence is a strong determinant of the final residual oil saturation. Recent studies have indicated the improved oil recovery potential of low salinity brine injection. Though the reason for this reported increase is still unclear, it is speculated that it may be due to wettability changes. In this work, coreflood studies were carried out to determine the recovery benefits of low salinity waterflood over high salinity waterflood and the role of wettability in any observed recovery benefit. Two sets of coreflood experiments were conducted; the first set examined the EOR potential of low salinity floods in tertiary oil recovery processes while the second set examined the secondary oil recovery potential of low salinity floods. Changes in residual oil saturation with variation in wettability and brine salinity were monitored. All the coreflood tests consistently showed an increase in produced oil and water-wetness with decrease in brine salinity and increase in brine temperature.