A comprehensive review of low salinity/engineered water injections and their applications in sandstone and carbonate rocks

The low salinity/engineered water injection techniques (LSWI/EWI) have become one of the most important research topics in the oil industry because of their possible advantages for improving oil recovery compared to conventional seawater injection. Researchers have proposed several mechanisms for the LSWI/EWI process in the literature; however, there is no consensus on a single main mechanism for the low salinity effect on oil recovery. Because of the latter, there are few models for LSWI/EWI and especially for carbonates due to their heterogeneity and complexity. In this paper, we present a comprehensive state-of-the-art review on low salinity/engineered water injection for both sandstones and carbonates. This review includes descriptions of underlying mechanisms, spontaneous imbibition and coreflood laboratory work, field-scale pilots, numerical and modeling work, implementation, comparison between sandstones and carbonates, other LSWI/EWI applications, and desalination methods. List of recommendations and conclusions are provided based on this vast literature review and our experiences. This paper can be used as a guide for starting or implementing laboratory- and field-scale projects on low salinity/engineered water injections.