Design of injected water salinity for enhanced oil recovery applications in sandstone reservoirs using coupled flow-geochemical simulation

Abstract

Many previous studies have highlighted the effect of injected fluid salinity on recovery performance and effluent analysis in sandstone reservoirs. However, the complex interactions between the oil, original formation water, injected water, and rocks make capturing all the relevant mechanisms difficult. This paper presents a simulation study where complex mechanisms and interactions are represented, including multiple ion exchange, mineral dissolution, wettability alteration, pH variation, and electrical double layers. The models are used to examine how the salinity of injected water may affect oil recovery and compositions of the effluent fluids. The results show that the wettability changes caused by ion exchange and mineral dissolution/precipitation reactions may strongly affect the recovery performance of low-salinity water injection. In contrast, mineral dissolution/precipitation effects are less significant for high-salinity water injection. In addition, the complex interactions between these processes also affect the pH in the effluent (producing) streams.