Water chemistry with selective ionic content and composition in the injection water plays a critical role to impact on several oil recovery enhancement processes. Lower ionic strength waters with threshold salinities less than 5,000 ppm are desired for SmartWater flooding in sandstones. Low salinity water depleted in monovalents, but enriched in sulfates and divalents is suited for SmartWater flooding in carbonates. Polymer floods mandate different low salinity water lacking both monovalent and divalent ions to reduce polymer dosage and improve project economics. ASP floods require optimal salinity water without the hardness ions to enable utilization of alkali and certain temperature tolerant surfactants in the chemical formulation design. Lower salinity water is desired for carbonated water flooding to increase CO2 dissolved quantities for better incremental oil recovery. Lower salinity waters could turn out to be advantageous even for CO2 WAG where low salinity benefits outweigh the adverse CO2 solubility effects. Thermal floods require fresh and hardness free water to generate the steam using boilers.
Injection waters of optimized salinity, ionic content and composition not only work on their own, but can also synergistically combine with other EOR processes to result in higher incremental oil recoveries. Lower salinity waters have a beneficial effect in polymer, surfactant, dilute surfactant and carbonated water floods to yield better oil recoveries when compared to high salinity water. In this paper we first provide an overview on the benefits of tuning injection water salinity and composition in different IOR/EOR processes with selected examples and then propose a unique set of injection water chemistry requirement guidelines for IOR/EOR. The study findings also point out the need to develop “water chemistry” as a specialty discipline within EOR portfolio and advocate for better integration of this area with other key surface and subsurface related disciplines to effectively improve upon IOR/EOR upstream value chain.