Injection Water Chemistry Requirement Guidelines for IOR/EOR

AbstractWater chemistry with selective ionic content and composition in the injection water plays a critical role to impact on several oil recovery enhancement processes. Low ionic strength waters with threshold salinities lower than 5,000 ppm are desired for SmartWater flooding in sandstones. Low to moderate salinity waters depleted in monovalents, but enriched in sulfates and divalents are 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 a boon for even CO2 WAG where low salinity benefits outweigh the adverse CO2 solubility effects. Thermal floods require fresh and hardness free water to generate steam as injectant 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 from published data and then propose a unique set of injection water chemistry requirement guidelines for IOR/EOR. The present 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 emerging focus area with other key surface and subsurface related disciplines to effectively improve upon IOR/EOR upstream value chain.