Identification and Evaluation of High-Performance EOR Surfactants

Summary We report results for a number of promising enhanced-oil-recovery (EOR) surfactants based upon a fast, low-cost laboratory screening process that is highly effective in selecting the best surfactants to use with different crude oils. Initial selection of surfactants is based upon desirable surfactant structure. Phase-behavior screening helps to quickly identify favorable surfactant formulations. Salinity scans are conducted to observe equilibration times, microemulsion viscosity, oil- and water-solubilization ratios, and interfacial tension (IFT). Cosurfactants and cosolvents are included to minimize gels, liquid crystals, and macroemulsions and to promote rapid equilibration to low-viscosity micro-emulsions. Branched alcohol propoxy sulfates (APS), internal olefin sulfonates, and branched alpha olefin sulfonates (AOS) have been identified as good EOR surfactants using this screening process. These surfactants are available at a low cost and are compatible with both polymers and alkali, such as sodium carbonate and, thus, are good candidates for both surfactant-polymer and alkali-surfactant-polymer EOR processes. One of the best formulations was tested in both sandstone and dolomite cores and found to give excellent oil recovery and low surfactant retention with a west Texas (WT) crude oil.