Selection of the Right Demulsifier for Chemical Enhanced Oil Recovery

Abstract

Abstract In this paper, the importance of five process variables (alkaline, surfactant, polymer, shear rate and oil cut) and their interactions that govern emulsion stability in chemical enhanced oil recovery (CEOR) was investigated. The surfactant, alkaline, and polymer decreased the size of oil droplets, increased the surface charge of oil droplets, and increased the film elasticity, making oil-water separation difficult. Selected cationic demulsifiers (patents pending) when added to a produced emulsion at ambient temperature for alkaline, surfactant, polymer (ASP) and surfactant, polymer (SP) processes yielded oil and water phases with greatly improved quality compared to emulsions treated with conventional nonionic demulsifier resins and polymeric cationic flocculants. Structure and performance relationships of alkyltrimethylammonium bromides and alkyldimethylbenzylammonium bromides (n=C8 to C18) were also studied. Octyltrimethylammonium bromide was the best demulsifier for SP flood and dodecyldimethylbenzylammonium bromide was the most effective for ASP flood. Di-alkyl quaternary ammonium bromides were more effective than mono-alkyl quaternary ammonium bromides of similar molecular weights. The zeta potential became less negative and the size of oil droplets remarkably increased when a cationic demulsifier was added to the emulsion. Application of this novel demulsifier resulted in the production of dry oil and clean water for a pilot field experiencing chemical breakthrough from an ASP flood