Summary Scientific understanding of how the molecular structures of surfactants and cosolvents affect microemulsion properties greatly speeds up the process of arriving at optimal chemical formulations for enhanced recovery of a specific crude oil. With the main emphasis on reducing the chemical cost of the formulations, novel surfactants and cosolvents have been developed and shown to have superior performance. We have synthesized and tested surfactants with different hydrophobe sizes and structures varying from ultrashort to large to satisfy a variety of crude-oil requirements over a wide range of reservoir conditions. The cosolvents and surfactants with ultrashort hydrophobes offer advantages such as short equilibration time for the microemulsion formation and lower microemulsion viscosity. Chemical formulations developed using these chemicals have shown excellent performance with very low cosolvent and surfactant retention in cores. Low retention means less chemicals can be used to recover each barrel of oil from the reservoir. These chemicals can be made commercially at low cost. Through use of these new developments, the chemical cost per barrel of oil is low enough to be economically viable, even at low crude-oil prices.

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