Chemical methods focus mainly on alkaline-surfactant-polymer (ASP) processes that involve the injection of micellar-polymers into the reservoir. Chemical flooding reduces the interfacial tension between the in-place crude oil and the injected water, allowing the oil to be produced. Micellar fluids are composed largely of surfactants mixed with water. Goals of polymer floods are to shut off excess water in producing wells, and to improve sweep efficiency to produce more oil. Chemical field trials by industry indicate that surfactants can recover up to an additional 28% of reservoir oil; however the economics have not been favorable when the price of oil is factored against the cost of surfactants and polymers. Chemical flooding technologies are subdivided into alkaline-surfactant-polymer processes, polymer flooding, profile modification, and water shut off methods.
NETL research in chemical EOR focuses to a great degree on the application of surfactants, which act as a “detergent” to loosen oil from a reservoir rock. The photos above depict a lack of oil displacement from a formation core sample placed in formation brine (left) and successful displacement of oil when the core sample is placed in an alkaline surfactant solution (right). This work is featured in the fact sheet Surfactant-Based Enhanced Oil Recovery Processes and Foam Mobility Control, Project No. DE-FC26-03NT15406.