Recent advances in surfactant EOR are reviewed. The addition of alkali to surfactant flooding in the 1980s reduced the amount of surfactant required and the process became know as alkaline surfactant polymer flooding. It was found that the adsorption of anionic surfactants on calcite and dolomite can be significantly reduced with use of sodium carbonate as the alkali, thus making the process applicable for carbonate formations. This system is also capable of altering the wettability of calcite from strongly oil-wet to preferentially water-wet. This wettability alteration in combination with ultra-low interfacial tension (IFT) makes it possible to displace oil from preferentially oil-wet carbonate matrix by oil-water gravity drainage.

The alkaline surfactant process generates surfactants (soap) in situ by reaction between the alkali and the naphthenic acids in the crude oil. The in situ ratio of the soap/surfactant determines the local optimal salinity for minimum IFT. Recognition of this dependence makes it possible to design a strategy to maximize oil recovery with the least amount of surfactant. An additional benefit of the presence of the soap component is that it generates an oil-rich colloidal dispersion that makes it possible to have ultra-low IFT over a much wider range of salinity than in its absence.

It was once thought that alcohol was necessary to have microemulsion without gel-like phase or polymer-rich phase separating from the surfactant solution. It was found (for one system) that by blending dissimilar surfactants, the single phase region with NaCl or CaCl2 is greater for the blend than either surfactant alone. This is an alternative to use of alcohol.

Foam can be used for mobility control by alternating slugs of gas with slugs of surfactant solution. Besides effective oil displacement in 1-D, it demonstrated greatly improved sweep in a layered, 2-D sandpack.