Stepan Company
Surfactants for enhanced oil recovery

Abstract:

Surfactant compositions useful for oil recovery are disclosed. The compositions comprise from 10 to 80 wt. % of a propoxylated C.sub.12-C.sub.20 alcohol sulfate, from 10 to 80 wt. % of a C.sub.12-C.sub.20 internal olefin sulfonate, and from 0.1 to 10 wt. % of an ethoxylated C.sub.4-C.sub.12 alcohol sulfate. Surprisingly, including a minor proportion of the ethoxylated alcohol sulfate reduces or eliminates the need to rely on costly cosolvents for achieving good performance in enhanced oil recovery processes. In particular, low interfacial tensions and low microemulsion viscosities can be achieved when the ethoxylated alcohol sulfate accompanies the propoxylated alcohol sulfate and internal olefin sulfonate. Aqueous concentrates comprising water and the surfactant compositions described above are also disclosed. Dilution of the surfactant composition or aqueous concentrate with water or brine to the desired anionic actives level provides an injectable composition useful for EOR applications. Stable, low-viscosity oil-in-water microemulsions comprising crude oil, water, and the surfactant compositions are also disclosed.