1. n. [Enhanced Oil Recovery]
Values of interfacial tension (IFT) less than about 10-2 mN/m. Mixed surfactant systems, as used in enhanced oil recovery, adsorb at the oil/water interface and can be designed to generate an interface that is flexible and that has an ultralow IFT. Ultralow IFT implies (1) a significant increase in the capillary number for a given flow velocity and therefore that viscous forces generated during a flood can mobilize additional oil; and (2) a significant increase in the Bond number and therefore that gravitational forces (i.e., buoyancy) can mobilize additional oil. Micellar-polymer and alkaline-surfactant-polymer flooding are techniques used to achieve ultralow IFT.