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

• 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
• 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.

See: alkaline-surfactant-polymer flooding,  interfacial tension,  micellar-polymer flooding