1. n. [Enhanced Oil Recovery, Enhanced Oil Recovery]

A type of damage in which the formation wettability is modified, generating a change in relative permeability that eventually affects well productivity. Surfactants or other additives in drilling fluids, especially oil-base mud, or other injected fluids can change formation wettability. A naturally water-wet formation could be changed into an oil-wet formation with consequent production impairment caused by reduction of oil relative permeability. Wettability change is normally treated with mutual solvents to remove the rock-oil coating (asphaltene or paraffin precipitation), followed by a strong water-wet surfactant to reduce the tendency of further hydrocarbon precipitation.

See: drilling fluid