1. n. []

In a reservoir waterflood or other fluid injection using a well pattern, the fraction of the pattern area from which reservoir fluid is displaced by the injected phase at the time of breakthrough. Parameters such as formation dip angle and dip azimuth, presence of fractures, mobility ratio, injection pattern and directional permeability affect areal displacement efficiency (EA).

Synonyms: areal sweep efficiency

See related terms: injection pattern,  vertical displacement efficiency