1. n. [Enhanced Oil Recovery]

In a displacement process, the ratio of the cumulative height of the vertical sections of the pay zone that are contacted by injection fluid to the total vertical pay zone height. Vertical displacement efficiency (EI) strongly depends on parameters such as mobility ratio and total volume of fluid injected. Nonuniform permeability may cause an irregular front that affects the vertical displacement efficiency because the injected fluid flows faster in high-permeability zones than in low-permeability zones.

Synonyms: vertical sweep efficiency

See related terms: areal displacement efficiency