Water injection is used for pressure maintenance of the reservoir and displacing the oil from injection towards production wells.
The water used is seawater, produced water that is reinjected or a combination of the two. In 2019, 41 fields on the NCS utilise water injection.
The Ekofisk field was originally produced with pressure depletion only and had an anticipated recovery factor of 17 percent. Subsequent water injection has contributed to a considerable increase in recovery.
Extensive water injection started in 1987, and the area with water injection was later expanded in multiple stages.
Experience has shown that the water is far more effective at displacing oil than expected, and the final recovery factor from Ekofisk is estimated at more than 50 percent.