Oil recovery process utilizing gravitational forces

摘要

There is disclosed a method of recovering oil from a subterranean oil formation having the vertical thickness of 40 ft or more. The method exploits the effect of gravity on the various slugs of diverse materials injected into the oil column of the formation. The method comprises injecting a surfactant slug into the lower 50-75% of the vertical thickness of the oil column, then injecting a slug of a mobility control polymer into the upper 50-75% portion of the thickness of the oil column, followed by the injection of a slug of a drive fluid over substantially the entire vertical thickness of the oil formation. Optionally, a low-salinity pre-flush slug may be injected to reduce contact of high salinity water with the surfactant slug, and an alkaline pre-treat solution may be injected to precipitate divalent cations prior to the injection of the surfactant slug.