Method of improving the areal sweep efficiency of a steam flood oil

Abstract

A method for the recovery of oil from a subterranean, oil-containing formation by a cyclical steam flood-pressurization and production program. During the first cycle, steam is injected into the formation and oil is recovered until there is steam breakthrough at the production well. Thereafter, a pressurization cycle is initiated by throttling or shutting-in the production well while continuing injection of the steam until the bottomhole injection pressure is greater than the vertical pressure created by the overburden thereby causing the formation to fracture horizontally. After the horizontal fracture is formed, the third cycle or production cycle is initiated in which oil is recovered from the formation from either the production well or the injection well or both until the amount of oil recovered is unfavorable. Also, during the production cycle, if oil is recovered only from the injection well or the production well, steam may be injected into the nonproducing well until the amount of oil recovered is unfavorable. Thereafter, the steam flood, pressurization and production cycles may be repeated for a plurality of cycles until the production of oil is uneconomical. Optimum results of fracturing is obtained during the pressurization cycle when the bottomhole injection pressure is greater than 0.9 psi per foot of the true vertical pressure created by the overburden.