| abstract |
A vertical downward gas-driven miscible blanket oil recovery process wherein the spreading rate of the solvent blanket on top of the oil column is increased by adding to or using with the conventional solvent a high density solvent such as carbon disulfide, carbon tetrachloride or certain halogenated hydrocarbons. Sufficient dense solvent is injected along with the conventional hydrocarbon solvent to increase the density of the resulting solvent mixture to a value only slightly less than the density of the formation petroleum being displaced, so that a stable blanket will be maintained with substantially increased rate and extent of spreading of the solvent blanket on top of the oil column. The miscible blanket is displaced downward by injecting gas such as natural gas, methane, or carbon dioxide into the upper portion of the reservoir. The dense solvent may be injected before or after the conventional solvent, or the dense and conventional solvent may be injected simultaneously using dual injection strings. |