Selective permeability reduction of oil-free zones of subterranean formations

摘要

The mobility of fluids in substantially oil-free zones of subterranean formations is controlled by introducing a composition comprising (a) water, (b) a fluid component selected from the group consisting of carbon dioxide, nitrogen, C1 to C3 hydrocarbons, and mixtures thereof, and (c) one or more polysaccharide surfactants of the formula RO(R1O)xSaccz, wherein R is a monovalent organic radical having a carbon number in the range from about 7 to 24; R1 represents a divalent hydrocarbon radical containing from about 2 to 4 carbon atoms; x is a number having an average value in the range from 0 to about 12; and Saccz represents an average number z between about 0.7 and 10 of moieties derived from reducing saccharides containing 5 or 6 carbon atoms. The resulting mixture of components (a), (b), and (c) forms a dispersion, or a "foam" as that term is commonly used in the art, which is resistant to fluid flow. In certain preferred embodiments, the invention is applied to a formation having both one or more zones of high oil saturation and one or more zones which are substantially free of oil. In such embodiments, the process accomplishes a selective reduction of the permeability of a subsequently injected oil displacement or drive fluid into and through the substantially oil-free zones, without significantly reducing mobility of the drive fluid flow into and through the zones having meaningfully high oil saturation.