Oil recovery by waterflooding employing cross-linked polysaccharides for mobility control

摘要

A method for the recovery of oil from an oil-containing subterranean formation by waterflooding employing as an injection medium an aqueous solution of a viscosifier comprising the water-soluble reaction product of an organic polyisocyanate and the addition product of an alkylene oxide and linear, non-ionic polysaccharide, said addition product having a molecular weight of at least about 100,000. According to a preferred form of the invention, a polyisocyanate cross-linked hydroxyethyl cellulose is utilized as a viscosifier to decrease the mobility ratio between the injected water and oil, thereby improving the efficiency of the waterflood. The novel viscosifiers which comprise one form of the invention are characterized by an improved resistance to the effect of divalent metal ions present in the formation as well as a thermal stability which is superior to that of the viscosifiers currently used in waterflooding operations. Aqueous solutions of the viscosifiers of the invention are characterized by viscosities which are reversible with shear rate.