Abstract: A method for the enhanced recovery of oil from subterranean reservoirs having connate water containing dissolved divalent metal cations wherein there is injected via an injection well a slug of an aqueous solution containing a water-soluble alkaline material and an aminopolycarboxylic acid or a salt thereof as a chelating agent followed by an aqueous drive fluid while producing fluids from the reservoir via a production well.

Abstract: An enhanced oil recovery process employing an aqueous alkyl polyethylene oxide sulfate solution and a carbon dioxide displacement fluid at injection pressures above about 1,500 p.s.i. The aqueous solution of an alkyl polyethylene oxide sulfate having 8 or 9 carbon atoms in the alkyl group and between 1 and 5 ethoxy groups significantly improves the areal sweep and overall efficiencies of dense fluid carbon dioxide enhanced oil recovery processes, especially under high salinity and low pH conditions. The efficiency of the process is increased as the injection pressure is increased.

Abstract: A composition and method for enhanced oil recovery utilizing an aqueous displacement fluid containing or contaminated by brine and containing a polyacrylamide or polyacrylamide derivative as a thickener and "OK Liquid" detergent.