Abstract: This invention relates to enhanced oil recovery (EOR) techniques for improving the production economies and recovery efficiency of hydrocarbons from a reservoir after primary depletion has occurred. The reservoir has at least two production strata. At least one production well capable of producing fluids from both strata is placed into the reservoir. At least one injection well capable of injecting fluid into both strata is placed in the reservoir. At least one combination production/injection well for producing well fluid from only one of the strata is placed into the reservoir. The produced well fluid is separated into a mostly hydrocarbon component and a mostly water component in place downhole and reinjecting into the other of said strata the mostly water component by use of the combination production/injection well.