It is widely known that heterogeneities in oil reservoirs occurring as a result of permeability variations in the rock can have a detrimental effect on an oil recovery process; preferential diversion of injected displacement fluid occurs through the high-permeability zones, leaving the lower-permeability zones at a high residual oil content at a time when it is no longer economically viable to continue the oil recovery process. A novel oil recovery process is described which aims to improve the volumetric sweep efficiency of oil recovery. High-permeability zones are partially or completely plugged off by using the chromatographic and phase behavior of surfactants and their mixtures and the preferential invasion of high-permeability areas by low-viscosity injected fluids. The plugging will divert flow into regions of higher oil saturation. 85 refs., 46 figs., 6 tabs.