In this study,the displacement mechanisms of alkaline flooding in enhanced heavy oil recovery(EOR) are investigated by using a micromodel.It has been observed that two mechanisms govern the EOR process.One is a novel mechanism ─ in situ water-in-oil (W/O) emulsion and partial wettability alteration.The W/O emulsion formed in the injection of alkaline solution blocks the high permeability zone and the pore walls are altered to partially oil-wet,leading to an increase in pressure drop and high tertiary oil recovery.The other mechanism is formation of an oil-in-water(O/W) emulsion.Heavy oil is emulsified in brine by an alkaline plus very dilute surfactant formula and then entrained in the water phase and produced out of the model.
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