Gas aided gravity drainage is a common oil recovery technique in anticline-shaped oil reservoirs. If the permeability is low and the reservoir is oil-wet, the remaining oil saturation can be quite high. The goal of this work is to mobilize a part of this oil by surfactant injection. Different coreflood strategies including Gas-Surfactant-Gas (GSG), Gas-Water-Surfactant-Water (GWSW), Gas-Surfactant-Water (GSW), and Gas-Surfactant-Water-Gas (GSWG) floods were investigated. GSG, GWSW and GSWG corefloods conducted in limestone cores recovered about 40-50% of the original oil in place (OOIP) due to the injection of surfactant. GSW corefloods conducted in a vuggy dolomite recovered less, about 20% OOIP incrementally. A 2D conceptual simulation model was built for an anticline reservoir for gas and surfactant solution injection. GSG flooding using wettability altering surfactant exhibited high oil recovery at the field-scale. IFT reduction, wettability alteration, and foam formation contributed to enhanced oil recovery.

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