LAUSR

Abstract In this study, the physicochemical properties of a series of synthesized cationic gemini surfactants with different aliphatic carbon spacer lengths were investigated as an effective, unconventional chemical agent for practical application in enhanced oil recovery (EOR) from mature reservoirs. The self-aggregation property at low concentrations was confirmed by tensiometry measurements. Critical micelle concentration (CMC) values increased with temperature rise. Thermal stability experiments showed no surfactant degradation over a long time period. The surfactants showed good tolerance to salt addition, confirming their functionality even under high salinity conditions. Rheological studies discussing the effect of the nature of micelles on the viscosity of surfactant solutions was studied as a function of concentration and temperature. Ultralow interfacial tension (IFT) values of the order of 10–2 to 10–3 mN/m was obtained at the oil-aqueous interface. Zeta potential and contact angle measurements revealed favorable rock alteration from intermediate-wet to water-wet state by the mechanism of ion-pair interactions. Sandpack flooding studies using surfactant-polymer formulations yielded additional oil recoveries of 29.83%, 31.73%, 33.83% and 34.55% for 14-3-14, 14-4-14, 14-5-14 and 14-6-14 systems respectively.