Study on the variation of dynamic interfacial tension in the process of alkaline flooding for heavy oil

► The variation of dynamic IFT in process of alkaline flood for heavy oil was studied. ► The heavy oil pre-equilibrated by NaOH solution loses the interfacial activity. ► There is still interfacial activity in heavy oil pre-equilibrated by Na2CO3 solution. ► Interfacial reaction has more effect on interfacial property of oil with low TAN. ► The equilibrated alkaline solutions can reduce IFT to ultralow for oil with high TAN.