CO 2 ‐Switchable Oil/Water Emulsion for Pipeline Transport of Heavy Oil

By mixing an aqueous solution of tertiary amine, N , N ‐dimethylethanolamine (DMEA), with naphthenic acid (RCOOH) derived from heavy oil, a CO 2 switchable zwitterionic surfactant (RCOO − DMEAH + ) aqueous system was constructed. The CO 2 switchability of this zwitterionic surfactant was confirmed by visual inspection, pH measurements, and conductivity tests, i.e., the RCOO − DMEAH + decomposed into RCOOH, DMEAH + and HCO 3 − after bubbling CO 2 through but switched back to its original state by subsequent bubbling N 2 through at 80 °C to remove the CO 2 . The interfacial tension tests of heavy oil in DMEA aqueous solutions indicated that the solution containing 0.5 wt% of DMEA and 0.2 wt% of NaCl resulted in the lowest interfacial tension. The O/W emulsion formed when aqueous solutions of DMEA were used to emulsify heavy oil exhibited the best performance when the oil/water volume ratio, DMEA concentration, and NaCl concentration were 65:35, 0.5 and 0.2 wt%, respectively. The feasibility of pipeline transport of the O/W heavy oil emulsion was evaluated. The results illustrated that the demulsification of the O/W emulsion after transport could be easily realized by bubbling CO 2 through. Although demulsification efficiency still needs to be improved, the recycling of the aqueous phase after demulsification by removal of CO 2 looks promising.