Separation of Water from High pH Water-in-Heavy Oil Emulsions Using Low Pressure CO2

In this study, a demulsification treatment process for high pH water-in-oil (W/O) emulsions, using low pressure CO2 and demulsifier, with optimized temperature and mixing time is designed. The efficacy of different acids, including Ha and CH3COOH, are also examined using this method, to be compared with the results obtained with CO2 gas. Both the demulsifier and CO2 are indispensable in this demulsification treatment process. The demulsification efficiency increases rapidly with the increase of demulsifier concentration when the initial concentration is lower than 120 mg/L. With the further increase of concentration, the demulsification efficiency can reach 83% and remain constant. Meanwhile, the demulsification efficiency increases with the increase of CO2 pressure. It is found that the optimum CO2 pressure is between SO and 200 kPa, with a mixing time of 65-125 min, where a demulsification efficiency of approximately 80-90% can be achieved. Settling under elevated temperature (70 degrees C), after CO2 demulsification, is also investigated; the results indicate that heating does not improve the demulsification efficiency if the pressure is over 500 kPa. Under the same conditions, CO2 shows better demulsification efficiency than that obtained by HCl and CH3COOH. At a pH of approximately 7.0-7.7, the emulsion is the least stable, and the maximum demulsification efficiency is obtained.