(603d) Switchable Crude Oil/Water Nanomulsions Stabilized By Sdbs for Oilfield Applications

Crude oil emulsification is one of the key mechanisms for the enhancement of oil recovery. Although it is desirable to create stable emulsions during the recovery process, they must be easy to break in order to recover the emulsified crude oil. Thus, the key objective of the current work is to demonstrate that very stable, but yet easy to break, crude oil-in-water (CO/W) nanoemulsions can be prepared using sodium dodecylbenzene sulfonate (SDBS). To achieve this objective, stable CO/W nanoemulsions stabilized by SDBS were prepared. The volumetric crude oil: water ratio was kept at 20:80. In each experiment, a coarse emulsion was prepared by mixing SDBS aqueous solution with crude oil overnight using a magnetic stirrer. Then, the nanoemulsion was prepared by sonicating the coarse emulsion using a probe sonicator for 15 min at 80% amplitude with a pulse of 30 s followed by 3 s off. The stability of the prepared nanoemulsions was monitored for more than a month. Additionally, the effectiveness of pH adjustment (i.e., pH-switch) in breaking the nanoemulsions was examined. The results demonstrated that all the prepared CO/W nanoemulsions (using 0.1, 0.5, 2, and 4% SDBS) were very stable with 0% oil separation after more than a month of incubation (water separation was also 0%). Despite the high stability of these nanoemulsions, it was possible to quickly destabilize the nanoemulsions prepared using 0.1 and 0.5% SDBS and fully recover the emulsified crude oil through the addition of NaOH or HCl (final concentration in the nanoemulsion = 0.5 M). Furthermore, the addition of NaOH resulted in the full demulsification of the nanoemulsion prepared using 2% SDBS. However, the addition of HCl was ineffective in switching off this nanoemulsion. Additionally, both NaOH and HCl were unable to fully breakdown the nanoemulsion stabilized by 4% SDBS. These results show that the pH-switchability of the CO/W nanoemulsions depends on the concentration of the emulsifier (i.e., SDBS). For low levels of SDBS, increasing or decreasing the nanoemulsion pH can lead to a full separation of the oil. On the other hand, for high levels of SDBS, oil separation using pH-switch is unsatisfactory.