Fabrication of a pH-responsive emulsifier for heavy oil recovery based on dynamic imine bond

Abstract

In order to ensure the emulsification function of chemical flooding and simultaneously relieve the difficulty in demulsification of produced fluid in heavy oilfield, a pH-responsive surfactant HB-HA− (4-hydroxybenzaldehyde (HB) and n-hexylamine (HA)) was constructed based on dynamic imine bond. The molecular structure and its pH-responsive property was characterized by 1H NMR. Then, an emulsifier system CTAB/HB-HA− for heavy oil was fabricated by mixing hexadecyltrimethylammonium bromide (CTAB) with the constructed HB-HA− as the molar ratio of 1:1. The emulsification and pH-responsive property of the emulsifier were evaluated by macroscopic and microscopic appearance of heavy oil emulsion prepared under different pH, the surface tension (SFT) and interfacial tension (IFT) were determined to explore the pH response mechanism. The results showed that the emulsifier had strong emulsification and IFT reduction ability under pH = 12, and the emulsion can be stable for more than 48 h. As pH decreased to 5, the emulsion demulsified within 30 min. This emulsifier guaranteed good emulsification during recovery process and rapid demulsification property after the treatment process of produced liquid in the petroleum industry.