Preparation and evaluation of hydroxymethylated betaine surfactant for enhanced recovery application

Abstract Exploring amidopropyl betaines with high interfacial activity and low cost is highly desired but remains a daunting challenge for modern oilfields enhancing quality and efficiency. Herein, a cost-effective surfactant (ROB-HM) with high interfacial activity and oil-washing capability was successfully synthesized through formaldehyde modification strategy. The effects of formaldehyde molar ratio, catalyst dosage, reaction temperature and time were investigated, and the optimal reaction conditions were determined. The compound was characterized by mass spectrometry and Fourier transform infrared spectroscopy, and the interfacial tension, surface tension, apparent viscosity, critical micelle concentration (CMC), wettability, emulsification capacity and oil recovery rate were comprehensively evaluated. Compared to its performance before modification, ROB-HM shows significantly higher interfacial activity at low concentrations, which can be attributed to the efficient arrangement of the introduced methanol group surfactant molecules. Additionally, the CMC of ROB-HM is considerably lower than before modification, having more opportunities to form micelles. Meanwhile, the other oil-washing capabilities of ROB-HM also shows desirable results. This work paves a novel route for designing and modifying molecular structures to increase the polarity group of surfactants and affect the surface interface activity, which are suitable for enhanced oilfield recovery.