Guerbet Alkoxy Betaine Surfactant for Surfactant-Polymer Flooding in High Temperature, High Salinity Reservoirs

In recent decade, various betaine surfactants have been developed and extensively investigated for binary Surfactant-Polymer flooding (SP flooding) due to their high interfacial activity at oil-water interface, excellent thermal tolerant and salt/divalent ion resistant characteristics under harsh reservoir conditions. Herein, a new type of guerbet alkoxy betaine surfactant (GAB) was prepared and evaluated for SP flooding. In order to boost the emulsification capability of betaine surfactant, ethylene oxide (EO) functional group was incorporated into betaine molecule and guerbet alcohol was selected as hydrophobic group. Firstly, glycidyl ether was prepared by reaction of alkoxylated Guerbet alcohol and epoxy chloropropane. Then, glycidyl ether and dimethyl amine generated tertiary amine. In the last step, surfactant GAB was synthesized by quarternization reaction of tertiary amine with 3-chloro-2-hydroxyl propanesulfonic acid sodium salt. In-lab performance evaluations, including interfacial tension, long term stability, contact angle, and phase behavior were conducted for this GAB surfactant. The developed surfactant demonstrated very good compatibility with high temperature, high salinity (HTHS) reservoir conditions. Applicability range of GAB surfactant amounted to 275,000 mg/L and 120 °C. Ultralow interfacial tension with crude oil was obtained using diluted GAB solutions with weight concentration ranging from 0.03% to 0.20%. For formulation composed by 0.5% GAB and 0.5% amidobetaine, Winsor III middle phase microemulsion was formed with dehydrated light oil from a high temperature, high salinity carbonate reservoir. The solubilization ratio mounted to 16 at reservoir temperature of 95 °C and optimal salinity of 50,000 mg/L. Compared with guerbet alkoxy sulfate surfactant and conventional sulfobetaine with similar structure, the developed betaine surfactant GAB showed better thermal stability, higher interfacial activity, and intensified emulsification capability under HTHS conditions.