Impact of spacer and hydrophobic tail on interfacial and rheological properties of cationic amido-amine gemini surfactants for EOR application

The impact of spacer length, spacer rigidity, trans and cis conformation of spacer double bond, and hydrophobic tail length of amido-amine cationic gemini surfactants was investigated by means of interfacial and rheological properties. For the study, six cationic amido-amine gemini surfactants were synthesized and used a cationic polyacrylamide. The interfacial tension (IFT) of the surfactants between crude oil and water was measured as a function of the surfactant concentration. It has been observed that the nature of the spacer and hydrophobic moiety have a significant effect on the oil/water interfacial tension. Rheological measurements of the surfactant-polymer hybrid system were performed at various surfactant concentrations, shear rates and temperatures. All synthesized cationic gemini surfactants were compatible with the cationic polyacrylamide since no precipitates were observed. By increasing the surfactant concentration, the storage modulus, as well as viscous properties of the cationic polyacrylamide, decreased at all temperatures because of the effect of charge shielding. On the other hand, the effect of concentration of surfactant was only significant at low shear rates. The storage modulus and viscous properties of the cationic polyacrylamide were also decreased significantly upon increasing surfactant tail length (C₁₂ to C₁₈). However, spacer rigidity, length, and conformation of spacer double bond caused a slight decrease in the storage modulus and viscous properties of cationic polyacrylamide. IFT, rheological properties, and compatibility tests showed huge potential of investigated surfactant-polymer system for enhanced oil production.