Effect of temperature and salinity on interfacial behavior of alkyl ether carboxylate surfactants

This work investigates the interfacial behavior of alkyl ether carboxylate (AEC) surfactants in examples of sodium laureth-11 carboxylate and sodium trideceth-7 carboxylate. AECs have two hydrophilic groups and demonstrate both anionic and nonionic properties, displaying stability under harsh reservoir conditions during surfactant flooding. The interfacial tension measurements were conducted with a spinning drop tensiometer; n-decane, and oil were used as the hydrocarbon phase. The influence of surfactant concentration, temperature (25 °C and 70 °C), and various ions (Na+, Ca2+, Mg2+, Cl−, SO4−, and HCO3−) were evaluated. It was found that the temperature increase has no significant effect on critical micelle concentration (CMC) for both surfactants but influences interfacial tension values in pre-CMC and post-CMC regions. According to data obtained, the temperature rise has a stronger impact on a surfactant with a longer oxyethylene chain sodium laureth-11 carboxylate. In contrast, brine salinity has a more substantial effect on sodium trideceth-7 carboxylate interfacial behavior.