Salinity Effect in Cloud Point Phenomena by Nonionic Surfactants Used in Enhanced Oil Recovery Tests

The cloud point phenomenon for solutions of polyoxyethylene (POE)-type nonionic surfactants (B, C, D, and E) in different salt concentrations was investigated. The cloud point temperature, T-c, increased with elongation of the POE chain. This demonstrated that the solvophilicity of the surfactants comes from POE chain. Thus, the cloud point decreased with increase of salt concentration. Surfactants D and E were the only ones that showed cloud point temperatures above the average temperature of oil wells (similar to 70 degrees C), even at high concentrations of salt, and surfactant E was most suitable for enhanced oil recovery operations.