Effect OF NaCl in cloud point of nonionic surfactants and adsorption behavior for chemical flooding in enhanced oil recovery

Surfactants are widely used in enhanced oil recovery, due to its chemical properties, like reduction of the interfacial tension between two immiscible liquids. For nonionic surfactants, the cloud temperature is an aspect important to be evaluated, since above this temperature an initially homogenous surfactant solution separates into two phases, losing their proprieties. This work evaluates cloud temperature, critical micelle concentration and adsorption for solutions of nonionic surfactant with different concentrations of NaCl, used in enhanced oil recovery. Nonionic surfactants polyoxyethylene (20) sorbitan monolaurate (T20), polyoxyethylene (20) sorbitan monooleate (T80), octylphenol ethoxylate with 10 moles of ethylene oxide (TX100), and Nonylphenol polyoxyethylene with 15 moles of ethylene oxide (U150) were used. From results obtained, it was observed that cloud points varied considerably for surfactants studied and, also, with different NaCl concentrations. Was observed that for the surfactants studied, except for the TX100, cloud point temperatures exhibited values above the average temperature of oil wells (~55 oC).It means that these surfactants can be used for oil recovery, significantly broadens the scope of application for conventional chemical EOR methods, getting good recovery results and without large losses of surfactant by adsorption amount (0,08 g surfactant/g sandstone), making the process more efficient.