Abstract
Surfactants play an important role in enhanced oil recovery by reducing the interfacial tension (IFT) between oil and water and changing the wettability of reservoir rock. Studies have been made to determine the effect of temperature, salt, alkali and polymer on IFT in the presence of anionic (SDS), cationic (CTAB) and nonionic (Tween 80) surfactants. The experimental data reveal that with increase in temperature the surface tension and IFT of the above surfactants are significantly reduced. IFT values of surfactants are also affected by the presence of polymer, alkali and salt. The results show that the addition of polymer increases the IFT as well as the contact angle of all the surfactant solutions. On the other hand, the presence of alkali in surfactant solution reduces the IFT between crude oil and water as alkali reacts with the acidic components of crude oil to form additional in-situ surfactants. It has been found that the presence of salt in an aqueous solution of different surfactants reduces IFT and contact angle as the salt increases the tendency of the surface active agents to accumulate at the interface. Sand pack flooding in presence of different chemical combinations has also been investigated. It has been found that the enhanced oil recovery by alkali-surfactant-polymer flooding is better than the corresponding surfactant and surfactant-polymer flooding.