Prior to the flooding tests, interfacial tension measurements between the oil and brine samples were performed for different type of oils and 5,000-ppm surfactant solution. For the case of the nonionic surfactant-black oil system, the system was best described as a case of mixed wettability. For the anionic surfactant-black oil system, there was an increase in enhanced oil recovery as surfactant concentration increased. For the anionic surfactant-tetradecane system, again the presence of emulsion for concentrations greater than 500 ppm limited the analysis. Nevertheless, for concentrations of 1,500 ppm or less the application was efficient, resulting in enhanced oil recovery of approximately 5%.