Among chemical flooding methods, surfactant flooding processes are particularly effective for recovering a large fraction of conventional oil left in the reservoir after water flood – which could be as much as 60% of the original oil in place. The basic principle behind the use of surfactant flooding is to recover the capillary-trapped residual oil remaining after water flooding by injecting surfactant solution; the residual oil can be mobilized through a strong reduction in the interfacial tension (IFT) between oil and water. If the interfacial tension can be reduced between the oil and water, the resistance to flow is definitely reduced. If surfactants are properly selected, a reduction in interfacial tension could be as much as 10-3 dynes/cm, a recovery of 10-20% of the original oil in place, when not producible by other technologies, is technically and economically feasible by surfactant feasible by surfactant flooding.
MECHANISM
Following the injection of surfactants into the water-flooded section of the reservoir, interfacial tension between oil and water become reduced and this leads to the mobilization and coalescence of trapped oil droplets. The resultant effect is an increase in oil saturation subsequently leading to a mobile oil bank. Surfactant also prevents already mobilized oil from being re-trapped behind the oil bank.