Influence of Surfactant Type, Surfactant Concentration, and Salinity on Interfacial Tension of a Brine/Live Oil/Surfactant Fluid System: A Case Study of Iranian Asmari Oil Reservoir

The chemical surfactant flooding can mobilize the trapped oil by lowering the interfacial tension between oil and brine and in some cases altering the reservoir rock wettability. In this work, the effect of surfactants on oil/brine interfacial tension was experimentally investigated. First, the effect of surfactants concentration was surveyed. Afterwards, the effect of salinity on surfactant behavior was studied. The experiments were carried out at ambient and reservoir temperatures (all at reservoir pressure) to clarify that we cannot generalize the ambient experimental results to reservoir ones and the experiments must be done in reservoir conditions to attain more certainty. Sodium dodecyl sulfonate, cetyl trimethyl ammonium bromide and Triton X-100 were used as the surfactants. The oil and brine samples of the Iranian Asmari reservoir were used. Pendant drop method was used to measure oil/brine interfacial tension. Based on the results, it is concluded that the anionic surfactant (SDS) has a better performance at reservoir and ambient temperatures. The superiority of SDS is more emphatic at reservoir temperature than ambient temperature. At reservoir temperature, the SDS solution lowers the interfacial tension significantly (0.4 mN/m) even when a very low concentration of SDS (0.04 wt.%) is added to brine.