Mixed anionic-nonionic surfactant microemulsion with decane and spontaneous imbibition test for enhanced oil recovery

Abstract

Crude oil production focuses on recovering the highest amount of oil from a reservoir. However, only 45% to 50% of the original oil in place is recovered by natural pressure and water flooding techniques. The challenge lies in developing new methods to extract the remaining oil in the reservoir. In this work, sulfate or sulfonate anionic surfactants were mixed with a non-ionic surfactant to study phase behavior. The effect of salinity was studied by the varying NaCl concentration from 1wt% to 10wt%. Decane was used as representative of oil phase. Phase behavior especially middle phase (Winsor type III) was studied and used for screening suitable surfactant formulas. Results show that single anionic surfactant systems cannot provide the middle phase and precipitation of the anionic surfactant is observed at high salt concentration. The precipitate of anionic surfactant can solve by adding of non-ionic surfactant to improve solubilization of the middle phase. The middle phase with thick layer and equal phase height was obtained from sodium dodecylbenzene sulfonic acid (SDBS) as anionic surfactant mixed with the nonionic surfactant, Triton X-100 at 12.5wt% NaCl and Tergitol TMN6 at 8.5wt% NaCl, respectively. Spontaneous imbibition tests also determined the mixed SDBS/Tergitol® TMN6 surfactant at 8.5%wt salinity is the optimum surfactant formula with the lowest IFT and had capacity to recovered 39.55% of decane from sandstone core sample.