(126d) Chemical EOR by Wettability Alteration

Waterflooding is not very efficient in non-fractured or fractured oil-wet reservoirs. The ionic composition of the brine and addition of surfactants can change the wettability of the reservoir rocks from oil-wet to intermediate-wet. The effect of wettability alteration on secondary flood would be described. More than 50% OOIP (original oil in place) can be recovered from fractured carbonates by the use of a dilute (<0.1 wt%) surfactant solution. Effect of surfactants on wettability / interfacial tension and the resulting spontaneous imbibition into fracture blocks would be described. Sensitivity of the process to temperature and fracture spacing would be discussed. Mechanistic numerical simulations that match laboratory experiments and identify field conditions for successful surfactant-aided gravity drainage would be outlined.