Effects of interfacial tension, oil layer break time, emulsification and wettability alteration on oil recovery for carbonate reservoirs

Abstract

Experimental investigations targeting optimum chemical slug formulations for tertiary enhance oil recovery of heavy crude oil in carbonate reservoir were carried out. Based on interfacial tension (IFT), emulsification, wettability alteration and core flooding studies, two alkalis and eight surfactants have been screened by considering conditions similar to oil reservoirs (0–20% salinity and 30–80 °C temperature). Dynamic IFT studies interestingly affirmed oil-layer break time phenomena and hence enhanced emulsification extent. Alkali, thermally stable surfactant mixture and alkali-surfactant mixture systems reduced IFT to 10−1, 10−2 and 10−3 mN/m respectively. Flooding studied confirmed an additional oil recovery of 12.79% and 14.46% for alkali and alkali-surfactant mixture systems respectively. On the other hand, due to optimal emulsion stability, maximal residual oil recovery of 24.58% being achieved for a slug formulation of 0.1 wt% surfactant mixture. Surfactant concentration above 0.1 wt% enabled stronger emulsion formation that detriments displacement efficiency and oil recovery factor.