Oil displacement behavior of biosurfactant/chemically synthetic surfactant binary system in a microfluidic chip

Alkali-Surfactant (biosurfactant/petroleum-based surfactant formulation) -Polymer (ASP) flooding has been applied to enhance oil recovery in Daqing oilfield, however, the critical role of biosurfactant and petroleum-based surfactant have not been sufficiently explored. Here, the characteristics of biosurfactant, lipopeptides (LPs), and petroleum-based synthetic surfactant, heavy alkyl benzene sulfonate (HABS), and LPs/HABS binary formulation in displacing model oil were determined in a microfluidic chip. The images of the chip with a physical rock network and the injection pressure were simultaneously captured during the displacing process. The oil displacement characteristics of LPs/HABS binary formulation was quantitatively analyzed from the aspects of displacement efficiency, threshold pressure, swept area, displacement efficiency within swept area, and the distributions of remaining oil. Results revealed that LPs/HABS binary systems had the higher displacement efficiency and the lower values of threshold pressure. It was suggested that the lower interfacial tensions between LPs/HABS binary displacing solution and model oil induced higher value of capillary number , which effectively reduced the resistance for displacing solution when entering the pore structure of the network. As for the displacement efficiency in the swept region, LPs systems and LPs/HABS binary systems performed better to obtain higher displacement efficiency due to the superiority of LPs in wettability alteration. Results in the present work is beneficial for fundamental understand of microscopic displacement feature of lipopeptides/petroleum-based surfactant binary formations. • Oil displacement feature of LPs/HABS blend is studied using a microfluidic chip. • LPs/HABS blends show synergistic effect in reducing oil/water interfacial tension. • LPs/HABS blends show synergistic effect in displacement efficiency of model oil. • LPs-contained floodings have higher displacement efficiency within swept area. • Interfacial tension reduction and wettability alteration are key factors.