Alterations in wettability and immiscible fluid flows by bacterial biosurfactant production for microbial enhanced oil recovery: Pore-scale micromodel study

Abstract

This study investigates alterations in wettability during bacterial growth and biosurfactant production and its ensuing impacts on immiscible fluid flow at a pore scale. Here, pore-scale experiments were carried out with two types of patterned micromodels. First, the experiments with a single-channel micromodel visually captured the real-time wettability alteration from oil-wet to water-wet while cultivating the model bacteria Bacillus subtilis, in which the bacterial cells and produced biosurfactant significantly lowered the contact angles, including static, advancing, and receding angles, by similar to 70-90 degrees. In addition, the emulsification-demulsification phenomena at brine-oil interfaces and the contact angle alterations by biofilms were also observed. Second, the surfactantflooding process was emulated in the experiments with multi-channel micromodel while examining the effect of surfactant concentration on oil sweeping efficiency. The results of the multi-channel micromodel experiment show that a biosurfactant concentration of 70 mg/L, which is twice the critical micelle concentration, resulted in a lower contact angle, reduced residual oil saturation, and more homogeneous and stable patterns of oil displacement. Particularly, a significant level of variations in the contact angles at fluid-solid interfaces was observed in the multi-channel micromodel, and the extent of variation decreased with an increase in biosurfactant concentration. The presented results provide insights into pore-scale coupled microbial-hydrological processes in porous media as well as the biosurfactant-aided flooding in microbial enhanced oil recovery (MEOR).