Pore-scale study of dynamic surfactant adsorption under immiscible displacement in porous media: effect of wetting conditions

Abstract

Surfactant flooding is one of the most effective methods of enhanced oil recovery, because it helps to reduce oil-water interfacial tension and mobilize the residual oil. Surfactant molecules can be adsorbed on the particle surface. This paper presents a systematic study of the dynamic adsorption of a water-soluble surfactant during flooding of oil-saturated porous media. The novelty lies in the study of dynamic adsorption with multiphase flows in porous media, which provides new trends. The main goal is to reveal the effect of wetting angle, interfacial tension, flow rate, and adsorption rate constant on the adsorbed amount in the immiscible displacement. Lattice Boltzmann simulations are used to study this problem. The flow regions are represented by digital images of granular porous structures. A map characterizing the adsorbed amount of surfactant versus wetting angle and interfacial tension has been presented. The results showed that increasing the wetting angle positively affects the adsorbed amount, while increasing interfacial tension suppresses the adsorbed value. Different patterns of dynamic adsorption in dependence on flow rate and adsorption rate constant have been identified. At low adsorption rates, regardless of the wetting angle and interfacial tension, a decrease in the flow rate contributes to an increase in the adsorbed amount. At high adsorption rates, the adsorbed amount is determined by the displacement efficiency. The obtained tendencies have been validated by performing a series of simulations on a group of porous structures. It has been found that the prediction reliability of the adsorbed amount increases with increasing wetting angle and capillary number.