Simulation of Two-Phase Fluid Flow in the Digital Model of a Pore Space of Sandstone at Different Surface Tensions

Abstract

© 2020, Springer Science+Business Media, LLC, part of Springer Nature. A study is made of the influence of surface tension on two-phase drainage flows in a porous medium. Computational filtration experiments are conducted in a three-dimensional digital microtomographic model of sandstone. To simulate two-phase flows, use is made of lattice Boltzmann equations; interfacial phenomena and wetting effects are described using the color-gradient-based method. Calculations are carried out at the same rate of injection of a nonwetting fluid and at a ratio of the viscosities of nonwetting and wetting phases of 1:10. Results are obtained according to which growth in the interfacial tension contributes to the rise in the efficiency of displacement of the wetting fluid, which is recorded at the moment the injected phase breaks through, and to the decrease in the efficiency after its breakthrough. It is established that distinctive features of flows with capillary fingering that arise at high surface tensions are the stepwise character of travel of the leading front and the growth of displacement channels in directions different from the hydrodynamic pressure difference. It is shown that interfacial tension is a parameter whose variation enables us to change the type of two-phase flow. Increase in the interfacial tension contributes to the transition of the flow with viscous fingering to a flow with capillary fingering. The efficiency of displacement of the wetting fluid in the transition crossover zone is the lowest.