Oil Recovery from Micropatterned Triangular Troughs during a Surfactant Flood

We study the recovery of oil trapped inside micropatterned triangular troughs after injecting a surfactant solution. In our experiments, we track the trapped oil volume with duration of surfactant flood for different capillary numbers. We observe that the capillary number affects the amount of oil recovered as the well as the rate of oil recovery. We employ multiphase flow simulations to analyze our system and show a qualitative agreement between the simulations and experimental results. We also discover that beyond a capillary number, the volume of oil recovered plateaus, and no additional oil is released with an increase in capillary number. We develop a theoretical model to predict the dependence of maximum oil recovery on geometrical features and find that the theoretical predictions compare favorably with the trends obtained from our simulations. Though approximate, theoretical relation provides insights into the efficiency of oil recovery and can be utilized to understand the effect of sharp bends and dead ends in enhanced oil recovery and soil remediation.