THE SIMULATION OF VISCOUS FINGERING BY USING A DIFFUSION-LIMITED-AGGREGATION MODEL DURING CO2 FLOODING

Under the conditions of high temperature and high pressure, viscous fingering phenomenon occurs during CO2 flooding because of viscosity differences between CO2 and crude oil, which leads to premature breakthrough of displacement fluid and the decrease of sweep efficiency. Therefore, oil production cannot reach the expected yields. In this paper, we investigate the effect of viscosity ratio, injection rate, and pore structure on viscous fingering in 3D digital cores obtained by CT experiments based on a diffusion-limited-aggregation (DLA) model. The results show that viscosity difference is the dominating factor that influences viscous fingering. With the increase of viscosity difference between the two displacement fluids, sweep efficiency decreases dramatically. In a lower permeable reservoir and at an appropriate injection rate, the viscous fingering can be decreased. The numerical simulation is validated against the CO2 flooding experiment.