CO
2 convective mixing in water has been visualized in Hele-Shaw and PVT cell experiments but not at the pore scale. Furthermore, CO
2 convective mixing in a three-phase system (i.e., CO
2 in the presence of both water and oil) has not
[...] Read more.
CO
2 convective mixing in water has been visualized in Hele-Shaw and PVT cell experiments but not at the pore scale. Furthermore, CO
2 convective mixing in a three-phase system (i.e., CO
2 in the presence of both water and oil) has not been visually investigated. A vertically placed micromodel setup was used to visualize CO
2 convective mixing at 100 bar and 50 °C, representative of reservoir conditions. To the best of our knowledge, for the first time, we have visually investigated CO
2 convective mixing in water at the pore scale and also CO
2 convective mixing in a multiphase system (water and oil). CO
2 mixing in water governed by both diffusion and convection mechanisms was observed. The vertical CO
2 transport velocity was calculated to be 0.3 mm/min in both a 100% water saturation system and a residual oil-saturated system. First, CO
2 always found the easiest path through the connected pores, and then CO
2 was transported into less connected pores and dead-end pores. CO
2 transport into dead-end pores was slower than through the preferential path. CO
2 transport into water-filled ganglia with trapped oil was observed and was slower than in water.
Full article