The effect of light gas on miscible CO2 flooding to enhance oil recovery from sandstone and chalk reservoirs

Abstract

Lower oil recovery is observed from sandstone cores than from chalk for synthetic dead and live oils with miscible CO2 flooding. This was attributed to the greater likelihood of developing fingers in sandstone cores and lower exposed surface areas compared to chalk. This was assessed by addressing the effect of the transverse dispersion on viscous instability. Recombined oil with C1 in chalk and sandstone cores and flooding with CO2 shows higher recovery than the case of recombination with C1/C3. A ternary diagram was constructed for the two cases in order to understand the CO2 flooding mechanisms at the different flooding conditions.