Influence of injected gas type and reservoir conditions on the oil migration in calcite nanoslits

The oil migration in nanoslits is essential to enhance oil recovery. In this study, the calcite was selected as typical representative of deep and medium-shallow reservoir, the effect of gas on oil migration behavior in calcite nanoslits is investigated at molecular level. Two types of migration behaviors, via overall migration and gas channel, were observed for oil in gas flooding, which was determining by the stability of oil adsorption region. Specifically, if the interaction of gas/nanoslits was more vigorous than that of oil/nanoslits, the oil adsorption region will remain stable and the oil would be overall migration; otherwise it formed gas channel. The influence of injected gas on oil migration had the sequence of CO2>C3H8>CH4>N2 under deep reservoirs, which is better than that under medium-shallow reservoirs. Our study highlighted the influence of injected gas and reservoir conditions on the oil migration at a molecular level, which might help facilitate the exploration of deep reservoirs.

Automated summary

This study investigated the effects of gas on oil migration behavior in calcite nanoslits at a molecular level, revealing two types of migration behaviors during gas flooding: overall migration and gas channel. It was found that the injected gas had a sequence of CO2>C3H8>CH4>N2 under deep reservoirs, which may facilitate the exploration of deep reservoirs.