Flowing Characteristics of CO₂-Oil System in Miscible Phase Flooding in Porous Media

At present, oil recovery by CO₂ driving is getting increasingly important.In order to probe into the flow mechanism of CO₂ in miscible state, a high temperature and high pressure 3-D device was used to study miscible flooding of CO₂ and oil.With this experiment, it is found that there is a big difference between the production and the injection volume.The complex flowing characteristics of CO₂ flooding in porous media are observed in the recovery, water cut and gas-oil ratio curves.By analyzing water saturation distribution map which is measured by saturation probe, it is proved that CO₂ and oil can be miscible.The viscosity of miscible liquid and flowing pressure decreases, which is one of the important mechanisms in enhanced oil recovery.At the same time, miscible CO₂ and oil contacted with water can make up a similar 3 phase state.Experiment results also show that the main reason for the difference between the production and the injection is that CO₂ can flow into micro pores in high density gas state while water and oil cann't.