At present

there are many researches on the interfacial interaction between CO_2 and oil

but few on the interfacial interaction of CO_2-water-oil. In this paper

axisymmetric drop shape analysis method is used to analyze the influence of different CO_2 saturations on the interfacial tension of crude oil-formation water and the change of the interfacial tension between crude oil-carbonate water and crude oil-formation water. In addition

the extraction of light hydrocarbon components from oil drops by CO_2 through the gas-water interface is studied. The results show that

the equilibrium interfacial tension of crude oil-carbonated water system decreases with the increase of pressure

and the dissolution and diffusion of the system becomes more and more obvious with the increase of pressure. The medium exchange occurs between oil and carbonated water

and the phenomenon of partial miscibility occurs. When the pressure is higher than the pressure threshold of 17.09 MPa

the increasing trend of CO_2 solubility becomes slower

and the interfacial tension of crude oil saturated CO_2 formation water decreases slowly and remains unchanged. In practical production

when the pressure is lower than the system threshold pressure

increasing CO_2 content can effectively reduce the interfacial tension. When the pressure is higher than the threshold pressure

increasing CO_2 content has little effect on the equilibrium interfacial tension.