In order to further clarify the mechanism of steam flooding assisted by CO

2

in the heavy oil reservoir

its visualization experiments are carried out by the acrylic plate model and natural cores

and their synergy is analyzed. After the mechanism of synergistic displacement is clarified

the core flow experiments are carried out to further analyze the influence of the synergistic effect and the injection mode on the actual displacement efficiency. The results show that CO

2

assisted steam flooding has the effects of the synergistic viscosity reduction

the expansion of steam sweep efficiency

the availability of residual oil at the blind end

and the demulsification. Among them

the comprehensive viscosity

reduction rate of the crude oil is 59.8 %

and the steam sweep area is increased by 37.44 %. Compared to the flooding by steam alone

after the assitant of CO

2

the recovery rate increased significantly. The alternate injection of steam and CO

2

can get a recovery rate of 65.7 %

7.9 % more than that of mixed injection

and observe the stable foam oil flow at the outlet.