The CO

2

miscible flooding project in the Taizhou formation of Caoshe oilfield is one of the most successful CO

2

EOR projects in China. The feasibility study on the secondary miscible flooding was carried out to settle the issues of complex remaining oil distribution and severe gas channeling in the later stage after first miscible flooding. The characteristic of microscopic fractal dimension in the CO

2

miscible flooding process of real core sample was observed through metalloscope. The remaining oil types attaching to the pore surface of rock took on the forms of thin film and isolated beads. The displacement efficiency of the secondary CO

2

miscible floo

ding was 93.4 %

which was 9.73 % higher than that of the first CO

2

miscible flooding. The average residual oil saturation was 30.8 % in sealed coring test

indicating great potential of III formation. A feasible development plan for secondary miscible-phases flooding was proposed to develop the stratified reservoirs at the bottom position. The CO

2

injection on the higher position was adopt to suppress gas gravity overlap

and the water alternating gas was applied to slow down the gas channeling. Furthermore

the injection profile was adjusted during the whole process of gas injection. The incremental recovery ratio was estimated to be 8 % ~ 10 %.