CO

2

immiscible flooding is a very important technology for low permeability reservoirs with strong heterogeneity

high miscibility pressure of crude oil or severe reservoir voidage. Firstly

the expansion experiments and MMP test of CO

2

injection are carried out

and the IFT and mole content of oil and gas phase of each block are tested by numerical simulation. And then

the dominant mechanism of CO

2

injection to recover reservoir energy and improve oil displacement efficiency in low permeability reservoir are revealed. Therefore

taking M Block with low-permeability as the research object

and bas

ed on 3D fine geological modeling

the numerical simulation is applied to optimize reservoir pressure

gas injection volume

gas injection velocity

shut-in gas-oil ratio and other parameters

and the optimal technical policy is formulated. Preferable recovery performance is obtained through field application. The results show that for the CO

2

immiscible flooding technology in low permeability reservoirs

dissolving and expanding oil phase by gas injection are the dominant mechanism for both recovering reservoir energy and improving oil displacement efficiency

besides

the latter still need to reduce the IFT and evaporate and extract the light components. This study provides a reference for the formulation of CO

2

immiscible continuous flooding scheme in other reservoirs of the same type.