Abstract: Low-permeability oil reservoirs have unique features of low abundance, low pressure, and low yield, their economic and effective exploitation are very difficult. Gas injection is the more efficient recovery method for such reservoirs at home and abroad. With numerical simulator, the main influencing factors affecting CO₂ flooding are determined, including analysis of the components of split and fitting, selection of state equation and experimental regression, etc. The study results show that phase behavior simulation is the key of success or failure in numerical simulation of compositional model. The mode of water-gas alternating injection, with properly increasing the injection pressure and selecting appropriate bottom-hole flowing pressure, has obvious effect on incremental production and EOR. Numerical simulation indicates that different well patterns or spacings, heterogeneity, fracture direction, gas injection parameters are the sensitive controlling factors of CO₂ flooding, directly affecting reservoir development index and development effect.

Key words: CO₂ flooding, low-permeability reservoir, numerical simulation, recovery, influencing factor