CO

2

enhanced oil recovery（EOR） with carbon capture and storage（CCS） projects offer dual benefits of increasing oil recovery and CO

2

storage

making it one of the most economically viable carbon sequestration methods nowadays. However

EOR-CCS projects typically involve multiple well sites

and the high risk of CO

2

leakage from wellbores poses significant safety and environmental challenges over large areas. To address the limitations of previous atmospheric diffusion studies based on point-source leakage at well sites

a new method for studying surface CO

2

leakage and atmospheric diffusion in EOR-CC

S projects based on area-source flux monitoring at well sites was developed. A case study of an oilfield in East China

based on scenario analysis

demonstrated that CO

2

leakage flux monitoring using the eddy covariance method could provide accurate data on area-source leakage fluxes for entire well sites

enabling large-scale computational fluid dynamics（CFD） simulations. Multi-well-site CFD diffusion simulations effectively captured the impact of complex regional topography and multiple well sites on CO

2

leakage

supporting regional safety and environmental risk management for well site leakage.