Evaluation method and risk control of CO2 leakage are key issues for carbon capture and storage（CCS).In order to reveal affecting factors and features of CO2 leakage during injection

a two-phase flow model was proposed to describe the leakage process

and numerical simulations were conducted using a commercial software COMSOL Multiphysics 3.5a.Based on comparison and extension of its solutions for a benchmark problem

the affecting factors

including distance between the injection well and leaky path

radius and permeability of leaky path

injection rate and injection depth

were investigated. The quantitative relationships between leakage rates and impact factors were obtained from simulations and data analysis.The results show that asymptotic leakage rates of CO2 are linearly dependent on the reciprocal of distance between the injection well and leaky path

are quadratic with radius of leak path

and are linear with respect injection rates.The permeability of leaky path is the key factor controlling CO2 leakage

whereas the increase of injection depth has little effect on decreasing CO2 leakage rates.The proposed model and simulation results not only reveal the relationship between CO2 leakage rates and impact factor quantitatively

but also provide analytical method and computational tools for site selection

evaluation of leakage and risk management of CO2 injection into subsurface formations.