Abstract: The leakage after CO_2 sequestration is critical in the evaluation of CO_2 storage period and the stability of the cap-rock. In this paper, the commercial FEM software ABAQUS is used with a secondary development to analyze the key factors of CO_2 seepage. Meanwhile the gas Vander-Walls equation is applied to the supercritical CO_2 compared to the ideal gas equation. A simple theoretical result is obtained and verified in a good agreement with that of simulation. The results show that at least 150 000 years are needed until CO_2 escapes completely from a homogeneous cap-rock with a low permeability; the number storage duration is decreaseds to 10 000 years when there is a high permeability leaky well or fractures, hence, fractures or leaky wells should be consolidated before sequestration or kept away from project areas.

Key words: CO2 geological sequestration, leakage, seepage