Abstract: CO₂ geosequestration technology is an important method to mitigate the greenhouse effect, and the evaluation of leakage risk in geosequestration system is a prerequisite to ensure the safe and efficient sequestration of CO₂. To address the risk of CO₂ leakage, the influence of wellbore and caprock factors on the risk of CO₂ leakage in CO₂ geosequestration system was systematically discussed, including the quality of cementing, CO₂ corrosion and damage to the wellbore assembly by alternating stress, as well as the influence of caprock-formation ratio, caprock thickness and lithology on low-speed seepage and high-speed leakage of caprock. Finally, the wellbore leakage risk evaluation method, the caprock leakage risk evaluation method and the CO₂ sequestration system leakage risk evaluation method based on the combined action of the above influencing factors were discussed, and the advantages and disadvantages of different evaluation methods were pointed out. The study provides theoretical support for site selection, formation selection and leakage risk evaluation in CO₂ geosequestration works.

Key words: CO₂ geosequestration, CO₂ leakage, wellbore, caprock, CO₂ corrosion, cementing quality