The purpose of this paper is to apply a qualitative risk assessment method to a mature oil field as a pilot experiment of CO
geological storage in Brazil. This study was structured based on discussions with experts, analysis of available real data from field and literature databases. The results from the application of this method shows that most of the risk scenarios were predominantly classified as low risk due to favourable conditions of the site, such as: reservoir formation depth, thickness and seal lateral continuity. However, special attention should be given to risk scenarios such as operational error and well mechanical conditions during the whole site life cycle, which can negatively impact an aquifer. Finally, with appropriate risk assessment management, the risks of unwanted CO
leakage in the pilot onshore storage experiment can be adequately controlled and minimised.
Keywords: CO 2 geological storage, qualitative risk assessment, risk method, pilot experiment, Brazil