A Comparison of FEP-analysis and Barrier Analysis for CO2 Leakage Risk Assessment on an Abandoned Czech Oilfield

Abstract

The storage of CO2 in depleted oilfields is one of the possible measures for reducing CO2 emissions to the atmosphere. In parallel with the technical feasibility study, a risk assessment focusing on storage risk and reliability need to be undertaken prior to CO2 storage. This is to demonstrate that the quality of the storage site, often formulated as the risk of CO2 containment failure, is acceptable. Legislations in various European countries state such risk assessments shall be provided as part of making a decision with respect to accepting a storage site solution. However, the details and the choices on the risk assessment approach itself are often arbitrary. In the REPP-CO2 project, a research cooperation initiative between Czech Republic and Norway, the main goal is to evaluate the feasibility of a storage site in the Vienna Basin, in the southeastern part of the Czech Republic. As part of the REPP-CO2 project, two different approaches have been selected for performing the risk assessment part, namely the features, events and processes (FEP) approach and the barrier analysis approach, to quantify storage risk. This paper elaborates both approaches and presents strengths and weaknesses for each of them, with respect to work process scalability, available analytical modeling tools, their role in a classical risk assessment context, uncertainty treatment, system suitability and their effectiveness with respect to communication of results. To highlight different aspects of comparison, examples from the Czech storage site candidate are also described in the paper.