A Risk-Based Approach for Well Integrity Management Over Long Term in a CO2 Geological Storage Project

Abstract

Abstract Carbon Capture and Storage, as a solution to mitigate the increase in greenhouse gases emissions in the atmosphere, is still bringing intensive worldwide R&D activities. In particular, significant acceleration of in situ CCS experiments supports technical developments as well as acceptability of this technology. Among the major risks identified to this technology, wells are often considered to be the weakest spots with respect to CO2 confinement in the geological reservoir. Therefore, long-term well integrity performance assessment is one of the critical steps that must be addressed before large scale CCS technology deployment is accepted as a safe solution to reduce CO2 emissions. A risk-based methodology associated with well integrity is proposed within CO2 geological storage. The main objectives of this approach are to identify and quantify risks associated with CO2 leakages along wells over time (from tens to thousands of years), to evaluate risks and to propose relevant actions to reduce unacceptable risks. The methodological framework emphasized the use of the risk concept as a relevant criterion to (i) evaluate the overall performance of well confinement with respect to different stakes, (ii) include different levels of uncertainty associated to the studied system, and (iii) provide a reliable decision making support. For the quantification of risk, a coupled CO2 flow model (gas flow and degradation processes) was used to identify possible leakage pathways along the wellbore and quantify possible CO2 leakage towards sensitive targets (surface, fresh water, any aquifers…) for different scenarios. This approach offers an operational response to some of the challenges inherent to well integrity management over well lifecycle. This paper focuses on the application of the methodology to a synthetic case based on an existing well. The practical outcomes and the added values will be presented:an objective and structured process,scenarios identification and quantification of CO2 migration along the wellbore for each scenario,risk mapping,and operational action plans for risk treatment of well integrity.