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Leak Risk Assessment for Plugged Wells in Carbon Sequestration Projects

Abstract Carbon sequestration is considered a promising method to mitigate the accumulation of greenhouse gases. Depleted oil and gas reservoirs are a desirable vessel for carbon sequestration. It is crucial to maintain the sealing ability of formations with high concentrations of CO2. Plugged wells are one of the risky leakage pathways and leakage defects the purpose of carbon sequestration. The performance of a plugged well must be monitored and evaluated through the whole lifetime of carbon sequestration. Much research is focused on well integrity assessment for carbon sequestration projects, however, a systematic manner addressing the CO2 leakage risk of plugged wells has not been presented. This study will fill this gap. Cause and Effect Analysis (CEA) method and Failure Mode and Effects Analysis (FMEA) method are used in this paper. CEA is used to identify the causes of plugged wells leakage, while FMEA is used to evaluate the possibility that CO2 will leak from plugged wells. WH field, a CO2 EOR oil field located in the Gulf of Mexico, is studied as an example. CEA and FMEA are effective ways to evaluate the plugged wells leak risk in carbon sequestration activities. This analysis can also be used to assess the integrity of CO2 injection wells and oil production wells of carbon sequestration projects. Through the use of CEA and FMEA, high risk plugged wells are identified.