Abstract

This paper examines the critical challenges of maintaining well integrity when repurposing oil and gas wells for carbon capture and storage (CCS) projects. It outlines geological storage options such as deep saline aquifers, unmineable coalbeds, and depleted oil and gas reservoirs, emphasizing the potential of depleted reservoirs for CO2 storage due to their available data and favorable conditions. A key focus is placed on the risks associated with injecting CO2 into existing wells, particularly the potential for leakage through compromised wellbore integrity. Issues including casing failures, cement degradation, and operational failures during abandonment are discussed. To mitigate these risks, solutions are proposed that focus on material selection, equipment integrity, and effective well monitoring strategies. Successful case studies, including a CO2 production well in Colorado and an offshore CO2-EOR pilot test between Japan and Vietnam, are analyzed to demonstrate how well these solutions were applied in practice. The paper contributes to improving well integrity in CCS, helping to ensure the long-term success of CO2 storage projects and supporting global sustainability goals.

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