Inaccessible/Abandoned Wells by Efe Kermen and Sjef Meekes

Underground storage of CO2 in depleted oil reservoir and deep saline aquifers is considered as an efficient way of reducing greenhouse gas emissions. Ensuring the safety and integrity of the storage site is crucial for such an operation. Abandoned wells have been identified as the biggest threat to the integrity of CO2 underground storage sites, mainly due to concerns about the regulations and industry standards at the time of abandonment. Another issue is that abandonment might have been performed due to problems that occurred during the life cycle of a well which indicate reduced integrity in the first place. Continuous monitoring is needed throughout the project to confirm that the integrity of wells in the storage compartment has been maintained. This report discusses the risks associated with abandoned wells, evaluates existing technologies to monitor abandoned wells and summarizes options to mitigate fluid flow along or out of abandoned wells if a leak was detected.