Field studies for de-risking existing wells and CCS site geology

Legacy wells are old exploration and production wells that are penetrating the rock formations in the subsurface. To enable large-scale CO2 and energy storage, these wells must be assessed and monitored to avoid any leakage from the reservoir where the fluids are stored (several hundreds of m to several km depth) to the surface. These wells are usually plugged and cannot be accessed so they have to be assessed from the surface. To do so, we plan to develop new technologies that allow to screen the status of the wells, to monitor them with non-invasive methods and to model potential leakage rates. The second stage will lead to propose methods to mitigate any potential leakage and investigate how these wells can be used as an asset rather than a threat. This will include using this legacy infrastructure to reduce cost for monitoring the fluid movements in the reservoir and anticipating leakages before they possibly happen. Better understanding and monitoring of such wells are crucial for long term safety of the storage complexes and to allow for large public acceptance of such projects which are critical to fight climate change.

CCS is world-wide considered a key measure to keep global warming to 1.5 degrees. CATF reports that by 2030, available CO2 storage capacity will amount to around half the volume of captured CO2. As more storage space is needed, more complex areas need to be considered. For CCS in historical oil and gas regions, containment of CO2 could be jeopardized by leakage along legacy well paths. Without storage in those regions, with well-known and extremely well-suited geological features in addition to potentially reusable infrastructure, world-wide storage capacity would be significantly limited. Primary objective of the LEGACY project is to develop tools and technologies for screening, modelling, monitoring, and mitigation of well integrity issues and leakage, thereby enabling safe and cost efficient, large-scale storage of CO2 in areas with legacy wells. Scientific aims: - Communicate effectively with industry, state regulators and general public on legacy wells threats and opportunities, - Develop an automated workflow for screening of legacy wells, - Demonstrate tools for cost-efficient non-invasive monitoring of well integrity and leakage, - Develop and validate strategies for efficient modelling and prediction of leakage rates, - Develop strategies for mitigation/remediation of well integrity issues, -Explore the possibility of using legacy wells to improve monitoring of storage sites, - Develop recommendations for future well construction and abandonment to facilitate monitoring.