CO2 leakage through existing wells: current technology and regulations

Preexisting wells and well bores are high-permeability pathways through the crust, and as such present zones of elevated risk to CO2 storage projects. Although current well closure and abandonment technology appears sufficient to contain CO2 at most sites, individual wells may suffer from a variety of factors that limit their integrity, including improper cementation, improper plugging, overpressure, corrosion, and other failure conditions. As a whole, wells in the US can be subdivided into three categories: wells that are not plugged, wells plugged before 1952, and those plugged after 1952 (when the American Petroleum Institute standardized plugging procedure and cement composition). After use, wells may be plugged and abandoned, with the liability of leakage remaining with the parent company. However, in some cases wells are orphaned and have no current parent company, leaving liability with the state. Current regulatory frameworks for well completion, plugging, and abandonment may not suffice in accounting for the most likely features, events and processes that affect well integrity after initial CO2 injection.