Evaluation of current logging tools

Carbon capture and storage (CCS) is planned to take place in deep seated geological formations such as aquifers, coal seams or in depleted oil and gas fields. However, many uncertainties still exists regarding the long-term integrity of the reservoirs and how CO2 may leak out from the storage formations back to the surface. A possible leakpath is through active or abandoned wells. Within the wells, CO2 may leak through pre- existing leakpaths such as a poorly cemented annulus, micro annulus, leaking tubing or through the cement used to line and/or plug the well. Therefore, the confirmation of the integrity of the wells becomes of upmost importance. This report reviews the current industry practices for material selection and maintenance of the wells and evaluates the various monitoring and diagnostic tools for a qualitative assessment of the well integrity.