Permanent decommissioning of 1000’s of wells occurs annually in Western Canada. Long term sealing of wellbores requires proper placement of sealing materials, avoidance of contamination/mixing and ensuring a good hydraulic bond of the cement to both steel and surrounding rock. Industry best practices, regulatory requirements and technology roadmaps need to be based on sound scientific knowledge of the complex defining mechanics, flow processes and materials performance, as well as field-based data, measurement and monitoring. This project delivers this underlying knowledge as its key objectives, building on the success of Phase I and aligned with knowledge gaps and policy issues identified by PTAC-AUPRF, Directive 020, IRP27 (Wellbore Decommissioning) and the TRM (Technology Roadmap to Improve Wellbore Integrity). The project utilizes infrastructure established in Phase I and addresses sub-projects in 7 complementary areas: dump bailing, off-bottom plugs placement, sequential cleaning and cementing, and squeeze cementing methods, together with modeling well leakage and data analysis of identified well types. New areas include study of alternate cementitious materials and steel-cement bonding mechanisms.