Annulus Wash and Cement Assurance for Reliable Barrier Placement: Integrating Field Learning in P&A Operations

Abstract Plug and abandonment (P&A) in mature offshore fields is often challenged by poor original cement condition and compromised cement integrity, making reliable annular isolation difficult. While section milling is proven, it is costly, operationally intensive, and adds wellbore risks. Annulus Wash and Cement Assurance (AWCA) is an established and widely applied method worldwide, with a proven track record in restoring annular integrity across various well configurations. This paper builds on that foundation by presenting a multi-well offshore P&A campaign where AWCA was adapted to local field challenges. The objective was to achieve permanent barriers in single casing, dual casing, and limited entry casing application while focusing on adaptive execution strategies and best practices. AWCA was performed across 14 wells to restore zonal isolation above the perforations. A Tubing Conveyed Perforating (TCP) gun was used to create circulation tunnels, followed by a Cup-Type tool to wash and clean the annular space, and effectively place cement across the perforated interval. The workflow combined pre-job logging evaluation, perforation planning, and effective washing strategies, that finally lead to a successful spacer and cementing operation to achieve a permanent barrier. Procedural improvements include refining washing decision tree, optimizing cement volumes, maintaining fluid rheology hierarchy, and incorporating scraper run post-perforation. In a subset of wells, sustained annular pressure (SAP) was observed post-job. A downhole diagnostic tool was deployed to identify potential leak paths and confirm the depth of pressure origin, guiding subsequent remediation activities to restore well isolation. The AWCA methodology successfully achieved annular isolation in most wells, as verified through cement plug tagging, positive pressure testing, and SAP monitoring post-job. In wells where SAP was detected, diagnostics enabled identification of leak paths, allowing for effective remedial actions. Overall success was driven by thorough planning, continuous improvements steps between wells, and effective teamwork and communication between operators and service providers. This work demonstrates a structured AWCA workflow that delivers reliable barriers while reducing operational time and complexity. The approach offers a scalable and a lower-risk alternative to section milling. Lessons learned from this campaign are transferable to other P&A campaigns in mature fields worldwide.