Qatar Petroleum's super-giant Dukhan field located onshore Qatar has a mature inventory of hundreds of wells. Managing integrity of such mature well inventory to avoid unplanned downtime has been no less crucial than any other activity to maximizing production and injection. This involves costly wellwork decisions for integrity control and repair, which rely heavily on data obtained from a well integrity monitoring program. Well integrity monitoring program ranges from using basic methods to state-of-the-art downhole monitoring tools. Their applications are almost always associated with limitations that impose uncertainty in well integrity evaluation. This paper presents an integrated approach Qatar Petroleum used to address this issue. This approach consisted of performing reliability assessment of the entire array of available tools and methods against given well conditions with a matrix of assessment criteria. This matrix enabled selection of a fit-for-purpose set of tools and methods with clear understanding of their strengths and limitations. Techniques of correlation, bracketing and elimination were then applied to analyze the outputs obtained from using the selected set of tools and methods. The approach allowed detecting well integrity problems and determining their severity with minimal uncertainty. The paper focuses on intricacies of the approach, and how its implementation results in a sound well integrity evaluation. It also presents field examples that demonstrate efficacy of the approach in supporting costly wellwork decisions for restoring well integrity. Successfully restoring the well integrity unlocked revenue potential, made quick payout of the wellwork costs and extended the field life.

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