Case Study of Well Intervention Techniques for Productivity Restoration in Watered-Out Wells of the Owena Field, Ondo State, South West Nigeria

Watered-out wells in mature onshore fields represent significant candidates for productivity restoration through targeted intervention techniques, and understanding the hydrodynamic and stratigraphic context of water encroachment is essential for selecting the most appropriate remediation strategy. This study presents a case study of well intervention techniques applied for productivity restoration in watered-out wells of the Owena Field, operated in Ondo State, South West Nigeria. Historical well files including perforation records, production logs, and cement evaluation surveys from eight wells with high water cuts were reviewed to identify the mechanism of water encroachment: casing leaks, channelling behind poor cement, or reservoir-scale water encroachment from the aquifer. Radioactive tracer logs and oxygen activation logs were used to differentiate behind-casing crossflow from reservoir-sourced water. Three categories of intervention were applied: mechanical isolation using inflatable bridge plugs for casing leak scenarios, cement squeeze operations for behind-casing channelling cases, and selective zone reperforations for reservoir water coning management. Post-intervention production data indicate that oil rates increased by an average of 340 barrels of oil per day across the treated well population, representing a cumulative annual production uplift of 1.24 million barrels. The study provides a decision tree framework for intervention candidate selection based on water entry mechanism diagnosis. Keywords: well intervention, productivity restoration, water encroachment, Owena Field, Ondo State.