Evolution of Non-Routine Integrated Well Works for North Sabah

Abstract A description on the approach taken by the operating company to increase quantity and complexity of non-routine well intervention activities while maintaining cost effectiveness in an offshore mature brownfield asset in Sabah waters, which had been producing under another operator since 1979. Due to the age of the asset, the four producing oil fields in the asset have severe pressure depletion, relatively low production rates, organic and inorganic scales and sand production challenges to be overcome. The operator first focused on improving well integrity management while simultaneously seeking to increase the company knowledge and experience on less complex well intervention activities before building up to more complex activities over a four-year period. The well integrity management strategy was optimised by implementing one comprehensive and one condition-based maintenance cycle conducted annually with corrective maintenance planned out in between the preventive maintenance activities. The operator conducted a comprehensive review on the production enhancement opportunities and selected the most easily achievable ones for fast execution, mostly those which could be conducted through slickline intervention alone, before expanding intervention operations to more complex opportunities. After two years of the revised well integrity strategy implementation, a trend of the typical integrity failures and their frequency had been established, which was then used to update the critical sparing philosophy and internal well integrity management systems. Once the asset well integrity had been improved, more complex non-routine intervention was planned and executed, this started with chemical pumping and slickline services supported by a vessel for additional bedding for organic and inorganic scale remediation. Due to significant logistical challenges, subsequent campaigns utilised a larger vessel with a crane to avoid reliance on the jacket cranes with limited and derated capacities. Starting from the third year of operating the assets, the operator successfully planned and executed Coiled Tubing, Pumping and Slickline interventions supported by an Accommodation Workboat for acid stimulation, coiled tubing sand clean out and most recently for coiled tubing and slickline fishing activities. This paper may be used as a guide on how an operator can successfully approach building up well intervention activity frequency and complexity in a mature oil producing asset.