Reducing Water While Preserving Oil: A Case Study Retrofitting Vertical Wells with Autonomous Inflow Control Devices

Abstract

Mature vertical oil wells frequently experience increasing water production as a result of water coning, reservoir heterogeneity, and preferential inflow from high-mobility water-bearing intervals. The resulting increase in water handling and artificial-lift requirements can substantially increase operating costs and accelerate the economic limit of wells that may still contain recoverable oil. This paper presents the design, implementation, and post-installation performance of Autonomous Inflow Control Device (AICD) retrofit completions installed in vertical wells in a mature North American oil field. The retrofit solution consists of AICD completion subs incorporating debris filtration and strategically positioned across the producing interval. Where required, isolation between inflow-control sections is incorporated to establish effective compartmentalization and enable the AICDs to modify the local pressure and inflow profiles. Wellbore modeling was used during candidate evaluation and completion design to assess reservoir inflow, water-production behavior, AICD configuration and pressure-drop requirements, and the expected economic benefit of the retrofit. Unlike conventional AICD applications in horizontal wells, these mature vertical wells present additional challenges associated with limited producing intervals, water coning, uncertain water-entry locations, and complex histories of previous completions and production operations. Retrofit installations were performed within existing completion architectures, including slotted-liner and gravel-packed configurations, requiring the AICD design to account for both the existing well geometry and the effectiveness of zonal isolation. Post-installation production data are compared with pre-retrofit performance to quantify changes in oil rate, water rate, water cut, and production trends. The field results demonstrate that appropriately designed retrofit AICD completions can selectively increase resistance to water-dominated inflow while maintaining productive drawdown from intervals containing remaining oil. The resulting redistribution of inflow reduces produced-water volumes without negatively impacting oil production and, in successful applications, enables additional recovery of bypassed oil. The field results demonstrate the potential for retrofit AICDs to provide a practical production-optimization strategy for mature vertical wells approaching their economic limits. By reducing water-handling requirements while maintaining oil production, the technology can decrease artificial-lift and water-disposal demands, extend productive well life, and improve the economics of mature assets without requiring a complete recompletion of the well.