Reversing Severe Depletion in a Late-Start Light-Oil Waterflood Through Field-Scale High-VRR Pressure Recovery

Abstract

The X Field is a light-oil sandstone development producing from the Upper Gharif Formation at approximately 3,100 m TVDSS. The original field development plan was based on an inverted five-spot waterflood pattern with injection scheduled to commence in 2020. However, water injection was delayed until January 2023 due to surface facility constraints, resulting in five years of uncontrolled reservoir depletion. Average reservoir pressure declined from 34,000 kPa to approximately 25,500 kPa — substantially below the bubble point of 32,000 kPa — triggering secondary gas cap development, ESP failures, and a production shortfall exceeding 30% relative to forecast. This paper documents the design and implementation of an accelerated pressure restoration strategy following commissioning of the permanent water injection facility in March 2025. A high voidage replacement ratio (VRR) of up to 2.5 was deliberately adopted to accelerate reservoir fill-up and drive rapid pressure recovery. By end-2025, static pressure surveys confirmed recovery above 30,000 kPa in significant portions of the field, incremental oil gains exceeding 50 m3/d were observed in selected wells, and previously shut-in wells were successfully reactivated. A structured surveillance program; incorporating static pressure surveys, production logging, saturation logging, and water quality monitoring underpinned the waterflood management framework throughout. The results demonstrate that aggressive high-VRR injection combined with disciplined surveillance can rehabilitate a severely depleted light-oil waterflood system and recover project value.