Maximizing Production and Cost Optimization in a Remote Carbonate Oilfield through a Standalone Waterflooding System: An Oman North Case Study

Abstract

Oxy's Oman North concession, a remote carbonate oilfield with a gas cap, initially produced under natural depletion, but production declined rapidly due to low reservoir pressure and a weak edge aquifer. To address this issue, waterflooding was deemed necessary. However, the field's location, which was approximately 50 km away from the main production station, posed a challenge because it would require considerable time and cost to install water injection facilities that are connected to the main station and provide the required produced water for injection. To overcome this challenge, a standalone system was designed with surface pumps for water injection. The project was executed within a year at a cost that was about 25% of constructing a water injection header from the station. The system's design included horizontal injectors that were aligned to support horizontal oil producers and prevent the encroachment of the gas cap further downdip. Injection optimization and redistribution of water among the injectors were strategies for maintaining high production and helped to control costs, as they ensured that no injected water or energy was wasted without a return of oil. For example, voidage replacement ratio and diagnostic plots were produced on a monthly basis to monitor the injection performance. The surface network was also optimized using Prosper and GAP modeling tools along with day-to-day monitoring. Wells were choked and opened to maximize production for the entire network. The implementation of these best practices resulted in a significant acceleration of field production. Within the first 18 months, production tripled, and then reached more than five times pre-waterflood rates by 2023. This paper presents an innovative method within the industry that effectively increases production while being cost-efficient. It introduces a pioneering approach that revolutionized production processes, achieved remarkable results, and ensured significant growth in production capacity.