Publications

A-Reservoir is part of the South Oman Salt Basin (SOSB), contains heavy oil with a viscosity of 200 cP and supported by a strong bottom aquifer. It has been developed by multilateral producers positioned 5 meters below the top of the reservoir. However, the significant contrast in the mobilities of water and oil, coupled with the formation of sharp cones, led to a rapid water breakthrough. Consequently, oil production declined to less than one-tenth of its peak rate, leaving a significant amount of oil unswept between cones.

To tackle this problem, polymer flooding is designed to target the remaining oil between the water cones. This is achieved by placing horizontal injectors between the horizontal producers and positioned 10 m above the oil water contact. This arrangement leverages the aquifer's natural pressure to push the polymer slug upwards towards the producers while simultaneously suppressing the aquifer's influx. Consequently, this concept transforms the typically adverse impact of the aquifer into an efficient drive mechanism.

This paper presents the modeling workflow used to simulate water coning and provides detailed insights into the recovery mechanisms associated with this application of polymer flooding. It also derives the optimal design for maximizing economic efficiency. By understanding the recovery mechanisms, this study has optimized the polymer utilization factor through adjustments in polymer slug size, injection depth, polymer viscosity, injection rate and production rate. These optimizations aim to restore oil production to peak rates, resulting in a polymer utilization factor of less than 4 kg/bbl and a unit technical cost (UTC) of less than 20 USD/bbl. Crucially, the insights gained from this study will unlock the bypassed potential in heavy oil reservoirs impacted by strong aquifer coning, transforming them into easily producible resources.