Enhancing Value of Polymer Flood Project with Proactive Well and Reservoir Management

Abstract

In viscous oil reservoirs, Polymer flooding is often used to improve oil recovery either after a short period of waterflooding or as a tertiary recovery process following extensive period of waterflood. After six years of water flooding in a major reservoir in Sultanate of Oman having viscous oil (90cp), a field development plan was developed to implement polymer flooding in this reservoir with anticipated incremental oil recovery of around 10% over and above that of waterflood. Necessary facilities were constructed, injection and production wells were drilled, completed, converted and the polymer flood project was initiated and ongoing since the last three years through 27 polymer injectors. By implementing proactive Well and Reservoir Management (WRM) strategies, the actual oil recoveries have been better than predicted levels so far. It is demonstrated here that proactive well and reservoir management through proper well and reservoir surveillance and dynamic adjustment of injection and production rates play a very important role in improving the performance of polymer floods as in waterfloods. Well and Reservoir Management (WRM) principles in case of a polymer flood are similar to that of high mobility ratio waterfloods with some additional aspects that are specific to a polymer flood scenario. Polymer chemical costs, its higher viscosity and non Newtonian fluid flow behavior all create unique conditions that are nonexistent in normal waterfloods. This, in turn, dictates the strategies and methods employed to optimize polymer flood performance. This paper details successful implementation of proactive WRM strategy that has played a key role in sustaining production from this polymer flood field to date. It describes the pattern management processes to optimize pattern wise polymer injection and oil recoveries, conformance control measures implemented to increase sweep and oil recovery, innovative surveillance techniques to monitor fracture growth in polymer injection wells and for evaluation and optimization of production/injection profiles. Production wells and facilities issues arising from polymer breakthrough are being addressed to mitigate any adverse effects.

Historical and recent observations in polymer floods: An update review

“…• Workovers and well stimulation to restore well productivity (Al-Kalbani et al, 2014a;Choudhuri et al, 2013;Christopher et al, 1988;Kumar et al, 2016).…”

“…Finally, Haynes, A. K., Clough, M. D., Fletcher, A. J. P., & Weston, S., (2013) reported that the rate at which fracture growth occurred was unknown. Choudhuri et al, 2013;Choudhuri et al, 2014;Koning and Mentzer, 1988;Shuaili et al, 2012;Thakuria et al, 2013;Zwaan and Valdez, 2015). This field was discovered in 1956 and started commercial production in 1980.…”

“…At least 50% of production wells have seen a reduction (5% to 40%) in total liquid rates and reaching more than 50% in some producers. This drop in total liquids (with minimal to no oil gain) corresponds with the high polymer production (>500 ppm) through high permeability streaks and/or fractures (Choudhuri et al, 2013;Thakuria et al, 2013). Strategies to partially restore well productivity include well stimulation with solvents and its combinations with xylene and diesel (Choudhuri et al, 2013).…”

“…This drop in total liquids (with minimal to no oil gain) corresponds with the high polymer production (>500 ppm) through high permeability streaks and/or fractures (Choudhuri et al, 2013;Thakuria et al, 2013). Strategies to partially restore well productivity include well stimulation with solvents and its combinations with xylene and diesel (Choudhuri et al, 2013). Well stimulation treatments have been optimized using mixtures of xylene, diesel, surfactants, and demulsifiers.…”

Optimization of a Large Polymer Flood With Full-Field Streamline Simulation

“…As mentioned by Choudhuri et al (2013), one reason for this is the large amount of polymer required per unit of recovered oil. This affects which patterns to roll out to polymer flooding, how long to inject polymer before incremental gains are compared with base waterflood performance, and what the optimal slug-size and polymer concentration should be.…”