Use of Polymers to Recover Viscous Oil from Unconventional Reservoirs – 2009

R.S. Seright – 2009

Abstract

First year of a three-year project on polymer flooding for viscous oil recovery on Alaska’s North Slope. Fractional flow calculations and reservoir simulation (ECLIPSE, VIP, UTCHEM) assess polymer flooding of viscous oils (1 to 100,000 cp). For 1 pore volume of polymer injection in a two-layer free-crossflow system, oil recovery increases as the more-permeable layer becomes thicker. A preliminary economic analysis shows polymer flooding provides higher relative profit than waterflooding over a significant throughput range. Maximizing polymer solution injectivity is identified as the critical factor for economic viability. ECLIPSE simulator requires specific formatting to produce credible fractional flow predictions for the free-crossflow case.

Key Takeaways

  • Polymer flooding provides higher relative profit than waterflooding for 1000-cp oil over a significant throughput range — establishing preliminary economic justification for North Slope applications.
  • Maximizing polymer solution injectivity is identified as the single most critical factor for economic viability of polymer flooding in viscous-oil unconventional reservoirs.
  • ECLIPSE simulator requires careful formatting to obtain credible free-crossflow predictions in layered reservoirs — standard default settings can produce non-physical results.
  • For two-layer systems with free crossflow, oil recovery for 1 pore volume polymer injection increases as the more-permeable layer becomes thicker relative to the less-permeable layer.
  • Without crossflow, large pore volume throughputs are needed to achieve high recovery even with viscous polymer solutions — short polymer slugs show limited performance.
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