EOR of heavy oil polymer on Alaska's North Slope: History matching challenges and solutions in a significant long-term water cut reduction

In 2016, a pilot program in Alaska's Milne Point Field tested polymer flooding for heavy oil recovery. Using four wells in the Schrader Bluff reservoir, it aimed to assess its effectiveness in capturing heavy oil resources. Generally, polymer flooding can boost oil production by 10-15%, typically occurring 6-9 months after injection. However, in this case, it took over 24 months for a polymer breakthrough. The method proved highly effective, consistently reducing water content by over 40% and maintaining a low level below 20% for 18 months. Applying standard simulation methods, like history matching, became challenging due to this prolonged low water cut. The usual history-matching processes focus on relative permeability, permeability corrections, and skin effect modifications. Nevertheless, these alternatives proved ineffective. In response to the extended low water cut in Alaska's North Slope, a unique approach was suggested. This approach entails highlighting the low-end point (Krw) across multiple relative permeability curves and adjusting these values according to the water cut history. Additionally, the method takes into account permeability adjustments, Equation of State on analyzes of oil viscosity, J-function incorporation, and considers the potential for viscous fingering during the process. The pilot program displayed remarkable polymer flooding effectiveness, but its unique performance on the North Slope required a modified history-matching approach to simulate its success accurately.