Simulation Study of Polymer Flooding Performance: Effect of Polymer Rheology

The use of enhanced oil recovery methods to improve oil productivity has grown and come to stay in the industry. This is as a result of its ability to improve productivity and sweep efficiency. Waterflooding, the most widely used method to recover oil becomes less effective when the mobility ratio is unfavorable and the displacement efficiency is low. This leads to viscous fingering or channeling that leads to significant bypassing of residual oil.

Augmenting injected water with polymer will increase the effectiveness of a conventional waterflood. However these Polymers used in the industry are pseudoplastic (shear thinning). This property is not a correct reflection of the sweep displacement. Polymer’s non-Newtonian behavior needs to be taken into account for the successful design and evaluation of polymer flooding projects. The objective of this work is to study the performance of polymer rheology on oil recovery under different fluid and rock properties.

This project uses ECLIPSE 100 to study the performance of polymer flooding on oil recovery. Sensitivity runs was made on polymer concentration, polymer injection rate, rock wettability, polymer rheology, heterogeneous reservoir, stratified reservoir with crossflow.

Based on the simulation studies and the hypothetical model built, Polymer flooding and waterflooding case was compared in which there is an increase of oil recovery by 20% over water flooding. Polymer flooding is effective in water-wet rock than oil-wet. This is because an oil-wet formation tends to hold back more oil in its minute pores and produce reservoir water. Increasing polymer concentration will lead to higher sweep but reservoir pressure and economics should be considered. Non-Newtonian polymer leads to lower oil recovery. This is due to the decrease in viscosity at high shear rate as a result of velocity contrast and instability.