Polymer Flooding Definition / Meaning

Polymer flooding is a chemical enhanced oil recovery (EOR) method used to improve the efficiency of waterflooding in oil reservoirs. By adding small amounts of water-soluble polymers (typically polyacrylamide or biopolymers) to the injection water, the viscosity of the water phase increases significantly. This reduces the mobility ratio between the injected water and the oil, leading to a more stable displacement front and a higher sweep efficiency. As a result, polymer flooding can recover additional oil beyond what conventional waterflooding can achieve, especially in heterogeneous or high-viscosity oil reservoirs.

How Polymer Flooding Works

The key principle behind polymer flooding is the improvement of the mobility ratio (M), defined as the mobility of the displacing fluid (water) divided by the mobility of the displaced fluid (oil). A favorable mobility ratio (M less than 1) means the oil can move more easily than the water, reducing the tendency for water to finger through oil and by-pass it. Adding polymers thickens the water, lowering its mobility, and thus improving the sweep efficiency both areally and vertically. The polymer also reduces the permeability of the rock to water (residual resistance factor), further slowing the water and improving oil recovery.

Key Polymers Used