All EOR projects begin with an analysis of the nature, location, and causes of residual oil saturations (''S''<sub>or</sub>) that remain after primary and/or secondary recovery operations. The main factors that control the value of ''S''<sub>or</sub> are pore geometry, rock [[wettability]], and the properties of the displaced (oil) and displacing (injected) fluids. Fluid properties of particular interest are interfacial tension, viscosity, and density. In combination with the heterogeneity of the reservoir, these properties result in the overall recovery (''E''<sub>R</sub>) for any recovery scheme. | All EOR projects begin with an analysis of the nature, location, and causes of residual oil saturations (''S''<sub>or</sub>) that remain after primary and/or secondary recovery operations. The main factors that control the value of ''S''<sub>or</sub> are pore geometry, rock [[wettability]], and the properties of the displaced (oil) and displacing (injected) fluids. Fluid properties of particular interest are interfacial tension, viscosity, and density. In combination with the heterogeneity of the reservoir, these properties result in the overall recovery (''E''<sub>R</sub>) for any recovery scheme. |