The basic purposes of chemical flooding are to add a material (chemical) to the water being injected into a reservoir to increase the oil recovery by (1) increasing the water viscosity (polymer floods), (2) decreasing the relative permeability to water (cross-linked polymer floods), or (3) increasing the relative permeability to oil and decreasing ''S''<sub>or</sub> by decreasing the interfacial tension between the oil and water phases (micellar and alkaline floods). The process is depicted schematically in [[:file:enhanced-oil-recovery_fig1.png|Figure 1]]. Chemical additives to reduce interfacial tension are detergent type compounds such as petroleum sulfinates and are so expensive that chemical floods are often technical successes and economic failures. Successful design of chemical floods always revolves around minimizing the amount of chemicals needed to achieve the desired change in interfacial tension and/or mobility ratio.<ref name=pt10r28>Shah, D. O., Schechter, R. S., 1971, Improved oil recovery by surfactant and polymer flooding: New York, Academic Press.</ref> | The basic purposes of chemical flooding are to add a material (chemical) to the water being injected into a reservoir to increase the oil recovery by (1) increasing the water viscosity (polymer floods), (2) decreasing the relative permeability to water (cross-linked polymer floods), or (3) increasing the relative permeability to oil and decreasing ''S''<sub>or</sub> by decreasing the interfacial tension between the oil and water phases (micellar and alkaline floods). The process is depicted schematically in [[:file:enhanced-oil-recovery_fig1.png|Figure 1]]. Chemical additives to reduce interfacial tension are detergent type compounds such as petroleum sulfinates and are so expensive that chemical floods are often technical successes and economic failures. Successful design of chemical floods always revolves around minimizing the amount of chemicals needed to achieve the desired change in interfacial tension and/or mobility ratio.<ref name=pt10r28>Shah, D. O., Schechter, R. S., 1971, Improved oil recovery by surfactant and polymer flooding: New York, Academic Press.</ref> |