Changes

[[file:enhanced-oil-recovery_fig1.png|300px|thumb|{{figure number|1}}Schematic diagram of chemical flooding (alkaline). © U.S. Department of Energy, Bartlesville, Oklahoma.]]

[[file:enhanced-oil-recovery_fig1.png|300px|thumb|{{figure number|1}}Schematic diagram of chemical flooding (alkaline). © U.S. Department of Energy, Bartlesville, Oklahoma.]]

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''_or 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., and R. S. Schechter, 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''_or 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., and R. S. Schechter, 1971, Improved oil recovery by surfactant and polymer flooding: New York, Academic Press.</ref>

This minimization is achieved by preceding the chemical injection with a preflush to buffer the chemicals from reactions with the ''in situ'' water and following the chemical injection with the injection of a polymer solution to maintain a favorable mobility ratio for the flood. One of the major problems with the injection of surfactants and other chemicals into reservoir rock is that the chemicals are surface active. Thus, they have a great affinity for the minerals found in reservoirs, causing adsorption of chemicals from solution onto the rock in great quantities.

This minimization is achieved by preceding the chemical injection with a preflush to buffer the chemicals from reactions with the ''in situ'' water and following the chemical injection with the injection of a polymer solution to maintain a favorable mobility ratio for the flood. One of the major problems with the injection of surfactants and other chemicals into reservoir rock is that the chemicals are surface active. Thus, they have a great affinity for the minerals found in reservoirs, causing adsorption of chemicals from solution onto the rock in great quantities.