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Near wellbore [[permeability]] reduction, that is, formation damage, can result from the interaction of the reservoir rock with extraneous drilling, completion, [[stimulation]], or enhanced recovery fluids. Rock-fluid reaction can occur from any of the following operations:

Near wellbore [[permeability]] reduction, that is, formation damage, can result from the interaction of the reservoir rock with extraneous [[drilling]], [[completion]], [[stimulation]], or [[enhanced recovery]] fluids. Rock-fluid reaction can occur from any of the following operations:

# Mixing of formation water with extraneous brine in which the total cation concentration is below a critical salinity value

# Mixing of [[formation water]] with extraneous brine in which the total cation concentration is below a critical [[salinity]] value

# Displacement of one brine by another whose divalent cation concentration is lower than the level required to prevent clay dispersion

# Displacement of one brine by another whose divalent cation concentration is lower than the level required to prevent clay dispersion

# Injection or production of fluids at rates exceeding the critical velocity beyond which mobilization of rock fines by mechanical (drag) forces is initiated

# [[Injection]] or production of fluids at rates exceeding the critical velocity beyond which mobilization of rock fines by mechanical (drag) forces is initiated

Both the critical salinity<ref name=Khilar_etal_1983>Khilar, K. C., and H. S. Fogler, 1983, Water sensitivity of sandstones: Society of Petroleum Engineers Journal, Feb., p. 55-64.</ref> and critical velocity<ref name=Gruesbeck_etal_1982>Gruesbeck, C., and R. E. Collins, 1982, Entrainment and deposition of fine particles in porous media: Journal of Petroleum Technology, v. 34, 847-856.</ref> can be determined from laboratory tests. These two damage mechanisms can exist independently or in combination<ref name=Gabriel_etal_1983>Gabriel, G. A., and G. R. Inamdar, 1983, An experimental investigation of fines migration in porous media: Society of Petroleum Engineers Paper No. 12168.</ref>. Therefore, any system of laboratory tests to evaluate only the influence of salinity on flow impairment must be conducted at rates below the critical velocity. Conversely, the critical velocity will vary depending on whether fluids are chemically compatible with the rock.

Both the critical salinity<ref name=Khilar_etal_1983>Khilar, K. C., and H. S. Fogler, 1983, Water sensitivity of sandstones: Society of Petroleum Engineers Journal, Feb., p. 55-64.</ref> and critical velocity<ref name=Gruesbeck_etal_1982>Gruesbeck, C., and R. E. Collins, 1982, Entrainment and deposition of fine particles in porous media: Journal of Petroleum Technology, v. 34, 847-856.</ref> can be determined from laboratory tests. These two damage mechanisms can exist independently or in combination.<ref name=Gabriel_etal_1983>Gabriel, G. A., and G. R. Inamdar, 1983, An experimental investigation of fines migration in porous media: Society of Petroleum Engineers Paper No. 12168.</ref> Therefore, any system of laboratory tests to evaluate only the influence of salinity on flow impairment must be conducted at rates below the critical velocity. Conversely, the critical velocity will vary depending on whether fluids are chemically compatible with the rock.

==Factors influencing rock-water reactions==

==Factors influencing rock-water reactions==