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When a well starts to make water, it is necessary to find out where the water is coming from to determine what actions, if any, are needed. Another important reason for sampling and analyzing water is to determine its resistivity (''R''<sub>w</sub>). This value is needed to determine its saturation (''S''<sub>w</sub>) in the producing formation by wireline log analysis. Consequently, some well logging societies have compiled ''R''<sub>w</sub> values for different regions.
When a well starts to make water, it is necessary to find out where the water is coming from to determine what actions, if any, are needed. Another important reason for sampling and analyzing water is to determine its resistivity (''R''<sub>w</sub>). This value is needed to determine its saturation (''S''<sub>w</sub>) in the producing formation by wireline log analysis. Consequently, some well logging societies have compiled ''R''<sub>w</sub> values for different regions.
Water from dry holes is sometimes analyzed for traces of hydrocarbon-related organic compounds, such as organic acids and benzene. If they are found, it suggests that the formation had an oil accumulation in the vicinity.<ref name=pt05r175>Zarella, W. M. 1967, Analysis and significance of hydrocarbons in subsurface brines: Geochimica et Cosmochimica Acta, n. 13, p. 1155–1166., 10., 1016/S0016-7037(67)80054-1</ref>
Water from dry holes is sometimes analyzed for traces of hydrocarbon-related organic compounds, such as organic acids and benzene. If they are found, it suggests that the formation had an oil [[accumulation]] in the vicinity.<ref name=pt05r175>Zarella, W. M. 1967, Analysis and significance of hydrocarbons in subsurface brines: Geochimica et Cosmochimica Acta, n. 13, p. 1155–1166., 10., 1016/S0016-7037(67)80054-1</ref>
Water for subsurface injection should be carefully filtered and analyzed for its chemical composition. Injection water is filtered because it must be free of suspended matter that might plug the rock pores or coat the faces of the grains. This matter might be bacteria or algae and can be mitigated by including bactericides in the water. Harmful matter can also arise from corrosion of the steel pipes, so it is customary to keep dissolved oxygen out of the injection water. (For information on corrosion and scale, see [[Production problems]].)
Water for subsurface injection should be carefully filtered and analyzed for its chemical composition. Injection water is filtered because it must be free of suspended matter that might plug the rock pores or coat the faces of the grains. This matter might be bacteria or algae and can be mitigated by including bactericides in the water. Harmful matter can also arise from corrosion of the steel pipes, so it is customary to keep dissolved oxygen out of the injection water. (For information on corrosion and scale, see [[Production problems]].)