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→How invasion affects rt measurement
==How invasion affects r<sub>t</sub> measurement==
==How invasion affects r<sub>t</sub> measurement==
[[file:predicting-reservoir-system-quality-and-performance_fig9-29.png|thumb|{{figure number|1}}Resistivity profiles of formations with fresh and saltwater mud filtrate invasion.]]
[[file:predicting-reservoir-system-quality-and-performance_fig9-29.png|300px|thumb|{{figure number|1}}Resistivity profiles of formations with fresh and saltwater mud filtrate invasion.]]
During the drilling process, filtrate water from the drilling fluid invades the formation. Its resistivity (R<sub>mf</sub>) is either greater than, less than, or equal to R<sub>t</sub> and can distort deep resistivities. Distortions to resistivities due to invasion must be corrected to get a valid R<sub>t</sub> value. The diagram in [[:file:predicting-reservoir-system-quality-and-performance_fig9-29.png|Figure 1]] shows resistivity profiles of formations with fresh and saltwater mud filtrate invasion.
During the drilling process, filtrate water from the drilling fluid invades the formation. Its resistivity (R<sub>mf</sub>) is either greater than, less than, or equal to R<sub>t</sub> and can distort deep resistivities. Distortions to resistivities due to invasion must be corrected to get a valid R<sub>t</sub> value. The diagram in [[:file:predicting-reservoir-system-quality-and-performance_fig9-29.png|Figure 1]] shows resistivity profiles of formations with fresh and saltwater mud filtrate invasion.