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[[file:preprocessing-of-logging-data_fig1.png|thumb|{{figure number|1}}Determination of true resistivity (''R''_t) from dual induction.]]

[[file:preprocessing-of-logging-data_fig1.png|300px|thumb|{{figure number|1}}Determination of true resistivity (''R''_t) from dual induction.]]

The logging service company chart books contain correction charts for most logging tools and instructions for their use. Users of well log data should become familiar with these so that they can either apply the corrections or recognize the environmental conditions where corrections are not significant. Table 1 gives a summary of environmental corrections for common logging tools emphasizing the conditions for which corrections can be large. Table 1 also contains a partial list of recent service company charts used for typical corrections.<ref name=pt04r19>Welex, 1985, Welex log interpretation charts: Houston, TX.</ref><ref name=pt04r4>Dyos, C. J., 1987, Inversion of induction log data by the method of maximum entropy: SPWLA 28th Annual Logging Symposium Transactions, Paper T.</ref>a, b; <ref name=pt04r20>Western Atlas International, 1985, Atlas log interpretation charts: Houston, TX.</ref> Older tools may require the use of older chart books. Slim hole models available for some tools may require their own specific charts. The user must become familiar with log headings to identify tool models so that the correct chart can be selected.

The logging service company chart books contain correction charts for most logging tools and instructions for their use. Users of well log data should become familiar with these so that they can either apply the corrections or recognize the environmental conditions where corrections are not significant. Table 1 gives a summary of environmental corrections for common logging tools emphasizing the conditions for which corrections can be large. Table 1 also contains a partial list of recent service company charts used for typical corrections.<ref name=pt04r19>Welex, 1985, Welex log interpretation charts: Houston, TX.</ref><ref name=pt04r4>Dyos, C. J., 1987, Inversion of induction log data by the method of maximum entropy: SPWLA 28th Annual Logging Symposium Transactions, Paper T.</ref>a, b; <ref name=pt04r20>Western Atlas International, 1985, Atlas log interpretation charts: Houston, TX.</ref> Older tools may require the use of older chart books. Slim hole models available for some tools may require their own specific charts. The user must become familiar with log headings to identify tool models so that the correct chart can be selected.