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A FORTRAN algorithm for correcting normal resistivity logs for borehole diameter and mud resistivity

January 1, 1978

The FORTRAN algorithm described in this report was developed for applying corrections to normal resistivity logs of any electrode spacing for the effects of drilling mud of known resistivity in boreholes of variable diameter. The corrections are based on Schlumberger departure curves that are applicable to normal logs made with a standard Schlumberger electric logging probe with an electrode diameter of 8.5 cm (3.35 in). The FORTRAN algorithm has been generalized to accommodate logs made with other probes with different electrode diameters. Two simplifying assumptions used by Schlumberger in developing the departure curves also apply to the algorithm: (1) bed thickness is assumed to be infinite (at least 10 times larger than the electrode spacing), and (2) invasion of drilling mud into the formation is assumed to be negligible.

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Publication Year 1978
Title A FORTRAN algorithm for correcting normal resistivity logs for borehole diameter and mud resistivity
DOI 10.3133/ofr78669
Authors James Henry Scott
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Open-File Report
Series Number 78-669
Index ID ofr78669
Record Source USGS Publications Warehouse