The Effect of Temperature on the Density and Electrical Resistivity of Sodium Chloride Solutions

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Abstract
This paper is a study of the effect of temperature on the electricalresistivity of sodium chloride solutions based on the published resistivity anddensity data in the International Critical Tables. This temperature effect isof considerable importance in quantitative interpretation of electric logs, where it is frequently necessary to correct mud resistivities measured undersurface conditions to temperatures existing at the bottom of the bore hole. Anempirical approximation formula was developed for this conversion which hasproved to be very useful and seems to provide results well within the range ofaccuracy of the data involved. Introduction: Research by various investigators during the past 20 years has clarified thephysical principles of the phenomena which cause the natural or spontaneouselectric potential in rotary drilled bore holes. In order to calculate the resistivity of the connate water Rw and toestimate its "equivalent salinity" (as NaCl) from an electric log bymeans of this SP relationship from a knowledge of the static self potential andof the resistivity of the mud filtrate Rmf, it is necessary to first correctthe resistivity of the mud filtrate measured under surface conditions to theresistivity of this same mud filtrate in the well bore at a differenttemperature. In order to make this temperature conversion for the mud filtrate thevariation of the electrical resistivity of sodium chloride solutions withtemperature is commonly used. Since some discrepancies were found in the charts.ordinarily used for this purpose, it was felt desirable to make a new study ofthis relationship based on the published measurement data. Because of thefundamental nature of these relationships and as an aid to other workers inthis field, an attempt has been made in this study to show every step in thecalculations. T.N. 195

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