Rw vs. Temperature with Concentration and Density Outputs

This crossplot is used to temperature correct reference water resistivity (Rw) values and to estimate the equivalent NaCl salinity (ppm).

Input a known Rw and the associated reference temperature. Also enter the reservoir temperature that you would like to output a temperature corrected Rw for. Solution density and concentration of NaCl in mg/L and ppm at 25 deg. C (77 deg. F) are also presented as calculated outputs. Many use NaCl mg/L and NaCl ppm interchangeably, which is reasonable for low salinities, but not with high salinities. The concentration of NaCl in ppm equals the concentration of NaCl in mg/L divided by solution density at the reference temperature.

Inputs are highlighted in yellow and outputs are in green.  Both reference and reservoir temperatures must be entered in degrees Celsius, degC=5/9*(degF-32). The associated data points are plotted on the cross plot.

The Rw to salinity model used above (for the concentration outputs) matches Schlumberger's Gen 9 Chart data very closely to a salinity of 150,000 ppm NaCl. The model assumes that there are only two ions in the water (Na+ and Cl-) and that there is an ion balance.

References

Arps, J.J., "The Effect of Temperature on The Density and Electrical Resistivity of Sodium Chloride Solutions." Petroleum Transactions Of The AIME Volume 198, Technical Note 195, 1953.

Schlumberger's Industry Publication, "Log Interpretation Charts." Gen-9  Chart from 2000 Edition.