Salinity dependence of the thermoelectric coupling coefficient in brine‐saturated sandstones

Abstract

We report measurements of the thermoelectric coupling coefficient in intact sandstone samples saturated with NaCl brine at concentrations ranging from 1 × 10−4 to 1 M. Our measurements account for temperature‐dependent electrode effects. We also present a model for the salinity dependence of the thermoelectric coupling coefficient which yields a close match to the experimental data. At low salinity, the measured coupling coefficient exhibits the salinity dependence predicted for a perfect membrane, while at high salinity, the coupling coefficient follows that predicted for an uncharged porous medium. Measured values of the coupling coefficient range from 0.370 mVK−1 at low salinity (1 × 10−4 M), to 0.055 mVK−1 at high salinity (1 M).