The Electrical Conductivity of Sea Water

Determination of the Relationships of Electrical Resistivity, Sound Velocity, and Density/Porosity of Sediment and Rock by Laboratory Techniques and Well Logs from Deep Sea Drilling Project Sites 415 and 416 off the Coast of Morocco

“…If the sediment consists of nonconducting minerals, the electrical conduction is primarily through the interstitial water, whose conductivity varies with temperature, pressure, and salinity (Home, 1965;Home and Courant, 1964;Home and Fry singer, 1963;Thomas et al, 1934). However, conduction through the fluid can be modified significantly if metallic minerals are present with appreciable conductivity, or clay-type minerals that exchange or withdraw ions from the interstitial water (de Witte, 1950a,b;Patnode and Wyllie, 1950;Keller, 1951;Berg, 1952;Winsauer and McCardell, 1953;Wyllie, 1955).…”

“…Thus the interstitial fluid may have a different chemical composition from that of the original interstitial sea water (Siever et al 1961;Siever et al, 1965). Therefore, the electrical resistivity of the interstitial water determined, for example, by using data of Thomas et al (1934) may be in error, because these investigators assumed a chemical composition like that of seawater.…”

“…The in situ salinities were estimations based on interpolations between a few salinity measurements on Legs 41 (Couture et al, 1978) and 50 (Gieskes et al, this volume). In situ resistivities of the interstitial water were calculated using the Thomas et al (1934) resistivitysalinity-temperature chart. These resistivity values were then corrected by hydrostatic pressure, using equations of Home and Frysinger (1963).…”

“…The wetbulk density from the FDC was completely corrected using the Schlumberger (1972) Log Interpretation Charts, assuming a 12-inch (30-cm) hole diameter, and the porosity was calculated assuming a 2.7-g/cm3 grain density and a 1.032-g/cm3 water density (typical density). When salinity became greater than 40.9 per mill, the R calculations were discontinued, as the Thomas et aL (1934) charts ended at 41 per mill salinity. It may have been possible to extrapolate the Thomas data or use the sodium-chloride salinity charts from the Schlumberger manual, but we did not want to introduce any additional uncertainties into the scatter diagrams of F versus porosity.…”

“…he hydrostatic pressure was calculated as = (depth below sea level) X (1.035 g/cm^). Electrical resistivity was calculated from the temperature and salinity based on Thomas et al (1934) and the corrected for hydrostatic pressure by Home and Frysinger (1963) techniques. Warren, 1966).…”