438 



EXPLORATION GEOPHYSICS 



Fig. 263. — Resistivities plotted against oil-water compositions. Curve B is a more 

 detailed plot of the lower part of curve A. The insert shows curve A drawn with a loga- 

 rithmic ordinate scale. (Jakosky and Hopper, Geophysics.) 



lytic. Practically all rocks are porous f and contain moisture, and it is 

 due to this moisture that rocks are fair conductors despite the fact that 

 their constituent minerals (quartz, feldspar, etc.) are poor conductors, or 

 even excellent insulators. 



Laboratory studies of both petroliferous and non-petroliferous rocks 

 have shown that for high values of moisture content, the conductivity 



t A report on sand porosity studies is given by C. S. Slichter, "Theoretical Investigation of 

 the Motion of Ground Waters," U. S. Geol. Survey, 19th Annual Report, Part 2, 1897-1898. See 

 also L. C. Uren, Petroleum Production Engineering (Oil Field Exploitation) (McGraw-Hill, 

 1939) p. 5. 



