Chap. 11] 



GEOPHYSICAL WELL TESTING 



839 



depth. One of the earliest accounts of rock temperatures m mine workhigs 

 was given by Athanasius Kircher in 1665, but about 150 years elapsed 

 before systematic underground observations were conducted in England, 

 Germany, and France. Reliable temperature measurements in wells were 



OCPTita m rcc 



<D 





Mi 



Ml 



x::s. 



JLL 



OIL pnooucrivc oil 



Fig. 11-14. Correlation between productivity of oil horizons and electrical resis- 

 tivities in the Grozny field, Russia (after Schlumberger) . 



made possible by the development of overflow thermometers in 1830. In 

 the eighties, this was followed by a systematic inquiry into the influence 

 of rock conductivities and of other factors. With progress in well drilling 

 (see Fig. 11-15), much material was accumulated after the turn of the 

 century and was made the object of exhaustive studies by Van Orstrand, 



