BORE-HOLE INVESTIGATIONS 



1059 



point) is obtained by adjusting the second coil so that its induced E.M.F. will reduce 

 the E.M.F. of the first coil to the desired amount. (See page 613). 



The Induction Log — Sensitivity Scales. — In logging practice, the resistivity unit 

 is the ohm-meter. The corresponding unit of conductivity is its reciprocal, the mho per 

 meter.'f As the usual range of formation conductivities expressed in mhos per meter 



OSCILLATOR 



:illolor housing 



Fig. 654. — Inductive logging apparatus. A, schematic; B, general 

 apparatus arrangement. 



would involve extensive use of fractional values, it is preferred to use a smaller unit, 

 the millimho per meter. 



With this unit : 



Conductivity 



(in millimhos per meter) 



1000 



Resistivity 

 (in ohm-meters) 



For illustration, a bed having a resistivity of 100 ohm-meters would thereby have 

 a conductivity of .01 mhos per meter, or 10 millimhos per meter. 



t Mho is ohm spelled backward. 



