Miscellaneous Subsurface Methods 



677 



The Electric Pilot 



The electric pilot is an apparatus through which the interface between 

 two liquids with dissimilar electric conductivities can be accurately lo- 

 cated in a well. Primarily the electric-pilot unit is made up of a source 

 of electricity, a circuit consisting of an insulated single conductor cable 

 that can be run into a well, and a special electrode assembly that can be 

 run into the well on the cable. A schematic diagram of the unit is shown 

 in figure 364. The cable is carried on a power-driven reel, which together 



ELECTRODE 



-WEIGHT INDICATOR 

 -MEASURE METER 



-INSULATED CABLE 



POWER DRIVEN REEL 



^i 



(5^ 



AMMETER ON EXTENSION CORD 



WELL 



no VOLT A.C GENERATOR 



TRANSFORMER 



Figure 364. Diagram of electric-pilot equipment. 



with the generator and all other auxiliary equipment is truck-mounted as 

 a compact unit. Slip rings and brushes permit completing the electric 

 circuit from the cable mounted on the reel to the generator and recording 

 instruments. 



A diagrammatic view of the electrode assembly is given in figure 365. 

 The instrument consists essentially of a tube several feet long, on the 

 outside of which are mounted two electrodes. The electrodes are com- 

 pletely insulated from the tube. The insulated conductor wire from the 

 cable is connected to the upper electrode, and the upper and lower elec- 

 trodes are connected by means of an insulated wire having a resistance of 

 several hundred ohms. In order to complete the electric circuit in the 

 well, it is, therefore, necessary to establish electric connection between 

 one or both of the electrodes and the body of the assembly. 



The actual operation of the electric pilot is seen by referring to fig- 



