Miscellaneous Subsurface Methods 



521 



are placed in the substitute so that they are in exact alignment with the 

 face of the whipstock. The tool is run into the well on the drill pipe. 

 Just before it reaches the bottom of the hole, a special bottom-hole orien- 

 tation instrument is run down inside the drill pipe and positioned between 

 the magnets of the substitute. This special instrument consists of an East- 

 man type "M" drift-indicator body, onto the bottom of which is screwed 

 a magnetic orienting unit (fig. 252). This orienting unit contains a disc 



«a|>--" 



FACE 

 LINE 



4AGNET 



Figure 250. Bottom-hole-orientation substitute. Whipstock shear-pin hole 

 is in back opposite face magnet. 



