Miscellaneous Subsurface Methods 523 



cup similar to that used with the drift indicator, except that it is free to 

 rotate. A small magnet is attached to the bottom of the cup. When the 

 orientation instrument is positioned so that the magnetic disc cup is be- 

 tween the magnets of the substitute, a picture is taken with the instrument. 

 The spot on the disc indicates the low side of the hole. The instrument and 

 barrel are withdrawn from the hole and the unit, with the disc in place, 

 is unscrewed from the instrument and placed in a reader (fig. 253). This 

 reader is constructed with two magnets in exactly the same relation that 

 they have in the drill-pipe substitute. The angular relation between the 

 face of the whipstock and the low side of the hole is obtained by means 

 of the reader. The drill pipe is turned the required amount, either right 



DISC 



MAGNETIC 

 DISC CUP 



DOT ^fr/f^^^m^\/ 



Figure 252. Magnetic orienting unit. 



or left, to correct for this difference. In this way the tool is faced in the 

 desired direction. A check on the orientation should be made by running 

 the instrument a second time, after the pipe has been turned. If a check 

 reading is taken, this method is considerably slower than the alignment 

 method of orientation when used at shallow depths. 



Typical deflection tools and the methods of orienting them into the 

 well have been considered. The art of directional drilling consists not 

 only in the employment of such tools, but in directing a well to an ob- 

 jective throughout its whole course by a knowledge of directional-drilling 

 practices. Some directionally drilled wells are very shallow; others have 

 been drilled to great depth. The carrying out of a successful directional- 

 drilling job calls for careful planning and consideration of the great 

 number of factors involved. 



Subsurface geologic conditions in the area where the work is to be 



