Miscellaneous Subsurface Methods 



573 



taken (usually at 100-foot intervals) as the line is being drawn out of 

 the \fe\\. Conductor-cable runs are made with a survey instrument similar 

 to that described, except that neither batteries nor an instrument watch is 

 used. When a reading is required, a button that is pushed on the surface- 

 control panel puts the machine in operation for one cycle, takes a photo- 

 graph of the angle unit, and winds the film (fig. 295). This method of 

 running a magnetic survey is very rapid. 



Figure 294. Making up multiple-shot barrel on drill pipe preparatory to running 



survey. 



Oriented surveys are made in a cased hole, where lost tools have been 

 forced into the wall of the hole, or in sidetracking operations near casing. 

 The magnetic compass in the instrument-angle unit will not give correct 

 direction readings because of the magnetic properties of the casing. Ori- 

 ented surveys are run on drill pipe or tubing. A few surveys have been 

 oriented on sucker rods inside two-inch upset tubing by a special survey 

 machine with fairly successful results. 



When an oriented survey is made, the rotation of the drill pipe as 

 it is run into the well is measured and recorded for each stand. Measure- 

 ment is made during the time in which the pipe is held motionless when 

 the instrument is taking a picture. The instrument and barrel are faced 

 initially in a known direction by a sighting device that fits into the tapered 



