574 



Subsurface Geologic Methods 



hole bored in the bottom bull plug of the survey barrel. A two-man crew 

 with drill-pipe clamps, a derrick telescope, and a special surveyor's transit 

 measures the amount and direction of the turn of each length of pipe as 

 it is run into the well stand by stand. The derrick man sights through the 

 telescope and aligns the clamp upon a distant target (fig. 296). The 

 floor man measures the amount the length of pipe has turned in relation 

 to the target by use of the transit (fig. 297). These pipe-rotation angles 

 are added algebraically to the azimuth of the direction in which the instru- 



FiGURE 295. Running magnetic multiple-shot survey with conductor cable on elec- 

 tronic truck. 



ment was originally faced. Thus the direction of the orienting lug photo- 

 graphed in the angle unit is ascertained for each reading. The equipment 

 used for orienting a survey is shown in figure 298. 



Combination surveys are made when a hole is partly cased. The drill 

 pipe is oriented to obtain directions in the casing, and magnetic bearings 

 are read from the compass when the machine is in open hole below the 

 casing. 



After the survey has been taken, the film is developed, fixed, and 

 dried (fig. 299). It is placed in a special projector (fig. 300), and an 

 enlarged image of each picture ten inches in diameter is projected on a 

 special protractor. The protractor is constructed so that the compass card 



