52 



DEEP BOREHOLE SURVEYS AND PROBLEMS 



This last item of check is probably the most important 

 aspect of accuracy. If possible the method being adopted 

 should be checked later by methods dependent on a 

 totally different operating principle. Then the results 



Derrick Floor 



Plan View of oinOil Well 

 ComparingResulis of Several Surve\/s 



Derrick^ -^ 

 Floor I 



depth 



Fig. 24. — Plan of an oil well comparing Fig. 25. 



results of several surveys made under 

 varied conditions. {After Macready.) 



could be compared graphically as in Fig. 24 (after R. P. 

 McLaughhn) ^ Faihng this a check survey should be made 

 in and out of the borehole as in Fig. 25. ^ The manner of 

 compiling a check will be seen from Table VIII, wherein 



1 By the courtesy of Bull. Amer. Assoc. Petroleum Geol. (Vol. 14, No. 5, 

 p. 586, 1930). 



2 Ibid., p. 588. 



