DEEP BOREHOLE SURVEYS 

 AND PROBLEMS 



CHAPTER I 

 DEVIATION AND ITS CAUSES 



The primary purpose of a borehole survey is to determine 

 the extent of the borehole in length and deviation. The 

 deviation is surveyed in angular deflection in amount and 

 bearing; the amount relative to the intended initial direc- 

 tion and the bearing with respect to the local meridian or 

 any other fixed reference mark. 



In many boreholes frequently only the amount of deflec- 

 tion suffices. Thus in exploratory borings in unknown 

 measures the direction of deflection is of less value than the 

 degree of deflection, owing to the remainder of the data 

 being absent from our conclusions. However, for a correct 

 decision respecting the strata penetraited, this knowledge 

 is unconditionally necessary. 



Still more important are these determinations when 

 the hole has to hold a pumping or bailing plant, as in certain 

 petroleum borings. Here the longevity of the borehole is 

 in considerable degree influenced by any noteworthy devia- 

 tion from the plumb. Rods, or the bailing rope, con- 

 tinually chafe in the same part of the casing; in a short 

 time it becomes seriously injured. That all deep boreholes 

 deviate — and by deep boreholes we imply all those over 

 1,000 ft. in extent — is established beyond any doubt, and 

 indeed much shallower boreholes deviate in more or less 

 degree. 



Dr. Otto Stiitzer of Kiel has recently cited a case^ where 

 two boreholes in the Moreni oil field of Rumania, com- 



1 Z. deut. geol. Ges., Bd. 81, Heft 10, p. 536 1929. 



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