Very probably the first intentional use of directional drilling was to by -pass 

 lost tools or other junk in a well. After failing to retrieve the lost material by 

 fishing, the driller would by-pass the obstacle by deflecting the bit with a crude 

 whipstock. By this method the driller was able to salvage the portion of the well 

 above the obstacle and minimize redrilling costs. This early whipstock was 

 generally a tapered piece of timber which could be left in the hole after it had 

 served its purpose. The setting of a more modern whipstock to by-pass lost tools 

 in a well is still one of the commoner applications of directional drilling. 



The Huntington Beach Oil Field in California was the site of the first ex- 

 tensive application of controlled directional drilling. This field, which extends 

 from the shore oceanward about two miles, presented a problem in development 

 which was solved by drilling directional wells from on-shore locations to sub- 

 surface bottom locations under the ocean. The many technical problems in- 

 volved in the successful drilling of these wells (i.e., prevention of abrupt changes 

 in drift and direction, avoidance of collision of drilling wells with older pro- 

 ducing wells, etc.) accelerated the development of better techniques and instru- 

 ments for well control and surveying. 



WELL SURVEYS The techniques of directional drilling did 



not begin to assume their present importance 

 in the oil industry until satisfactory tools for surveying the course of a well 

 were developed. Early attempts at well surveying were crude, but they did give 

 an indication of the inclination and direction of the hole. One early type of 

 deviation survey was made with a weak solution of hydrofluoric acid in a glass 

 bottle. The bottle containing the acid was lowered to the bottom of the hole 

 and allowed to sit for 10 or 15 minutes, long enough for the acid to etch the 

 glass. When removed from the well, the etched bottle gave an indication of the 

 angle of inclination of the hole from the vertical, but not the direction of the 

 inclination. 



A modification of the hydrofluoric acid technique involved the use of a 

 magnetic needle floating in gelatin. This arrangement was lowered into the 

 hole and allowed to sit until the gelatin hardened. The inclination of the surface 

 of the gelatin in the container thus gave an indication of the angle of the hole, 

 and the orientation of the magnetic needle gave an indication of the direction 

 of the hole. 



Neither of the above early methods gave any assurance to the operators 

 that they were measuring the true inclination of the hole. Erroneous readings 

 were often caused by the jamming of the devices against the side of the hole 

 or against an obstacle. 



Three basic types of well surveying instruments are now in common use: 

 (1) drift indicators, (2) single-shot instruments, and (3) multiple-shot instru- 



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