Miscellaneous Subsurface Methods 773 



characteristics of an area, it would be possible to determine the probability 

 of finding commercial oil by drilling in any of the structural or strati- 

 graphic traps in that particular province. This would be an enormously 

 important step in the direction of focusing exploration efforts on those 

 areas most likely to produce the reserves of the future. 



Questions 



1. What is meant by "controlled directional drilling"? 



2. What is a whipstock and what is the purpose of running the device in 

 a drill hole? 



3. Refer to figure 239 ff. for operation of the whipstock. 



4. What is the recommended drift in a directionally drilled well? 



5. Directional wells are of what two types? 



6. What are the applications of directional drilling? 



7. In well surveying what three basic types of instruments are used? 

 What are the principles of each? 



8. For what reasons are wells surveyed? 



9. What is the basic principle of magnetic-core orientation? 



10. What geologic variables must be considered in a magnetic-core orien- 

 tation? 



11. Discuss the practical applications of magnetic-core orientation. 



12 How are oriented cores taken with the conventional-core barrel? With 

 the wire-line retractable-coring equipment? 



13. Upon what principle are dipmeter surveys based? 



14. How are dipmeter levels selected in a well? 



15. Give several applications of dipmeter surveys. 



16. What are the five general types of coring procedures? 



17. What are the advantages of conventional coring? Disadvantages? 



18. What are the advantages of diamond coring? Disadvantages? 



19. What are the advantages of wire-line coring? Disadvantages? 



20. What are the advantages of reverse-circulation coring? Disadvan- 

 tages? 



21. Give the advantages and disadvantages of side-wall coring. 



22. How may the geologist use coring data to advantage? 



23. How does information obtained from cores assist in the evaluation 

 of the electric-log profile? 



24. What is the basic geometry of tricone bits and what is the purpose 

 of such construction? 



25. What are the advantages of using several drill collars during drilling? 



26. What is the optical system and general principle of operation of the 

 deep-well camera? 



27. Two types of deep-well-camera surveys are made. Discuss each. 



28. The electric pilot is used for what three purposes in oil-field comple- 

 tions and remedial work? 



29. What are some of the reservoir and well conditions under which 

 selective acidizing should be considered? 



