Chap. 9] 



SEISMIC METHODS 



577 



are correlated from point to point. For preliminary depth calculations 

 an average velocity may be assumed or be determined from surface 

 profiles. However, for most areas accurate values derived from well 

 shooting are now available. 



1000 



mo 



StaLmI 



</ef Iff/ft phase 

 9tmidtfinitt phase 

 indefinite phase 



.--"' 



(1 — 

 <i — 



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-d-^ __ 











!>. i! 



~-(l^. 



ir 





~<>^— ~ 



(I— 



--^.r^^'-^-ri-"^' 



— o- 



"^ "[],-.' >-"<! 



— -<r 







-—-"■ 



'•T — ■ 



—■'>-"■ 



^--"""'' 



-. — -<• 



-J ►---'' 



J I — 



l/eeff 



Fig. 9-92. Reflection correlation (phase) logs. 



Records are generally calculated in the field office; some companies 

 make it a practice to send duplicate records to headquarters. The field 

 crew keeps the following records and turns them in to the field ofl&ce at 

 the end of the day's work : (a) Driller's notes, containing data on location 

 of shot holes, formations encountered, depth of hole, depth of casing, and 



