430 



Subsurface Geologic Methods 



the time the sample was caught. Because of the tested accuracy of the 

 measuring system employed and the ability of the instruments to indicate 

 the changes in formations behind casing, radioactivity logs have become 

 a popular means of resolving all manner of measuring discrepancies. 



An additional feature of radioactivity well logging is the collar log, 



Figure 198. Radioactive curves in Branyon field, Caldwell County, Texas. Radio- 

 activity increases from left to right. (Lane-Wells.) 



