breaks appear. Then, when a corresponding log is obtained from another well, the 

 validity of correlation can be established. Due to stratal thinning and to varia- 

 tions in structural dip, the footage interval involved in the penetrated section 

 may vary considerably between wells. Emphasis must be placed on the sequence 

 of zones in the overall well profile. 



WELL E 



WELL F 



Figure 7-7. Correlation of thermalogs. 



Only limited sections of logs can be used as examples in this chapter. In 

 every instance where correlation was achieved, it was based not only on the 

 portion illustrated but on overlying and underlying footages. The figures merely 

 serve to exemplify the manner in which correlation is obtained. 



Figure 7-7 is a reproduction of corresponding sections from two DTA logs 

 successfully correlated even though no major breaks appeared. Without attempt- 

 ing to identify the mineral reactions which produce the curves, the following 

 peaks are significantly similar between the wells. 



1. Double low-temperature endothermic peak extending for about 40 feet 

 (1445-1485 feet, well E; 1850-1890 feet, well F). 



2. High-temperature reversal at 1385 feet and 1405 feet, well E and at 1790 

 feet and 1810 feet, well F, with shallower depth of each exhibiting a flat 

 exothermic plateau, while the greater depth shows a sharp peak. 



131 



