FORMATIONS INDICATED 



A Bentonitic Cloy 



B Quartz Sand 



C Lignite 



D Shale 



E. Quartz Sand 



F Conglomerate 



G. Limestone 



H. Dolomite 



I . Pyrite and Dolomite 



J. Sandy Shale 



K. Oil Sand 



OTA- Curvtl 

 IVMtll N? II 



•y — -^ 



y 



-w 



y 



Figure 7-5. Schematic correlation of zones with DTA. 



placement has occurred. For purposes of illustration, various types of common 

 lithologies have been included in the drawing and typical DTA curves repre- 

 senting each are shown alongside. These curves have been rotated 90 degrees 

 clockwise from the examples previously shown. In other words, high-temperature 

 reactions are toward the right end of the curves; endothermic peaks extend down- 

 ward; and exothermic peaks extend upward. In this position it is possible to 

 present the curves in the form of a log with the base line of each sample plotted 

 against depth. 



As well No. 1, in Figure 7-5, is drilled through the successive formations AK, 

 each provides samples whose DTA curves resemble those indicated in the sim- 

 plified log at the left, with obvious breaks occurring between each formation. 

 When well No. 2 is drilled, correlation with No. 1 is desired. DTA is deter- 

 mined on cutting samples and at some depth A', the curves are similar to those 

 of well No. 1 at A. Succeeding zones B', C, D', and E' compare respectively with 

 B, C, D, and E and provide good correlation. Below E', where the fault is pene- 

 trated, an immediate difference is obvious. Study of the ensuing portions of the 

 logs, however, show that D" and E" are repeats of D' and E', while F"K" again 

 correspond with sections FK of well No. 1. The DTA logs of these two wells not 



127 



