854 



GEOPHYSICAL WELL TESTING 



[Chap. 11 



esses discussed below produce transient temperature conditions of widely 

 varying duration. When such processes are to be detected by geophysical 

 well investigation, it is, of course, not necessary to wait until temperature 

 equilibrium has been established, as was the case in the structural applica- 

 tions described in the preceding section. 



1. Radioactivity. Much has been written about the part played by 

 radioactivity in the retardation of the cooling of our planet. It is im- 

 possible to deal with this problem extensively here from the theoret- 

 ical viewpoint. Reference is made to the review and bibliography by 

 Van Orstrand.^° It is noteworthy that virtually no verification of the 



Oklahoma City 



Davenport Key West Bristow KelJyville Sapulpa 



500 

 1000 

 1500 



^ 2000 



c 



4= 



(b 



2500 

 3000 

 3500 

 4000 



4500 



Fig. 11-24. Isogeothermal surfaces and depth to granite between Oklahoma City 

 and Tulsa (after McCutchin). 



theory has been obtainable, the outstanding observation being that the 

 pitchblende deposit in Joachimstal, which is in one of the richest radium 

 localities, does not exhibit abnormally high temperatures. 



2. Volcanism. In volcanic areas large anomalies in geothermal gradients 

 may arise (a) from rapid changes in conductivities of formations (inter- 

 calation of highly porous lavas, and the like), or (6) from circulating hot 

 waters. In Oregon, Van Orstrand'^ observed reciprocal gradients as small 



'» A.A.P.G. Bull., 18(1), 13-38 (1934). 



" J. Koenigsberger, Inst. Min. Eng. Trans., 39, 1-28 (1910). 



"Van Orstrand, Am. J. Sci., 35, 22-46 (1938). 



