CUAP. 11] 



GEOPHYSICAL WELL TESTING 



853 



where ^p is dip. The normal reciprocal gradient of 1° F. in 50 feet changes, 

 therefore, with dip to the extent shown in Table 78, if the anisotropy is 

 1.765 (slate). 



Table 78 



i/b 



0° 50.0 feet 



5° 50.3 



10° 51.2 



15° 52.5 



The influence of dip can be so 

 pronounced as to make the isogeo- 

 thermal surfaces almost parallel 

 with the structural contours. 

 Two well-known examples are 

 the Salt Creek field (Fig. 11-23) 

 and the section from Oklahoma 

 City to Sapulpa (Fig. 11-24). 

 The A.P.I, report on geothermal 



• • • 28 • 



mvestigations contams many 

 more instances of this character. 

 Faults may be indicated in geo- 

 thermal maps: (1) by a slight 

 deflection of the isogeothermal 

 surfaces if the fault has thrown 

 blocks of different conductivity 

 against one another f^ and (2) by 

 a peak in the temperature curve, 

 as shown in Fig. 11-25, if waters 

 of different temperature circulate 

 in the fault plane. 



D. Heat Generating Proc- 

 esses; Causes of Tran- 

 sient Temperatures 



l/b 



20° 54.5 feet 



25° 56.8 



30° 59.6 



Fig. 11-23. Lines of equal reciprocal 

 temperature gradient and contours on sec- 

 ond Wall Creek sand in Salt Creek dome, 

 Wyoming (after Van Orstrand). 



As shown in the preceding sec- 

 tion, static distribution of temper- 

 atures is a function of the variations in the heat conductivities of rocks and 

 formations. With the exception of factors of geologic periodicity (such as 

 volcanism, glaciation, and radioactivity) most of the heat-generating proe- 



ms Am. PetroL Inst. Prod. Bull. No. 205 (Oct., 1930). 



" L O. Haas and C. R. Hoffmann, A.A.P.G. Bull., 13(10), 1257-1273 (Oct., 1929). 



