Chap. 11] 



GEOPHYSICAL WELL TESTING 



861 



considered in shallow holes unless temperature differences betw en ad- 

 jacent holes are measured. The temperature ^d,t at a given depth d and 



^400' 



^m' 



^otxf' ^ooo' 4000' 



Fig. 11-31o. Topographic effect (calculated) of Long Beach dome on isothermal 

 surfaces (after Van Orstrand). 



f2P00\ 



fiftOO'- 



James Penk 



Fig. 11-316. Observed temperatures in Moffat Tunnel near Denver (after Van 



Orstrand). 



time t (in days, from a reference instant) may be calculated for ground of 

 known diffusivity K from 



= ». + f.e-^^- 



^(cos^^'-dy^^), (11-11) 



where e„ is the mean annual temperature, Ae^ is the annual range, and T 

 is the period (365 days) of the variation. The exponential indicates the 

 penetration, and the bracket term indicates the phase shift; K follows 

 from eq. (11-4) and is expressed in tyi per day, if depth is in meters and 



