840 



GEOPHYSICAL WELL TESTING 



[Chap. 11 



Koenigsberger, Heald, and others. The development of the electrical 

 logging process in the past five years has made it possible to obtain de- 

 tailed and continuous records of well temperatures and to study their 

 relation to geologic conditions and production technique. 



A. Apparatus; Procedure 



Apparatus used in geothermal well testing depends entirely on the pur- 

 pose for which the test is undertaken. In present practice measurements 

 are made (1) in shallow holes for the location of near-surface formations, 



m 193d m 1936 1937 1938 



lopod 



16m 



Fig. 11-15. Trend of drilling depths in the United States in the past eighty years 



(from Union Oil Bulletin). 



near-surface structure, spring waters, and the like; (2) in deep wells for 

 correlating the mean gradient between wells with geologic structure; and 

 (3) in deep wells individually, for locating gas, oil, and water flows, and 

 for determining cementation depth. 



For shallow well testing, ordinary thermometers are suitable, if they are 

 provided with some sort of a cover (paraffine, rubber, or the like) to slow 

 down rapid temperature fluctuations. If they are so protected and are 

 hauled up rapidly, they will give the true bottom-hole temperature. Re- 

 sistance thermometers and thermocouples have the advantage that two of 

 them may be so connected as to give the difference in temperature of 

 adjacent holes. Thereby, the daily or any other temperature variation is 



