USE OF EXISTING WELLS IN SEISMOGRAPH WORK 1411 
than has heretofore been possible by the usual surface methods of opera- 
tion. This method has been used only in connection with wildcat wells. 
It is now proposed greatly to extend its usefulness by utilizing existing 
wells that have been drilled off the flanks of known domes. Literally 
hundreds of such wells are available at the present time for this purpose, 
because any well open to a depth ranging from 4,000 to 6,000 feet, or 
deeper, can be used. It does not matter whether the well is pumping or 
whether it is a dry hole. If a flowing well is used, it may be necessary to 
restrict its flow during the period it is being used for the test. The pro- 
posal here is to select any suitable well off the flank of the dome, as at A 
in Figure 2, and, after placing the detector down near the bottom of the 

Fic. 2.—Plan diagram illustrating method for deep exploration of region sur- 
rounding known domes. 
121 
