EXPLORATION FOR PETROLEUM 19 
first oil field credited to geophysics in the Rocky Mountain Province 
resulted from the use of the reflection seismograph at the sub-mar- 
ginal surface prospect at the Quealy dome, Albany County, Wyo- 
ming. 
Actual experience shows, then, that the geophysical discoveries 
at a premium have, in general, been due to the use of these tactics 
(characterized by a higher resolving power) in the re-examination of 
sub-marginal prospects carried over from the earlier campaigns with 
tactics of a lower resolving power. However, this increase in resolving 
power was attained only at a marked increase in operating cost. Thus, 
if the recognized methods of exploration are listed (approximately) 
in order of increasing cost, they are also listed (approximately) in 
order of resolving power, as follows: 
Library methods® 
Surface geological methods 
Airplane photographs 
Core drilling (cost listing probably markedly incorrect) 
Magnetometer 
Gravity meter 
Torsion balance 
Refraction seismograph 
Reflection seismograph 
Drill (including subsurface paleontology, subsurface stratigraphy 
and electrical logging). 
From past experience, then, and for an exploration campaign, 
rather than a prospecting sortie, empirical rules can be drawn, that 
for the general case of discovery at a minimum cost: 
1. Prospects should be first located by the appropriate method 
of lowest operating cost. These prospects should be evaluated 
and culled by the successive use of the appropriate methods of 
higher cost (successive high-grading). 
2. Prospect development in a particular area should not be initi- 
ated by any given method until the area has been previously 
explored by the appropriate methods of lower cost. 
Thus, if in a given area there are ‘‘N” appropriate methods, 
A, B, C, D, etc., so arranged in order of increasing cost and resolving 
power, the sequence is: 
6 Including all the ethical and unethical methods of securing and making use of 
“other peoples’ data.” 
263 
