EXPLORATION FOR PETROLEUM 23 
PERMIAN BASIN 
Surface and subsurface methods, the magnetometer, the torsion 
balance and the refraction seismograph have been used successfully 
for prospect discovery in this province. The present stage seems to be 
the early phase of the discovery as well as the evaluation of prospects 
by the reflection seismograph. An interesting situation prevails in that 
seismic reflections are not as readily returned from the Big Lime (the 
present production objective) as they are from a deeper horizon, 
probably Pennsylvanian in age. 
EDWARDS PLATEAU 
This province is one of the most intriguing and yet most baffling 
existing. Discoveries to date have been due to random wildcatting and 
the use of surface geology. All other recognized exploration methods 
have been tried and found wanting. Development in the area is at- 
tended by an unusually great hazard because of the absence of any 
method with satisfactory resolving power which is appropriate for 
use ahead of the drill. 
ROCKY MOUNTAIN PROVINCE 
The possibilities of surface methods in the area were practically 
exhausted several years ago. At present the area is yet in the stage of 
sub-marginal surface prospect evaluation by the reflection seismo- 
graph. There have been trials of geophysical methods with resolving 
powers lower than that of the reflection seismograph, but with little 
success except for the torsion balance, which has shown possibilities 
of locating structure, but little possibility of detailing structure. If 
the present interest in the producing possibilities of the Sundance 
horizon persists, the reflection seismograph may yet be used in- 
tensively to discover as well as to evaluate prospects. 
SOUTH TEXAS 
Although surface prospects are still being found, the most promis- 
ing tactics now seem to be prospect discovery by gravity methods, 
followed by evaluation with the reflection seismograph. Although 
there is some use of the reflection seismograph to discover prospects, 
the attempt is probably premature, and so may prove to be unduly 
expensive. 
SOUTHERN OKLAHOMA 
Prospect discovery by library methods, surface methods, and per- 
haps airplane mapping would seem to be the most favorable tactics, 
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