PETROLEUM RESOURCES—LEVORSEN 
by no means exhausted, but to meet 
the ever-increasing demands new areas 
must be added to them. 
When in geologic thought we pro- 
ceed outward from these established 
areas of production, however, we come 
into more and more speculative regions 
which require increasing amounts of 
geologic imagination to visualize their 
potentialities in terms of important 
future supplies. Some examples of 
these areas or prospective provinces 
are the Anadarko Basin; the Conti- 
nental Shelf; the coastal plains of Mex- 
ico; the interior plains of western Can- 
ada; Florida and the Southeastern 
States; New Brunswick and other Mari- 
time Provinces; the Atlantic Coastal 
Plain; the Great Basin region; the over- 
thrust fault belts and the sediments of 
Cambrian age. Valid objections, both 
geologic and economic, can be found 
to each of these areas which either 
overbalance the favorable factors or 
are overbalanced by them depending 
on who makes the appraisal, for what 
purpose, and when. There is nothing 
new in such a statement as every in- 
dividual prospect, even in the old es- 
tablished provinces, goes through the 
same sort of reasoning in the normal 
competitive operation of the petroleum 
industry. The test well is finally 
drilled when, in the mind of someone, 
the favorable factors overbalance the 
unfavorable. Countless pools have 
been discovered when the majority, 
orthodox geologic opinion rated the 
prospects low, or even negligible and 
the discovery well had but a small 
minority support. 
The characteristics of provinces par- 
allel those of individual oil fields in 
many respects, and the single oil or 
gas pool is often a “Shand specimen” 
of the province insofar as its geologic 
history is concerned. Experience has 
shown that every oil field is unique in 
that it has its own stratigraphic and 
structural development, and the same 
uniqueness is true of a_ province. 
Therefore, in a new province, we 
should not expect to duplicate the geo- 
logic history found in the proven prov- 
245 
inces. Any evaluation of prospective 
producing regions should depend 
rather on the objective application of 
principles to the observed geologic 
conditions of the area being considered. 
Reduced to their simplest terms, the 
geologic factors which favor a region 
as a potential petroleum province are: 
(1) sediments, preferably but not nec- 
essarily marine, variable, and unmet- 
amorphosed—generally the more the 
better; (2) evidences of oil and gas, 
either from surface seepages or show- 
ings in wells; (3) unconformities—also 
the more the better; and (4) up-dip 
wedge belts of permeability resulting 
from any cause. These factors may be 
termed common denominators of 
known petroleum provinces, and, 
while their presence does not assure 
commercial production in a new re- 
gion, yet the better and stronger these 
factors are developed, the better the 
chances for such production. Once a 
petroleum province has been estab- 
lished, there remains only the problem 
of finding the local traps. 
The geologic merit of a prospective 
region is often tempered by the exces- 
sive drilling depths necessary to reach 
the productive formations. During 
recent years, the average depth of ex- 
ploratory drilling has steadily in- 
creased, and today wells 12,000 to 
15,000 feet in depth are common. 
The deepest hole to date was drilled 
last summer in western Oklahoma to 
a depth of 17,823 feet. It is therefore 
assumed that test wells as much as 
20,000 feet in depth may be considered 
as practical in the petroleum explora- 
tion of the future. 
Another important factor which 
enters into the consideration of a pro- 
spective region is its distance from the 
market. Our petroleum demand is 
strong enough that it can be expected 
to reach for supply anywhere on this 
continent either through pipe lines or 
ocean transport, provided the supply 
is large enough to justify the expense. 
While distance from market is com- 
monly thought of in terms of miles, 
equally significant are the hurdles 
