PETROLEUM. 
29 
development presages a time, soon to arrive if not already here, when 
the present rate of production can no longer be sustained in its full 
vigor. Just so soon as the aggregate output is compounded of senile 
and youthful fields, with the latter no longer in the ascendency, the 
resource as a whole will pass inevitably into a period of slowing and 
more costly production, even though the resource is yet but half 
exhausted . 1 The period of economic stress, then, waits merely on this' 
concatenation of circumstances, by no means upon a marked physical 
exhaustion of the resource. 
WHAT PETROLEUM EXHAUSTION MEANS. 
It appears from the foregoing section that the petroleum re- 
source is not only strictly limited in size but also in ability to sustain 
' APPALACHIAN 
LIMA-1 NDIANA 
ILLINOIS 
KANSAS-OKLAHOMA 
NORTH TEXAS 
NORTHWEST LOUISIANA 
GULF COAST 
COLORADO 
YYYOMING-M0NTANA 
CALIFORNIA 
Pig. S. — Chart showing the approximate degree op exhaustion of the principal 
PETROLEUM FIELDS OF THE UNITED STATES. THE “ UNUSED PORTIONS ” CAN BE GREATLY 
INCREASED BY RECONSTRUCTED METHODS OF PRODUCTION. DATA FROM U. S. GEOLOGICAL 
Survey. 
the present rate of increase in production. We may examine, then, 
vhat would be involved in a curtailment of activities dependent upon 
petroleum, since this necessity lies in prospect, in order to be better 
prepared to weigh the gravity of the issue. 
As already noted, crude petroleum 2 is converted into four main 
products — gasoline, kerosene, fuel oil, and lubricating oils — and a 
group of substances less consequential at present which may be 
termed by-products. The social importance of these five classes of 
products may be examined in turn, although some of the points have 
1 An oil field in its youth is vigorous ; then, in particular, gushers pour forth their 
exuberance. Later, in maturity and with increasing age, the production is maintained 
with growing difficulty ; many more wells must be drilled ; the oil responds less willingly 
to stronger pumping. Eventually the production declines long before the field is near 
exhaustion. The gasoline content of the oil also decreases, as a rule, with the aging of 
the field or pool. 
2 Apart from the one-fifth, more or less, used in the crude condition, which falls 
largely into the class of fuel oil. 
500 
MILLIONS OF BARRELS 
10 00 1500 zooo 
UNUSED 
