The tendency toward amalgamation of individual producing, transporting, refining and marketing interests into strong units capable of competition in domestic and foreign markets on relatively equal terms with each other and with pre-existing combinations of equivalent strength will doubtless increase, and with the growing strength of the several units will come an efficient and thorough quest for petroleum in all parts of the world.
In the refining of petroleum it is probable that methods will be devised and perfected for recovering more of the light-gravity products from low-grade petroleum and for the conversion of the less-salable products of petroleum into products of greatest current demand. Moreover, it is believed that internal-combustion engines will be so modified as to run successfully on petroleum products of lower volatility than gasoline. The use of petroleum as railroad, marine, and industrial fuel is destined to increase enormously in the next decade.
Although an important contributor to the oil-supply of Great Britain, the shale-oil industry has received little attention in recent years outside of Scotland. Investigations by the United States Geological Survey have demonstrated that the United States contains vast deposits of oil shale in Utah, Colorado, Wyoming and Nevada, much of which will average higher in oil content than the Scottish shale. Efforts already begun to develop methods for the recovery of shale oil on a commercial scale in the United States will undoubtedly result in the establishment of a shale-oil industry in this country within the next two or three years. The future growth of this industry will depend largely on the rapidity of the decline in the domestic production of petroleum.
GEOLOGICAL DISTRIBUTION
Commercial accumulations of petroleum are everywhere restricted to strata of sedimentary origin. In the United States petroleum is produced commercially from strata of all periods from Cambrian to Quaternary, the most prolific sources being in strata of the Carboniferous and Tertiary systems. The geological age of the chief sources of petroleum production in each of the other oil-producing countries of the world is indicated in the table following:
Table 1.—Geologic Age of Petroleum-bearing Formations
| Country | System |
|---|---|
| North America | |
| Canada | Silurian and Devonian |
| Mexico | Cretaceous and basal Tertiary |
| Alaska | Tertiary (?) |
| West Indies | |
| Trinidad | Tertiary |
| Cuba | Cretaceous and pre-Cretaceous |
| South America | |
| Colombia | Cretaceous and Tertiary |
| Venezuela | Cretaceous and Tertiary |
| Peru | Tertiary |
| Argentina | Jurassic, Cretaceous and Tertiary |
| Europe | |
| Russia | Tertiary |
| Roumania | Tertiary |
| Galicia | Tertiary |
| Italy | Tertiary |
| Germany (Alsace) | Tertiary and pre-Tertiary |
| Asia | |
| India | Tertiary |
| Turkestan | Tertiary |
| Persia | Tertiary |
| Africa | |
| Algeria | Tertiary |
| Egypt | Tertiary |
| Oceania | |
| Japan | Tertiary |
| Dutch East Indies | Tertiary |
| New Zealand | Cretaceous and Tertiary |
From the foregoing table one might conclude that a direct relation exists between the distribution of Tertiary rocks and the supply of petroleum, but in the United States, which produces two-thirds of the world’s current supply, the quest for petroleum has, under scientific direction, included the entire range of the stratigraphic column, and has found petroleum in considerable quantities in the rocks of each geologic system younger than the Cambrian.
The fact that seeps and other surface indications of petroleum are generally more pronounced in the relatively younger Mesozoic strata than in the older Paleozoic formations, and the further fact that geologic exploration for oil and gas in countries other than the United States has been restricted in the main to areas containing the most pronounced indications of petroleum, tend to account for the predominance of the Tertiary system in the foregoing table and to indicate the fallacy of attempts to estimate the world’s reserves of petroleum on stratigraphic evidence alone.
Despite the broad geologic range of petroleum, its occurrence in specific members, formations, groups, series or systems is by no means universal. On the contrary, its occurrence is restricted to specific localities in which are fulfilled certain variable relations, as yet but little understood, that involve (1) the constitution, sequence and content of organic matter of the sediments; (2) the nature and degree of metamorphism they have undergone; (3) their structure; and (4) their degree of saturation with salt water. Because the most detailed geologic work is insufficient to provide a basis for the appropriate evaluation of the numerous factors involved, and because only a relatively small percentage of the areas of sedimentary rocks in the world have been examined geologically in appreciable detail, any estimate of the future supply of petroleum in the world is peculiarly hazardous.