PETROLEUM In all the countries and areas throughout the world where petro leum has been found to exist or where there has been geological determination of oil possibilities, only in the United States of America have studies been conducted to evolve a fairly scientific basis for estimating oil reserves or resources. Even such estimates made in the United States are subject to misinterpretation due largely to the fact that reserves may be placed in a number of categories, such as proven reserves (those based on actual drilling experience) and unproven reserves (those based on geo logic considerations but not yet proven by drilling). There are other qualifications, such as whether certain proven reserves could be profitably exploited under existing conditions. More over, any estimates of reserves are subject to constant revision, and it is virtually impossible to obtain comparable figures for various countries reflecting the same degree of accuracy. It also must be borne in mind that only a fraction of the petroleum stored underground, usually associated with natural gas, is, or can be, brought to the surface. Thus it is estimated that in the United States only some 25 to 35% of the petroleum underground in the proven fields is recovered. However, production technique is in creasing this recovery as well as, by making possible deeper drill ing, opening up reserves hitherto beyond the range of estimate.
There has been substantial and continuing enlargement of the proven recoverable reserves of petroleum in the United States. In 1908, David T. Day, chief geologist of the U.S. Geological Sur vey, estimated that the ultimate total production from oil fields of the United States would range from a minimum of 10,172, 000,000bbl. to a maximum of 24,680,000,000 barrels. His esti mate included previous production, known reserves, and probable production from fields not then discovered. His minimum es timate was reached in actual production as long ago as 1927. The U.S. Geological Survey and U.S. Bureau of Mines revised Day's estimate in 1916, and estimated that the ultimate total would be ii,000,000,000 barrels. That amount of oil had been produced by the end of 1928. A comprehensive attempt at reserve estima tion was undertaken in 1921 by the U.S. Geological Survey and the American Association of Petroleum Geologists. In this effort,
a careful analysis was made of all known favourable structures, both producing and untested, based on available knowledge of sub-surface conditions and what was then considered reasonable drilling depths. Their conclusion was to the effect that future recoverable reserves amounted to 9,15o,000,000bbl., of which approximately 5,000,000.000bbl. were classed as "oil in sight" and about 4,000,000.000bbl. as "prospective and possible oil." *Proved reserves are an estimated inventory of recoverable oil, in known fields and by present methods only. They include no estimate of future discoveries nor of greater recovery in known fields from probable advances in the technique of producing oil. tAmerican Petroleum Institute. All other reserve data from Garfias and Whetsel. Ilncludes Sakhalin and all other Soviet fields.
From American Petroleum Institute; V. R. Garfias and R. V. Whetsel, Foreign Oil Dept., Cities Service Co.; U. S. Bureau of Mines.
This reserve was "exhausted" by actual production prior to the end of 1933.
In 1925, the American Petroleum Institute Committee of Eleven conducted a most exhaustive survey, and concluded that the future reserves recoverable from producing fields by then known methods of production amounted to approximately 5,300, 000,00o barrels.
In 1935, a committee of prominent geologists under the auspices of the American Petroleum Institute began making the most ex haustive and scientifically calculated estimates of U.S. petroleum reserves yet attempted, and has continued this practice virtually annually. The first estimate, as of Jan. 1, 1935, placed the proven reserve of crude oil in the United States at 12.2 billion barrels. Subsequently these estimates have been as follows: as of Jan. 1, 1937, 13.1 billion bbl. ; Jan. 1, 1938, 15.5 billion bbl., and Jan. I, 1939, 17.3 billion barrels. Thus each succeeding estimate has in creased. These estimates do not count oil available upon the application of secondary recovery methods. They make no allow ance for possible reserves in untested areas, but represent only the volume of crude oil recoverable by present known methods from fields now completely developed or drilled, or sufficiently drilled and explored to permit of reasonably accurate calculations.