The Elements of economic geology

Bibliographic data

Monograph

Identifikator:: 1773832379

URN:: urn:nbn:de:zbw-retromon-172798

Document type:: Monograph

Author:: Gregory, John W. http://d-nb.info/gnd/11683014X

Title:: The Elements of economic geology

Place of publication:: London

Publisher:: Methuen

Year of publication:: 1928

Scope:: XIV, 312 S.; graph. Darst.

Digitisation:: 2021

Collection:: Economics Books

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Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Part V. Mineral fuels

Collection:: Economics Books

278 ECONOMIC GEOLOGY in America, and at the advice of the Geological Survey special efforts were made to reach the untouched deep level oil beds in California; and wells have now been sunk there to depths of over 8300 feet. The increased yield made California the most prolific of the States, and led to a serious fall in the price of crude oil. California reached its maximum of nearly 263 million barrels in 1923 ; but its decline has been more than counterbalanced by increased yields from Okla- homa and Texas. Nevertheless, in September, 1926, the Federal Oil Conservation Board of the United States (Repori, pt. i, 1026, p. 6; and cf. p. 8) states that the oil available by flowing and pumping wells from the present producing and proven fields would only maintain the present output for six years, and that of the current production more than half comes from only 4 per cent. of the wells, which are for the most part only a year or so old, and from fields that have been discovered within the past five years. The life of the fields, it proclaims a matter of grave concern. TrE OricIN oF OrL—Success in search for petroleum is helped by a right conclusion as to its origin. Chemists have repeatedly asserted that mineral oil is an inorganic product, due to the action of superheated steam on iron carbides in the interior of the earth. This theory is a chemical possi- bility, but is disproved by the evidence of distribution. If the oil came from the interior it should be found mostly in old rocks and be rare in new rocks. The reverse is the case, Oil is not found in any commercial quantity in the most ancient rocks of the earth’s crust nor in the Cambrian. Ac. cording to Beeby Thompson (0il-Field Explor., i, 1925, p. 16), out of a total production to the end of 1923 of 12,094,000,000 barrels, the Kainozoic yield was 44 per cent., the Mesozoic 15 per cent., and the Paleozoic 41 per cent. Of the Palzo- zoic 88 per cent. is Permian and Carboniferous, 2 per cent. Devonian, and 10 per cent. Silurian and Ordovician. Hence the youngest geological Group yields most oil, and in the Palzozoic the upper Systems are the most productive, and there is practically none in the lowest, the Cambrian. Petroleum is an organic product due to the slow distillation of buried animal and vegetable tissues by heat and pressure. The organic nature of oil is suggested by its composition of carbon, hydrogen, and oxygen, which are the chief constitu-

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