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

20 ECONOMIC GEOLOGY Many Mexican wells yielded up to 60,000 barrels a day, but the life of such wells is short. Heavy losses were in- curred by these uncontrollable flows catching fire. The ‘“ Potero del Llano, No. 4,” 1914, which discharged an accumulation of oil beside a basalt intrusion into Cretaceous limestones, is one of those famous for the disasters due to its superabundant oil. The Isthmus or Tebasco fields on the Tehuantepec Isthmus were opened in 1905. The wells are associated with salt domes and are of the South Texas type; in the eastern part of the field the wells are associated with an anticline. The wells in the Isthmus fields have been less productive than the main group, but some of the oil is lighter and of better quality. Canapa—The oldest of the three chief Canadian oilfields is in the Ordovician limestones of Southern Ontario, and is an extension of the Appalachian field. The productive rocks range from the Ordovician to the Devonian and the oil comes from limestones ; the chief pools were in the Devonian Onondaga Limestone; smaller contributions come from the Silurian beds and the Ordovician Trenton Limestone. The Alberta field at the eastern foot of the Rocky Mountains is an extension of the Rocky Mountain field of Montana; but that line does not promise to extend far into Canada owing to the huge intrusions of granite. N.W. of Edmonton are the Cretaceous Athabasca tar-sands, of which the bitumen may be the heavy residue left by the evaporation of crude petroleum. The quantity of this bitumen is immense. Where the Arctic circle crosses the Mackenzie River to the W.N.W. of Fort Norman is an anticline of an Ordovician coral limestone, 6000 feet in thickness, and near it seepages of petroleum have long been known. Borings from 1914- 21 proved the existence of oil, but the development of the field is hampered by its remoteness. This oilfield and one further north in Northern Alaska are the two farthest from the Equator. West Inpies—The West Indian Islands include four oil- fields. The most famous is Trinidad, to which attention was directed by the Pitch Lake (137 acres; 135 feet thick; Cadman, Tr. I. Min. Eng., xxxv, pp. 453-80), which is re- garded as a residual deposit left by the evaporation of 40 million tons of petroleum (Thompson, tbid., xxxv, p. 478).

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