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

204 ECONOMIC GEOLOGY seams of sand in which the oil has collected. Adjacent wells pass through strikingly different beds, and usually do not in- terfere with one another. The oil is gradually drained from the porous lenticles. The chief oilfield, Yenangyaung, obtains its supply from an area of about 1 square mile on a broad flat dome. Bores opened gushing wells, but the oil is mainly derived from many small pumped wells, In Sumatra ang Java the oilfields occur among volcanic rocks, but the oil appears to come from Kainozoic sediments which have undergone mountain folding, and volcanic heat has distilled their organic matter into oil ; the high-grade petrol from one field in Sumatra for years was burnt as the cheapest way of getting rid of it. In Borneo within the Malayan Arc ‘and further from the main folding the oil occurs in Kainozoic rocks with a homoclinal dip. Oilfields of secondary imi- portance occur in China where natural gas and oil have been obtained from salt-wells in the Triassic and Permian red sandstones for salt ; some of the wells are 3000 feet deep and took generations to bore. The continents of Africa and Australia have hitherto yielded no important supplies of oil, except in Egypt, or of natural gas, though a little has been found in Queensland. O1L SuarLe Oil shale is a clay which on distillation yields petroleum of various grades, usually ranging from asphalt or paraffin through heavy lubricating and fuel oils to the lighter illuminat- ing oil, kerosene, and to petrol and the petrol ethers. Typical oil shale itself contains no oil and only a small proportion is soluble by the ordinary solvents for organic materials and hydrocarbons. Some materials, such as some Californian diatomaceous earth which is impregnated with oil, have been classified as oil shale, and according to Cunningham Craig oil shale is clay which has adsorbed oi] from percolating petroleum. True oil shale however contains no petroleum, and the oil obtained from it is produced by destructive dis- tillation of its organic constituents, The oil producing material is a pyro-bitumen, i.e. a material which is altered into bitumen by heat, Oil shale is classed as a sapropelic coal, as a variety of cannel and is classified as earthy cannel (cf. p. 266).

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