Olefins of radiogenic origin in crude oils

Crude oil samples irradiated by Co-60 gamma-irradiation have been investiga ted for olefins. Olefin concentrations were found to increase in oils in th e proportion with the irradiation dose. No influence of S and/or asphaltene concentrations in oils on olefin formation was observed. The olefin hydroc arbons were found to be generated mainly through non-selective dehydrogenat ion of saturated hydrocarbons in the oils, rather than cleavage of C-C bond s of aromatic and/or resinous compounds. Structures of the laboratory-prepa red radiogenic olefins were studied (by GC,H-1 and C-13 NMR) and compared w ith structures of alkenes isolated from Paleozoic and Precambrian oils. The results of comparison do support the radiolytic concept of olefin formatio n in crude oils. There are also reported data on the olefin concentrations measured in about 700 oils from 5 basins of the Former Soviet Union, in whi ch the age of oil formations ranges from Precambrian up to Cainozoic. A ten dency for olefins to occur more often in oils from old and cold deposits ha s been established. (C) 1998 Elsevier Science Ltd. All rights reserved.