ADAMANTANES OF GENETICALLY DIFFERENT CRUDE OILS

Chromato-mass spectrometry has been used to study C-10-C-13 adamantane hydrocarbons in crude oils of different genesis. It has been shown th at adamantanes are present both in young and in ancient crude oils of marine and continental genesis, and in mature and immature crude oils generated both by argillaceous and by carbonate rock masses, It has be en found that adamantanes are present in crude oils in far-from-equili brium ratios, Here the concentration of more stable isomers of methyla damantanes falls with increasing molecular weight, The relative concen tration distribution of adamantanes can be used as a criterion of the genetic affiliation of crude oils. In crude oils generated in carbonat e deposits, the concentration of cis-1,4-dimethyladamantane and cis-1, 3,4-trimethyladamantane is appreciably higher than in crude oils gener ated in argillaceous deposits. A comparative analysis of the distribut ion of adamantanes and steranes in crude oils has been carried out. (C ) 1998 Elsevier Science Ltd. All rights reserved.