--> Abstract: Geochemical Indications and Mass Balances on Migration of Oil and Gas in Coals, by R. Littke and D. Leythaeuser; #91012 (1992).

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ABSTRACT: Geochemical Indications and Mass Balances on Migration of Oil and Gas in Coals

LITTKE, RALF, Forschungszentrum Julich GmbH (KFA), Julich, Germany, and DETLEV LEYTHAEUSER, University of Cologne, Cologne, Germany

In recent years, results of pyrolysis-GC experiments have revealed that coals and dispersed terrigenous organic matter possess significant potentials for generation of both gaseous and liquid hydrocarbons. However, field observations suggest that coals, although often the sources of gas accumulations, are only rarely the sources of oil accumulations. These apparently contrasting results may be explained by an inhibited migration of oil in coals. To investigate the effects of migration of oil in coals, a series of Carboniferous coal samples covering a maturity interval corresponding to the "oil window" was studied by means of elemental analysis, organic geochemistry, and organic petrography. The results of the elemental analysis were converted into a mass balance, which revealed that t e relative expulsion of organic hydrogen is indeed much lower in coals than in marine source rocks in the same maturity interval. Although the mass balance thus indicated that the bulk of the bitumen generated in coals is not expelled at early stages of maturation (<1.0% Rr), organic geochemical results revealed that some expulsion is to be expected at this stage. Our data also indicate that these early expulsion effects are different for different groups of compounds and that differences exist between petroleum expulsion from coals and from associated clastic rocks containing exclusively terrigenous organic matter.

 

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)