Effects of pressure on thermal evolution of organic matter
- Ecole Normale Superieure, Paris (France)
In the internal metamorphic zones of the French Alps, organic matter-bearing terrestrial sediments of Dogger age underwent an Eocene high-pressure metamorphic event (607 kbar at 300{degree}-330{degree}C). These metasediments now contain, trapped in metamorphic minerals, low evolved kerogen (small extent of molecular orientation), heavy hydrocarbon compounds (aromatic and aliphatic up to C{sup 30} with traces of pristane and phytane molecules), and gases with low C{sup 1}/C{sup 2}-C{sup 6} ratios. However, the degree of organic maturation (equivalent to catagenesis) is much less than that predicted by classical models. This field example indicates that the oil window opens with increasing pressure. Experimental pyrolysis of supercritical hexane performed in a closed, constant-pressure gold reactor at 210-15,600 bars pressure range and 290{degree}-365{degree}C, clearly demonstrates the important influence of pressure on the product distribution of hexane pyrolysis: as pressure is increased, relative light product yields decrease and heavy products increase. This can be interpreted mainly by considering the activation volumes of the reactions involved. In conclusion, the experimental and natural examples presented here indicate that the rate of thermal maturation decreases with pressure.
- OSTI ID:
- 5499165
- Report Number(s):
- CONF-8910195-; CODEN: AABUD
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (USA), Vol. 73:9; Conference: AAPG Rocky Mountain Section meeting, Albuquerque, NM (USA), 1-4 Oct 1989; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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