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The AAPG/Datapages Combined Publications Database

Journal of Petroleum Geology

Abstract

Journal of Petroleum Geology, vol.25 (4), October 2002, pp 407-432



A RE-CONSIDERATION OF THE "OIL Previous HitWINDOWNext Hit" FOR HUMIC COAL AND KEROGEN TYPE III SOURCE ROCKS

H. I. Petersen*



*Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark; email: [email protected]

    Based on natural data-sets and several hydrous-pyrolysis experiments on immature humic coals, the conventional "oil Previous HitwindowNext Hit" (0.5-0.6%Ro to 1.3-1.35%Ro) for humic coals is re-considered. A worldwide coal data-set comprising coals of Carboniferous - Tertiary age and having vitrinite reflectances from 0.32%Ro to 3.6%Ro indicates that initial liquid hydrocarbon generation commences at a vitrinite reflectance of 0.5%Ro to 0.6%Ro, and that a significant liquid hydrocarbon build-up occurs from approximately 0.6%Ro to
0.85%R
o. The start of the "oil Previous HitwindowNext Hit" corresponds to a vitrinite reflectance of 0.85%R ; however, the start of the "oil Previous HitwindowNext Hit" can vary significantly for individual coal series,

o

and it may range up to a vitrinite reflectance of 1.15%Ro. Liquid hydrocarbon generation is negligible at a vitrinite reflectance of approximately 1.8%Ro, and at 2.0%Ro the hydrocarbon generative potential is exhausted. A vitrinite reflectance of 1.8%R corresponds to the end of the "oil Previous HitwindowNext Hit", and for general use a vitrinite reflectance

o

range of 0.85-1.8%Ro is suggested to define the "oil Previous HitwindowNext Hit" for humic coals and kerogen type III. The end of the "oil Previous HitwindowNext Hit" at 1.8%Ro is supported by published data, indicating a much higher thermal stability of nC15+ hydrocarbons than is generally accepted, and therefore limited oil-to-gas cracking at 1.3%Ro. The re-considered "oil Previous HitwindowTop" between
0.85-1.8%R
o has significant implications for evaluating the prospectivity of basins dominated by terrestrial organic matter, such as coals.

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