A re-consideration of the "oil window" for humic coal and kerogen type III source rocks

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Based on natural data-sets and several hydrous-pyrolysis experiments on immature humic coals, the conventional "oil window" (0.5-0.6%R0 to 1.3-1.35%R0) for humic coals is re-considered. A worldwide coal data-set comprising coals of Carboniferous - Tertiary age and having vitrinite reflectances from 0.32%R0 to 3.6%R0 indicates that initial liquid hydrocarbon generation commences at a vitrinite reflectance of 0.5%R0 to 0.6%R0, and that a significant liquid hydrocarbon build-up occurs from approximately 0.6%R0 to 0.85%R0. The start of the "oil window" corresponds to a vitrinite reflectance of 0.85%R0; however, the start of the "oil window" can vary significantly for individual coal series, and it may range up to a vitrinite reflectance of 1.15%R0. Liquid hydrocarbon generation is negligible at a vitrinite reflectance of approximately 1.8%R0, and at 2.0%R0 the hydrocarbon generative potential is exhausted. A vitrinite reflectance of 1.8%R0 corresponds to the end of the "oil window", and for general use a vitrinite reflectance range of 0.85-1.8%R0 is suggested to define the "oil window" for humic coals and kerogen type III. The end of the "oil window" at 1.8%R0 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%R0. The re-considered "oil window" between 0.85-1.8%R0 has significant implications for evaluating the prospectivity of basins dominated by terrestrial organic matter, such as coals.

Sider (fra-til)407-432
Antal sider26
TidsskriftJournal of Petroleum Geology
Udgave nummer4
StatusUdgivet - okt. 2002


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