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A RE‐CONSIDERATION OF THE “OIL WINDOW” FOR HUMIC COAL AND KEROGEN TYPE III SOURCE ROCKS
Author(s) -
Petersen H. I.
Publication year - 2002
Publication title -
journal of petroleum geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.725
H-Index - 42
eISSN - 1747-5457
pISSN - 0141-6421
DOI - 10.1111/j.1747-5457.2002.tb00093.x
Subject(s) - vitrinite , kerogen , maceral , geology , coal , hydrocarbon , mineralogy , window (computing) , vitrinite reflectance , pyrolysis , source rock , carboniferous , geochemistry , petrography , sedimentary rock , chemistry , paleontology , organic chemistry , structural basin , computer science , operating system
Based on natural data‐sets and several hydrous‐pyrolysis experiments on immature humic coals, the conventional “oil window” (0.5–0.6%R 0 to 1.3–1.35%R 0 ) for humic coals is re‐considered. A worldwide coal data‐set comprising coals of Carboniferous ‐ Tertiary age and having vitrinite reflectances from 0.32%R 0 to 3.6%R 0 indicates that initial liquid hydrocarbon generation commences at a vitrinite reflectance of 0.5%R 0 to 0.6%R 0 , and that a significant liquid hydrocarbon build‐up occurs from approximately 0.6%R 0 to 0.85%R 0 . The start of the “oil window” corresponds to a vitrinite reflectance of 0.85%R 0 ; 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%R 0 . Liquid hydrocarbon generation is negligible at a vitrinite reflectance of approximately 1.8%R 0 , and at 2.0%R 0 the hydrocarbon generative potential is exhausted. A vitrinite reflectance of 1.8%R 0 corresponds to the end of the “oil window”, and for general use a vitrinite reflectance range of 0.85–1.8%R 0 is suggested to define the “oil window” for humic coals and kerogen type III. The end of the “oil window” at 1.8%R 0 is supported by published data, indicating a much higher thermal stability of nC 15+ hydrocarbons than is generally accepted, and therefore limited oil‐to‐gas cracking at 1.3%R 0 . The re‐considered “oil window” between 0.85–1.8%R 0 has significant implications for evaluating the prospectivity of basins dominated by terrestrial organic matter, such as coals.