--> Abstract: Aspects of the Variability of the Hydrogen Index and Its Application to Measure the Oil-Potential of Coal Source Rocks: Examples from Africa and SE Asia, by Henrik I. Petersen, Sofie Lindström, Hans P. Nytoft, and Samuel O. Akande; #90082 (2008)

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Aspects of the Variability of the Hydrogen Index and Its Application to Measure the Oil-Potential of Coal Source Rocks: Examples from Africa and SE Asia

Henrik I. Petersen1, Sofie Lindström1, Hans P. Nytoft1, and Samuel O. Akande2
1Geological Survey of Denmark and Greenland (GEUS), Copenhagen K, Denmark
2Department of Geology, University of Ilorin, Ilorin, Nigeria

Coaly source rocks are important in the Australasian region and the Niger Delta, and a better understanding of factors influencing the oil-potential of coaly source rocks is necessary in order to predict the oil generation capacity. The Hydrogen Index (HI) is the most widely used parameter to describe rocks ability to generate petroleum. The HI of Type I and II source rocks is principally a measure of the oil-generating capacity, but for coals HI values can be misleading as they may relate to a mainly gas/condensate potential. Coals with similar HI’s may have different generation potential in terms of oil, which overall is controlled by coal age: Paleozoic coals are principally not oil-prone due to lack of long paraffinic chains in their kerogen structure, whereas Upper Cretaceous and Cenozoic coals can be highly oil-prone. Chemical analyses have demonstrated that the HI values of these coals commonly are related to long-chain oil-generating moieties. An example is the Maastrichtian Anambra Basin coals (onshore Niger Delta), which are highly paraffinic and oil-prone. Miocene Indonesian Kutei Basin (onshore Mahakam Delta) coals and Miocene Vietnamese coals onshore the Phu Khanh Basin are likewise oil-prone. Large variations in HI between oil-prone iso-rank coals are common and can be related to both depositional conditions and floral input. The Miocene Indonesian and Vietnamese iso-rank coals have varying HI values, but correlation between floral variations and oil-proneness cannot be documented. The Vietnamese coals show, however, correlation between HI and long-chain aliphatics and the vitrinitic and liptinitic matrix of the coals. Acknowledgement: The study was supported by the Danish Research Council for Nature and Universe (21-04-0605)

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