Present address: Department of Chemistry, Biology, and Marine Science, Faculty of Science, University of the Ryukyus, Senbaru, Nishihara-cho, Okinawa 903-0213, Japan.
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Origins of hydrocarbons in the Sagara oil field, central Japan
Article first published online: 18 AUG 2006
DOI: 10.1111/j.1440-1738.2006.00528.x
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How to Cite
Toki, T., Gamo, T. and Tsunogai, U. (2006), Origins of hydrocarbons in the Sagara oil field, central Japan. Island Arc, 15: 285–291. doi: 10.1111/j.1440-1738.2006.00528.x
Publication History
- Issue published online: 18 AUG 2006
- Article first published online: 18 AUG 2006
- Received 20 October 2004; accepted for publication 10 April 2006.
- Abstract
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Keywords:
- carbon isotope;
- free-gas;
- hydrocarbons;
- in situ fluid;
- microbial origin;
- Sagara Drilling Program;
- Sagara oil field;
- thermogenic origin
Abstract We collected free-gas and in situ fluid samples up to a depth of 200.6 m from the Sagara oil field, central Japan (34°44′N, 138°15′E), during the Sagara Drilling Program (SDP) and measured the concentrations and stable carbon isotopic compositions of CH4 and C2H6 in the samples. A combination of the CH4/C2H6 ratios with the carbon isotope ratios of methane indicates that the hydrocarbon gases are predominantly of thermogenic origin at all depths. The isotope signature of hydrocarbon gases of δ13
< δ13
suggests that these gases in the Sagara oil field are not generated by polymerization, but by the decomposition of organic materials.