著者

早稲田 周 岩野 裕継

出版者

石油技術協会

雑誌

石油技術協会誌 (ISSN:03709868)

巻号頁・発行日

vol.72, no.6, pp.585-593, 2007 (Released:2008-11-14)

参考文献数

22

被引用文献数

10 9 10

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Carbon isotope compositions of methane, ethane and propane, and hydrocarbon ratios in gas samples provide information of their origin (microbial vs. thermogenic), maturity of thermogenic component, compositional change due to migration, and extent of biodegradation. Mixing of gases with different origins or different maturities can also be evaluated using gas isotopic and molecular compositions. While these gas geochemical data have been used mainly for petroleum exploration, their applications for development, production and operation issues are also increasing. Headspace gas analyses can be used to delineate reservoir compartments and pay zones. Carbon isotope compositions in commingled production could be used to allocate contributions form individual production zones if isotopic differences exist between the gases from the contributing reservoirs. Origin of gas seepage in production sites could be investigated by the gas molecular and isotope compositions if enough reference data exist in the area.

著者

加藤 進 西田 英毅 岩野 裕継

出版者

石油技術協会

雑誌

石油技術協会誌 (ISSN:03709868)

巻号頁・発行日

vol.79, no.3, pp.171-179, 2014 (Released:2016-07-15)

参考文献数

29

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Three oil samples, eight gas samples, and three rock samples, collected mainly from surface seepages in the northern Fossa Magna region, Nagano Prefecture, Japan, were subjected to geochemical analysis, yielding the following results.1) The oils are heavy and biodegraded, and are classified as Kubiki-type (Hirai et al., 1995). Geochemical characteristics of the oils indicate an origin from type II-III organic matter, and their maturity is estimated to be ∼ 0.7% Ro equivalent.2) The gases are mainly methane (C1); only three samples from Tenjinzawa and Nakatsuka contain heavier hydrocarbons, up to C6, and these samples have with high wetness over 10%. The chemical and isotopic compositions of the gases indicate that they are partly biodegraded and mostly thermogenic in origin, with a maturity of 0.7%-0.9% Ro equivalent.3) Mudstones in the Bessho Formation and the lower part of the Aoki Formation are probably the source rocks that generated the oil and gas in the areas of the Takafu and Komeji synclines as indicated by source rock analysis and by surface oil and gas seepages. Although subsurface geologic structures remain unclear, there is hydrocarbon potential in the zone between the areas of oil and gas seepages and the synclines.