紀伊半島の石油・天然ガス資源に関する地球化学的考察

概要

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To investigate a possibility of oil and gas accumulation, we analyzed surface sedimentary rocks and subsurface gases from the Neogene to the Mesozoic in the southern Kii Peninsula, Japan. Rock samples yielded total organic carbon (TOC of 0.20〜1.94% (av. 0.53%) and extractable hydrocarbon (HyR) of 9〜53 ppm (av.22 ppm). Plot of HyR versus TOC suggested most samples to be a lean oil source or a possible source of methane. Atomic H/C ratio of kerogen from the rock samples was 0.40〜0.66 (av. 0.49). Van Krevelen Diagram showed high maturities of these samples, but could not determine kerogen types. CH_4 content of gas samples was 0.000〜93.7%, mostly being higher than 1%. Plot of C_1/(C_2+C_3) versus δ^<13>C(CH_4)_<PDB> indicated their hydrocarbons to be thermocatalytic products of organic matter. CH_4 was likely to have been concentrated against other hydrocarbons during migration.
日本地球化学会の論文
1987-12-10