| Research Abstract |
1.Characterization of Methylphenanthrene with Methyldibenzothiophen as wide-range maturity indicator in mudrocks, Japan :
Methylphenanthrene index (PFI), a wide-range maturation indicater, was characterized with methyldebenzothiophen for the Cretaceous-tertialy mudstones in Japan. Mudstones from Miocene Nanatani-Teradomari Formation (MITI Tomikura and Tojo) in Niigata Prefecture, Onnagawa Formation in Akita prefecture, Josoji Formation in Shimane Prefecture and Cretaceous-Tertiary Shimanto Group in Kochi Prefecture were investigated to know the variation of MPI and its relation to %Ro. For all rock samples, the MPI showed increase from 0.7 to 4.2 in the mature zone (%Ro=0.5-1.9) and decrease from 4.2 to 1.3 in the over-mature zone (%Ro=1.9-4.5). The upper slope in these trends was discussed by means of geochemical kinetics, suggesting that the MPI change depend on production of intermediate MPI and the methyl-shift from α-isomer to β-isomer.
2.Geochemical kinetic parameters for isomeriza
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tion of Methylphenanthrene :
To know the variation of MPI in the oil window, the geochemical dynamics of MPI change were examined by the heating experiment of Sarukawa crude oil from Onnagawa Formation with clay mineral (bentonite) and water in the heat/pressure-stable reactor at 300, 350, 370, 380, 400 and 450℃. The activation energy (E) and frequency factor (A) of the MPI change within the upper slope were obtained by the heating experiment as follows : E = 57.2 kcal/mol and A = 2.23 x 10^<12> s^<-1>. Based on the results, the relationship between MPI and maximum paleo-temperature was estimated for some basin.
3.Contact metamorphism of Miocene Josoji black mudstones in Shimane Peninsula, southwest Japan :
Compositional changes in organic matter by contact metamorphism were investigated for Miocene Josoji black mudstones in Shimane Peninsula. Three representative outcrops were selected, where the black mudstones have invaded by ryorite and andesite lava. Several rock samples were collected from the contact plane to about 30m distance. The ryorite supposed to have thermally influenced the mudstones more than the andesite. This is due to size of the intrusion. The ryorite decomposed organic matter to be less than 10%, but the andesite to be only about 70%.
4.Compositional changes in organic matter artificially heated black mudstone from Miocene Josoji formation, southwest Japan :
This study is a preliminary experimental work on decomposition of organic matter in sedimentary rocks. Compositional changes in the organic matter after heating blask mudstone from Miocene Josoji formation, Shimane peninsula were investigated. The mud rocks were heated in an oven at constant temperature. i. e. 200, 250, 300, 350, 400, 450, 500, 550 and 600℃, for 2 days. After the experiment of 60O℃, TOC (total organic carbon), TN (total nitrogen) and TS (total sulfur) decreased to 50%, 25% and 20% of the initial rocks, respectively. Pristane/Phytane ratio and CPI (carbon preference index) decreased from 4.3 to 0.3 and from 1.1 to 0.25, respectively. HI (hydrogen index) abnormally decreased from 43 to 1. Less
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