The Neogene formations in the Noto Peninsula are widely distributed as an extention of the “Green tuff” basin formed in the inner zone of Northeast Japan. The Suzu and the Himi-Nadaura areas, among them, are well known as the standard Neogene sequences of the Noto-Hokuriku district, Central Japan. In order to obtain some information on geochemical evaluation for petroleum source rock, 119 argillaceous rock samples collected from each Formations of both areas mentioned above were examined through the stratigraphic variation of organic constituents and maturation obtained by extractable organic matter, visual kerogen and Rock-Eval analysis. The average values of organic carbon contents of the Nazimi and the Iizuka Formations (Middle Miocene) in the Suzu area, and the Sugata Formation (Middle Miocene) in the Himi-Nadaura area are high more than 2.0 per cent. They are higher than ones of the other Neogene oil field areas along the Japan Sea side. The results of Rock-Eval analysis, however, show that argillaceous source rocks from these Formations are immature in terms of organic maturation. Althogh the source rocks are immature, on the basis of those results and other geochemical and geological information, some considerations on the expectancy for the occurrence of immature hydrocarbon deposits in this distrct have been also presented.
We describe in detail the calcareous nannofossil assemblages present in the uppermost Cenozoic sequences in the southern Kwanto region, Japan and in the Vrica section (the Pliocene/Pleistocene boundary stratotype), southern Italy. Ten of twelve calcareous nannofossil biohorizons previously recognized in the Quaternary sequences in the Northeast Atlantic Ocean (TAKAYAMA and SATO, 1987) also occur in these areas. These datums allow us to correlate the uppermost Cenozoic sequences in the southern Kwanto region with these sequences along the Japan Sea margins. We clarify the relationships between the calcareous nannofossil biohorizons and the benthonic foraminiferal zones recognized in the sedimentary basins along the coastal regions of the Japan Sea. We also clarify the relation between these biohorizons and the Pliocene/Pleistocene boundary at its stratotype. The first occurrence of Gephyrocapsa caribbeanica, which occurs seventeen meters above the Pliocene /Pleistocene boundary and thirty meters above the Olduvai event at the Vrica section, is usable as the excellent indicator to detect the Pliocene/Pleistocene boundary.
The oil reservoir, which is one of the main reservoir in the company, has strong bottom water drive mechanism. With the increase in cumulative oil production from this reservoir, production water cut rapidly increased in several wells caused by water coning. This study was carried out to investigate the effect of water coning on the production performance. Using numerical reservoir simulator, the production oil and water rates were estimated on the actual well. The production rate was also calculated using the simplified method reported by KUO et al. The comparison of these two calculation results was studied. It is concluded that the critical rate, for which the initial low water production rate is maintained, was about 1, 500B/D. Secondly water shut-off job was very effective in order to restrain water cut in this studied well.