北海道第三系・上部白亜系の有機変成と石油の熟成

Abstract

Revised parameter to measure and compile the degree of organic metamorphism of the Tertiary and the upper Cretaceous systems based on vitrinite reflectance value (R0) are introduced; i. e. V-value, decupled R0, ν-value along iso-rank direction in the traditional proximate rank classification diagram (Fig. 4). Numerous data of proximate analysis of the Tertiary and the Cretaceous coalfields and coal-bealing strata are classified by ν-value to expose regional and stratigraphic variation of organic metamorphism (Figs. 5, 6). Depth-vitrinite reflectance gradient in oil exploring deep drill holes in the western flank of the Hidaka orogenic belt is confirmed to correspond the smaller value to lower terrestrial heat flow region. Since the pattern of organic metamorphism and the regional variation of terrestrial heat flow is satisfactorily correlated, the depth of petroleum generation zone is able to be predicted based on surface organic metamorphism degree and geothermal structure in connection with subsurface vitrinite reflectance gradient, and finally regional restriction for f abourable petroleum exploration is suggested from the view point of organic metamorphism.