Tenkari coal-field coveres the junctional area of three counties, Uryu, Tomamae and Embetsu, and consists of the Neogene Tertiary coal-or lignite-bearing formations overlying the Cretaceous basement. Several oil indicating localities have hitherto been reported from the coal-field by several geologists. The writers newly added several localities and from which obtained oil samples for study. As has been carried on the chemical analysis of those samples, the following facts were recognized. (1) The oil-sand from the Cretaceous containes too small quantity of crude oil for quantitative analysis. (2) The crude nature of the sample obtained from the seepage in the Quaternary of the Kamisekiyuzawa area [Loc. No. 1 in fig. 1] is quite different from that of one from the Tertiary formation of the Sanjussenzawa area [Loc. No. 6 in fig. 1]. As comparing with data of the nature of Japanese crude oil already known, the former belongs to the older type or the Cretaceous-Palaeogene oil type and the latter to the younger or the Neogene oil type [figs. 2-5]. Judging from the subserface geological data to the former seepage, it seems to the writers to be possible that this seepage is fed with crude oil generated in the underneath Cretaceous deposits through the conceald fault.
This paper deals with the structural analysis of the Upper Cretaceous System in SouthCentral Hokkaido, on Lie basis of grasping quantitatively the change in velocity of downwarping during the entire period. The writer attempts to measure quantitatively the movement of subsidence on the assumption that the rate of subsidence is equivalent to the velocity of downwarping, because the subsidence during sedimentation is misty accepted as common or/and true evidences in the ralation of upheaval of source areas and sinking of sedimentary basins. Zonal succession, composed of the species of genus Inoceramus, is represented as widest common divisor by six zones, namely; shikotanensis•orientalis•japonicus•uwajimensis•hobetsensis and concentricus nipponicus, in descending order. Each zone is extended over the whole areas under discussion without any breaks throughout the time. These zones roughly correspond to the international stages. (Fig. 1.) On the otherhand "Holmes's symposium" has presented the Time Scale in the worldwide grade, in which the Cretaceous dating from 136 million years to 65 million years subdivided into eleven stages of apploximately equal duration. Recently the laboratory research of University of Alberta and Geological Survey of Canada have supplied some noticeable results concerning the dating of the Cretaceous System mainly in South Western Alberta. However, assumption of equal duration of each stage in Upper Crtaceous Epoch is not entirely ascertained even by so many materials on the western part of the country. Upper Cretaceous Zoning (space) and corresponding Duration (time) present the factors to resolve the movement on the subjects quantitatively. Velocities of downwarping in six stages are quite interesting and distinguishable especially in the middle stage ranging from Turonian to Santonion, instead of clear coincidence of upper and lower stages in velocity gradient. (Fig. 5). Figures (in Fig. 4) and subsequent plotts (in Fig. 5A) may be changed according to true determined ages in future, however, characteristic differences and its gradients in velocities among stages remain unaltered. Upper Cretaceous sedimentary basin might be divided into four subbasins, representing different tendency of subsidence which controlls the sedimentation during the Epoch. (Fig. 7)
Since reservoir engineers are intersted in the movement of the oil-water contact in a water drive reservoir, the author tried an experiment on the problem with an electric model, because such movement problem is very difficult to solve mathematically. He wishes first to present the theory of correspondence between a reservoir and an electric model, and then make experiment results known. Although this experiment was the first trial that was performed using a simple electric model, it has enabled him to obtain considerably quantitative results. And it is considered that this sort of an experiment is very useful to analyse such problems adopted in this paper.
The VIII-zone of Yabase Oil Field and I-zone of Kubiki Oil Field are about 1, 200m deep. The pilot tests of water injection were initiated in these fields in Dec. 1954 and Aug. 1955 respectively. The applicabilities of water flooding to these deep shaly sand reservoirs are not yet proved. This paper discusses some of the difficulties and problems encountered in both tests.