N-500 type drilling rig is indigenous rig which assembling is finished at July, 1949. Its design was made by the staffs of Teikoku Oil Company's Equipment Section. This rig is complete ready-for-action on trailers……speed to move…speed to erect…speed to operate. It combines 3 3/4″ draw-works, 65' jack-knife mast, 8 3/8″ rotary maclie, 5″×10″ slush power pump. This is capable of consistantly drilling to its recommended depth 2, 000 feet with 2 7/8″ drill pipe, without undue stress or strain on any part. It is operated with equal success in open fields or mountainous terrain If necessary, it is able to break down several parts in order to convey.

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The writer has theoretically inspected the results of formal investigations about permeability. As the results, it has been found that we have made the different measurement values of permeability in time, as the following three factors have never been taken care of.
(1) The errors in calculations of the measurement value.
(2) The differences due to the measurement apparatus itself.
(3) The differences by the chemical and physical changes of the porous media.
These results of the experiment had show large the differences influenced by those three factors.

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Macrofossil names and fossil localities from the Hachikoku Oilfield, Niigata Pref, are shown on the Table 2 in the Japanese text. The geologic horizon of each fossil locality is illustrated on the Table 1 in connection with the foraminiferal zoning of this region.

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Mr. K. Kanai, geologist of the Daido Oil Co., has kindly sent to the Oil Section of the Geological Survey the fossil shells found in the core of Rotary No. 16 well of 463m deep of the Hachimori Oilfield One of those is "Chlanmys kaneharai (Yok, and is buried in the conglomeratic tufaceous mudstone alternating usually with the black mudstone, which is considered as the reservoir rock of this oilregion.
The sedimentation environment of the reservoir rock suggested by this fossil occurrence is a open sea bottom condition with strong current of about 100m deep. Such an environment is far difierent from that of the black mudstone. Consequently, from the fact that such a rock alternates with the black mudstone, we can get the following suggestion concerning the study of the geologic history of this region, also based on the based assumption that this rock might be deposited primarily. That is, we are able to suppose the deposition time of the black mudstone. In other words, we can say that the crustal movement might have started at the Funakawa age. Such a supposition, it seems to me, may contribute to the exploration of the oil of this region.

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