Kubiki Gas Field is a general term of the several gas fields existing in Kubiki Plain in the south-western part of Niigata Prefecture. Five gas fields, Katamachi, Meijj, Kuroi, Asahi, and Shinkuroi, have been discovered by now, while a potential oil pool has been discovered in the south western wing of Katamachi structure. All of these fields are now being actively developed. In this paper, the writer investigates the stratigraphy and tectonic history of Kubiki sedimentary basin where above-mentioned gas and oil fields are located, and further explains the consideration on the migration and accumulation of oil and gas which show an unique distribution.
Abstract: The Cretaceous sequence in Hokkaido might be classified two major groups by the orogenic cycles. The agency of the first orogenic cycle origenated in Okhotsk Sea and shift the basin in the direction of south-west. It is in the cycle that the Lower Cretaceous (Neocomian-Cenomanian) formations were deposited. The second that was caused by the elevation of the Honshil arc moved the basin in the direction of east, from the western Honshu are to the eastern Pacific Ocean. In this cycle, the Upper Cretaceous (Turonian-Maestrichtian) formation were deposited. Each of the major cycles has two minor cycles. The former break of them is between the Neocomian and Aptian, and latter between the Campanian and Maestrichtian. Corresponding with them, each several breaks of fauna could be recognized. Particularly, the faunal break between the Cenomanian and Turonian is most dominant. The isopach maps of each formation are shown, Figs. 1-4. The depositional cross section from east to west is shown, Fig. 5.
From the mathematical point of view, water drive fields present us many interesting problems. There are several solutions for the diffusivity equation for unsteady-state flow of a compressible liquid in a porous media. However, all these solutions are for the single fluid case. In the solutions to be presented here, the writer tried to solve the equation under several assumptions, taking into account the existence of the aquifer around the oil reservoir and applying the Laplace transformation.