In the Tokachi region, situated in eastern part of Hokkaido, some oil seeps are found from early days. However, the oil exploration surveys started in 1956, and the well drilling are not carried out up to 1961.
In this paper, the compiling studies of the results of surface geological surveys, seismic surveys, and gravitational surveys are described, and the possibility of oil production at the south-eastern part of Tokachi region is considered.
Results of the studies are as follows;
(a) The standard stratigaphic order of oil-bearing Neogene system in the Tokachi region is amost established, and the correlation to the Tertiary Formations of oil producing area in central Hokkaido is become clear.
(b) The shape and property of the sedimentary basin are nearly cleared up.
(c) The main source rock of petroleum may be the Taiki and equivalent Toberi, Kawakami Group, and their wide development is expected in this region. The reservoir rocks are contained in these groups, and at the lowest course-grained parts of the overlied Tokachi Group.
(d) The author presumes that the oil accumlations at the Sarubetsu anticline and some anticlinal structures of its western side are the most hopeful zone.
