In the northern Hokkaido, it has given rise to discussion that the Wakkanai formation, a conspicuous muddy unit, lies upon the oil producting Masuporo formation with the uncomformity which has been reco nized by Yoshio Ishida befor 23 years ago (1930). The writer carried out to survey the Wakkanai formation in the upper course of Uttu-gawa in the autum, 1949. And he found the fact that the Wakkanai formation laps over the Cretacious sediments, laking the Masuporo and the other Tertiary formations, and he recognized that the Wakkanai formation also covers directly Cretacious sediments with para-uncomformity in the south of the surveyed area. The meckanics of such relation is not yet fully analysed, however it may be said that the cretacious kern acts an important role to the migration, accumulation and the oil possibility in the district fundamentally.
The invasion of water in producing well may become interfere the flow of oil in the well. And it is important that measures be taken to catch its source and to exclude it, if economically possible. This paper presents the principle and its applications by the use of an example of water exclusion operations in Kamihama oil field.
1) The quality of coal and geological strueture of the Sinhoronai pir are suitable for the generation and accumulation of coal gas. 2) The writer estimated that the greater part of coal-gas was derived from coal-seams in early stage of carbonization.