The Yufutsu Gas Field underlying in depths more than 4, 000 meters, locates in the vicinity of the Tomakomai industrial area, 50km south of Sapporo-city in Hokkaido, Japan. The field was discovered by the exploratory well “Minami-Yufutsu SK-1” in 1988 after years of exploiting activities of JAPEX.
Exploration drilling in the southern part of Hokkaido had been continually carried out by JAPEX since 1961, in an attempt to find a promising hydrocarbon accumulation in the area. These efforts had, however, resulted in failure before the Minami-Yufutsu SK-1 well, because of production capability of each well that was not assessed to be commercially viable.
Subsequent to the successful result in the Minami-Yufutsu well, a series of delineation wells was drilled, disclosing the essential information to evaluate the reservoir, and encouraging us to take further steps towards its development.
Following an intensive study of examining the field from both technical and economic points of view, its development was officially announced in 1993. Production began in early 1996, supplying clean energy of natural gas to the local community.
This field is quite distinctive among other gas fields worldwide in its type of reservoir formations, which are in combination of naturally fractured granite and conglomerate.
Due to the type of reservoir formations, the depths underlying, and the reservoir fluids properties, that contain waxy oil of its pour point indicating 82°F, there were a number of difficulties in designing and executing both well construction and well completion operations.
This report gives an overview of the technologies/solutions applied to develop the field during the past decade, and will help us foresee our business circumstances in the next decade.