Prospecting of the inclosed coal field north of Ariake Bay

Abstract

The Ariake Coal Mine is an inclosed undersea coal mine, located to the north of the Miike Coal Field of the Mitsui Mining Co. The district is shallow sea for the part, and is partly reclaimed land. The basement of this district consists of Palaeozoic, crystalline schists, covered by the Eocene formation-mainly coal measure-with a thickness of about 100-350 meters; the Quartanary system, about 100-200 200 meters in thickness, covers the whole district.
The prospecting of this district, mainly with seismic method and drilling, was started by the Nittetsu Mining Company in 1952. Main purpose of the prospecting is investigation of the geological structure, especially the distribution of faults, coal seams and underground water. In the seismic prospecting, the refraction method was used principally, supplemented with the reflection method. The refraction method was put into operation with a span of 500 meters. The total length of the line was about 411 kilo-meters. Five marine drilling towers of Pontoon type were constructed for drilling. The draft of these travelling towers is about 2.5 meters, with the capacity of accomodating 20 persons. About 140 holes were drilled, their total length ottaining to about 44, 000 meters. Using the drill holes, investigation of ground water was carried out by formation tester, electric logging and velocity logging.
The prospecting has confirmed nine coal seams, all being of coking bituminous coal. As. a result of the prospecting, this coal field has been developed since 1960; the man-made island with an area of 14 ha was constructed in the sea, and three shafts are now being sunk in this district. According to the development plan, the mine will produce 2 million tons of prepared coal annually, employing the horizontal mining method.