指向性ボーリングを用いた地山ガス抜きおよび断層探査技術

Abstract

Taiheiyo Coal Mine is located on the southeast part of Kushiro-city in Hokkaido prefecture, Japan. The Mine, which is an underground coal mine, was established in 1920. The total output of clean coal during its 80 years of operation was more than 100 million tons. Its mining fields gradually expanded into sea beds in the Pacific Ocean from land areas ; and since 1951 its entire mining fields have been under the sea bed. Currently, the main fields for mining are areas located 600 to 700 meters under sea level. The production of clean coal in 1999 was 2.13 million tons and R.O.M was 4.08 million tons. The Coal Mine has commenced present directional drilling system applied in Australia for in-seam gas drainage since 1997. However, due to the coal seam condition in the Mine that collapse easier than in Australia and contain clay parting, it was difficult to keep the borehole in open. Hence we modified drilling system, in order to drill both in the coal seam and in the rock strata. This change required some modification on bit, bent sub and rod and also development of new drilling machine. After these modifications, three directional drilling systems have been installed for gas drainage and exploration underground, and another two systems will be installed by the end of March 2001. In this paper, outline of the directional drilling system and the typical result of trials for in-seam gas drainage and exploration drilling by the system are descried.