抄録
1) Electric logging, used commonly in oil fields, requires some modification of instruments and methods for the purpose of exploration of boreholes in coal fields, where permissible error in determining thickness of seams is on the order of a centimeter. Therefore, standard. (45 mm in diameter, electrode interval : 100-250 mm)and micrologging(120 mm in maximum expansion, electrode interval : 25 mm) electrodes were designed, and were carefully removed from boreholes at a slow speed. (minimum, 100 meters per hour).
2) Since 1953, more than 20 holes of 50-1400 meters depth in the Ishikari (Hokkaido) and Saga (Kyushu) coal fields were tsted by the Mitsubishi Mining Company with improved instruments and measuring methods, and results have proved that electric logging is effective even in the case of coal exploration.
3) Main results :
a) Coal and partings more than two centimeters thick could be detected.
b) Columnar sections of holes where coal was not recovered could be adiusted.
c) Drillers could be checked when no coal was recovered.
