Experiences on deep borehole drilling in Neogene sedimentary formations during surface-based investigation phase

Matsui, Hiroya ; Sasaki, Manabu*

Japan Atomic Energy Agency (JAEA) has been conducting the project with construction of the Underground Research Laboratory (URL) called "Horonobe URL Project" since FY2000/FY2001 in Horonobe-cho, Hokkaido in Japan. The project is divided into three major phase, such as surface-based investigation phase, construction phase and operation phase. Total duration of the project is about 20 years. In the surface-based investigation phase, the eleven deep borehole investigations, which were drilled until 1000m depth, have carried out to understand a geological environment in the selected URL area formed Neocence sedimentary formations in Horonobe-cho. This report describe summarized important experiences to perform the deep borehole investigations with max. 1000m depth. This information could be great helpful for future site investigations.