Comparison of laboratory-measured permeability with in-situ measurements of hydraulic conductivity for the Neogene sedimentary rocks of Horonobe area, northern Hokkaido, Japan

Uehara, Shinichi*; Shimamoto, Toshihiko*; Funaki, Hironori ; Kurikami, Hiroshi  ; Niizato, Tadafumi  ; Onishi, Yuzo*

Estimation of deep underground permeability k structures is extremely difficult because transport properties of rocks are affected dramatically with fractures and fault zones and yet we do not know how much rocks are fractured and faulted at depths for a given region. We address this issue in the underground testing site in Horonobe area, where JAEA has been conducting a large-scale underground testing for sedimentary rocks. The Neogene sedimentary rocks of Horonobe area consist of Yuchi, Koetoi and Wakkanai Formations in the descending order. Hydraulic conductivity of Wakkanai Formation from in-situ measurements are compared with gas permeability as measured with a flow method for intact specimens, for fractured specimens and for breccia zones of Wakkanai Formation. In-situ data for hydraulic conductivity of lower part of Koetoi Formation is very close to that estimated from gas permeability of intact specimen, far smaller to those for brecciated samples.