Hydraulic property of the Neogene sedimentary rocks of Horonobe area, northern Hokkaido, Japan

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

We have conducted detailed permeability k and porosity n measurements using fresh surface samples and drill cores of the three Neogene sedimentary formations in Horonobe area. Main results are outlined as follows. (1) k and n decrease from upper to lower horizons due to compaction and cementation and with increasing effective pressure Pe. Pressure cycling tests provide basic data for estimating k and n structures of the host rock. (2) Measurements for two specimens cored next to each other under the same Pe exhibit relationship showing an increase in k with increasing n that can be fit with Kozeny-Carman relationship. (3) n plotted against logarithm of Pe shows a clear knee point, similar to compaction curves for soils. This knee point is several times as large as the maximum Pe estimated from stratigraphy and from opal A to CT transition, so that the knee cannot be correlated with the maximum burial depth of the sedimentary rocks.