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Okazaki, Keishi*; Uehara, Shinichi*; Shimamoto, Toshihiko*; Funaki, Hironori; Kurikami, Hiroshi; Niizato, Tadafumi; Onishi, Yuzo*
no journal, ,
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.
Uehara, Shinichi*; Shimamoto, Toshihiko*; Funaki, Hironori; Kurikami, Hiroshi; Niizato, Tadafumi; Onishi, Yuzo*
no journal, ,
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.
Otosaka, Shigeyoshi; Oku, Shunsuke*; Minami, Hideki*; Minakawa, Masayuki*; Noriki, Shinichiro*
no journal, ,
The Japan Sea is regarded as a miniature of the ocean because of its bowl-like topography and unique seawater circulation. Recent studies have suggested that biogeochemical processes in the Japan Sea correspond with the global climate change. In this study, we assessed decadal changes in particulate flux and elemental composition of sinking particle in the Japan Sea by comparing results of a sediment trap experiment in September 1984 with those in 1999-2001. Total mass flux did not show remarkable temporal change, however, biogenic opal/carbonate ratios observed recently were lower than those from the previous observation. In addition, relative content of scavenging elements such as manganese and cobalt also showed a decrease between the 15 years. These results may indicate decadal changes in ecological characteristics at the surface and transport processes of particulate materials in the deep water.