Study on a method to evaluate heterogeneity of sedimentary rocks using a forward model, 3 (Contract research)

Hara, Akio*; Hoshi, Kazuyoshi*; Kato, Arata*; Maekawa, Keisuke

JAEA-Research 2007-015, 104 Pages, 2007/03

JAEA-Research-2007-015.pdf:25.1MB

It is very important for performance assessment of high-level radioactive waste disposal to develop a method to estimate heterogeneity of sedimentary rocks. We studied siliceous shale from boreholes in the Horonobe area, and developed a sedimentary process modeling software in order to establish a method to estimate heterogeneity of sedimentary rocks. In this study, we aimed for addition of functions in sedimentary process modeling software and improvement of operability. For the former aim, we added functions which were enable to consider the second sedimentation style and influences by subsidence and upheaval of basement of sedimentary basin at the time of a shoreline movement calculation. And, on the occasion of the output of calculation results, we changed the file format in order to enable to adapt to the current visualization software. For the latter aim, we developed the Graphic User Interface (GUI) to support a work for data input. Using this sedimentary process modeling software with the above-mentioned improvement, we carried out simulations for Horonobe area. For making of input data, we utilized the existing data from geological surveys which were carried out by not only Japan Atomic Energy Agency but the others. Therefore we showed two realizations of geological model of Horonobe area. Moreover, we suggested a possibility of sand deposition in a remote area from accutual boreholes. From these results, we showed an applicability of this modeling methodology.

Application of Log Interpretation Methods to Evaluate Heterogeneity in Diatomaceous Mudstone at Horonobe Area

Hara, Akio; Tsuji, Takashi*; Hoshi, Kazuyoshi*; Yagi, Masahiko*; Nishimura, Mizue*; Kawada, Koji*; Hou, J.-Y.*

Program and Abstracts, p.65, P. 65, 2005/02

To evaluate heterogeneity of diatomaceous mudstone in Horonobe area, physical properties and lithofacies of sedimentary rocks have been estimated from natural ray log data and electrical micro imaging (EMI) log data. Spatial distribution of heterogeneity of sedimentary rocks has been discussed by comparison of log data acquired from several boreholes. Five sedimentary facies, A to E, have been established. Sedimentary facies A and B, which can decipher bedding planes clearly in EMI image, have been developed horizontally with low ray and high SiOcontents while sedimentary facies D, bedding planes are not clear to decipher, have been developed horizontally with high ray and low SiOcontents. The results of this study support the estimation of Hara (2004) namely the strata which characterized with high ray have been high AlOcontents and rich in terrigenous sediments such as clay minerals, on the other hand, the strata characterized with low ray have high SiOcontents and rich in diatomaceous fossils. Layered sedimentary facies can correlate between boreholes based on natural ray log and EMI log analysis. Sedimentary system and spatial distribution of strata of Horonobe area can estimate from the results of the facies correlation.

Study on a Method to Evaluate Heterogeneity of Sedimentary Rocks Using a Forward Model, II

Hoshi, Kazuyoshi*; Hou, J.-Y.*; Kawada, Koji*; Tsuji, Takashi*; Suwabe, Mizue*

JNC TJ8400 2005-008, 138 Pages, 2005/01

JNC-TJ8400-2005-008.pdf:25.65MB

Developing a method to evaluate heterogeneity of sedimentary rocks is very important for a site survey and a property test of the site. We studied siliceous shale from wells in the Horonobe area, and developed a sedimentary process modeling software in order to establish a method to evaluate heterogeneity of sedimentary rocks. Well log analysis of Koetoi and Wakkanai Formations revealed variations of porosity, shale content, and amount of erosion. We correlate marker beds, and establish a compaction curve for siliceous shale in the Horonobe area. EMI analysis revealed alternation of thin beds which can not been recognized by naked eyes. Chemical analysis shows that this heterogeneity originates from a variation in diatom and clastic material contents in the rock. We also examined seismic data using GDI method. For sedimentary modeling software, we expanded the sedimentary simulation module, and attached another module to compare the calculated results with actual data. We also attached the module to find the best input parameters. We performed a test run using the geology model we made for Horonobe area.