2021 Fiscal Year Final Research Report

Characterization of fracture network of cracked rocks and prediction of these transport properties

Research Project

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Project/Area Number	19K04047
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Multi-year Fund
Section	一般
Review Section	Basic Section 17040:Solid earth sciences-related
Research Institution	National Institute of Advanced Industrial Science and Technology
Principal Investigator	Takahashi Miki 国立研究開発法人産業技術総合研究所, 地質調査総合センター, 研究グループ長 (40470033)
Co-Investigator(Kenkyū-buntansha)	上原真一東邦大学, 理学部, 教授 (20378813) 渡邊了富山大学, 学術研究部都市デザイン学系, 教授 (30262497) 北村真奈美国立研究開発法人産業技術総合研究所, 地質調査総合センター, 研究員 (40795960)
Project Period (FY)	2019-04-01 – 2022-03-31
Keywords	亀裂ネットワーク / 浸透率 / 電気伝導度 / 弾性波速度
Outline of Final Research Achievements	Although rough correlations between the fracture geometries and the measured transport properties, such as porosity-permeability relationship have been proposed, we have not fully clarified the relationship between the structure of fracture network and measured properties. In this research, we challenged to establish a method how to extract characteristics of the fracture network, using 3D volume of microfocus X-ray CT images of thermally cracked granite rock specimen, and will compare between the measured and calculated transport properties: permeability and electrical conductivity. Using a trainable segmentation technique (a plugin, trainable wake segmentation, installed in Fiji), we could extract 8-bit gray scale 3D crack images. Then those images were binarized by textured Renyi entropy method. We finally compared the measured permeabilities and estimated ones from the binarized images based on persistent homology analysis which provides a size of pore of the critical path.
Free Research Field	構造地質学
Academic Significance and Societal Importance of the Research Achievements	地下深部の流体移動は，亀裂の連結性は地下深部から地表への流体そのものの移動のみならず付随して圧力や熱の移動をも強くコントロールしているにもかかわらず，多孔質媒体に比べてそのジオメトリの複雑性や不均質な分布により，孔隙率などの情報のみでは浸透率などの流体移動特性を推定するのは困難である．本研究では，亀裂ネットワークを持つ岩石の，流体移動に最も強く寄与する流路の特徴を抽出する手法の開発に取り組んだ．本研究は地球のダイナミクスに関係する諸問題の解決に貢献するだけでなく，亀裂性貯留層における水・熱資源等の開発のうえでも重要な情報を提供可能である．