Development of rock physics models of characterizing fluid flow in faults

• Project Area: Science of Slow to Fast Earthquakes
• Project/Area Number: 22H05303
• Research Category: Grant-in-Aid for Transformative Research Areas (A)
• Allocation Type: Single-year Grants
• Review Section: Transformative Research Areas, Section (II)
• Research Institution: Kyoto University
• Principal Investigator: 澤山 和貴 京都大学, 理学研究科, 助教 (10936991)
• Project Period (FY): 2022-06-16 – 2024-03-31
• Project Status: Completed (Fiscal Year 2023)
• Budget Amount: ¥4,940,000 (Direct Cost: ¥3,800,000、Indirect Cost: ¥1,140,000); Fiscal Year 2023: ¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000); Fiscal Year 2022: ¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000)
• Keywords: 岩石物理モデル / 浸透率 / 地震波速度 / 断層 / デジタル岩石物理 / 異方性 / 空隙率 / アップスケール / アスペリティ / 弾性波トモグラフィー / 電気比抵抗 / 3Dプリンタ / 比抵抗

Outline of Research at the Start

多様な地震の発生様式には断層の水理特性の時空間分布が関連しているとの仮説を立て，断層内流体流動を観測物性値から推定するモデルを考案する。断層面の粗さ形状・アスペリティの変形と岩石物性との相関を実験によって詳細に明らかにし，数値計算手法を駆使することでそのスケーリング則を解明する。観測から得られる岩石物性値と本提案モデルを組み合わせることで，従来の岩石物理モデルでは困難であった地下透水性のモデリング・モニタリングを目指す。

Outline of Annual Research Achievements

本研究では，断層の水理特性を地球物理学的観測手法から推定するための岩石物理モデル確立を目的とした。本年度は，昨年度に構築した実験システムを拡張し，模擬断層面の応力を変えながら亀裂開口幅と浸透率・電気比抵抗・地震波速度を同時測定する実験システムを構築した。模擬断層面は，天然断層のフラクタル特性を模擬して非整数ブラウンで数値的に作成し，3Dプリンタで造形した。また地震波速度測定は，圧電素子を多点に配置し，アレイ切替・初動ピックの自動化システムによって複数アレイでトモグラフィー測定を実施した。測定の結果，浸透率と比抵抗の関係はサンプルに依存しない一方で，地震波速度はパスごとに異なる変化を示した。感圧紙を利用してアスペリティの接触状態分布を推定したところ，これによって速度変化が概ね説明できることが明らかとなった。
実験室スケールの経験式から理論的な検証を行うため，同様のフラクタル特性を入力した数値シミュレーションも行った。計算手法の改良により，~kmスケールの亀裂に対してアスペリティの変形・流体流動・電気伝導・応力-ひずみ解析を同時に実現するデジタル岩石物理スキームを確立した。解析の結果，亀裂のサイズ・粗さ・せん断変位によって浸透率，比抵抗，地震波速度はそれぞれ異なる挙動を示し，浸透率は開口幅，比抵抗は接触面積，地震波速度はその双方に大きく支配されることが明らかとなった。また浸透率と比抵抗の関係は亀裂のサイズ・粗さ・せん断変位には依らず，両対数軸上で線形関係がみられ，その傾きは流路の屈曲度から求められる。この関係の傾きの変化は流路の連結性によって変化し，その閾値は亀裂の性状によらず接触面積~20%で説明できる。この値は地震波速度の変化が頭打ちになる閾値と一致しており，地震波速度と比抵抗の双方の情報を活用することで，一枚亀裂の透水性の変化を予測可能であるモデルを提案した。

Research Progress Status

令和5年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

令和5年度が最終年度であるため、記入しない。

Research Products

• [Int'l Joint Research] Purdue大学(米国)
• [Journal Article] Using Digital Rock Physics for Elucidating the Relationship between Pore Microstructure and Resistivity in Porous Rocks (2024)
  • Author(s): SUZUKI Takeshi、SAWAYAMA Kazuki
  • Journal Title: Journal of the Society of Materials Science, Japan Volume: 73 Issue: 3 Pages: 232-239
  • DOI: 10.2472/jsms.73.232
  • ISSN: 0514-5163, 1880-7488
  • Year and Date: 2024-03-15
  • Peer Reviewed / Open Access
• [Journal Article] Extracting crucial microstructures to characterize the elastic wave velocity and resistivity of Berea sandstone using convolutional neural networks (2024)
  • Author(s): Kazuki Sawayama; Takeshi Tsuji; Koki Shige
  • Journal Title: GEOPHYSICS Volume: 89 Issue: 1 Pages: 117-126
  • DOI: 10.1190/geo2023-0163.1
  • Peer Reviewed
• [Journal Article] Joint Diagnostic Approach to Pressure and Tracer Responses from Reservoirs: An Experimental and Theoretical Study to Estimate the Accuracy of Reservoir Models (2024)
  • Author(s): Mitsuo Matsumoto; Kazuki Sawayama
  • Journal Title: Geofluids Volume: 2024 Pages: 1-21
  • DOI: 10.1155/2024/9329314
  • Peer Reviewed
• [Journal Article] Dependence of resistivity of natural rock samples on humidity (2024)
  • Author(s): Suzuki Takeshi、Yoshimura Ryokei、Yamazaki Ken'ichi、Minami Takuto、Sawayama Kazuki、Oshiman Naoto
  • Journal Title: Journal of Applied Geophysics Volume: 220 Pages: 105271-105271
  • DOI: 10.1016/j.jappgeo.2023.105271
  • Peer Reviewed
• [Journal Article] Regression activation mapping detects the characteristic microstructures of rock physical properties: Insights from the combination of digital rock physics and convolutional neural networks (2023)
  • Author(s): Kazuki Sawayama; Takeshi Tsuji
  • Journal Title: Proc. Seventh International Conference on Engineering Geophysics Volume: 7 Pages: 30-36
  • DOI: 10.1190/iceg2023-007.1
  • Peer Reviewed
• [Journal Article] The relationship between the ice content and electrical conductivity of lunar regolith: towards exploration of lunar ice resource utilizing electrical and electromagnetic methods (2023)
  • Author(s): Koshi Wakura; Kazuki Sawayama; Tatsunori Ikeda; Takeshi Tsuji
  • Journal Title: Proc. International Symposium on Earth Science and Technology Volume: 2023
• [Journal Article] Relationship Between Permeability and Resistivity of Sheared Rock Fractures: The Role of Tortuosity and Flow Path Percolation (2023)
  • Author(s): K. Sawayama; T. Ishibashi; F. Jiang; T. Tsuji
  • Journal Title: Geophysical Research Letters Volume: 50 Issue: 20
  • DOI: 10.1029/2023gl104418
  • Peer Reviewed / Open Access
• [Journal Article] Estimation of the mass fraction and distribution of ice in a lunar regolith simulant from seismic velocity (2023)
  • Author(s): Takaaki Kunimasu; Kazuki Sawayama; Takeshi Tsuji
  • Journal Title: Icarus Volume: 406 Pages: 115725-115725
  • DOI: 10.1016/j.icarus.2023.115725
  • Peer Reviewed
• [Journal Article] Rock Physical Modeling of Sheared Fractures: Permeability-Resistivity-Seismic Velocity Relationship Explored via Digital Rock Physics Approach (2023)
  • Author(s): K. Sawayama; T. Ishibashi; F. Jiang; T. Tsuji
  • Journal Title: U.S. Rock Mechanics/Geomechanics Volume: 740
  • DOI: 10.56952/arma-2023-0740
  • Peer Reviewed
• [Journal Article] Simultaneous electrical resistivity and elastic wave velocity measurements during triaxial deformation of granite under brine-saturated conditions (2023)
  • Author(s): Katayama Ikuo、Aoi Yu、Tanimoto Kazumasa、Akamatsu Yuya、Sawayama Kazuki
  • Journal Title: Earth, Planets and Space Volume: 75 Issue: 1 Pages: 56-56
  • DOI: 10.1186/s40623-023-01809-4
  • Peer Reviewed / Open Access
• [Journal Article] Permeability evolution in fine-grained Aji granite during triaxial compression experiments (2023)
  • Author(s): Sueyoshi, K., Sawayama, K., and Katayama, I.
  • Journal Title: Geophysical Prospecting Volume: - Issue: 2 Pages: 675-684
  • DOI: 10.1111/1365-2478.13412
  • Peer Reviewed / Open Access
• [Journal Article] Rock physical modeling of sheared fractures: permeability-resistivity-seismic velocity relationship explored via digital rock physics approach (2023)
  • Author(s): Kazuki SAWAYAMA, Takuya ISHIBASHI, Fei JIANG, Takeshi TSUJI
  • Journal Title: ARMA2023 Volume: 740 Pages: 1-10
  • Peer Reviewed
• [Journal Article] デジタル岩石物理による亀裂岩石の比抵抗と空隙率・浸透率との関係 (2023)
  • Author(s): 澤山和貴
  • Journal Title: CA研究会論文集 Volume: 0 Pages: 35-82
  • Open Access
• [Journal Article] 大分平野における適正な温泉坑井離隔距離 に関する理論的検討 (2023)
  • Author(s): 澤山 和貴, 大沢 信二, 松本 光央
  • Journal Title: 大分県温泉調査会研究報告 Volume: 74 Pages: 0-0
  • Open Access
• [Journal Article] Elastic Wave Velocity Changes Due to the Fracture Aperture and Density, and Direct Correlation With Permeability: An Energetic Approach to Mated Rock Fractures (2022)
  • Author(s): Sawayama K.、Ikeda T.、Tsuji T.、Jiang F.、Nishizawa O.、Fujimitsu Y.
  • Journal Title: Journal of Geophysical Research: Solid Earth Volume: 127 Issue: 2
  • DOI: 10.1029/2021jb022639
  • Peer Reviewed
• [Journal Article] Accurate determination of the first arrival time of elastic wave traveled through rock sample by machine learning (2022)
  • Author(s): Suwa Yuji、Gu Zhiming、Obata Takuya、Nakagawa Shinji、Morishita Ryoichi、Sawayama Kazuki、Tsuji Takeshi
  • Journal Title: Journal of Applied Geophysics Volume: 203 Pages: 104688-104688
  • DOI: 10.1016/j.jappgeo.2022.104688
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Resistivity structural imaging of the Olkaria Domes geothermal field in Kenya using 2D and 3D MT Data inversion (2022)
  • Author(s): Omollo Philip、Nishijima Jun、Fujimitsu Yasuhiro、Sawayama Kazuki
  • Journal Title: Geothermics Volume: 103 Pages: 102414-102414
  • DOI: 10.1016/j.geothermics.2022.102414
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Hydro-Mechanical-Electrical simulations of rock fractures toward indirect estimation and monitoring of EGS (2022)
  • Author(s): Kazuki SAWAYAMA, Takuya ISHIBASHI, Fei JIANG, Takeshi TSUJI
  • Journal Title: Proc. CouFrac2022 Volume: 97 Pages: 1-4
  • Peer Reviewed
• [Journal Article] Relating permeability and geophysical properties with asperity contact (2022)
  • Author(s): Kazuki SAWAYAMA, Takeshi TSUJI
  • Journal Title: International Joint Workshop on Slow-to-Fast Earthquakes 2022 Volume: 0 Pages: 0-0
• [Journal Article] Universal relationship between permeability and resistivity of sheared rock fractures: the role of tortuosity and flow path percolation (2022)
  • Author(s): Kazuki SAWAYAMA, Takuya ISHIBASHI, Fei JIANG, Takeshi TSUJI
  • Journal Title: Authorea Volume: 0 Pages: 0-0
  • Open Access
• [Journal Article] Permeability evolution in fine-grained Aji granite during triaxial compression experiments (2022)
  • Author(s): K Sueyoshi, I Katayama, K Sawayama
  • Journal Title: Authorea Volume: 0 Pages: 0-0
  • Open Access
• [Journal Article] Heterogeneity of Subsurface Pore Distribution: Characterization based on Pressure and Tracer Responses to Identify Undiscovered Permeable Structures in Reservoirs (2022)
  • Author(s): M Matsumoto, K Sawayama
  • Journal Title: Authorea Volume: 0 Pages: 0-0
  • DOI: 10.1002/essoar.10512889.1
  • Open Access
• [Journal Article] Relationship between ice content rate and elastic wave velocity of lunar regolith simulant based on digital rock physics (2022)
  • Author(s): Takaaki Kunimasu, Kazuki Sawayama, Tatsunori Ikeda, Takeshi Tsuji
  • Journal Title: Proc. CINEST Volume: 0 Pages: 0-0
• [Journal Article] 含水率の異なる月のレゴリスシミュラントの電気伝導度の測定及び推定 (2022)
  • Author(s): 輪倉 光矢, 澤山 和貴, 辻 健, 池田 達紀
  • Journal Title: 物理探査学会学術講演会論文集 Volume: 147
• [Presentation] Effects of anisotropy and tortuosity on the relationship between electrical resistivity and porosity of sandstone: insight from digital rock physics (2023)
  • Author(s): Takeshi Suzuki; Kazuki Sawayama
  • Organizer: AGU Fall Meeting 2023
• [Presentation] Changes in Electrical Conductivity and Permeability of Synthetic Sheared Fractures under Stress (2023)
  • Author(s): Nayu Takita; Kazuki Sawayama
  • Organizer: AGU Fall Meeting 2023
• [Presentation] Simultaneous measurements of electrical resistivity and seismic velocities of two orthogonal directions during triaxial deformation until failure (2023)
  • Author(s): Kazuki Sawayama; Jiei Sou; Yuya Akamatsu; Ikuo Katayama; Takeshi Suzuki
  • Organizer: AGU Fall Meeting 2023
• [Presentation] The relationship between the ice content and electrical conductivity of lunar regolith: towards exploration of lunar ice resource utilizing electrical and electromagnetic methods (2023)
  • Author(s): Koshi Wakura; Kazuki Sawayama; Tatsunori Ikeda; Takeshi Tsuji
  • Organizer: International Symposium on Earth Science and Technology
• [Presentation] 亀裂の閉鎖による電気比抵抗と亀裂浸透率の関係性に対する実測定 (2023)
  • Author(s): 宗 慈瑛; 澤山 和貴
  • Organizer: 地熱学会令和5年学術講演会
• [Presentation] Regression activation mapping detects the characteristic microstructures of rock physical properties: Insights from the combination of digital rock physics and convolutional neural networks (2023)
  • Author(s): Kazuki Sawayama; Takeshi Tsuji
  • Organizer: Seventh International Conference on Engineering Geophysics, Al Ain, UAE, 16?19 October 2023
  • Invited
• [Presentation] Direct investigations of the fracture flow with asperity contact, and its relationship to the geophysical properties (2023)
  • Author(s): Kazuki Sawayama; Jiei Sou
  • Organizer: International Joint Workshop on Slow-to-Fast Earthquakes
• [Presentation] Rock Physical Modeling of Sheared Fractures: Permeability-Resistivity-Seismic Velocity Relationship Explored via Digital Rock Physics Approach (2023)
  • Author(s): K. Sawayama; T. Ishibashi; F. Jiang; T. Tsuji
  • Organizer: U.S. Rock Mechanics/Geomechanics
• [Presentation] 瀧田 菜友, 柴田 智郎, 澤山 和貴 (2023)
  • Author(s): 亀裂性岩盤における剪断変位; 垂直応力に対する浸透率と比抵抗の変化の関係
  • Organizer: 日本地球惑星科学連合2023年大会
• [Presentation] 三軸圧縮試験における比抵抗の異方性の測定方法の開発 (2023)
  • Author(s): 宗 慈瑛; 赤松 祐哉; 片山 郁夫; 鈴木 健士; 澤山 和貴
  • Organizer: 日本地球惑星科学連合2023年大会
• [Presentation] Estimating electrical resistivity and tortuosity of sandstone using digital rock physics (2023)
  • Author(s): Takeshi Suzuki; Kazuki Sawayama
  • Organizer: Japan Geoscience Union Meeting 2023
• [Presentation] 岩石物性値を支配する特徴的な微細構造をデジタル岩石物理と機械学習から可視化する試み (2023)
  • Author(s): 澤山 和貴; 辻 健
  • Organizer: 日本地球惑星科学連合2023年大会
• [Presentation] Rock physics and fluid flow of fractures: Possible roles in understanding slow-to-fast earthquakes (2023)
  • Author(s): Kazuki SAWAYAMA
  • Organizer: Slow-to-fast earthquake Beppu meeting
• [Presentation] Relating permeability and geophysical properties with asperity contact (2022)
  • Author(s): Kazuki SAWAYAMA, Takeshi TSUJI
  • Organizer: International Joint Workshop on Slow-to-Fast Earthquakes 2022
  • Int'l Joint Research
• [Presentation] Hydro-Mechanical-Electrical simulations of rock fractures toward indirect estimation and monitoring of EGS (2022)
  • Author(s): Kazuki SAWAYAMA, Takuya ISHIBASHI, Fei JIANG, Takeshi TSUJI
  • Organizer: CouFrac2022
  • Int'l Joint Research
• [Presentation] Simultaneous changes in electrical resistivity and elastic wave velocity with fracture permeability evolution of synthetic faults (2022)
  • Author(s): Kazuki SAWAYAMA, Takuya ISHIBASHI, Fei JIANG, Takeshi TSUJI
  • Organizer: AGU2022 fall meeting
  • Int'l Joint Research
• [Presentation] 異方性のある亀裂の流体流動挙動と岩石物性:デジタル岩石物理によるスケール依存性の検討 (2022)
  • Author(s): 澤山和貴, 石橋琢也, 蒋 飛,辻 健
  • Organizer: 日本地球惑星科学連合2022年大会
• [Presentation] デジタル岩石物理による亀裂岩石の比抵抗と空隙率・浸透率との関係 (2022)
  • Author(s): 澤山和貴
  • Organizer: 2022年度 Conductivity Anomaly 研究会
• [Presentation] 平野部深層熱水型温泉の適正利用に関する理論的検討 (2022)
  • Author(s): 澤山 和貴, 大沢 信二, 松本 光央
  • Organizer: 地熱学会学術講演会
• [Presentation] Relationship between ice content rate and elastic wave velocity of lunar regolith simulant based on digital rock physics (2022)
  • Author(s): Takaaki Kunimasu, Kazuki Sawayama, Tatsunori Ikeda, Takeshi Tsuji
  • Organizer: International Symposium on Earth Science and Technology 2022
  • Int'l Joint Research
• [Presentation] 含水率の異なる月のレゴリスシミュラントの電気伝導度の測定及び推定 (2022)
  • Author(s): 輪倉 光矢, 澤山 和貴, 辻 健, 池田 達紀
  • Organizer: 物理探査学会
• [Presentation] 小笠原諸島西之島で2016年に採取された溶岩試料の比抵抗・弾性波・空隙率・密度測定_ (2022)
  • Author(s): 鈴木健士, 多田訓子, 澤山和貴, 谷本和優, 坂本玄弥, 赤松祐哉, 片山郁夫, 市原寛, 山本裕二, 前野深
  • Organizer: 2022年度 Conductivity Anomaly 研究会
• [Presentation] 非湿潤状態の岩石比抵抗にみられる湿度依存性 (2022)
  • Author(s): 鈴木健士, 吉村令慧, 山崎健一, 南拓人, 澤山和貴, 大志万直人
  • Organizer: 2022年度 Conductivity Anomaly 研究会