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1997 Fiscal Year Final Research Report Summary

Characterization of a Geothermal Reservoir Crack Based on the Analysis of Dynamic Response of a Crack Filled with Fluid

Research Project

Project/Area Number 08650086
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Materials/Mechanics of materials
Research InstitutionTohoku University

Principal Investigator

HAYASHI Kazuo  Tohoku University, Institute of Fluid Science, Professor, 流体科学研究所, 教授 (30111256)

Co-Investigator(Kenkyū-buntansha) NAGANO Koji  Muroran Institute of Technology, Faculty of Engineering, Research Associate, 工学部, 助手 (90212109)
NIITSUMA Hiroaki  Tohoku University, Graduate School of Engineering, Professor, 工学部, 教授 (90108473)
Project Period (FY) 1996 – 1997
KeywordsGeothermal Energy / HDR / Geothermal Reservoir Crack / Characterization of Crack / AE / Elastic Wave
Research Abstract

The objective of the present project is the establishment of a method for characterizing the geometrical and physical characteristics of a fluid-filled geothermal reservoir crack. Firstly, we have proposed a model for a fluid-filled crack within an elastic medium with permeation of fluid. The upper and lower surfaces are in partial contact to each other, thus there exists interface stiffness along the crack, and also the fluid viscosity is taken into account. It has been revealed that, in the case that the partial contact is absent, the eigen angular frequencies are highly dependent on the aspect ratio (the ratio between the crack size and aperture), when the viscosity and permeability are small. However, in the case that the partial contact is present, the eigen angular frequencies are highly dependent on the interfacial stiffness. When the permeability is large as that of a formation in a usual geothermal field, then the effects of the permeability and viscosity become stronger. In order to get clear understanding of the effects of permeability and fluid viscosity, we have analyzed the case that the rock is rigid and have found that there exists an optimum value of fluid viscosity which gives the largest pressure response. The optimum value of fluid viscosity is mostly determined by the permeability of the formation. Inversely speaking, it is possible to get the maximum pressure response by choosing the fluid with the optimum value of viscosity depending on the formation permeability. Finally, on the basis of the results of the analysis, we have set up the inverse problem to estimate the aspect ratio of the crack, the initial crack aperture and the interfacial stiffness by using a newly introduced objective function.

  • Research Products

    (10 results)

All Other

All Publications (10 results)

  • [Publications] K.Hayashi: "Radiation pattern of elastic waves induced by the motion of fluid in a two-dimensional reservoir crack" Proc.6th Conf.AE/MS Geol.Struc.Mat.521-532 (1998)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] K.Hayashi: "Dynamic responses of a fluid-filled geothermal reservoir crack-effect of the aspect ratio of the reservoir crack-" Progress in Acoustic Emission VIII. 104-109 (1996)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] K.Hayashi: "Dynamic response of fluid inside a penny shaped crack" Geothermal Resources Council Transaction. 21. 577-584 (1997)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] K.Hayashi: "Dynamic response of fluid within a reservoir crack in a rock mass connected to a wellbore" Abs.Wrksp.Induced Seis.27-28 (1996)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 伊藤 伸: "地下き裂の振動特製に及ぼす流体の粘性と岩体の透水性の影響" 日本非破壊検査協会第11回アコースティック・エミッション総合コンファレンス論文集. 131-136 (1997)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] K.Hayashi: "Radiation pattern of elastic waves induced by the motion of fluid in a two-dimensional reservoir crack" Proc.6th Conf.AE/MS Act.Geol.Struc.Mat.521-532 (1998)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] K.Hayashi: "Dynamic responses of a fluid-filled geothermal reservoir crack -effect of the aspect ratio of the reservoir crack-" Progress in Acoustic Emission. VIII. 104-109 (1996)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] K.Hayashi: "Dynamic Response of fluid inside a penny shaped crack" Geothermal Resources Council Transaction. 21. 577-584 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] K.Hayashi: "Dynamic Response of fluid within a reservoir crack in a rock mass connected to a wellbore" Abs.Wrksp.Induced Seis.27-28 (1996)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] S.Ito: "Effect of fluid viscosity and permeability of rock on Dynamic Responses of a geothermal reservoir crack" 1997 National Conference on Acoustic Emission. 131-136 (1997)

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 1999-03-16  

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