International Journal of the JSRM
Online ISSN : 2189-8405
Cloud-fracture networks as a means of accessing superhot geothermal energy
Noriaki WATANABEKiyotoshi SAKAGUCHIRyota GOTOTakuya ISHIBASHIYouqing CHEN
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ジャーナル オープンアクセス

2020 年 16 巻 1 号 p. 1-4

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This article is a summary of the authors’ published article (Watanabe et al. 2019), which is an open access article distributed under the terms of the Creative Commons CC BY license. Superhot geothermal environments (above ca. 400 ℃) represent a new geothermal energy frontier. However, the networks of permeable fractures capable of storing and transmitting fluids are likely to be absent in the continental granitic crust. Here we report the first-ever experimental results for well stimulation involving the application of low-viscosity water to granite at temperatures ≧400 ℃ under true triaxial stress. This work demonstrates the formation of a network of permeable microfractures densely distributed throughout the entire rock body, representing a so-called cloud-fracture network. Fracturing was found to be initiated at a relatively low injection pressure between the intermediate and minimum principal stresses and propagated in accordance with the distribution of preexisting microfractures, independent of the directions of the principal stresses. This study confirms the possibility of well stimulation to create excellent fracture patterns that should allow the effective extraction of thermal energy.

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© 2020 Japanese Society of Rock Mechanics
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