1999 Fiscal Year Final Research Report Summary
Development of a system to measure fracture aperture of artificial fracture produced in-situ
| Project/Area Number |
09555321
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
資源開発工学
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| Research Institution | Yamaguchi University |
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Principal Investigator |
MIZUTA Yoshiaki Yamaguchi University, Faculty of Engineering, Professor, 工学部, 教授 (20107733)
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| Co-Investigator(Kenkyū-buntansha) |
YAMAGUCHI Tsutomu National Institute for Resources and Environment, Geotechnology Department Geo-Energy Division, Chief, 地殻工学部, 地殻エネルギー研究室長
OHNISHI Yasunori Yamaguchi University, Faculty of Engineering, Research Associate, 工学部, 助手 (00274184)
ISHIDA Tsuyoshi Yamaguchi University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (10232307)
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| Project Period (FY) |
1997 – 1999
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| Keywords | Kamioka Mine / Underground Measurement / Fluid Injection Experiment / Metal Packer / Fracture Aperture / Rock Surface Displacement / Numerical Simulation / 3D Boundary Element Method |
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| Research Abstract |
The registered investigators have developed a special double packer. In hydraulic fracturing operation, an opening and closing behavior of a fracture is related to in-situ stress state. A purpose of new packer was to measure the fracture opening directly. The new packer consisted of two co-axial pipes that move independently. As sealing elements were fixed to each of two pipes, fracture opening could be measure by relative displacements of two co-axial pipes. Two types of the materials as sealing element were examined. One of the materials was rubber and the other was lead. The former was named rubber-seal packer, and the latter is named metal-seal packer.
A conventional double packer, the rubber-seal packer and the metal-seal packer were used for in-situ experiment carried out in the Kamioka mine in 1998. IN this mine, a hydraulic fracturing experiment in order to estimate an earth stress was done using a borehole that was drilled horizontally from a gallery in 1996. The newly developed packers were used to re-open the pre-existed artifical fracture.
The result of the metal-seal packer experiments showed that relative displacements of two co-axial pipes had a good correlation with the gallery wall expansion that was measured at vicinity of the borehole. The shut-in pressure, that is thought to be equivaient to a magnitude of normal stress component, was estimated from the relative displacements of two co-axial pipes. This shut-in pressure estimated from the metal-seal packer agreed well with those determined from the Muskut method and Hayashi & Haimson method.
Numerial simulation of displacement variations of fracture aperture and gallery wall surface, which were caused by fluid injection, was carried out by using three dimensional boundary element method. Numerical results nearly agreed with the measured results.
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