1996 Fiscal Year Final Research Report Summary
Fundamental Design Methogology for Geothermal Energy Extraction -Establishment of Fractal Fracture Mechanics and Its Application-
| Project/Area Number |
05232101
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| Research Category |
Grant-in-Aid for Scientific Research on Priority Areas
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| Allocation Type | Single-year Grants |
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| Research Institution | Tohoku University |
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Principal Investigator |
NAKATSUKA Katsuto Tohoku Univ., Faculty of Engng, Prof., 工学部, 教授 (60005345)
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| Co-Investigator(Kenkyū-buntansha) |
HASHIDA Toshiyuki Tohoku Univ., Faculty of Engng, Assoc.Prof., 工学部, 助教授 (40180814)
YAMASAKI Nakamichi Kochi Univ., Faculty of Science, Prof., 理学部, 教授 (50036589)
HAYASHI Kazuo Tohoku Univ., Institute of Fluid Science, Prof., 流体科学研究所, 教授 (30111256)
TAKAYASU Hideki Tohoku Univ., Graduate School of Info.Sci., Prof., 大学院・情報科学研究所, 教授 (00183062)
YUSA Yuki Kyoto Univ., Faculty of Science, Prof., 理学部, 教授 (90025403)
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| Project Period (FY) |
1993 – 1995
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| Keywords | Geothermal Energy / Fractals / Subsurface Crack / Hydraulic Stimulation / Thermal Design / Multi-crack / Fracture Mechanics / Water-Rock Interaction |
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| Research Abstract |
The objective of the present research program is to develop a numerical model for predicting long-term performance of thermal extraction from geothermal reservoirs. The research program consists of the following major subjects, and three research group (RG) are formed to examine each research subject :
(1) Characterization of subsurface natural fracture networks based on fractal geometry (RG : A01)
(2) Modeling of mechanical responses of fracture-type rock mass stimulated by hydraulic fracturing (RG : A02)
(3) Characterization of water-rock interaction (RG : A03)
The following results are obtained from the RG activities. Firstly, a fractals-based method has been worked out which allows the generation of a 3D fracture network using a well logging data obtained from the reservoir considered. Then, numerical models have been developed to analyze the mechanical behavior of the geothermal reservoir during hydraulic stimulation process, steady state fluid flow at circulation stage, and heat extr
… More
action through the fractured rock mass, based on the generated fractal fracture network and the inputs measurable from field data. The numerical model of hydraulic stimulation allows to take into account the shear displacements of the stimulated fracture as well as the openings at a given treatment pressure, and to calculate the amount of fluid needed to stimulate a given volume of rock. The numerical models allows to predict the shape of the stimulated region, the recovery rate of circulating fluid, and then the long-term temperature variation of produced fluid. Finally, we have established a computer simulation model for predicting long-term performance of thermal extraction from a fracture network type geothermal reservoir, on the basis of the above-mentioned fundamental results. The model has been applied to examine the effect of geothermal reservoir size on the thermal output. International co-operative joint research programs have also been conducted to support the present study.
Three international symposia have been held to disseminate our research results in addition to annual research group meeting. Furthermore, we have issued ten news-letters to facilitate the information change within the research groups. Less
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[Publications] Wang, Y., Yamasaki, N., Nakatsuka, K., Takahashi, H., Yanagisawa, K., Ishida, T.and Nishiuchi, S.: "Simulation test of granite alteration by flow system autoclave" Proc.First.Int.Conf.Solvo-Thermal Reactions. 1. 174-177 (1994)
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