Validation and Evaluation of an Estimation Method for Deep Thermal Structures Using an Activity Index in Major Geothermal Fields in Northeastern Japan

Yota Suzuki, Hirofumi Muraoka and Hiroshi Asanuma
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Yota Suzuki: Fukushima Renewable Energy Institute, National Institute of Advanced Industrial Science and Technology, Koriyama, Fukushima 963-0298, Japan
Hirofumi Muraoka: Institute of Regional Innovation, Hirosaki University, Aomori 030-0813, Japan
Hiroshi Asanuma: Fukushima Renewable Energy Institute, National Institute of Advanced Industrial Science and Technology, Koriyama, Fukushima 963-0298, Japan

Energies, 2020, vol. 13, issue 18, 1-13

Abstract: A considerable number of rock bodies with varying percentages of supercritical fluid exist around the brittle–ductile transition (BDT) zone at a depth of several kilometers from the surface of the Earth, in northeastern Japan. As the BDT zone in the granitic basement of the continental crust is estimated to occur at about 380 °C, the identification of the depth corresponding to 380 °C is important to utilize the thermal energy inside the “supercritical geothermal systems”. In this study, we focused on an estimation method to determine the depth of the isothermal layer corresponding to 380 °C, using the activity index (AI) obtained from the maximum-temperature data of the geothermal wells and hot springs. The thermal profiles of deep and hot exploration boreholes and the hypocentral distribution of natural earthquakes were used to evaluate the characteristics and accuracy of the deep thermal structure, using the activity index. The estimated depth corresponding to 380 °C tended to be higher than the actual depth, with a maximum possible estimation error of approximately 9.7 km. Distribution maps showing the depth of the isothermal layer corresponding to 380 °C were created for six major geothermal fields in northeastern Japan, using the results from this study.

Keywords: geothermal energy; geothermal exploration; geothermal mapping; brittle–ductile transition; seismicity; hydrothermal convection; supercritical geothermal resources (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
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Citations: View citations in EconPapers (1)

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