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成果報告書詳細
管理番号20190000000189
タイトル*平成30年度中間年報 超臨界地熱発電技術研究開発 超臨界地熱資源への調査井掘削に資する革新的技術開発 革新的超臨界地熱場観測技術の研究開発
公開日2019/5/17
報告書年度2018 - 2018
委託先名一般財団法人エンジニアリング協会 一般財団法人ファインセラミックスセンター 国立大学法人京都大学
プロジェクト番号P18008
部署名新エネルギー部
和文要約
英文要約Title: Research and Development of Supercritical Geothermal Power Generation Technology /
Innovative Technology Development Contributing to Pilot Well Drilling into Supercritical Geothermal Resources /
Research and Development of Innovative Supercritical Geothermal Field Characterizing Technology (FY2018 – FY2020)
FY2018 Annual Report

1) Preliminary study to examine feasibility of seismic method to characterize supercritical water reservoirs
In November 2018, we conducted a feasibility study in the Medipolis geothermal field, Kyushu, Japan. We installed a fiber-optic cable at a 977 m depth in the borehole. We measured the temperature and acquired seismic data in the borehole using distributed temperature sensor (DTS) and distributed acoustic sensor (DAS) modes, respectively. The highest measured temperature was 264 °C at the 914 m depth. The DAS data were acquired at 1 m intervals. We also installed 20 sets of seismometers on the ground surface in the study field. Continuous seismic monitoring via the DAS and surface seismometers was performed for 4.5 days. From the seismic system, seven natural earthquakes occurred in the Kyushu region. One of the earthquakes of M 5.2 at 100 km south of the DAS system occurred at a 123 km depth and was observed at the entire depth of 977 m to 0 m. There was less or no attenuation of seismic amplitudes at the high temperature zone, and Vp was approximately 4 km/s at this zone. Using a semblance analysis of all earthquakes, a Vp profile in the borehole was obtained. Horizontal components of surface seismometers showed a P-to-S converted phase. A possible cause of the P-to-S conversion is the deep geothermal reservoirs in the Medipolis area.

2) Development of analytical and imaging technology for the supercritical water reservoirs.
We tested waveform inversion to characterize geothermal reservoirs. We used a famous MARMOUSI-I model. Assuming low Vp, Vs and density reservoir at 2.5 km depth and using residual waveforms, we successfully retrieved the assumed reservoir.
We also tested high Vp/Vs model located at 4km depth assuming Medipolis field. We assumed seismic system of 1km depth DAS and 2km long surface seismic array. Because the field size is 2km wide, the aperture of seismic array is not large, and it seems affecting resolution imaging characteristics.

3) Development of optical fiber under supercritical water circumstance
We tested the durability of non-coated, carbon-coated and gold-coated fibers under supercritical circumstances such as 500°C and 25 MPa. Non-coated fiber was heavily damaged by 10 hours test. The carbon-coated fiber was also damaged by 10 hours test. The gold-coated fiber showed that the skin of fiber remained as non-damaged state by 100 hours test. The attenuations loss input light of the gold-coated fiber after the100 hour test should be examined.
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