[S-VC33] Hydrothermal systems of volcanoes

[SVC33-01] Investigation of supercritical geothermal reservoir by magnetotelluric method

*Keiichi Ishizu¹, Yasuo Ogawa¹, Keishi Nunohara², Noriyoshi Tsuchiya², Masahiro Ichiki², Hideaki Hase¹, Wataru Kanda¹, Shin'ya Sakanaka³, Yoshimori Honkura¹, Yuta Hino¹, Kaori Seki¹, Kuo Tseng¹, Yusuke Yamaya⁴, Toru Mogi¹ (1.Tokyo Institute of Technology, 2.Tohoku University, 3.Akita University, 4.National Institute of Advanced Industrial Science and Technology)

Keywords:Resistivity, Electromagnetic survey, Geothermal energy, Supercritical geothermal system, Yuzawa

Subsurface fluids in a supercritical state (high temperature and pressure of >374°C and >22.1 MPa) have gained attention as next-generation geothermal resources because they can offer significantly more energy than conventional geothermal fluids with temperatures <350°C. Supercritical geothermal fluids are believed to be found in various volcanic areas worldwide. Although an understanding of the spatial distribution and fluid fraction of supercritical fluids is necessary for their resource assessment, the spatial distribution and fluid fraction of supercritical geothermal reservoirs are poorly understood. Therefore, we used the magnetotelluric (MT) method to obtain information on the spatial distribution and fluid fraction of a supercritical geothermal reservoir in the Yuzawa geothermal field, northeastern Japan. Our MT data revealed a potential supercritical geothermal reservoir of 3 km (width) × 5 km (length) at a depth of 2.5–6 km with a fluid fraction estimated to be 0.5–2% and a salinity of 5–10 wt%.