[S-VC29] Hydrothermal systems of volcanoes

[SVC29-08] Ability of the magnetotelluric method to image a deep conductor: Exploration of a supercritical geothermal system

*Keiichi Ishizu¹, Yasuo Ogawa¹, Toru Mogi¹, Yusuke Yamaya², Toshihiro Uchida² (1.Tokyo Institute of Technology, 2.National Institute of Advanced Industrial Science and Technology)

Keywords:Resistivity, Electromagnetic survey, Geothermal energy, supercritical geothermal system, Kakkonda

Fluids trapped under supercritical conditions are attractive unconventional geothermal resources that can yield much higher well-productivity. The magnetotelluric (MT) method can image supercritical fluids as deep conductors. However, MT imaging of a deep conductor strongly depends on the conductor geometries and overlying clay layers. The MT ability to image a deep conductor should be clarified to understand the MT usefulness for exploring supercritical fluids and correctly relate the imaged conductor to supercritical fluids. Therefore, this study investigated the MT ability to image a deep conductor of supercritical fluids using numerical tests. The numerical tests used a conceptual resistivity model of a promising supercritical geothermal system in the Kakkonda area, northeast Japan. The test results prove that the MT method is useful for revealing the deep conductor of promising supercritical fluids. The results also showed that the MT ability to image deep conductors strongly depends on the size and depth of the target conductor and the thickness of overlying clay layers. The findings from the test results help to relate deep conductors imaged by the MT method to supercritical geothermal systems.