[S-VC29] 火山の熱水系

[SVC29-08] MT法を用いた深部低比抵抗体のイメージング能力について：超臨界地熱資源探査の例

*石須 慶一¹、小川 康雄¹、茂木 透¹、山谷 祐介²、内田 利弘² (1.東京工業大学、2.産業技術総合研究所)

キーワード：比抵抗、電磁探査、地熱、超臨界地熱システム、葛根田

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.