3D inversion of HELITEM data in geothermal area, Japan

Abstract

For the exploration of geothermal resources, helicopter-borne time-domain electromagnetic (HELITEM) survey was conducted over the Kuju and Kirishima Areas in Kyusyu by Japan Oil, Gas and Metals National Corporation (JOGMEC). HELITEM data were analysed by using EMflow, which is widely used for the qualitative interpretation of airborne electromagnetic (AEM) data. For the quantitative interpretation of the HELITEM data, which we propose in order to evaluate the geothermal potential, we have performed rigorous 3D inversion with EMVision ® for subset of the HELITEM data acquired along two lines in the Kuju survey area. Magnetotelluric (MT) and Controlled-source audio-frequency MT (CSAMT) surveys have been conducted in the same area, and we have compared results in order to validate the 3D inversion technology (EMVision ® ). It was demonstrated that the rigorous 3D inversion with EMVision ® can be properly used for the quantitative interpretation of HELITEM data. One can clearly see the detailed geoelectrical structure with realistic and reasonable resistivity values, and the technology has been proven to be fast and efficient for large amounts of AEM data in a complex geological setting.