| Title | Geoelectrical Investigation of the Kakkonda Geothermal Field, Northern Japan |
|---|---|
| Authors | Toshihiro Uchida, Yasuo Ogawa, Shinichi Takakura and Yuji Mitsuhata |
| Year | 2000 |
| Conference | World Geothermal Congress |
| Keywords | magnetotelluric method, two-dimensional inversion, resistivity structure, reservoir structure, Kakkonda geothermal field |
| Abstract | The Geological Survey of Japan (GSJ) and the New Energy and Industrial Technology Development Organization (NEDO) have carried out magnetotelluric (MT) surveys with a dense station coverage in the Kakkonda geothermal field, northern Japan. The Kakkonda geothermal plant is utilizing steam and hot water produced from reservoirs at depth of 1000 - 3000 meters. A very young granitic rock was found at a depth of approximately 3 km. MT measurements have been done on several survey lines covering the geothermal field in order to delineate the resistivity structure of the reservoir and the granite. Due to the complicated resistivity structure, dominant strike direction of the impedance rotates from higher frequency to lower. Shallow parts of twodimensional models have good agreement with reservoir structure and resistivity logging data, showing very conductive zone of the clay-rich cap layer of the reservoir. Main body of the young granite was interpreted as a low-resistivity zone. However, due to the three-dimensionality, some of the 2-D models seem to be poor in delineating resistivity structure in deeper portions. |