Abstract
The Otake Geothermal Power Station (12.5MW) is located in Otake-Hatchobaru geothermal field, one of the most active geothermal fields in Japan. This power station has been operating since 1967 and maintaining a stable operation since 1988 using 4 production wells. However, the electric power output has declined since 2006 due to the decreasing mass flow of the main production well (O-22). In 2010, a magnetotelluric (MT) survey was conducted to detect a drilling target for a make-up production well. In 2012, make-up well O-21 was drilled to the target detected in the MT survey and it successfully discharged steam and water. As a result of the successful drilling of the make-up well, the power output of the Otake Geothermal Power Station recovered to its 2006 level of output.
