The Resistivity Structure of the Deep Geothermal Reservoir in Kakkonda - the Exploration by Borehole EM and MT/CSAMT Surveys

Abstract

Since 1992, NEDO has undertaken the Deep Seated Geothermal Resources Survey Project in Kakkonda (Iwate, Japan). The pilot survey well WD-la reached 3,729 m depth and 550 degrees C in 1995. In 1996, NEDO drilled a side-track well WD-lb and hit several high penneability zones. Geophysical surveys (MT, reflection seismic, micro-earthquake, etc.) and geophysical logging has been carried out by JMC and NEDO during field development and this project.We compiled and compared the results of MT, micro-earthquake and well data, with the results from new exploration techniques using electromagnetic utilizing wellbore methods named MAIL (Multi-frequency Array Induction Logging ) and VEMP (Vertical Profiling ) that were developed in this project. The results suggest that there is high probability of open fractures in the region correlating with the steep resistivity gradient.