oa Three-Dimensional Magnetotelluric Analysis for the Kakkonda Geothermal Field

NEDO began the “Deep-Seated Geothermal Resources Survey" in Kakkonda (Iwate, Japan) from Fiscal year 1992 and the pilot survey well WD-1a reached 37,929m and over 500 degrees C in 1995. In1996, NEDO drilled a side-trucking well WD-1b and hit several high permeability zones. As the number of remaining shallow geothermal reservoirs diminishes through exploitation, the geothermal industry must turn its efforts towards the detection and delineation of deep-seated geothermal reservoirs. As part of NEDO project, an extensive tensor magnetotelluric (MT) survey was carried out over the Kakkonda area in 1998. 76 sites were arranged in four profiles to cross a major structural feature. To curtail spatial aliasing, the electric dipoles along each profile were deployed contiguously. The resistivity model within the area was derived by 3-D inversion analysis.