Development of the Vertical Electro Magnetic Profiling (VEMP) Method

As a part of the "Deep-Seated Geothermal Resources Survey" project being undertaken by the NEDO, the Vertical ElectroMagnetic Profiling (VEMP) method is being developed to accurate1y obtain deep resistivity structure. The VEMP method takes multi-frequency three-component magnetic field data in an open hole well using controlled sources (loop sources or grounded-wire sources) emitted at the surface. Numerical simulation using EM3D (Wannamaker et al., 1984) demonstrated that phase data of the VEMP method is very sensitive to resistivity structure and the phase data will also indicate presence of deep anomalies. Forward modelling was also used to determine required transmitter moments for various grounded-wire and loop sources for a field test using the WD-1 well in the Kakkonda geothermal area (Miura et al., 1994). Field logging of the well was carried out in May 1994 and the processed field data matches well the simulated data.