The paper from Geotech Ltd. has been awarded as the Best Paper in the Mining and Geothermal sessions at the 2015 SEG annual meeting in New Orleans: “Airborne Inductively Induced Polarization effects in and their removal from the VTEM data from Mirny, Russia”.
As the Committee Chair says: “Out of all the papers presented, it was voted as highest ranking by the session participants”.
The paper is about airborne inductively induced polarization (AIIPTM) effects, which is expressed in the form of numerous negative transients, and observed in the VTEM helicopter time-domain EM (TDEM) data from Mirny, Russia. VTEM data reflect mainly two physical phenomena in the earth: i) electromagnetic induction and ii) airborne inductively induced polarization (AIIP) related to the relaxation of polarized charges in the ground. Typical AIIP effects in the VTEM data from Mirny corrupt only the early to mid-time channels, from 55 microsec to 400 microsec. Moreover, the earliest few time channels, from 18 microsec to 48 microsec, are not affected by AIIP, because the IP effect takes a finite time to build up. Cole-Cole analysis of the AIIP affected VTEM data showed that the frequency factor and the time constant are close to 0.8 and 0.0001s, respectively. Since the earliest time channel data are not affected by AIIP, the resistivity of the shallow ground can still be precisely determined. As a result, the purely inductive VTEM decay can be accurately modelled and used to remove the AIIP effect from later time-channels.