Possibilities and specific features of pulsed inductive electromagnetic sounding of shallow sections under complex geological conditions

摘要

A new high-resolution technology of pulsed induction electrical survey is developed for sounding with small (2-30 m) loops in the depth interval from 0.5 to a few hundred meters (in its possibilities, this technology is unprecedented). The specific feature of the proposed technology is that it is applicable not only to well conducting and contrasting objects but also to sounding of low conductivity and low contrast geological objects (including those overlain by high and low resistivity screens) and to identification of thin and low contrast beds. The minimum initial time of recording the useful signal is 350 ns at a current of 3 A. The accuracy of the location of an interface between layers attains 2-5%. The interpretation results are close to electrical logging data. Testing methodological studies were carried out in the Malo-Batuobinskaya diamondiferous province of the Yakutian permafrost zone and in the inspection of high embankments and two landslides in a railroad zone. The new technology can be used in the presence of intense electromagnetic interferences (in particular, along electrified railroad tracks).