A Very-Short Offset Transient Electromagnetic Method with a Grounded-wire Source

摘要

#$%^&*AU2020100496A420200514.pdf#####Abstract The invention discloses a very-short offset transient electromagnetic method with grounded-wire source, and belongs to the technical field of transient electromagnetic detection methods. A traditional grounded-wire source transient electromagnetic detection is performed at an offset greater than 0.7 times the target depth, and there is no related research on the detection of the offset range less than 0.7 times the target depth. In order to give full play to the advantages of high signal intensity and high detection efficiency in the offset range less than 0.7 times the target depth, this patent proposes a very-short offset grounded-wire source transient electromagnetic method (VOTEM), which is to derive VOTEM multi-component response expression on the surface of layered earth based on a point charge infinitesimal theory, to study the multi-component response characteristics and resolution capabilities, the optimal observation range, the electromagnetic induction in a near-field source area, as well as the sounding mechanism and additional effects, and to provide basis for an actual VOTEM measurement. It is helpful to promote the development of a whole (offset) range observation mode of the grounded-wire source transient electromagnetic methods.1/18 d gd p, d-*a Fig. 1