Optimizing Semi-Airborne Electromagnetic Survey Design for Mineral Exploration

Abstract

As semi-airborne mineral exploration has a limited budget, it is critical to design experimental procedures that generate data to maximize desired information. We investigated the effects of transmitter–receiver geometries for a variety of anomalies and semi-airborne layouts. Our simulations indicated that flight line spacing of 200 m and a point distance of 100 m provides the optimal trade-off between coverage and survey progress for various targets. Based on the target size and distance between the transmitter and the target, the transmitter length should be at least equal to the length of the target. However, where the distance between the transmitter and the target is more than 1 km, the transmitter length should be at least two or three times the target size. Of similar importance are the location and direction of the transmitter cables, which can have a significant impact on the result of inversion and should be parallel to the target strike. By using more than one transmitter, better results can be obtained. If the strike of the target is known, transmitters should be parallel to each other, and if not, it is better to use perpendicular transmitters. The results of this study showed that the optimal distance between transmitters is 3 km. Our simulations showed that it is even possible to recover targets just below the transmitter in corresponding areas of masked data.

Research note: A comparison between normalized controlled‐source electromagnetic field components and transfer functions as input data for three‐dimensional non‐linear conjugate gradient inversion

“…To enable the simulation of impedance and vertical magnetic transfer functions (VMTF) tensors, we integrate a second grounded-wire source perpendicularly oriented to the original source. In order to have a sufficiently homogeneous primary electromagnetic (EM) field across the entire station array, we take measurement recommendations from Nazari et al (2023) into account and extend the source lengths to 3 km.…”

Efficient 3D Frequency Semi-Airborne Electromagnetic Modeling Based on Domain Decomposition

“…The FV method can effectively resolve complex geological structures using orthogonal Delaunay-Voronoï unstructured grids, as its implementation is complicated and requires high mesh quality [29]. To be suitable for modeling complex terrain and geologic structures, the FE method, using unstructured grids, has been widely used in SAEM modeling [30,31].…”