July 13, 2020
Distributed Array surveys (DAS) are recommended for deep complex anisotropic targets where near surface resolution is a lower priority. Hardware advances over the past decade make it possible to to acquire large quantities of data in a relatively short amount of time. DAS are often combined with standard 2d Spectral IP/Resistivity arrays for optimal resolution and coverage.
IRIS Instruments V-Fullwaver
There are several types of Full 3d IP/Resistivity setups and several manufacturers that provide receivers that can read various configurations. Receivers with three potential electrode connections can allow 2D orthogonal setups at each receiver for P1, P2 and P3.
Adding to the possibilities, a reference wire can be attached between a common electrode at each receiver to allow a number of post-processing calculations and QA/QC, such as noise canceling, before getting to the point of inversion modeling. Software such as UBC 3d, used by ClearView Geophysics Inc. for decades, can handle these large complex datasets.
Most receivers are full-waveform so that standard 690ms-1050ms time slices can be used for direct comparison to conventional IP survey data sets. Other processing such as time-series analyses and accurate spectral data can be acquired to further resolve near surface and narrower targets. Data can be supplemented with cross-hole IP/Resistivity for refined 3d models. Spectral data from conventional 2d arrays supplement the interpretation. That is, the DAS survey is carried out at the same time as standard Spectral IP/Resistivity 2d surveys.
The possibilities are endless with modern instrumentation, limitless computer storage and solid-state processing speed.