Multichannel, full waveform and flexible electrode combination resistivity-imaging system

Abstract

The development of a new multichannel and multielectrode, full waveform resistivity acquisition system is presented. This system, which can be built in any electronics workshop without major difficulties, allows for large data collection capacity and flexibility but without the sacrifice of channels, as in most other systems that use a preselected array. A superior interpretation quality is enabled by the increased data and the monitoring of noise through full waveform display. The proposed hardware is robust because no electronics need to be installed in the cable. Therefore, it is suitable for 2D or 3D surface or crosshole tomography. A major feature of the data collection strategy is to capture all of the electrode combinations subject to having one current electrode in each cable. This is efficient because there is no extra cost in doing this. It is an automatic process; one does not have to make any prior decisions as to what electrode combinations to use. The data sets collected with this strategy are suitable for an inversion process involving a large amount of data because the number of voltage values measured using a couple of current electrodes is maximized. Synthetic modeling shows that the proposed approach allows for better imaging of the subsurface than with conventional arrays and the results are comparable to results obtained with an optimized experimental design strategy. A field experiment illustrates the effectiveness of the presented strategy. The inverted image of the subsurface is well-correlated with the available borehole information.