Pitfalls and refinement of 2D cross-hole electrical resistivity tomography

Haoran Wang, Chih Ping Lin*, Hsin Chang Liu

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

As the conventional surface ERT method is limited by its low resolution at depth, cross-hole electrical resistivity tomography (CHERT) method is increasingly used in the field of geo-environment and hydrogeology whenever possible. Researches regarding CHERT configurations and some negative effects in this method have been useful in survey planning and data interpretation. Nevertheless, some issues remained to be resolved before a standard guideline can be drawn up for conducting CHERT. The symmetric effect was recently pointed out as a major issue in resistivity tomography involving borehole measurements including both borehole-to-surface and cross-hole methods. Symmetrical artifacts emerge for certain types of electrode configuration, which are often desired for better resolution. In this study, the symmetric effect was further investigated in a general two-hole CHERT layout, which is more frequently used in the field. The influence of symmetric effect is found to manifest when the assumption of boundary condition in the inversion is incorrect. The effect of electrode configuration and inversion scheme was further examined and the extended inversion model was found to be more suitable for CHERT data inversion. In particular, the optimal extended range outside the boreholes on each side was shown to be 0.25 times the borehole depth. To mitigate the symmetric effect, a more practical optimal array was proposed. These new suggestions were further verified by a field example.

Original languageEnglish
Article number104143
JournalJournal of Applied Geophysics
Volume181
DOIs
StatePublished - Oct 2020

Keywords

  • Cross-hole ERT
  • Inversion range
  • Symmetric effect

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