Underground Cavity Investigation Using 3D Electeical Resistivity Imaging Method


Oil Engineering Department, Engineering Faculty, Islamic Azad University, Masjed-i-Solaiman Branch, Masjed- i-Solaiman, Iran


     Applicability of three kinds of electrode configurations to delineate an underground cavity was studied. A 3D resistivity imaging survey was carried out along eight parallel lines using pole-pole, pole-dipole, and dipole-dipole arrays with 1 m minimum electrode spacing. Roll-along measurements were carried out to cover a rectangular grid. The 3D least squares algorithms based on the robust inversion method, was used in the inversion of the apparent resistivity data sets. To obtain the better results, 3D joint inversion of the pole-pole + pole-dipole and pole-pole + dipole-dipole datasets were performed as well as the pole-dipole + dipole-dipole datasets. In this case, both horizontal and vertical dimensions of subsurface cavity were resolved. The resulting model with the ones obtained from each array was compared separately. The result showed the joint inversion improves the investigation depth obtained by the survey. However the horizontal resolution in shallow layers remains acceptable.


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