3D resistivity imaging of buried oil-and tar-contaminated waste deposits

摘要

This case study illustrates the advantages of 3D resistivity surveys for mapping concealed, highly irregular tarpits containing industrial waste, mainly from oil reprocessing and coal mining. Previous geophysical surveys and intrusive sampling had confirmed the irregular geometry of the pits and the heterogeneity of the waste products but, at the time, 3D resistivity surveys were not a practical option. With recent advances it has now been possible to obtain a more accurate spatial model based on 3D resistivity datasets and full 3D inversion. The survey was carried out using a network of individual lines within a grid measuring 95 m by 95 m. The data were modelled using a 3D inversion program a(RES3DINV) and the resulting resistivity distributions were then displayed as volumetric 3D tomograms. Three zones of low resistivity were identified as pits 4N, 4S and 1A respectively. The 3D model provided valuable diagnostic information on the geometry of the pits; the distribution and nature of in-filling waste materials and zones where leachate had infiltrated the bedrock. The results were confirmed by ground-truth derived from trial pits, cone penetration tests, historic photographs and boreholes.