Electrical resistance tomography using steel cased boreholes as electrodes

摘要

Electrical resistance tomography (ERT) using multiple electrodes installed in211u001eboreholes has been shown to be useful for both site characterization and process 211u001emonitoring. In some cases, however, installing multiple downhole electrodes is 211u001etoo costly (e.g., deep targets) or risky (e.g., contaminated sites). For these 211u001ecases we have examined the possibility of using the steel casings of existing 211u001eboreholes as electrodes. The first case we investigated used an array of steel 211u001ecasings as electrodes. This results in very few data and thus requires additional 211u001econstraints to limit the domain of possible inverse solutions. Simulations 211u001eindicate that the spatial resolution and sensitivity are understandably low but 211u001eit is possible to coarsely map the lateral extent of subsurface processes such as 211u001esteam floods. A hybrid case uses traditional point electrode arrays combined with 211u001elong-conductor electrodes (steel casings). Although this arrangement provides 211u001emore data, in many cases it results in poor reconstructions of test targets. 211u001eResults indicate that this method may hold promise for low resolution imaging 211u001ewhere steel casings can be used as electrodes.