A scale model of the through-casing resistivity measurement

In recent years,the possibility of resistivity logging in cased wells has attracted much interest. This study draws on the basic principles of through-casing resistivity (TCR) measurements. Based on the principle of TCR theory, we designed a TCR tool and performed TCR experiments. Computer simulation code was written to provide expected values. In the experiments, we used two formation beds with a high contrast in resistivity, an airbed and a saline waterbed. We measured two sets of logs, which gave distinguishable readings between air and saline water. The measured results were compared to values predicted by the computer model. We found that the distribution of the leakage current was not uniform in our experiment, which was unexpected. However, these results can be used in the future to improve TCR measurements and interpretation.