Analysis of a guided wave along a conducting structure in a borehole

A guided wave along a borehole is often observed in borehole radar measurements. These guided waves deform the antenna pattern and can cause artefacts in radar measurments. A water-filled borehole or a conducting logging cable can function as a waveguide for electromagnetic waves under some conditions. We describe the theoretical characteristics of such a guided wave in a borehole and compare them with our experiments. the measured signal discussed was obtained with a directional borehole radar. This radar uses a cyclindrical conformal array antenna as receiver and is a model of a conducting structure in a borehole. The induced field around the borehole was compared with the theory. the most fundamental symmetrical and asymmetrical modes were TM₀₁ and HE₁₁, and they were identified in the measured signals using time-frequency distribution analysis and by observation f the azimuthal field distribution of the magnetic field.