For traditional surface based EM methods the presence of metallic well casing has been problematic. Well casing and surface piping distribute supplied and ambient signals in complex ways, and field data collected at sites with well casings were complex and often uninterpretable with existing tools. We generally avoided these places. The logging industry had a different take. They developed tools to operate within the well casings to interrogate the condition of well completions and to log the formation conductivity adjacent to the wellbore. In the process we have learned how the well casing behaves in the presence of an EM field and how to numerically model the process.