Electromagnetic Shielding of Sources within a Metal-Cased Bore Hole

An abbreviated derivation is given for the electromagnetic fields produced by a two-dimensional source located within a metalcased bore hole surrounded by a homogeneous rock formation. Numerical results are presented for the fields in the external region. It is shown that the combined influence of the conductivity and permeability of the steel casing will severely attenuate the fields even at frequencies as low as 100 Hz.