ELECTROMAGNETIC-FIELD DUE TO A LOOP ANTENNA IN A BOREHOLE

The radiation of a loop antenna embedded in a borehole with complicate d geometry is analyzed by perturbation method and an efficient fast mu ltiple-integration technique. The perturbation method is not used dire ctly because there is a drill-stem whose conductivity and magnetic per meability are very large in the borehole, The prolate ellipsoid equiva lence of the metal drill-rod is made, then the drill-rod may be remove d and the perturbation method is valid, Some numerical results indicat e that the approach is efficient and stable at low frequencies.