Electromagnetic field due to a loop antenna in a borehole

The radiation of a loop antenna embedded in a borehole with complicated geometry is analyzed by perturbation method and an efficient fast multiple-integration technique. The perturbation method is not used directly because there is a drill-stem whose conductivity and magnetic permeability are very large in the borehole. The prolate ellipsoid equivalence of the metal drill-rod is made, then the drill-rod may be removed and the perturbation method is valid. Some numerical results indicate that the approach is efficient and stable at low frequencies