Electromagnetic Fields Due to a Loop Current in a Cased Borehole Surrounded by Uniform Whole Space

Precise evaluation of electromagnetic (EM) response in steel-cased borehole is an essential first step towards developing techniques for casing parameter evaluation, which would ultimately help evaluating the formation response. In this report we demonstrate a numerical scheme for accurately computing EM responses in cased borehole environment. For improved numerical accuracy we use explicit representations of the electromagnetic spectra inside the borehole, in the casing, and in the formation. Instead of conventional Hankel transform, FFT is used to improve the numerical accuracy. The FFT approach allows us to compute fields at positions very close to the source loop, including the center of the transmitter loop