Response of tilted-coil antennas in multicylindrically layered media

We analyze the response of tilted-coil antennas in multicylindrically layered media. The loop antennas have fixed radial size of 4.5 [in]. Both the axial and azimuthal angles of the antennas can be changed. The transmitter antenna is placed at the position z=0 [in]. The first and second receiver antennas are placed at the position z=30 and 24 [in], respectively. The operating frequency is 2MHz. We study the response of this tool in multilayered formations. Both a pseudo-analytical formulation extended to multicylindrically layered medium, and a full numerical formulation based on the finite-difference time-domain (FDTD), are used to analyze this problem and for cross-validation. The FDTD method here employs a three-dimensional (3D) cylindrical grid to better conform to the logging tool geometry.