Separation of azimuthal effects for new-generation resistivity logging tools - Part I

A symmetrization approach used in new-generation logging-while-drilling (LWD) resistivity tools separates the dipping anisotropy and dipping boundary effects. It deals with couplings between axial transmitters and tilted or transverse receivers. I have investigated the performance of two symmetrization schemes in full 3D scenarios for LWD and rigorously extended them to triaxial induction logging, including couplings between transverse transmitters and transverse receivers. Thus, I apply similar principles of data processing to new-generation wireline and LWD tools. The method enables separation of the formation response from the borehole eccentricity effect, which cannot be ignored for triaxial induction. The technique can accelerate and improve existing methods of formation interpretation by directly determining bed boundary positions, formation anisotropy azimuth, and tool eccentricity direction and by improving visual interpretation of raw tool data. The second objective of my investigation was a brief review of previously published work on a 3D finite-difference (FD) modeling approach, its latest development and its ability to simulate responses of new-generation resistivity tools in general 3D formations. This approach, based on the Lebedev staggered FD grid, handles arbitrary resistivity anisotropy effectively. Its high efficiency encourages its routine use for modeling. In addition, the method enables simultaneous multispacing and multifrequency computing at no cost. It makes the detailed investigation and further development of the separation technique possible.