Review of 3D EM Modeling and Interpretation Methods for Triaxial Induction and Propagation Resistivity Well Logging Tools

The 3D electromagnetic (EM) modeling and inversion techniques for the geological formation evaluation have been experiencing signiflcant progress since the early 90s. There are three main 3D EM numerical techniques: flnite-difierence (FD), flnite element (FE), and integral equation (IE). They have been used for simulating arbitrary 3D media as well as for development of 3D inversion-based interpretation of well log data acquired by the conventional and new-generation logging tools. We present a brief review of these three techniques as to their ability to simulate and interpret the new-generation of triaxial tensor wireline and logging-while- drilling (LWD) measurements. The new EM tools provide full triaxial tensor measurement, in addition to the conventional axial measurement, when the formation is excited by an axial z- directed magnetic dipole transmitter, and the response of axial receivers is analyzed. Due to full 3D sensitivities, the new tools allow signiflcantly enhanced formation resistivity interpretation. We present synthetic logs for four difierent new-generation tools: both triaxial induction and directional propagation resistivity LWD tools. We also consider new features in the new tool responses and discuss various post-acquisition processing techniques. These approaches allow to better visualize tool responses and enable e-cient application of fast stable inversion schemes for resistivity interpretation.