Liang C. Shen
University of Houston
ABSTRACT
The amplitude-based log and the phase-based log of a measurement-while-drilling (MWD) resistivity sensor is often separated in a formation and the separation is the direct consequence of the method used to convert phase and amplitude data into resistivity logs. Examples show that the two resistivities separate even in some homogeneous media. The depth of investigation based on the so-called integrated pseudo geometrical factor may not be a good indicator for predicting whether or not the phase-based log is deeper looking than the amplitude-based log. It is highly desirable to use computer simulation, to infer from the MWD logs the resistivity of the formation and the invasion profile.