Single-well acoustic imaging in anisotropic formations

Abstract

The effect of formation anisotropy on single-well acoustic imaging was analyzed to provide a simple and effective correction method for the imaging application. We used analytical and synthetic modeling to analyze acoustic reflection moveout in a transversely isotropic (TI) formation for borehole configuration. Far-borehole reflections from a bed generally have small reflection angles to the bed. Thus the reflection moveout away from the borehole is controlled largely by the velocity along the TI-symmetry axis. Consequently, reflection imaging using measured velocity along the borehole can cause errors in the imaged reflector position. By correcting the anisotropy effect in the velocity, reflectors can be imaged correctly. A simple correction is to use the velocity along the TI-symmetry axis, which effectively maps the bed reflector to its correct position. Application of the correction method to synthetic and field-data examples demonstrate the anisotropy effect on reflector imaging and the effectiveness of the method.