Shear‐wave imaging using cross‐dipole acoustic logging tool

Abstract

The shear waves from a four‐component cross‐dipole acoustic tool were analyzed to provide an important method for the single‐well acoustic imaging application. We analyzed the effects of wave radiation, reflection, and borehole acoustic response on the shear‐wave reflection measurements. In particular, we studied shear‐wave radiation from a dipole source and the wave's reflection from a formation reflector, showing that the shear waves generated by a dipole source in borehole have a wide radiation pattern. This allows for imaging reflectors at various dip angles crossing the borehole. More importantly, the azimuthal variation of the shear waves, in connection with the multi‐component nature of a cross‐dipole tool, can be used to determine the strike azimuth of the reflector. The analysis results establish a theoretical foundation for the borehole shear‐wave imaging application. The theoretical results are utilized to formulate an inversion procedure for field data processing. The field data application not only validates the theoretical results but also demonstrates advantages of shear‐wave imaging.