Corrections for polarization distortion in reflected shear-waves and possible extensions to the Alford Rotation at non-normal incidence angles and applications

Abstract

Onshore resource shale production (gas and liquids) is growing rapidly and may necessitate the use of seismic shear wave data for full characterization of shale reservoir properties prior to drilling and completion. This includes descriptions of anisotropy for characterization of fractures (HTI) as well as the internal nature of the shales (VTI and Vp/Vs). The objective of this study is two parts. The first is to document the distortion in polarization of seismic shear waves upon reflection. Second we address a correction, based on an understanding of shear amplitude versus incidence angle behavior that corrects for the distortion at offset angles. This includes demonstration of the efficacy of the proposed correction by applying it to 9C shear source data from the Black-Bear field in Oklahoma. This correction should result in a minimized distorted amplitude response that arises from polarization distortion upon reflection. The polarization distortion correction may potentially be used in an extension to the Alford's rotation at non-normal incidence angles. Hence, expanding applications to 3D data with distorted amplitudes that may be corrected to identify HTI anisotropy not observed in polarization distortion reflections