Comparison of PP and PS reflectivities for fracture characterization

Abstract

We present a method for inversion of fracture compliance matrix components from Wide Azimuth (WAZ) noisy synthetic PS-reflection data and show quantitatively that variations of reflection amplitude with offset and azimuth (AVOA) for converted PS-waves are more informative for fracture characterization than P-waves. We consider monoclinic symmetry for fractured reservoir (parameters chosen from Woodford shale), which can be formed by two or more sets of vertical fractures embedded in a VTI background. Components of effective fracture compliance matrices for a medium with monoclinic symmetry are related to the characteristics of the fractured medium. Monte Carlo simulation results show that inversion of PS reflection data is more robust to uncertainties in our a priori knowledge (VTI parameters of unfractured rock) than PP reflection data. Also we show that while inversion of PP reflections is sensitive to contrasts in elastic properties of upper and lower media, inversion of PS reflectivities is robust with respect to such contrasts.