AVO and Anisotropy
The AVO studies that we discussed in the preceding chapters assume that subsurface rock formations are isotropic. Often that assumption is not strictly true, because subsurface formations can exhibit various kinds of anisotropy. In such cases, serious errors can creep into AVO analysis and lead to erroneous interpretations. On the other hand, anisotropic behavior can be used beneficially to characterize fractured reservoirs. Thus, it is important to study the different types of anisotropy encountered in subsurface formations, along with their effect on seismic data, and then to determine their ultimate effect on AVO analysis. We will explore all of these considerations in this chapter.