Abstract

Recent observations from several walkaround, walkaway, and 3D VSPs from various parts of the world have shown that anisotropy symmetry directions (or fracture orientations) estimated from traveltime or velocity anisotropy do not necessarily agree with symmetry directions from amplitude or attenuation analysis. We have also consistently found that attenuation anisotropy in reservoir intervals is generally stronger than in overburdens. We argue in this article that, instead of reconciling the differences between various attributes, we should try to understand the mechanisms and use the difference in velocity and attenuation anisotropy which may contain additional information about subsurface fracture systems.

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