Fracture detection using P‐wave AVO

A 3-D modeling program for general anisotropy was used to obtain the reflection coefficients of the P-wave reflected from two anisotropic, vertically fractured media beneath an isotropic medium. Two lines were recorded, perpendicular and parallel to the fractures. Although the AVO response of a media containing gas-filled fractures increases with offset when the recorded line was parallel to the fractures, we observed a decreasing AVO response when the offset orientation was perpendicular to the direction of the fractures. Media containing fractures filled with water present no such differences; the AVO response increases with offset, perpendicular and parallel to the fractures. The results were compared to a generalized Zoeppritz solution for reflections from a layer with vertical fractures. The case study suggests that AVO response for different source-receiver azimuths may contain information about the internal structure of the subsurface.