The Anisotropic Characteristics of Mesoscale Fractures and Applications in Wide Azimuth 3D P-wave Seismic Data

In order to predict different scales of fractures, we analyze differences in P-wave anisotropic attributes caused by different scales of fractures through numerical and rock physics modelling based on an equivalent medium theory. Two scales, meso (1m) and micro (0.001m), are considered during the modeling. Within the limits of the equivalent medium theory, the effects of fracture scale on velocity anisotropy are small, and hence the velocity anisotropy attribute is not senstive to fracture scale. However, the root-mean-squared amplitude attributes show significant changes with offset but have no obvious differences between fracture scales. This indifference to different fracture scales was also present in the anisotropic AVO gradient attributes. However, attenuation is very sensitive to the fracture scale.

Attenuation induced by mesoscale fractures is large. In contrast, attenuation induced by microscale fractures is very small and can be neglected, indicating that attenuation anisotropy attributes can be used to detect mesoscale fractures. These findings are applied to a wide azimuth 3D P-wave seismic dataset to illustrate their applications for detecting meso-scale fractures.