Observations of Seismic Attenuation as Loss of Energy in the Overburden and as a Fracture Indicator

We present an illustration of the two aspects of understanding seismic attenuation: as a means of correcting seismic data to enhance resolution of standard imaging techniques, and as a potentially important quantity which may provide information on fluids and fractures. We study two different datasets for this purpose. In the first case, we show a clear example of anisotropic attenuation in the overburden using a walkaround VSP gather. We suggest that this effect may be important for processing and interpretation of multi-azimuth reflection data. In the second case, we estimate the attenuation between two wells as a function of depth in a crosswell shotgather. The attenuation appears to be sensitive to the density of open fractures, with high attenuation in high fracture density areas. We show that the fracture density and permeability are statistically related to the observed attenuation and these parameters can reproduce the measured Q values with a rock physics model.