A method for reducing phase uncertainty for improved prospecting in frontier basins

 

Earth scientists are familiar with the Earth’s absorptive effects on seismic energy, which is often represented by the Quality Factor, Q.  Interpreters understand that attenuation causes amplitude and frequency degradation with travel time, and processors apply phase-only Q compensation in time processing to address dispersion effects.  Still, background Q, much less a spatially variant field, is notoriously difficult to characterize, and most seismic products retain amplitude and phase errors that may be unrecognized, ignored, or attributed to the black box that is seismic.  This translates into increased uncertainty in interpretation of events, relative amplitudes, AVO classification, and depthing, to name a few.

 

Well data, in particular VSP waveforms, can help to describe and correct for Q locally.  Seismic processing companies are recognizing the value of amplitude and phase Q compensation, deriving Q fields tomographically and applying the compensation through 3D prestack depth migration.  However, in frontier areas with little or no well control, the first well locations are often selected off of speculative time migrated products, and uncertainties in attributes such as phase are difficult to quantify.  A workflow is shown here that utilizes the AVO model from offset wells to better understand errors in phase for improved prospecting.