Stacking and Velocity Estimation for 3-D Surveys

The standard approach to stacking and velocity estimation for 3-D seismic reflection surveys is to organise the data by CMP bins and then apply techniques originally developed for 2-D surveys. The benefit of conventional binning is primarily in the display of the 3-D data volume.

Velocity estimation can be carried out directly with 3-D data provided the geometry of the survey is readily available. To minimise the effects of dip it is still desirable to restrict the location of the CMP’s to lie in a restricted region without the requirement of bins of fixed size. Since the stacking velocities are azimuthally dependent, the trace gathers for velocity estimation over a narrow azimuth window should be chosen for that purpose rather than be based on stacking bins. Once the elliptic variation of stacking velocity with azimuth has been estimated, the seismic traces can be simultaneously stacked and interpolated onto a regular grid. The interpolation procedure is of most significance for short reflection times. The regular array of traces is particularly beneficial for the development of 3-D self-consistent statics procedures exploiting recent developments in large scale inverse problems.