3D Regional Velocity Modeling

Building a realistic and accurate regional velocity model at the scale of a basin is only possible by integrating seismic velocity data. Traditionally the integration of the seismic velocity data into a velocity model is made by a layer cake approach. This is a quite incomplete integration as the approach stacks, layer by layer, the vertical structuration of the seismic velocity data. At the scale of a basin, a fully 3D integration of the seismic velocity data sets, coupled with previous qualification and merge steps, leads to the generation of a 3D continuous velocity model. That fully 3D approach, possible thanks to advanced geostatistical techniques, has been applied on several basins. The observed depth uncertainty attached to the velocity models is on average about +/−70m (error far from the wells, expressed in terms of 2 × standard deviation of the errors distribution).