The introduction of well data in the velocity model demands some extra care because seismic data provide a relatively high horizontal resolution while well data provide a very narrow vertical resolution but a poor horizontal resolution. Well velocities are direct rock properties, estimated directly from the earth, while seismic velocities are indirect rock properties estimated from traveltimes. If the combination of seismic velocities and well velocities were possible, migration results would be favorably improved.
The problem is how to manage both velocities to get
better seismic images.
Well velocities may be interpolated to obtain a horizontal velocity model.
This velocity model can be correlated with the velocity
model from seismic data, resulting in a new
velocity model from both kinds of information.
The interpolation problem, may be solved using geostatistics.
As a conclusive example, Lee and Xu (2000) show how geostatistics
helped to improve the imaging of a geopressure zone in the Gulf of
Mexico. Other interpolation techniques Fomel (1997) can
be implemented in order to obtain a satisfactory 
.Steering filters prove effective in interpolating velocities
obtaining a horizontal velocity model from well data
Clapp et al. (1997, 1998); Clapp and Biondi (1998),
but it will be necessary to regularize well velocities in order
to allow a satisfying the correlation between the velocity model from seismic
and from well to produce good results.
In the next section, I am going to discuss a method to obtain
interval velocities from RMS velocities.