Abstract: Directional drilling techniques allow for the drilling of boreholes within the earth along any three dimensional path. This invention provides a method for determining the path a wellbore needs to take in order to stay within a defined three dimensional target. This is done by using the petrophysical and spacial information received from the portion of the wellbore as drilled. First, a three dimensional model of the target is constructed using seismic data. Then, the seismic data is used to create a depth model which is continually refined during the drilling operation. This will provide the needed information to steer the wellbore to any point within a three dimensional representation of the real target.