Evaluation Of Prediction Ahead Of The Bit By Inversion Of Vsp Data

One of the applications of VSP surveys is to predict acoustic impedance<br>variations in a well ahead of the bit. The up going wave traces<br>obtained from the VSP processing are inverted to produce a pseudo-<br>acoustic impedance log for the sediments below T.D. This type of<br>inversion is expected to be more precise than the inversion of surface<br>seismic data for two reasons: a) An accurate estimation of the seismic<br>wavelet is obtained from the deconvolved down going waves. b) The<br>bandwidth of the VSP traces is wider than that of surface seismic data<br>and the signal/noise ratio is generally better in VSP data than in<br>surface seismic data.