Velocity Model Refinement in Vicinity of a Borehole by Dynamically Based Traveltime Inversion (Case of Offset VSP)

We propose some development of wave equation traveltime inversion algorithm that provides the possibility to process both transmitted and reflected waves and to use Newton-like technique for macro-velocity refinement. At each iteration of nonlinear kinematical inversion we solve a linearized inverse problem using LSQR algorithm to obtain a small perturbation of a current macrovelocity model which minimizes traveltime residuals. Numerical experiments with a synthetic and real data have shown that our approach can be successfully applied for improvement of the near borehole velocity in the case of offset VSP survey. <br>