In order to compare the results of sonic-log measurements and of vertical seismic profiling (VSP), the sonic-log velocities are used to estimate the corresponding travel time in the geological structure, which is then compared with the VSP travel time.
In this paper we show how to calculate the sonic-log travel time in the geological structure from the sonic-log velocities while taking into account the effects of the non-vertical propagation of seismic waves due to the source offset and due to the heterogeneous velocity in the structure, together with the effects of well trajectory differing from strictly vertical. We also estimate the errors due to the commonly used assumption of vertical propagation.
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