Effects of geological structure and geophone field configuration on seismic velocity accuracies

Abstract

In the seismic reflection method the determination of vertical signal velocities is of basic importance, but timing perturbations which result from raypath distortion may cause discrepancies in the process of calculating true velocities from the velocities obtained by a stacking process. In particular, if different configurations of geophones ('field configurations') are employed over an area, the 'stacking velocities' obtained can vary greatly with different shot-to-receiver distances, even though a constant separation ('spread length') of the geophones is maintained. In this paper the modelling of raypaths in some simple geological sections shows that the combined effects of both velocity errors and timing errors may be so significant as to obscure the resolution needed in the method for the detection of subtle hydrocarbon traps.