Target Oriented Velocity Analysis with Marchenko Redatumed Data

Abstract

Summary Marchenko redatuming allows us to remove the effect of a complex overburden from seismic surface data so that we obtain redatumed reflection responses for virtual sources and receivers at an arbitrary new datum level within the subsurface. We propose a method to perform target oriented velocity analysis using such redatumed data. We apply an iterative Marchenko scheme to a horizontally layered medium and we use the redatumed data to create angle-domain common image gathers (ADCIG’s) at specific offset positions. The curvature of reflections in the ADCIG’s is directly related to incorrect velocities used for both redatuming and imaging. We use a synthetic example to demonstrate that we can correctly determine velocity errors using a semblance analysis applied to an ADCIG. Combining the results of the semblance analysis for the different reflections present in one ADCIG, we are able to separate the velocity error inherent to the portion of the velocity model used for redatuming from the one used for imaging. Therefore, using Marchenko redatumed data, our approach allows us to determine velocity errors in a target zone of a layered medium, even if we use incorrect velocities for redatuming.