Angle-domain common-image gathers from Fresnel volume migration

Abstract

Abstract. In complex geological settings, such as in hard-rock environments, Fresnel volume migration (FVM) has been successfully applied and found to deliver superior image quality compared to conventional imaging techniques. However, previous studies on FVM have mainly focused on obtaining kinematic seismic images, and the analysis of the migrated amplitudes has not received major attention. Therefore this study presents a method for constructing angle-domain common-image gathers (ADCIGs) and common-angle stacks from FVM, which can facilitate prestack amplitude analysis from the migrated seismic data in the angle-domain. These ADCIGs were constructed inside the migration loops using phase slowness vectors derived from traveltime gradient fields. We then tested this method on synthetic and field seismic data and investigated the reliability of the output for amplitude versus angle (AVA) analysis. The test results obtained showed that the AVA responses from the common-angle stacks resemble that of the input synthetic shot gather of migration relatively well, indicating the promising feasibility of AVA analysis from common-angle stacks. When implemented on field data acquired from a hard-rock environment, the proposed method can provide common-angle stacks with a higher signal-to-noise ratio and better reflection coherency compared to the common-angle stacks from the standard Kirchhoff prestack depth migration. This study extends the implementation of FVM toward amplitude analysis, which can help improve the feasibility of hard-rock characterization.