A ROBUST METHOD OF EXTRACTING ANGLE-DOMAIN COMMON-IMAGE GATHERS FROM SHOT-PROFILE WAVE EQUATION MIGRATION

摘要

Shot-profile pre-stack depth migration is quite attractive for sparse-shot wide-azimuth geometries. Meanwhile, angle-domain common-image gathers (ADCIGs) have become an essential tool in seismic processing. After revisiting the popular schemes of extracting ADCIGs, we present a robust method to estimate the incident-angle field and extract ADCIGs from shot-profile wave equation migration. The cosines of the incident-angle can be estimated from the ratios between the square roots of the angle-weighted image gathers' Laplacian operators and the amplitude values from the conventional common-image gathers. The angle-weighted image gathers can be extracted by multiplying an extra imaging weight including local propagation velocity and angular frequency in conventional shot-profile wave-equation migration process, while the conventional common-image gathers are obtained using the cross-correlation imaging condition. A stable division at selected wave crests with large amplitude ensures the stability and avoids noise interference. Finally, we separate the shot-domain common-image gathers (SDCIGs) into different angle bins using incident-angle field to extract ADCIGs. Numerical examples demonstrate that the method is stable and memory-efficient and independent of structural dips.