A PRE-STACK DEPTH DIFFRACTION IMAGING WORKFLOW BASED ON ANGLE GATHERS

摘要

A new workflow is presented that can image diffracted waves for pre-stack seismic data based on angle gathers. This workflow combines the advantages of pre-stack time migration and pre-stack depth migration. For simplicity in calculations and parameter estimations, we mute the Fresnel zones related to reflections to enhance diffractions in the common angle gathers by shot-domain pre-stack time migration. A structural dip estimation scheme is provided to obtain the best Fresnel zones for accurate attenuation of reflections. Then, the demigration processing is used to remove the effect of previous pre-stack time migration on the imaged diffracted events to obtain diffracted wavefield. At last, the diffracted wavefield is imaged again by pre-stack depth migration, which adapt to imaging for complex structure. The result of my method is an effective complement to conventional interpretation workflow in detecting of small-scale geological discontinuities. Synthetic example and field data example demonstrate that my method is accurate, robust and easy to implement.