Angle Domain Common Image Gathers Based On Reverse-time Migration

In recent years,reverse-time migration(RTM)has raised up scholars more interest,because the difficult of imaging the complicated subsurface targets has increased.Based on the full wave equation,the RTM can deal with wave propagation in all direction without angle limitation.It can handle not only multi-arrivals,but also overturned reflections.RTM is one of the most accurate imaging method.Common imaging gathers(CIG)is the main input data of velocity analysis and AVO analysis?AVA analysis.Compared with other CIG,Angle domain common imaging gathers(ADCIGs)can form high coherence flat events even for complicated structures and greatly reduce low-frequence noise.Poynting vector method is a fast and efficient method to construct ADCIGs,the advantage of this method is not need too many extra storage,only need a tiny mount calculation.The ADCIGs also has higher resolution than other methods.This paper first introduces the basic principle of reverse-time migration,including the reverse-time migration wave-field forward modeling and reverse continuation algorithm.Stability conditions are given,choose the appropriate source function,and take the appropriate PML boundary condition.The reason why low-frequency noise exists in reverse-time migration was analyzed,then different imaging conditions are introduced to suppress the low frequency noise in reverse-time migration rseult.Then the principle and implementation process of the Poynting vector method are introduced.Through the model trial,the selection of Angle decide the resolution and the S/N ratio of ADCIGs,triangle filter is used to smooth ADCIGs to get higher S/N ratio.Finally through complex Marmousi model and Sigsbee2 A model is verified the correctness of the Poynting vector method to extract the ADCIGs.