多次波逆时偏移与常规逆时偏移对比分析

Comparison and analysis of multiple reverse-time migration and conventional reverse-time migration

在常规逆时偏移处理流程中,将包含一次波和多次波的地震记录代替脉冲震源子渡沿时间延拓到各个深度层,将地表多次波记录代替一次波地震记录沿时间逆时延拓到相同深度层,然后选取合适的成像条件实现基于逆时偏移的多次波成像,即为多次渡逆时偏移.本文首先详细分析了常规逆时偏移对多次波的成像机制,简要阐述了多次波逆时偏移的原理,在此基础上对多次波逆时偏移和常规逆时偏移的成像效果进行了模型试算,证实了逆时偏移对多次波进行成像的可行性,只有正向外推的震源渡场和逆时外推的预测多次波波场中成对的波场能量才能互相关产生真正的成像值,且多次波逆时偏移可以获取比常规逆时偏移更为广阔的成像和照明范围,对深部构造有更好的照明.

In the process of conventional reverse-time migration,the numerical impulsive source is replaced with the recorded data including primaries and multiples on the surface and are extrapolated forward in time to each depth level,while the recorded primary reflections are replaced with multiples and are extrapolated backward in time to the same depth levels,then we select the appropriate imaging condition to realize the multiples imaging based on RTM The above process is Multiple RTM.In this paper,we analyzes the conventional RTM＇s imaging capability of multiples and then discuss the theory of Multiple RTM.Numerical examples show that the multiples can be imaged by RTM Only the pairs of the wave field energy between the extrapolated forward source wavefield and the extrapolated backward predicted multiples can be crosscorrelated to produce the real imaging values.Multiple RTM can provide more vast and precise underground lighting and imaging for the deeper and more complex seismic exploration.