逆时偏移技术发展现状与趋势

逆时偏移比单程波波动方程偏移和克希霍夫积分偏移更适于复杂构造成像。基于双程波波动方程进行波场逆时外推,并应用成像条件提取成像值,可以得到逆时偏移数据体。实例分析表明,逆时偏移对盐体侧翼及盐下构造的成像效果要优于单程波波动方程偏移。然而,由于采用有限差分算法以及需要保存大量的震源波场数据,因而逆时偏移的计算成本很高,使其无法适应大数据量的地震数据处理;而由互相关成像条件引入的低频噪声也是困扰逆时偏移实用化的一个问题。在总结和分析逆时偏移技术的进展以及国外地球物理公司关于逆时偏移技术发展策略的基础上,结合研究现状,阐明了逆时偏移未来的发展趋势和研究重点。分析认为,进一步提高逆时偏移的计算效率仍然是未来几年逆时偏移技术发展的重要方向,弹性波逆时偏移和各向异性逆时偏移将会越来越受到重视。

Development status and trend of reverse time migration

Reverse time migration(RTM)is more applicable for the imaging of complex structures than one-way wave-equation migration and Kirchhoff integral migration.Based on two-way wave-equation,extrapolating wavefields in reverse time domain and applying imaging conditions to extract the imaging values,we can gain reverse time migration data volume.The imaging results of salt flanks and subsalt structures by applying reverse imaging are better than one-way wave-equation migration.However,since reverse time imaging adopts finite difference algorithm and needs to store large amount of source wavefield data,its computation cost is high,which causes it not suitable for processing huge amount of seismic data.In addition,the low-frequency noise caused by crosscorrelation imaging conditions also puzzles the practicality of reverse time migration.Based on summarizing and analyzing the technical progress of reverse time migration techniques as well as its development strategies of foreign geophysical companies,combining with development status,we analyzed the future development trend and research focus of reverse time migration.We think that further improving the computation efficiency is still an important development direction of reverse time migration in future few years,elastic wave reverse time migration and anisotropic reverse time migration will be paid more attention to.