叠前逆时偏移实用化方法研究

Research of prestack reverse time migration

基于双程波动方程的叠前逆时偏移技术是解决复杂构造成像难题的强有力手段.本文首先对该技术的基本原理和实现方法进行简要介绍,该技术主要包括震源波场与检波波场构建、对构建的源、检波场应用互相关成像条件以及成像过程中或成像后低波数噪声压制三个主要环节.在此基础上对其实用化过程中涉及的高性能计算策略、低存储方案和高效低波数噪声压制方法等关键环节所需考虑的因素进行分析并给出相应的解决方案,从而给出了一套存储消耗较低且计算效率较高的逆时偏移实现流程.然后以Sigsbee2A模型和深水盐丘数据为例,与工业上标准的克希霍夫叠前深度偏移方法成像结果进行对比从而验证方法的正确性及对复杂构造的成像优势.最后结合理论分析与实际测试结果对该技术的特点和发展方向进行探讨与总结.

Reverse Time Migration(RTM), based on the two-way wave equation, is considered as a powerful tool to solve the imaging difficulty of complex subsurface structures. In this paper, we first give a brief introduction and analysis of the basic principles and workflows of RTM. For this method, it mainly consists of three steps: reconstruction of the source and receiver wavefields, crosscorrelation of the time consistent source and receiver wavefields and suppression of the low wavenumber noise. At the same time, some key aspects of industrial-scale development and application, such as high-performance computational framework, efficient wavefield reconstruction strategies and low wavenumber noise suppression methods, are also discussed in detail. So a relatively low storage cost and high computational efficiency workflow of RTM is proposed. Then the Sigsbee2 A model and a field data example which both contain a salt body are used to examine its validity and imaging capability of complex subsurface structures compared with the results of standard Kirchhoff prestack depth migration. Finally, based on the above theoretical analysis and practical examples, a discussion about its characteristics and further development is provided.