基于散射理论面向储层的叠前地震波形反演理论与方法

Pre-stack seismic inversion is a useful hydro-carbon detection geophysical technology. However, for the practical application, conventional inversion methods, such as AVO inversion based on the Zoeppritz equation and full waveform inversion, have encountered difficulties and choke point. These methods cannot meet the needs of fine description of reservoir and the development of unconventional reservoir nowadays. In this project, for solving the reservoir-oriented seismic inversion problem, we solve the stress-velocity formulation of elastic scattering problems. And we will develop a more stable and efficient approach to the numerical simulation of elastic wave propagation that is based on the integral equation formulation. For the process of the inversion, the forward operator will be the integral representation of the elastic wave equation mentioned above. Besides, the input data to the inversion should be the full wave field information, which is accounted for the all internal multiple scattering and mode-conversions, as well as travel time differences between the real medium and the background medium of the target interval. Based on the regularization theory and the Bayesian framework, the reservoir-oriented elastic scattering theory based pre-stack seismic waveform inversion scheme will be developed. By contrast, the new method not only attempts to overcome the defect that the pre-stack AVO inversion method based on the Zoeppritz equation uses the linearized reflection coefficients, but also avoids the expensive computation of the full waveform inversion (FWI). There are many benefits for the further study of this project. Above all, it is of great significance to develop the pre-stack seismic inversion theory. And it has important practical application value to improve the seismic technology progress, as well as to promote the development of the unconventional hydro-carbon efficiency and to reduce the risk of drilling.

目前，基于地震波传播近似理论或全波场理论的油气地球物理技术在面向储层的实际应用中遇到了困难与瓶颈，不能满足油气藏精细描述和非常规油气开发的需求。项目针对面向储层的地震反演问题，将弹性波动方程的求解转化为弹性散射问题求解，发展基于散射波场的弹性波动方程积分法，研究求解弹性散射波场稳定高效的计算方法。以基于散射波场弹性波动方程积分法求解为正演算子，利用面向储层同时考虑层间多次、透射损失等在内的全波场信息，结合正则化思想以及贝叶斯反演理论框架，建立基于散射理论面向储层的叠前地震波形反演理论与方法。试图解决传统基于Zoeppritz方程的AVO反演理论不能考虑层间多次波、转换波、球面扩散和透射损失等波传播效应问题，也避开全波形反演巨大计算量的问题。项目研究对于丰富和发展叠前地震反演理论具有重要意义，对促进地震技术进步，推动老油田挖潜、提高非常规油气开发效益、降低钻探风险等具有重要的实际应用价值。

项目开展了弹性波动方程散射波场积分法快速求解方法、基于散射波场积分法方程求解的非线性反演框架构建、基于散射理论面向储层的叠前地震波形反演框架下正则化参数分析、基于贝叶斯反演理论框架约束的散射理论面向储层的叠前地震波形非线性反演方法探索等研究，提出了弹性波动方程散射波场积分法快速求解方法和基于散射理论面向储层的叠前地震波形反演理论，实现了相关算法。对比本项目研究方法与其它方法的优缺点，确定方法理论分析的精确性与实际应用的可行性。在此理论研究基础上，将研究成果与实际密切结合，建立了对应的实际处理流程，完成了基于散射理论面向储层的叠前地震波形反演方法的实际数据应用试验，充分利用本项目研究算法和成果改善了正演算子精度和提高了反演效率。通过本项目研究，形成了基于散射理论面向储层的叠前地震波形反演理论与方法，提高了实际资料的计算效率与反演结果质量。按照研究计划，完成了项目研究内容，达到了预期目标。