强非均质介质中参数长波长分量反演方法研究

Full waveform inversion can provide velocity models with high accuracy and high resolution for migration, and it is very useful for the exploration and development of subtle hydrocarbon reservoir in complex areas. However the highly nonlinear property makes full waveform inversion depend strongly on the initial model，which means that long wavelength component must be contained in the initial model. Conventional methods cannot effectively retrieve the long wavelength structures and will converge to the local minima, especially for strong heterogeneous complex models, because there is always no low frequency information in seismic data. This project focuses on this issue. We would start from the theory for the analytic signal and extract the instantaneous amplitude (data envelope) and the instantaneous phase information. Considering the phase wrapping problem in numerical calculation, an efficient phase unwrapping method based on the exponential instantaneous phase would be proposed. By combining the properties of data envelope and the instantaneous phase information together, the joint objective function using the scattering angle as constraint would be constructed. Furthermore, a hierarchical inversion strategy would be proposed based on the joint objective function to improve the inversion. If this project runs smoothly, the results would provide fine initial models for the inversion of strong heterogeneous complex geologic models, which would promote the development of full waveform inversion and support the exploration and development of complex oil-gas reservoir strongly.

全波形反演可以为偏移成像提供高精度、高分辨率的速度模型，对复杂地区油气藏的勘探开发具有重要意义。然而全波形反演的高度非线性特性导致其对初始模型依赖性很强，要求初始模型包含介质参数的长波长分量。由于地震数据中往往缺乏低频信息，常规全波形反演方法不能有效获得介质参数的长波长分量，容易陷入局部极值，尤其对于强非均质性复杂介质，该问题更为突出。本项目拟针对此问题展开研究，从解析信号理论出发，分别提取地震信号的瞬时振幅(包络)与瞬时相位信息；考虑到数值计算中的相位缠绕问题，提出利用指数相位进行快速相位解缠绕的方法。结合包络与瞬时相位各自的特点，以散射角为约束条件，提出融合包络与瞬时相位信息的联合目标函数；在此基础上，提出有效的分级反演策略，以提高反演效果。本项目研究成果能够为强非均质性复杂地质模型的全波形反演提供良好的初始速度模型，推动全波形反演的发展，为复杂油气藏精细勘探开发提供有力支撑。

全波形反演可以为偏移成像提供高精度、高分辨率的速度模型，对复杂地区油气藏的勘探开发具有重要意义。然而全波形反演的高度非线性特性导致其对初始模型依赖性很强，要求初始模型包含介质参数的长波长分量。由于地震数据中往往缺乏低频信息，常规全波形反演方法不能有效获得介质参数的长波长分量，容易陷入局部极值，尤其对于强非均质性复杂介质，该问题更为突出。本项目针对此问题展开研究，首先从解析信号理论出发，提取地震信号的瞬时振幅与瞬时相位信息；考虑到数值计算中的相位缠绕问题，首先提出了利用指数相位进行快速相位解缠绕的方法，并在此基础上研究了基于瞬时相位信息的时间域全波形反演方法。以散射角为约束条件，研究了基于角度分解的全波形反演方法，并分别应用于时间域和频率域、声波和弹性波、单参数和多参数的全波形反演。本项目研究成果能够为强非均质性复杂地质模型的全波形反演提供良好的初始速度模型，推动全波形反演的发展，为复杂油气藏精细勘探开发提供有力支撑。项目研究过程中，已发表期刊论文6篇（其中SCI论文4篇），国际会议论文3篇，授权国家发明专利1项，培养研究生8人（其中4人已毕业）。按照项目研究计划，完成了项目预期研究内容，获得了比较好的预期效果，达到甚至超过了预期的研究目标。