基于反射能量约束全波形反演初始速度场建立研究

Establishment of initial velocity field for full waveform inversion based on reflective energy constraints

全波形反演作为地震勘探中提取实际地下介质弹性参数的高端技术,一直是研究的热点和难点.它以综合利用地震数据中的全部信息(振幅和相位等)来开展优化反演方法,一方面现有的全波形反演方法主要以局部最优化算法为主,另一方面采集观测系统局限性和地震数据的带通特征,使其具有较强的非线性,从而导致其对初始模型存在较强的依赖性.本文提出了一种利用反射能量约束全波形反演方法,目的是为常规全波形反演提供相对可靠的初始模型,首先利用反射能量算子给出了其散射波动方程具体表达式,并利用两个不同的散射模型说明了反射能量算子可有效提取反射信息的能力.在此基础上提出了基于反射能量约束全波形反演方法的梯度算子并建立其反演流程,最后利用简单的凹陷和复杂的推覆体模型验证了本文提出的基于反射能量约束的全波反演方法可有效提供精度较高的初始速度信息.

Full waveform inversion,as an advancing theory for extracting elastic parameters of real underground media in seismic exploration,has always been a hot and difficult research topic.On the one hand,due to the limitation of computation capacity,the existing method of full-waveform inversion is mainly based on local optimization algorithm.On the other hand,the limitation of the survey design and frequency range of seismic data make it strong nonlinearity,which leads to the success of inversion depends on the accuracy of initial model.In this paper,a full-waveform inversion method using reflection energy constraints is proposed.The purpose is to provide a relatively reliable initial model for conventional fullwaveform inversion.Firstly,the scattering wave equation is expressed by using reflection ability operator.Two different scattering models are used to illustrate the ability of reflection energy operator to extract reflection information effectively.On this basis,a gradient operator based on reflectivity constrained full-wave inversion method is proposed and its inversion process is established.Finally,the simple depression medal and the complex nappe model are used to verify that the proposed full-wave inversion method based on reflection energy constraints can effectively provide high accuracy initial velocity information.