近地表复杂区早至波全波形反演建模技术与应用

为提高近地表复杂区速度建模的精度,开展了早至波全波形反演的近地表速度建模技术研究,并将其应用于陆上三维实际地震资料处理。分析了全波形反演中非线性来源,确定地震数据偏移距选取范围,讨论了观测地震数据早至波提取及其波动方程正演模拟方法,介绍了早至波全波形反演的方法原理,探讨了早至波全波形反演在实际资料应用中的关键技术流程。研究确定了早至波全波形反演的反演策略:首先利用初至走时层析方法恢复近地表模型低波数信息,然后将其作为早至波全波形反演的初始模型,利用早至波信息进行反演,恢复模型的高波数成分。研究表明,早至波全波形反演对初始模型的依赖性低于常规全波形反演。陆上三维实际地震资料测试结果表明,早至波全波形反演建模结果相对于走时层析速度模型细节更加丰富,异常体空间展布描绘更加清晰。

 The accuracy of near-surface velocity modeling affects static correction,velocity analysis and migration imaging of seismic data.The tomographic method based on high-frequency hypothetical ray theory has a “blind zone” in modeling,which can not meet the requirements of high-precision velocity modeling.The waveform inversion method based on full wavefield is limited by the quality of seismic data.In order to improve the accuracy of velocity modeling in complex near-surface area,a full-waveform inversion technique based on early arrival waves is used.The non-linear source of full waveform inversion was analyzed,and the range of offset selection was determined.The method of extracting early arrival waves from observed seismic data and wave equation forward modeling of early arrival waves was discussed.Then the theoretical method of full waveform inversion based on early arrival waves was introduced,and the key technical process used in practical data was discussed.Firstly,low-wavenumber information from the near-surface model was recovered by first arrival travel time tomography.Then the tomographic result was used as the initial model for full-waveform inversion of early arrival waves to recover the high-wave number components of the model.The results showed that full waveform inversion based on early arrival waves does not require a high level of accuracy in the initial model.Through FWI based on early arrival waves,the details of the inverted velocity model were more accurate than those of travel time tomography,and the spatial distribution of velocity anomalies was more distinct.This method has been applied to the three-dimensional seismic data of a work area,and good modeling results was achieved,demonstrating that full waveform inversion based on early arrival waves is an effective method for velocity modeling in near surface complex areas.

国家重大研发计划(2017YFB0202904)资助。