基于应变率的分布式光纤声波传感全波形反演研究

Study of distributed acoustic sensing data waveform inversion based on strain rate

分布式光纤声波传感系统(Distributed Acoustic Sensing,DAS)是近年来迅速发展的新型地震数据采集系统.与传统地震检波器相比,DAS具有耐受恶劣环境,易实现大区域高密度观测等优点.传统地震检波器测量质点速度,而DAS接收沿光纤的轴向应变率(或应变)信号,传统基于速度—应力场弹性波方程全波形反演无法直接用于DAS数据反演.在前人DAS数据全波形反演研究中,将DAS数据转换为沿光纤的质点速度,但会放大低波数噪声,在低信噪比条件下影响反演精度.本文提出了直接基于应变率数据的DAS信号全波形反演方法.首先推导实现了直接基于应变率参数的DAS数据全波形反演理论.其次通过典型模型测试和DAS实测数据验证了直接基于应变率的全波形反演方法在DAS数据速度反演中的可行性和有效性.

Distributed Acoustic Sensing(DAS)is a new seismic observation system that has developed rapidly in recent years.Compared with traditional geophones,DAS has the advantages of a wide application range,high resolution,etc.Traditional geophones record particle velocity,while DAS receives axial strain rate signals along with the fiber.So,the conventional full-waveform inversion(FWI)based on the velocity-stress wave equation cannot be directly used for the DAS strain rate data inversion.The previous FWI DAS method converts the strain rate into particle velocity,amplifying low wave number noise and affecting the inversion accuracy under a low signal-to-noise ratio(SNR).This paper proposed the DAS-FWI method directly based on strain rate data.Firstly,we derive the elastic wave full-waveform inversion theory based on strain rate parameters.Then,the typical synthetic model and DAS field data tests demonstrate the feasibility and effectiveness of the proposed strain rate DAS FWI method in velocity tomogram.