基于动态平面波的三维多尺度全波形反演方法

3D multi-scale full waveform inversion based on the dynamic plane-wave encoding method

全波形反演(FWI)是一种较为精确的速度建模方法,但是在缺少低频和背景速度场不准确的情况下,容易引起周波跳跃现象。为了快速构建三维背景速度模型,提出了一种新的平面波编码策略,即构建新的平面波形态——锥面波,通过控制射线参数,实现多尺度锥面波编码全波形反演方法(CFWI),达到反演背景速度模型的目的。通过动态锥面波编码策略,仅用少量的平面波,就可以实现背景速度场的建立,大大降低了反演的计算量。将动态锥面波反演方法应用于三维洼陷和逆冲速度模型测试,结合多震源的FWI(MFWI),对于较差的初始模型和不含低频地震数据,能够准确地反演出速度模型。

Full waveform inversion(FWI)is a relatively accurate velocity modeling method,but it can easily cause cycle jumps owing to a lack of low-frequency and inaccurate background fields.To overcome cycle skipping problem and rapidly construct 3D background velocity model,a plane-wave multi-scale FWI method was proposed.Plane waves were used for building the background field in a 3D observation system,and a new form of conical wave was constructed.By controlling the ray parameters,a multi-scale cone-wave-coded FWI(CFWI)method was implemented to achieve background velocity model inversion.Through the dynamic conical wave coding strategy,the background velocity field can be established using only a small number of plane waves,thereby greatly reducing the amount of inversion calculation.The dynamic cone wave inversion method was applied to test 3D sag and its thrust velocity model.By implementing a multi-source FWI(MFWI),the velocity model could be accurately inverted even for a poor initial model with no low-frequency seismic data.