Research On Initial Model Construction Strategy Of Full Waveform Inversion Based On Joint Envelope And Multi-scale Methods

Full waveform inversion(FWI)makes full use of the dynamics and kinematics information in the pre-stack seismic data for inversion,and is an effective means to establish a high-resolution velocity model.However,there are many problems in the realization of FWI,such as large amount of calculation,strong nonlinearity,easy to fall into local minimum,lack of low-frequency information,and sensitive to noise.With the resolution of these difficult problems,it will be more helpful to the research and application of FWI in complex areas.Aiming at the above-mentioned problems currently faced by FWI,this paper combines envelope inversion and multi-scale FWI strategies to carry out research work,and obtains the following four research results:(1)Based on the acoustic wave equation,this paper uses the high-order staggered grid finite difference method to solve it in the time domain,and uses the CPU parallel computing strategy to accelerate the forward modeling problem,and realizes the fast calculation of the FWI.(2)Aiming at the problem of insufficient low-frequency information in the seismic data,an envelope inversion(EI)method is used to effectively extract the low-frequency components in the seismic data to restore the large-scale background structure of the model instead of onedimensional initial model,this method greatly reduce the risk of falling into a local minimum during the inversion process.(3)Based on the theoretical model data,it is verified that the EI method has the characteristics of suppressing Gaussian white noise and being insensitive to the source phase information.(4)The frequency division multi-scale FWI was realized,and the SEG/EAGE salt dome model trial calculation verified that the multi-scale inversion method can alleviate the strong nonlinearity of the FWI and reduce the phenomenon of cycle skipping.Possibility to improve the accuracy of the inversion results.