Research And Application Of Acoustic Wave Full Waveform Inversion Based On Staggered-Grid Finite Differences

Full waveform inversion can accurately estimate the high-resolution seismic parameter model by data fitting and solving the optimization problem,which is also one of the hotspots in geophysical field.Although the theoretical framework of full waveform inversion has a great development,there are still many problems in field data application.Such as the huge calculation and computing time of full waveform inversion are important reasons for the large-scale application of batch data.In this paper,the wave equation numerical simulation method is used for forward and inversion research.Firstly,the high-order staggered grid finite difference of the first-order stress-velocity acoustic wave equation is derived,the influence of CPML boundary conditions of the forward modeling and the dispersion and stability conditions of staggered grid finite difference are discussed in detail.In order to improve the computational efficiency of wave equation forward modeling,CUDA parallel computing platform is used to realize the parallel algorithms of acoustic equation forward simulation with second-order in time and eighth-order in space.Then,according to the basic principle of inversion,the calculation of gradient of misfit function which based on adjoint method,the estimation of optimum step and multi-scale inversion strategy are deeply introduced.The wavefield reconstruction strategy is adopted to reduce the memory demand in the inversion process.This paper uses the L-BFGS method to solve the optimization problem of nonlinearity.Finally,using the theoretical model and actual data to test and analyze the FWI method of this paper.In the theoretical model test,this paper focuses on the exploration problems with different surveys,and the inversion accuracy in each case is quantitatively analyzed through the comparison of velocity curves and the error of misfit function.Using the research results of this paper,the actual data of Walkaway VSP are tested,the velocity distribution characteristics underground are accurately estimated and the effectiveness and reliability of this method is verified.