Research On Full Waveform Inversion Method Of Two-dimensional Acoustic Wave Equation

Full Waveform Inversion(FWI)is characterized by high accuracy and high resolution,and the results of FWI can provide important support for exploration issues such as lithologic judgment and reservoir identification.This thesis presents a new full waveform inversion method for two-dimensional time-domain acoustic wave equations.We study the full waveform inversion method from three aspects:forward simulation method,iterative direction and search step length:(1)We use the ON ADM method to perform forward modeling of the layered model and the Marmousi model,and the surface seismic records of the simulation results show that the direct and reflected waves of the two models are obvious,the entire seismic record is clear and no visible numerical dispersion.It can be seen that the ONADM method can be used for full waveform inversion;(2)The CG-DESCENT method is the selection method of the iteration direction;(3)The improved back-off method is the step length search method.On this basis,this thesis proposes a new full waveform inversion method-CDIB full waveform inversion method.The CDIB full waveform inversion method is used in inversion test for the layered model and the Marnousi model.From the inversion results of the layered model,it can be seen that the CDIB full waveform inversion method can be solved 50 times to obtain better inversion results under the premise of satisfying the convergence condition.In the process of inversion of Marmousi model,L-BFGS algorithm and Wolfe-Powell inexact one-dimensional search method(abbreviated as LBWP full waveform inversion method)are also used in inversion test.Comparing the inversion results of the two methods,we discover:(1)while satisfying the convergence condition,the CDIB full waveform inversion method is iterated 68 times,and the LBWP full waveform inversion method is iterated 96 times,and the required calculation time of LBWP full waveform inversion method is 4.61 times that of the CDIB full waveform inversion method.Therefore,it can be seen that the CDIB full waveform inversion method has the advantages of fast convergence,less computation time,and high computational efficiency;(2)The CDIB full waveform inversion method performs well in shallow layers,while the LBWP full waveform inversion method performs well in deep layers.Numerical experiments show that the proposed CDIB full waveform inversion method has certain effectiveness.