Three-dimensional Elastic Wave Numerical Simulation And Full Waveform Inversion Based On MPI

Full waveform inversion(FWI)is a popular seismic imaging technology developed in recent years.Compared with the conventional seismic inversion method,this method can use more seismic wave field data and has higher inversion accuracy.Although this method has been greatly developed in recent years,due to the high time cost of three-dimensional elastic full waveform inversion,the current research on this method is still focused on the two-dimensional and acoustic fields.The actual geological situation is three-dimensional,so there may be some problems with the two-dimensional inversion method.For example,without knowing the direction of the geological structure,the two-dimensional inversion may get wrong inversion results.With the increasing requirements for the accuracy of oil and gas exploration and engineering exploration,the two-dimensional forward and inverse method has become increasingly difficult to meet the actual exploration needs.Therefore,the full waveform inversion method needs to be extended to three dimensions.Parallelization algorithm is an effective method to expand the elastic full waveform inversion method from 2D to 3D,it can greatly improve the calculation efficiency of the program.Three-dimensional elastic wave forward modeling is the foundation of inversion.Therefore,to study parallel three-dimensional elastic wave full waveform inversion method,we must start from studying parallel threedimensional elastic wave forward modeling.This paper firstly studies the three-dimensional elastic wave numerical simulation method based on MPI parallel.Starting from the elastic wave equation,the article studies the implementation process of the high-order staggered grid effective difference method,and then makes a specific comparative analysis in terms of numerical dispersion,stability conditions,source loading and boundary conditions.Finally,through domain decomposition of the entire model area,parallel three-dimensional numerical simulation of elastic waves is realized based on MPI.In this paper,the effect of the method on surface wave simulation is verified by a uniform half-space model and a two-layer model.Then the feasibility and effectiveness of the method are further verified by a three-layer model and a slope fault model.Based on the parallel forward simulation,this paper studies the parallel elastic wave threedimensional full waveform inversion method based on the conjugate gradient method,and further improves the efficiency of the three-dimensional inversion through the time-frequency domain hybrid inversion method..The time-frequency domain hybrid inversion method is to perform forward inversion in the time domain and inversion in the frequency domain.This method can not only take advantage of the higher efficiency of time domain forward modeling,but also take advantage of the multi-scale inversion of frequency domain to ensure the efficiency and stability of the inversion process.Finally,through the analysis and research on the inversion results of the small-scale anomaly model,double-layer model and inclined fault model,the effectiveness and feasibility of the inversion method are proved.