Full waveform inversion method and system based on non-monotonic search technology

Abstract

The invention aims to provide a full waveform inversion method and system based on a non-monotonic search technology. The method comprises the following steps: firstly, dividing multi-scale inversionfrequencies into N frequency groups according to a set frequency group range; secondly, determining a speed model of next iteration corresponding to the jth frequency group according to the seismic observation data and an initial speed model by adopting a non-monotonic search technology in combination with the initial step length; judging whether j is greater than N or not; if j is greater than N,outputting the speed model of the next iteration corresponding to the jth frequency group as an optimal speed model; and finally, performing seismic imaging based on the optimal speed model. According to the method, the step length is determined by combining the non-monotonic search technology with the initial step length, so that a high-precision inversion result can be obtained on the premise of ensuring the inversion calculation efficiency; and when the initial speed model is poor, the global convergence of inversion can be ensured to a certain extent, and a good inversion result can be obtained.

Description

technical field [0001] The invention relates to the technical field of seismic exploration, in particular to a full waveform inversion method and system based on non-monotonic search technology. Background technique [0002] Full waveform inversion (FWI) comprehensively utilizes the full wave information in the seismic wave field, and quantitatively corrects the initial model by fitting the actual observed wave field and the predicted wave field, so as to reconstruct the parameter model of the underground medium such as velocity and density. It can provide rich elastic parameter information such as high-precision compressional and shear wave velocity and density for seismic exploration and exploration of the earth's internal structure. [0003] Full waveform inversion is generally a nonlinear data fitting process, which is repeated iteratively until the objective function formed by the observed data and the synthetic seismic data is small enough. First of all, it is necessa...

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Problems solved by technology

Although this type of method can also make the inversion converge, forcing the objective function to decrease successively will destroy the global convergence property of the inversion optimization method, and when the inversion falls into the vicinity of the local minimum, small step size and zigzag phenomenon will appear , reducing the computational efficiency and accuracy of the inversion, and the gradual decrease of the objective function is not conducive to protecting the global convergence of the inversion

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