Research On Time Domain Multi-parameter Full Waveform Inversion Method Based On Optimized Envelope

The seismic exploration environment is more and more complex,but the exploration requirements are getting higher and higher.Although it is difficult to study high-complexity media,such challenges are very necessary.The more complex the simulated media is,the closer it is to the true conditions.In this paper,the problems related to multi-parameter elastic wave inversion are studied,which have important theoretical significance and application value for the description of oil and gas reservoirs and the deepening of geological understanding.FWI can estimate accurate and reliable underground parameters through an interactive update method.However,there is usually a lack of recorded low-frequency information,which will greatly affect the inversion results.To solve this problem,we can use the envelope operator to demodulate the low frequency information and recover the long wavelength components when the low frequency information is lost.In addition,we propose a multi-step inversion scheme for multi-parameter FWI to reduce multi-parameter coupling.This paper started from the elastic wave forward simulation,and then optimize envelope inversion.Finally,based on the optimization of the envelope and combined with optimized multi-parameter inversion,the elastic wave full waveform inversion study are performed.The second chapter introduces the related problems of elastic wave forward.It mainly uses the finite difference method to solve the wave equation of elastic wave,and analyzes the problems of dispersion and absorption boundary in the forward process.Based on the second chapter and the traditional envelope inversion,the third chapter gives the theoretical framework of optimized envelope inversion and derives the corresponding gradient formula and objective function.The fourth chapter optimized the traditional multi-parameter inversion strategy,and gave a four-step inversion strategy.Combined with the optimized envelope inversion,the model test shows that the effect is better than conventional elastic waveform inversion.