VTI Media Full Waveform Inversion And The Research On Constraint Of Logging Information

The conventional full waveform inversion is mainly applied to the acoustic isotropic medium.However,wave anisotropy exists widely in the earth medium,and the full wave-form inversion of single parameter as the acoustic velocity can not meet the actual needs.In particular,when full waveform inversion is applied to large aperture and wide azimuth data,the effects of conversion and anisotropy need to be specially considered,which re-quires that the single parameter full waveform inversion of acoustic approximation be extended to multi parameter full waveform inversion,including inversion of longitudinal and transverse wave velocity,density,anisotropic parameters,etc.For this reason,this paper firstly focus on the full waveform inversion of multi parameters in VTI media,and analyzes the inversion characteristics of anisotropic parameters.Secondly,aiming at the coupling effect of multi parameter inversion,the paper research on the algorithm of multi parameter full waveform inversion with logging information constraint,and apply the algorithm based on model relation constraint.Finally,aiming at the inversion accuracy problem,based on the Backus equivalent average theory,this paper proposes a full wave-form inversion result scale refinement method based on well logging data,to get a higher resolution inversion modelThe main research results are as follows1)The full waveform inversion of reflected wave based on wave field decomposition is realized.Based on Born approximation theory,the gradient kernel function of full waveform inversion is decomposed into migration component and tomographic compo-nent.The offset component mainly updates the direct wave path from the shot point to the detection point,and the updated path is shallow;the tomographic component can update the wave path from the reflection layer to the shot detection point,and the updated wave path is relatively deep,which can be used to update the medium and long wavelength components of the model.2)The multi parameter full waveform inversion of VTI media based on scattering integral method is realized.Combined with the observation system of surface excitation surface receiving,the problem of parameter selection of full waveform inversion of VTI media is analyzed by studying the radiation mode of different parameter combinations.3)In the anisotropic parameter combination v_n,?,?,there is a coupling between the parameter?and the depth.If the background?is inaccurate,there will be a deviation between the inversion speed and the actual speed in depth,and the inversion result will be larger.To solve this problem,this paper proposes an inversion method to correct the background?model by logging data.4)The inversion of multi parameter full waveform based on multi prior informa-tion constraint is realized.Based on the assumption of model continuity(transverse),the model information constrained full waveform inversion is proposed;based on the assumption of model local smoothness,the Tikhonov regularization and full variation regularization constrained full waveform inversion are proposed.5)The full waveform result downscaling inversion is realized.The key of upscaling method is to get smooth matrix.For the problem of scale refinement of full waveform inversion result,considering the coupling effect of multi parameter full waveform inver-sion and the accuracy of seismic illumination,it is proposed to scale the result of full waveform inversion based on logging data Refine the strategy.The innovation of this paper is reflected in the following three aspects:1)This paper presents a method to construct the background anisotropic parameter?,using the logging information.This method uses well logging information to construct the corresponding relationship between inversion horizon and actual horizon,and then obtains the background?.It overcomes the coupling of?and depth in VTI medium full waveform inversion parameter combination v_n,?,?,which results in inaccurate velocity inversion results.2)A model relation constrained multi parameter full waveform inversion method is proposed.In two parameter inversion of acoustic velocity and density,due to the influence of coupling effect,the density value obtained is often inaccurate.Based on the empirical relationship between the inversion parameters,this method constrains the gradient update of multi parameter full waveform inversion,so as to reduce the influence of parameter coupling effect,and the inversion results that are consistent with the actual model can be obtained.3)A downscale inversion method of full waveform inversion results based on well logging information constraints is proposed.