The Study Of Pre-stack Three-parameter Simultaneous Inversion Based On Dipole Seismic Wavelet

In view of the influence of the reflection coefficient and the low frequency model for seismic inversion,on the basis of the analysis in the study of reservoir seismic velocity and spectral characteristics,to establish the relationship between reservoir seismic characteristics and reservoir parameters,but also an important part of reservoir seismic inversion research.According to the fact that top and bottom reflections of a reservoir always appear in pairs,we call them dipole-like seismic wavelet or seismic dipole.A seismic dipole which depicts the overall characteristic of a reservoir can be taken as a principal research tool in this dissertation,therefore I innovatively construct dipole–based convolution model,dipole–based seismic response characteristic analysis method and provide a multiple integral mathematical expression for calculating seismic dipole wavelet and an equation set delineating reflectivity properties from the reservoir top and bottom interfaces.The seismic dipole–based researches show that the odd-number multiple integral value is dependent on the relative impedance of a reservoir and an even-number multiple integration strong amplitude is related to seismic reflective interface attributes.It is obvious that the reservoir thickness and its seismic relative impedance can be predicted using the multiple integral data and the dipole–based reservoir prediction theory can be formed.Thin bed layer theory model confirmed: the reservoir thickness prediction is realized by the energy constrained reservoir thickness spectrum.Resolution test confirmed that the resolution of reservoir thickness and layer thickness is proportional.The thicker layer is,the more easily reservoir distinguish.In the case of relatively simple geological condition,the precision of the thickness can reach ?/16(?is wavelength).For the most difficult to predict thin bed layers,the thickness of the identification is still up to ?/8.In the constraint of multi-level stage sedimentary micro cycle,the use of multi-level wavelet reconstruction is used to improve the prediction accuracy of thin interbed.Using multiple order differential technique to highlight the information of higher frequency band of seismic relative impedance data,to improve the ability of distinguishing thin reservoir.Through the reliability analysis of seismicand well logging data,further prove that the low frequency information of the multiple integral recovery is matched with frequency division impedance of well logging in the same frequency band,which is the foundation for the frequency band model construction of the seismic inversion.Seismic inversion depends on the accuracy of the initial low frequency impedance or velocity model,the accuracy of velocity prediction of pre-stack gathers wave is improved by using the method of pre-stack seismic gathers point by point continuous velocity prediction for the first time.Duo to the root mean square(RMS)velocity's variation is more sensitive to time,which results in that the requirements for the authenticity of seismic data and resampling efficiency are higher.Seismic waveform constrained interpolation method can effectively improve the interpolation effect of time sampling,and improve the accuracy of the calculation of the continuous root mean square velocity of the pre-stack seismic gathers,It is helpful to establish the high precision layer velocity model,and has good prediction effect on the low frequency segment.The method of parameter decomposition is adopted for the complexity of the construction of the objective function step by step.Firstly,the self correlation function,the amplitude envelope,the differential characteristic curve and so on are adopted.Accurate calculation of important wavelet frequency,phase and attenuation characteristic parameters.To solve the problem of prediction of the rapid variation of time and space of wavelet frequency and delay time.It is clear that the sequence of the optimization of the seismic wavelet sensitive parameters is the video frequency,the delay time,the attenuation coefficient.then through the sensitivity analysis of elastic parameters,pointed out that the optimization order is the thickness of the reservoir,P-wave velocity,S-wave velocity and density.Multiple parameter step by step constraint to realize the prediction of reservoir thickness of dipole wave to the reservoir structure and the inside inversion.Aiming at the problem of large amount of computation and insufficient seismic accuracy in the current pre-stack full waveform inversion,This study is based on the prediction of seismic multiple calculus thickness and the low frequency model of pre-stack fine velocity,drawing on mature pre-stack wave impedance inversion and AVO inversion method,and combining the characteristics of seismic wave travel time and seismic wave field dynamic,The reservoir characteristics of the multiple integral and multi-order differential relative impedance conversion of the seismic trace are reconstructed.A technique is proposed to realize the pre-stack three parametersseismic inversion of dipole wave.Compile and debug the pre-stack seismic inversion related algorithm program,good application results have been achieved in the prediction of the actual carbonate rocks,tight sandstone and fractured bedrock reservoir,and has applied for four patents of invention.