Research on seismic inversion method of total organic carbon content in shale based on facies constraint
Seismic prediction of Total Organic Carbon(TOC)content in shale is of great significance for the dessert evaluation of shale oil and gas and the exploration and development of shale.Taking the shale research of a block in the basin in eastern China as an example,this paper discusses the difficulties and existing problems in TOC prediction of shale organic carbon content and proposes a geophysical prediction technology and method of the total organic carbon content of shale based on the phase constraints.Firstly,the petrographic classification,P-and S-wave velocity,density,TOC,and clay of the logging data are analyzed,and the elastic parameters sensitive to the TOC of high-quality shale lithofacies and sweet spots are studied.The relationship between sweet spots parameters and elastic impedance is established according to the elastic impedance equations of P-and S-wave velocity and density.Through the Bayesian theoretical framework,and the prior distribution of shale TOC,high-quality lithofacies,and sensitive elastic parameters,a posterior probability distribution of TOC based on the joint constraint of facies constraint and the sensitive elastic parameter is established.The seismic inversion prediction of TOC is realized through the maximization probability algorithm.This method effectively improves the accuracy of the inversion results through phase constraints and is in good agreement with the measured results,which provides a reliable technique for further seismic evaluation of shale sweet spots.
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