Method And Application Of Multiwave Prestack Joint Inversion Lithologic Parameters In VTI Media

In terms of the problems in lithologic exploration of reservoir geophysics, in order to improve the accuracy of lithologic parameters inversion and directly predict lithology and oil-gas, taking anisotropic media as geological model, due to the precise reflection coefficient formula in anisotropic media, making full use of multiwave seismic data, adapting linear and no-linear joint inversion algorithm and considering the effect of seismic wavelet, this paper proposes a multiwave joint inversion method based on waveform in anisotropic media, which can obtain P-wave velocity, S-wave velocity, density and anisotropic coefficients. Furthermore according to petrophysics theory, by transformed and combined lithologic parameters, reservoir parameters and elastic parameters, complicated reservoir description and recognition are carried out with multiple properties, which is proved to be correct, effective and advanced by processing the real data. The main achievements of research include four aspects as follow:1) The precise seismic multiwave reflection and transmission coefficient formula in anisotropic media (VTI) is deduced systematically by studying a lot of literatures on AVA. Theoretic AVA modeling has indicated that the precise formula has higher precision than various kinds of approximate formulas, and proved the correctness and adaptability of precise formula.2) Based up on AVA precise forward formula, prestack multiwave associated inversion method based on waveform has been proposed, which can obtain P-wave velocity, S-wave velocity, density and anisotropic coefficients, and the correctness and feasibility of the method are verified with a theoretical model.3) Using the lithologic parameters by inversion and rock physics theory, the author describes the fundamental theory of reservoir characterization with multiple-attribute and the mathematic relationship among lithologic parameters, elastic parameters and reservoir parameters. The dependent relation among multiple parameters, lithology and oil-gas is analyzed, which provides basis for multiparameter reservoir evaluation.4) Mutiwave AVA forward/inversion methods and multiattribute AVA interpretation theory in this paper are used to the processing of 2D3C and 3D3C actual seismic data, the lithologic parameters with remarkable characteristic and kinds of elastic parameters are obtained. With multi-parameter interpretation, new information about oil and gas can be obtained, which provide a new way for lithology identification, petrophysical properties prediction and fluid detection.