Multi-wave AVO reservoir elastic parameter inversion method based on precise Zoeppritz equation

Abstract

The invention relates to a multi-wave AVO reservoir elastic parameter inversion method based on the precise Zoeppritz equation. The method includes: a. defining amplitude scaling factors; b. counting the prior information of model parameters and calculating the covariance matrix of the relevance of the three parameters; c. building an initial elastic parameter model of the time domain; d. forward modeling the multi-wave seismic pre-stack gather based on the elastic parameter mode and the precise Zoeppritz equation and calculating the inversion residual error between the PP wave and the PS wave according to the forward modeling records and the actual records; e. building and solving the inversion objective function and obtaining the solution expression of the disturbance quantity of the model parameters; f. calculating the disturbance quantity of the model parameters according to the inversion residual error and the solution expression of the disturbance quantity; g. repeating and iterating the steps of d, e and f and obtaining an optimal model parameter. The multi-wave AVO reservoir elastic parameter inversion method based on the precise Zoeppritz equation effectively improves the calculating precision and the stability of the existing pre-stack AVO inversion method, and meets the requirement of the inversion identification of oil and gas reservoir of the seismic prestack, especially the requirement of the characterization of the shale gas reservoir.

Description

technical field [0001] The invention relates to oil and gas fields, shale gas seismic exploration and reservoir parameter prediction methods, in particular to a multi-wave AVO reservoir elastic parameter inversion method based on the accurate Zoeppritz equation. Background technique [0002] Using limited logging data, it is very difficult to describe the reservoir continuously in space. The accuracy of the 3D spatial model of the reservoir based on interpolation, extrapolation or simulation of well data depends on the number and spatial distribution of wells around the reservoir. When the number of wells around the reservoir is limited, the lateral resolution of the reservoir description based on logging is low, and it is difficult to realize the effective characterization of the interwell reservoir. Seismic data has good spatial continuity and plays a very important role in reservoir characterization. The high-precision inversion method makes the inversion results have g...

AI Technical Summary

Problems solved by technology

Due to the complexity of the precise Zoeppritz equation, the current AVO inversion is mainly based on the approximate formula of the Zoeppritz equation to extract the elastic parameters by using the information of the amplitude change with the offset on the prestack gather. The elastic parameter is directly inverted, and there are too many assumptions, especially when the incident angle (or offset) is large, there is a large calculation error, and the calculation accuracy cannot meet the fine characterization requirements of the actual reservoir

Although the full waveform inversion can use the information of the full wave field to predict the model parameters, it has a huge amount of calculation, and cannot meet the requirements of the fine characterization of the actual reservoir in terms of inversion scale and calculation efficiency, especially for the actual three-dimensional large offset multi-wave and multi-component seismic data

[0003] In summary, the current research on reservoir elastic parameter inversion methods based on pre-stack seismic data has the following problems: AVO inversion based on the approximate formula of the Zoeppritz equation cannot extract large offset information, and its adaptability is poor; In particular, the most common structure of shale gas reservoirs is the thin interbedded structure of shale-sandstone, with large differences in longitudinal elastic parameters, which greatly reduces the solution accuracy of the Zoeppritz approximate formula, and the AVO inversion method based on the approximate expression of the Zoeppritz equation is no longer Applicable to this type of reservoir; the current conventional AVO inversion methods do not directly invert the elastic parameters such as P-wave velocity, shear-wave velocity, and density, but obtain them indirectly, which reduces the accuracy of the inversion; the traditional pre-stack The AVO inversion method generally only considers PP wave data. PP wave data mainly contains P-wave velocity information, but is not sensitive to model velocity and density. Using PP seismic AVO data alone to invert S-wave velocity information and density has great uncertainty; How to effectively obtain the elastic parameter model information of the underground medium as prior information to reduce the uncertainty of the inversion and improve the accuracy of the inversion requires further research

The algorithm does not directly invert elastic parameters such as P-wave velocity, S-wave velocity, and density, but obtains them indirectly, which reduces the accuracy of the inversion; only PP wave data is considered, and PP-wave data mainly contains P-wave velocity information. But not sensitive to model speed and density

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