The Study And Application On Methods Of Elastic Impedance Inversion And Fluid Discrimination

As poststack acoustic impedance inversion use the seismic data of full angle multiple stack, it weakens the reflection sensitivity of reservoir character. AVO analysis and inversion provides various lithology parameters, but it can be easily affected by many kinds of noise. Elastic impedance inversion approach overcomes the limitations of acoustic impedance inversion and AVO method, which preserves the information of prestack data, also avoids the effects of noise. However, elastic impedance is a parameter that can only be calculated out, therefore it has no clear physical meanings. So that it is quite valuable to carry out research on extracting lithology parameters from elastic impedance. Fluid identification is one of the most main contents of reservoir predication, so it is very important to analyze the fluid factors for the fluid discrimination.This paper introduces the basic theory of elastic impedance function firstly, and analyzes the precision of different kinds of elastic impedance equations. Then, introduces the basic theory and pivotal technology for the elastic impedance inversion. After that, I study the methods of extracting lithology parameters from elastic impedance under two situations according to the characteristic of real seismic data: first, when the incidence is big, by linear transforming to the elastic equations, the compressional and shear wave velocity and density can be extracted directly; in addition, I rewrite the equation for parameter extraction and derive an equation that can be used as extracting compressional and shear wave impedance and density directly from elastic impedance. Secondly, when the incidence is small, it is hardly to get three angle gather stack datum, I simplify the solution equation by using reasonable approximation, and then present the approach for estimating compressional and shear wave impedance or only shear wave impedance directly from elastic impedance. Whereafter, according to the relationship of different lithology parameters, the other parameters can be calculated. Besides, after getting the litholoty parameters, I analyzes the fluid factor methods, which can discriminate the different fluids with well log data analysis. The methods of fluid factor based on AVO analysis can discriminate gas sand. The methods of fluid factor based on Gassmann equation and Poission impedance can discriminate different fluids effectively by choosing different parameters. At last, I tests and applies those approaches discussed before into the exploration of Keneast and Yongxin oil field. The result shows that discussed methods in this paper are feasible and effective.