The Application Of Pre-stack Simultaneous Inversion In Reservoir Prediction In Chunguang Oilfield

This paper focuses on applying the pre-stack simultaneous inversion to the prediction of oil and gas reservoir of Shawan. It is organized into three sections to illustrate the applications from different prospects.Firstly, this article introduce the Zoeppritz equation and its approximate formulas that establish the theoretical basis of modern seismic inversion in detail. By collating the formulas, we study the relationship between the reflection coefficient of seismic wave and the elastic parameters(such as P-wave velocity, S-wave velocity and density parameters) of the underground strata. Based on the Fatti equation which is one of Zoeppritz approximate formulas, pre-stack simultaneous inversion use the sparse pulse inversion to make multiple different angles of seismic stack into the elastic parameters(such as P-wave impedance, S-wave impedance and density) of the underground rock. Combining the inversion parameters in the form of mathematics, we will be able to get the elastic parameters(such as ?? and shear wave ratio) which are more sensitive to the variation of the fluid.Secondly, in order to solve the shortage of the shear wave logging data in pre-stack simultaneous inversion, we introduce the Xu-white rock physics model which has achieved good shear wave prediction effect in sandstone and mudstone area. This method can be used to predict the density curve, P-wave velocity and S-wave velocity curve of single well, and is based on Kuster-Toks?z model, Gassmann equation and difference effective medium theories. After completing derivation of the formula of the model, we can furtherly study how seismic P-wave and S-wave velocity in the subsurface is influenced on the rock physical parameters(such as clay content, water saturation and porosity) of the underground strata. As provide theoretical basis for the superiority of the elastic parameters(such as ??) which are related to shear wave information on the identification of the fluid.Finally, in this paper, the case which we study is from the Chunguang oilfield. The main geological difficulties of the area :the strata has the strong anisotropy;the variation of the lithology thickness changes fast in the lateral; The relationship between the oil and water in the reservoir is quite complex. Besides, by studying logging information, we find that the rock physics characteristics of the reservoir is very complicated, the Pimpendence of the water layer and the oil layer is the overlap, thus the post inversion can not identify the reservoir of the Chunguang oilfield.The elastic parameters of prestack simultaneous inversion is more sensitive to variation of fluid of the rock. The method has a good effect on the area in which the relationship between the oil and water in the reservoir is quite complex.by using Xu-white model of rock physics modeling method,we not only predict the shear wave data the C27-1 well lacks, also used to the density data predicted to correct density curve distortion of well C27-1. The Jason software is applied on the sandstone reservoir of the Chunguang oilfield for pre-stack simultaneous inversion.By analyzing the rock physics property of the sandstone reservoir and inverse result, it show that the elastic parameters ?? is the sensitive parameters of the area. Based on the sensitive parameters and the inversion results, we finished the Identify of the oil reservoir and the discrimination of the possible oil sandstone, we can achieved the reliable result of fluid identification on predicting reservoir and hydrocarbon.