Prestack Simultaneous Inversion And Its Application In Central Sichuan Dengying Formation Carbonate Reservoir Prediction

Central Sichuan basin carbonate reservoir of strong heterogeneity and complicated pore structure makes this type of carbonate reservoir have those features: irregular shape distribution, different origin, hidden distributed, vertical and horizontal direction mutation etc. Therefore, it is of great significance to study the suitable reservoir prediction method for the identification of carbonate reservoirs. Prestack inversion has long been a hot research topic in seismic attribute analysis and reservoir prediction. Compared with post-stack inversion, prestack inversion can get more direct reservoir properties, lithology and fluid content information.Based on rock physics, the Prestack P-wave and S-wave elastic impedance simultaneous inversion method is used for the second and fourth segment of Dengying formation carbonate reservoir prediction, this paper is mainly on the four aspects:Firstly, this paper introduced the development of seismic inversion technology at home and abroad. For the prediction of carbonate reservoirs in Central Sichuan basin, the research work of predecessors were described in this paper. The former mainly use the multidisciplinary methods of geology, geophysics and geochemistry, the research scale is from micro to macro, or the combination of both methods.Secondly, based on the data collected from 3 wells, the loss of shear wave velocity is predicted by the physical modeling of rock. Elastic parameters such as compressional wave velocity, shear wave velocity, density, elastic modulus, Poisson's ratio and so on contact the reservoir characteristics with seismic response. The rock physical model is mainly divided into contact model, effective medium model and adaptive model, which can effectively simplify the complex rock structure. Based on statistical analysis of mineral content of well logging data, the rock model of the study area was determined. The framework is composed of four kinds of minerals: dolomite, calcite, quartz and clay, which are filled with gas and water. Compared with the commonly used shear wave velocity prediction method, the Greenberg-Castagna method is more suitable for the carbonate rocks. The processing of the practical data illustrated the effectiveness of this method.Then basic theory of the Prestack P-wave and S-wave elastic impedance simultaneous inversion method is described. The key technologies which includes seismic and well data processing, seismic wavelet extraction and synthetic seismogram, the initial low frequency models establishment during the inversion process are respectively discussed.At last, the RockTrace module of Jason inversion software is used to predict the second and fourth segment reservoir of Central Sichuan basin Sinian Dengying formation. The prediction results fit well with the actual well data. The second segment of Dengying formation with the abundance of gas influencing, the shear wave velocity ratio is reduced. The reservoir displays with the characteristics: low P-impedance, low P and S wave velocity ratio. The fourth segment of Dengying formation displays with the characteristics: medium P-impedance, low P and S wave velocity ratio features. The siliceous dolomite displays with high P-wave impedance, low P and S wave velocity ratio.