Petrophysical properties of three reservoir models by means of AVA data modeling

Abstract

Summary Amplitude Versus Angle (AVA) modeling has been performed to find out effects of porosity and fluid type of three different reservoir rock types. We used two layer earth models with shale/limestone, shale/sandstone and shale/shaly sandstone horizontal interfaces. Our upper layer consists of nonpermeable shale unit and lower reservoir layer has permeable rocks with different percentage of porosities. Each interface is modeled with assumption of reservoir rock has porosities of 10%, 20% and 30%. Reservoir rocks are assumed with gas, oil and brine saturated. AVA gathers were created by using the matrix form of the Zoeppritz equations for these three trap models. Three dimensional graphs that show the reflection coefficients versus incident angle and porosity produced for better interpretations. Increasing porosity in all the models reduces the amplitudes from positive values to negative values. In every trap model increasing porosity ratios change the AVA curve significantly and thus the AVA class type can change especially in shale–sandstone interface model. Lithology and porosity are the main factors effecting on the angle dependent reflectivity for all the three models. Change in the rock fluid type is less effective for the AVA anomalies in these models.