Prestack forward modeling of tight reservoirs based on the Xu–White model

Abstract

Inversion methods for conventional reservoirs cannot be used in tight reservoirs because of small differences in wave impedance between tight reservoirs and surrounding rocks. Tight reservoirs in western China are characterized by strong heterogeneity; thus, it is difficult to predict favorable zones using conventional reservoir inversion methods. In this study, we propose an inversion method based on the Xu–White model. First, we modify the test parameters of the Xu–White model until model P- and S-wave velocities and density values agree with well-logging data. Then, we calculate P- and S-wave velocities, density, and Poisson ratio for different lithologies and oil saturation and construct different geological models for interbedded sand and shale. Subsequently, we use approximations to Zoeppritz equations to perform prestack forward modeling and analyze the response characteristics of prestack gathers for different physical properties, lithology, and oil saturation. We analyze the response of thirteen types of elastic parameters to porosity, clay content, and oil saturation. After the optimization of the real prestack gathers in the Z area of western China, we select an elastic parameter that is the most sensitive to lithology and oil saturation to predict the distribution of oil-producing reservoirs with high accuracy.