Prestack seismic direct prediction of permeability, pore structure, matrix, and fluid parameters based on rock-physics model approximations

ABSTRACT In reservoir characterization and evaluation, permeability, pore structure, and properties of matrix and fluid are the driving parameters used to estimate hydrocarbon reserves and predict reservoir productivity. However, the quantitative relationships between these parameters and the reservoir’s elastic properties exhibit nonlinear characteristics or lack a well-defined mapping, posing significant challenges for predicting or inverting these parameters from seismic data. Therefore, we develop a rock-physics model that considers the influence of permeability, which is used to establish the rock-physics relationships and elucidate the elastic response patterns of microscopic physical parameters. Based on theoretical analysis of rock physics, we define an indicator of permeability and determine pore structure parameters. Subsequently, the rock-physics model is subjected to a Taylor first-order approximation. Then, the linear rock-physics relationships are incorporated into Russell’s linear approximation and combined with the Gassmann fluid term to derive a P-wave reflectivity approximation equation that incorporates permeability, pore structure, matrix, and fluid information. The approximation accuracy and the feasibility of the equation are validated through an analysis of reflection characteristics. Finally, based on the novel P-wave reflectivity equation, a prestack seismic direct prediction method for permeability, pore structure, matrix, and fluid parameters is further developed within a Bayesian framework. Model testing and field data validate the applicability and effectiveness of the method.