Effects of Pore Structure Evolution on Elastic Wave Velocities and Permeability of Tight Sandstones under Pressure

Summary

Permeability is a critical parameter for reservoir characterization and hydrocarbon development, yet its accurate prediction remains a challenge. Pore structure, as the intrinsic factor governing both the elastic and hydraulic transport properties of rocks, serves as a bridge between these properties and facilitates permeability prediction from well logs and seismic data. To accurately describe the variation in the physical properties of tight sandstone reservoirs with pressure, our study aims to construct a physical model that relates rock elastic properties with permeability. We developed a dual-porosity rock physics model by coupling David & Zimmerman’s pore-structure inversion method with Dienes’s percolation theory. Our model divides the pore space into pressure-insensitive stiff pores and pressure-sensitive compliant microcracks. By inverting the microcrack density and aspect ratio distribution-which evolve with pressure-from elastic wave velocities, we quantitatively predict permeability variations using Dienes statistical percolation model. To validate this model, we measured porosity, permeability, and P- and S-wave velocities on four tight sandstone samples under effective pressures of 5 to 50 MPa. The results show that the proposed model accurately captures the evolution of both elastic parameters and permeability with effective pressure, demonstrating strong predictive capability for the experimental data. The significance of this study lies in achieving a quantitative relation between elastic and transport properties by explicitly characterizing the pore structure and integrating percolation theory, which is then calibrated with real experiment data, thereby providing solid physical basis for better prediction of reservoir permeability using acoustic logs and seismic data.