Impact of Velocity-Dependent Relative Permeability and Fines Migration on CO2 Storage in Aquifers: A Hybrid Analytical-Numerical Upscaling Framework

Summary

The aim of this study is to develop an analytical model for axisymmetric gas-water flows in heterogeneous geological formations applicable to carbon dioxide (CO2) storage in deep saline aquifers. The novel method integrates numerical upscaling with an analytical reservoir model for predicting sweep and injectivity during CO2 injection. Pseudophase permeabilities are obtained from 2D numerical simulations, based on an averaging across layers and explicitly capturing velocity-dependent relative permeability reduction caused by fines-migration-induced formation damage. Using these upscaled properties, an exact analytical solution for radial gas-water flow is derived, providing explicit expressions for pressure drop, saturation distribution, sweep efficiency, and well impedance. We show that injectivity is highly sensitive to the vertical permeability profile and the extent of fines-induced damage. When permeability decreases with depth, gravitational segregation amplifies rate-dependent injectivity loss. In contrast, formations with permeability increasing with depth sustain a two-phase mixture zone that propagates outward, producing a different injectivity response. The analysis shows that incorporating velocity-dependent pseudopermeabilities altered by formation damage is essential for accurate injectivity and sweep prediction. The developed framework offers a fast, physics-based tool for quantifying injectivity losses and sweep efficiency in heterogeneous aquifers.