Pore-scale modeling of two-phase flow: A comparison of the generalized network model to direct numerical simulation

Despite recent advances in pore-scale modeling of two-phase flow through porous media, the relative strengths and limitations of various modeling approaches have been largely unexplored. In this work, two-phase flow simulations from the generalized network model (GNM) [Phys. Rev. E 96, 013312 (2017); Phys. Rev. E 97, 023308 (2018)] are compared with a recently developed lattice-Boltzmann model (LBM) [Adv. Water Resour. 116, 56 (2018); J. Colloid Interface Sci. 576, 486 (2020)] for drainage and waterflooding in two samples-a synthetic beadpack and a micro-CT imaged Bentheimer sandstone-under water-wet, mixed-wet, and oil-wet conditions. Macroscopic capillary pressure analysis reveals good agreement between the two models, and with experiments, at intermediate saturations but shows large discrepancy at the end-points. At a resolution of 10 grid blocks per average throat, the LBM is unable to capture the effect of layer flow which manifests as abnormally large initial water and residual oil saturations. Critically, pore-by-pore analysis shows that the absence of layer flow limits displacement to invasion-percolation in mixed-wet systems. The GNM is able to capture the effect of layers, and exhibits predictions closer to experimental observations in water and mixed-wet Bentheimer sandstones. Overall, a workflow for the comparison of pore-network models with direct numerical simulation of multiphase flow is presented. The GNM is shown to be an attractive option for cost and time-effective predictions of two-phase flow, and the importance of small-scale flow features in the accurate representation of pore-scale physics is highlighted.

Automated summary

Despite recent advances in pore-scale modeling of two-phase flow through porous media, the relative strengths and limitations of different modeling approaches remain largely unexplored. This study compares two-phase flow simulations from the generalized network model (GNM) and the lattice-Boltzmann model (LBM) for drainage and waterflooding in two different samples. The results show that the GNM captures the effect of layers and provides predictions closer to experimental observations, while the LBM fails to capture layer flow and shows discrepancies with experimental data. The importance of small-scale flow features in accurate pore-scale physics representation is highlighted.