Inertial Effects in Pore-scale Fluid Displacement in Real Rock Geometries

Direct numerical simulation of flow in porous media plays an increasingly important role in understanding pore-scale flow physics and obtaining constitutive parameters for upscaling, thanks to the improvement of numerical models and increase in computational capability. Inertial effects are largely ignored in such simulations as the bulk Reynolds number (Re) is very small. However, recent micromodel experiments show that the local Re could be much higher than the bulk Re and the inertial effects may not be negligible, particularly in a scCO₂ - brine system. Our previous drainage simulation results [1, 2] show that inertial effects have a significant impact on fluid displacement patterns and residual saturation in both a heterogenous micromodel and a real sandstone sample, at both high and low capillary numbers. In addition, the change of the invasion patterns is not proportional to the change of inertial effects, thus exhibiting threshold behavior.

In this work, we further extend our existing simulation work to study the inertial effects under different wetting conditions and rock geometries. We employ the CSF (continuum-surface-force) based color-gradient lattice Boltzmann multiphase model and geometrical wetting model to reduce spurious currents and eliminate artificial films. The simulations are performed on a GPU-based supercomputer which enables us to simulate sufficient large rock samples, with approximate half billion grid nodes, at realistic capillary numbers.

Chen, Y., et al., Lattice Boltzmann simulations of liquid CO2 displacing water in a 2D heterogeneous micromodel at reservoir pressure conditions. Journal of Contaminant Hydrology, 2018. 212: p. 14-27. Chen, Y., et al., Inertial Effects during the Process of Supercritical CO2 Displacing Brine in a Sandstone: Lattice Boltzmann Simulations based on the Continuum-surface-force and Geometrical Wetting Models. (Under review).