Using high-speed micro-PIV to investigate pore-scale interactions of liquid CO$_2$ and water in 2D porous micromodels with varying wettabilities

Multiphase flow of supercritical CO$_2$ and water in porous media is relevant to geologic carbon sequestration and enhanced oil recovery, among many other applications in the energy and environmental sectors. Resolving pore-scale transient flow dynamics is crucial to understanding the underlying physics and informing large-scale predictive models. To that end, an experimental investigation of the pore-scale flow dynamics of liquid CO$_2$ and water in two-dimensional (2D) circular porous micromodels with different surface characteristics is conducted employing high-speed microscopic particle image velocimetry (micro-PIV). The design of the micromodel minimized side boundary effects due to the limited size of the domain. The high-speed micro-PIV technique resolved the spatial and temporal dynamics of multiphase flow of CO$_2$ and water under reservoir-relevant conditions, for both drainage and imbibition scenarios. These novel measurements enable direct observations of the meniscus displacement, revealing a significant alteration of the pore filling mechanisms during drainage and imbibition. And pore-scale velocity fields were statistically analyzed to provide a quantitative measure of the role of capillary effects in these pore flows.