Quantifying the Dynamics of Water-CO2 Multiphase Flow in Microfluidic Porous Media Using High-Speed Micro-PIV

Multiphase flow in porous media is central to a large range of applications in the energy and environmental sectors, such as enhanced oil recovery, groundwater remediation, and geologic CO2 storage and sequestration (CCS). Herein we present an experimental study of pore-scale flow dynamics of liquid CO2 and water in two-dimensional (2D) heterogeneous porous micromodels employing high-speed microscopic particle image velocimetry (micro-PIV). This novel technique allowed us to spatially and temporally resolve the dynamics of multiphase flow of CO2 and water under reservoir-relevant conditions for varying wettabilities and thus to evaluate the impact of wettability on the observed physics and dynamics. The preliminary results show that multiphase flow of liquid CO2 and water in hydrophilic micromodels is strongly dominated by successive pore-scale burst events, resulting in velocities of two orders of magnitude larger than the bulk velocity. When the surface wettability was altered such that imbibtion takes place, capillarity and instability are significantly suppressed, leading to more compact and axi-symmetric displacement of water by liquid CO2 with generally low flow velocities. To our knowledge, this work represents the first of its kind, and will be useful for advancing our fundamental understanding and facilitating pore-scale model development and validation.