Unstable Drainage Dynamics During Multiphase Flow Across Capillary Heterogeneities

Abstract We use novel, fast 4D Synchrotron X‐ray imaging with large field‐of‐view to reveal pore‐ and macro‐scale drainage dynamics during gas–brine flow through a layered sandstone rock sample. We show that a single centimeter‐scale layer, similar in pore size distribution to the surrounding rock but with reduced connectivity, temporarily inhibits, and redirects gas flow, acting as a capillary barrier. Subtle variations in gas invasion upstream of the barrier lead to different downstream migrat