  Carbonates are highly heterogeneous formations with large variations in pore
size distribution and pore space topology, which results in complex multiphase
flow behavior. Here we investigate the spontaneous imbibition behavior of
fluids in vuggy carbonates. Glass beads of 1.0 mm diameter, with dissolvable
inclusions, are sintered to form multiple configurations of heterogeneous vuggy
core with variations in matrix porosity, vug size, vug spatial location, and
number of vugs. The core fabrication process is repeatable and allows the
impact of vug textural properties to be investigated in a controlled manner.
  Capillary rise experiments are conducted in these proxy vuggy carbonate core
and compared with the homogeneous non-vuggy core as reference. Continuous
optical imaging is performed to track the position of the air-water interface
in the cores. To understand the change in capillary height in the presence of a
vug, a volume-of-fluid two-phase numerical simulation is performed in a
parallel set of connected and disconnected tubes. Finally x-ray tomography
scans are performed to identify the shape of the air-water interface in a
select few cores.
  The results can be summarized as follows: disconnected vugs result in higher
capillary rise compared to non-vuggy porous media. The vugs act as capillary
barriers, diverting fluid flow to the adjacent connected channels, which
ultimately results in a higher overall capillary rise.
  The results of this work highlight that radius of spontaneous invasion of
aqueous phases, such as fracture fluid and hazardous wastes, are affected by
vug porosity but not their distribution.
