Fast synchrotron-based X-ray microtomography was used to image the injection of
super-critical CO2 under subsurface conditions into a brine-saturated carbonate sample at the
pore-scale with a voxel size of 3.64µm and a temporal resolution of 45 s. Capillary pressure
was measured from the images by finding the curvature of terminal menisci of both connected
and disconnected CO2 clusters. We provide an analysis of three individual dynamic drainage
events at elevated temperatures and pressures on the tens of seconds timescale, showing nonlocal
interface recession due to capillary pressure change, and both local and distal (non-local)
snap-off. The measured capillary pressure change is not sufficient to explain snap-off in this
system, as the disconnected CO2 has a much lower capillary pressure than the connected
CO2 both before and after the event. Disconnected regions instead preserve extremely low
dynamic capillary pressures generated during the event. Snap-off due to these dynamic effects
is not only controlled by the pore topography and throat radius, but also by the local fluid
arrangement. Whereas disconnected fluid configurations produced by local snap-off were
rapidly reconnected with the connected CO2 region, distal snap-off produced much more
long-lasting fluid configurations, showing that dynamic forces can have a persistent impact
on the pattern and sequence of drainage events.