The Imaging of Dynamic Multiphase Fluid Flow Using Synchrotron-Based X-ray Microtomography at Reservoir Conditions

Fast synchrotron-basedX-raymicrotomographywas 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 45s. Capillary pressure wasmeasured 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.