  The partial differential equations describing immiscible, but soluble, carbon
dioxide (CO2) displacement of brine are developed including local mass-transfer
effects. Scaling relationships for characteristic time among laboratory and
representative storage formation conditions are found upon assumption that
free-phase CO2 transport during injection is dominated by convection. The
implication is that an hour in the FluidFlower (large-scale visual model)
scales to hundreds of years of elapsed time in the storage formation. The
scaling criteria permit extrapolation of the effects of changes in parameters
and operating conditions. Interphase mass transfer allows CO2 to saturate the
brine phase and such mass transfer is a significant nonequilibrium phenomenon.
Significant mixing of CO2 dissolved into formation brine with original brine is
found experimentally and is also predicted. The magnitude of onset time for
downward migrating fingers containing CO2 is typically only a fraction of the
duration of CO2 injection and in general agreement with theoretical analysis in
the literature. Predictions for onset time of convective mixing at
representative storage formation conditions likewise teach that the onset time
for viscous fingering is significantly less than the duration of CO2 injection
in some cases. The implications of this observation include that mixing of CO2
with brine and the subsequent settling due to gravity are relatively rapid and
coincide with the period of active CO2 injection.
