Pore-scale Evolution of Trapped CO2 at Early Stages Following Imbibition Using Micro-CT Imaging

A CO2-brine drainage and imbibition cycle was performed in a Boise sandstone sample at reservoir conditions (1300 PSI, 44 degrees C) at the Advanced Light Source, LBNL. The sample was repeatedly imaged, at the pore-scale, using synchrotron-based X-ray microtomography. In particular the temporal evolution of residually trapped CO2 was monitored for about 30 hours in order to quantify fluid stability at early stages following imbibition. The data show that fluid phase distribution distribution was not stable with time over the course of the experiment. We hypothesize that fluid displacement is caused by local capillary equilibration following the imbibition process