Events

Speaker:  Dr. Charlotte Garing, Postdoctoral researcher, Department of Energy Resources Engineering at Stanford University

Title of Seminar: “Pore-scale investigations into the stability of residual CO2”

Abstract: The long-term reliability of residual (capillary) trapping is a key process for CO2 storage security and efficiency. After an initial drainage phase during injection, substantial supercritical CO2 (scCO2) volumes are disconnected from the plume during brine imbibition.

Whereas conventional multi-phase flow models assume that residually trapped portions of the plume are permanently immobilized, multiple physiochemical mechanisms exist which could potentially invalidate this assumption. One mechanism is CO2 transfer driven by differences in capillary pressure between disconnected neighbor ganglia, called Ostwald Ripening. The potential for Ostwald ripening was assessed by calculating pore-scale capillary pressure distribution in sandstones using a multi-scale X-ray microtomographic (micro-CT) datatset of residually trapped air after a simple gravity-driven imbibition experiment. The data suggest that Ostwald ripening may occur, leading to gas transfer from ganglia with higher capillary pressures to surrounding ganglia with lower capillary pressures.

Previous studies have measured scCO2 residual trapping at in situ conditions in order to better understand and characterize the control of the formation attributes on residual trapping and the feedbacks between residual, solubility and mineral trapping. However most experimental work have investigated residual CO2 immediately after imbibition. The stability of residually trapped scCO2 was observed during the early stages following imbibition by conducting a CO2-brine drainage-imbibition experiment in a sandstone with reservoir conditions and using time-resolved synchrotron micro-CT imaging. The data show that fluid phase distribution was not stable with time over the course of the experiment. We hypothesize that fluid displacement may be caused by local capillary equilibration following the imbibition process. The detailed analysis of the temporal evolution of scCO2 ganglia also suggests that a small fraction of mobile scCO2 may reconnect most surrounding disconnected ganglia.

Biography:   Charlotte Garing is a postdoctoral researcher in the department of Energy Resources Engineering at Stanford University (Sally Benson’s group). She received her Ph.D in Geosciences from the University of Montpellier, France, in 2011. Her thesis focused on field characterization and laboratory investigation of reactive transport in carbonates. Her current research examines fundamental characteristics of CO2 residual trapping at the pore scale in the context of geologic carbon storage. She is involved in the Global Climate and Energy Project (Stanford University) and the Energy Frontier Research Center for Nanoscale Controls on Geologic CO2 (DOE).