Time scales for migration and trapping of CO_2 in saline aquifers

摘要

CO_2 can be effectively immobilized during a CO_2 injection into saline aquifers by residual trapping through capillary snap-off of isolated bubbles of CO_2. Simulations of CO_2 injection were performed to investigate the interplay of viscous and gravity forces on capillary trapping of CO_2. Results of those simulations show that displacements in which gravitational forces are weak compared to the viscous forces trap significantly more CO_2 than do displacements with strong gravitational forces relative to the viscous forces. Significant fractions of the trapping of CO_2 due to relative permeability hysteresis occur on time scales of a few injection periods for a wide range of ratios of gravity to viscous forces. Trapping increases when effects of capillary pressure are included.