Visualization of CO2 flooding in an artificial porous structure using micromodels

Abstract:

Geological CO2 sequestration is one of the most important technologies to mitigate greenhouse gas emission into the atmosphere by isolating great volumes of CO2 in deep geological formations. This novel storage option for CO2 involves injecting supercritical CO2 into porous formations saturated with pore fluid such as brine and initiate CO2 flooding with immiscible displacement. Despite of significant effects on macroscopic migration and distribution of injected CO2, however, only a limited information is available on wettability in microscopic scCO2-brine-mineral systems. In this study, a micromodel had been developed to improve our understanding of how CO2 flooding and residual characteristics of pore water are affected by the wettability in scCO2-water-glass bead systems. The micromodel (a transparent pore structure made of 0.5 mm diameter glass beads between two glass plates) in a high-pressure cell provided the opportunity to visualize spread of supercritical CO2 and displacement of pore water in high pressure and high temperature conditions. CO2 flooding followed by fingering migration and dewatering followed by formation of residual water were observed through a imaging system with a microscope. Measurement of contact angles of droplets of residual water on and between glass beads in a micromodel were conducted to estimate differential pressure between wetting and nonwetting fluids in a scCO2-water-glass bead system. The experimental observation results could provide important fundamental informations on capillary characteristics of reservoirs and caprocks for geological CO2 sequestration.