Simulations of upward leakage of CO₂ in long-column flow experiments: Effect of lateral boundary condition

Large-scale laboratory experiments can play a key role in improving understanding of CO₂ migration, phase change, and trapping processes. Critical to the design of such experiments are defensible configurations that mimic relevant subsurface flow scenarios. We are simulating CO₂ and brine flow in high-pressure long-column pressure vessels (LCPVs) using TOUGH2/ECO2M to design upward migration and leakage experiments. The experiments are designed for a large-scale facility such as the property laboratory CO ₂ Investigation" (LUCI) LUCI would consist of one or more vertical LCPVs a few hundred meters in length and filled with porous materials. The outer wall of the LCPVs will be fitted with heaters and wrapped in insulation to create either temperaturecontrolled or insulated sidewall boundary conditions. The complex flows that develop as CO2 moves upward in the LCPV can be understood by looking at the evolution over time and space of pressure, temperature, phase saturation, and fluid density. Radial 2-D simulations show that results are very sensitive to the choice of outer sidewall thermal boundary conditions. For the case of constant geothermal-gradient temperature on the outer wall, there is very little liquid CO₂ formed as heat from the sidewall counteracts decompression cooling and the CO₂ remains either supercritical or gaseous, depending on pressure. For the case of an insulated sidewall, upward migration of CO₂ and related decompression cooling leads to three-phase conditions through the formation of liquid CO₂ in equilibrium with gaseous CO₂ and brine. The strong dependence of flow on boundary conditions and relative permeability assumptions underlines the need for large-scale laboratory experiments. We are actively seeking a site for LUCI.