Hydrate seal formation during laboratory CO2 injection in a cold aquifer

We report the flow resistance of liquid CO2 advancing through cold, water-saturated sandstone to mimic CO2 storage in a shallow aquifer. Sedimentary hydrate growth is determined by resistivity, temperature, and pressure measurements. Hydrate formation in the pore space resulted in significant pressure gradients and blockage of flow under most conditions. The effect of CO2 injection rate, initial water saturation, brine salinity, and temperature are investigated and discussed with respect to induction time and hydrate seal properties. We conclude that CO2 hydrates consistently form an effective and robust flow barrier in sandstone aquifer under local hydrate stable conditions. Rock permeability elimination, even at low initial water saturation (36%), indicates a pore-filling morphology of flow-induced CO2 hydrate. Flow discontinuity by hydrate formation is thus highly relevant as a sealing mechanism for storage of liquid CO2 near the base of the gas hydrate stability zone (GHSZ).