Visualization of hydrate formation during CO2 storage in water-saturated sandstone

Formation of solid CO2 hydrates during geosequestration of CO2 may offer increased storage capacity and provide extra sealing in cold aquifers. Evaluation of the integrity and distribution of the formed hydrate seal requires comprehensive knowledge about the CO2 flow and hydrate growth pattern within sedimentary pores. We address this knowledge gap by pore-to core-scale visualization of hydrate formation during liquid CO2 injection in water-filled sandstone (P = 70 bar, T = 1-2 degrees C). Pore-level hydrate growth is analyzed by direct imaging of the pore space in a micromodel chip that is an analog to the pore network in a sandstone. Flow visualization of CO2-water drainage followed by hydrate formation is also presented at core-scale in Bentheim sandstone using high-field MR imaging. The image results verified hydrate nucleation both at the liquid-liquid interface and in the water phase alone due to the presence of dissolved CO2. The pore-filling hydrate growth pattern effectively reduced the sandstone permeability and showed the potential of CO2 hydrate as a sealing mechanism during CO2 sequestration.