Storage of CO2 in a partially water saturated porous medium at gas hydrate formation conditions

Storage of CO2 in depleted natural gas reservoirs is considered an attractive option to mitigate climate change concerns of CO2 from sources such as thermal power plants. In this regard, a number of depleted gas reservoirs located in Northern Alberta, Canada have been identified as potential sites for CO2 storage at temperature and pressure conditions at which CO2 forms gas hydrate crystals in the presence of water. This offers the possibility of storing more CO2 than what can be normally stored as a gas at the same conditions. The injection of CO2 in a bed of silica sand partially saturated with water (wet sand) at pressure and temperature conditions similar to those in a typical depleted gas reservoir in Northern Alberta was investigated in this work. The CO2 gas was injected into the simulated reservoir under the gas cap mode and the spiral tube mode procedure. Through the pressure drop measurements the CO2 gas consumption was determined and also the amount of water converted to hydrate was calculated. The results indicate that 39-47% of water formed hydrate in the gas cap mode gas injection experiments and 51-55% in the spiral tube mode injection experiments. Hydrate saturation reached 0.11-0.15 after 24 h for each gas injection mode. Finally, the capacity of the laboratory reservoir to store CO2 in various forms was determined.