Determination of CO 2 storage density in a partially water‐saturated lab reservoir containing CH 4 from injection of captured flue gas by gas hydrate crystallization

It has been demonstrated that CO 2 storage in depleted natural gas reservoirs at gas hydrate formation conditions is an opportunity to mitigate the emission of CO 2 from fossil fuel combustion or gasification sources. More than 100 depleted natural gas reservoirs located in Alberta, Canada were investigated and recognized as potential sites for CO 2 storage using hydrate technology. Treated flue gas captured from large stationary sources is generally a gas mixture of CO 2 with N 2 , O 2 , and other impurities. The depleted gas reservoirs still contain natural gas that was not economically recoverable. In this work CO 2 and a CO 2 /N 2 (90/10 mol%) gas mixture were used for injection in a laboratory reservoir that contained residual CH 4 . The experimental results indicated that about 80 % of the original water in the reservoir formed CO 2 hydrate after 120 h. The total CO 2 storage density (in hydrate, gaseous, and dissolved state) from the injection of the CO 2 /N 2 mixture into a 500 kPa CH 4 reservoir was found to be 118.6 kg/m 3 . The addition of a certain amount of tapioca starch in the reservoir delayed the onset of nucleation and improved the CO 2 storage density (121 kg/m 3 ). This storage density may also be achieved by compressing the gaseous CO 2 /N 2 mixture to 5220 kPa at 285 K. This study shows that hydrate technology provides more CO 2 storage density than other storage methods or the same storage but at much lower compression costs.