Capture of CO2 from large point sources and the subsequent placement of captured CO2 into a subsurface porous formation of the earth (geological storage) is considered an effective climate change mitigation strategy until the world’s energy systems become non-fossil dependent. Depleted gas reservoirs are such an attractive formation because the fluid trapping mechanisms and the reservoir properties are known. The storage potential in the world’s gas fields is estimated to be 520 Gt of CO2. One example of underground storage of CO2 is the Sleipner West gas field in the North Sea. Also, the Otway project in Australia demonstrated long-term storage in a gas field. The use of the gas hydrate process as part of a potential strategy to mitigate climate change in the current carbon dependent economy is discussed. Gas hydrate crystallization has been proven in the lab to be a new way of capturing CO2 form flue and fuel gas mixtures arising in conventional fossil fuel power plants and in industrial gasification sites respectively. Captured CO2 may also be stored as a solid gas hydrate, which is advantageous because solid storage reduces the mobility and migration of CO2 in the reservoir. Several depleted natural gas reservoirs in Alberta, Canada have significant CO2 storage potential at shallow depth and in gas hydrate state. Injected CO2 is stored in such reservoirs in its hydrate, gaseous and dissolved state. Based on laboratory trials we calculated a storage density of about 120 kg CO2/m3. Finally, methane hydrates in the earth may be a potential source of methane (a greenhouse gas) in the atmosphere if it is released in an uncontrolled manner (runaway greenhouse effect).

Gas hydrates and decarbonization of the energy sector

ACS Spring 2022

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