Researchers at Sandia National Laboratories are investigating the potential of using depleted oil and natural gas reservoirs as hydrogen storage.
They consider hydrogen a crucial clean fuel that has various potential uses and is capable of long-term storage. Their findings were published in the International Journal of Hydrogen Energy.
Tuan Ho, Sandia chemical engineer leading the research, suggests hydrogen could be beneficial for seasonal and long-term storage. The excess electricity produced by solar energy during summer months can be converted into hydrogen and stored till winter – a period when more heating is required.
Storing large amounts of hydrogen in above-ground metal tanks presents difficulties due to its volumetric energy density. Thus, the exploration of underground storage. While salt caverns can be used for this purpose, they are not evenly distributed across the U.S. Therefore, this team is studying if storage in depleted oil and gas reservoirs could prove feasible without leakage, contamination, or getting stuck in the reservoir’s rock formations.
Initially, the team studied whether the hydrogen would remain trapped in the sandstone or shale that forms many oil and gas reservoirs. Both laboratory experiments and computer simulations were carried out. They concluded that hydrogen doesn’t remain trapped inside sandstone but up to 10% of adsorbed gas was stuck inside shale samples.
Further research on specific types of clay common around oil and gas reservoirs showed minimal loss of hydrogen in clay. These findings, seen as a positive for underground storage, were published in the journal Sustainable Energy and Fuels.
It was discovered that injecting hydrogen into a depleted natural gas reservoir can release residual natural gas into the hydrogen. Consequently, when the hydrogen is removed for use, it will contain a small amount of natural gas – this can result in a small amount of CO2 being produced when burned. Now, the team is investigating the potential interaction between leftover oil and hydrogen gas in depleted oil reservoirs.
Examining depleted oil and natural gas reservoirs for hydrogen storage will guide large field-scale tests, says Don Conley, manager for Sandia’s underground hydrogen storage projects. The Subsurface Hydrogen Assessment, Storage, and Technology Acceleration (SHASTA) project plans to conduct these tests to prove the feasibility of this storage method.
