Experimental studies of well integrity in cementing during underground hydrogen storage

Underground Hydrogen Storage (UHS) in the subsurface is an alternative to overcome limitations associated with a fluctuating production of renewable energy sources. The excess energy produced can be converted to hydrogen and stored in porous media. Hydrogen is injected and produced from geological formations via wells. There are several concerns regarding the interactions of hydrogen with the different well components responsible for maintaining proper well integrity, such as cement. This experimental study investigates the interaction between molecular hydrogen and cement Class H by characterizing samples using different physical and chemical tests. Results showed samples exposed to molecular hydrogen exhibited a greater compressive strength in both the short and long terms. Porosity and permeability were found to be lower in samples exposed to molecular hydrogen. NMR distributions showed a reduction of larger pores and an increase of smaller pore spaces. Acoustic velocities showed an increase of Young's Modulus, Shear's Modulus and a slight decrease in Poisson's ratio. The compositional analysis demonstrated that hydrogen presence increases the amount of portlandite and ettringite formed. The crystalline needle-shaped structure observed in the SEM confirmed the presence of portlandite and ettringite within some of the larger pores. This experimental study showed that molecular hydrogen present could increase the formation of portlandite and ettringite, causing a shift in the porosity distribution increasing the mechanical strength of the cement.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.