Mechanical Evaluation of Selected Standard Oilfield Elastomers Under Simulated Subsurface Hydrogen Storage Environments

Abstract A primary concern in large-scale subsurface hydrogen storage is gas leakage through sealing elements due to prolonged exposure to hydrogen-rich gaseous environments. This study simulates subsurface storage conditions using an autoclave system with three different gases: carbon dioxide (CO2), methane (CH4), and hydrogen (H2). Three standard oilfield elastomers; Ethylene Propylene Diene Monomer (EPDM), Fluoroelastomer (Viton/FKM), and Nitrile Butadiene Rubber (NBR), were subjected to varying gas mixtures. Their mechanical properties were assessed both pre and post-exposure under different aging durations and experimental conditions. The effects of aging duration, temperature, and gas composition on the mechanical properties of elastomers were evaluated, with a specific focus on hydrogen and methane environments and their mixtures. A test matrix incorporating various gas ratios, temperatures, and pressures was developed for systematic experimentation. Mechanical performance of elastomers was assessed via Shore A hardness measurements and compression resistance tests. In both pure hydrogen and 50% H2–50% CH4 environments, a consistent trend was observed: an initial reduction in elastomer hardness followed by a gradual increase as aging progressed. This behavior was evident at both 25°C and 70°C, although more pronounced at 25°C. EPDM generally exhibited improved hardness and increased resistance to compressive strain at elevated temperatures in hydrogenated environments, despite poor resistance to compressive strain at lower temperatures. NBR experienced the greatest degradation in hydrogenated environments, showing high compressive strain values. Viton, in contrast, remained thermally stable in hydrogenated environments, and its resistance to strain increased with days at a constant high temperature. The observed changes in mechanical behavior are attributed to plasticization effects on polymer chains, and crosslink density variations due to chain growth or scission, induced by chemical aging. These findings highlight potential material degradation risks associated with hydrogen exposure standard oilfield elastomers. The results provide valuable insights for material selection in underground hydrogen storage systems to ensure long-term seal integrity. Furthermore, they underscore the necessity of developing more resilient elastomeric materials for extreme subsurface environments to support the safe and sustained deployment of large-scale hydrogen storage infrastructure.