Hydrogen reactivity with wellbore and polymer-modified cements: experimental insights for safe underground hydrogen storage

Underground Hydrogen Storage (UHS) is a promising approach to store energy in large quantities to balance the fluctuation between renewable energy supply and overall energy demand. Compared to established underground natural gas storage, UHS imposes stricter requirements on gas tightness and long-term well integrity, which must be thoroughly investigated before implementation. While thermodynamic modelling suggests potential chemical reactions relevant to long-term stability, experimental data remain limited. Additionally, no studies have investigated polymer-modified cements, which exhibit promising material properties to meet the increased requirements. This study investigates the reactivity of hardened wellbore cement paste and polymer-modified cement paste with hydrogen under conditions of 50 °C and 100 bar over 4 weeks. To examine the individual effects of gas, temperature, and pressure on the reactivity, a combination of microstructural and mineralogical analyses, along with mechanical and physical properties evaluations, was conducted under various exposure conditions. The results indicate no detectable reactivity between hydrogen and the tested cement materials, supporting the feasibility of long-term and safe UHS using wellbore cements. • No detectable reactivity between hydrogen and hardened cement paste. • Microstructure analyses help to validate porosity and permeability measurements. • In contrast to thermodynamic models no change in mineral phases is observed. • Polymer-modified cements show promising properties to improve wellbore integrity.