Multiscale mechanisms of foam injection for enhanced underground hydrogen storage: Experimental and simulation insights from pore to reservoir scale

Underground hydrogen storage in geological formations, such as depleted oil and gas reservoirs, presents a promising solution for balancing supply and demand in renewable energy systems. However, challenges such as preferential flow through large pores and gravity segregation reduce storage efficiency. This study investigates the multiscale mechanisms by which foam injection enhances hydrogen storage efficiency across pore to reservoir scales. Through a combination of microfluidic visualization, molecular dynamics simulations, core flooding experiments, and reservoir-scale modeling, we demonstrate how surfactant-stabilized foam improves hydrogen conformance and displacement efficiency. Microfluidic experiments reveal that surfactant adsorption stabilizes hydrogen bubbles, while molecular dynamics simulations show reduced hydrogen mobility and enhanced water displacement due to surfactant interactions. Core flooding tests confirm increased hydrogen saturation and reduced preferential flow, while reservoir modeling predicts substantial improvement in storage capacity with foam injection compared to pure hydrogen injection under the simulated conditions. These findings offer insights into optimizing foam-based hydrogen storage strategies for large-scale renewable energy systems, advancing hydrogen's role as a key clean energy carrier, though field implementation would require site-specific assessment and optimization.