Hydrogen storage-production in aquifers: Multiple-mechanism-coupled numerical modeling and sensitivity analysis

Global climate change demands efficient energy storage solutions for transitioning to cleaner, low-carbon systems. Underground hydrogen storage (UHS) offers large capacity, extended duration, and enhanced safety, making it suitable for large-scale use. However, optimizing storage in aquifers and addressing economic challenges require specific engineering methods. This paper develops an unsteady seepage model for hydrogen storage in aquifers and predicts storage-production performance of a homogeneous aquifer model using numerical simulation. Results show hydrogen remains gaseous in homogeneous aquifers, with minor impacts from individual storage mechanisms on yield and quality. Hysteresis effects enhance gas retention and purity, reducing production but increasing bottomhole pressure. Solubility and aqueous phase property variations minimally impact yield and quality. Sensitivity analysis shows reservoir pressure impacts 64.7 %, other factors contributing less than 35 %. An injection-production ratio close to 1 with high injection rate generates the highest total hydrogen recovery and storage, while a high injection-production ratio, e.g. 4, generates a highest-hydrogen-concentration outflux. Since higher reservoir pressure would boost total hydrogen stored and produced efficiently and evidently, it is advised that injection pressure is maintained higher while the production rate could be close to injection rate, which would ensure the best recovery without producing excessive liquid.