Hydrogen storage in heterogeneous reservoirs: evaluating well configurations and cushion gas impact

Abstract

The urgency in mitigating the climate change effects and the expecting rise of energy consumption in the coming decades will require zero-carbon sources like renewables, fossil fuels with carbon capture and storage, and sustainable storage solutions like underground gas storage. Hydrogen geological storage in porous rock formations is expected to play a major role for sustainable energy systems, offering large-scale storage in subsurface reservoirs for grid stability and cost-effective integration of renewable hydrogen production. This work explores hydrogen geological storage in saline aquifers, focusing on reservoir simulation under varying structural and geological conditions. To address renewable energy fluctuations, hydrogen injection and withdrawal cycles were conducted in complex heterogeneous reservoirs. Key aspects include the evaluation of different well configurations, such as separate injection and withdrawal wells, dual-purpose wells, and a hybrid of both, and the role of cushion gas in enhancing reservoir efficiency. The work highlights that dual-purpose well configurations offer higher efficiency, making the use of cushion gas less critical. However, optimising cushion gas usage is essential due to its significant impact on operational costs. The study also emphasizes the importance of addressing reservoir heterogeneity, as it greatly influences the efficiency of hydrogen injection and withdrawal cycles.