Investigation on the Impact of Cushion Gases in Saline Aquifer: Implication for Underground H2 Storage

The goal of this research is to investigate the use of different gases to serve as cushion gases to minimize H2 loss in underground H2 storage (UHS). A detailed study is performed using a compositional numerical reservoir simulator. We constructed a base model that uses H2 as the cushion gas. Next, we developed three different scenarios where CH4, N2, and CO2 are used as the cushion gas, and we analyzed the impact of each cushion gas on the overall performance of the UHS. We developed the fluid model to account for the density and viscosity of a mixture of gases. Our results indicated that CH4 emerges as the optimal choice, followed by N2, and subsequently CO2. However, maximizing the H2 recovery from 63% to 77% was at the cost of lowering H2 purity. Yet, using an alternative cushion gas played a vital role in minimizing the spreading of hydrogen, and consequently preventing the H2 loss into the formation.