Perforation design coupled with heterogeneity during underground hydrogen storage in steeply dipping anticline aquifers

Hydrogen has been recognized as a crucial energy carrier to reduce greenhouse gas emissions. However, as it is not always possible to meet current energy demands, underground hydrogen storage (UHS) is required for energy supply and consumption. UHS is an emerging field of study with limited investigations regarding structural conditions and wellbore perforation design in steeply dipping anticline aquifers. This study investigates different perforation schemes with respect to UHS within steeply dipping anticline aquifers to find the most suitable injection/production design while examining small-scale reservoir heterogeneities. Several UHS improvement techniques are evaluated, including water and CO₂ injection through flank wells during hydrogen production. The results indicate that the highest hydrogen production is achieved with a fully perforated H₂ well located at the crest as it provides the maximum contact between the hydrogen and aquifer layers during H₂ injection/production. In contrast, hydrogen production is diminished with increased heterogeneity, as higher heterogeneities raise the chance of H₂ being trapped. To enhance UHS performance, first H₂ initialization before UHS beginning was evaluated but the results showed that it does not enhance UHS performance in a steeply dipped anticline aquifers, as effectively as it does in gas reservoirs. Water injection from flank wells during H₂ production cycles showed improvement in hydrogen withdrawal, while water production experienced a slight increase. CO₂ injection from flank wells was evaluated to effectively increase H₂ recovery as a cushion gas and to maintain hydrogen purity during production. According to results, hydrogen purity was not affected only in high heterogeneity, since more hydrogen gets trapped in the small-scale high heterogeneity level, which prevents the mixing zone from reaching the H₂ well during production. While the method prevents hydrogen contamination in anticline aquifers due to the high dip angle coupled with high heterogeneity levels, it leads to a lower hydrogen recovery.