Influence of added hydrogen on underground gas storage: a review of key issues

The existing infrastructure of the natural gas transportation pipeline network and underground gas storage (UGS) facilities in Germany provides an opportunity and huge capacity to feed, transport and store hydrogen and synthetic fuel gases containing hydrogen, produced from renewable sources. At low hydrogen concentrations, only minor changes to gas transportation equipment will be required. In contrast, the UGS designed in converted gas fields and aquifers are particularly susceptible to the effect of hydrogen. Due to a lack of adequate knowledge about the hydrogen concentration in natural gas, which can be tolerated by the downhole equipment, reservoir and caprocks, the injection of natural gas containing hydrogen in the existing porous UGS is strongly limited. Key issues addressed in this paper are the change in capacity and efficiency of UGS associated with the blending of hydrogen in the stored natural gas, the geological integrity of the reservoir and caprocks, the technical integrity of gas storage wells, durability of the materials used for well completions, corrosion and environmental risks associated with the products of microbial metabolism.