Experiments showed no reactions coupled to methane leaked into shallow aquifers

The need for subsurface energy stor¬age to balance the fluctuations in power production using renewable sources already exists, and based on the current deployment rate of wind and solar power stations, scenarios with a renewable share of up to 80% of the German energy production were developed for the next decades (UBA, 2010). Owing to the fluctuat¬ing character of renewable energy production, storage of gases, including compressed air, methane, and hydro¬gen may play a deciding role in the geological energy storage mix (Bauer et al., 2013). In case of a methane storage concept, the gas is generated from surplus renewable electricity via the Sabatier process, stored under¬ground in deep porous reservoirs or salt caverns, and retrieved and used in the existing energy system when needed. Any geological gas storage may result in leakages of the stored gas into shallow geological compart¬ments due to various reasons such as well failure (Evans, 2009). Evaluating hydrogeochemical reactions following such a potential accidental methane leakage into shallow aquifers are of particular importance for ensuring good groundwater quality, especially if the overlying shallow aquifers are used for drinking water production.