Hydro-mechanical reservoir simulation of hydrogen storage in a saline aquifer in the North German Basin

The long-term energy storage potential of underground hydrogen storage (UHS) in geologic porous reservoirs is key to mitigating the intermittency of renewable energy supplies. Assessing its feasibility requires understanding hydraulic and mechanical behaviour, particularly in faulted reservoirs, which remains insufficiently studied under realistic conditions. This study presents a coupled hydro-mechanical simulation of cyclic hydrogen injection and withdrawal at the Ketzin site (Germany), a fault-bounded saline aquifer, incorporating heterogeneous facies and a complex fault network. Results show that fault stability is maintained throughout, with low slip tendency values. Fault geometry exerts a strong control on reactivation potential, in addition to pore pressure effects. Localised stress variations occur but remain below failure conditions. Reservoir uplift is limited to millimetre scale during injection, with negligible cumulative compaction. The results highlight the importance of accurate fault geometry characterisation and support the evaluation of safe UHS operations at Ketzin and similar fault-bounded saline aquifers. • Hydro-mechanical model of underground hydrogen storage in a saline aquifer. • Real-field simulation including heterogeneous facies and complex fault networks. • Fault slip tendency remains below critical limits under realistic storage cycles. • Fault geometry strongly controls fault stress distribution beyond pore pressure. • Cyclic injection causes only reversible millimetre-scale surface deformation.