Cyclic Deformation in Underground Hydrogen Storage: A Global Sensitivity Study

We conduct a global sensitivity analysis for cyclic underground hydrogen storage in depleted gas reservoirs to quantify how flow and mechanical parameters control key responses in each cycle. Using a principal component regression (PCR) workflow, we rank drivers of reservoir and overburden vertical/radial displacements, recovery, and plume radius, and assess imbalances arising from asymmetric cycles. Simulated deformation signals are within detectability limit of remote sensing and feasibility of field-scale monitoring. Across all scenarios, reservoir stiffness is the dominant control: for both vertical and radial deformation, highlighting geomechanics as a first-order driver. Vertical response shows larger uplift than subsidence (median uplift 1.5 mm versus median subsidence -0.9 mm). Radial deformation affects a broad footprint, with deformation radius spanning 12 km to 14.7 km. Sensitivity results reveal a separation of controls: the radial deformation ratio is primarily governed by mechanical properties, whereas the vertical deformation ratio is more sensitive to operational conditions such as pressure evolution and hydrogen fraction. The deformation front propagates 10 times faster than the concentration front, suggesting geomechanical monitoring can provide earlier indication of system performance compared to compositional metrics. Peak recovery per cycle reaches 0.8, while cases with net uplift at the end of production tend to show reduced recovery