Impact of Wettability and Relative Permeability Hysteresis in Saline Aquifers; Implication of Hydrogen Underground Storage

Abstract

Abstract Numerical simulation is a crucial step in evaluating hydrogen storage in porous media and plays a crucial role in complementing and extending the insights gained from traditional laboratory experiments. This study focuses on numerically evaluating the influence of wettability and relative permeability hysteresis on hydrogen recovery in underground hydrogen storage. Wettability and hysteresis play pivotal roles in determining trapped gas saturation and significantly affect hydrogen recovery. Neglecting hysteresis may lead to overestimating gas production and misrepresenting water production. The investigation employs the Carlson model to calculate trapped gas saturation and the Killough model to account for the water hysteresis. By utilizing the Land coefficient based on laboratory-measured data for the hydrogen-brine system, our results reveal a substantial impact of gas hysteresis on the hydrogen recovery factor. The base model, neglecting the hysteresis effect, indicates a recovery factor of 78% by the fourth cycle. In contrast, the modified model, accounting for hysteresis and yielding a trapped gas saturation of ~17%, shows a hydrogen recovery factor of 45% by the fourth cycle. Furthermore, gas hysteresis notably impacts water production, with an observed 12.5% increase in volume in the model incorporating gas hysteresis. Additionally, results suggest that water hysteresis is significant in UHS, and a substantial reduction of hydrogen recovery and water production was observed. In conclusion, relative permeability hysteresis significantly influences hydrogen production compared to other petrophysical phenomena, such as wettability, which has a limited impact on operational feasibility and poses little threat to storing hydrogen in sandstone formations. In contrast to numerous numerical simulation studies that neglect hysteresis, this research offers a comprehensive analysis underscoring the significance of hysteresis on UHS. This contribution enhances the precision of recovery factor data estimation, which is crucial for assessing storage project feasibility.