Multiscale Model for Hydrogen Transport and Storage in Shale Reservoirs

Summary Utilizing underground geological structures for hydrogen storage is an effective approach for energy transformation. The depleted shale reservoirs can be considered as promising options for large-scale hydrogen storage because of the vast storage capacity, high containment security, and low operation cost. However, it is challenging to characterize the hydrogen transportation mechanism and estimate hydrogen storage potential in shale formations from multiscale perspectives. In this paper, we propose a multiscale model for hydrogen transport and storage in partially depleted hydraulically fractured shale reservoirs, considering the effects of gas diffusion, adsorption, slip flow, and continuous flow. By the Laplace transformation and Pedrosa substitution, a computationally effective semi-analytical solution was derived and validated with a commercial numerical simulator. A hydrogen storage capacity (HSC) assessment workflow is proposed using a typical shale reservoir in the Appalachian Basin as a case study. The results indicate that the storage capacity can reach up to 31.92×108 m3 at a high constrained injection pressure. In addition, the HSC is strongly controlled by the adsorption property, diffusion coefficient, shale composition, flow capacity between different scale media, and mobility ratio. The influence of most reservoir parameters on storage potential is negligible at low constrained pressure but critical at high constrained pressure. Such a model can be used as a robust pressure predictor and storage capacity estimator for hydrogen storage projects in partially depleted shale reservoirs.