Integrated modeling and economic assessment of hydrogen storage with wellbore-reservoir-thermo-hydro-mechanical-diffusion coupling

Storage hydrogen in depleted gas reservoirs can effectively utilize existing underground space and safely and stably store hydrogen while saving investment costs. Therefore, a fully coupled wellbore-reservoir-thermo-hydro-mechanical-diffusion (WR-THMD) model for hydrogen geological storage (HGS) in depleted gas reservoirs was established in this paper. Based on this model, we analyzed the flow and heat transfer dynamics of hydrogen in the wellbore and reservoir, as well as the influence of changes in the physical properties of hydrogen. Finally, we discussed the impact of engineering parameters on the performance and economy of HGS system. The main conclusions are as follows: The low-temperature zone generated by low-temperature hydrogen injection helps to increase the storage capacity of hydrogen, and the molar concentration of hydrogen in this zone is 1.1 times higher than that in other areas. The high diffusion coefficient of hydrogen leads to a transition zone width of more than 50 m between hydrogen and methane in the reservoir, which is not conducive to the recovery of hydrogen. The low density of hydrogen is conducive to long-term HGS. However, it also increases the possibility of fingering effect. A relatively low injection mass flow rate should be used to enhance the injection capacity of hydrogen and reduce its diffusion into the caprock and bedrock, thereby improving the hydrogen storage efficiency. By reusing existing infrastructure, the initial investment and operational costs are significantly reduced by 2.24 × 107 dollars. This study provides important theoretical support and engineering guidance for HGS technology, and further promotes the practical application of hydrogen geological storage.