Speaker
Description
Underground H2 storage in saline aquifers is critical for advancing the global energy transition through large-scale H2 utilization. However, cyclic stress-induced nano-cracks in caprocks may lead to leakage due to H2’s small size and high diffusivity. This study employed molecular dynamics simulations exploring the occurrence states of H2 and H2O near kaolinite surfaces, particularly focusing on H2 leakage when a nano-crack formed. We examined the effects of basal surfaces (gibbsite and siloxane), water content, and cushion gases (CH4 and CO2). In gibbsite aquifers, H2O formed adsorption layers; while in siloxane aquifers, it appeared as droplets or bridges. Upon nano-crack formation, initial H2 leakage occurred but halted once a critical number of H2O blocked the crack. H2 leakage was generally higher in siloxane than in gibbsite aquifers, except at low water content. Increased water content significantly reduced H2 leakage in gibbsite aquifers by rapidly achieving the critical H2O number, whereas the effect in siloxane aquifers depended on H2O distribution. Cushion gases effectively mitigated H2 leakage. CO2 outperformed CH4 in gibbsite aquifers, while their effects in siloxane aquifers varied based on H2O distribution. CH4 reduced leakage by hindering initial H2 entry into the crack, while CO2 not only impeded initial H2 entry but also assisted H2O in blocking the crack. Our analysis of density distributions, leakage dynamics, molecular configurations, and excess chemical potentials provides insights into H2 leakage and blockage mechanisms in aqueous environments near caprock minerals, facilitating the evaluation of H2 storage feasibility in saline aquifers.
| Country | China |
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