Speaker
Description
Hydrogen has emerged as a promising alternative for sustainable energy and plays a pivotal role in the transition from fossil fuels to green energy. With this growing reliance on hydrogen, the demand for efficient and scalable energy storage solutions has become increasingly critical. Among the various methods available, underground hydrogen storage (UHS) stands out as a cost-effective solution for long-term, large-scale energy storage. UHS involves injecting hydrogen into geological subsurface formations, including depleted hydrocarbon reservoirs, salt caverns, and saline aquifers. However, a major challenge in UHS arises from the activity of subsurface microorganisms, such as methanogens, sulfate-reducing bacteria (SRB), and acetogens. These microorganisms use hydrogen as an electron donor, producing impurities such as methane (CH₄) through methanogenesis, hydrogen sulfide (H2S) through reduction of sulfate, and acetic acid (CH₃COOH) during acetogenesis. Microbial activities within porous media thus profoundly affect the hydrodynamics of the system and induce alterations in its physical properties, which can impact storage efficiency and hydrogen recovery. Despite experimental efforts to study these effects at the pore-scale, the results remain inconsistent, and simulations, on a larger scale, that account for microbially induced impurities are also very limited. Therefore, evaluating the biotic effects on the hydrodynamics of UHS is essential to understand the risks associated with the hydrogen loss and recovery rate in these systems.
This study addresses these knowledge gaps by conducting pore-scale analysis to investigate the hydrodynamics of UHS systems under realistic storage conditions, focusing on the behavior of rock-hydrogen-brine interactions during the cyclic injection, storage, and withdrawal phases in the presence of methanogens and SRBs. Our pore-scale analyses are employed to model the effects of microbial metabolisms on wettability, hydrogen diffusion, and relative hydrogen permeability. Microbial products are introduced during the storage stage and their impact is analyzed throughout the storage and withdrawal phases of UHS. The results demonstrate that the presence of microbial-mediated impurities causes the rock surface to slightly alter in terms of wettability, which can greatly influence fluid-rock interactions and dynamics. We also report that hydrogen diffusion decreases with increasing concentrations of microbial impurities. Furthermore, the shift in wettability and reduced hydrogen mobility, in turn, impact the relative permeability of hydrogen, highlighting the importance of microbially-induced changes on storage efficiency and recovery dynamics in UHS systems. Our findings provide critical insights into optimizing UHS designs to mitigate biotic impacts.
| Country | USA |
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