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CFD Simulation of the Effect of Rock Characteristics on Hydrogen-Water Flow in Underground Hydrogen Storage

Nazari, Mansour | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58006 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Mahani, Hassan; Ayatollahi, Shahaboddin
  7. Abstract:
  8. With the increasing demand for clean energy and the need to reduce greenhouse gas emissions, underground hydrogen storage has emerged as an effective strategy for managing energy demand and optimizing the use of renewable resources. Given the importance of the wettability of the hydrogen-water-rock system and its spatial distribution within pores on the performance of hydrogen storage and production from aquifers, and the lack of studies in this field, this fundamental research aims to investigate the effect of rock properties, including wettability distribution and microporosity, on hydrogen and water flow behavior at the pore scale Pore-scale simulations were conducted using computational fluid dynamics (CFD) and the OpenFOAM software, directly solving the Navier-Stokes equations within the actual geometry of porous media. Results indicated that in strongly water-wet systems (contact angle less than 45°), medium flow rates (corresponding to a capillary number of 4.5×10-7 during drainage and 5.3×10-5 during imbibition) performed better. Conversely, in weakly water-wet systems (contact angle greater than 45°), increasing the flow rate improved the recovery factor. In mixed-wet systems with random distribution, the recovery factor significantly decreased under all conditions compared to uniform systems with the same average contact angle, highlighting the negative impact of wettability heterogeneity on hydrogen displacement and trapping. Systems with correlated wettability distributions, which are closer to natural porous rocks, demonstrated higher hydrogen trapping during imbibition. In these systems, hydrogen trapping was nearly ten times greater than in systems with uniform wettability distributions. In a correlated wettability system, the displacement mechanism during the drainage was primarily driven by invasion percolation, while two distinct imbibition mechanisms, referred to as I1 and I2 imbibition, dominated during the imbibition. Additionally, the presence of microporosity in the porous media revealed that many seemingly dead-end pathways are not truly closed. In systems without microporosity, these pathways act as barriers to hydrogen flow and water displacement. However, in systems with microporosity, the unique structure of these systems creates bottlenecks that enable hydrogen to penetrate the closed pathways, allowing the water in these regions to be displaced through the microporous network. Overall, the impact of injection and production rates on the recovery factor in microporous systems exhibited a similar trend to systems without microporosity, however the hydrogen distribution, particularly during the imbibition, was distinct between the two systems. The approach presented in this study, leveraging fundamental equations of fluid motion at the pore-scale and considering hydrogen's properties, can be applied to analyze flow behavior in depleted oil and gas reservoirs, predict their stability, and assess their reusability for underground hydrogen storage
  9. Keywords:
  10. Pore Scale Simulation of Fluid Flow ; Underground Hydrogen Storage ; Computational Fluid Dynamics (CFD) ; Microporosity ; Mixed Wettability ; Wettability Distribution

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