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Microfluidic Investigation of Hydrogen-Water Flow at Pore-Scale for Subsurface Hydrogen Storage

Bahrami, Mehdi | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56164 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Mahani, Hassan; Ayatollahi, Shahaboddin; Zivar, Davood
  7. Abstract:
  8. Hydrogen storage in porous subsurface formations, such as aquifers or depleted hydrocarbon reservoirs because of their high storage capacity, has gained momentum as a promising approach to balance the renewable energy supply and demand. However, the poor understanding of hydrogen flow dynamics in porous media is the main obstacle to the development and widespread application of underground hydrogen storage (UHS). For example, the main uncertainty is lack of detailed understanding of hydrogen flow dynamics in the natural porous media which leads to the unknown volume of recoverable hydrogen for this cyclic process. In this research, by developing a visual microfluidic apparatus to handle gas-water flow, the pore-scale displacement mechanisms during drainage and imbibition processes for hydrogen-water systems were studied. Besides, similar type of experiments were performed on the carbon dioxide-water system in this microfluidic system for the sake of comparison. Image processing techniques using high resolution microscopic images of the fluids flow at the pore-scale were used to investigate the flow behavior of the two-phase system, the gas displacement mechanisms, in-situ wettability distribution, capillary trapping, topology and connectivity of the gas phase through evaluation of Euler characteristic during the imbibition process. The results show that by reducing the rate of hydrogen injection, the extent of gas fingering during the drainage process decreases and the final saturation of hydrogen in the micromodel increases. Besides, the amount of trapped hydrogen and carbon dioxide saturation at the end of the imbibition process increased as the number of cycles increased. Quantitative assessment of the trapped gas showed that almost 15% of the carbon dioxide is trapped while for hydrogen it was 40%. The dissolution of carbon dioxide gas in the flowing water phase in the porous medium is one of the main reasons behind its lower residual saturation during the imbibition process. In addition, the observation of the fluid flow at the pore-scale showed that, at the start of the imbibition process, after injecting a small pore volume, the water penetrates the hydrogen phase causing gas trapping through the snap-off phenomenon. This turns the gas phase (hydrogen) from a continuous phase (with a negative Euler number) to into a non-continuous phase (with a positive Euler number). A significant amount of gas is also bypassed by water, which causes high capillary trapping of hydrogen. The hydrogen displacement mechanism is mainly achieved by the piston-like throat filling and I1 cooperative pore filling. Also, the average in-situ contact angle for the hydrogen-water-glass system is measured to be 30°, which indicates a strongly water-wet state in this system; explaining the two-phase flow results presented here. The findings of this research increase our understanding of the complexities of the underground hydrogen storage process in natural formations. In addition, by revealing the details of the flow behavior of water and hydrogen fluids at the pore-scale, it can provide important input parameters for modeling and simulation of the flow behavior of hydrogen in porous media at the pore-scales
  9. Keywords:
  10. Renewable Energy Resources ; Microfluidic System ; Wettability ; Hysteresis Behavior ; Euler Characteristics ; Underground Hydrogen Storage ; Porous Media

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