Pore-scale investigation of two-phase flow hysteresis in hydrogen storage using micro-ct imaging
File(s)
Author(s)
Goodarzi, Sepideh
Type
Thesis
Abstract
With increasing interest in hydrogen as a clean energy carrier, understanding its behaviour in subsurface porous media is essential for optimising geological storage systems. This PhD thesis investigates the pore-scale dynamics of hydrogen-brine systems, focusing on hysteresis, capillary pressure, and the role of Ostwald ripening in gas retention and connectivity. Traditional models-largely based on hydrocarbon systems-tend to overlook gas redistribution mechanisms like Ostwald ripening. This research addresses that gap by employing high-resolution X-ray tomography combined with the computation of Minkowski functionals to examine hydrogen behaviour in Bentheimer sandstone, offering new insights into gas-phase connectivity and trapping. The work comprises three experimental investigations. The first study examined hydrogen and brine distribution during repeated injection and waterflooding cycles, with a 16-hour storage period. Results showed preferential hydrogen accumulation in larger pores and demonstrated that Ostwald ripening enhanced gas connectivity even in the absence of external flow. The second experiment focused on capillary pressure and saturation changes across three injection–flooding cycles. Residual gas saturation decreased from 40% in the first cycle to less than 18% by the third, suggesting reduced hysteresis relative to conventional expectations and reinforcing the significance of Ostwald ripening in mobilising trapped gas. The final study extended the storage period to four days to observe longer-term effects on hydrogen distribution and connectivity. Using both hydrophilic and hydrophobic porous plates, contact angle measurements confirmed the water-wet nature of Bentheimer sandstone. Observations revealed a decrease in gas saturation from 85% after initial hydrogen injection to 22% after the third brine injection. These findings further highlight that hydrogen storage hysteresis is less pronounced than predicted by classical models. By advancing the understanding of pore-scale fluid topology and gas connectivity, this thesis contributes important insights toward the design and optimisation of subsurface hydrogen storage systems, supporting the transition to cleaner energy solutions.
Version
Open Access
Date Issued
2025-05-28
Date Awarded
01/08/2025
License URL
Advisor
Blunt, Martin J
Bijeljic, Branko
Sponsor
Shell International Ltd (Firm)
Imperial College London
Diamond Light Source (Firm)
Grant Number
EP/V038044/1
Publisher Department
Department of Earth Science & Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)