Morphological and hydrodynamic properties of hydrates during dissociation in sediment

• Main Authors: Sun, Zhixue, Yin, Yifan, Wu, Yuqi, Sun, Zhilei, Zhu, Linqi, Zhan, Yuting, Niasar, Vahid, An, Senyou
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2023
• Subjects: Methane hydrate; Digital rock physics; Hydrate pattern classification; Hydrate evolution
• Online Access: https://research.manchester.ac.uk/en/publications/e07188e3-20cc-4f83-84af-5cb2820892d6

The formation and dissociation of hydrate at the pore scale can be observed qualitatively using μ-CT X-ray imaging. However, a quantitative criterion for hydrate pattern is not currently available in the literature. To fill this research gap, we generated numerically-simulated sediments with specific hydrate formation patterns and accurate hydrate saturation levels, by integrating X-ray computed tomography techniques, morphological operation algorithm, and quartet structure generation set method. Using the topological information extracted from the generated hydrate-bearing sediments, we proposed a quantitative criterion for the microscopic classification of hydrates. By calculating the topology pore complexity (Tp) and hydrate topology (Th),hydrates are classified into Pore-floating, cementing and bridging. In this study, we utilized μ-CT imaging technology to visualize the 3D distribution of hydrate, as well as analyzed the topology of hydrate and its dynamic evolution through our proposed classification method and the extracted dual network models. Our findings demonstrate that when the hydrate saturation exceeds 30%, the dominating hydrate patterns are bridging and pore-floating, while sediment is more likely to exhibit cementing and pore-floating patterns when the hydrate saturation is below this threshold. Additionally, we applied the lattice Boltzmann method to numerically analyze the variation of normalized permeability and tortuosity under different hydrate saturation levels. The permeability monotonically increases as hydrate dissociates from the sediments, while the behaviour of tortuosity is non-monotonic.