| Summary: | Methane hydrate has been considered as a future energy resource due to the vast amount of carbon in the natural hydrate reservoirs. During gas production from deep-sea hydrate deposits via depressurization, the effective stress of hydrate-bearing sediments can increase and alter the mechanical, physical, and hydraulic properties of the sediments. This thesis explores the geomechanical and hydraulic properties of tetrahydrofuran hydrate-bearing sand specimens subjected to high effective stress. Specifically, the focus is placed on understanding the role of hydrate crystals on the compressibility, particle grain crushing, wave velocity, the coefficient of earth pressure at rest, and permeability anisotropy in hydrate-bearing sediments. This thesis also explores hydrate morphology in clayey sediments and ensued geophysical properties using X-ray computed tomography and elastic wave measurements. The major findings of this thesis include: (i) the presence of hydrate crystals restrains particle rotation and rearrangement during loading, resulting in less pronounced particle crushing in sediments with higher hydrate saturation; (ii) the coefficient of earth pressure at rest K0 is mainly affected by hydrate saturation and applied vertical stress levels, and the cementation effect and the creep behavior of hydrate crystals play a vital roles in the evolution of K0; (iii) the permeability anisotropy of hydrate-bearing sediments increases exponentially with the increase of effective vertical stress under the oedometer condition, implying that vertical direction permeameter tests may underestimate the reservoir’s flow performance; and (iv) the morphology and hydrate saturation of tetrahydrofuran hydrate in clayey sediments are affected by the nucleation induction time, and the sediments with higher hydrate saturation attenuate P- and S-waves more significantly. These findings are expected to provide a comprehensive understanding of the geotechnical and the hydraulic behavior of hydrate-bearing specimens under high effective stress conditions and wave-based characterization of hydrate-bearing clayey specimens. Ph.D.
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