Gas Hydrates in Permafrost: Distinctive Effect of Gas Hydrates and Ice on the Geomechanical Properties of Simulated Hydrate‐Bearing Permafrost Sediments

• Published in: Journal of geophysical research. Solid earth 2019-03, Vol.124 (3), p.2551-2563
• Main Authors: Yang, J., Hassanpouryouzband, A., Tohidi, B., Chuvilin, E., Bukhanov, B., Istomin, V., Cheremisin, A.
• Format: Article
• Language: English
• Subjects: Bearing; Climate change; Compression; Computer simulation; Confining; Deformation; Drilling; Exploratory drilling; Frame structures; Freezing; gas hydrate; Gas hydrates; geomechanical properties; Geomechanics; Geophysics; Global warming; Hydrates; Ice; Internal friction; Methane; Methane hydrates; microhydrate networks; Natural gas exploration; Oil and gas exploration; Oil exploration; Permafrost; Properties; Properties (attributes); Saturation; Sediment; Sediments; Shear strength; Shearing; Stability; Stretching; Triaxial compression tests; triaxial shearing
• ISSN: 2169-9313; 2169-9356
• DOI: 10.1029/2018JB016536

The geomechanical stability of the permafrost formations containing gas hydrates in the Arctic is extremely vulnerable to global warming and the drilling of wells for oil and gas exploration purposes. In this work the effect of gas hydrate and ice on the geomechanical properties of sediments was compared by triaxial compression tests for typical sediment conditions: unfrozen hydrate‐free sediments at 0.3 °C, hydrate‐free sediments frozen at −10 °C, unfrozen sediments containing about 22 vol% methane hydrate at 0.3 °C, and hydrate‐bearing sediments frozen at −10 °C. The effect of hydrate saturation on the geomechanical properties of simulated permafrost sediments was also investigated at predefined temperatures and confining pressures. Results show that ice and gas hydrates distinctively influence the shearing characteristics and deformation behavior. The presence of around 22 vol% methane hydrate in the unfrozen sediments led to a shear strength as strong as those of the frozen hydrate‐free specimens with 85 vol% of ice in the pores. The frozen hydrate‐free sediments experienced brittle‐like failure, while the hydrate‐bearing sediments showed large dilatation without rapid failure. Hydrate formation in the sediments resulted in a measurable reduction in the internal friction, while freezing did not. In contrast to ice, gas hydrate plays a dominant role in reinforcement of the simulated permafrost sediments. Finally, a new physical model was developed, based on formation of hydrate networks or frame structures to interpret the observed strengthening in the shear strength and the ductile deformation. Key Points Geomechanical properties of unfrozen and frozen, hydrate‐free, and hydrate‐bearing sediments were experimentally determined Ice and hydrate distinctively affected the shearing characteristics and deformation behavior of sediments A physical model of microhydrate networks or frame structures was presumed to interpret the distinctive characteristics