Deformation Characteristics of Hydrate-Bearing Sediments.

The safe and efficient development of natural gas hydrate requires a deep understanding of the deformation behaviors of reservoirs. In this study, a series of triaxial shearing tests are carried out to investigate the deformation properties of hydrate-bearing sediments. Variations of volumetric and lateral strains versus hydrate saturation are analyzed comprehensively. Results indicate that the sediments with high hydrate saturation show dilative behaviors, which lead to strain-softening characteristics during shearing. The volumetric strain curves have a tendency to transform gradually from dilatation to compression with the increase in effective confining pressure. An easy prediction model is proposed to describe the relationship between volumetric and axial strains. The model coefficient β is the key dominating factor for the shape of volumetric strain curves and can be determined by the hydrate saturation and stress state. Moreover, a modified model is established for the calculation of lateral strain. The corresponding determination method is provided for the easy estimation of model coefficients for medium sand sediments containing hydrate. This study provides a theoretical and experimental reference for deformation estimation in natural gas hydrate development. [ABSTRACT FROM AUTHOR]