Mechanical Properties of Gas Hydrate-Bearing Sediments Influenced by Multiple Factors: A Comprehensive Review of Triaxial Tests

Natural gas hydrate (NGH) has the characteristics of low pollution and large reserves, which is considered as a very promising energy source. The extraction of NGH would cause the strength and stiffness reduced in hydrate-bearing sediment (HBS) reservoirs, which could lead to geological disasters. The mechanical properties of HBS have been studied by a large number of scholars, but it has not been sorted out and summarized for HBS under the influence of multiple factors. In this paper, the hydrate types, synthesis methods, and test conditions are summarized. The effects of hydrate saturation, loading rate, temperature, pore pressure, confining pressure, fine content, and clay content on mechanical properties and deformation behavior of HBS are outlined. The microstructure of the synthesis, decomposition, and shear processes of HBS specimens is also analyzed based on the CT triaxial shear test system, and the microscopic mechanism of HBS specimens in the shearing process is summarized. Finally, the shortcomings of current research on the mechanical properties of HBS are discussed, and provided corresponding suggestions to promote the development of the mechanical properties of HBS.