Interfacial thermo-mechanical behavior of methane hydrate-bearing sediments: A steered molecular dynamics study

Evaluating and predicting the mechanical properties of hydrate-bearing sediments to safely develop hydrates has become an inevitable difficulty, but its microscopic mechanism was poorly understood, especially under extreme conditions. Based on the equations of state for methane, the steered molecular dynamics (SMD) simulation method has been employed to study the tensile and shear mechanical behavior of methane hydrate-bearing sediments (MHBS), considering the various temperatures (50 similar to 250 K) and methane hydrate saturation levels (75 similar to 95 %). The microstructure variation and deformation mechanism of the whole system under different phase equilibrium conditions were investigated. The simulation results showed that: (1) The tensile failure of the MHBS was brittle, and its shear failure was plastic, where the shear strength in the x and y directions was lower than the tensile strength. (2) Both tensile and shear failure occurred in the layer of hydrate structure near the hydrate-silica interface. (3) The tensile and shear strength decreased with rising temperature. The shear strength in the x direction was slightly higher than that in they direction at temperatures less than 150 K, but the opposite was true at temperatures over 150 K. (4) When the methane hydrate saturation was greater than 75 %, the influence of methane hydrate saturation on the tensile and shear strength was relatively little. This work provided guidance and a new research ideas for the exploitation of MHBS under extreme conditions.