Micromechanical modeling of the effect of dissociation on the mechanical response of hydrate-bearing sediments

Geomechanical aspects of methane hydrate (MH) bearing sediments constitute a major factor in MH reservoirs exploitation. One important element to be analyzed and quantified is the hydrate dissociation effect on the soil response, which may be critical for understanding the overall sediment response to gas hydrate production. This paper investigates the effect of MH dissociation on stresses and strains using the discrete element method (DEM). Both thermal-induced and depressurization-induced dissociation are considered in the paper. The sediment response is investigated under stress control and strain control loading conditions (one leading to excessive deformation while the other to stress relaxation), with examination of the resulting strain path and stress path, respectively. The effect of the stage in which the hydrate is formed and stressed is also investigated. Based on the DEM investigation, a simplified model entailing an interpolation between two states of the sediment (with and without hydrate) is suggested for potential use in continuum based formulations.