Numerical study on mechanical properties and instability characteristics of sandy reservoir containing hydrate interlayer

Abstract

A sound understanding of the geomechanical behavior of sandy reservoir containing hydrate interlayer is crucial not only for safe exploitation of natural gas but also for assessing the continental slope stability. To date, there are extremely limited reports on synergistic consideration of hydrate interlayer together with overburden and underburden. In order to study the mechanical properties and instability characteristics of sandy reservoir containing hydrate interlayer, in this study, sandy reservoir specimens were prepared using the discrete element method firstly. Subsequently, triaxial undrained tests were carried out under different thicknesses and saturation of hydrate interlayer. Results show that formation of hydrate can enhance the strength of the sediments, but not necessarily the reservoir. Conversely, lower intercalation saturation and thickness can reduce reservoir strength. The critical saturation and thickness that significantly alter the geomechanical properties of reservoirs are further discussed. Additionally, there is a dissipation of energy respectively before and after the peak stress, which may be a unique feature of the reservoir. By analyzing the crack propagation and evolution of the shear band during shear, the damage and failure process of specimen is clarified. And a prediction method for the mechanical response of sandy reservoir containing hydrate interlayer was suggested.