Deformation characteristics on anisotropic consolidated methane hydrate clayey-silty sediments of the South China Sea under heat injection

Abstract

Natural gas hydrate is a new energy source with huge reserves, and the carbon content of hydrates is twice the carbon content of all proven fossil fuels combined, but the natural gas hydrate exploitation involves solid-liquid-gas phases change, which could induce a potential geological and environmental risk. Accurate description of the deformation behavior of sediments during hydrate dissociation is the key to predict the long-term stability of hydrate reservoirs. Nowadays, related studies mainly focus on the deformation behavior of hydrate-bearing sediment without dissociation. In this study, the deformation behaviors of remolded cores during thermal dissociation under anisotropy stress states were studied. The results show that 1) hydrate dissociation can lead to sediment deformation, the deformation rate of the sediments during the process of hydrate dissociation is 3 orders of magnitude larger than that before the dissociation. 2) the sediments under larger effective confining pressure (burial depth) present less deformation. 3) the sediments under isotropic stress conditions exhibit smaller deformation than that under anisotropic stress conditions. 4) dynamic permeability evolution during hydrate dissociation process can lead to effective confining pressure changes of the sediment, which can exacerbate the deformation.