Deformation Characteristics on Anisotropic Consolidated Methane Hydrate Clayey-Silty Sediments of the South China Sea Under Heat Injection

Abstract

Natural gas hydrate is the commanding point of future energy development strategy, which is crucial to solving the world energy crisis and the transition to green and low-carbon energy. Therefore, it is urgent to fully clarify the formation deformation characteristics caused by hydrate dissociation before commercial exploitation. However, most of the current studies focus on the deformation behavior of hydrate reservoirs under the condition of isotropic consolidation, the actual hydrate reservoirs have different consolidation coefficients due to the difference of historical stress, but the relevant studies are still blank. In this paper, the clayey-silty was used as the substrate to reshape the hydrate sediment samples under in-situ temperature and pressure conditions in the hydrate reservoir of the South China Sea. The influences of consolidation coefficient, effective confining pressure and initial stress level on formation deformation were emphatically studied, and the following conclusions were reached: (1) The sediment samples with anisotropic consolidation have greater shear strength than those with isotropic consolidation. (2) Effective confining pressure can inhibit sediment deformation, but it will produce a larger volume change. (3) The dissociation of hydrate will lead to the deformation of the sediment, which is mainly caused by the failure of the cementation of hydrate and the loss of additional strength of the sediment skeleton. (4) Consolidation coefficient, effective confining pressure, initial stress level and permeability all have an impact on the formation deformation during hydrate dissociation.

Keywords: Hydrate dissociation, anisotropic consolidated, natural gas hydrate, deformation properties