Creep and Wave Velocity Characterization on Anisotropic Consolidated Methane Hydrate Sediments of the South China Sea

Offshore engineering geological activities can lead to creep behavior in hydrate reservoirs, which, in turn, leads to reservoir subsidence, seriously affecting the safety of offshore facilities as well as the long-term stability of the reservoir. Accurate characterization of the creep properties of hydrate sediment is the key to predicting the long-term stability of hydrate reservoirs. Therefore, a series of creep experiments were carried out in the triaxial pressure chamber, and the creep deformation mechanism was proposed based on the acoustic wave data and predicted the long-term strength of the reservoirs. The results show that the hydrate sediments have typical stable creep characteristics; the creep strain and the volumetric strain of the sediments are positively correlated with the stress level and effective confining pressure. The long-term stability of the reservoir is generally low and therefore requires careful consideration. Finally, two different creep constitutive models are compared, and the Singh–Mitchell empirical creep model applicable to the creep relationship of hydrate sediments in the South China Sea is established based on the experimental data.