Strength Behaviors of Remolded Hydrate-Bearing Marine Sediments in Different Drilling Depths of the South China Sea

Yanghui Li,Yongchen Song,Weiguo Liu,Xiang Sun,Yuanping Li,Qingping Li,Tingting Luo

doi:10.3390/en12020253

Abstract

The mechanical behaviors of hydrate-bearing marine sediments (HBMS) drilled from the seafloor need to be understood in order to safely exploit natural gas from marine hydrate reservoirs. In this study, hydrates were prepared using ice powder and CH4 gas, and HBMS from the Shenhu area in the South China Sea were remolded using a mixed sample preparation method. A series of triaxial tests were conducted on the remolded HBMS to investigate the effects of soil particle gradation and the existence of hydrate on the mechanical properties of hydrate reservoirs. The results show that the stiffness and failure strength of HBMS decrease along with the decrease of mean particle size and soil aggregate morphology change at different drilling depths, and the reduction of failure strength is more than 20% when the drilling depth drops by 30 m. A better particle gradation of marine sediments may boost the stiffness and failure strength of HBMS. In addition, the existence of hydrate plays an important role in the strength behaviors of HBMS. The reduction of failure strength of HBMS with 30% initial hydrate saturation is more than 35% after complete hydrate dissociation.

Highlights

Methane gas hydrate, an ice-like compound, has attracted the attention of global scientists for its huge exploitation potential [1,2,3,4,5]
A comparison between the mechanical properties of hydrate-bearing marine sediments (HBMS) formed by S-1, S-2, S-3 and S-4 marine sediments in Figure 6 clearly shows that the elastic modulus and failure strength of HBMS S-3 and
A series of triaxial tests was conducted to investigate the effects of soil particle gradation and hydrate existence on the mechanical properties of remolded HBMS

Summary

Introduction

An ice-like compound, has attracted the attention of global scientists for its huge exploitation potential [1,2,3,4,5]. Many marine explorations have confirmed that large amounts of natural gas hydrate resources exist in the Shenhu area in the. South China Sea [10,11,12] This area may become an objective target for hydrate exploitation in the future. Hydrate dissociation in the natural gas exploitation process may lead to submarine landslides and tsunamis, and further give rise to unexpected engineering facility damage [13,14,15,16,17,18]. The mechanical behaviors of HBMS need to be investigated systematically before that the large-scale exploitation from gas hydrate reservoirs is undertaken

Methods

Results

Conclusion